Those were 8th and 9th months working on Debian LTS started by Raphael Hertzog at Freexian. I had trouble resuming work in November as I had taken a long break during the month and started looking at issues only during the last week of November.Imagemagick, again
I have, again, spent a significant amount of time fighting the ImageMagick (IM) codebase. About 15 more vulnerabilities were found since the last upload, which resulted in DLA-756-1. In the advisory, I unfortunately forgot to mention CVE-2016-8677 and CVE-2016-9559, something that was noticed by my colleague Roberto after the upload... More details about the upload are available in the announcement.
When you consider that I worked on IM back in october, which lead to an upload near the end of November covering around 80 more vulnerabilities, it doesn't look good for the project at all. Of the 15 vulnerabilities I worked on, only 6 had CVEs assigned and I had to request CVEs for the other 9 vulnerabilities plus 11 more that were still unassigned. This lead to the assignment of 25 distinct CVE identifiers as a lot of issues were found to be distinct enough to warrant their own CVEs.
One could also question how many of those issues affect the fork, Graphicsmagick. A lot of the vulnerabilities were found through fuzzing searches that may not have been tested on Graphicsmagick. It seems clear to me that a public corpus of test data should be available to test regressions and cross-project vulnerabilities. It's already hard enough to track issues withing IM itself, I can't imagine what it would be for the fork to keep track of those issues, especially since upstream doesn't systematically request CVEs for issues that they find, a questionable practice considering the number of issues we all need to keep track of.Nagios
I have also worked on the Nagios package and produced DLA 751-1 which fixed two fairly major issues (CVE-2016-9565 and CVE-2016-9566) that could allow remote root access under certain conditions. Fortunately, the restricted permissions setup by default in the Debian package made both exploits limited to information disclosure and privilege escalation if the debug log is enabled.
This says a lot about how proper Debian packaging can help in limiting the attack surface of certain vulnerabilities. It was also "interesting" to have to re-learn dpatch to add patches to the package: I regret not converting it to quilt, as the operation is simple and quilt is so much easier to use.
People new to Debian packaging may be curious to learn about the staggering number of patching systems historically used in Debian. On that topic, I started a conversation about how much we want to reuse existing frameworks when we work on those odd packages, and the feedback was interesting. Basically, the answer is "it depends"...NSS
I had already worked on the package in November and continued the work in December. Most of the work was done by Raphael, which fixed a lot of issues with the test suite. I tried to wrap this up by fixing CVE-2016-9074, the build on armel and the test suite. Unfortunately, I had to stop again because I ran out of hours and the fips test suite was still failing, but fortunately Raphael was able to complete the work with DLA-759-1.
For the second time, I forgot to formally assign myself a package before working on it, which meant that I wasted part of my hours working on the monit package. Those hours, of course, were not counted in my regular hours. I still spent some time reviewing mejo's patch to ensure it was done properly and it turned out we both made similar patches working independently, always a good sign.
As I reported in my preliminary November report, I have also triaged issues in libxml2, ntp, openssl and tiff.
Finally, I should mention my short review of the phpMyAdmin upload, among the many posts i sent to the LTS mailing list.Other free software work
One reason why I had so much trouble getting paid work done in November is that I was busy with unpaid work...manpages.debian.org
A major time hole for me was trying to tackle the manpages.debian.org service, which had been offline since August. After a thorough evaluation of the available codebases, I figured the problem space wasn't so hard and it was worth trying to do an implementation from scratch. The result is a tool called debmans.
It took, obviously, way longer than I expected, as I experimented with Python libraries I had been keeping an eye on for a while. For the commanline interface, I used the click library, which is really a breeze to use, but a bit heavy for smaller scripts. For a web search service prototype, I looked at flask, which was also very interesting, as it is light and simple enough to use that I could get started quickly. It also, surprisingly, fares pretty well in the global TechEmpower benchmarking tests. Those interested in those tools may want to look at the source code, in particular the main command (using an interesting pattern itself, __main__.py) and the search prototype.
Debmans is the first project for which I have tried the CII Best Practices Badge program, an interesting questionnaire to review best practices in software engineering. It is an excellent checklist I recommend every project manager and programmer to get familiar with.
I still need to complete my work on Debmans: as I write this, I couldn't get access to the new server the DSA team setup for this purpose. It was a bit of a frustrating experience to wait for all the bits to get into place while I had a product ready to test. In the end, the existing manpages.d.o maintainer decided to deploy the existing codebase on the new server while the necessary dependencies are installed and accesses are granted. There's obviously still a bunch of work to be done for this to be running in production so I have postponed all this work to January.
My hope is that this tool can be reused by other distributions, but after talking with Ubuntu folks, I am not holding my breath: it seems everyone has something that is "good enough" and that they don't want to break it...Monkeysign
I spent a good chunk of time giving a kick in the Monkeysign project, with the 2.2.2 release, which features contributions from two other developers, which may be a record for a single release.
I am especially happy to have adopted a new code of conduct - it has been an interesting process to adapt the code of conduct for such a relatively small project. Monkeysign is becoming a bit of a template on how to do things properly for my Python projects: documentation on readthedocs.org including a code of conduct, support and contribution information, and so on. Even though the code now looks a bit old to me and I am embarrassed to read certain parts, I still think it is a solid project that is useful for a lot of people. I would love to have more time to spend on it.LWN publishing
As you may have noticed if you follow this blog, I have started publishing articles for the LWN magazine, filed here under the lwn tag. It is a way for me to actually get paid for some of my blogging work that used to be done for free. Reports like this one, for example, take up a significant amount of my time and are done without being paid. Converting parts of this work into paid work is part of my recent effort to reduce the amount of time I spend on the computer.
An funny note: I always found the layout of the site to be a bit odd, until I looked at my articles posted there in a different web browser, which didn't have my normal ad blocker configuration. It turns out LWN uses ads, and Google ones too, which surprised me. I definitely didn't want to publish my work under banner ads, and will never do so on this blog. But it seems fair that, since I get paid for this work, there is some sort of revenue stream associated with it. If you prefer to see my work without ads, you can wait for it to be published here or become a subscriber which allows you to get rid of the ads on the site.
My experience with LWN is great: they're great folks, and very supportive. It's my first experience with a real editor and it really pushed me in improving my writing to make better articles that I normally would here. Thanks to the LWN folks for their support! Expect more of those quality articles in 2017.Debian packaging
I have added a few packages to the Debian archive:
- magic-wormhole: easy file-transfer tool, co-maintained with Jamie Rollins
- slop: screenshot tool
- xininfo: utility used by teiler
- teiler (currently in NEW): GUI for screenshot and screencast tools
Against my better judgment, I worked again on the borg project. This time I tried to improve the documentation, after a friend asked me for help on "how to make a quick backup". I realized I didn't have any good primer to send regular, non-sysadmin users to and figured that, instead of writing a new one, I could improve the upstream documentation instead.
I generated a surprising 18 commits of documentation during that time, mainly to fix display issues and streamline the documentation. My final attempt at refactoring the docs eventually failed, unfortunately, again reminding me of the difficulty I have in collaborating on that project. I am not sure I succeeded in making the project more attractive to non-technical users, but maybe that's okay too: borg is a fairly advanced project and not currently aimed at such a public. This is yet another project I am thinking of creating: a metabackup program like backupninja that would implement the vision created by liw in his A vision for backups in Debian post, which was discarded by the Borg project.
Github also tells me that I have opened 19 issues in 14 different repositories in November. I would like to particularly bring your attention to the linkchecker project which seems to be dead upstream and for which I am looking for collaborators in order to create a healthy fork.
Finally, I started on reviving the stressant project and changing all my passwords, stay tuned for more!
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The Debian project is looking at possibly making automatic minor upgrades to installed packages the default for newly installed systems. While Debian has a reliable and stable package update system that has been an inspiration for multiple operating systems (the venerable APT), upgrades are, usually, a manual process on Debian for most users.
The proposal was brought up during the Debian Cloud sprint in November by longtime Debian Developer Steve McIntyre. The rationale was to make sure that users installing Debian in the cloud have a "secure" experience by default, by installing and configuring the unattended-upgrades package within the images. The unattended-upgrades package contains a Python program that automatically performs any pending upgrade and is designed to run unattended. It is roughly the equivalent of doing apt-get update; apt-get upgrade in a cron job, but has special code to handle error conditions, warn about reboots, and selectively upgrade packages. The package was originally written for Ubuntu by Michael Vogt, a longtime Debian developer and Canonical employee.
Since there was a concern that Debian cloud images would be different from normal Debian installs, McIntyre suggested installing unattended-upgrades by default on all Debian installs, so that people have a consistent experience inside and outside of the cloud. The discussion that followed was interesting as it brought up key issues one would have when deploying automated upgrade tools, outlining both the benefits and downsides to such systems.Problems with automated upgrades
An issue raised in the following discussion is that automated upgrades may create unscheduled downtime for critical services. For example, certain sites may not be willing to tolerate a master MySQL server rebooting in conditions not controlled by the administrators. The consensus seems to be that experienced administrators will be able to solve this issue on their own, or are already doing so.
For example, Noah Meyerhans, a Debian developer, argued that "any reasonably well managed production host is going to be driven by some kind of configuration management system" where competent administrators can override the defaults. Debian, for example, provides the policy-rc.d mechanism to disable service restarts on certain packages out of the box. unattended-upgrades also features a way to disable upgrades on specific packages that administrators would consider too sensitive to restart automatically and will want to schedule during maintenance windows.
Reboots were another issue discussed: how and when to deploy kernel upgrades? Automating kernel upgrades may mean data loss if the reboot happens during a critical operation. On Debian systems, the kernel upgrade mechanisms already provide a /var/run/reboot-required flag file that tools can monitor to notify users of the required reboot. For example, some desktop environments will popup a warning prompting users to reboot when the file exists. Debian doesn't currently feature an equivalent warning for command-line operation: Vogt suggested that the warning could be shown along with the usual /etc/motd announcement.
The ideal solution here, of course, is reboot-less kernel upgrades, which is also known as "live patching" the kernel. Unfortunately, this area is still in development in the kernel (as was previously discussed here). Canonical deployed the feature for the Ubuntu 16.04 LTS release, but Debian doesn't yet have such capability, since it requires extra infrastructure among other issues.
Furthermore, system reboots are only one part of the problem. Currently, upgrading packages only replaces the code and restarts the primary service shipped with a given package. On library upgrades, however, dependent services may not necessarily notice and will keep running with older, possibly vulnerable, libraries. While libc6, in Debian, has special code to restart dependent services, other libraries like libssl do not notify dependent services that they need to restart to benefit from potentially critical security fixes.
One solution to this is the needrestart package which inspects all running processes and restarts services as necessary. It also covers interpreted code, specifically Ruby, Python, and Perl. In my experience, however, it can take up to a minute to inspect all processes, which degrades the interactivity of the usually satisfying apt-get install process. Nevertheless, it seems like needrestart is a key component of a properly deployed automated upgrade system.Benefits of automated upgrades
One thing that was less discussed is the actual benefit of automating upgrades. It is merely described as "secure by default" by McIntyre in the proposal, but no one actually expanded on this much. For me, however, it is now obvious that any out-of-date system will be systematically attacked by automated probes and may be taken over to the detriment of the whole internet community, as we are seeing with Internet of Things devices. As Debian Developer Lars Wirzenius said:
The ecosystem-wide security benefits of having Debian systems keep up to date with security updates by default overweigh any inconvenience of having to tweak system configuration on hosts where the automatic updates are problematic.
One could compare automated upgrades with backups: if they are not automated, they do not exist and you will run into trouble without them. (Wirzenius, coincidentally, also works on the Obnam backup software.)
Another benefit that may be less obvious is the acceleration of the feedback loop between developers and users: developers like to know quickly when an update creates a regression. Automation does create the risk of a bad update affecting more users, but this issue is already present, to a lesser extent, with manual updates. And the same solution applies: have a staging area for security upgrades, the same way updates to Debian stable are first proposed before shipping a point release. This doesn't have to be limited to stable security updates either: more adventurous users could follow rolling distributions like Debian testing or unstable with unattended upgrades as well, with all the risks and benefits that implies.Possible non-issues
That there was not a backlash against the proposal surprised me: I expected the privacy-sensitive Debian community to react negatively to another "phone home" system as it did with the Django proposal. This, however, is different than a phone home system: it merely leaks package lists and one has to leak that information to get the updated packages. Furthermore, privacy-sensitive administrators can use APT over Tor to fetch packages. In addition, the diversity of the mirror infrastructure makes it difficult for a single entity to profile users.
Automated upgrades do imply a culture change, however: administrators approve changes only a posteriori as opposed to deliberately deciding to upgrade parts they chose. I remember a time when I had to maintain proprietary operating systems and was reluctant to enable automated upgrades: such changes could mean degraded functionality or additional spyware. However, this is the free-software world and upgrades generally come with bug fixes and new features, not additional restrictions.Automating major upgrades?
While automating minor upgrades is one part of the solution to the problem of security maintenance, the other is how to deal with major upgrades. Once a release becomes unsupported, security issues may come up and affect older software. While Debian LTS extends releases lifetimes significantly, it merely delays the inevitable major upgrades. In the grand scheme of things, the lifetimes of Linux systems (Debian: 3-5 years, Ubuntu: 1-5 years) versus other operating systems (Solaris: 10-15 years, Windows: 10+ years) is fairly short, which makes major upgrades especially critical.
While major upgrades are not currently automated in Debian, they are usually pretty simple: edit sources.list then:# apt-get update && apt-get dist-upgrade
But the actual upgrade process is really much more complex. If you run into problems with the above commands, you will quickly learn that you should have followed the release notes, a whopping 20,000-word, ten-section document that outlines all the gory details of the release. This is a real issue for large deployments and for users unfamiliar with the command line.
The solutions most administrators seem to use right now is to roll their own automated upgrade process. For example, the Debian.org system administrators have their own process for the "jessie" (8.0) upgrade. I have also written a specification of how major upgrades could be automated that attempts to take into account the wide variety of corner cases that occur during major upgrades, but it is currently at the design stage. Therefore, this problem space is generally unaddressed in Debian: Ubuntu does have a do-release-upgrade command but it is Ubuntu-specific and would need significant changes in order to work in Debian.Future work
Ubuntu currently defaults to "no automation" but, on install, invites users to enable unattended-upgrades or Landscape, a proprietary system-management service from Canonical. According to Vogt, the company supports both projects equally as they differ in scope: unattended-upgrades just upgrades packages while Landscape aims at maintaining thousands of machines and handles user management, release upgrades, statistics, and aggregation.
It appears that Debian will enable unattended-upgrades on the images built for the cloud by default. For regular installs, the consensus that has emerged points at the Debian installer prompting users to ask if they want to disable the feature as well. One reason why this was not enabled before is that unattended-upgrades had serious bugs in the past that made it less attractive. For example, it would simply fail to follow security updates, a major bug that was fortunately promptly fixed by the maintainer.
In any case, it is important to distribute security and major upgrades on Debian machines in a timely manner. In my long experience in professionally administering Unix server farms, I have found the upgrade work to be a critical but time-consuming part of my work. During that time, I successfully deployed an automated upgrade system all the way back to Debian woody, using the simpler cron-apt. This approach is, unfortunately, a little brittle and non-standard; it doesn't address the need of automating major upgrades, for which I had to revert to tools like cluster-ssh or more specialized configuration management tools like Puppet. I therefore encourage any effort towards improving that process for the whole community.
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