Fedora desktop Planet

New Evince format support: Adobe Illustrator and CBR files

Posted by Bastien Nocera on July 26, 2017 01:42 PM
A quick update, as we've touched upon Evince recently.

I mentioned that we switched from using external tools for decompression to using libarchive. That's not the whole truth, as we switched to using libarchive for CBZ, CB7 and the infamous CBT, but used a copy/paste version of unarr to support RAR files, as libarchive support lacks some needed features.

We hope to eventually remove the internal copy of unarr, but, as a stop-gap, that allowed us to start supporting CBR comics out of the box, and it's always a good thing when you have one less non-free package to grab from somewhere to access your media.

The second new format is really two formats, from either side of the 2-digit-year divide: PostScript-based Adobe Illustrator and PDF-based Adobe Illustrator. Evince now declares to support "the format" if both of the backends are built and supported. It only took 12 years, and somebody stumbling upon the feature request while doing bug triaging. The nooks and crannies of free software where the easy feature requests get lost :)

Both features will appear in GNOME 3.26, the out-of-the-box CBR support is however available now in an update for the just released Fedora 26.

Summer recipes

Posted by Matthias Clasen on July 26, 2017 12:44 PM

I just did a release of GNOME recipes in time for GUADEC.

While this is a development release, I think it may be time to declare this version (1.6) stable. Therefore, I encourage you to try it out and let me know if something doesn’t work.

Here is a quick look at the highlights in this release.

Inline editing

Inline editing of ingredients has been completed. We provide completions for both units and ingredients.

Error handling

And if something goes wrong, we try to be helpful by pointing out the erroneous entry and explaining the required format.


The printed form of recipes has seen several small improvements. Fields like cuisine and season are now included, and the ingredients list is properly aligned in columns.


All lists of recipes can now be sorted by recency or by name.

If you happen to be in Manchester this weekend, you can learn more about GNOME recipes by coming to our talk.


Posted by Bastien Nocera on July 21, 2017 04:53 PM
@GodTributes took over my title, soz.

Dude, where's my maintainer?

Last year, probably as a distraction from doing anything else, or maybe because I was asked, I started reviewing bugs filed as a result of automated flaw discovery tools (from Coverity to UBSan via fuzzers) being run on gdk-pixbuf.

Apart from the security implications of a good number of those problems, there was also the annoyance of having a busted image file bring down your file manager, your desktop, or even an app that opened a file chooser either because it was broken, or because the image loader for that format didn't check for the sanity of memory allocations.

(I could have added links to Bugzilla entries for each one of the problems above, but that would just make it harder to read)

Two big things happened in gdk-pixbuf 2.36.1, which was used in GNOME 3.24:

  • the removal of GdkPixdata as a stand-alone image format loader. We really don't want to load GdkPixdata files from sources other than generated sources or embedded data structures, and removing that loader closed off those avenues. We still ended up fixing a fair number of naive assumptions in helper functions though.
  • the addition of a thumbnailer for gdk-pixbuf supported images. Images would not be special-cased any more in gnome-desktop's thumbnailing code, making the file manager, the file chooser and anything else navigating directories full of broken and huge images more reliable.
But that's just the start. gdk-pixbuf continues getting bug fixes, and we carry on checking for overflows, underflows and just flows, breaks and beats in general.

Programmatic Thumbellina portrait-maker

Picture, if you will, a website making you download garbage files from the Internet, the ROM dump of a NES cartridge that wasn't properly blown on and digital comic books that you definitely definitely paid for.

That's a nice summary of the security bugs foisted upon GNOME in past year or so, even if, thankfully, we were ahead of the curve in terms of fixing those issues (the GStreamer NSF decoder bug was removed in 2013, the comics backend in evince was rewritten over a period of 2 years and committed in March 2017).

Still, 2 pieces of code were running on pretty much every file downloaded, on purpose or not, from the Internet: Tracker's indexers and the file manager's thumbnailers.

Tracker started protecting itself not long after the NSF vulnerability, even if recent versions of GStreamer weren't vulnerable, as we mentioned.

That left the thumbnailers. Some of those are first party, like the gdk-pixbuf, and those offered by core applications (Evince, Videos), written by GNOME developers (yours truly for both epub/mobi and Nintendo DS).

They're all good quality code I'd vouch for (having written or maintained quite a few of them), but they can rely on third-party libraries (say GStreamer, poppler, or libarchive), have naive or insufficiently defensive code (gdk-pixbuf loaders,  GStreamer plugins) or, worst of all: THIRD-PARTY EXTENSIONS.

There are external plugins and extensions for image formats in gdk-pixbuf, for video and audio formats in GStreamer, and for thumbnailers pretty much anywhere. We can't control those, but the least we can do when they explode in a wet mess is make sure that the toilet door is closed.

Not even Nicholas Cage can handle this Alcatraz

For GNOME 3.26 (and today in git master), the thumbnailer stall will be doubly bolted by a Bubblewrap sandbox and a seccomp blacklist.

This closes a whole vector of attack for the GNOME Desktop, but doesn't mean we're completely out of the woods. We'll need to carry on maintaining and fixing security bugs in those libraries and tools we depend on, as GStreamer plugin bugs still affect Videos, gdk-pixbuf bugs still affect Photos and Eye Of Gnome, etc.

And there are limits to what those 2 changes can achieve. The sandboxing and syscall blacklisting avoids those thumbnailers writing anything but an image file in PNG format in a specific directory. There's no network, the filename of the original file is hidden and sanitised, but the thumbnailer could still create a crafted PNG file, and the sandbox doesn't work inside a sandbox! So no protection if the application running the thumbnailer is inside Flatpak.

In fine

GNOME 3.26 will have better security for thumbnailers, so you won't "need to delete GNOME Files".

But you'll probably want to be careful with desktops that forked our thumbnailing code, namely Cinnamon and MATE, which don't implement those security features.

The next step for the thumbnailers will be beefing up our protection against greedy thumbnailers (in terms of CPU and memory usage), and sharing the code better between thumbnailers.

Note for later, more images of cute animals.

Avoiding TPM PCR fragility using Secure Boot

Posted by Matthew Garrett on July 18, 2017 06:48 AM
In measured boot, each component of the boot process is "measured" (ie, hashed and that hash recorded) in a register in the Trusted Platform Module (TPM) build into the system. The TPM has several different registers (Platform Configuration Registers, or PCRs) which are typically used for different purposes - for instance, PCR0 contains measurements of various system firmware components, PCR2 contains any option ROMs, PCR4 contains information about the partition table and the bootloader. The allocation of these is defined by the PC Client working group of the Trusted Computing Group. However, once the boot loader takes over, we're outside the spec[1].

One important thing to note here is that the TPM doesn't actually have any ability to directly interfere with the boot process. If you try to boot modified code on a system, the TPM will contain different measurements but boot will still succeed. What the TPM can do is refuse to hand over secrets unless the measurements are correct. This allows for configurations where your disk encryption key can be stored in the TPM and then handed over automatically if the measurements are unaltered. If anybody interferes with your boot process then the measurements will be different, the TPM will refuse to hand over the key, your disk will remain encrypted and whoever's trying to compromise your machine will be sad.

The problem here is that a lot of things can affect the measurements. Upgrading your bootloader or kernel will do so. At that point if you reboot your disk fails to unlock and you become unhappy. To get around this your update system needs to notice that a new component is about to be installed, generate the new expected hashes and re-seal the secret to the TPM using the new hashes. If there are several different points in the update where this can happen, this can quite easily go wrong. And if it goes wrong, you're back to being unhappy.

Is there a way to improve this? Surprisingly, the answer is "yes" and the people to thank are Microsoft. Appendix A of a basically entirely unrelated spec defines a mechanism for storing the UEFI Secure Boot policy and used keys in PCR 7 of the TPM. The idea here is that you trust your OS vendor (since otherwise they could just backdoor your system anyway), so anything signed by your OS vendor is acceptable. If someone tries to boot something signed by a different vendor then PCR 7 will be different. If someone disables secure boot, PCR 7 will be different. If you upgrade your bootloader or kernel, PCR 7 will be the same. This simplifies things significantly.

I've put together a (not well-tested) patchset for Shim that adds support for including Shim's measurements in PCR 7. In conjunction with appropriate firmware, it should then be straightforward to seal secrets to PCR 7 and not worry about things breaking over system updates. This makes tying things like disk encryption keys to the TPM much more reasonable.

However, there's still one pretty major problem, which is that the initramfs (ie, the component responsible for setting up the disk encryption in the first place) isn't signed and isn't included in PCR 7[2]. An attacker can simply modify it to stash any TPM-backed secrets or mount the encrypted filesystem and then drop to a root prompt. This, uh, reduces the utility of the entire exercise.

The simplest solution to this that I've come up with depends on how Linux implements initramfs files. In its simplest form, an initramfs is just a cpio archive. In its slightly more complicated form, it's a compressed cpio archive. And in its peak form of evolution, it's a series of compressed cpio archives concatenated together. As the kernel reads each one in turn, it extracts it over the previous ones. That means that any files in the final archive will overwrite files of the same name in previous archives.

My proposal is to generate a small initramfs whose sole job is to get secrets from the TPM and stash them in the kernel keyring, and then measure an additional value into PCR 7 in order to ensure that the secrets can't be obtained again. Later disk encryption setup will then be able to set up dm-crypt using the secret already stored within the kernel. This small initramfs will be built into the signed kernel image, and the bootloader will be responsible for appending it to the end of any user-provided initramfs. This means that the TPM will only grant access to the secrets while trustworthy code is running - once the secret is in the kernel it will only be available for in-kernel use, and once PCR 7 has been modified the TPM won't give it to anyone else. A similar approach for some kernel command-line arguments (the kernel, module-init-tools and systemd all interpret the kernel command line left-to-right, with later arguments overriding earlier ones) would make it possible to ensure that certain kernel configuration options (such as the iommu) weren't overridable by an attacker.

There's obviously a few things that have to be done here (standardise how to embed such an initramfs in the kernel image, ensure that luks knows how to use the kernel keyring, teach all relevant bootloaders how to handle these images), but overall this should make it practical to use PCR 7 as a mechanism for supporting TPM-backed disk encryption secrets on Linux without introducing a hug support burden in the process.

[1] The patchset I've posted to add measured boot support to Grub use PCRs 8 and 9 to measure various components during the boot process, but other bootloaders may have different policies.

[2] This is because most Linux systems generate the initramfs locally rather than shipping it pre-built. It may also get rebuilt on various userspace updates, even if the kernel hasn't changed. Including it in PCR 7 would entirely break the fragility guarantees and defeat the point of all of this.

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casync Video

Posted by Lennart Poettering on July 17, 2017 10:00 PM

Video of my casync Presentation @ kinvolk

The great folks at kinvolk have uploaded a video of my casync presentation at their offices last week.

<iframe allowfullscreen="allowfullscreen" frameborder="0" height="315" src="https://www.youtube.com/embed/JnNkBJ6pr9s" width="560"></iframe>

The slides are available as well.


Migrating to blogsport

Posted by Dave Airlie on July 10, 2017 06:36 AM
Due to lots of people telling me LJ is bad, mm'kay, I've migrated to blogspot.

New blog is/will be here: https://airlied.blogspot.com

Hacker Space Rømø

Posted by Eike Rathke on July 06, 2017 08:47 PM
Of the series of precious places to hack on LibreOffice.

Hacking on LibreOffice with dune view.

Gaming hardware support

Posted by Bastien Nocera on July 06, 2017 01:27 PM
While my colleagues are working on mice that shine in all kinds of different colours, I went towards the old school.

For around 10 units of currency, you should be able to find the uDraw tablet for the PlayStation 3, the drawing tablet that brought down a company.

The device contains a large touchpad which can report one or two touches, for right-clicking (as long as the fingers aren't too close), a pen interface which will make the cheapest of the cheapest Wacom tablets feel like a professional tool from 30 years in the future, a 4-button joypad (plus Start/Select/PS) with the controls either side of the device, and an accelerometer to play Marble Madness with.

The driver landed in kernel 4.10. Note that it only supports the PlayStation 3 version of the tablet, as the Wii and XBox 360 versions require receivers that aren't part of the package. Here, a USB dongle should be provided.

Recommended for: point'n'click adventure games, set-top box menu navigation.

The second driver landed in kernel 4.12, and is a primer for more work to be done. This driver adds support for the Retrode 2's joypad adapters.

The Retrode is a USB console cartridge reader which makes Sega Mega Drive (aka Genesis) and Super Nintendo (aka Super Famicom) cartridges show up as files on a mass storage devices in your computer.

It also has 4 connectors for original joypads which the aforementioned driver now splits up and labels, so you know which is which, as well as making the mouse work out of the box. I'd still recommend picking up the newer optical model of that mouse, from Hyperkin. Moving a mouse with a ball in it is like weighing a mobile phone from that same era.

I will let you inspect the add-ons for the device, like support for additional Nintendo 64 pads and cartridges, and Game Boy/GB Color/GB Advance, and Sega Master System adapters.

Recommended for: cartridge-based retro games, obviously.

Integrated firmware updates, and better integration with Games is in the plans.

I'll leave you with this video, which shows how you could combine GNOME Games, a Retrode, this driver, a SNES mouse, and a cartridge of Mario Paint. Let's get creative :)

Using a reverse-style application IDs in your application

Posted by Richard Hughes on July 05, 2017 02:22 PM

Many upstream applications are changing their application ID from something like boxes.desktop to org.gnome.Boxes.desktop so they can be packaged as flatpaks. Where upstream doesn’t yet have this, we rewrite the desktop file in flatpak-builder so it can be packaged and deployed safely. However, more and more upstreams are building flatpaks and thus more and more apps seem to be changing desktop ID every month.

This poses a problem for the ODRS review system: When we query using the reverse-DNS-style we don’t match the hundreds of reviews submitted against the old ID. This makes the application look bad, and users file bugs against GNOME Software saying it’s broken either because “no reviews are showing up”, or that “a previously 5 star application with 30 reviews is now 2 stars with just one review”.

This also happens when companies get taken over, or when the little toy project moves from a hosting site to a proper home, e.g. com.github.FeedReader to org.gnome.FeedReader.

So, what can we do? AppData (again) to the rescue. Adding the following XML to the file allows new versions of gnome-software to do the right thing; we then get reviews and ratings for both the old and new names.


If you renamed your application in the last couple of years, I’d love you to help out and add this tag to your .appdata.xml file – in all supported branches if possible. I can’t promise cookies, but your application will have more reviews and that can’t be a bad thing. Thanks!

fwupd 0.9.5 and new goodies

Posted by Richard Hughes on July 04, 2017 03:36 PM

I’ve just released the latest version of fwupd from the development branch. 0.9.5 has the usual bug fixes, translation updates and polish, but also provides two new goodies:

We now support for updating Logitech peripherals over a protocol helpfully called DFU, which is not to be confused with the standard USB DFU protocol. This allows us to update devices such as the K780 keyboard over the Unifying layer. Although it takes a few minutes to complete, it works reliably and allows us to finally fix the receiver end of the MouseJack vulnerability. Once the user has installed the Unifying dongle update and in some cases a peripheral update they are secure again. The K780 update is in “testing” on the LVFS if anyone wants to try this straight away. You should send huge thanks to Logitech as they have provided me access to the documentation, hardware and firmware engineers required to make this possible. All the released Logitech firmwares will move to the “stable” state once this new fwupd release has hit Fedora updates-testing.

The other main feature in this release is the Intel Management Engine plugin. The IME is the source of the recent AMT vulnerability that affects the “ME blob” that is included in basically every consumer PC sold in the last decade. Although we can’t flash the ME blob using this plugin, it certainly makes it easy to query the hardware and find out if you are running a very insecure system. This plugin is more that inspired by the AMT status checker for Linux by Matthew Garrett, so you should send him cookies, not me. Actually updating the ME blob would be achieved using the standard UEFI UpdateCapsule, but it would mean your vendor does have to upload a new system firmware to the LVFS. If you’ve got a Dell you are loved, other vendors are either still testing this and don’t want to go public yet (you know who you are) or don’t care about their users. If you still don’t know what the LVFS is about, see the whitepaper and then send me an email. Anyway, obligatory technical-looking output:

$ fwupdmgr get-devices
  Guid:                 2800f812-b7b4-2d4b-aca8-46e0ff65814c
  DeviceID:             /dev/mei
  DisplayName:          Intel AMT (unprovisioned)
  Plugin:               amt
  Flags:                internal
  Version:              9.5.30
  VersionBootloader:    9.5.30

If the AMT device is present, and the display name has provisioned and the AMT version is between 6.0.x and 11.2.x, and you have not upgraded your firmware, you are vulnerable to CVE-2017-5689 and you should disable AMT in your system firmware. I’ve not yet decided if this should bubble up to the session in the form of a notification bubble, ideas welcome.

The new release is currently building for Fedora, and might be available in other distributions at some point.

libinput and pressure-based palm detection

Posted by Peter Hutterer on July 04, 2017 04:43 AM

I (finally!) merged a patchset to detect palms based on pressure into libinput. This should remove a lot of issues that our users have seen with accidental pointer movement. Palm detection in libinput previously used two approaches: disable-while-typing and an edge-based approach. The former simply ignores touchpad events while keyboard events are detected, the latter ignores touches that happen in the edge zones of the touchpad where real interaction is unlikely. Both approaches have the obvious disadvantages: they're timeout- and location-dependent, causing erroneous pointer movements. But their big advantage is that they work even on old touchpads where a lot of other information is unreliable. Touchpads are getting better, so it's time to make use of that.

The new feature is relatively simple: libinput looks at per-touch pressure and if that pressure hits a given threshold, the touch is regarded as palm. Once a palm, that touch will be ignored until touch up. The threshold is intended to be high enough that it cannot easily be hit. At least on the touchpads I have available for testing, I have to go through quite some effort to trigger palm detection with my finger.

Pressure on touchpads is unfortunately hardware-dependent and we can expect most laptops to have different pressure thresholds. For our users this means that the feature won't immediately work perfectly, it will require a lot of hwdb entries. libinput now ships a libinput measure touchpad-pressure tool to experiment with the various pressure thresholds. This makes it easy to figure out the right pressure threshold and submit a bug report (or patch) for libinput to get the pressure threshold updated. The documentation for this tool is available as part of libinput's online documentation.

TLDR: if libinput seems to misdetect touches as palms, figure out the right threshold with libinput measure touchpad-pressure and file a bug report so we can merge this into our hwdb.

mkosi — A Tool for Generating OS Images

Posted by Lennart Poettering on June 27, 2017 10:00 PM

Introducing mkosi

After blogging about casync I realized I never blogged about the mkosi tool that combines nicely with it. mkosi has been around for a while already, and its time to make it a bit better known. mkosi stands for Make Operating System Image, and is a tool for precisely that: generating an OS tree or image that can be booted.

Yes, there are many tools like mkosi, and a number of them are quite well known and popular. But mkosi has a number of features that I think make it interesting for a variety of use-cases that other tools don't cover that well.

What is mkosi?

What are those use-cases, and what does mkosi precisely set apart? mkosi is definitely a tool with a focus on developer's needs for building OS images, for testing and debugging, but also for generating production images with cryptographic protection. A typical use-case would be to add a mkosi.default file to an existing project (for example, one written in C or Python), and thus making it easy to generate an OS image for it. mkosi will put together the image with development headers and tools, compile your code in it, run your test suite, then throw away the image again, and build a new one, this time without development headers and tools, and install your build artifacts in it. This final image is then "production-ready", and only contains your built program and the minimal set of packages you configured otherwise. Such an image could then be deployed with casync (or any other tool of course) to be delivered to your set of servers, or IoT devices or whatever you are building.

mkosi is supposed to be legacy-free: the focus is clearly on today's technology, not yesteryear's. Specifically this means that we'll generate GPT partition tables, not MBR/DOS ones. When you tell mkosi to generate a bootable image for you, it will make it bootable on EFI, not on legacy BIOS. The GPT images generated follow specifications such as the Discoverable Partitions Specification, so that /etc/fstab can remain unpopulated and tools such as systemd-nspawn can automatically dissect the image and boot from them.

So, let's have a look on the specific images it can generate:

  1. Raw GPT disk image, with ext4 as root
  2. Raw GPT disk image, with btrfs as root
  3. Raw GPT disk image, with a read-only squashfs as root
  4. A plain directory on disk containing the OS tree directly (this is useful for creating generic container images)
  5. A btrfs subvolume on disk, similar to the plain directory
  6. A tarball of a plain directory

When any of the GPT choices above are selected, a couple of additional options are available:

  1. A swap partition may be added in
  2. The system may be made bootable on EFI systems
  3. Separate partitions for /home and /srv may be added in
  4. The root, /home and /srv partitions may be optionally encrypted with LUKS
  5. The root partition may be protected using dm-verity, thus making offline attacks on the generated system hard
  6. If the image is made bootable, the dm-verity root hash is automatically added to the kernel command line, and the kernel together with its initial RAM disk and the kernel command line is optionally cryptographically signed for UEFI SecureBoot

Note that mkosi is distribution-agnostic. It currently can build images based on the following Linux distributions:

  1. Fedora
  2. Debian
  3. Ubuntu
  4. ArchLinux
  5. openSUSE

Note though that not all distributions are supported at the same feature level currently. Also, as mkosi is based on dnf --installroot, debootstrap, pacstrap and zypper, and those packages are not packaged universally on all distributions, you might not be able to build images for all those distributions on arbitrary host distributions.

The GPT images are put together in a way that they aren't just compatible with UEFI systems, but also with VM and container managers (that is, at least the smart ones, i.e. VM managers that know UEFI, and container managers that grok GPT disk images) to a large degree. In fact, the idea is that you can use mkosi to build a single GPT image that may be used to:

  1. Boot on bare-metal boxes
  2. Boot in a VM
  3. Boot in a systemd-nspawn container
  4. Directly run a systemd service off, using systemd's RootImage= unit file setting

Note that in all four cases the dm-verity data is automatically used if available to ensure the image is not tampered with (yes, you read that right, systemd-nspawn and systemd's RootImage= setting automatically do dm-verity these days if the image has it.)

Mode of Operation

The simplest usage of mkosi is by simply invoking it without parameters (as root):

# mkosi

Without any configuration this will create a GPT disk image for you, will call it image.raw and drop it in the current directory. The distribution used will be the same one as your host runs.

Of course in most cases you want more control about how the image is put together, i.e. select package sets, select the distribution, size partitions and so on. Most of that you can actually specify on the command line, but it is recommended to instead create a couple of mkosi.$SOMETHING files and directories in some directory. Then, simply change to that directory and run mkosi without any further arguments. The tool will then look in the current working directory for these files and directories and make use of them (similar to how make looks for a Makefile…). Every single file/directory is optional, but if they exist they are honored. Here's a list of the files/directories mkosi currently looks for:

  1. mkosi.default — This is the main configuration file, here you can configure what kind of image you want, which distribution, which packages and so on.

  2. mkosi.extra/ — If this directory exists, then mkosi will copy everything inside it into the images built. You can place arbitrary directory hierarchies in here, and they'll be copied over whatever is already in the image, after it was put together by the distribution's package manager. This is the best way to drop additional static files into the image, or override distribution-supplied ones.

  3. mkosi.build — This executable file is supposed to be a build script. When it exists, mkosi will build two images, one after the other in the mode already mentioned above: the first version is the build image, and may include various build-time dependencies such as a compiler or development headers. The build script is also copied into it, and then run inside it. The script should then build whatever shall be built and place the result in $DESTDIR (don't worry, popular build tools such as Automake or Meson all honor $DESTDIR anyway, so there's not much to do here explicitly). It may also run a test suite, or anything else you like. After the script finished, the build image is removed again, and a second image (the final image) is built. This time, no development packages are included, and the build script is not copied into the image again — however, the build artifacts from the first run (i.e. those placed in $DESTDIR) are copied into the image.

  4. mkosi.postinst — If this executable script exists, it is invoked inside the image (inside a systemd-nspawn invocation) and can adjust the image as it likes at a very late point in the image preparation. If mkosi.build exists, i.e. the dual-phased development build process used, then this script will be invoked twice: once inside the build image and once inside the final image. The first parameter passed to the script clarifies which phase it is run in.

  5. mkosi.nspawn — If this file exists, it should contain a container configuration file for systemd-nspawn (see systemd.nspawn(5) for details), which shall be shipped along with the final image and shall be included in the check-sum calculations (see below).

  6. mkosi.cache/ — If this directory exists, it is used as package cache directory for the builds. This directory is effectively bind mounted into the image at build time, in order to speed up building images. The package installers of the various distributions will place their package files here, so that subsequent runs can reuse them.

  7. mkosi.passphrase — If this file exists, it should contain a pass-phrase to use for the LUKS encryption (if that's enabled for the image built). This file should not be readable to other users.

  8. mkosi.secure-boot.crt and mkosi.secure-boot.key should be an X.509 key pair to use for signing the kernel and initrd for UEFI SecureBoot, if that's enabled.

How to use it

So, let's come back to our most trivial example, without any of the mkosi.$SOMETHING files around:

# mkosi

As mentioned, this will create a build file image.raw in the current directory. How do we use it? Of course, we could dd it onto some USB stick and boot it on a bare-metal device. However, it's much simpler to first run it in a container for testing:

# systemd-nspawn -bi image.raw

And there you go: the image should boot up, and just work for you.

Now, let's make things more interesting. Let's still not use any of the mkosi.$SOMETHING files around:

# mkosi -t raw_btrfs --bootable -o foobar.raw
# systemd-nspawn -bi foobar.raw

This is similar as the above, but we made three changes: it's no longer GPT + ext4, but GPT + btrfs. Moreover, the system is made bootable on UEFI systems, and finally, the output is now called foobar.raw.

Because this system is bootable on UEFI systems, we can run it in KVM:

qemu-kvm -m 512 -smp 2 -bios /usr/share/edk2/ovmf/OVMF_CODE.fd -drive format=raw,file=foobar.raw

This will look very similar to the systemd-nspawn invocation, except that this uses full VM virtualization rather than container virtualization. (Note that the way to run a UEFI qemu/kvm instance appears to change all the time and is different on the various distributions. It's quite annoying, and I can't really tell you what the right qemu command line is to make this work on your system.)

Of course, it's not all raw GPT disk images with mkosi. Let's try a plain directory image:

# mkosi -d fedora -t directory -o quux
# systemd-nspawn -bD quux

Of course, if you generate the image as plain directory you can't boot it on bare-metal just like that, nor run it in a VM.

A more complex command line is the following:

# mkosi -d fedora -t raw_squashfs --checksum --xz --package=openssh-clients --package=emacs

In this mode we explicitly pick Fedora as the distribution to use, ask mkosi to generate a compressed GPT image with a root squashfs, compress the result with xz, and generate a SHA256SUMS file with the hashes of the generated artifacts. The package will contain the SSH client as well as everybody's favorite editor.

Now, let's make use of the various mkosi.$SOMETHING files. Let's say we are working on some Automake-based project and want to make it easy to generate a disk image off the development tree with the version you are hacking on. Create a configuration file:

# cat > mkosi.default <<EOF


# The packages to appear in both the build and the final image
Packages=openssh-clients httpd
# The packages to appear in the build image, but absent from the final image
BuildPackages=make gcc libcurl-devel

And let's add a build script:

# cat > mkosi.build <<EOF
./configure --prefix=/usr
make -j `nproc`
make install
# chmod +x mkosi.build

And with all that in place we can now build our project into a disk image, simply by typing:

# mkosi

Let's try it out:

# systemd-nspawn -bi image.raw

Of course, if you do this you'll notice that building an image like this can be quite slow. And slow build times are actively hurtful to your productivity as a developer. Hence let's make things a bit faster. First, let's make use of a package cache shared between runs:

# mkdir mkosi.cache

Building images now should already be substantially faster (and generate less network traffic) as the packages will now be downloaded only once and reused. However, you'll notice that unpacking all those packages and the rest of the work is still quite slow. But mkosi can help you with that. Simply use mkosi's incremental build feature. In this mode mkosi will make a copy of the build and final images immediately before dropping in your build sources or artifacts, so that building an image becomes a lot quicker: instead of always starting totally from scratch a build will now reuse everything it can reuse from a previous run, and immediately begin with building your sources rather than the build image to build your sources in. To enable the incremental build feature use -i:

# mkosi -i

Note that if you use this option, the package list is not updated anymore from your distribution's servers, as the cached copy is made after all packages are installed, and hence until you actually delete the cached copy the distribution's network servers aren't contacted again and no RPMs or DEBs are downloaded. This means the distribution you use becomes "frozen in time" this way. (Which might be a bad thing, but also a good thing, as it makes things kinda reproducible.)

Of course, if you run mkosi a couple of times you'll notice that it won't overwrite the generated image when it already exists. You can either delete the file yourself first (rm image.raw) or let mkosi do it for you right before building a new image, with mkosi -f. You can also tell mkosi to not only remove any such pre-existing images, but also remove any cached copies of the incremental feature, by using -f twice.

I wrote mkosi originally in order to test systemd, and quickly generate a disk image of various distributions with the most current systemd version from git, without all that affecting my host system. I regularly use mkosi for that today, in incremental mode. The two commands I use most in that context are:

# mkosi -if && systemd-nspawn -bi image.raw

And sometimes:

# mkosi -iff && systemd-nspawn -bi image.raw

The latter I use only if I want to regenerate everything based on the very newest set of RPMs provided by Fedora, instead of a cached snapshot of it.

BTW, the mkosi files for systemd are included in the systemd git tree: mkosi.default and mkosi.build. This way, any developer who wants to quickly test something with current systemd git, or wants to prepare a patch based on it and test it can check out the systemd repository and simply run mkosi in it and a few minutes later he has a bootable image he can test in systemd-nspawn or KVM. casync has similar files: mkosi.default, mkosi.build.

Random Interesting Features

  1. As mentioned already, mkosi will generate dm-verity enabled disk images if you ask for it. For that use the --verity switch on the command line or Verity= setting in mkosi.default. Of course, dm-verity implies that the root volume is read-only. In this mode the top-level dm-verity hash will be placed along-side the output disk image in a file named the same way, but with the .roothash suffix. If the image is to be created bootable, the root hash is also included on the kernel command line in the roothash= parameter, which current systemd versions can use to both find and activate the root partition in a dm-verity protected way. BTW: it's a good idea to combine this dm-verity mode with the raw_squashfs image mode, to generate a genuinely protected, compressed image suitable for running in your IoT device.

  2. As indicated above, mkosi can automatically create a check-sum file SHA256SUMS for you (--checksum) covering all the files it outputs (which could be the image file itself, a matching .nspawn file using the mkosi.nspawn file mentioned above, as well as the .roothash file for the dm-verity root hash.) It can then optionally sign this with gpg (--sign). Note that systemd's machinectl pull-tar and machinectl pull-raw command can download these files and the SHA256SUMS file automatically and verify things on download. With other words: what mkosi outputs is perfectly ready for downloads using these two systemd commands.

  3. As mentioned, mkosi is big on supporting UEFI SecureBoot. To make use of that, place your X.509 key pair in two files mkosi.secureboot.crt and mkosi.secureboot.key, and set SecureBoot= or --secure-boot. If so, mkosi will sign the kernel/initrd/kernel command line combination during the build. Of course, if you use this mode, you should also use Verity=/--verity=, otherwise the setup makes only partial sense. Note that mkosi will not help you with actually enrolling the keys you use in your UEFI BIOS.

  4. mkosi has minimal support for GIT checkouts: when it recognizes it is run in a git checkout and you use the mkosi.build script stuff, the source tree will be copied into the build image, but will all files excluded by .gitignore removed.

  5. There's support for encryption in place. Use --encrypt= or Encrypt=. Note that the UEFI ESP is never encrypted though, and the root partition only if explicitly requested. The /home and /srv partitions are unconditionally encrypted if that's enabled.

  6. Images may be built with all documentation removed.

  7. The password for the root user and additional kernel command line arguments may be configured for the image to generate.

Minimum Requirements

Current mkosi requires Python 3.5, and has a number of dependencies, listed in the README. Most notably you need a somewhat recent systemd version to make use of its full feature set: systemd 233. Older versions are already packaged for various distributions, but much of what I describe above is only available in the most recent release mkosi 3.

The UEFI SecureBoot support requires sbsign which currently isn't available in Fedora, but there's a COPR.


It is my intention to continue turning mkosi into a tool suitable for:

  1. Testing and debugging projects
  2. Building images for secure devices
  3. Building portable service images
  4. Building images for secure VMs and containers

One of the biggest goals I have for the future is to teach mkosi and systemd/sd-boot native support for A/B IoT style partition setups. The idea is that the combination of systemd, casync and mkosi provides generic building blocks for building secure, auto-updating devices in a generic way from, even though all pieces may be used individually, too.


  1. Why are you reinventing the wheel again? This is exactly like $SOMEOTHERPROJECT! — Well, to my knowledge there's no tool that integrates this nicely with your project's development tree, and can do dm-verity and UEFI SecureBoot and all that stuff for you. So nope, I don't think this exactly like $SOMEOTHERPROJECT, thank you very much.

  2. What about creating MBR/DOS partition images? — That's really out of focus to me. This is an exercise in figuring out how generic OSes and devices in the future should be built and an attempt to commoditize OS image building. And no, the future doesn't speak MBR, sorry. That said, I'd be quite interested in adding support for booting on Raspberry Pi, possibly using a hybrid approach, i.e. using a GPT disk label, but arranging things in a way that the Raspberry Pi boot protocol (which is built around DOS partition tables), can still work.

  3. Is this portable? — Well, depends what you mean by portable. No, this tool runs on Linux only, and as it uses systemd-nspawn during the build process it doesn't run on non-systemd systems either. But then again, you should be able to create images for any architecture you like with it, but of course if you want the image bootable on bare-metal systems only systems doing UEFI are supported (but systemd-nspawn should still work fine on them).

  4. Where can I get this stuff? — Try GitHub. And some distributions carry packaged versions, but I think none of them the current v3 yet.

  5. Is this a systemd project? — Yes, it's hosted under the systemd GitHub umbrella. And yes, during run-time systemd-nspawn in a current version is required. But no, the code-bases are separate otherwise, already because systemd is a C project, and mkosi Python.

  6. Requiring systemd 233 is a pretty steep requirement, no? — Yes, but the feature we need kind of matters (systemd-nspawn's --overlay= switch), and again, this isn't supposed to be a tool for legacy systems.

  7. Can I run the resulting images in LXC or Docker? — Humm, I am not an LXC nor Docker guy. If you select directory or subvolume as image type, LXC should be able to boot the generated images just fine, but I didn't try. Last time I looked, Docker doesn't permit running proper init systems as PID 1 inside the container, as they define their own run-time without intention to emulate a proper system. Hence, no I don't think it will work, at least not with an unpatched Docker version. That said, again, don't ask me questions about Docker, it's not precisely my area of expertise, and quite frankly I am not a fan. To my knowledge neither LXC nor Docker are able to run containers directly off GPT disk images, hence the various raw_xyz image types are definitely not compatible with either. That means if you want to generate a single raw disk image that can be booted unmodified both in a container and on bare-metal, then systemd-nspawn is the container manager to go for (specifically, its -i/--image= switch).

Should you care? Is this a tool for you?

Well, that's up to you really.

If you hack on some complex project and need a quick way to compile and run your project on a specific current Linux distribution, then mkosi is an excellent way to do that. Simply drop the mkosi.default and mkosi.build files in your git tree and everything will be easy. (And of course, as indicated above: if the project you are hacking on happens to be called systemd or casync be aware that those files are already part of the git tree — you can just use them.)

If you hack on some embedded or IoT device, then mkosi is a great choice too, as it will make it reasonably easy to generate secure images that are protected against offline modification, by using dm-verity and UEFI SecureBoot.

If you are an administrator and need a nice way to build images for a VM or systemd-nspawn container, or a portable service then mkosi is an excellent choice too.

If you care about legacy computers, old distributions, non-systemd init systems, old VM managers, Docker, … then no, mkosi is not for you, but there are plenty of well-established alternatives around that cover that nicely.

And never forget: mkosi is an Open Source project. We are happy to accept your patches and other contributions.

Oh, and one unrelated last thing: don't forget to submit your talk proposal and/or buy a ticket for All Systems Go! 2017 in Berlin — the conference where things like systemd, casync and mkosi are discussed, along with a variety of other Linux userspace projects used for building systems.

casync — A tool for distributing file system images

Posted by Lennart Poettering on June 19, 2017 10:00 PM

Introducing casync

In the past months I have been working on a new project: casync. casync takes inspiration from the popular rsync file synchronization tool as well as the probably even more popular git revision control system. It combines the idea of the rsync algorithm with the idea of git-style content-addressable file systems, and creates a new system for efficiently storing and delivering file system images, optimized for high-frequency update cycles over the Internet. Its current focus is on delivering IoT, container, VM, application, portable service or OS images, but I hope to extend it later in a generic fashion to become useful for backups and home directory synchronization as well (but more about that later).

The basic technological building blocks casync is built from are neither new nor particularly innovative (at least not anymore), however the way casync combines them is different from existing tools, and that's what makes it useful for a variety of use-cases that other tools can't cover that well.


I created casync after studying how today's popular tools store and deliver file system images. To briefly name a few: Docker has a layered tarball approach, OSTree serves the individual files directly via HTTP and maintains packed deltas to speed up updates, while other systems operate on the block layer and place raw squashfs images (or other archival file systems, such as IS09660) for download on HTTP shares (in the better cases combined with zsync data).

Neither of these approaches appeared fully convincing to me when used in high-frequency update cycle systems. In such systems, it is important to optimize towards a couple of goals:

  1. Most importantly, make updates cheap traffic-wise (for this most tools use image deltas of some form)
  2. Put boundaries on disk space usage on servers (keeping deltas between all version combinations clients might want to run updates between, would suggest keeping an exponentially growing amount of deltas on servers)
  3. Put boundaries on disk space usage on clients
  4. Be friendly to Content Delivery Networks (CDNs), i.e. serve neither too many small nor too many overly large files, and only require the most basic form of HTTP. Provide the repository administrator with high-level knobs to tune the average file size delivered.
  5. Simplicity to use for users, repository administrators and developers

I don't think any of the tools mentioned above are really good on more than a small subset of these points.

Specifically: Docker's layered tarball approach dumps the "delta" question onto the feet of the image creators: the best way to make your image downloads minimal is basing your work on an existing image clients might already have, and inherit its resources, maintaining full history. Here, revision control (a tool for the developer) is intermingled with update management (a concept for optimizing production delivery). As container histories grow individual deltas are likely to stay small, but on the other hand a brand-new deployment usually requires downloading the full history onto the deployment system, even though there's no use for it there, and likely requires substantially more disk space and download sizes.

OSTree's serving of individual files is unfriendly to CDNs (as many small files in file trees cause an explosion of HTTP GET requests). To counter that OSTree supports placing pre-calculated delta images between selected revisions on the delivery servers, which means a certain amount of revision management, that leaks into the clients.

Delivering direct squashfs (or other file system) images is almost beautifully simple, but of course means every update requires a full download of the newest image, which is both bad for disk usage and generated traffic. Enhancing it with zsync makes this a much better option, as it can reduce generated traffic substantially at very little cost of history/meta-data (no explicit deltas between a large number of versions need to be prepared server side). On the other hand server requirements in disk space and functionality (HTTP Range requests) are minus points for the use-case I am interested in.

(Note: all the mentioned systems have great properties, and it's not my intention to badmouth them. They only point I am trying to make is that for the use case I care about — file system image delivery with high high frequency update-cycles — each system comes with certain drawbacks.)

Security & Reproducibility

Besides the issues pointed out above I wasn't happy with the security and reproducibility properties of these systems. In today's world where security breaches involving hacking and breaking into connected systems happen every day, an image delivery system that cannot make strong guarantees regarding data integrity is out of date. Specifically, the tarball format is famously nondeterministic: the very same file tree can result in any number of different valid serializations depending on the tool used, its version and the underlying OS and file system. Some tar implementations attempt to correct that by guaranteeing that each file tree maps to exactly one valid serialization, but such a property is always only specific to the tool used. I strongly believe that any good update system must guarantee on every single link of the chain that there's only one valid representation of the data to deliver, that can easily be verified.

What casync Is

So much about the background why I created casync. Now, let's have a look what casync actually is like, and what it does. Here's the brief technical overview:

Encoding: Let's take a large linear data stream, split it into variable-sized chunks (the size of each being a function of the chunk's contents), and store these chunks in individual, compressed files in some directory, each file named after a strong hash value of its contents, so that the hash value may be used to as key for retrieving the full chunk data. Let's call this directory a "chunk store". At the same time, generate a "chunk index" file that lists these chunk hash values plus their respective chunk sizes in a simple linear array. The chunking algorithm is supposed to create variable, but similarly sized chunks from the data stream, and do so in a way that the same data results in the same chunks even if placed at varying offsets. For more information see this blog story.

Decoding: Let's take the chunk index file, and reassemble the large linear data stream by concatenating the uncompressed chunks retrieved from the chunk store, keyed by the listed chunk hash values.

As an extra twist, we introduce a well-defined, reproducible, random-access serialization format for file trees (think: a more modern tar), to permit efficient, stable storage of complete file trees in the system, simply by serializing them and then passing them into the encoding step explained above.

Finally, let's put all this on the network: for each image you want to deliver, generate a chunk index file and place it on an HTTP server. Do the same with the chunk store, and share it between the various index files you intend to deliver.

Why bother with all of this? Streams with similar contents will result in mostly the same chunk files in the chunk store. This means it is very efficient to store many related versions of a data stream in the same chunk store, thus minimizing disk usage. Moreover, when transferring linear data streams chunks already known on the receiving side can be made use of, thus minimizing network traffic.

Why is this different from rsync or OSTree, or similar tools? Well, one major difference between casync and those tools is that we remove file boundaries before chunking things up. This means that small files are lumped together with their siblings and large files are chopped into pieces, which permits us to recognize similarities in files and directories beyond file boundaries, and makes sure our chunk sizes are pretty evenly distributed, without the file boundaries affecting them.

The "chunking" algorithm is based on a the buzhash rolling hash function. SHA256 is used as strong hash function to generate digests of the chunks. xz is used to compress the individual chunks.

Here's a diagram, hopefully explaining a bit how the encoding process works, wasn't it for my crappy drawing skills:


The diagram shows the encoding process from top to bottom. It starts with a block device or a file tree, which is then serialized and chunked up into variable sized blocks. The compressed chunks are then placed in the chunk store, while a chunk index file is written listing the chunk hashes in order. (The original SVG of this graphic may be found here.)


Note that casync operates on two different layers, depending on the use-case of the user:

  1. You may use it on the block layer. In this case the raw block data on disk is taken as-is, read directly from the block device, split into chunks as described above, compressed, stored and delivered.

  2. You may use it on the file system layer. In this case, the file tree serialization format mentioned above comes into play: the file tree is serialized depth-first (much like tar would do it) and then split into chunks, compressed, stored and delivered.

The fact that it may be used on both the block and file system layer opens it up for a variety of different use-cases. In the VM and IoT ecosystems shipping images as block-level serializations is more common, while in the container and application world file-system-level serializations are more typically used.

Chunk index files referring to block-layer serializations carry the .caibx suffix, while chunk index files referring to file system serializations carry the .caidx suffix. Note that you may also use casync as direct tar replacement, i.e. without the chunking, just generating the plain linear file tree serialization. Such files carry the .catar suffix. Internally .caibx are identical to .caidx files, the only difference is semantical: .caidx files describe a .catar file, while .caibx files may describe any other blob. Finally, chunk stores are directories carrying the .castr suffix.


Here are a couple of other features casync has:

  1. When downloading a new image you may use casync's --seed= feature: each block device, file, or directory specified is processed using the same chunking logic described above, and is used as preferred source when putting together the downloaded image locally, avoiding network transfer of it. This of course is useful whenever updating an image: simply specify one or more old versions as seed and only download the chunks that truly changed since then. Note that using seeds requires no history relationship between seed and the new image to download. This has major benefits: you can even use it to speed up downloads of relatively foreign and unrelated data. For example, when downloading a container image built using Ubuntu you can use your Fedora host OS tree in /usr as seed, and casync will automatically use whatever it can from that tree, for example timezone and locale data that tends to be identical between distributions. Example: casync extract http://example.com/myimage.caibx --seed=/dev/sda1 /dev/sda2. This will place the block-layer image described by the indicated URL in the /dev/sda2 partition, using the existing /dev/sda1 data as seeding source. An invocation like this could be typically used by IoT systems with an A/B partition setup. Example 2: casync extract http://example.com/mycontainer-v3.caidx --seed=/srv/container-v1 --seed=/srv/container-v2 /src/container-v3, is very similar but operates on the file system layer, and uses two old container versions to seed the new version.

  2. When operating on the file system level, the user has fine-grained control on the meta-data included in the serialization. This is relevant since different use-cases tend to require a different set of saved/restored meta-data. For example, when shipping OS images, file access bits/ACLs and ownership matter, while file modification times hurt. When doing personal backups OTOH file ownership matters little but file modification times are important. Moreover different backing file systems support different feature sets, and storing more information than necessary might make it impossible to validate a tree against an image if the meta-data cannot be replayed in full. Due to this, casync provides a set of --with= and --without= parameters that allow fine-grained control of the data stored in the file tree serialization, including the granularity of modification times and more. The precise set of selected meta-data features is also always part of the serialization, so that seeding can work correctly and automatically.

  3. casync tries to be as accurate as possible when storing file system meta-data. This means that besides the usual baseline of file meta-data (file ownership and access bits), and more advanced features (extended attributes, ACLs, file capabilities) a number of more exotic data is stored as well, including Linux chattr(1) file attributes, as well as FAT file attributes (you may wonder why the latter? — EFI is FAT, and /efi is part of the comprehensive serialization of any host). In the future I intend to extend this further, for example storing btrfs sub-volume information where available. Note that as described above every single type of meta-data may be turned off and on individually, hence if you don't need FAT file bits (and I figure it's pretty likely you don't), then they won't be stored.

  4. The user creating .caidx or .caibx files may control the desired average chunk length (before compression) freely, using the --chunk-size= parameter. Smaller chunks increase the number of generated files in the chunk store and increase HTTP GET load on the server, but also ensure that sharing between similar images is improved, as identical patterns in the images stored are more likely to be recognized. By default casync will use a 64K average chunk size. Tweaking this can be particularly useful when adapting the system to specific CDNs, or when delivering compressed disk images such as squashfs (see below).

  5. Emphasis is placed on making all invocations reproducible, well-defined and strictly deterministic. As mentioned above this is a requirement to reach the intended security guarantees, but is also useful for many other use-cases. For example, the casync digest command may be used to calculate a hash value identifying a specific directory in all desired detail (use --with= and --without to pick the desired detail). Moreover the casync mtree command may be used to generate a BSD mtree(5) compatible manifest of a directory tree, .caidx or .catar file.

  6. The file system serialization format is nicely composable. By this I mean that the serialization of a file tree is the concatenation of the serializations of all files and file sub-trees located at the top of the tree, with zero meta-data references from any of these serializations into the others. This property is essential to ensure maximum reuse of chunks when similar trees are serialized.

  7. When extracting file trees or disk image files, casync will automatically create reflinks from any specified seeds if the underlying file system supports it (such as btrfs, ocfs, and future xfs). After all, instead of copying the desired data from the seed, we can just tell the file system to link up the relevant blocks. This works both when extracting .caidx and .caibx files — the latter of course only when the extracted disk image is placed in a regular raw image file on disk, rather than directly on a plain block device, as plain block devices do not know the concept of reflinks.

  8. Optionally, when extracting file trees, casync can create traditional UNIX hard-links for identical files in specified seeds (--hardlink=yes). This works on all UNIX file systems, and can save substantial amounts of disk space. However, this only works for very specific use-cases where disk images are considered read-only after extraction, as any changes made to one tree will propagate to all other trees sharing the same hard-linked files, as that's the nature of hard-links. In this mode, casync exposes OSTree-like behavior, which is built heavily around read-only hard-link trees.

  9. casync tries to be smart when choosing what to include in file system images. Implicitly, file systems such as procfs and sysfs are excluded from serialization, as they expose API objects, not real files. Moreover, the "nodump" (+d) chattr(1) flag is honored by default, permitting users to mark files to exclude from serialization.

  10. When creating and extracting file trees casync may apply an automatic or explicit UID/GID shift. This is particularly useful when transferring container image for use with Linux user name-spacing.

  11. In addition to local operation, casync currently supports HTTP, HTTPS, FTP and ssh natively for downloading chunk index files and chunks (the ssh mode requires installing casync on the remote host, though, but an sftp mode not requiring that should be easy to add). When creating index files or chunks, only ssh is supported as remote back-end.

  12. When operating on block-layer images, you may expose locally or remotely stored images as local block devices. Example: casync mkdev http://example.com/myimage.caibx exposes the disk image described by the indicated URL as local block device in /dev, which you then may use the usual block device tools on, such as mount or fdisk (only read-only though). Chunks are downloaded on access with high priority, and at low priority when idle in the background. Note that in this mode, casync also plays a role similar to "dm-verity", as all blocks are validated against the strong digests in the chunk index file before passing them on to the kernel's block layer. This feature is implemented though Linux' NBD kernel facility.

  13. Similar, when operating on file-system-layer images, you may mount locally or remotely stored images as regular file systems. Example: casync mount http://example.com/mytree.caidx /srv/mytree mounts the file tree image described by the indicated URL as a local directory /srv/mytree. This feature is implemented though Linux' FUSE kernel facility. Note that special care is taken that the images exposed this way can be packed up again with casync make and are guaranteed to return the bit-by-bit exact same serialization again that it was mounted from. No data is lost or changed while passing things through FUSE (OK, strictly speaking this is a lie, we do lose ACLs, but that's hopefully just a temporary gap to be fixed soon).

  14. In IoT A/B fixed size partition setups the file systems placed in the two partitions are usually much shorter than the partition size, in order to keep some room for later, larger updates. casync is able to analyze the super-block of a number of common file systems in order to determine the actual size of a file system stored on a block device, so that writing a file system to such a partition and reading it back again will result in reproducible data. Moreover this speeds up the seeding process, as there's little point in seeding the white-space after the file system within the partition.

Example Command Lines

Here's how to use casync, explained with a few examples:

$ casync make foobar.caidx /some/directory

This will create a chunk index file foobar.caidx in the local directory, and populate the chunk store directory default.castr located next to it with the chunks of the serialization (you can change the name for the store directory with --store= if you like). This command operates on the file-system level. A similar command operating on the block level:

$ casync make foobar.caibx /dev/sda1

This command creates a chunk index file foobar.caibx in the local directory describing the current contents of the /dev/sda1 block device, and populates default.castr in the same way as above. Note that you may as well read a raw disk image from a file instead of a block device:

$ casync make foobar.caibx myimage.raw

To reconstruct the original file tree from the .caidx file and the chunk store of the first command, use:

$ casync extract foobar.caidx /some/other/directory

And similar for the block-layer version:

$ casync extract foobar.caibx /dev/sdb1

or, to extract the block-layer version into a raw disk image:

$ casync extract foobar.caibx myotherimage.raw

The above are the most basic commands, operating on local data only. Now let's make this more interesting, and reference remote resources:

$ casync extract http://example.com/images/foobar.caidx /some/other/directory

This extracts the specified .caidx onto a local directory. This of course assumes that foobar.caidx was uploaded to the HTTP server in the first place, along with the chunk store. You can use any command you like to accomplish that, for example scp or rsync. Alternatively, you can let casync do this directly when generating the chunk index:

$ casync make ssh.example.com:images/foobar.caidx /some/directory

This will use ssh to connect to the ssh.example.com server, and then places the .caidx file and the chunks on it. Note that this mode of operation is "smart": this scheme will only upload chunks currently missing on the server side, and not re-transmit what already is available.

Note that you can always configure the precise path or URL of the chunk store via the --store= option. If you do not do that, then the store path is automatically derived from the path or URL: the last component of the path or URL is replaced by default.castr.

Of course, when extracting .caidx or .caibx files from remote sources, using a local seed is advisable:

$ casync extract http://example.com/images/foobar.caidx --seed=/some/exising/directory /some/other/directory

Or on the block layer:

$ casync extract http://example.com/images/foobar.caibx --seed=/dev/sda1 /dev/sdb2

When creating chunk indexes on the file system layer casync will by default store meta-data as accurately as possible. Let's create a chunk index with reduced meta-data:

$ casync make foobar.caidx --with=sec-time --with=symlinks --with=read-only /some/dir

This command will create a chunk index for a file tree serialization that has three features above the absolute baseline supported: 1s granularity time-stamps, symbolic links and a single read-only bit. In this mode, all the other meta-data bits are not stored, including nanosecond time-stamps, full UNIX permission bits, file ownership or even ACLs or extended attributes.

Now let's make a .caidx file available locally as a mounted file system, without extracting it:

$ casync mount http://example.comf/images/foobar.caidx /mnt/foobar

And similar, let's make a .caibx file available locally as a block device:

$ casync mkdev http://example.comf/images/foobar.caibx

This will create a block device in /dev and print the used device node path to STDOUT.

As mentioned, casync is big about reproducibility. Let's make use of that to calculate the a digest identifying a very specific version of a file tree:

$ casync digest .

This digest will include all meta-data bits casync and the underlying file system know about. Usually, to make this useful you want to configure exactly what meta-data to include:

$ casync digest --with=unix .

This makes use of the --with=unix shortcut for selecting meta-data fields. Specifying --with-unix= selects all meta-data that traditional UNIX file systems support. It is a shortcut for writing out: --with=16bit-uids --with=permissions --with=sec-time --with=symlinks --with=device-nodes --with=fifos --with=sockets.

Note that when calculating digests or creating chunk indexes you may also use the negative --without= option to remove specific features but start from the most precise:

$ casync digest --without=flag-immutable

This generates a digest with the most accurate meta-data, but leaves one feature out: chattr(1)'s immutable (+i) file flag.

To list the contents of a .caidx file use a command like the following:

$ casync list http://example.com/images/foobar.caidx


$ casync mtree http://example.com/images/foobar.caidx

The former command will generate a brief list of files and directories, not too different from tar t or ls -al in its output. The latter command will generate a BSD mtree(5) compatible manifest. Note that casync actually stores substantially more file meta-data than mtree files can express, though.

What casync isn't

  1. casync is not an attempt to minimize serialization and downloaded deltas to the extreme. Instead, the tool is supposed to find a good middle ground, that is good on traffic and disk space, but not at the price of convenience or requiring explicit revision control. If you care about updates that are absolutely minimal, there are binary delta systems around that might be an option for you, such as Google's Courgette.

  2. casync is not a replacement for rsync, or git or zsync or anything like that. They have very different use-cases and semantics. For example, rsync permits you to directly synchronize two file trees remotely. casync just cannot do that, and it is unlikely it every will.

Where next?

casync is supposed to be a generic synchronization tool. Its primary focus for now is delivery of OS images, but I'd like to make it useful for a couple other use-cases, too. Specifically:

  1. To make the tool useful for backups, encryption is missing. I have pretty concrete plans how to add that. When implemented, the tool might become an alternative to restic, BorgBackup or tarsnap.

  2. Right now, if you want to deploy casync in real-life, you still need to validate the downloaded .caidx or .caibx file yourself, for example with some gpg signature. It is my intention to integrate with gpg in a minimal way so that signing and verifying chunk index files is done automatically.

  3. In the longer run, I'd like to build an automatic synchronizer for $HOME between systems from this. Each $HOME instance would be stored automatically in regular intervals in the cloud using casync, and conflicts would be resolved locally.

  4. casync is written in a shared library style, but it is not yet built as one. Specifically this means that almost all of casync's functionality is supposed to be available as C API soon, and applications can process casync files on every level. It is my intention to make this library useful enough so that it will be easy to write a module for GNOME's gvfs subsystem in order to make remote or local .caidx files directly available to applications (as an alternative to casync mount). In fact the idea is to make this all flexible enough that even the remoting back-ends can be replaced easily, for example to replace casync's default HTTP/HTTPS back-ends built on CURL with GNOME's own HTTP implementation, in order to share cookies, certificates, … There's also an alternative method to integrate with casync in place already: simply invoke casync as a sub-process. casync will inform you about a certain set of state changes using a mechanism compatible with sd_notify(3). In future it will also propagate progress data this way and more.

  5. I intend to a add a new seeding back-end that sources chunks from the local network. After downloading the new .caidx file off the Internet casync would then search for the listed chunks on the local network first before retrieving them from the Internet. This should speed things up on all installations that have multiple similar systems deployed in the same network.

Further plans are listed tersely in the TODO file.


  1. Is this a systemd project?casync is hosted under the github systemd umbrella, and the projects share the same coding style. However, the code-bases are distinct and without interdependencies, and casync works fine both on systemd systems and systems without it.

  2. Is casync portable? — At the moment: no. I only run Linux and that's what I code for. That said, I am open to accepting portability patches (unlike for systemd, which doesn't really make sense on non-Linux systems), as long as they don't interfere too much with the way casync works. Specifically this means that I am not too enthusiastic about merging portability patches for OSes lacking the openat(2) family of APIs.

  3. Does casync require reflink-capable file systems to work, such as btrfs? — No it doesn't. The reflink magic in casync is employed when the file system permits it, and it's good to have it, but it's not a requirement, and casync will implicitly fall back to copying when it isn't available. Note that casync supports a number of file system features on a variety of file systems that aren't available everywhere, for example FAT's system/hidden file flags or xfs's projinherit file flag.

  4. Is casync stable? — I just tagged the first, initial release. While I have been working on it since quite some time and it is quite featureful, this is the first time I advertise it publicly, and it hence received very little testing outside of its own test suite. I am also not fully ready to commit to the stability of the current serialization or chunk index format. I don't see any breakages coming for it though. casync is pretty light on documentation right now, and does not even have a man page. I also intend to correct that soon.

  5. Are the .caidx/.caibx and .catar file formats open and documented?casync is Open Source, so if you want to know the precise format, have a look at the sources for now. It's definitely my intention to add comprehensive docs for both formats however. Don't forget this is just the initial version right now.

  6. casync is just like $SOMEOTHERTOOL! Why are you reinventing the wheel (again)? — Well, because casync isn't "just like" some other tool. I am pretty sure I did my homework, and that there is no tool just like casync right now. The tools coming closest are probably rsync, zsync, tarsnap, restic, but they are quite different beasts each.

  7. Why did you invent your own serialization format for file trees? Why don't you just use tar? — That's a good question, and other systems — most prominently tarsnap — do that. However, as mentioned above tar doesn't enforce reproducibility. It also doesn't really do random access: if you want to access some specific file you need to read every single byte stored before it in the tar archive to find it, which is of course very expensive. The serialization casync implements places a focus on reproducibility, random access, and meta-data control. Much like traditional tar it can still be generated and extracted in a stream fashion though.

  8. Does casync save/restore SELinux/SMACK file labels? — At the moment not. That's not because I wouldn't want it to, but simply because I am not a guru of either of these systems, and didn't want to implement something I do not fully grok nor can test. If you look at the sources you'll find that there's already some definitions in place that keep room for them though. I'd be delighted to accept a patch implementing this fully.

  9. What about delivering squashfs images? How well does chunking work on compressed serializations? – That's a very good point! Usually, if you apply the a chunking algorithm to a compressed data stream (let's say a tar.gz file), then changing a single bit at the front will propagate into the entire remainder of the file, so that minimal changes will explode into major changes. Thankfully this doesn't apply that strictly to squashfs images, as it provides random access to files and directories and thus breaks up the compression streams in regular intervals to make seeking easy. This fact is beneficial for systems employing chunking, such as casync as this means single bit changes might affect their vicinity but will not explode in an unbounded fashion. In order achieve best results when delivering squashfs images through casync the block sizes of squashfs and the chunks sizes of casync should be matched up (using casync's --chunk-size= option). How precisely to choose both values is left a research subject for the user, for now.

  10. What does the name casync mean? – It's a synchronizing tool, hence the -sync suffix, following rsync's naming. It makes use of the content-addressable concept of git hence the ca- prefix.

  11. Where can I get this stuff? Is it already packaged? – Check out the sources on GitHub. I just tagged the first version. Martin Pitt has packaged casync for Ubuntu. There is also an ArchLinux package. Zbigniew Jędrzejewski-Szmek has prepared a Fedora RPM that hopefully will soon be included in the distribution.

Should you care? Is this a tool for you?

Well, that's up to you really. If you are involved with projects that need to deliver IoT, VM, container, application or OS images, then maybe this is a great tool for you — but other options exist, some of which are linked above.

Note that casync is an Open Source project: if it doesn't do exactly what you need, prepare a patch that adds what you need, and we'll consider it.

If you are interested in the project and would like to talk about this in person, I'll be presenting casync soon at Kinvolk's Linux Technologies Meetup in Berlin, Germany. You are invited. I also intend to talk about it at All Systems Go!, also in Berlin.

All Systems Go! 2017 CfP Open

Posted by Lennart Poettering on June 19, 2017 10:00 PM

<large>The All Systems Go! 2017 Call for Participation is Now Open!</large>

We’d like to invite presentation proposals for All Systems Go! 2017!

All Systems Go! is an Open Source community conference focused on the projects and technologies at the foundation of modern Linux systems — specifically low-level user-space technologies. Its goal is to provide a friendly and collaborative gathering place for individuals and communities working to push these technologies forward.

All Systems Go! 2017 takes place in Berlin, Germany on October 21st+22nd.

All Systems Go! is a 2-day event with 2-3 talks happening in parallel. Full presentation slots are 30-45 minutes in length and lightning talk slots are 5-10 minutes.

We are now accepting submissions for presentation proposals. In particular, we are looking for sessions including, but not limited to, the following topics:

  • Low-level container executors and infrastructure
  • IoT and embedded OS infrastructure
  • OS, container, IoT image delivery and updating
  • Building Linux devices and applications
  • Low-level desktop technologies
  • Networking
  • System and service management
  • Tracing and performance measuring
  • IPC and RPC systems
  • Security and Sandboxing

While our focus is definitely more on the user-space side of things, talks about kernel projects are welcome too, as long as they have a clear and direct relevance for user-space.

Please submit your proposals by September 3rd. Notification of acceptance will be sent out 1-2 weeks later.

To submit your proposal now please visit our CFP submission web site.

For further information about All Systems Go! visit our conference web site.

systemd.conf will not take place this year in lieu of All Systems Go!. All Systems Go! welcomes all projects that contribute to Linux user space, which, of course, includes systemd. Thus, anything you think was appropriate for submission to systemd.conf is also fitting for All Systems Go!

libinput 1.8 switching to git-like helper tool naming "libinput sometool"

Posted by Peter Hutterer on June 19, 2017 01:47 AM

I just released the first release candidate for libinput 1.8. Aside from the build system switch to meson one of the more visible things is that the helper tools have switched from a "libinput-some-tool" to the "libinput some-tool" approach (note the space). This is similar to what git does so it won't take a lot of adjustment for most developers. The actual tools are now hiding in /usr/libexec/libinput. This gives us a lot more flexibility in writing testing and debugging tools and shipping them to the users without cluttering up the default PATH.

There are two potential breakages here, one is that the two existing tools libinput-debug-events and libinput-list-devices have been renamed too. We currently ship compatibility wrappers for those but expect those wrappers to go away with future releases. The second breakage is of lesser impact: typing "man libinput" used to bring up the man page for the xf86-input-libinput driver. Now it brings up the man page for the libinput tool which then points to the man pages of the various features. That's probably a good thing, it puts the documentation a bit closer to the user. For the driver, you now have to type "man 4 libinput" though.

Rawhide sightings

Posted by Matthias Clasen on June 08, 2017 06:31 PM

I haven’t done a blog post about new stuff in GNOME for a while.

Many exciting things are getting advertised by their respective developers anyway, such as Builder or GNOME Todo or gnome-tweak-tool. So here is just a quick note about about a few new things that I am enjoying in GNOME shell in 3.25.

Translucent top bar

The shell top bar was conceived to visually merge with the bezel of the monitor, which is why it has always been mostly black. As many people have pointed out, one downside of this is that it makes the monitor appear smaller, when vertical space is already a scarce commodity. In 3.26, we are trying something new, and make the top bar translucent. To avoid odd visuals, we only do this if the background is actually visible underneath the top bar. In other words, we still have a black bar when there are maximized windows directly touching it.

I have to admit that I was skeptical when we discussed this change: it could be frustrating to move a window up towards that now seemingly available space, only to find the top bar turn solid as you touch it. But in actually using it, it is pleasant, and I like it very much.

Maximize animations

Last cycle, we introduced animations when application windows enter or leave the fullscreen state. In 3.26, we now also animate transition to and from maximized and half-tiled states. A small, but noticable bit of polish!

<video class="wp-video-shortcode" controls="controls" height="267" id="video-1853-1" preload="metadata" width="474"><source src="https://blogs.gnome.org/mclasen/files/2017/06/shell-sightings.webm?_=1" type="video/webm">https://blogs.gnome.org/mclasen/files/2017/06/shell-sightings.webm</video>

If you want to see these things for yourself and don’t want to wait until October, you can try them in Fedora rawhide (which will turn into Fedora 27 in the fall).

More things coming

The GNOME shell team around Florian Müllner has a some more nice things in the pipeline for GNOME 3.26 that are not quite ready for a screen cast yet. A great way to learn about them is to come to GUADEC in  Manchester, July 27 – August 3. See you there!

xf86-input-wacom 0.34 workaround for pressure range bugs

Posted by Peter Hutterer on June 02, 2017 03:10 AM

Back in 2003, the pressure range value for Wacom pen tablets was set to 2048. That's a #define in the driver, but it shouldn't matter because we also advertise this range as part of the device description in the X Input protocol. Clients should be using that advertised min/max range and scale appropriately, in the same way as they should be doing this for the x/y axis ranges.

Fast-forward to 2017 and we changed the pressure range. New Wacom devices now use ~8000 levels, but we opted to just #define it in the driver to 65536 and be done with it. We now scale all models into that range, with varying granularity based on the physical hardware. It shouldn't matter because it's not tied to a reliable physical property anyway and the only thing that matters is the percentage of the max value (which is why libinput just gives you a [0, 1] range. Hindsight is a bliss.).

Slow-forward to 2017-and-a-bit and we received complaints that pressure handling is now broken. Turns out that some applications hardcoded the old 2048 range and now get confused, because virtually any pressure will now hit that maximum. Since those applications are largely proprietary ones and cannot be updated easily, we needed a workaround to this. Jason Gerecke from Wacom got busy and we now have a "Pressure2K" option available in the driver. If set, this option will scale everything into the 2048 range to make sure those applications still work. To get this to work, the following xorg.conf.d snippet is recommended:

Section "InputClass"
Identifier "Wacom pressure compatibility"
MatchDriver "wacom"
Option "Pressure2K" "true"
Put it in a file that sorts higher than the wacom driver itself (e.g. /etc/X11/xorg.conf.d/99-wacom-pressure2k.conf) and restart X. Check the Xorg.log/journal for a "Using 2K pressure levels" message, then verify it works by running xinput list "device name". xinput should show a range of 0 to 2048 on the third valuator.

$> xinput list "Wacom Intuos4 6x9 Pen stylus"
Wacom Intuos4 6x9 Pen stylus id=25 [slave pointer (2)]
Reporting 8 classes:
Class originated from: 25. Type: XIButtonClass
Buttons supported: 9
Button labels: None None None None None None None None None
Button state:
Class originated from: 25. Type: XIKeyClass
Keycodes supported: 248
Class originated from: 25. Type: XIValuatorClass
Detail for Valuator 0:
Label: Abs X
Range: 0.000000 - 44704.000000
Resolution: 200000 units/m
Mode: absolute
Current value: 22340.000000
Class originated from: 25. Type: XIValuatorClass
Detail for Valuator 1:
Label: Abs Y
Range: 0.000000 - 27940.000000
Resolution: 200000 units/m
Mode: absolute
Current value: 13970.000000
Class originated from: 25. Type: XIValuatorClass
Detail for Valuator 2:
Label: Abs Pressure
Range: 0.000000 - 2048.000000
Resolution: 1 units/m
Mode: absolute
Current value: 0.000000

Class originated from: 25. Type: XIValuatorClass
Detail for Valuator 3:
Label: Abs Tilt X
Range: -64.000000 - 63.000000
Resolution: 57 units/m
Mode: absolute
Current value: 0.000000
Class originated from: 25. Type: XIValuatorClass
Detail for Valuator 4:
Label: Abs Tilt Y
Range: -64.000000 - 63.000000
Resolution: 57 units/m
Mode: absolute
Current value: 0.000000
Class originated from: 25. Type: XIValuatorClass
Detail for Valuator 5:
Label: Abs Wheel
Range: -900.000000 - 899.000000
Resolution: 1 units/m
Mode: absolute
Current value: 0.000000

This is an application bug, but this workaround will make sure new versions of the driver can be used until those applications have been fixed. The option will be available in the soon-to-be-released xf86-input-wacom 0.35. The upstream commit is d958ab79d21b57141415650daac88f9369a1c861.

Edit 02/06/2017: wacom devices have 8k pressure levels now.

xinput list shows a "xwayland-pointer" device but not my real devices and what to do about it

Posted by Peter Hutterer on May 23, 2017 12:56 AM

TLDR: If you see devices like "xwayland-pointer" show up in your xinput list output, then you are running under a Wayland compositor and debugging/configuration with xinput will not work.

For many years, the xinput tool has been a useful tool to debug configuration issues (it's not a configuration UI btw). It works by listing the various devices detected by the X server. So a typical output from xinput list under X could look like this:

:: whot@jelly:~> xinput list
⎡ Virtual core pointer id=2 [master pointer (3)]
⎜ ↳ Virtual core XTEST pointer id=4 [slave pointer (2)]
⎜ ↳ SynPS/2 Synaptics TouchPad id=22 [slave pointer (2)]
⎜ ↳ TPPS/2 IBM TrackPoint id=23 [slave pointer (2)]
⎜ ↳ ELAN Touchscreen id=20 [slave pointer (2)]
⎣ Virtual core keyboard id=3 [master keyboard (2)]
↳ Virtual core XTEST keyboard id=5 [slave keyboard (3)]
↳ Power Button id=6 [slave keyboard (3)]
↳ Video Bus id=7 [slave keyboard (3)]
↳ Lid Switch id=8 [slave keyboard (3)]
↳ Sleep Button id=9 [slave keyboard (3)]
↳ ThinkPad Extra Buttons id=24 [slave keyboard (3)]
Alas, xinput is scheduled to go the way of the dodo. More and more systems are running a Wayland session instead of an X session, and xinput just doesn't work there. Here's an example output from xinput list under a Wayland session:

$ xinput list
⎡ Virtual core pointer id=2 [master pointer (3)]
⎜ ↳ Virtual core XTEST pointer id=4 [slave pointer (2)]
⎜ ↳ xwayland-pointer:13 id=6 [slave pointer (2)]
⎜ ↳ xwayland-relative-pointer:13 id=7 [slave pointer (2)]
⎣ Virtual core keyboard id=3 [master keyboard (2)]
↳ Virtual core XTEST keyboard id=5 [slave keyboard (3)]
↳ xwayland-keyboard:13 id=8 [slave keyboard (3)]
As you can see, none of the physical devices are available, the only ones visible are the virtual devices created by XWayland. On a Wayland session, the X server doesn't have access to the physical devices. Instead, it talks via the Wayland protocol to the compositor. This image from the Wayland documentation shows the architecture:
In the above graphic, devices are known to the Wayland compositor (1), but not to the X server. The Wayland protocol doesn't expose physical devices, it merely provides a 'pointer' device, a 'keyboard' device and, where available, a touch and tablet tool/pad devices (2). XWayland wraps these into virtual devices and provides them via the X protocol (3), but they don't represent the physical devices.

This usually doesn't matter, but when it comes to debugging or configuring devices with xinput we run into a few issues. First, configuration via xinput usually means changing driver-specific properties but in the XWayland case there is no driver involved - it's all handled by libinput inside the compositor. Second, debugging via xinput only shows what the wayland protocol sends to XWayland and what XWayland then passes on to the client. For low-level issues with devices, this is all but useless.

The takeaway here is that if you see devices like "xwayland-pointer" show up in your xinput list output, then you are running under a Wayland compositor and debugging with xinput will not work. If you're trying to configure a device, use the compositor's configuration system (e.g. gsettings). If you are debugging a device, use libinput-debug-events. Or compare the behaviour between the Wayland session and the X session to narrow down where the failure point is.

Updating Logitech Hardware on Linux

Posted by Richard Hughes on May 22, 2017 08:41 PM

Just over a year ago Bastille security announced the discovery of a suite of vulnerabilities commonly referred to as MouseJack. The vulnerabilities targeted the low level wireless protocol used by Unifying devices, typically mice and keyboards. The issues included the ability to:

  • Pair new devices with the receiver without user prompting
  • Inject keystrokes, covering various scenarios
  • Inject raw HID commands

This gave an attacker with $15 of hardware the ability to basically take over remote PCs within wireless range, which could be up to 50m away. This makes sitting in a café quite a dangerous thing to do when any affected hardware is inserted, which for the unifying dongle is quite likely as it’s explicitly designed to remain in an empty USB socket. The main manufacturer of these devices is Logitech, but the hardware is also supplied to other OEMs such as Amazon, Microsoft, Lenovo and Dell where they are re-badged or renamed. I don’t think anybody knows the real total, but by my estimations there must be tens of millions of affected-and-unpatched devices being used every day.

Shortly after this announcement, Logitech prepared an update which mitigated some of these problems, and then again a few weeks later prepared another update that worked around and fixed the various issues exploited by the malicious firmware. Officially, Linux isn’t a supported OS by Logitech, so to apply the update you had to start Windows, and download and manually deploy a firmware update. For people running Linux exclusively, like a lot of Red Hat’s customers, the only choice was to stop using the Unifying products or try and find a Windows computer that could be borrowed for doing the update. Some devices are plugged in behind racks of computers forgotten, or even hot-glued into place and unremovable.

The MouseJack team provided a firmware blob that could be deployed onto the dongle itself, and didn’t need extra hardware for programming. Given the cat was now “out of the bag” on how to flash random firmware to this proprietary hardware I asked Logitech if they would provide some official documentation so I could flash the new secure firmware onto the hardware using fwupd. After a few weeks of back-and-forth communication, Logitech released to me a pile of documentation on how to control the bootloader on the various different types of Unifying receiver, and the other peripherals that were affected by the security issues. They even sent me some of the affected hardware, and gave me access to the engineering team that was dealing with this issue.

It took a couple of weeks, but I rewrote the previously-reverse-engineered plugin in fwupd with the new documentation so that it could update the hardware exactly according to the official documentation. This now matches 100% the byte-by-byte packet log compared to the Windows update tool. Magic numbers out, #define’s in. FIXMEs out, detailed comments in. Also, using the documentation means we can report sensible and useful error messages. There were other nuances that were missed in the RE’d plugin (for example, making sure the specified firmware was valid for the hardware revision), and with the blessing of Logitech I merged the branch to master. I then persuaded Logitech to upload the firmware somewhere public, rather than having to extract the firmware out of the .exe files from the Windows update. I then opened up a pull request to add the .metainfo.xml files which allow us to build a .cab package for the Linux Vendor Firmware Service. I created a secure account for Logitech and this allowed them to upload the firmware into a special testing branch.

This is where you come in. If you would like to test this, you first need a version of fwupd that is able to talk to the hardware. For this, you need fwupd-0.9.2-2.fc26 or newer. You can get this from Koji for Fedora.

Then you need to change the DownloadURI in /etc/fwupd.conf to the testing channel. The URI is in the comment in the config file, so no need to list it here. Then reboot, or restart fwupd. Then you can either just launch GNOME Software and click Install, or you can type on the command line fwupdmgr refresh && fwupdmgr update — soon we’ll be able to update more kinds of Logitech hardware.

If this worked, or you had any problems please leave a comment on this blog or send me an email. Thanks should go to Red Hat for letting me work on this for so long, and even more thanks to Logitech to making it possible.

Fractional scaling goes east

Posted by Matthias Clasen on May 19, 2017 06:34 PM

When we introduced HiDPI support in GNOME a few years ago, we took the simplest possible approach that was feasible to implement with the infrastructure we had available at the time.

Some of the limitations:

  • You either get 1:1 or 2:1 scaling, nothing in between
  • The cut-off point that is somewhat arbitrarily chosen and you don’t get a say in it
  • In multi-monitor systems, all monitors share the same scale

Each of these limitations had technical reasons. For example, doing different scales per-monitor is hard to do as long as you are only using a single, big framebuffer for all of them. And allowing scale factors such as 1.5 leads to difficult questions about how to deal with windows that have a size like 640.5×480.5 pixels.

Over the years, we’ve removed the technical obstacles one-by-one, e.g. introduced per-monitor framebuffers. One of the last obstacles was the display configuration API that mutter exposes to the control-center display panel, which was closely modeled on XRANDR, and not suitable for per-monitor and non-integer scales. In the last cycle, we introduced a new, more suitable monitor configuration API, and the necessary support for it has just landed in the display panel.

With this, all of the hurdles have been cleared away, and we are finally ready to get serious about fractional scaling!

Yes, a hackfest!

Jonas and Marco happen to both be in Taipei in early June, so what better to do than to get together and spend some days hacking on fractional scaling support:


If you are a compositor developer (or plan on becoming one), or just generally interested in helping with this work, and are in the area, please check out the date and location by following the link. And, yes, this is a bit last-minute, but we still wanted to give others a chance to participate.

Recently released applications in GNOME Software

Posted by Richard Hughes on May 16, 2017 01:28 PM

By popular request, there is now a list of recently updated applications in the gnome-software overview page.

Upstream applications have to do two things to be featured here:

  1. Have an upstream release within the last 2 months (will be reduced as the number of apps increases)
  2. Have upstream release notes in the AppData file

Quite a few applications from XFCE, GNOME and KDE have already been including <release> tags and this visibility should hopefully encourage other projects to do the same. As a small reminder, the release notes should be small, and easily understandable by end users. You can see lots of examples in the GNOME Software AppData file. Any questions, please just email me or leave comments here. Thanks!

Intel AMT on wireless networks

Posted by Matthew Garrett on May 09, 2017 08:18 PM
More details about Intel's AMT vulnerablity have been released - it's about the worst case scenario, in that it's a total authentication bypass that appears to exist independent of whether the AMT is being used in Small Business or Enterprise modes (more background in my previous post here). One thing I claimed was that even though this was pretty bad it probably wasn't super bad, since Shodan indicated that there were only a small number of thousand machines on the public internet and accessible via AMT. Most deployments were probably behind corporate firewalls, which meant that it was plausibly a vector for spreading within a company but probably wasn't a likely initial vector.

I've since done some more playing and come to the conclusion that it's rather worse than that. AMT actually supports being accessed over wireless networks. Enabling this is a separate option - if you simply provision AMT it won't be accessible over wireless by default, you need to perform additional configuration (although this is as simple as logging into the web UI and turning on the option). Once enabled, there are two cases:
  1. The system is not running an operating system, or the operating system has not taken control of the wireless hardware. In this case AMT will attempt to join any network that it's been explicitly told about. Note that in default configuration, joining a wireless network from the OS is not sufficient for AMT to know about it - there needs to be explicit synchronisation of the network credentials to AMT. Intel provide a wireless manager that does this, but the stock behaviour in Windows (even after you've installed the AMT support drivers) is not to do this.
  2. The system is running an operating system that has taken control of the wireless hardware. In this state, AMT is no longer able to drive the wireless hardware directly and counts on OS support to pass packets on. Under Linux, Intel's wireless drivers do not appear to implement this feature. Under Windows, they do. This does not require any application level support, and uninstalling LMS will not disable this functionality. This also appears to happen at the driver level, which means it bypasses the Windows firewall.
Case 2 is the scary one. If you have a laptop that supports AMT, and if AMT has been provisioned, and if AMT has had wireless support turned on, and if you're running Windows, then connecting your laptop to a public wireless network means that AMT is accessible to anyone else on that network[1]. If it hasn't received a firmware update, they'll be able to do so without needing any valid credentials.

If you're a corporate IT department, and if you have AMT enabled over wifi, turn it off. Now.

[1] Assuming that the network doesn't block client to client traffic, of course

comment count unavailable comments

3000 Reviews on the ODRS

Posted by Richard Hughes on May 08, 2017 09:02 AM

The Open Desktop Ratings service is a simple Flask web service that various software centers use to retrieve and submit application reviews. Today it processed the 3000th review, and I thought I should mark this occasion here. I wanted to give a huge thanks to all the people who have submitted reviews; you have made life easier for people unfamiliar with installing software. There are reviews in over a hundred different languages and over 600 different applications have been reviewed.

Over 4000 people have clicked the “was this useful to you” buttons in the reviews, which affect how the reviews are ordered for a particular system. Without people clicking those buttons we don’t really know how useful a review is. Since we started this project, 37 reviews have been reported for abuse, of which 15 have been deleted for things like swearing and racism.

Here are some interesting graphs, first, showing the number of requests we’re handling per month. As you can see we’re handling nearly a million requests a month.

The second show the number of people contributing reviews. At about 350 per month this is a tiny fraction compared to the people requesting reviews, but this is to be expected.

The third shows where reviews come from; the notable absence is Ubuntu, but they use their own review system rather than the ODRS. Recently Debian has been increasing the fastest, I assume because at last they ship a gnome-software package new enough to support user reviews, but the reviews are still coming in fastest from Fedora users. Maybe Fedora users are the kindest in the open source community? Maybe we just shipped the gnome-software package first? :)

One notable thing missing from the ODRS is a community of people moderating reviews; at the moment it’s just me deciding which reviews are indeed abuse, and also fixing up common spelling errors in the submitted text. If this is something you would like to help with, please let me know and I can spend a bit of time adding a user type somewhere in-between benevolent dictator (me) and unauthenticated. Ideas welcome.

Recipes growing team

Posted by Matthias Clasen on May 05, 2017 06:31 PM

With the big push towards 1.0 now over, the development in GNOME recipes has moved to a more relaxed pace. But that doesn’t mean that nothing is happening! In fact, our team is growing, we will have two interns joining us this cycle, Ekta and Paxana.

While we are waiting for Ekta and Paxana to start working on the big projects for this cycle (sharing and unit conversion),  a number of smaller improvements have landed and will hopefully appear in a development release soon.

More recipes

We were somewhat successful in getting recipe contributions from the GNOME community.

Thanks to everybody who has contributed – keep it coming !

One consequence of this success is that we have too much data to ship with the application – the tarball for 1.0 was bigger than 100MB. To avoid this problem growing even further, the current development release downloads all recipe and image data at runtime, when needed. I’m very interested in feedback about how well that works.

More cuisines

Another consequence is that we now have so many cuisines represented that they don’t fit on one page anymore.

To address this, I’ve added an expander to show more cuisines.

Another improvement around cuisines is that we now offer all the cuisines that we know about to the cuisine combo box when you are editing recipes. A small step towards a user interface that adapts to your use of the application.

Inline editing

One of the findings of our testing session with Jakub and Tuomas at devconf was that creating a recipe was too fiddly, in particular the popover-heavy editing of the ingredients list.

To address this, we are moving to an inline editing approach for the ingredients list. To make this easier, I first refactored the ingredients list to be a separate widget which is now shared between the edit page and the details page (in a read-only mode).

Ekta is helping me with this.

Row reordering

Another outcome of our testing session was that we need to let the user reorder the ingredients list, which was not possible back in January. For 1.0, we added buttons to move a row up or down, but that was more of a stop-gap solution.

What we really want is to reorder rows by drag-and-drop,so I spent a bit of time recently to figure out drag-and-drop support for list boxes.

Temperature conversion

Last, but not least, we also added some preliminary support for unit conversion.

For now, we can display temperatures in Celsius or Fahrenheit. Currently, this gets determined by a setting, but as the next step, we are going to pick this up from the locale.

Paxana is working on this, as a warm-up for her internship project.

how much of the conformance test suite does radv pass now?

Posted by Dave Airlie on May 04, 2017 04:22 AM
Test run totals:
Passed: 109293/150992 (72.4%)
Failed: 0/150992 (0.0%)
Not supported: 41697/150992 (27.6%)
Warnings: 2/150992 (0.0%)

This is effectively a pass. The Not Supported stuff isn't missing features as uneducated people are quick to spout, it's more stuff the hardware doesn't support or is pointless to expose on the hardware. (lots of image formats).

This is the results from the Vulkan CTS 1.0.2 branch, against mesa master with one patch (a workaround for some InternalErrors that CTS throws up).

Do not call the driver conformant as that is against the Khronos rules as we haven't paid or filed for approval, but the driver does now effectively pass the latest conformance test suite. I'll update on things if that changes.

Thanks again to everyone involved.

Intel's remote AMT vulnerablity

Posted by Matthew Garrett on May 01, 2017 10:52 PM
Intel just announced a vulnerability in their Active Management Technology stack. Here's what we know so far.


Intel chipsets for some years have included a Management Engine, a small microprocessor that runs independently of the main CPU and operating system. Various pieces of software run on the ME, ranging from code to handle media DRM to an implementation of a TPM. AMT is another piece of software running on the ME, albeit one that takes advantage of a wide range of ME features.

Active Management Technology

AMT is intended to provide IT departments with a means to manage client systems. When AMT is enabled, any packets sent to the machine's wired network port on port 16992 or 16993 will be redirected to the ME and passed on to AMT - the OS never sees these packets. AMT provides a web UI that allows you to do things like reboot a machine, provide remote install media or even (if the OS is configured appropriately) get a remote console. Access to AMT requires a password - the implication of this vulnerability is that that password can be bypassed.

Remote management

AMT has two types of remote console: emulated serial and full graphical. The emulated serial console requires only that the operating system run a console on that serial port, while the graphical environment requires drivers on the OS side requires that the OS set a compatible video mode but is also otherwise OS-independent[2]. However, an attacker who enables emulated serial support may be able to use that to configure grub to enable serial console. Remote graphical console seems to be problematic under Linux but some people claim to have it working, so an attacker would be able to interact with your graphical console as if you were physically present. Yes, this is terrifying.

Remote media

AMT supports providing an ISO remotely. In older versions of AMT (before 11.0) this was in the form of an emulated IDE controller. In 11.0 and later, this takes the form of an emulated USB device. The nice thing about the latter is that any image provided that way will probably be automounted if there's a logged in user, which probably means it's possible to use a malformed filesystem to get arbitrary code execution in the kernel. Fun!

The other part of the remote media is that systems will happily boot off it. An attacker can reboot a system into their own OS and examine drive contents at their leisure. This doesn't let them bypass disk encryption in a straightforward way[1], so you should probably enable that.

How bad is this

That depends. Unless you've explicitly enabled AMT at any point, you're probably fine. The drivers that allow local users to provision the system would require administrative rights to install, so as long as you don't have them installed then the only local users who can do anything are the ones who are admins anyway. If you do have it enabled, though…

How do I know if I have it enabled?

Yeah this is way more annoying than it should be. First of all, does your system even support AMT? AMT requires a few things:

1) A supported CPU
2) A supported chipset
3) Supported network hardware
4) The ME firmware to contain the AMT firmware

Merely having a "vPRO" CPU and chipset isn't sufficient - your system vendor also needs to have licensed the AMT code. Under Linux, if lspci doesn't show a communication controller with "MEI" or "HECI" in the description, AMT isn't running and you're safe. If it does show an MEI controller, that still doesn't mean you're vulnerable - AMT may still not be provisioned. If you reboot you should see a brief firmware splash mentioning the ME. Hitting ctrl+p at this point should get you into a menu which should let you disable AMT.

How about over Wifi?

Turning on AMT doesn't automatically turn it on for wifi. AMT will also only connect itself to networks it's been explicitly told about. Where things get more confusing is that once the OS is running, responsibility for wifi is switched from the ME to the OS and it forwards packets to AMT. I haven't been able to find good documentation on whether having AMT enabled for wifi results in the OS forwarding packets to AMT on all wifi networks or only ones that are explicitly configured.

What do we not know?

We have zero information about the vulnerability, other than that it allows unauthenticated access to AMT. One big thing that's not clear at the moment is whether this affects all AMT setups, setups that are in Small Business Mode, or setups that are in Enterprise Mode. If the latter, the impact on individual end-users will be basically zero - Enterprise Mode involves a bunch of effort to configure and nobody's doing that for their home systems. If it affects all systems, or just systems in Small Business Mode, things are likely to be worse.
We now know that the vulnerability exists in all configurations.

What should I do?

Make sure AMT is disabled. If it's your own computer, you should then have nothing else to worry about. If you're a Windows admin with untrusted users, you should also disable or uninstall LMS by following these instructions.

Does this mean every Intel system built since 2008 can be taken over by hackers?

No. Most Intel systems don't ship with AMT. Most Intel systems with AMT don't have it turned on.

Does this allow persistent compromise of the system?

Not in any novel way. An attacker could disable Secure Boot and install a backdoored bootloader, just as they could with physical access.

But isn't the ME a giant backdoor with arbitrary access to RAM?

Yes, but there's no indication that this vulnerability allows execution of arbitrary code on the ME - it looks like it's just (ha ha) an authentication bypass for AMT.

Is this a big deal anyway?

Yes. Fixing this requires a system firmware update in order to provide new ME firmware (including an updated copy of the AMT code). Many of the affected machines are no longer receiving firmware updates from their manufacturers, and so will probably never get a fix. Anyone who ever enables AMT on one of these devices will be vulnerable. That's ignoring the fact that firmware updates are rarely flagged as security critical (they don't generally come via Windows update), so even when updates are made available, users probably won't know about them or install them.

Avoiding this kind of thing in future

Users ought to have full control over what's running on their systems, including the ME. If a vendor is no longer providing updates then it should at least be possible for a sufficiently desperate user to pay someone else to do a firmware build with the appropriate fixes. Leaving firmware updates at the whims of hardware manufacturers who will only support systems for a fraction of their useful lifespan is inevitably going to end badly.

How certain are you about any of this?

Not hugely - the quality of public documentation on AMT isn't wonderful, and while I've spent some time playing with it (and related technologies) I'm not an expert. If anything above seems inaccurate, let me know and I'll fix it.

[1] Eh well. They could reboot into their own OS, modify your initramfs (because that's not signed even if you're using UEFI Secure Boot) such that it writes a copy of your disk passphrase to /boot before unlocking it, wait for you to type in your passphrase, reboot again and gain access. Sealing the encryption key to the TPM would avoid this.

[2] Updated after this comment - I thought I'd fixed this before publishing but left that claim in by accident.

(Updated to add the section on wifi)

(Updated to typo replace LSM with LMS)

(Updated to indicate that the vulnerability affects all configurations)

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Looking at the Netgear Arlo home IP camera

Posted by Matthew Garrett on April 30, 2017 05:09 AM
Another in the series of looking at the security of IoT type objects. This time I've gone for the Arlo network connected cameras produced by Netgear, specifically the stock Arlo base system with a single camera. The base station is based on a Broadcom 5358 SoC with an 802.11n radio, along with a single Broadcom gigabit ethernet interface. Other than it only having a single ethernet port, this looks pretty much like a standard Netgear router. There's a convenient unpopulated header on the board that turns out to be a serial console, so getting a shell is only a few minutes work.

Normal setup is straight forward. You plug the base station into a router, wait for all the lights to come on and then you visit arlo.netgear.com and follow the setup instructions - by this point the base station has connected to Netgear's cloud service and you're just associating it to your account. Security here is straightforward: you need to be coming from the same IP address as the Arlo. For most home users with NAT this works fine. I sat frustrated as it repeatedly failed to find any devices, before finally moving everything behind a backup router (my main network isn't NATted) for initial setup. Once you and the Arlo are on the same IP address, the site shows you the base station's serial number for confirmation and then you attach it to your account. Next step is adding cameras. Each base station is broadcasting an 802.11 network on the 2.4GHz spectrum. You connect a camera by pressing the sync button on the base station and then the sync button on the camera. The camera associates with the base station via WPS and now you're up and running.

This is the point where I get bored and stop following instructions, but if you're using a desktop browser (rather than using the mobile app) you appear to need Flash in order to actually see any of the camera footage. Bleah.

But back to the device itself. The first thing I traced was the initial device association. What I found was that once the device is associated with an account, it can't be attached to another account. This is good - I can't simply request that devices be rebound to my account from someone else's. Further, while the serial number is displayed to the user to disambiguate between devices, it doesn't seem to be what's used internally. Tracing the logon traffic from the base station shows it sending a long random device ID along with an authentication token. If you perform a factory reset, these values are regenerated. The device to account mapping seems to be based on this random device ID, which means that once the device is reset and bound to another account there's no way for the initial account owner to regain access (other than resetting it again and binding it back to their account). This is far better than many devices I've looked at.

Performing a factory reset also changes the WPA PSK for the camera network. Newsky Security discovered that doing so originally reset it to 12345678, which is, uh, suboptimal? That's been fixed in newer firmware, along with their discovery that the original random password choice was not terribly random.

All communication from the base station to the cloud seems to be over SSL, and everything validates certificates properly. This also seems to be true for client communication with the cloud service - camera footage is streamed back over port 443 as well.

Most of the functionality of the base station is provided by two daemons, xagent and vzdaemon. xagent appears to be responsible for registering the device with the cloud service, while vzdaemon handles the camera side of things (including motion detection). All of this is running as root, so in the event of any kind of vulnerability the entire platform is owned. For such a single purpose device this isn't really a big deal (the only sensitive data it has is the camera feed - if someone has access to that then root doesn't really buy them anything else). They're statically linked and stripped so I couldn't be bothered spending any significant amount of time digging into them. In any case, they don't expose any remotely accessible ports and only connect to services with verified SSL certificates. They're probably not a big risk.

Other than the dependence on Flash, there's nothing immediately concerning here. What is a little worrying is a family of daemons running on the device and listening to various high numbered UDP ports. These appear to be provided by Broadcom and a standard part of all their router platforms - they're intended for handling various bits of wireless authentication. It's not clear why they're listening on rather than, and it's not obvious whether they're vulnerable (they mostly appear to receive packets from the driver itself, process them and then stick packets back into the kernel so who knows what's actually going on), but since you can't set one of these devices up in the first place without it being behind a NAT gateway it's unlikely to be of real concern to most users. On the other hand, the same daemons seem to be present on several Broadcom-based router platforms where they may end up being visible to the outside world. That's probably investigation for another day, though.

Overall: pretty solid, frustrating to set up if your network doesn't match their expectations, wouldn't have grave concerns over having it on an appropriately firewalled network.

(Edited to replace a mistaken reference to WDS with WPS)

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LibreOffice in The Matrix [m]

Posted by Eike Rathke on April 25, 2017 08:45 PM
If you use the Riot App (or any other) to connect to the Matrix and communicate, there's now a LibreOffice room that is bridged with the #libreoffice IRC channel on freenode.net. IRC channels are bridged to the matrix already for some time, but so far you had to type
/join #freenode_#libreoffice:matrix.org
in your matrix mobile app, or in the browser app know the bridge exists and select from the list, now you can just search in the available matrix rooms for LibreOffice and join. This should be a convenient method to join a chat with other LibreOffice users for people who otherwise don't use IRC or don't want to install an IRC app just for this on their mobile, smartphone, tablet..

The #libreoffice IRC channel and thus the LibreOffice matrix room is dedicated to user questions around all LibreOffice applications. Join and enjoy, get help and help others.

Reverse engineering ComputerHardwareIds.exe with winedbg

Posted by Richard Hughes on April 25, 2017 07:49 PM

In an ideal world vendors could use the same GUID value for hardware matching in Windows and Linux firmware. When installing firmware and drivers in Windows vendors can always use some generated HardwareID GUIDs that match useful things like the BIOS vendor and the product SKU. It would make sense to use the same scheme as Microsoft. There are a few issues in an otherwise simple plan.

The first, solved with a simple kernel patch I wrote (awaiting review by Jean Delvare), exposes a few more SMBIOS fields into /sys/class/dmi/id that are required for the GUID calculation.

The second problem is a little more tricky. We don’t actually know how Microsoft joins the strings, what encoding is used, or more importantly the secret namespace UUID used to seed the GUID. The only thing we have got is the closed source ComputerHardwareIds.exe program in the Windows DDK. This, luckily, runs in Wine although Wine isn’t able to get the system firmware data itself. This can be worked around, and actually makes testing easier.

So, some research. All we know from the MSDN page is that Each hardware ID string is converted into a GUID by using the SHA-1 hashing algorithm which actually tells us quite a bit. Generating a GUID from a SHA-1 hash means this has to be a type 5 UUID.

The reference code for a type-5 UUID is helpfully available in the IETF RFC document so it’s quite quick to get started with research. From a few minutes of searching online, the most likely symbols the program will be using are the BCrypt* set of functions. From the RFC code, we call the checksum generation update function with first the encoded namespace (aha!) and then the encoded joined string (ahaha!). For Win32 programs, BCryptHashData is the function we want to trace.

So, to check:

wine /home/hughsie/ComputerHardwareIds.exe /mfg "To be filled by O.E.M."

…matches the reference HardwareID-14 output from Microsoft. So onto debugging, using +relay shows all the calling values and return values from each Win32 exported symbol:

WINEDEBUG=+relay winedbg --gdb ~/ComputerHardwareIds.exe
Wine-gdb> b BCryptHashData
Wine-gdb> r ~/ComputerHardwareIds.exe /mfg "To be filled by O.E.M." /family "To be filled by O.E.M."
005b:Call bcrypt.BCryptHashData(0011bab8,0033fcf4,00000010,00000000) ret=0100699d
Breakpoint 1, 0x7ffd85f8 in BCryptHashData () from /lib/wine/bcrypt.dll.so

Great, so this is the secret namespace. The first parameter is the context, the second is the data address, the third is the length (0x10 as a length is indeed SHA-1) and the forth is the flags — so lets print out the data so we can see what it is:

Wine-gdb> x/16xb 0x0033fcf4
0x33fcf4:	0x70	0xff	0xd8	0x12	0x4c	0x7f	0x4c	0x7d
0x33fcfc:	0x00	0x00	0x00	0x00	0x00	0x00	0x00	0x00

Using either the uuid in python, or uuid_unparse in libuuid, we can format the namespace to 70ffd812-4c7f-4c7d-0000-000000000000 — now this doesn’t look like a randomly generated UUID to me! Onto the next thing, the encoding and joining policy:

Wine-gdb> c
005f:Call bcrypt.BCryptHashData(0011bb90,00341458,0000005a,00000000) ret=010069b3
Breakpoint 1, 0x7ffd85f8 in BCryptHashData () from /lib/wine/bcrypt.dll.so
Wine-gdb> x/90xb 0x00341458
0x341458:	0x54	0x00	0x6f	0x00	0x20	0x00	0x62	0x00
0x341460:	0x65	0x00	0x20	0x00	0x66	0x00	0x69	0x00
0x341468:	0x6c	0x00	0x6c	0x00	0x65	0x00	0x64	0x00
0x341470:	0x20	0x00	0x62	0x00	0x79	0x00	0x20	0x00
0x341478:	0x4f	0x00	0x2e	0x00	0x45	0x00	0x2e	0x00
0x341480:	0x4d	0x00	0x2e	0x00	0x26	0x00	0x54	0x00
0x341488:	0x6f	0x00	0x20	0x00	0x62	0x00	0x65	0x00
0x341490:	0x20	0x00	0x66	0x00	0x69	0x00	0x6c	0x00
0x341498:	0x6c	0x00	0x65	0x00	0x64	0x00	0x20	0x00
0x3414a0:	0x62	0x00	0x79	0x00	0x20	0x00	0x4f	0x00
0x3414a8:	0x2e	0x00	0x45	0x00	0x2e	0x00	0x4d	0x00
0x3414b0:	0x2e	0x00
Wine-gdb> q

So there we go. The encoding looks like UTF-16 (as expected, much of the Windows API is this way) and the joining character seems to be &.

I’ve written some code in fwupd so that this happens:

$ fwupdmgr hwids
Computer Information
BiosVendor: LENOVO
BiosVersion: GJET75WW (2.25 )
Manufacturer: LENOVO
Family: ThinkPad T440s
ProductName: 20ARS19C0C
ProductSku: LENOVO_MT_20AR_BU_Think_FM_ThinkPad T440s
EnclosureKind: 10
BaseboardManufacturer: LENOVO
BaseboardProduct: 20ARS19C0C

Hardware IDs
{c4159f74-3d2c-526f-b6d1-fe24a2fbc881}   <- Manufacturer + Family + ProductName + ProductSku + BiosVendor + BiosVersion + BiosMajorRelease + BiosMinorRelease
{ff66cb74-5f5d-5669-875a-8a8f97be22c1}   <- Manufacturer + Family + ProductName + BiosVendor + BiosVersion + BiosMajorRelease + BiosMinorRelease
{2e4dad4e-27a0-5de0-8e92-f395fc3fa5ba}   <- Manufacturer + ProductName + BiosVendor + BiosVersion + BiosMajorRelease + BiosMinorRelease
{3faec92a-3ae3-5744-be88-495e90a7d541}   <- Manufacturer + Family + ProductName + ProductSku + BaseboardManufacturer + BaseboardProduct
{660ccba8-1b78-5a33-80e6-9fb8354ee873}   <- Manufacturer + Family + ProductName + ProductSku
{8dc9b7c5-f5d5-5850-9ab3-bd6f0549d814}   <- Manufacturer + Family + ProductName
{178cd22d-ad9f-562d-ae0a-34009822cdbe}   <- Manufacturer + ProductSku + BaseboardManufacturer + BaseboardProduct
{da1da9b6-62f5-5f22-8aaa-14db7eeda2a4}   <- Manufacturer + ProductSku
{059eb22d-6dc7-59af-abd3-94bbe017f67c}   <- Manufacturer + ProductName + BaseboardManufacturer + BaseboardProduct
{0cf8618d-9eff-537c-9f35-46861406eb9c}   <- Manufacturer + ProductName
{f4275c1f-6130-5191-845c-3426247eb6a1}   <- Manufacturer + Family + BaseboardManufacturer + BaseboardProduct
{db73af4c-4612-50f7-b8a7-787cf4871847}   <- Manufacturer + Family
{5e820764-888e-529d-a6f9-dfd12bacb160}   <- Manufacturer + EnclosureKind
{f8e1de5f-b68c-5f52-9d1a-f1ba52f1f773}   <- Manufacturer + BaseboardManufacturer + BaseboardProduct
{6de5d951-d755-576b-bd09-c5cf66b27234}   <- Manufacturer

Which basically matches the output of ComputerHardwareIds.exe on the same hardware. If the kernel patch gets into the next release I’ll merge the fwupd branch to master and allow vendors to start using the Microsoft HardwareID GUID values.

Meson considerations

Posted by Matthias Clasen on April 20, 2017 08:38 PM

A post with my GNOME release team hat on…

Meson is new and cool

A number of GNOME modules are switching to meson for 3.26. I myself was an early adopter for this: recipes has had meson build support since the beginning of the year, and after the 1.0 release, I’ve dropped autotools support on the master branch.

autotools are of course very familiar to most of us, and we know how to get most things done there. But it often isn’t pretty, and  using meson feels like a breath of fresh air. Others have been praising meson for its simplicity, ease of use and speed, so I am not going repeat that here.

Supported tools

jhbuild is our traditional build support tool, and it has well-working meson support for a while now. GNOME builder and flatpak-builder also both support meson and we include meson in the GNOME sdk for 3.24.

So, for developers, meson support is more or less there, and working well.

Transition woes

So, things are pretty awesome all around: we have a new build system, it is shiny and fast and supported. Sounds too good to be true. Whats the catch ?

One thing that meson does not do is building traditional ‘make dist’ style tarballs. The premise is that you can just build your software from a git tag or from a snapshot produced by git-archive.

While that is true, and maybe a direction we want to be going in for the future, there are plenty of build systems out there that expect you to provide a tarball or similar archive. That is true for Fedora’s koji, and it is also true for form in which we currently produce GNOME releases.

A GNOME release is essentially defined by a jhbuild module file (several of them, in fact) which refers to release tarballs for all of our modules, including checksums and sizes.  For core GNOME modules, these tarballs are generally put in place using a tool called ftpadmin. As I’ve recently found out, ftpadmin is a little picky. It expects the content in the tarball to be in a directory that’s named in module-version style and will error out if that is not the case.

Thankfully, git archive is up to the task. Here is what I did to produce a recent gnome-recipes release:

git tag -m 1.2.0 1.2.0
git archive --prefix gnome-recipes-1.2.0/ \
            -o gnome-recipes-1.2.0.tar.xz \

Some unsolved problems remain. For example, we have not decided on how to handle library documentation in the new meson world. The way this works with autotools is that the tarballs include generated docs, which get extracted and post-processed by some scripts before they end up on developer.gnome.org. But git archive snapshots contain no generated documentation…  So far, no library that we host documentation for has made the jump to meson-only builds, so we still have some time to come up with a different solution.

Overall, I am really excited that we are embracing meson!

Update: My discussion of archives failed to consider git submodules. git-archive does not handle those, so my recommendation will not produce a working snapshot if you use submodules. See nautilus’ make_release.sh script for how to handle that.

Mailing list for fwupd and the LVFS

Posted by Richard Hughes on April 13, 2017 08:56 AM

I’ve created a mailing list for fwupd and LVFS discussions. If you’re interested in firmware updating on Linux, or want to know what’s happening on the Linux Vendor Firmware Service you probably want to join. There are a few interesting things I’ll post in a few days.

Disabling SSL validation in binary apps

Posted by Matthew Garrett on April 11, 2017 10:27 PM
Reverse engineering protocols is a great deal easier when they're not encrypted. Thankfully most apps I've dealt with have been doing something convenient like using AES with a key embedded in the app, but others use remote protocols over HTTPS and that makes things much less straightforward. MITMProxy will solve this, as long as you're able to get the app to trust its certificate, but if there's a built-in pinned certificate that's going to be a pain. So, given an app written in C running on an embedded device, and without an easy way to inject new certificates into that device, what do you do?

First: The app is probably using libcurl, because it's free, works and is under a license that allows you to link it into proprietary apps. This is also bad news, because libcurl defaults to having sensible security settings. In the worst case we've got a statically linked binary with all the symbols stripped out, so we're left with the problem of (a) finding the relevant code and (b) replacing it with modified code. Fortuntely, this is much less difficult than you might imagine.

First, let's find where curl sets up its defaults. Curl_init_userdefined() in curl/lib/url.c has the following code:
set->ssl.primary.verifypeer = TRUE;
set->ssl.primary.verifyhost = TRUE;
#ifdef USE_TLS_SRP
set->ssl.authtype = CURL_TLSAUTH_NONE;
set->ssh_auth_types = CURLSSH_AUTH_DEFAULT; /* defaults to any auth
type */
set->general_ssl.sessionid = TRUE; /* session ID caching enabled by
default */
set->proxy_ssl = set->ssl;

set->new_file_perms = 0644; /* Default permissions */
set->new_directory_perms = 0755; /* Default permissions */

TRUE is defined as 1, so we want to change the code that currently sets verifypeer and verifyhost to 1 to instead set them to 0. How to find it? Look further down - new_file_perms is set to 0644 and new_directory_perms is set to 0755. The leading 0 indicates octal, so these correspond to decimal 420 and 493. Passing the file to objdump -d (assuming a build of objdump that supports this architecture) will give us a disassembled version of the code, so time to fix our problems with grep:
objdump -d target | grep --after=20 ,420 | grep ,493

This gives us the disassembly of target, searches for any occurrence of ",420" (indicating that 420 is being used as an argument in an instruction), prints the following 20 lines and then searches for a reference to 493. It spits out a single hit:
43e864: 240301ed li v1,493
Which is promising. Looking at the surrounding code gives:
43e820: 24030001 li v1,1
43e824: a0430138 sb v1,312(v0)
43e828: 8fc20018 lw v0,24(s8)
43e82c: 24030001 li v1,1
43e830: a0430139 sb v1,313(v0)
43e834: 8fc20018 lw v0,24(s8)
43e838: ac400170 sw zero,368(v0)
43e83c: 8fc20018 lw v0,24(s8)
43e840: 2403ffff li v1,-1
43e844: ac4301dc sw v1,476(v0)
43e848: 8fc20018 lw v0,24(s8)
43e84c: 24030001 li v1,1
43e850: a0430164 sb v1,356(v0)
43e854: 8fc20018 lw v0,24(s8)
43e858: 240301a4 li v1,420
43e85c: ac4301e4 sw v1,484(v0)
43e860: 8fc20018 lw v0,24(s8)
43e864: 240301ed li v1,493
43e868: ac4301e8 sw v1,488(v0)

Towards the end we can see 493 being loaded into v1, and v1 then being copied into an offset from v0. This looks like a structure member being set to 493, which is what we expected. Above that we see the same thing being done to 420. Further up we have some more stuff being set, including a -1 - that corresponds to CURLSSH_AUTH_DEFAULT, so we seem to be in the right place. There's a zero above that, which corresponds to CURL_TLSAUTH_NONE. That means that the two 1 operations above the -1 are the code we want, and simply changing 43e820 and 43e82c to 24030000 instead of 24030001 means that our targets will be set to 0 (ie, FALSE) rather than 1 (ie, TRUE). Copy the modified binary back to the device, run it and now it happily talks to MITMProxy. Huge success.

(If the app calls Curl_setopt() to reconfigure the state of these values, you'll need to stub those out as well - thankfully, recent versions of curl include a convenient string "CURLOPT_SSL_VERIFYHOST no longer supports 1 as value!" in this function, so if the code in question is using semi-recent curl it's easy to find. Then it's just a matter of looking for the constants that CURLOPT_SSL_VERIFYHOST and CURLOPT_SSL_VERIFYPEER are set to, following the jumps and hacking the code to always set them to 0 regardless of the argument)

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A quick look at the Ikea Trådfri lighting platform

Posted by Matthew Garrett on April 09, 2017 12:16 AM
Ikea recently launched their Trådfri smart lighting platform in the US. The idea of Ikea plus internet security together at last seems like a pretty terrible one, but having taken a look it's surprisingly competent. Hardware-wise, the device is pretty minimal - it seems to be based on the Cypress[1] WICED IoT platform, with 100MBit ethernet and a Silicon Labs Zigbee chipset. It's running the Express Logic ThreadX RTOS, has no running services on any TCP ports and appears to listen on two single UDP ports. As IoT devices go, it's pleasingly minimal.

That single port seems to be a COAP server running with DTLS and a pre-shared key that's printed on the bottom of the device. When you start the app for the first time it prompts you to scan a QR code that's just a machine-readable version of that key. The Android app has code for using the insecure COAP port rather than the encrypted one, but the device doesn't respond to queries there so it's presumably disabled in release builds. It's also local only, with no cloud support. You can program timers, but they run on the device. The only other service it seems to run is an mdns responder, which responds to the _coap._udp.local query to allow for discovery.

From a security perspective, this is pretty close to ideal. Having no remote APIs means that security is limited to what's exposed locally. The local traffic is all encrypted. You can only authenticate with the device if you have physical access to read the (decently long) key off the bottom. I haven't checked whether the DTLS server is actually well-implemented, but it doesn't seem to respond unless you authenticate first which probably covers off a lot of potential risks. The SoC has wireless support, but it seems to be disabled - there's no antenna on board and no mechanism for configuring it.

However, there's one minor issue. On boot the device grabs the current time from pool.ntp.org (fine) but also hits http://fw.ota.homesmart.ikea.net/feed/version_info.json . That file contains a bunch of links to firmware updates, all of which are also downloaded over http (and not https). The firmware images themselves appear to be signed, but downloading untrusted objects and then parsing them isn't ideal. Realistically, this is only a problem if someone already has enough control over your network to mess with your DNS, and being wired-only makes this pretty unlikely. I'd be surprised if it's ever used as a real avenue of attack.

Overall: as far as design goes, this is one of the most secure IoT-style devices I've looked at. I haven't examined the COAP stack in detail to figure out whether it has any exploitable bugs, but the attack surface is pretty much as minimal as it could be while still retaining any functionality at all. I'm impressed.

[1] Formerly Broadcom

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inputfd - a protocol for direct access to input devices in wayland

Posted by Peter Hutterer on April 01, 2017 06:12 AM

This is a higher-level explanation of the inputfd protocol RFC I sent to the list on March 31. Note that this is a first draft, this protocol may never see the light of the day or may be significantly altered before it lands.

First, what is it? inputfd is a protocol for a Wayland compositor to pass a file descriptor (fd) for an input device directly to the client. The client can then read events off this fd and process them, without any additional buffering in between. In the ideal case, the compositor doesn't care (or even notice) that events are flowing between the kernel and the client. Because the compositor sets up the fd, the client does not need any special privileges.

Why is this needed? There are a few input devices that will not be handled by libinput. libinput is the stack for those devices that have a direct interaction with the desktop - mice, keyboards, touchpads, ... But plenty of devices do not want or require desktop interactions. Joysticks/gamepads are the prime example here, but 3D mice or VR input devices also come to mind. These devices don't control the cursor on the desktop, so the compositor doesn't care about the device's events. Note that the current draft only caters for joysticks, 3D mice etc. are TBD.

Why not handle these devices in libinput? Joysticks in particular are so varied that a library like libinput would have to increase the API surface area massively to cater for every possibility. And in the end it is likely that libinput would merely buffer events and pass them on almost as-is anyway. From a maintenance POV - I don't want to deal with that. And from a technical POV - there's little point to have libinput in between anyway. Furthermore, it's already the case that gaming devices are opened directly by the application rather than going through X. So just connecting the clients with the device directly has a advantages.

What does the compositor do? The compositor has two jobs: device filtering and focus management. In the current draft, a client can say "give me all gaming devices" but it's the compositor that decides which device is classified as such (see below for details). Depending on seat assignment or other policies, a client may only see a fraction of the devices currently connected.

Focus management is relatively trivial: the compositor decides that a client has focus now (e.g. by clicking into the window) and hands that client an fd. On focus out (e.g. alt-tab) the fd is revoked and the client cannot read any more events. Rinse, wash, repeat as the focus changes. Note that the protocol does not define how the focus is decided, that task is up to the compositor. Having focus management in the compositor gives us a simple benefit: the client can't hog the device or read events when it's out of focus. This makes it easy to have multiple clients running that need access to the same device without messing up state in a backgrounded client. The security benefit is minimal, few people enter their password with a joystick. But it's still a warm fuzzy feeling to know that a client cannot read events when it's not supposed to.

What devices are applicable devices? This is one of the TBD of the protocol. The compositor needs to know whether a device is a gaming device or not, but the default udev tag ID_INPUT_JOYSTICK is too crude and provides false positives (e.g. some Wacom tablets have that tag set). The conversion currently goes towards having a database that can define this better, but this point is far from decided on.

There are a couple of other points that are still being discussed. If you have knowledge in game (framework) development, do join the discussion, we need input. Personally I am far from a game developer, so I cannot fathom all the weird corner cases we may have to deal with here. Flying blind while designing a protocol is fun, but not so much when you then have to maintain it for the next 10 years. So some navigational input would be helpful.

And just to make sure you join the right discussion, I've disabled comments here :)

GTK+ happenings

Posted by Matthias Clasen on March 31, 2017 08:10 PM

This will be a longer post summarizing some of the discussions and decisions at the recent GTK+ hackfest in London.

I’ve just released GTK+ 3.90, as a milestone on our way towards GTK+ 4. This post should explain not just what is or isn’t in that release, but also where we are on the journey towards GTK+ 4, and what changes are still in the pipeline.

The reason for doing a 3.90 release now and not just another 3.89.x milestone is that we want to encourage experimental ports of some GTK+ 3 applications at this point, to gather feedback.

If you want to do this for your application, you should be aware that we are not promising more than 6 month API stability yet. There are still a number of unfinished transitions and fundamental changes (such as dropping subwindows, or moving container APIs to GtkWidget) that can and will affect application APIs before GTK+ 4.

I am willing to do a few 3.90.x snapshots if there is interest, but you should also be prepared to keep your application building against GTK+ 3, since 3.90 may not be widely available in distributions.

Hackfest happenings

We had a 3 productive days in London last week. The hackfest was a bit different from previous GTK+ get-togethers since we had a bigger and more diverse audience, which means that we had less down-in-the-details discussion about GTK+ internals.

Instead, some of us spent time discussion portals, Flatpak, build services and other things – but I will focus on the GTK+ parts in this post.

The GTK+ discussion was sometimes a bit higher-level, with topics like graphics pipelines and how we use them in GSK, or constraints and how they can fit into the GTK+ layout machinery.

I’ve personally enjoyed this change of pace quite a bit, and hope we can repeat this style of event in the future.

The details: GSK

We spent a while reviewing how far we have come with rebasing the GTK+ rendering onto GSK (and thus, GL / Vulkan). I won’t go into excessive details here, but we have both a Vulkan and a GL renderer for GSK.

The Vulkan renderer has shader implementations for many of the performance-relevant elements of CSS that make up GTK+ widgets. One major omission is that we still don’t handle text natively and fall back to cairo rendering and texture upload for it. We decided to look at cogl-pango and lift the necessary texture atlas and pango renderer from there, as far as possible.

The GL renderer is much less complete, since Benjamin has focused on implementing things on the Vulkan side at first. The plan here is to finish the Vulkan side first and then port things over to GL. One difference between the backends that we discussed at some length is that while changing pipelines is cheap with Vulkan, that may not be the case on the GL side, so we may need an optimizing pass over the render node tree to minimize state changes.

The details: constraints

Emmanuele gave a demo of Emeus, which is his implementation of constraints-based layout for GTK+. This demo left me feeling quite positive – everybody seems to be moving in the direction of constraints-based layout.

Emeus also supports Apple’s shorthand notation for constraints, so it should be familiar to many people who don’t have experience with GTK+’s nested boxes model. If we can integrate this in time for GTK+ 4, it could make a real difference for how GTK+ applications are designed and implemented.

In the discussion after the demo, we touched on questions of how we could possibly reimplement existing GTK+ containers in terms of constraints, and how we can take even more advantage of constraints by making Emeus composable.

Of course, there are questions of how far this approach will scale – could you put all of gtk-widget-factory into a single system of constraints and solve it while resizing the window ? We will find out…

The details: input

One of the reasons why we are moving to GL-based rendering is that we want to enable more pervasive animations in many places. One example that we’ve discussed is animating the showing and hiding of list or grid elements in a filtered list box or flow box. Doing this smoothly at 60 frames per second requires that we can move and transform elements without causing full relayouts, which in turn means that we to separate positions from sizes, which is only practical in a world without subwindows.

Therefore, one of the milestones on our journey towards GTK+ 4 is to move event handling away from using subwindows for routing input events to their target. Once we have taken this step, it will also be possible to take transformations into account.

Carlos just posted a branch that is taking the first steps in this direction.

The details: children, nodes and gadgets

I’ve already talked about Emeus and constraints, so I won’t repeat that here. But there are some other changes in the way GTK+ widgets work that are worth mentioning here.

We are moving away from GtkContainer as the parent class for container. Instead we now allow any widget to have children. The APIs for this are more DOM-like than GtkContainer: gtk_widget_get_first_child, gtk_widget_get_last_child, gtk_widget_get_next_sibling, gtk_widget_get_prev_sibling.

In GTK+ 3.20 and afterwards, we introduced gadgets as internal construct that allowed us to clean up our widget’s adherence to the CSS box model. This was always meant as a stop-gap solution for pre-existing widgets that were just too complicated to fit the CSS box model well. Now that any widget can have children, we have begun to replace some of these gadgets with regular widgets.

For example, GtkSwitch now has three child widgets: the slider and two labels.


We’ve had a successful hackfest and GTK+ 4 development is on track, with 3.90 as a visible milestone. Try it out!

Announcing the Shim review process

Posted by Matthew Garrett on March 21, 2017 08:29 PM
Shim has been hugely successful, to the point of being used by the majority of significant Linux distributions and many other third party products (even, apparently, Solaris). The aim was to ensure that it would remain possible to install free operating systems on UEFI Secure Boot platforms while still allowing machine owners to replace their bootloaders and kernels, and it's achieved this goal.

However, a legitimate criticism has been that there's very little transparency in Microsoft's signing process. Some people have waited for significant periods of time before being receiving a response. A large part of this is simply that demand has been greater than expected, and Microsoft aren't in the best position to review code that they didn't write in the first place.

To that end, we're adopting a new model. A mailing list has been created at shim-review@lists.freedesktop.org, and members of this list will review submissions and provide a recommendation to Microsoft on whether these should be signed or not. The current set of expectations around binaries to be signed documented here and the current process here - it is expected that this will evolve slightly as we get used to the process, and we'll provide a more formal set of documentation once things have settled down.

This is a new initiative and one that will probably take a little while to get working smoothly, but we hope it'll make it much easier to get signed releases of Shim out without compromising security in the process.

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Buying a Utah teapot

Posted by Matthew Garrett on March 20, 2017 08:45 PM
The Utah teapot was one of the early 3D reference objects. It's canonically a Melitta but hasn't been part of their range in a long time, so I'd been watching Ebay in the hope of one turning up. Until last week, when I discovered that a company called Friesland had apparently bought a chunk of Melitta's range some years ago and sell the original teapot[1]. I've just ordered one, and am utterly unreasonably excited about this.

Update: Friesland have apparently always produced the Utah teapot, but were part of the Melitta group for some time - they didn't buy the range from Melitta.

[1] They have them in 0.35, 0.85 and 1.4 litre sizes. I believe (based on the measurements here) that the 1.4 litre one matches the Utah teapot.

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how close to conformant is radv?

Posted by Dave Airlie on March 20, 2017 07:26 AM
I spent some time staring into the results of the VK-GL-CTS test suite on radv, which contains the Vulkan 1.0 conformance tests.

In order to be conformant you have to pass all the tests on the mustpass list for the Vulkan version you want to conform to, from the branch of the test suite for that version.

The latest CTS tests for 1.0 is the vulkan-cts-1.0.2 branch, and the mustpass list is in external/vulkancts/mustpass/1.0.2/vk-default.txt

Using some WIP radv patches in my github radv-wip-conform branch and the 1.0.2 test suite, today's results are on my Tonga GPU:

Test run totals:
Passed: 82551/150950 (54.7%)
Failed: 0/150950 (0.0%)
Not supported: 68397/150950 (45.3%)
Warnings: 2/150950 (0.0%)

That is pretty conformant (in fact it would pass as-is). However I need to clean up the patches in the branch and maybe figure out how to do some bits properly without hacks (particularly some semaphore wait tweaks), but that is most of the work done.

Thanks again to Bas and all other radv contributors.

Recipes 1.0

Posted by Matthias Clasen on March 17, 2017 02:31 PM

Recipes 1.0 is here, in time for GNOME 3.24 next week. You can get it here:


A flatpak is available here:


and can be installed with

flatpak install https://matthiasclasen.github.io/recipes-releases/gnome-recipes.flatpakref

Thanks to everybody who helped us to reach this point by contributing recipes, sending patches, translations or bug reports!


Recipes looks pretty good in GNOME Software already, but one thing is missing: No documentation costs us a perfect rating. Thankfully, Paul Cutler has shown up and started to fill this gap, so we can get the last icon turned blue with the next release.

Since one of the goals of Recipes is to be an exemplaric Flatpak app, I took this opportunity to investigate how we can handle documentation for sandboxed applications.

One option is to just put all the docs on the web and launch a web browser, but that feels a bit like cheating. Another option is to export all the documentation files from the sandbox and launch the host help browser on it. But this would require us to recursively export an entire directory full of possibly malicious content – so far, we’ve been careful to only export individual, known files like the desktop file or the app icon.

Therefore, we decided that we should instead ship a help browser in the GNOME runtime and launch it inside the sandbox. This turns out to work reasonably well, and will be used by more GNOME apps in the near future.


Apart from this ongoing work on documentation, a number of bug fixes and small improvements have found there way into the 1.0 release. For example, you can now find recipes by searching for the chef by name. And we ask for confirmation if you are about to close the window with unsaved changes.

Some of these changes were contributed by prospective Outreachy interns.


I have mentioned it before, you can find some information about our future plans for recipes here:


Your help is more than welcome!

A simple house-moving tip: use tape to mark empty cupboards

Posted by Peter Hutterer on March 17, 2017 02:00 AM

When you've emptied a cupboard, put masking tape across it, ideally in a colour that's highly visible. This way you immediately see know which ones are finished and which ones still need attention. You won't keep opening the cupboard a million times to check and after the move it takes merely seconds to undo.

The Internet of Microphones

Posted by Matthew Garrett on March 08, 2017 01:30 AM
So the CIA has tools to snoop on you via your TV and your Echo is testifying in a murder case and yet people are still buying connected devices with microphones in and why are they doing that the world is on fire surely this is terrible?

You're right that the world is terrible, but this isn't really a contributing factor to it. There's a few reasons why. The first is that there's really not any indication that the CIA and MI5 ever turned this into an actual deployable exploit. The development reports[1] describe a project that still didn't know what would happen to their exploit over firmware updates and a "fake off" mode that left a lit LED which wouldn't be there if the TV were actually off, so there's a potential for failed updates and people noticing that there's something wrong. It's certainly possible that development continued and it was turned into a polished and usable exploit, but it really just comes across as a bunch of nerds wanting to show off a neat demo.

But let's say it did get to the stage of being deployable - there's still not a great deal to worry about. No remote infection mechanism is described, so they'd need to do it locally. If someone is in a position to reflash your TV without you noticing, they're also in a position to, uh, just leave an internet connected microphone of their own. So how would they infect you remotely? TVs don't actually consume a huge amount of untrusted content from arbitrary sources[2], so that's much harder than it sounds and probably not worth it because:


Seriously your phone is like eleven billion times easier to infect than your TV is and you carry it everywhere. If the CIA want to spy on you, they'll do it via your phone. If you're paranoid enough to take the battery out of your phone before certain conversations, don't have those conversations in front of a TV with a microphone in it. But, uh, it's actually worse than that.

These days audio hardware usually consists of a very generic codec containing a bunch of digital→analogue converters, some analogue→digital converters and a bunch of io pins that can basically be wired up in arbitrary ways. Hardcoding the roles of these pins makes board layout more annoying and some people want more inputs than outputs and some people vice versa, so it's not uncommon for it to be possible to reconfigure an input as an output or vice versa. From software.

Anyone who's ever plugged a microphone into a speaker jack probably knows where I'm going with this. An attacker can "turn off" your TV, reconfigure the internal speaker output as an input and listen to you on your "microphoneless" TV. Have a nice day, and stop telling people that putting glue in their laptop microphone is any use unless you're telling them to disconnect the internal speakers as well.

If you're in a situation where you have to worry about an intelligence agency monitoring you, your TV is the least of your concerns - any device with speakers is just as bad. So what about Alexa? The summary here is, again, it's probably easier and more practical to just break your phone - it's probably near you whenever you're using an Echo anyway, and they also get to record you the rest of the time. The Echo platform is very restricted in terms of where it gets data[3], so it'd be incredibly hard to compromise without Amazon's cooperation. Amazon's not going to give their cooperation unless someone turns up with a warrant, and then we're back to you already being screwed enough that you should have got rid of all your electronics way earlier in this process. There are reasons to be worried about always listening devices, but intelligence agencies monitoring you shouldn't generally be one of them.

tl;dr: The CIA probably isn't listening to you through your TV, and if they are then you're almost certainly going to have a bad time anyway.

[1] Which I have obviously not read
[2] I look forward to the first person demonstrating code execution through malformed MPEG over terrestrial broadcast TV
[3] You'd need a vulnerability in its compressed audio codecs, and you'd need to convince the target to install a skill that played content from your servers

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A journey, with recipes

Posted by Matthias Clasen on March 06, 2017 04:13 AM

This month, we will release GNOME 3.24, and alongside, GNOME recipes will have its 1.0 release.

It has been quite a journey from just an idea at GUADEC last August to the application that we have now.

To the finish line

Since my last update, we have focused on completing our 1.0 goals. The last thing that we needed was to get enough contributed recipes to replace all the test data with actual content. And we’ve made it, thanks to the cooks in the GNOME community, we have plenty of great recipes now:

A few small features have still made their way in, despite the focus on polish. One thing I’ve played with is making appstream data useful inside the application itself, for showing ‘What’s New’ style information:

The timer support in cooking mode has seen quite a bit of improvement and polish.

I’ve also picked up my earlier experiment again, and built Recipes on OS X. This time, I got far enough to produce a dmg image:

A useful by-product of this effort was a number of bug fixes for the GTK+ Quartz backend, such as working fullscreen and window functions.

What next ?

1.0 will not be the end of the road for Recipes. There’s a number of exciting features on the post-1.0 roadmap.

For the next leg of the journey, we will welcome some Outreachy interns who will help us to add useful functionality, from unit conversion to shopping list export.

Better Resolution of Kerberos Credential Caches

Posted by Nathaniel McCallum on March 03, 2017 03:45 PM
DevConf is a great time of year. Lots of developers gather in one place and we get to discuss integration issues between projects that may not have a direct relationship. One of those issues this year was the desktop integration of Kerberos authentication. GNOME Online Accounts has supported the creation of Kerberos accounts since nearly the beginning, thanks to the effort of Debarshi Ray. However, we were made aware of an issue this year that had not come up before.

radv + steamvr

Posted by Dave Airlie on February 27, 2017 07:42 PM
If anyone wants to run SteamVR on top of radv, the code is all public now.


The external memory code will be going upstream to master once I clean it up a bit, the semaphore hack is waiting on kernel
changes, and the NIR shader hack is waiting on a new SteamVR build that removes the bad use of SPIR-V.

I've run Serious SAM TFE in VR mode on this branch.

The Fantasyland Code of Professionalism is an abuser's fantasy

Posted by Matthew Garrett on February 27, 2017 01:40 AM
The Fantasyland Institute of Learning is the organisation behind Lambdaconf, a functional programming conference perhaps best known for standing behind a racist they had invited as a speaker. The fallout of that has resulted in them trying to band together events in order to reduce disruption caused by sponsors or speakers declining to be associated with conferences that think inviting racists is more important than the comfort of non-racists, which is weird in all sorts of ways but not what I'm talking about here because they've also written a "Code of Professionalism" which is like a Code of Conduct except it protects abusers rather than minorities and no really it is genuinely as bad as it sounds.

The first thing you need to know is that the document uses its own jargon. Important here are the concepts of active and inactive participation - active participation is anything that you do within the community covered by a specific instance of the Code, inactive participation is anything that happens anywhere ever (ie, active participation is a subset of inactive participation). The restrictions based around active participation are broadly those that you'd expect in a very weak code of conduct - it's basically "Don't be mean", but with some quirks. The most significant is that there's a "Don't moralise" provision, which as written means saying "I think people who support slavery are bad" in a community setting is a violation of the code, but the description of discrimination means saying "I volunteer to mentor anybody from a minority background" could also result in any community member not from a minority background complaining that you've discriminated against them. It's just not very good.

Inactive participation is where things go badly wrong. If you engage in community or professional sabotage, or if you shame a member based on their behaviour inside the community, that's a violation. Community sabotage isn't defined and so basically allows a community to throw out whoever they want to. Professional sabotage means doing anything that can hurt a member's professional career. Shaming is saying anything negative about a member to a non-member if that information was obtained from within the community.

So, what does that mean? Here are some things that you are forbidden from doing:
  • If a member says something racist at a conference, you are not permitted to tell anyone who is not a community member that this happened (shaming)
  • If a member tries to assault you, you are not allowed to tell the police (shaming)
  • If a member gives a horribly racist speech at another conference, you are not allowed to suggest that they shouldn't be allowed to speak at your event (professional sabotage)
  • If a member of your community reports a violation and no action is taken, you are not allowed to warn other people outside the community that this is considered acceptable behaviour (community sabotage)

Now, clearly, some of these are unintentional - I don't think the authors of this policy would want to defend the idea that you can't report something to the police, and I'm sure they'd be willing to modify the document to permit this. But it's indicative of the mindset behind it. This policy has been written to protect people who are accused of doing something bad, not to protect people who have something bad done to them.

There are other examples of this. For instance, violations are not publicised unless the verdict is that they deserve banishment. If a member harasses another member but is merely given a warning, the victim is still not permitted to tell anyone else that this happened. The perpetrator is then free to repeat their behaviour in other communities, and the victim has to choose between either staying silent or warning them and risk being banished from the community for shaming.

If you're an abuser then this is perfect. You're in a position where your victims have to choose between their career (which will be harmed if they're unable to function in the community) and preventing the same thing from happening to others. Many will choose the former, which gives you far more freedom to continue abusing others. Which means that communities adopting the Fantasyland code will be more attractive to abusers, and become disproportionately populated by them.

I don't believe this is the intent, but it's an inevitable consequence of the priorities inherent in this code. No matter how many corner cases are cleaned up, if a code prevents you from saying bad things about people or communities it prevents people from being able to make informed choices about whether that community and its members are people they wish to associate with. When there are greater consequences to saying someone's racist than them being racist, you're fucking up badly.

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Bluetooth in Fedora

Posted by Nathaniel McCallum on February 16, 2017 08:53 PM
So… Bluetooth. It’s everywhere now. Well, everywhere except Fedora. Fedora does, of course support bluetooth. But even the most common workflows are somewhat spotty. We should improve this. To this end, I’ve enlisted the help of the Don Zickus, kernel developer extrordinaire, and Adam Williamson, the inimitable Fedora QA guru. The plan is to create a set of user tests for the most common bluetooth tasks. This plan has several goals.

Recipes by mail

Posted by Matthias Clasen on February 12, 2017 08:58 AM

Since I last wrote about GNOME recipes, we’ve mainly focused on completing our feature set for 3.24.

Todays 0.12.0 release brings us very close to covering all the goals we’ve set ourselves when we started working on recipes: We have a  fullscreen cooking mode

and recipes and shopping lists can be shared by email

Since the Share button has replaced the Export button, contributing your recipes is now easier too: Just choose the “Contribute” option and send the recipe to the new recipes-list@gnome.org mailing list.

While working on this, it suddenly dawned on my why I may have seen some recipe contributions in bugzilla that where missing attachments: bugzilla has a limit for the sizes of attachments it allows, and recipes with photos may hit this limit.

So, if you’ve tried to contributed a recipe via bugzilla, and ran into this problem, please send your recipe to recipes-list@gnome.org instead.

libinput knows about internal and external touchpads

Posted by Peter Hutterer on February 10, 2017 12:27 AM

libinput has a couple of features that 'automagically' work on touchpads such as disable-while-typing and the lid switch triggered disabling of touchpads and disabling the touchpad when an external mouse is plugged in [1]. But not all of these features make sense on all touchpads. For example, an Apple Magic Trackpad doesn't need disable-while-typing because unless you have a creative arrangement of input devices [2], the touchpad won't be where your palm is likely to hit it. Likewise, a Logitech T650 connected over a unifying receiver shouldn't get disabled when the laptop lid closes.

For this to work, libinput has some code to figure out whether a touchpad is internal or external. Initially we had some code to detect this but eventually moved this to the ID_INPUT_TOUCHPAD_INTEGRATION property now set by udev's hwdb (systemd 231 and later). Having it in the hwdb makes it quite trivial to override locally where the current rules are insufficient (and until the hwdb is fixed, thanks for filing a bug). We still have the fallback code though in case the tag is missing. On a sufficiently modern distribution, udevadm info /sys/class/input/event4 for your touchpad device node should show something like ID_INPUT_TOUCHPAD_INTEGRATION=internal.

So for any feature that libinput adds for touchpads, we only enable it where it makes sense. That's why your external touchpad doesn't trigger disable-while-typing or the lid switch.

[1] ok, I admit, this is something we should've left to the client, but now we have the feature.
[2] yes, I'm sure there's at least one person out there that uses the touchpad upside down in front of the keyboard and is now angry that libinput doesn't allow arbitrary rotation of the device combined with configurable dwt. I think of you every night I cry myself to sleep.

New fwupd release, and why you should buy a Dell

Posted by Richard Hughes on February 08, 2017 01:14 PM

This morning I released the first new release of fwupd on the 0.8.x branch. This has a number of interesting fixes, but more importantly adds the following new features:

  • Adds support for Intel Thunderbolt devices
  • Adds support for some Logitech Unifying devices
  • Adds support for Synaptics MST cascaded hubs
  • Adds support for the Altus-Metrum ChaosKey device
  • Adds Dell-specific functionality to allow other plugins turn on TBT/GPIO

Mario Limonciello from Dell has worked really hard on this release, and I can say with conviction: If you want to support a hardware company that cares about Linux — buy a Dell. They seem to be driving the importance of Linux support into their partners and suppliers. I wish other vendors would do the same.

Open Desktop Review System : One Year Review

Posted by Richard Hughes on February 06, 2017 10:01 AM

This weekend we had the 2,000th review submitted to the ODRS review system. Every month we’re getting an additional ~300 reviews and about 500,000 requests for reviews from the system. The reviews that have been contributed are in 94 languages, and from 1387 different users.

Most reviews have come from Fedora (which installs GNOME Software as part of the default workstation) but other distros like Debian and Arch are catching up all the time. I’d still welcome KDE software center clients like Discover and Apper using the ODRS although we do have quite a lot of KDE software reviews submitted using GNOME Software.

Out of ~2000 reviews just 23 have been marked as inappropriate, of which I agreed with 7 (inappropriate is supposed to be swearing or abuse, not just being unhelpful) and those 7 were deleted. The mean time between a review being posted that is actually abuse and it being marked as such (or me noticing it in the admin panel) is just over 8 hours, which is certainly good enough. In the last few months 5523 people have clicked the “upvote” button on a review, and 1474 people clicked the “downvote” button on a review. Although that’s less voting that I hoped for, that’s certainly enough to give good quality sorting of reviews to end users in most locales. If you have a couple of hours on your hands, gnome-software --mode=moderate is a great way to upvote/downvote a lot of reviews in your locale.

So, onward to 3,000 reviews. Many thanks to those who submitted reviews already — you’re helping new users who don’t know what software they should install.