Search Results: "pere"

12 September 2022

Petter Reinholdtsen: Time to translate the Bullseye edition of the Debian Administrator's Handbook

(The picture is of the previous edition.) Almost two years after the previous Norwegian Bokm l translation of the "The Debian Administrator's Handbook" was published, a new edition is finally being prepared. The english text is updated, and it is time to start working on the translations. Around 37 percent of the strings have been updated, one way or another, and the translations starting from a complete Debian Buster edition now need to bring their translation up from 63% to 100%. The complete book is licensed using a Creative Commons license, and has been published in several languages over the years. The translations are done by volunteers to bring Linux in their native tongue. The last time I checked, it complete text was available in English, Norwegian Bokm l, German, Indonesian, Brazil Portuguese and Spanish. In addition, work has been started for Arabic (Morocco), Catalan, Chinese (Simplified), Chinese (Traditional), Croatian, Czech, Danish, Dutch, French, Greek, Italian, Japanese, Korean, Persian, Polish, Romanian, Russian, Swedish, Turkish and Vietnamese. The translation is conducted on the hosted weblate project page. Prospective translators are recommeded to subscribe to the translators mailing list and should also check out the instructions for contributors. I am one of the Norwegian Bokm l translators of this book, and we have just started. Your contribution is most welcome. As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

28 July 2022

Matthew Garrett: UEFI rootkits and UEFI secure boot

Kaspersky describes a UEFI-implant used to attack Windows systems. Based on it appearing to require patching of the system firmware image, they hypothesise that it's propagated by manually dumping the contents of the system flash, modifying it, and then reflashing it back to the board. This probably requires physical access to the board, so it's not especially terrifying - if you're in a situation where someone's sufficiently enthusiastic about targeting you that they're reflashing your computer by hand, it's likely that you're going to have a bad time regardless.

But let's think about why this is in the firmware at all. Sophos previously discussed an implant that's sufficiently similar in some technical details that Kaspersky suggest they may be related to some degree. One notable difference is that the MyKings implant described by Sophos installs itself into the boot block of legacy MBR partitioned disks. This code will only be executed on old-style BIOS systems (or UEFI systems booting in BIOS compatibility mode), and they have no support for code signatures, so there's no need to be especially clever. Run malicious code in the boot block, patch the next stage loader, follow that chain all the way up to the kernel. Simple.

One notable distinction here is that the MBR boot block approach won't be persistent - if you reinstall the OS, the MBR will be rewritten[1] and the infection is gone. UEFI doesn't really change much here - if you reinstall Windows a new copy of the bootloader will be written out and the UEFI boot variables (that tell the firmware which bootloader to execute) will be updated to point at that. The implant may still be on disk somewhere, but it won't be run.

But there's a way to avoid this. UEFI supports loading firmware-level drivers from disk. If, rather than providing a backdoored bootloader, the implant takes the form of a UEFI driver, the attacker can set a different set of variables that tell the firmware to load that driver at boot time, before running the bootloader. OS reinstalls won't modify these variables, which means the implant will survive and can reinfect the new OS install. The only way to get rid of the implant is to either reformat the drive entirely (which most OS installers won't do by default) or replace the drive before installation.

This is much easier than patching the system firmware, and achieves similar outcomes - the number of infected users who are going to wipe their drives to reinstall is fairly low, and the kernel could be patched to hide the presence of the implant on the filesystem[2]. It's possible that the goal was to make identification as hard as possible, but there's a simpler argument here - if the firmware has UEFI Secure Boot enabled, the firmware will refuse to load such a driver, and the implant won't work. You could certainly just patch the firmware to disable secure boot and lie about it, but if you're at the point of patching the firmware anyway you may as well just do the extra work of installing your implant there.

I think there's a reasonable argument that the existence of firmware-level rootkits suggests that UEFI Secure Boot is doing its job and is pushing attackers into lower levels of the stack in order to obtain the same outcomes. Technologies like Intel's Boot Guard may (in their current form) tend to block user choice, but in theory should be effective in blocking attacks of this form and making things even harder for attackers. It should already be impossible to perform attacks like the one Kaspersky describes on more modern hardware (the system should identify that the firmware has been tampered with and fail to boot), which pushes things even further - attackers will have to take advantage of vulnerabilities in the specific firmware they're targeting. This obviously means there's an incentive to find more firmware vulnerabilities, which means the ability to apply security updates for system firmware as easily as security updates for OS components is vital (hint hint if your system firmware updates aren't available via LVFS you're probably doing it wrong).

We've known that UEFI rootkits have existed for a while (Hacking Team had one in 2015), but it's interesting to see a fairly widespread one out in the wild. Protecting against this kind of attack involves securing the entire boot chain, including the firmware itself. The industry has clearly been making progress in this respect, and it'll be interesting to see whether such attacks become more common (because Secure Boot works but firmware security is bad) or not.

[1] As we all remember from Windows installs overwriting Linux bootloaders
[2] Although this does run the risk of an infected user booting another OS instead, and being able to see the implant

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16 July 2022

Petter Reinholdtsen: Automatic LinuxCNC servo PID tuning?

While working on a CNC with servo motors controlled by the LinuxCNC PID controller, I recently had to learn how to tune the collection of values that control such mathematical machinery that a PID controller is. It proved to be a lot harder than I hoped, and I still have not succeeded in getting the Z PID controller to successfully defy gravity, nor X and Y to move accurately and reliably. But while climbing up this rather steep learning curve, I discovered that some motor control systems are able to tune their PID controllers. I got the impression from the documentation that LinuxCNC were not. This proved to be not true The LinuxCNC pid component is the recommended PID controller to use. It uses eight constants Pgain, Igain, Dgain, bias, FF0, FF1, FF2 and FF3 to calculate the output value based on current and wanted state, and all of these need to have a sensible value for the controller to behave properly. Note, there are even more values involved, theser are just the most important ones. In my case I need the X, Y and Z axes to follow the requested path with little error. This has proved quite a challenge for someone who have never tuned a PID controller before, but there is at least some help to be found. I discovered that included in LinuxCNC was this old PID component at_pid claiming to have auto tuning capabilities. Sadly it had been neglected since 2011, and could not be used as a plug in replacement for the default pid component. One would have to rewriting the LinuxCNC HAL setup to test at_pid. This was rather sad, when I wanted to quickly test auto tuning to see if it did a better job than me at figuring out good P, I and D values to use. I decided to have a look if the situation could be improved. This involved trying to understand the code and history of the pid and at_pid components. Apparently they had a common ancestor, as code structure, comments and variable names were quite close to each other. Sadly this was not reflected in the git history, making it hard to figure out what really happened. My guess is that the author of at_pid.c took a version of pid.c, rewrote it to follow the structure he wished pid.c to have, then added support for auto tuning and finally got it included into the LinuxCNC repository. The restructuring and lack of early history made it harder to figure out which part of the code were relevant to the auto tuning, and which part of the code needed to be updated to work the same way as the current pid.c implementation. I started by trying to isolate relevant changes in pid.c, and applying them to at_pid.c. My aim was to make sure the at_pid component could replace the pid component with a simple change in the HAL setup loadrt line, without having to "rewire" the rest of the HAL configuration. After a few hours following this approach, I had learned quite a lot about the code structure of both components, while concluding I was heading down the wrong rabbit hole, and should get back to the surface and find a different path. For the second attempt, I decided to throw away all the PID control related part of the original at_pid.c, and instead isolate and lift the auto tuning part of the code and inject it into a copy of pid.c. This ensured compatibility with the current pid component, while adding auto tuning as a run time option. To make it easier to identify the relevant parts in the future, I wrapped all the auto tuning code with '#ifdef AUTO_TUNER'. The end result behave just like the current pid component by default, as that part of the code is identical. The end result entered the LinuxCNC master branch a few days ago. To enable auto tuning, one need to set a few HAL pins in the PID component. The most important ones are tune-effort, tune-mode and tune-start. But lets take a step back, and see what the auto tuning code will do. I do not know the mathematical foundation of the at_pid algorithm, but from observation I can tell that the algorithm will, when enabled, produce a square wave pattern centered around the bias value on the output pin of the PID controller. This can be seen using the HAL Scope provided by LinuxCNC. In my case, this is translated into voltage (+-10V) sent to the motor controller, which in turn is translated into motor speed. So at_pid will ask the motor to move the axis back and forth. The number of cycles in the pattern is controlled by the tune-cycles pin, and the extremes of the wave pattern is controlled by the tune-effort pin. Of course, trying to change the direction of a physical object instantly (as in going directly from a positive voltage to the equivalent negative voltage) do not change velocity instantly, and it take some time for the object to slow down and move in the opposite direction. This result in a more smooth movement wave form, as the axis in question were vibrating back and forth. When the axis reached the target speed in the opposing direction, the auto tuner change direction again. After several of these changes, the average time delay between the 'peaks' and 'valleys' of this movement graph is then used to calculate proposed values for Pgain, Igain and Dgain, and insert them into the HAL model to use by the pid controller. The auto tuned settings are not great, but htye work a lot better than the values I had been able to cook up on my own, at least for the horizontal X and Y axis. But I had to use very small tune-effort values, as my motor controllers error out if the voltage change too quickly. I've been less lucky with the Z axis, which is moving a heavy object up and down, and seem to confuse the algorithm. The Z axis movement became a lot better when I introduced a bias value to counter the gravitational drag, but I will have to work a lot more on the Z axis PID values. Armed with this knowledge, it is time to look at how to do the tuning. Lets say the HAL configuration in question load the PID component for X, Y and Z like this:
loadrt pid names=pid.x,pid.y,pid.z
Armed with the new and improved at_pid component, the new line will look like this:
loadrt at_pid names=pid.x,pid.y,pid.z
The rest of the HAL setup can stay the same. This work because the components are referenced by name. If the component had used count=3 instead, all use of pid.# had to be changed to at_pid.#. To start tuning the X axis, move the axis to the middle of its range, to make sure it do not hit anything when it start moving back and forth. Next, set the tune-effort to a low number in the output range. I used 0.1 as my initial value. Next, assign 1 to the tune-mode value. Note, this will disable the pid controlling part and feed 0 to the output pin, which in my case initially caused a lot of drift. In my case it proved to be a good idea with X and Y to tune the motor driver to make sure 0 voltage stopped the motor rotation. On the other hand, for the Z axis this proved to be a bad idea, so it will depend on your setup. It might help to set the bias value to a output value that reduce or eliminate the axis drift. Finally, after setting tune-mode, set tune-start to 1 to activate the auto tuning. If all go well, your axis will vibrate for a few seconds and when it is done, new values for Pgain, Igain and Dgain will be active. To test them, change tune-mode back to 0. Note that this might cause the machine to suddenly jerk as it bring the axis back to its commanded position, which it might have drifted away from during tuning. To summarize with some halcmd lines:
setp pid.x.tune-effort 0.1
setp pid.x.tune-mode 1
setp pid.x.tune-start 1
# wait for the tuning to complete
setp pid.x.tune-mode 0
After doing this task quite a few times while trying to figure out how to properly tune the PID controllers on the machine in, I decided to figure out if this process could be automated, and wrote a script to do the entire tuning process from power on. The end result will ensure the machine is powered on and ready to run, home all axis if it is not already done, check that the extra tuning pins are available, move the axis to its mid point, run the auto tuning and re-enable the pid controller when it is done. It can be run several times. Check out the run-auto-pid-tuner script on github if you want to learn how it is done. My hope is that this little adventure can inspire someone who know more about motor PID controller tuning can implement even better algorithms for automatic PID tuning in LinuxCNC, making life easier for both me and all the others that want to use LinuxCNC but lack the in depth knowledge needed to tune PID controllers well. As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

20 June 2022

Petter Reinholdtsen: My free software activity of late (2022)

I guess it is time to bring some light on the various free software and open culture activities and projects I have worked on or been involved in the last year and a half. First, lets mention the book releases I managed to publish. The Cory Doctorow book "Hvordan knuse overv kningskapitalismen" argue that it is not the magic machine learning of the big technology companies that causes the surveillance capitalism to thrive, it is the lack of trust busting to enforce existing anti-monopoly laws. I also published a family of dictionaries for machinists, one sorted on the English words, one sorted on the Norwegian and the last sorted on the North S mi words. A bit on the back burner but not forgotten is the Debian Administrators Handbook, where a new edition is being worked on. I have not spent as much time as I want to help bring it to completion, but hope I will get more spare time to look at it before the end of the year. With my Debian had I have spent time on several projects, both updating existing packages, helping to bring in new packages and working with upstream projects to try to get them ready to go into Debian. The list is rather long, and I will only mention my own isenkram, openmotor, vlc bittorrent plugin, xprintidle, norwegian letter style for latex, bs1770gain, and recordmydesktop. In addition to these I have sponsored several packages into Debian, like audmes. The last year I have looked at several infrastructure projects for collecting meter data and video surveillance recordings. This include several ONVIF related tools like onvifviewer and zoneminder as well as rtl-433, wmbusmeters and rtl-wmbus. In parallel with this I have looked at fabrication related free software solutions like pycam and LinuxCNC. The latter recently gained improved translation support using po4a and weblate, which was a harder nut to crack that I had anticipated when I started. Several hours have been spent translating free software to Norwegian Bokm l on the Weblate hosted service. Do not have a complete list, but you will find my contributions in at least gnucash, minetest and po4a. I also spent quite some time on the Norwegian archiving specification Noark 5, and its companion project Nikita implementing the API specification for Noark 5. Recently I have been looking into free software tools to do company accounting here in Norway., which present an interesting mix between law, rules, regulations, format specifications and API interfaces. I guess I should also mention the Norwegian community driven government interfacing projects Mimes Br nn and Fiksgatami, which have ended up in a kind of limbo while the future of the projects is being worked out. These are just a few of the projects I have been involved it, and would like to give more visibility. I'll stop here to avoid delaying this post. As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

10 June 2022

Lisandro Dami n Nicanor P rez Meyer: Qt 6 in Debian bullseye

As announced some time ago on Debian Backport s mailing list I will be backporting Qt 6 to Debian 11 Bullseye . This comprises the (so far) 29 source packages that compose Qt 6 and libassimp. The Qt Company wanted to let us Debian users also enjoy Qt 6 on Bullseye, so they contacted me (and by extension my employer ICS) to bring this forward. As said in the mail I sent to the backports list I m making the commitment to maintain the packages myself, but I m really happy the Qt Company asked me for this. You can download Qt 6 for Debian Bullseye s backports by following the instructions. Also a big kudos to IOhannes m zm lnig, the assimp maintainer, who promptly helped me to get it backported. Enjoy!

3 June 2022

Petter Reinholdtsen: LinuxCNC translators life just got a bit easier

Back in oktober last year, when I started looking at the LinuxCNC system, I proposed to change the documentation build system make life easier for translators. The original system consisted of independently written documentation files for each language, with no automated way to track changes done in other translations and no help for the translators to know how much was left to translated. By using the po4a system to generate POT and PO files from the English documentation, this can be improved. A small team of LinuxCNC contributors got together and today our labour finally payed off. Since a few hours ago, it is now possible to translate the LinuxCNC documentation on Weblate, alongside the program itself. The effort to migrate the documentation to use po4a has been both slow and frustrating. I am very happy we finally made it. As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

20 April 2022

Petter Reinholdtsen: geteltorito make CD firmware upgrades a breeze

Recently I wanted to upgrade the firmware of my thinkpad, and located the firmware download page from Lenovo (which annoyingly do not allow access via Tor, forcing me to hand them more personal information that I would like). The download from Lenovo is a bootable ISO image, which is a bit of a problem when all I got available is a USB memory stick. I tried booting the ISO as a USB stick, but this did not work. But genisoimage came to the rescue. The geteltorito program in the genisoimage binary package is able to convert the bootable ISO image to a bootable USB stick using a simple command line recipe, which I then can write to the most recently inserted USB stick:
geteltorito -o usbstick.img lenovo-firmware.iso
sudo dd bs=10M if=usbstick.img of=$(ls -tr /dev/sd? tail -1)
This USB stick booted the firmware upgrader just fine, and in a few minutes my machine had the latest and greatest BIOS firmware in place.

Petter Reinholdtsen: genisoimage make CD firmware upgrades a breeze

Recently I wanted to upgrade the firmware of my thinkpad, and located the firmware download page from Lenovo (which annoyingly do not allow access via Tor, forcing me to hand them more personal information that I would like). The download from Lenovo is a bootable ISO image, which is a bit of a problem when all I got available is a USB memory stick. I tried booting the ISO as a USB stick, but this did not work. But genisoimage came to the rescue. The geteltorito program in the genisoimage package is able to convert the bootable ISO image to a bootable USB stick using a simple command line recipe, which I then can write to the most recently inserted USB stick:
geteltorito -o usbstick.img lenovo-firmware.iso
sudo dd bs=10M if=usbstick.img of=$(ls -tr /dev/sd? tail -1)
This USB stick booted the firmware upgrader just fine, and in a few minutes my machine had the latest and greatest BIOS firmware in place.

16 April 2022

Petter Reinholdtsen: Playing and encoding AV1 in Debian Bullseye

Inspired by the recent news of AV1 hardware encoding support from Intel, I decided to look into the state of AV1 on Linux today. AV1 is a free and open standard as defined by Digistan without any royalty payment requirement, unlike its much used competitor encoding H.264. While looking, I came across an 5 year old question on askubuntu.com which in turn inspired me to check out how things are in Debian Stable regarding AV1. The test file listed in the question (askubuntu_test_aom.mp4) did not exist any more, so I tracked down a different set of test files on av1.webmfiles.org to test them with the various video tools I had installed on my machine. I was happy to discover that AV1 decoding and playback worked with almost every tool I tested:
mediainfo ok
dragonplayer ok
ffmpeg / ffplay ok
gnome-mplayer fail
mplayer ok
mpv ok
parole ok
vlc ok
firefox ok
chromium ok
AV1 encoding is available in Debian Stable from the aom-tools version 1.0.0.errata1-3 package, using the aomenc tool. The encoding using the package in Debian Stable is quite slow, with the frame rate for my 10 second test video at around 0.25 fps. My 10 second video test took 16 minutes and 11 seconds on my test machine. I tested by first running ffmpeg and then aomenc using the recipe provided by the askubuntu recipe above. I had to remove the '--row-mt=1' option, as it was not supported in my 1.0.0 version. The encoding only used a single thread, according to top.
ffmpeg -i some-old-video.ogv -t 10 -pix_fmt yuv420p video.y4m
aomenc --fps=24/1 -u 0 --codec=av1 --target-bitrate=1000 \
  --lag-in-frames=25 --auto-alt-ref=1 -t 24 --cpu-used=8 \
  --tile-columns=2 --tile-rows=2 -o output.webm video.y4m
As version 1.0.0 currently have several unsolved security issues in Debian Stable, and to see if the recent backport provided in Debian is any quicker, I ran apt -t bullseye-backports install aom-tools to fetch the backported version and re-encoded the video using the latest version. This time the '--row-mt=1' option worked, and the encoding was done in 46 seconds with a frame rate of around 5.22 fps. This time it seem to be using all my four cores to encode. Encoding speed is still too low for streaming and real time, which would require frame rates above 25 fps, but might be good enough for offline encoding. I am very happy to see AV1 playback working so well with the default tools in Debian Stable. I hope the encoding situation improve too, allowing even a slow old computer like my 10 year old laptop to be used for encoding. As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

12 March 2022

Petter Reinholdtsen: Publish Hargassner wood chip boiler state to MQTT

Recently I had a look at a Hargassner wood chip boiler, and what kind of free software can be used to monitor and control it. The boiler can be connected to some cloud service via what the producer call an Internet Gateway, which seem to be a computer connecting to the boiler and passing the information gathered to the cloud. I discovered the boiler controller got an IP address on the local network and listen on TCP port 23 to provide status information as a text line of numbers. It also provide a HTTP server listening on port 80, but I have not yet figured out what it can do beside return an error code. If I am to believe various free software implementations talking to such boiler, the interpretation of the line of numbers differ between type of boiler and software version on the boiler. By comparing the list of numbers on the front panel of the boiler with the numbers returned via TCP, I have been able to figure out several of the numbers, but there are a lot left to understand. I've located several temperature measurements and hours running values, as well as oxygen measurements and counters. I decided to write a simple parser in Python for the values I figured out so far, and a simple MQTT injector publishing both the interpreted and the unknown values on a MQTT bus to make collecting and graphing simpler. The end result is available from the hargassner2mqtt project page on gitlab. I very much welcome patches extending the parser to understand more values, boiler types and software versions. I do not really expect very few free software developers got their hands on such unit to experiment, but it would be fun if others too find this project useful. As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

2 March 2022

Petter Reinholdtsen: Run your industrial metal working machine using Debian?

After many months of hard work by the good people involved in LinuxCNC, the system was accepted Sunday into Debian. Once it was available from Debian, I was surprised to discover from its popularity-contest numbers that people have been reporting its use since 2012. Its project site might be a good place to check out, but sadly is not working when visiting via Tor. But what is LinuxCNC, you are probably wondering? Perhaps a Wikipedia quote is in place?
"LinuxCNC is a software system for numerical control of machines such as milling machines, lathes, plasma cutters, routers, cutting machines, robots and hexapods. It can control up to 9 axes or joints of a CNC machine using G-code (RS-274NGC) as input. It has several GUIs suited to specific kinds of usage (touch screen, interactive development)."
It can even control 3D printers. And even though the Wikipedia page indicate that it can only work with hard real time kernel features, it can also work with the user space soft real time features provided by the Debian kernel. The source code is available from Github. The last few months I've been involved in the translation setup for the program and documentation. Translators are most welcome to join the effort using Weblate. As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

Petter Reinholdtsen: Run your industrial metal working machine using Debian?

After many months of hard work by the good people involved in LinuxCNC, the system was accepted Sunday into Debian. Once it was available from Debian, I was surprised to discover from its popularity-contest numbers that people have been reporting its use since 2012. Its project site might be a good place to check out, but sadly is not working when visiting via Tor. But what is LinuxCNC, you are probably wondering? Perhaps a Wikipedia quote is in place?
"LinuxCNC is a software system for numerical control of machines such as milling machines, lathes, plasma cutters, routers, cutting machines, robots and hexapods. It can control up to 9 axes or joints of a CNC machine using G-code (RS-274NGC) as input. It has several GUIs suited to specific kinds of usage (touch screen, interactive development)."
It can even control 3D printers. And even though the Wikipedia page indicate that it can only work with hard real time kernel features, it can also work with the user space soft real time features provided by the Debian kernel. The source code is available from Github. The last few months I've been involved in the translation setup for the program and documentation. Translators are most welcome to join the effort using Weblate. As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

14 February 2022

Petter Reinholdtsen: Updated vlc bittorrent plugin in Debian (version 2.14)

I am very happy to report that a new version of the VLC bittorrent plugin was just uploaded into debian. The changes since last time is mostly code clean in the download code. The package is currently in Debian unstable, but should be available in Debian testing son. To test it, simply install it like this:
apt install vlc-plugin-bittorrent
After it is installed, you can try to use it to play a file downloaded live via bittorrent like this:
vlc https://archive.org/download/Glass_201703/Glass_201703_archive.torrent
It can also use magnet links and local .torrent files like the ones provided by the Internet Archive. Another example is the Love Nest Buster Keaton movie, where one can click on the 'Torrent' link to get going. As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

Petter Reinholdtsen: Updated vlc bittorrent plugin in Debian (version 2.14)

I am very happy to report that a new version of the VLC bittorrent plugin was just uploaded into debian. The changes since last time is mostly code clean in the download code. The package is currently in Debian unstable, but should be available in Debian testing son. To test it, simply install it like this:
apt install vlc-plugin-bittorrent
After it is installed, you can try to use it to play a file downloaded live via bittorrent like this:
vlc https://archive.org/download/Glass_201703/Glass_201703_archive.torrent
It can also use magnet links and local .torrent files like the ones provided by the Internet Archive. Another example is the Love Nest Buster Keaton movie, where one can click on the 'Torrent' link to get going. As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

17 January 2022

Matthew Garrett: Boot Guard and PSB have user-hostile defaults

Compromising an OS without it being detectable is hard. Modern operating systems support the imposition of a security policy or the launch of some sort of monitoring agent sufficient early in boot that even if you compromise the OS, you're probably going to have left some sort of detectable trace[1]. You can avoid this by attacking the lower layers - if you compromise the bootloader then it can just hotpatch a backdoor into the kernel before executing it, for instance.

This is avoided via one of two mechanisms. Measured boot (such as TPM-based Trusted Boot) makes a tamper-proof cryptographic record of what the system booted, with each component in turn creating a measurement of the next component in the boot chain. If a component is tampered with, its measurement will be different. This can be used to either prevent the release of a cryptographic secret if the boot chain is modified (for instance, using the TPM to encrypt the disk encryption key), or can be used to attest the boot state to another device which can tell you whether you're safe or not. The other approach is verified boot (such as UEFI Secure Boot), where each component in the boot chain verifies the next component before executing it. If the verification fails, execution halts.

In both cases, each component in the boot chain measures and/or verifies the next. But something needs to be the first link in this chain, and traditionally this was the system firmware. Which means you could tamper with the system firmware and subvert the entire process - either have the firmware patch the bootloader in RAM after measuring or verifying it, or just load a modified bootloader and lie about the measurements or ignore the verification. Attackers had already been targeting the firmware (Hacking Team had something along these lines, although this was pre-secure boot so just dropped a rootkit into the OS), and given a well-implemented measured and verified boot chain, the firmware becomes an even more attractive target.

Intel's Boot Guard and AMD's Platform Secure Boot attempt to solve this problem by moving the validation of the core system firmware to an (approximately) immutable environment. Intel's solution involves the Management Engine, a separate x86 core integrated into the motherboard chipset. The ME's boot ROM verifies a signature on its firmware before executing it, and once the ME is up it verifies that the system firmware's bootblock is signed using a public key that corresponds to a hash blown into one-time programmable fuses in the chipset. What happens next depends on policy - it can either prevent the system from booting, allow the system to boot to recover the firmware but automatically shut it down after a while, or flag the failure but allow the system to boot anyway. Most policies will also involve a measurement of the bootblock being pushed into the TPM.

AMD's Platform Secure Boot is slightly different. Rather than the root of trust living in the motherboard chipset, it's in AMD's Platform Security Processor which is incorporated directly onto the CPU die. Similar to Boot Guard, the PSP has ROM that verifies the PSP's own firmware, and then that firmware verifies the system firmware signature against a set of blown fuses in the CPU. If that fails, system boot is halted. I'm having trouble finding decent technical documentation about PSB, and what I have found doesn't mention measuring anything into the TPM - if this is the case, PSB only implements verified boot, not measured boot.

What's the practical upshot of this? The first is that you can't replace the system firmware with anything that doesn't have a valid signature, which effectively means you're locked into firmware the vendor chooses to sign. This prevents replacing the system firmware with either a replacement implementation (such as Coreboot) or a modified version of the original implementation (such as firmware that disables locking of CPU functionality or removes hardware allowlists). In this respect, enforcing system firmware verification works against the user rather than benefiting them.
Of course, it also prevents an attacker from doing the same thing, but while this is a real threat to some users, I think it's hard to say that it's a realistic threat for most users.

The problem is that vendors are shipping with Boot Guard and (increasingly) PSB enabled by default. In the AMD case this causes another problem - because the fuses are in the CPU itself, a CPU that's had PSB enabled is no longer compatible with any motherboards running firmware that wasn't signed with the same key. If a user wants to upgrade their system's CPU, they're effectively unable to sell the old one. But in both scenarios, the user's ability to control what their system is running is reduced.

As I said, the threat that these technologies seek to protect against is real. If you're a large company that handles a lot of sensitive data, you should probably worry about it. If you're a journalist or an activist dealing with governments that have a track record of targeting people like you, it should probably be part of your threat model. But otherwise, the probability of you being hit by a purely userland attack is so ludicrously high compared to you being targeted this way that it's just not a big deal.

I think there's a more reasonable tradeoff than where we've ended up. Tying things like disk encryption secrets to TPM state means that if the system firmware is measured into the TPM prior to being executed, we can at least detect that the firmware has been tampered with. In this case nothing prevents the firmware being modified, there's just a record in your TPM that it's no longer the same as it was when you encrypted the secret. So, here's what I'd suggest:

1) The default behaviour of technologies like Boot Guard or PSB should be to measure the firmware signing key and whether the firmware has a valid signature into PCR 7 (the TPM register that is also used to record which UEFI Secure Boot signing key is used to verify the bootloader).
2) If the PCR 7 value changes, the disk encryption key release will be blocked, and the user will be redirected to a key recovery process. This should include remote attestation, allowing the user to be informed that their firmware signing situation has changed.
3) Tooling should be provided to switch the policy from merely measuring to verifying, and users at meaningful risk of firmware-based attacks should be encouraged to make use of this tooling

This would allow users to replace their system firmware at will, at the cost of having to re-seal their disk encryption keys against the new TPM measurements. It would provide enough information that, in the (unlikely for most users) scenario that their firmware has actually been modified without their knowledge, they can identify that. And it would allow users who are at high risk to switch to a higher security state, and for hardware that is explicitly intended to be resilient against attacks to have different defaults.

This is frustratingly close to possible with Boot Guard, but I don't think it's quite there. Before you've blown the Boot Guard fuses, the Boot Guard policy can be read out of flash. This means that you can drop a Boot Guard configuration into flash telling the ME to measure the firmware but not prevent it from running. But there are two problems remaining:

1) The measurement is made into PCR 0, and PCR 0 changes every time your firmware is updated. That makes it a bad default for sealing encryption keys.
2) It doesn't look like the policy is measured before being enforced. This means that an attacker can simply reflash modified firmware with a policy that disables measurement and then make a fake measurement that makes it look like the firmware is ok.

Fixing this seems simple enough - the Boot Guard policy should always be measured, and measurements of the policy and the signing key should be made into a PCR other than PCR 0. If an attacker modified the policy, the PCR value would change. If an attacker modified the firmware without modifying the policy, the PCR value would also change. People who are at high risk would run an app that would blow the Boot Guard policy into fuses rather than just relying on the copy in flash, and enable verification as well as measurement. Now if an attacker tampers with the firmware, the system simply refuses to boot and the attacker doesn't get anything.

Things are harder on the AMD side. I can't find any indication that PSB supports measuring the firmware at all, which obviously makes this approach impossible. I'm somewhat surprised by that, and so wouldn't be surprised if it does do a measurement somewhere. If it doesn't, there's a rather more significant problem - if a system has a socketed CPU, and someone has sufficient physical access to replace the firmware, they can just swap out the CPU as well with one that doesn't have PSB enabled. Under normal circumstances the system firmware can detect this and prompt the user, but given that the attacker has just replaced the firmware we can assume that they'd do so with firmware that doesn't decide to tell the user what just happened. In the absence of better documentation, it's extremely hard to say that PSB actually provides meaningful security benefits.

So, overall: I think Boot Guard protects against a real-world attack that matters to a small but important set of targets. I think most of its benefits could be provided in a way that still gave users control over their system firmware, while also permitting high-risk targets to opt-in to stronger guarantees. Based on what's publicly documented about PSB, it's hard to say that it provides real-world security benefits for anyone at present. In both cases, what's actually shipping reduces the control people have over their systems, and should be considered user-hostile.

[1] Assuming that someone's both turning this on and actually looking at the data produced

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19 December 2021

Russ Allbery: Review: Raybearer

Review: Raybearer, by Jordan Ifueko
Series: Raybearer #1
Publisher: Amulet Books
Copyright: 2020
ISBN: 1-68335-719-1
Format: Kindle
Pages: 308
Tarisai was raised alone in Bhekina House by an array of servants and tutors who were not allowed to touch her. Glimpses of the world were fleeting and sometimes ended by nailed-shut windows. Her life revolved around her rarely-seen mother, The Lady, who treats her with deep affection but rarely offers a word of praise, instead only pushing her to study harder. The servants whispered behind her back (but still in her hearing) that she was not human. At the age of seven, in a child's attempt to locate her absent mother by sneaking out of the house, she finds her father and is told a piece of the truth: she is the daughter of the Lady and a captive ehru, a djinn. At the age of eleven she's sent with two guardians to Oluwan City, the capital of Aritsar, to enter a competition she knows nothing about, for reasons no one has ever explained. Raybearer is a young adult fantasy novel, the first of a duology. Like a lot of young adult novels, it is a coming of age story that follows Tarisai from the end of her highly manipulated childhood through her introduction to a world she was carefully never taught about. Like a lot of young adult fantasy novels, Tarisai has some unusual abilities. What those are, and why she has them, is perhaps less obvious than it may appear at first. Unlike a lot of young adult fantasy novels, Raybearer is not set in a facsimile of Western Europe, the structure of gods and religion is not obviously derived from Christianity or Greek or Norse mythology, and neither Tarisai nor most of the characters of this story are white. Some of the characters are; Ifueko draws from a grab bag of cultures that does include European as well as African, Middle Eastern, and Asian. But the food, the physical descriptions, the landscape, and the hair and hair styles feel primarily African not in the sense of specific identifiable regions, but in the same way that most fantasy feels European even if the map isn't recognizable. That gives this story a freshness that I found delightful. The mythology of this world shares some similarities to standard fantasy tropes, including a bargain with the underworld that plays a similar role to fae bargains in some European fantasy, but it also goes in different directions and finds atypical balances, which gave the story room to catch me by surprise. The magical center of this book (and series), which Tarisai is carefully not told about until the story starts, is a system for anointing and protecting the emperor: selection of people who swear loyalty to him and each other and become his innermost circle, and thereby grant him magical protection. The emperor himself is the Raybearer, possessing an artifact that makes him invulnerable to one form of death for each member of his council he anoints. At eleven council members, he becomes invulnerable to anything but old age, or an attack from one of the council themselves. As the reader learns early in the book, that last part is important. Tarisai is an assassin; her mother's goal is for her to be selected as a member of the council for the prince, who will become the next emperor. But there is rather more to this system of magic than it may first appear, in a way that adds good depth to the mythology. And there is quite a bit more to Tarisai herself than anyone expects. Tarisai as a protagonist follows a more typical young adult pattern, but it's a formula that works for me. Her upbringing isolated from any other children has left her craving connection, but it also made her self-reliant, stubborn, and good at keeping her own counsel. One of the things that I loved about this book is that she's not thrown into a nest of vipers and cynical politics. Some of that is happening in the background, but the first step of her mother's plan is for her to earn the trust of the prince in a competition with other potential council members, all of whom are, well, kids. They fight (some), but they also make friends, helped along by the goal and requirement that they join a cooperative council or be sent home. That gives the plot a more collaborative and social feel than one would otherwise expect from the setup. Ifueko does a great job juggling a challenging cast size by focusing on a few kids with whom Tarisai strikes up a friendship but giving the others distinct-enough personalities that their presence is still felt in the story. There are two character dynamics that stand out: Tarisai's relationship with Prince Ekundayo, and her friendship with Sanjeet. The first carries much of the weight of the plot, of course; Tarisai is supposed to gain his trust and then kill him, and the reader will be unsurprised that this takes twists and turns no one expected. But Ifueko, refreshingly, does not reach for the stock plot development of a romance to complicate matters, even though many of the characters expect that. To the contrary, this is a rare story that at least hints at an acknowledgment that some people are not interested in romance at all, and there are other forms that mutual respect can take. Tarisai's relationship with Sanjeet is a different type of depth: two kids with very different histories finding a common understanding in the ways that they were both abused, and create space for each other. It's a great friendship that includes some deeply touching moments. It took me a bit to get into this book, but once Tarisai starts finding her feet and navigating her new relationships, I was engrossed. The story takes a sharp and nasty turn that was hard to read, but Ifueko chooses to turn it into a story of resiliency rather than survival, which makes it much easier to read than it could have been. She also pulls off the kind of plot that complicates and deepens the motives of the obvious villains in a way that gives the story much greater heft, but without disregarding the damage that they have done. I think the plot did fall apart a bit at the end of the book, with too much quick travel and world-building revelations at the cost of development of the relationships that were otherwise at the center of the book, but I'm hoping the sequel will pull those threads back together. And it's so refreshing to read a fantasy novel of this type with a different setting. It's not perfect: Ifueko falls back on Planet of the Hats regional characterization in a few places, and Songland is so obviously Korea that it felt jarring and out of place. Christianity also snuck its nose into the world-building tent near the end in ways that bugged me a bit, although it was subtle enough that I think most readers won't notice. But compared to most fantasy settings, it feels original and fresh. More of this! Ifueko starts this book with a wonderfully memorable dedication:
For the kid scanning fairy tales for a hero with a face like theirs. And for the girls whose stories we compressed into pities and wonders, triumphs and cautions, without asking, even once, for their names.
I think she was successful on both parts of that promise, and it makes for some great reading. Recommended. Followed by Redemptor. Rating: 8 out of 10

3 December 2021

Petter Reinholdtsen: A Brazilian Portuguese translation of the book Made with Creative Commons

A few days ago, a productive translator started working on a new translation of the Made with Creative Commons book for Brazilian Portuguese. The translation take place on the Weblate web based translation system. Once the translation is complete and proof read, we can publish it on paper as well as in PDF, ePub and HTML format. The translation is already 16% complete, and if more people get involved I am conviced it can very quickly reach 100%. If you are interested in helping out with this or other translations of the Made with Creative Commons book, start translating on Weblate. There are partial translations available in Azerbaijani, Bengali, Brazilian Portuguese, Dutch, French, German, Greek, Polish, Simplified Chinese, Swedish, Thai and Ukrainian. The git repository for the book contain all source files needed to build the book for yourself. HTML editions to help with proof reading is also available. As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

24 October 2021

Petter Reinholdtsen: Debian still an excellent choice for Lego builders

The Debian Lego team saw a lot of activity the last few weeks. All the packages under the team umbrella has been updated to fix packaging, lintian issues and BTS reports. In addition, a new and inspiring team member appeared on both the debian-lego-team Team mailing list and IRC channel #debian-lego. If you are interested in Lego CAD design and LEGO Minestorms programming, check out the team wiki page to see what Debian can offer the Lego enthusiast. Patches has been sent upstream, causing new upstream releases, one even the first one in more than ten years, and old upstreams was released with new ones. There are still a lot of work left, and the team welcome more members to help us make sure Debian is the Linux distribution of choice for Lego builders. If you want to contribute, join us in the IRC channel and become part of the team on Salsa. As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

21 October 2021

Lisandro Dami n Nicanor P rez Meyer: CMake toolchain files with Debian's cross compilers

Almost a year ago I added a script made by Helmut Grohne that is able to create a CMake toolchain file pre-filled with Debian-specifics ross compilers. The tool is installed by the cmake package and located at /usr/share/cmake/debtoolchainfilegen. It's usage is simple:
debtoolchainfilegen (arch) > cmake_toolchain_<arch>.cmake
Where $arch can be any of the Debian supported architectures, like arm64 (aka aarch64):
$ /usr/share/cmake/debtoolchainfilegen arm64 > /tmp/cmake_toolchain_aarch64
dpkg-architecture: warning: specified GNU system type aarch64-linux-gnu does not match CC system type x86_64-linux-gnu, try setting a correct CC environment variable
dpkg-architecture: warning: specified GNU system type aarch64-linux-gnu does not match CC system type x86_64-linux-gnu, try setting a correct CC environment variable
$ cat /tmp/cmake_toolchain_aarch64
# Use it while calling CMake:
#   mkdir build; cd build
#   cmake -DCMAKE_TOOLCHAIN_FILE="/path/to/cmake_toolchain_<arch>.cmake" ../
#
set(CMAKE_SYSTEM_NAME "Linux")
set(CMAKE_SYSTEM_PROCESSOR "aarch64")
set(CMAKE_C_COMPILER "aarch64-linux-gnu-gcc")
set(CMAKE_CXX_COMPILER "aarch64-linux-gnu-g++")
set(PKG_CONFIG_EXECUTABLE "aarch64-linux-gnu-pkg-config")
set(PKGCONFIG_EXECUTABLE "aarch64-linux-gnu-pkg-config")
set(QMAKE_EXECUTABLE "aarch64-linux-gnu-qmake")
Note: I kept the warnings, which can be ignored and won't end up on the final file. As you might have noticed the file itself has instructions on how to use it. Of course we will need the requires cross toolchain for the selected arch. For example using arm64:
$ apt install crossbuild-essential-arm64
That's it, we can now start cross building our cmake-based software.

4 August 2021

Petter Reinholdtsen: Mechanic's words in five languages, English, Norwegian and Northern S mi editions

Almost thirty years ago, some forward looking teachers at Samisk videreg ende skole og reindriftsskole teaching metal work and Northern S mi, decided to create a list of words used in Northern S mi metal work. After almost ten years this resulted in a dictionary database, published as the book "Mekanihkk rs nit : Mekanikerord = Mekaanisen alan sanasto = Mechanic's words" in 1999. The story of this work is available from the pen of Svein Lund, one of the leading actors behind this effort. They even got the dictionary approved by the S mi Language Council as the recommended metal work words to use. Fast forward twenty years, I came across this work when I recently became interested in metal work, and started watching educational and funny videos on the topic, like the ones from mrpete222 and This Old Tony. But they all talk English, but I wanted to know what the tools and techniques they used were called in Norwegian. Trying to track down a good dictionary from English to Norwegian, after much searching, I came across the database of words created almost thirty years ago, with translations into English, Norwegian, Northern S mi, Swedish and Finnish. This gave me a lot of the Norwegian phrases I had been looking for. To make it easier for the next person trying to track down a good Norwegian dictionary for the metal worker, and because I knew the person behind the database from my Skolelinux / Debian Edu days, I decided to ask if the database could be released to the public without any usage limitations, in other words as a Creative Commons licensed data set. And happily, after consulting with the S mi Parliament of Norway, the database is now available with the Creative Commons Attribution 4.0 International license from my gitlab repository. The dictionary entries look slightly different, depending on the language in focus. This is the same entry in the different editions. English
lathe
dreiebenk (nb) v rve, v rvenbea ka, jorahanbea ka, v tnanbea ka (se) svarv (sv) sorvi (fi)
Norwegian
dreiebenk
lathe (en) v rve, v rvenbea ka, jorahanbea ka, v tnanbea ka (se) svarv (sv) sorvi (fi)
(nb): sponskj rande bearbeidingsmaskin der ein med skj reverkt y lausgj r spon fr eit roterande arbetsstykke
Northern S mi
v rve, v rvenbea ka, jorahanbea ka, v tnanbea ka
dreiebenk (nb) lathe (en) svarv (sv) sorvi (fi)
(se): ma iidna mainna uohpp vuolahasaid jorri bargo vdnasis
(nb): sponskj rande bearbeidingsmaskin der ein med skj reverkt y lausgj r spon fr eit roterande arbetsstykke
The database included term description in both Norwegian and Northern S mi, but not English. Because of this, the Northern S mi edition include both descriptions, the Norwegian edition include the Norwegian description and the English edition lack a descripiton. Once the database was available without any usage restrictions, and armed with my experience in publishing books, I decided to publish a Norwegian/English dictionary as a book using the database, to make the data set available also on paper and as an ebook. Further into the project, it occurred to me that I could just as easily make an English dictionary, and talking to Svein and concluding that it was within reach, I decided to make a Northern S mi dictionary too. Thus I suddenly find myself publishing a Northern S mi dictionary, even though I do not understand the language myself. I hope it will be well received, and can help revive the impressive work done almost thirty years ago to document the vocabulary of metal workers. If I get some help, I might even extend it with some of the words I find missing, like collet, rotary broach, carbide, knurler, arbor press and others. But the first edition build from a lightly edited version of the original database, with no new entries added. If you would like to check it out, visit my list of published books and consider buying a paper or ebook copy from lulu.com. The paper edition is only available in hardcover to increase its durability in the workshop. I am very happy to report that in the process, and thanks to help from both Svein Lund and B rre Gaup who understand the language, the docbook tools I use to create books, dblatex and docbook-xsl, now include support for Northern S mi. Before I started, these lacked the needed locale settings for this language, but now the patches are included upstream. As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

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