We are thrilled to announce a new big RcppArmadillo release! Conrad recently moved Armadillo to the 8.* series, with significant improvements and speed ups for sparse matrix operations, and more. See below for a brief summary. This also required some changes at our end which Binxiang Ni provided, and Serguei Sokol improved some instantiations. We now show the new vignette Binxiang Ni wrote for his GSoC contribution, and I converted it (and the other main vignette) to using the pinp package for sleeker pdf vignettes. This release resumes our bi-monthly CRAN release cycle. I may make interim updates available at GitHub "as needed". And this time I managed to mess up the reverse depends testing, and missed one sync() call on the way back to R---but all that is now taken care of. Armadillo is a powerful and expressive C++ template library for linear algebra aiming towards a good balance between speed and ease of use with a syntax deliberately close to a Matlab. RcppArmadillo integrates this library with the R environment and language--and is widely used by (currently) 405 other packages on CRAN. A high-level summary of changes follows.

Changes in RcppArmadillo version 0.8.100.1.0 (2017-10-05)

• Upgraded to Armadillo release 8.100.1 (Feral Pursuits)
  • faster incremental construction of sparse matrices via element access operators
  • faster diagonal views in sparse matrices
  • expanded SpMat to save/load sparse matrices in coord format
  • expanded .save(),.load() to allow specification of datasets within HDF5 files
  • added affmul() to simplify application of affine transformations
  • warnings and errors are now printed by default to the std::cerr stream
  • added set_cerr_stream() and get_cerr_stream() to replace set_stream_err1(), set_stream_err2(), get_stream_err1(), get_stream_err2()
  • new configuration options ARMA_COUT_STREAM and ARMA_CERR_STREAM
• Constructors for sparse matrices of types dgt, dtt amd dst now use Armadillo code for improved performance (Serguei Sokol in #175 addressing #173)
• Sparse matrices call .sync() before accessing internal arrays (Binxiang Ni in #171)
• The sparse matrix vignette has been converted to Rmarkdown using the pinp package, and is now correctly indexed. (#176)

Courtesy of CRANberries, there is a diffstat report. More detailed information is on the RcppArmadillo page. Questions, comments etc should go to the rcpp-devel mailing list off the R-Forge page.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. Please report excessive re-aggregation in third-party for-profit settings.

It feels like the past week or two has been very busy, and so I'm looking forward to my "holiday" next month. I'm not really having a holiday of course, my wife is slowly returning to work, so I'll be taking a month of paternity leave, taking sole care of Oiva for the month of November. He's still a little angel, and now that he's reached 10 months old he's starting to get much more mobile - he's on the verge of walking, but not quite there yet. Mostly that means he wants you to hold his hands so that he can stand up, swaying back and forth before the inevitable collapse. Beyond spending most of my evenings taking care of him, from the moment I return from work to his bedtime (around 7:30PM), I've made the Debian Administration website both read-only and much simpler. In the past that site was powered by a lot of servers, I think around 11. Now it has only a small number of machines, which should slowly decrease. I've ripped out the database host, the redis host, the events-server, the planet-machine, the email-box, etc. Now we have a much simpler setup:

• Front-end machine
  • Directly serves the code site
  • Directly serves the SSL site which exists solely for Let's Encrypt
  • Runs HAProxy to route the rest of the requests to the cluster.
• 4 x Apache servers
  • Each one has a (read-only) MySQL database on it for the content.
    • In case of future-compromise I removed all user passwords, and scrambled the email-addresses.
    • I don't think there's a huge risk, but better safe than sorry.
  • Each one runs the web-application.
    • Which now caches each generated page to /tmp/x/x/x/x/$hash if it doesn't exist.
    • If the request is cached it is served from that cache rather than dynamically.

Finally although I'm slowly making progress with "radio stuff" I've knocked up a simple hack which uses an ultrasonic sensor to determine whether I'm sat in front of my (home) PC. If I am everything is good. If I'm absent the music is stopped and the screen locked. Kinda neat. (Simple ESP8266 device wired to the sensor. When the state changes a message is posted to Mosquitto, where a listener reacts to the change(s).) Oh, not final. I've also transfered my mobile phone from DNA.fi to MoiMobile. Which should complete soon, right now my phone is in limbo, active on niether service. Oops.

During a long era, electronic mail was the main communication tool for enterprises. Slack, which offer public or private group discussion boards and instant messaging between two people, challenge its position, especially in the IT industry. Not only Slack has features known and used since IRC launch in the late 80s, but Slack also offers file sending and sharing, code quoting, and it indexing for ulterior searches everything that goes through the application. Slack is also modular with numerous plug-in to easily add new features. Using the Software-As-A-Service (SAAS) model, Slack basic version is free, and users pay for options. Slack is now considered by the Github generation like the new main enterprise communication tool. As I did in my previous article on the Github threat, this one won t promote Slask s advantages, as many other articles have already covered all these points ad nauseam, but to show the other side and to warn the companies using this service about its inherent risks. So far, these risks have been ignored, sometimes voluntary in the name of the It works ideology. Neglecting all economic and safety consideration, neglecting all threat to privacy and individual freedom. We ll see about them below. All your company communication since its creation When a start-up chooses Slack, all of its internal communication will be stored by Slack. When someone uses this service, the simple fact to chat through it means that the whole communication is archived. One may point that within the basic Slack offer, only the last 10.000 messages can be read and searched. Bad argument. Slack stored every message and every file shared as it pleases. We ll see below this application behavior is of capital importance in the Slack threat to enterprises. And the problem is the same for all other companies which choose Slack at one point or another. If they replace their traditional communication method with it, Slack will have access to capital data, not only in volume, but also because of their value for the company itself Or anyone interested in this company life. Search Your Entire Archive One of the main arguments to use Slack is its Search your entire archive feature. One can search almost anything one can think of. Why? Because everything is indexed. Your team chat archive or the more or less confidential documents exchanged with the accountant department; everything is in it in order to provide the most effective search tool. We can t deny it s a very attractive feature for everyone inside the company. But it is also a very attractive feature for everyone outside of the company who would want to know more about its internal life. Even more if you re looking for a specific subject. If Slack is the main communication tool of your company, and if as I ve experienced in my professional life, some teams prefer to use it than to go to the office next door or even bug you to put the information on the dedicated channel, one can easily deduce that nothing in this type of company escape Slack. The automatic indexation and the search feature efficiency are excellent tools to get all the information needed, in quantity and in quality. As such, it s a great social engineering tool for everyone who has access to it, with a history as old as the use of Slack as a communication tool in the company. Across borders And Beyond! Slack is a Web service which uses mainly Amazon Web services and most specially Cloudfront, as stated by the available information on Slack infrastructure. Even without a complete study of said infrastructure, it s easy to state that all the data regarding many innovative global companies around the world (and some of them including for all their internal communication since their creation) are located in the United States, or at least in the hands of a US company, which must follow US laws, a country with a well-known history of large scale industrial espionage, as the whistleblower Edward Snowden demonstrated it in 2013 and where company data access has no restriction under the Patriot Act, as in the Microsoft case (2014) where data stored in Ireland by the Redmond software editor have been given to US authorities. As such, Slack s automatic indexation and search tool are a boon for anyone spy agency or hacker which get authorized access to it. To trust a third party with all, or at least most of, your internal corporate communication is a certain risk for your company if the said third party doesn t follow the same regulations as yours or if it has different interests, from a data security point of view or more globally on its competitiveness. A badly timed data leak can be catastrophic. What s the point of secretly preparing a new product launch or an aggressive takeover if all your recent Slack conversations have leaked, including your secret plans? What if Slack is hacked? First let s remember that even if a cyber attack may appear as a rare or hypothetical scenario to a badly informed and hurried manager, it is far from being as rare as she or he believes it (or wants to believe it). Infrastructure hacking is quite common, as a regular visit to Hacker News will give you multiple evidence. And Slack itself has already been hacked. February 2015: Slack is the victim during four days of a cyber attack, which was made public by the company in March. Officially, the unauthorized access was limited to information on the users profiles. It is impossible to measure exactly what and who was impacted by this attack. In a recent announcement, Yahoo confessed that these 3 billion accounts (you ve read well: 3 billions) were compromised late 2014! Officially, Slack stated that No financial or payment information was accessed or compromised in this attack. Which is, and by far, the least interesting of all data stored within Slack! With company internal communication indexed sometimes from the very beginning of said company and searchable, Slack may be a potential target for cybercriminal not looking for its users financial credentials but more their internal data already in a usable format. One can imagine Slack must give information on a massive data leak, which can t be ignored. But what would happen if only one Slack user is the victim of said leak? The Free Alternative Solutions As we demonstrated above, companies need to find an alternative solution to Slack, one they can host themselves to reduce data leaks and industrial espionage and dependency on the Internet connection. Luckily, Slack success created its own copycats, some of them being also free software. Rocket.chat is one of them. Its comprehensive service offers chat rooms, direct messages and file sharing but also videoconferencing and screen sharing, and even most features. Check their dedicated page. You can also try an online demo. And even more, Rocket Chat has a very simple extension system and an API. Mattermost is another service which has the advantages of proximity and of compatibility with Slack. It offers numerous features including the main expected by this type of software. It also offers numerous apps and plug-ins to interact with online services, software forges, and continuous integration tools. It works In the introduction, we discussed the It works effect, usually invoked to dispel any arguments about data protection and exchange confidentiality we discussed in this article. True, one single developer can ask: why worry about it? All I want is to chat with my colleagues and send files! Because Slack service subscription in the long term put the company continuously at risk. Maybe it s not the employees place to worry about it, they just have to do their job the more efficiently possible. On the other side, the company management, usually non-technical, may not be aware of what risks will threaten their company with this technical choice. The technical management may pretend to be omniscient, nobody is fooled. Either someone from the direction will ask the right question (where are our data and who can access them?) or someone from the technical side alert them officially on these problems. This is this technical audience, even if not always heard by their direction, which is the target of this article. May they find in it the right arguments to be convincing. We hope that the several points we developed in this article will help you to make the right choice. About Me Carl Chenet, Free Software Indie Hacker, founder of the French-speaking Hacker News-like Journal du hacker. Follow me on social networks

• My Mastodon account : @carlchenet
• My Diaspora* account : @carlchenet
• My Twitter account : @carl_chenet

Translated from French by St phanie Chaptal. Original article written in October 2016.

A long time ago, I switched my GnuPG setup to a smartcard based one. I kept using the same master key, but:

• copied the rsa4096 master key to a master smartcard, for when I need to sign (certify) other keys;
• created rsa2048 subkeys (for signature, encryption and authentication) and moved them to an OpenPGP smartcard for daily usage.

I've been working with that setup for a few years now and it is working perfectly fine. The signature counter on the OpenPGP basic card is a bit north of 5000 which is large but not that huge, all considered (and not counting authentication and decryption key usage).

One very nice feature of using a smartcard is that my laptop (or other machines I work on) never manipulates the private key directly but only sends request to the card, which is a really huge improvement, in my opinion. But it's also not the perfect solution for me: the OpenPGP card uses a proprietary platform from ZeitControl, named BasicCard. We have very few information on the smartcard, besides the fact that Werner Koch trust ZeistControl to not mess up. One caveat for me is that the card does not use a certified secure microcontroler like you would find in smartcard chips found in debit card or electronic IDs. That means it's not really been audited by a competent hardware lab, and thus can't be considered secure against physical attacks. The cardOS software and the application implementing the OpenPGP specification are not public either and have not been audited either, to the best of my knowledge.

At one point I was interested in the Yubikey Neo, especially since the architecture Yubico used was common: a (supposedly) certified platform (secure microcontroler, card OS) and a GlobalPlatform / JavaCard virtual machine. The applet used in the Yubikey Neo is open-source, too, so you could take a look at it and identify any issue.

Unfortunately, Yubico transitioned to a less common and more proprietary infrastructure for Yubikey 4: it's not longer Javacard based, and they don't provide the applet source anymore. This was not really seen as a good move by a lot of people, including Konstantin Ryabitsev (kernel.org administrator). Also, it wasn't possible even for the Yubico Neo to actually build the applet yourself and inject it on the card: when the Yubikey leaves the facility, the applet is already installed and the smartcard is locked (for obvious security reason). I've tried asking about getting naked/empty Yubikey with developers keys to load the applet myself, but it' was apparently not possible or would have required signing an NDA with NXP (the chip maker), which is not really possible as an individual (not that I really want to anyway).

In the meantime, a coworker actually wrote an OpenPGP javacard applet, with the intention to support latest version of the OpenPGP specification, and especially elliptic curve cryptography. The applet is called SmartPGP and has been released on ANSSI github repository. I investigated a bit, and found a smartcard with correct specification: certified (in France or Germany), and supporting Javacard 3.0.4 (required for ECC). The card can do RSA2048 (unfortunately not RSA4096) and EC with NIST (secp256r1, secp384r1, secp521r1) and Brainpool (P256, P384, P512) curves.

I've ordered some cards, and when they arrived started playing. I've built the SmartPGP applet and pushed it to a smartcard, then generated some keys and tried with GnuPG. I'm right now in the process of migrating to a new smartcard based on that setup, which seems to work just fine after few days.

Part two of this serie will describe how to build the applet and inject it in the smartcard. The process is already documented here and there, but there are few things not to forget, like how to lock the card after provisionning, so I guess having the complete process somewhere might be useful in case some people want to reproduce it.

The @TorAtlas web application will now also prompt operators to update their relays if they are outdated. pic.twitter.com/HMixwqbBKM Tor Atlas (@TorAtlas) October 9, 2017

We have instructions for setting up new Tor relays on Debian. The only time the word upgrade is mentioned here is:

Be sure to set your ContactInfo line so we can contact you if you need to upgrade or something goes wrong.

This isn t great. We should have some decent instructions for keeping your relay up to date too. I ve been compiling a set of documentation for enabling automatic updates on various Linux distributions, here s a taste of what I have so far:

---

Debian Make sure that unattended-upgrades is installed and then enable the installation of updates (as root):

apt install unattended-upgrades
dpkg-reconfigure -plow unattended-upgrades

Fedora 22 or later Beginning with Fedora 22, you can enable automatic updates via:

dnf install dnf-automatic

In /etc/dnf/automatic.conf set:

apply_updates = yes

Now enable and start automatic updates via:

systemctl enable dnf-automatic.timer
systemctl start dnf-automatic.timer

(Thanks to Enrico Zini I know all about these timer units in systemd now.)

RHEL or CentOS For CentOS, RHEL, and older versions of Fedora, the yum-cron package is the preferred approach:

yum install yum-cron

In /etc/yum/yum-cron.conf set:

apply_updates = yes

Enable and start automatic updates via:

systemctl start yum-cron.service

---

I d like to collect together instructions also for other distributions (and *BSD and Mac OS). Atlas knows which platform a relay is running on, so there could be a link in the future to some platform specific instructions on how to keep your relay up to date.

GDPR is a new EU regulation for privacy. The name is short for "General Data Protection Regulation" and it covers all organisations that handle personal data of EU citizens and EU residents. It will become enforceable May 25, 2018 (Towel Day). This will affect Debian. I think it's time for Debian to start working on compliance, mainly because the GDPR requires sensible things. I'm not an expert on GDPR legislation, but here's my understanding of what we in Debian should do:

• do a privacy impact assessment, to review and document what data we have, and collect, and what risks that has for the people whose personal data it is if the data leaks
• only collect personal information for specific purposes, and only use the data for those purposes
• get explicit consent from each person for all collection and use of their personal information; archive this consent (e.g., list subscription confirmations)
• allow each person to get a copy of all the personal information we have about them, in a portable manner, and let them correct it if it's wrong
• allow people to have their personal information erased
• maybe appoint one or more data protection officers (not sure this is required for Debian)

There's more, but let's start with those. I think Debian has at least the following systems that will need to be reviewed with regards to the GDPR:

• db.debian.org - Debian project members, "Debian developers"
• nm.debian.org
• contributors.debian.org
• lists.debian.org - at least membership lists, maybe archives
• possibly irc servers and log files
• mail server log files
• web server log files
• version control services and repositories

There may be more; these are just off the top of my head. I expect that mostly Debian will be OK, but we can't just assume that.

Here's what happened in the Reproducible Builds effort between Sunday October 1 and Saturday October 7 2017: Media coverage

• Bernhard sent another report about the status of Reproducible openSUSE. They currently they are at 478 unreproducible and 11,111 reproducible packages out of 11,821, so also at 93%!
• Holger attempted to get a Reproducible Builds devroom at FOSDEM 2018 but sadly this proposal was not accepted.

Documentation updates

• Christoph Berg created a wiki page about Openjade generated timestamps from DSSSL stylesheets.

Packages reviewed and fixed, and bugs filed

• Bernhard M. Wiedemann:
  • LiE uninitialized memory (need to find upstream)
  • chrony date (merged)
• Chris Lamb:
  • #877375 filed against polygen.
  • #877381 filed against plr.
  • #877384 filed against rcs.
  • #877928 filed against cadvisor.
• jathan:
  • #877470 filed against bsh.

Reviews of unreproducible packages 32 package reviews have been added, 46 have been updated and 62 have been removed in this week, adding to our knowledge about identified issues. Weekly QA work During our reproducibility testing, FTBFS bugs have been detected and reported by:

• Adrian Bunk (27)

diffoscope development

• Chris Lamb:
  • Don't crash on malformed md5sums files. (Closes: #877473)
  • Improve names in output of "internal" binwalk members. (Closes: #877525)
• Mattia Rizzolo:
  • Fix test compatibility with dtb version 1.4.5

strip-nondeterminism development Rob Browning noticed that strip-nondeterminism was causing serious performance regressions in the Clojure programming language within Debian. After some discussion, Chris Lamb also posted a query to debian-devel in case there were any other programming languages that might be suffering from the same problem.

• Chris Lamb:
  • jar.pm: Clojure considers the .class file to be stale if it shares the same timestamp of the .clj. We thus adjust the timestamps of the .clj to always be younger.. (Closes: #877418)
  • jar.pm, zip.pm: Allow $options member_normalizer callback to support specifying the timestamp.
  • zip.pm: Ensure that we don't try and write an old timestamp; Archive::Zip will do this anyway, just noisily.
  • zip.pm: Calculate the target canonical time in just one place.
  • bin/strip-nondeterminism: Print a warning in --verbose mode if no canonical time specified.
  • jar.pm: Update comment to reflect that NTFS/FAT has a 2s timestamp granularity.
  • jar.pm: s/NTFS/FAT/. Thanks to James Ross.

reprotest development Versions 0.7.1 and 0.7.2 were uploaded to unstable by Ximin Luo:

• New features:
  • Add a --auto-build option to try to determine which specific variations cause unreproducibility.
  • Add a --source-pattern option to restrict copying of source_root, and set this automatically in our presets.
• Usability improvements:
  • Improve error messages in some common scenarios.
    • Fiving a source_root or build_command that doesn't exist
    • Using reprotest with default settings after not installing Recommends
  • Output hashes after a successful --auto-build.
  • Print a warning message if we reproduced successfully but didn't vary everything.
• Fix varying both umask and user_group at the same time.
• Have dpkg-source extract to different build dir if varying the build-path.
• Pass --exclude-directory-metadata to diffoscope(1) by default as this is the majority use-case.
• Various bug fixes to get the basic dsc+schroot example working.

It included contributions already covered by posts of the previous weeks, as well as new ones from:

• Ximin Luo:
  • main: Add a --env-build option for testing different env vars
  • Don't output spurious warnings in tests
  • Add some more notes on the remaining variations
  • Fix the help text for virtual servers

tests.reproducible-builds.org

• Mattia Rizzolo:
  • Re-deploy odxu4a after being reinstalled and renamed from odxu4.
• Vagrant Cascadian:
  • Rename armhf host odxu4 to odxu4a

Misc. This week's edition was written by Bernhard M. Wiedemann, Chris Lamb, Holger Levsen, Mattia Rizzolo & reviewed by a bunch of Reproducible Builds folks on IRC & the mailing lists.

Welcome to gambaru.de. Here is my monthly report that covers what I have been doing for Debian. If you re interested in Java, Games and LTS topics, this might be interesting for you. Debian Games

• I sponsored a new release of hexalate for Unit193 and icebreaker for Andreas Gnau. The latter is a reintroduction.
• New upstream releases this month: freeorion and hyperrogue.
• I backported freeciv and freeorion to Stretch.

Debian Java

• New upstream releases and one update: sweethome3d, sweethome3d-furniture, sweethome3d-furniture-editor, sweethome3d-textures-editor (update), libsambox-java, libsejda-java, pdfsam, easymock, jboss-modules, jboss-xnio and undertow.
• I fixed one RC bug in libsejda-io-java (#874494) and investigated another one (#869266) in commons-httpclient which could be closed.
• The new build-dependencies of jboss-xnio, wildfly-client-config and wildfly-common, were accepted into the archive this month.
• I spent some quality time on fixing #874579 in libhibernate-validator-java. This was the last blocking bug for pdfsam which I could finally upload to unstable. It s a really great JavaFX application. Check it out!
• I sponsored another update of libimglib2-java for Ghislain Vaillant and simplyhtml, freeplane and knopflerfish-osgi for Felix Natter.
• I also fixed RC bug #871348 in robocode, a Java programming game and #871347 in tycho.

Debian LTS This was my nineteenth month as a paid contributor and I have been paid to work 15,75 hours on Debian LTS, a project started by Rapha l Hertzog. In that time I did the following:

• From 18. September to 24. September I was in charge of our LTS frontdesk. I triaged bugs in poppler, binutils, kannel, wordpress, libsndfile, libexif, nautilus, libstruts1.2-java, nvidia-graphics-drivers, p3scan, otrs2 and glassfish.
• DLA-1108-1. Issued a security update for tomcat7 fixing 1 CVE.
• DLA-1116-1. Issued a security update for poppler fixing 3 CVE.
• DLA-1119-1. Issued a security update for otrs2 fixing 4 CVE.
• DLA-1122-1. Issued a security update for asterisk fixing 1 CVE. I also investigated CVE-2017-14099 and CVE-2017-14603. I decided against a backport because the fix was too intrusive and the vulnerable option is disabled by default in Wheezy s version which makes it a minor issue for most users.
• I submitted a patch for Debian s reportbug tool. (#878088) During our LTS BoF at DebConf 17 we came to the conclusion that we should implement a feature in reportbug that checks whether the bug reporter wants to report a regression for a recent security update. Usually the LTS and security teams receive word from the maintainer or users who report issues directly to our mailing lists or IRC channels. However in some cases we were not informed about possible regressions and the new feature in reportbug shall ensure that we can respond faster to such reports.
• I started to investigate the open security issues in wordpress and will complete the work in October.

Misc

• I packaged a new version of xarchiver. Thanks to the work of Ingo Br ckl xarchiver can handle almost all archive formats in Debian now.

QA upload

• I did a QA upload of xball, an ancient game from the 90ies that simulates bouncing balls. It should be ready for another decade at least.

Thanks for reading and see you next time.

Introduction pristine-tar is a tool that is present in the workflow of a lot of Debian people. I adopted it last year after it has been orphaned by its creator Joey Hess. A little after that Tomasz Buchert joined me and we are now a functional two-person team. pristine-tar goals are to import the content of a pristine upstream tarball into a VCS repository, and being able to later reconstruct that exact same tarball, bit by bit, based on the contents in the VCS, so we don t have to store a full copy of that tarball. This is done by storing a binary delta files which can be used to reconstruct the original tarball from a tarball produced with the contents of the VCS. Ultimately, we want to make sure that the tarball that is uploaded to Debian is exactly the same as the one that has been downloaded from upstream, without having to keep a full copy of it around if all of its contents is already extracted in the VCS anyway. The current state of the art, and perspectives for the future pristine-tar solves a wicked problem, because our ability to reconstruct the original tarball is affected by changes in the behavior of tar and of all of the compression tools (gzip, bzip2, xz) and by what exact options were used when creating the original tarballs. Because of this, pristine-tar currently has a few embedded copies of old versions of compressors to be able to reconstruct tarballs produced by them, and also rely on a ever-evolving patch to tar that is been carried in Debian for a while. So basically keeping pristine-tar working is a game of Whac-A-Mole. Joey provided a good summary of the situation when he orphaned pristine-tar. Going forward, we may need to rely on other ways of ensuring integrity of upstream source code. That could take the form of signed git tags, signed uncompressed tarballs (so that the compression doesn t matter), or maybe even a different system for storing actual tarballs. Debian bug #871806 contains an interesting discussion on this topic. Recent improvements Even if keeping pristine-tar useful in the long term will be hard, too much of Debian work currently relies on it, so we can t just abandon it. Instead, we keep figuring out ways to improve. And I have good news: pristine-tar has recently received updates that improve the situation quite a bit. In order to be able to understand how better we are getting at it, I created a "visualization of the regression test suite results. With the help of data from there, let s look at the improvements made since pristine-tar 1.38, which was the version included in stretch. pristine-tar 1.39: xdelta3 by default. This was the first release made after the stretch release, and made xdelta3 the default delta generator for newly-imported tarballs. Existing tarballs with deltas produced by xdelta are still supported, this only affects new imports. The support for having multiple delta generator was written by Tomasz, and was already there since 1.35, but we decided to only flip the switch after using xdelta3 was supported in a stable release. pristine-tar 1.40: improved compression heuristics pristine-tar uses a few heuristics to produce the smaller delta possible, and this includes trying different compression options. In the release Tomasz included a contribution by Lennart Sorensen to also try the --gnu, which gretly improved the support for rsyncable gzip compressed files. We can see an example of the type of improvement we got in the regression test suite data for delta sizes for faad2_2.6.1.orig.tar.gz: pristine-tar 1.41: support for signatures This release saw the addition of support for storage and retrieval of upstream signatures, contributed by Chris Lamb. pristine-tar 1.42: optionally recompressing tarballs I had this idea and wanted to try it out: most of our problems reproducing tarballs come from tarballs produced with old compressors, or from changes in compressor behavior, or from uncommon compression options being used. What if we could just recompress the tarballs before importing then? Yes, this kind of breaks the pristine bit of the whole business, but on the other hand, 1) the contents of the tarball are not affected, and 2) even if the initial tarball is not bit by bit the same that upstream release, at least future uploads of that same upstream version with Debian revisions can be regenerated just fine. In some cases, as the case for the test tarball util-linux_2.30.1.orig.tar.xz, recompressing is what makes it possible to reproduce the tarball (and thus import it with pristine-tar) possible at all: In other cases, if the current heuristics can t produce a reasonably small delta, recompressing makes a huge difference. It s the case for mumble_1.1.8.orig.tar.gz: Recompressing is not enabled by default, and can be enabled by passing the --recompress option. If you are using pristine-tar via a wrapper tool like gbp-buildpackage, you can use the $PRISTINE_TAR environment variable to set options that will affect any pristine-tar invocations. Also, even if you enable recompression, pristine-tar will only try it if the delta generations fails completely, of if the delta produced from the original tarball is too large. You can control what too large means by using the --recompress-threshold-bytes and --recompress-threshold-percent options. See the pristine-tar(1) manual page for details.

I am very, very, very happy to report this And I cannot believe we have achieved this so fast: Back in June, I announced I'd start working on the translation of the Made with Creative Commons book into Spanish. Over the following few weeks, I worked out the most viable infrastructure, gathered input and commitments for help from a couple of friends, submitted my project for inclusion in the Hosted Weblate translations site (and got it approved!) Then, we quietly and slowly started working. Then, as it usually happens in late August, early September... The rush of the semester caught me in full, and I left this translation project for later For the next semester, perhaps... Today, I received a mail that surprised me. That stunned me. 99% of translated strings! Of course, it does not look as neat as "100%" would, but there are several strings not to be translated. So, yay for collaborative work! Oh, and FWIW Thanks to everybody who helped. And really, really, really, hats off to Luis Enrique Amaya, a friend whom I see way less than I should. A LIDSOL graduate, and a nice guy all around. Why to him specially? Well... This has several wrinkles to iron out, but, by number of translated lines:

• Andr s Delgado 195
• scannopolis 626
• Leo Arias 812
• Gunnar Wolf 947
• Luis Enrique Amaya Gonz lez 3258

...Need I say more? Luis, I hope you enjoyed reading the book :-] There is still a lot of work to do, and I'm asking the rest of the team some days so I can get my act together. From the mail I just sent, I need to:

1. Review the Pandoc conversion process, to get the strings formatted again into a book; I had got this working somewhere in the process, but last I checked it broke. I expect this not to be too much of a hurdle, and it will help all other translations.
2. Start the editorial process at my Institute. Once the book builds, I'll have to start again the stylistic correction process so the Institute agrees to print it out under its seal. This time, we have the hurdle that our correctors will probably hate us due to part of the work being done before we had actually agreed on some important Spanish language issues... which are different between Mexico, Argentina and Costa Rica (where translators are from). Anyway This sets the mood for a great start of the week. Yay!

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Here s my weekly report for week 40 of 2017. In this week I have looked at censorship in Catalonia and had my deleted Facebook account hacked (which made HN front page). I ve also been thinking about DRM on the web.

Debian I have prepared and uploaded fixes for the measurement-kit and hamradio-maintguide packages. I have also sponsored uploads for gnustep-base (to experimental) and chkservice. I have given DM upload privileges to Eric Heintzmann for the gnustep-base package as he has shown to care for the GNUstep packages well. In the near future, I think we re looking at a transition for gnustep- base,back,gui as these packages all have updates. Bugs filed: #877680 Bugs closed (fixed/wontfix): #872202, #877466, #877468

Tor Project This week I have participated in a discussion around renaming the Operations section of the Metrics website. I have also filed a new ticket on Atlas, which I am planning to implement, to link to the new relay lifecycle post on the Tor Project blog if a relay is less than a week old to help new relay operators understand the bandwidth usage they ll be seeing. Finally, I ve been hacking on a Twitter bot to tweet factoids about the public Tor network. I ve detailed this in a separate blog post. Bugs closed (fixed/wontfix): #23683

Sustainability I believe it is important to be clear not only about the work I have already completed but also about the sustainability of this work into the future. I plan to include a short report on the current sustainability of my work in each weekly report. I have not had any free software related expenses this week. The current funds I have available for equipment, travel and other free software expenses remains 60.52. I do not believe that any hardware I rely on is looking at imminent failure.

When I learned TeX, I was told to not write e.g. something, because TeX would think the period after the g ends a sentence, and introduce a wider, inter-sentence space. Instead, I was to write e.g.\ . Years later, I learned from a convincing, but since forgotten source, that in fact e.g.\@ is the proper thing to write. I vaguely remembering that e.g.\ supposedly affected the inter-word space in some unwanted way. So I did that for many years. Until I recently was called out for doing it wrong, and that infact e.g.\ is the proper way. This was supported by a StackExchange answer written by a LaTeX authority and backed by a reference to documentation. The same question has, however, another answer by another TeX authority, backed by an analysis of the implementation, which concludes that e.g.\@ is proper. What now? I guess I just have to find it out myself. The above image shows three variants: The obviously broken version with e.g., and the two contesting variants to fix it. Looks like they yield equal results! So maybe the difference lies in how \@ and \ react when the line length changes, and the word wrapping require differences in the inter-word spacing. Will there be differences? Let s see; I cannot see any difference. But the inter-sentence whitespace ate most of the expansion. Is there a difference visible if we have only inter-word spacing in the line? Again, I see the same behaviour. Conclusion: It does not matter, but e.g.\ is less hassle when using lhs2tex than e.g.\@ (which has to be escaped as e.g.\@@), so the winner is e.g.\ ! (Unless you put it in a macro, then \@ might be preferable, and it is still needed between a captial letter and a sentence period.)

A while ago I played with a Twitter bot that would track radio amateurs using a packet radio position reporting system, tweet their location and a picture from Flickr that was taken near to their location and a link to their packet radio activity on aprs.fi. It s really not that hard to put these things together and they can be a lot of fun. The tweets looked like this:

VK4CVL is mobile near Chapel Hill, Australia http://t.co/2dqvuqjJxQ http://t.co/q88OhtcPTX #hamradio #hamr pic.twitter.com/5gBVw3ebvq HamLocator (@HamLocator) June 12, 2015

This isn t about building a system that serves any critical purpose, it s about fun. As the radio stations were chosen essentially at random, there could be some cool things showing up that you wouldn t otherwise have seen. Maybe you d spot a callsign of a station you ve spoken to before on HF or perhaps you d see stations in areas near you or in cool places. On Friday evening I took a go at hacking together a bot for Tor relays. The idea being to have regular snippets of information from the Tor network and perhaps you ll spot something insightful or interesting. Not every tweet is going to be amazing, but it wasn t running for very long before I spotted a relay very close to its 10th birthday:

esko in Finland started contributing bandwidth to the #Tor network 9 years and 51 weeks ago https://t.co/4K7aj9Jf6C Tor Atlas (@TorAtlas) October 7, 2017

The relays are chosen at random, and tweet templates are chosen at random too. So far, tweets about individual relays can be about age or current bandwidth contribution to the Tor network. There are also tweets about how many relays run in a particular autonomous system (again, chosen at random) and tweets about the total number of relays currently running. The total relays tweets come with a map:

There are currently 6638 #Tor relays running. https://t.co/uySyX7AlAH pic.twitter.com/BbgNGpoNtY Tor Atlas (@TorAtlas) October 7, 2017

The maps are produced using xplanet. The Earth will rotate to show the current side in daylight at the time the tweet is posted. Unfortunately, the bot currently cannot tweet as the account has been suspended. You should still be able to follow @TorAtlas though and tweets will begin appearing again once I ve resolved the suspension. I plan to rewrite the mess of cron-activated Python scripts into a coherent Python (maybe Java) application and publish the sources soon. There are also a number of new templates for tweets I d like to explore, including number of relays and bandwidth contributed per family and statistics on operating system diversity. Update (2017-10-08): The @TorAtlas account should now be unsuspended.

At work, I help maintain a smartcard middleware that is provided to Belgian citizens who want to use their electronic ID card to, e.g., log on to government websites. This middleware is a piece of software that hooks into various browsers and adds a way to access the smartcard in question, through whatever APIs the operating system and the browser in question provide for that purpose. The details of how that is done differ between each browser (and in the case of Google Chrome, for the same browser between different operating systems); but for Firefox (and Google Chrome on free operating systems), this is done by way of a PKCS#11 module. For Firefox 57, mozilla decided to overhaul much of their browser. The changes are large and massive, and in some ways revolutionary. It's no surprise, therefore, that some of the changes break compatibility with older things. One of the areas in which breaking changes were made is in the area of extensions to the browser. Previously, Firefox had various APIs available for extensions; right now, all APIs apart from the WebExtensions API are considered "legacy" and support for them will be removed from Firefox 57 going forward. Since installing a PKCS#11 module manually is a bit complicated, and since the legacy APIs provided a way to do so automatically provided the user would first install an add-on (or provided the installer of the PKCS#11 module sideloads it), most parties who provide a PKCS#11 module for use with Firefox will provide an add-on to automatically install it. Since the alternative involves entering the right values in a dialog box that's hidden away somewhere deep in the preferences screen, the add-on option is much more user friendly. I'm sure you can imagine my dismay when I found out that there was no WebExtensions API to provide the same functionality. So, after asking around a bit, I filed bug 1357391 to get a discussion started. While it took some convincing initially to get people to understand the reasons for wanting such an API, eventually the bug was assigned the "P5" priority -- essentially, a "we understand the need and won't block it, but we don't have the time to implement it. Patches welcome, though" statement. Since having an add-on was something that work really wanted, and since I had the time, I got the go-ahead from management to look into implementing the required code myself. I made it obvious rather quickly that my background in Firefox was fairly limited, though, and so was assigned a mentor to help me through the process. Having been a Debian Developer for the past fifteen years, I do understand how to develop free software. Yet, the experience was different enough that still learned some new things about free software development, which was somewhat unexpected. Unfortunately, the process took much longer than I had hoped, which meant that the patch was not ready by the time Firefox 57 was branched off mozilla's "central" repository. The result of that is that while my patch has been merged into what will eventually become Firefox 58, it looks strongly as though it won't make it into Firefox 57. That's going to cause some severe headaches, which I'm not looking forward to; and while I can certainly understand the reasons for not wanting to grant the exception for the merge into 57, I can't help but feeling like this is a missed opportunity. Anyway, writing code for the massive Open Source project that mozilla is has been a load of fun, and in the process I've learned a lot -- not only about Open Source development in general, but also about this weird little thing that Javascript is. That might actually be useful for this other project that I've got running here. In closing, I'd like to thank Tomislav 'zombie' Jovanovic for mentoring me during the whole process, without whom it would have been doubtful if I would even have been ready by now. Apologies for any procedural mistakes I've made, and good luck in your future endeavours!

Seems it is now almost a decade since I migrated from Thunderbird to GNUS. And GNUS is an awesome mail program that I still rather like. However GNUS is also heavily quirky. It's essentially single-threaded and synchronous which means you either have to wait for the "IMAP check for new mails" to finish or you have to C-g abort it if you want the user interface to work; You have to wait for the "Move mail" to complete (which can take a while -- especially with dovecot-antispam training the filter) before you can continue working. It has it's funny way around TLS and certificate validation. And it seems to hang from time to time until it is C-g interrupted. So when I set up my new desktop machine I decided to try something else. My first try was claws-mail which seems OK but totally fails in the asynchronous area. While the GUI stays reactive, all actions that require IMAP interactions become incredibly slow when a background IMAP refresh is running. I do have quite some mailboxes and waiting the 5+ minutes after opening claws or whenever it decides to do a refresh is just to much. Now my last try has been Kmail -- also driven by the idea of having a more integrated setup with CalDAV and CardDAV around and similar goodies. And Kmail really compares nicely to claws in many ways. After all, I can use it while it's doing its things in the background. However the KDE folks seem to have dropped all support for the \recent IMAP flag which I heavily rely on. I do -- after all -- keep a GNUS like workflow where all unread mail (ref \seen) needs to still be acted upon which means there can easily be quite a few unread messages when I'm busy at the moment and just having a quick look at the new (ref \recent) mail to see if there's something super-urgent is essential. So I'm now looking for useful suggestions for a mail program (ideally with desktop integration) with the following essential features:

• It stays usable at all times -- which means smarter queuing than claws -- so foreground actions are not delayed by any background task the mail program might be up to and tasks like moving mail are handled in the background.
• Decent support for filtering. Apart from some basic stuff I need shortcut filtering for \recent mail.
• Option to hide \seen mail (and ideally hide all folders that only contain \seen mail). Hopefully toggle-able by some hotkey. "Age in days" would be an acceptable approximation, but Kmail doesn't seem to allow that in search (it's available as a filter though).

Debian Long Term Support (LTS) This is my monthly Debian LTS report. I mostly worked on the git, git-annex and ruby packages this month but didn't have time to completely use my allocated hours because I started too late in the month.

Ruby I was hoping someone would pick up the Ruby work I submitted in August, but it seems no one wanted to touch that mess, understandably. Since then, new issues came up, and not only did I have to work on the rubygems and ruby1.9 package, but now the ruby1.8 package also had to get security updates. Yes: it's bad enough that the rubygems code is duplicated in one other package, but wheezy had the misfortune of having two Ruby versions supported. The Ruby 1.9 also failed to build from source because of test suite issues, which I haven't found a clean and easy fix for, so I ended up making test suite failures non-fatal in 1.9, which they were already in 1.8. I did keep a close eye on changes in the test suite output to make sure tests introduced in the security fixes would pass and that I wouldn't introduce new regressions as well. So I published the following advisories:

• ruby 1.8: DLA-1113-1, fixing CVE-2017-0898 and CVE-2017-10784. 1.8 doesn't seem affected by CVE-2017-14033 as the provided test does not fail (but it does fail in 1.9.1). test suite was, before patch:

  2199 tests, 1672513 assertions, 18 failures, 51 errors
  

  and after patch:

  2200 tests, 1672514 assertions, 18 failures, 51 errors
  

• rubygems: uploaded the package prepared in August as is in DLA-1112-1, fixing CVE-2017-0899, CVE-2017-0900, CVE-2017-0901. here the test suite passed normally.
• ruby 1.9: here I used the used 2.2.8 release tarball to generate a patch that would cover all issues and published DLA-1114-1 that fixes the CVEs of the two packages above. the test suite was, before patches:

  10179 tests, 2232711 assertions, 26 failures, 23 errors, 51 skips
  

  and after patches:

  1.9 after patches (B): 10184 tests, 2232771 assertions, 26 failures, 23 errors, 53 skips
  

Git I also quickly issued an advisory (DLA-1120-1) for CVE-2017-14867, an odd issue affecting git in wheezy. The backport was tricky because it wouldn't apply cleanly and the git package had a custom patching system which made it tricky to work on.

Git-annex I did a quick stint on git-annex as well: I was able to reproduce the issue and confirm an approach to fixing the issue in wheezy, although I didn't have time to complete the work before the end of the month.

Other free software work

New project: feed2exec I should probably make a separate blog post about this, but ironically, I don't want to spend too much time writing those reports, so this will be quick. I wrote a new program, called feed2exec. It's basically a combination of feed2imap, rss2email and feed2tweet: it allows you to fetch RSS feeds and send them in a mailbox, but what's special about it, compared to the other programs above, is that it is more generic: you can basically make it do whatever you want on new feed items. I have, for example, replaced my feed2tweet instance with it, using this simple configuration:

[anarcat]
url = https://anarc.at/blog/index.rss
output = feed2exec.plugins.exec
args = tweet "%(title)0.70s %(link)0.70s"

The sample configuration file also has examples to talk with Mastodon, Pump.io and, why not, a torrent server to download torrent files available over RSS feeds. A trivial configuration can also make it work as a crude podcast client. My main motivation to work on this was that it was difficult to extend feed2imap to do what I needed (which was to talk to transmission to download torrent files) and rss2email didn't support my workflow (which is delivering to feed-specific mail folders). Because both projects also seemed abandoned, it seemed like a good idea at the time to start a new one, although the rss2email community has now restarted the project and may produce interesting results. As an experiment, I tracked my time working on this project. It turns out it took about 45 hours to write that software. Considering feed2exec is about 1400 SLOC, that's 30 lines of code per hour. I don't know if that's slow or fast, but it's an interesting metric for future projects. It sure seems slow to me, but we need to keep in mind those 30 lines of code don't include documentation and repeated head banging on the keyboard. For example, I found two issues with the upstream feedparser package which I use to parse feeds which also seems unmaintained, unfortunately. Feed2exec is beta software at this point, but it's working well enough for me and the design is much simpler than the other programs of the kind. The main issue people can expect from it at this point is formatting issues or parse errors on exotic feeds, and noisy error messages on network errors, all of which should be fairly easy to fix in the test suite. I hope it will be useful for the community and, as usual, I welcome contributions, help and suggestions on how to improve the software.

More Python templates As part of the work on feed2exec, I did cleanup a few things in the ecdysis project, mostly to hook tests up in the CI, improve on the advancedConfig logger and cleanup more stuff. While I was there, it turns out that I built a pretty decent basic CI configuration for Python on GitLab. Whereas the previous templates only had a non-working Django example, you should now be able to chose a Python template when you configure CI on GitLab 10 and above, which should hook you up with normal Python setup procedures like setup.py install and setup.py test.

Selfspy I mentioned working on a monitoring tool in my last post, because it was a feature from Workrave missing in SafeEyes. It turns out there is already such a tool called selfspy. I did an extensive review of the software to make sure it wouldn't leak out confidential information out before using it, and it looks, well... kind of okay. It crashed on me at least once so far, which is too bad because then it loses track of the precious activity. I have used it at least once to figure out what the heck I worked on during the day, so it's pretty useful. I particularly used it to backtrack my work on feed2exec as I didn't originally track my time on the project. Unfortunately, selfspy seems unmaintained. I have proposed a maintenance team and hopefully the project maintainer will respond and at least share access so we don't end up in a situation like linkchecker. I also sent a bunch of pull requests to fix some issues like being secure by default and fixing the build. Apart from the crash, the main issue I have found with the software is that it doesn't detect idle time which means certain apps are disproportionatly represented in statistics. There are also some weaknesses in the crypto that should be adressed for people that encrypt their database. Next step is to package selfspy in Debian which should hopefully be simple enough...

Restic documentation security As part of a documentation patch on the Restic backup software, I have improved on my previous Perl script to snoop on process commandline arguments. A common flaw in shell scripts and cron jobs is to pass secret material in the environment (usually safe) but often through commandline arguments (definitely not safe). The challenge, in this peculiar case, was the env binary, but the last time I encountered such an issue was with the Drush commandline tool, which was passing database credentials in clear to the mysql binary. Using my Perl sniffer, I could get to 60 checks per second (or 60Hz). After reimplementing it in Python, this number went up to 160Hz, which still wasn't enough to catch the elusive env command, which is much faster at hiding arguments than MySQL, in large part because it simply does an execve() once the environment is setup. Eventually, I just went crazy and rewrote the whole thing in C which was able to get 700-900Hz and did catch the env command about 10-20% of the time. I could probably have rewritten this by simply walking /proc myself (since this is what all those libraries do in the end) to get better result, but then my point was made. I was able to prove to the restic author the security issues that warranted the warning. It's too bad I need to repeat this again and again, but then my tools are getting better at proving that issue... I suspect it's not the last time I have to deal with this issue and I am happy to think that I can come up with an even more efficient proof of concept tool the next time around.

Ansible 101 After working on documentation last month, I ended up writing my first Ansible playbook this month, converting my tasksel list to a working Ansible configuration. This was a useful exercise: it allow me to find a bunch of packages which have been removed from Debian and provides much better usability than tasksel. For example, it provides a --diff argument that shows which packages are missing from a given setup. I am still unsure about Ansible. Manifests do seem really verbose and I still can't get used to the YAML DSL. I could probably have done the same thing with Puppet and just run puppet apply on the resulting config. But I must admit my bias towards Python is showing here: I can't help but think Puppet is going to be way less accessible with its rewrite in Clojure and C (!)... But then again, I really like Puppet's approach of having generic types like package or service rather than Ansible's clunky apt/yum/dnf/package/win_package types...

Pat and Ham radio After responding (too late) to a request for volunteers to help in Puerto Rico, I realized that my amateur radio skills were somewhat lacking in the "packet" (data transmission in ham jargon) domain, as I wasn't used to operate a Winlink node. Such a node can receive and transmit actual emails over the airwaves, for free, without direct access to the internet, which is very useful in disaster relief efforts. Through summary research, I stumbled upon the new and very promising Pat project which provides one of the first user-friendly Linux-compatible Winlink programs. I provided improvements on the documentation and some questions regarding compatibility issues which are still pending. But my pet issue is the establishment of pat as a normal internet citizen by using standard protocols for receiving and sending email. Not sure how that can be implemented, but we'll see. I am also hoping to upload an official Debian package and hopefully write more about this soon. Stay tuned!

Random stuff I ended up fixing my Kodi issue by starting it as a standalone systemd service, instead of gdm3, which is now completely disabled on the media box. I simply used the following /etc/systemd/service/kodi.service file:

[Unit]
Description=Kodi Media Center
After=systemd-user-sessions.service network.target sound.target
[Service]
User=xbmc
Group=video
Type=simple
TTYPath=/dev/tty7
StandardInput=tty
ExecStart=/usr/bin/xinit /usr/bin/dbus-launch --exit-with-session /usr/bin/kodi-standalone -- :1 -nolisten tcp vt7
Restart=on-abort
RestartSec=5
[Install]
WantedBy=multi-user.target

The downside of this is that it needs Xorg to run as root, whereas modern Xorg can now run rootless. Not sure how to fix this or where... But if I put needs_root_rights=no in Xwrapper.config, I get the following error in .local/share/xorg/Xorg.1.log:

[  2502.533] (EE) modeset(0): drmSetMaster failed: Permission denied

After fooling around with iPython, I ended up trying the xonsh shell, which is supposed to provide a bash-compatible Python shell environment. Unfortunately, I found it pretty unusable as a shell: it works fine to do Python stuff, but then all my environment and legacy bash configuration files were basically ignored so I couldn't get working quickly. This is too bad because the project looked very promising... Finally, one of my TLS hosts using a Let's Encrypt certificate wasn't renewing properly, and I figured out why. It turns out the ProxyPass command was passing everything to the backend, including the /.well-known requests, which obviously broke ACME verification. The solution was simple enough, disable the proxy for that directory:

ProxyPass /.well-known/ !

Debian Long Term Support (LTS) This is my monthly Debian LTS report. I mostly worked on the git, git-annex and ruby packages this month but didn't have time to completely use my allocated hours because I started too late in the month.

Ruby I was hoping someone would pick up the Ruby work I submitted in August, but it seems no one wanted to touch that mess, understandably. Since then, new issues came up, and not only did I have to work on the rubygems and ruby1.9 package, but now the ruby1.8 package also had to get security updates. Yes: it's bad enough that the rubygems code is duplicated in one other package, but wheezy had the misfortune of having two Ruby versions supported. The Ruby 1.9 also failed to build from source because of test suite issues, which I haven't found a clean and easy fix for, so I ended up making test suite failures non-fatal in 1.9, which they were already in 1.8. I did keep a close eye on changes in the test suite output to make sure tests introduced in the security fixes would pass and that I wouldn't introduce new regressions as well. So I published the following advisories:

• ruby 1.8: DLA-1113-1, fixing CVE-2017-0898 and CVE-2017-10784. 1.8 doesn't seem affected by CVE-2017-14033 as the provided test does not fail (but it does fail in 1.9.1). test suite was, before patch:

  2199 tests, 1672513 assertions, 18 failures, 51 errors
  

  and after patch:

  2200 tests, 1672514 assertions, 18 failures, 51 errors
  

• rubygems: uploaded the package prepared in August as is in DLA-1112-1, fixing CVE-2017-0899, CVE-2017-0900, CVE-2017-0901. here the test suite passed normally.
• ruby 1.9: here I used the used 2.2.8 release tarball to generate a patch that would cover all issues and published DLA-1114-1 that fixes the CVEs of the two packages above. the test suite was, before patches:

  10179 tests, 2232711 assertions, 26 failures, 23 errors, 51 skips
  

  and after patches:

  1.9 after patches (B): 10184 tests, 2232771 assertions, 26 failures, 23 errors, 53 skips
  

Git I also quickly issued an advisory (DLA-1120-1) for CVE-2017-14867, an odd issue affecting git in wheezy. The backport was tricky because it wouldn't apply cleanly and the git package had a custom patching system which made it tricky to work on.

Git-annex I did a quick stint on git-annex as well: I was able to reproduce the issue and confirm an approach to fixing the issue in wheezy, although I didn't have time to complete the work before the end of the month.

Other free software work

New project: feed2exec I should probably make a separate blog post about this, but ironically, I don't want to spend too much time writing those reports, so this will be quick. I wrote a new program, called feed2exec. It's basically a combination of feed2imap, rss2email and feed2tweet: it allows you to fetch RSS feeds and send them in a mailbox, but what's special about it, compared to the other programs above, is that it is more generic: you can basically make it do whatever you want on new feed items. I have, for example, replaced my feed2tweet instance with it, using this simple configuration:

[anarcat]
url = https://anarc.at/blog/index.rss
output = feed2exec.plugins.exec
args = tweet "%(title)0.70s %(link)0.70s"

The sample configuration file also has examples to talk with Mastodon, Pump.io and, why not, a torrent server to download torrent files available over RSS feeds. A trivial configuration can also make it work as a crude podcast client. My main motivation to work on this was that it was difficult to extend feed2imap to do what I needed (which was to talk to transmission to download torrent files) and rss2email didn't support my workflow (which is delivering to feed-specific mail folders). Because both projects also seemed abandoned, it seemed like a good idea at the time to start a new one, although the rss2email community has now restarted the project and may produce interesting results. As an experiment, I tracked my time working on this project. It turns out it took about 45 hours to write that software. Considering feed2exec is about 1400 SLOC, that's 30 lines of code per hour. I don't know if that's slow or fast, but it's an interesting metric for future projects. It sure seems slow to me, but we need to keep in mind those 30 lines of code don't include documentation and repeated head banging on the keyboard. For example, I found two issues with the upstream feedparser package which I use to parse feeds which also seems unmaintained, unfortunately. Feed2exec is beta software at this point, but it's working well enough for me and the design is much simpler than the other programs of the kind. The main issue people can expect from it at this point is formatting issues or parse errors on exotic feeds, and noisy error messages on network errors, all of which should be fairly easy to fix in the test suite. I hope it will be useful for the community and, as usual, I welcome contributions, help and suggestions on how to improve the software.

More Python templates As part of the work on feed2exec, I did cleanup a few things in the ecdysis project, mostly to hook tests up in the CI, improve on the advancedConfig logger and cleanup more stuff. While I was there, it turns out that I built a pretty decent basic CI configuration for Python on GitLab. Whereas the previous templates only had a non-working Django example, you should now be able to chose a Python template when you configure CI on GitLab 10 and above, which should hook you up with normal Python setup procedures like setup.py install and setup.py test.

Selfspy I mentioned working on a monitoring tool in my last post, because it was a feature from Workrave missing in SafeEyes. It turns out there is already such a tool called selfspy. I did an extensive review of the software to make sure it wouldn't leak out confidential information out before using it, and it looks, well... kind of okay. It crashed on me at least once so far, which is too bad because then it loses track of the precious activity. I have used it at least once to figure out what the heck I worked on during the day, so it's pretty useful. I particularly used it to backtrack my work on feed2exec as I didn't originally track my time on the project. Unfortunately, selfspy seems unmaintained. I have proposed a maintenance team and hopefully the project maintainer will respond and at least share access so we don't end up in a situation like linkchecker. I also sent a bunch of pull requests to fix some issues like being secure by default and fixing the build. Apart from the crash, the main issue I have found with the software is that it doesn't detect idle time which means certain apps are disproportionatly represented in statistics. There are also some weaknesses in the crypto that should be adressed for people that encrypt their database. Next step is to package selfspy in Debian which should hopefully be simple enough...

Restic documentation security As part of a documentation patch on the Restic backup software, I have improved on my previous Perl script to snoop on process commandline arguments. A common flaw in shell scripts and cron jobs is to pass secret material in the environment (usually safe) but often through commandline arguments (definitely not safe). The challenge, in this peculiar case, was the env binary, but the last time I encountered such an issue was with the Drush commandline tool, which was passing database credentials in clear to the mysql binary. Using my Perl sniffer, I could get to 60 checks per second (or 60Hz). After reimplementing it in Python, this number went up to 160Hz, which still wasn't enough to catch the elusive env command, which is much faster at hiding arguments than MySQL, in large part because it simply does an execve() once the environment is setup. Eventually, I just went crazy and rewrote the whole thing in C which was able to get 700-900Hz and did catch the env command about 10-20% of the time. I could probably have rewritten this by simply walking /proc myself (since this is what all those libraries do in the end) to get better result, but then my point was made. I was able to prove to the restic author the security issues that warranted the warning. It's too bad I need to repeat this again and again, but then my tools are getting better at proving that issue... I suspect it's not the last time I have to deal with this issue and I am happy to think that I can come up with an even more efficient proof of concept tool the next time around.

Ansible 101 After working on documentation last month, I ended up writing my first Ansible playbook this month, converting my tasksel list to a working Ansible configuration. This was a useful exercise: it allow me to find a bunch of packages which have been removed from Debian and provides much better usability than tasksel. For example, it provides a --diff argument that shows which packages are missing from a given setup. I am still unsure about Ansible. Manifests do seem really verbose and I still can't get used to the YAML DSL. I could probably have done the same thing with Puppet and just run puppet apply on the resulting config. But I must admit my bias towards Python is showing here: I can't help but think Puppet is going to be way less accessible with its rewrite in Clojure and C (!)... But then again, I really like Puppet's approach of having generic types like package or service rather than Ansible's clunky apt/yum/dnf/package/win_package types...

Pat and Ham radio After responding (too late) to a request for volunteers to help in Puerto Rico, I realized that my amateur radio skills were somewhat lacking in the "packet" (data transmission in ham jargon) domain, as I wasn't used to operate a Winlink node. Such a node can receive and transmit actual emails over the airwaves, for free, without direct access to the internet, which is very useful in disaster relief efforts. Through summary research, I stumbled upon the new and very promising Pat project which provides one of the first user-friendly Linux-compatible Winlink programs. I provided improvements on the documentation and some questions regarding compatibility issues which are still pending. But my pet issue is the establishment of pat as a normal internet citizen by using standard protocols for receiving and sending email. Not sure how that can be implemented, but we'll see. I am also hoping to upload an official Debian package and hopefully write more about this soon. Stay tuned!

Random stuff I ended up fixing my Kodi issue by starting it as a standalone systemd service, instead of gdm3, which is now completely disabled on the media box. I simply used the following /etc/systemd/service/kodi.service file:

[Unit]
Description=Kodi Media Center
After=systemd-user-sessions.service network.target sound.target
[Service]
User=xbmc
Group=video
Type=simple
TTYPath=/dev/tty7
StandardInput=tty
ExecStart=/usr/bin/xinit /usr/bin/dbus-launch --exit-with-session /usr/bin/kodi-standalone -- :1 -nolisten tcp vt7
Restart=on-abort
RestartSec=5
[Install]
WantedBy=multi-user.target

The downside of this is that it needs Xorg to run as root, whereas modern Xorg can now run rootless. Not sure how to fix this or where... But if I put needs_root_rights=no in Xwrapper.config, I get the following error in .local/share/xorg/Xorg.1.log:

[  2502.533] (EE) modeset(0): drmSetMaster failed: Permission denied

After fooling around with iPython, I ended up trying the xonsh shell, which is supposed to provide a bash-compatible Python shell environment. Unfortunately, I found it pretty unusable as a shell: it works fine to do Python stuff, but then all my environment and legacy bash configuration files were basically ignored so I couldn't get working quickly. This is too bad because the project looked very promising... Finally, one of my TLS hosts using a Let's Encrypt certificate wasn't renewing properly, and I figured out why. It turns out the ProxyPass command was passing everything to the backend, including the /.well-known requests, which obviously broke ACME verification. The solution was simple enough, disable the proxy for that directory:

ProxyPass /.well-known/ !

While the adoption of OpenPGP by the general population is marginal at best, it is a critical component for the security community and particularly for Linux distributions. For example, every package uploaded into Debian is verified by the central repository using the maintainer's OpenPGP keys and the repository itself is, in turn, signed using a separate key. If upstream packages also use such signatures, this creates a complete trust path from the original upstream developer to users. Beyond that, pull requests for the Linux kernel are verified using signatures as well. Therefore, the stakes are high: a compromise of the release key, or even of a single maintainer's key, could enable devastating attacks against many machines. That has led the Debian community to develop a good grasp of best practices for cryptographic signatures (which are typically handled using GNU Privacy Guard, also known as GnuPG or GPG). For example, weak (less than 2048 bits) and vulnerable PGPv3 keys were removed from the keyring in 2015, and there is a strong culture of cross-signing keys between Debian members at in-person meetings. Yet even Debian developers (DDs) do not seem to have established practices on how to actually store critical private key material, as we can see in this discussion on the debian-project mailing list. That email boiled down to a simple request: can I have a "key dongles for dummies" tutorial? Key dongles, or keycards as we'll call them here, are small devices that allow users to store keys on an offline device and provide one possible solution for protecting private key material. In this article, I hope to use my experience in this domain to clarify the issue of how to store those precious private keys that, if compromised, could enable arbitrary code execution on millions of machines all over the world.

Why store keys offline? Before we go into details about storing keys offline, it may be useful to do a small reminder of how the OpenPGP standard works. OpenPGP keys are made of a main public/private key pair, the certification key, used to sign user identifiers and subkeys. My public key, shown below, has the usual main certification/signature key (marked SC) but also an encryption subkey (marked E), a separate signature key (S), and two authentication keys (marked A) which I use as RSA keys to log into servers using SSH, thanks to the Monkeysphere project.

    pub   rsa4096/792152527B75921E 2009-05-29 [SC] [expires: 2018-04-19]
      8DC901CE64146C048AD50FBB792152527B75921E
    uid                 [ultimate] Antoine Beaupr  <anarcat@anarc.at>
    uid                 [ultimate] Antoine Beaupr  <anarcat@koumbit.org>
    uid                 [ultimate] Antoine Beaupr  <anarcat@orangeseeds.org>
    uid                 [ultimate] Antoine Beaupr  <anarcat@debian.org>
    sub   rsa2048/B7F648FED2DF2587 2012-07-18 [A]
    sub   rsa2048/604E4B3EEE02855A 2012-07-20 [A]
    sub   rsa4096/A51D5B109C5A5581 2009-05-29 [E]
    sub   rsa2048/3EA1DDDDB261D97B 2017-08-23 [S]

All the subkeys (sub) and identities (uid) are bound by the main certification key using cryptographic self-signatures. So while an attacker stealing a private subkey can spoof signatures in my name or authenticate to other servers, that key can always be revoked by the main certification key. But if the certification key gets stolen, all bets are off: the attacker can create or revoke identities or subkeys as they wish. In a catastrophic scenario, an attacker could even steal the key and remove your copies, taking complete control of the key, without any possibility of recovery. Incidentally, this is why it is so important to generate a revocation certificate and store it offline. So by moving the certification key offline, we reduce the attack surface on the OpenPGP trust chain: day-to-day keys (e.g. email encryption or signature) can stay online but if they get stolen, the certification key can revoke those keys without having to revoke the main certification key as well. Note that a stolen encryption key is a different problem: even if we revoke the encryption subkey, this will only affect future encrypted messages. Previous messages will be readable by the attacker with the stolen subkey even if that subkey gets revoked, so the benefits of revoking encryption certificates are more limited.

Common strategies for offline key storage Considering the security tradeoffs, some propose storing those critical keys offline to reduce those threats. But where exactly? In an attempt to answer that question, Jonathan McDowell, a member of the Debian keyring maintenance team, said that there are three options: use an external LUKS-encrypted volume, an air-gapped system, or a keycard. Full-disk encryption like LUKS adds an extra layer of security by hiding the content of the key from an attacker. Even though private keyrings are usually protected by a passphrase, they are easily identifiable as a keyring. But when a volume is fully encrypted, it's not immediately obvious to an attacker there is private key material on the device. According to Sean Whitton, another advantage of LUKS over plain GnuPG keyring encryption is that you can pass the --iter-time argument when creating a LUKS partition to increase key-derivation delay, which makes brute-forcing much harder. Indeed, GnuPG 2.x doesn't have a run-time option to configure the key-derivation algorithm, although a patch was introduced recently to make the delay configurable at compile time in gpg-agent, which is now responsible for all secret key operations. The downside of external volumes is complexity: GnuPG makes it difficult to extract secrets out of its keyring, which makes the first setup tricky and error-prone. This is easier in the 2.x series thanks to the new storage system and the associated keygrip files, but it still requires arcane knowledge of GPG internals. It is also inconvenient to use secret keys stored outside your main keyring when you actually do need to use them, as GPG doesn't know where to find those keys anymore. Another option is to set up a separate air-gapped system to perform certification operations. An example is the PGP clean room project, which is a live system based on Debian and designed by DD Daniel Pocock to operate an OpenPGP and X.509 certificate authority using commodity hardware. The basic principle is to store the secrets on a different machine that is never connected to the network and, therefore, not exposed to attacks, at least in theory. I have personally discarded that approach because I feel air-gapped systems provide a false sense of security: data eventually does need to come in and out of the system, somehow, even if only to propagate signatures out of the system, which exposes the system to attacks. System updates are similarly problematic: to keep the system secure, timely security updates need to be deployed to the air-gapped system. A common use pattern is to share data through USB keys, which introduce a vulnerability where attacks like BadUSB can infect the air-gapped system. From there, there is a multitude of exotic ways of exfiltrating the data using LEDs, infrared cameras, or the good old TEMPEST attack. I therefore concluded the complexity tradeoffs of an air-gapped system are not worth it. Furthermore, the workflow for air-gapped systems is complex: even though PGP clean room went a long way, it's still lacking even simple scripts that allow signing or transferring keys, which is a problem shared by the external LUKS storage approach.

Keycard advantages The approach I have chosen is to use a cryptographic keycard: an external device, usually connected through the USB port, that stores the private key material and performs critical cryptographic operations on the behalf of the host. For example, the FST-01 keycard can perform RSA and ECC public-key decryption without ever exposing the private key material to the host. In effect, a keycard is a miniature computer that performs restricted computations for another host. Keycards usually support multiple "slots" to store subkeys. The OpenPGP standard specifies there are three subkeys available by default: for signature, authentication, and encryption. Finally, keycards can have an actual physical keypad to enter passwords so a potential keylogger cannot capture them, although the keycards I have access to do not feature such a keypad. We could easily draw a parallel between keycards and an air-gapped system; in effect, a keycard is a miniaturized air-gapped computer and suffers from similar problems. An attacker can intercept data on the host system and attack the device in the same way, if not more easily, because a keycard is actually "online" (i.e. clearly not air-gapped) when connected. The advantage over a fully-fledged air-gapped computer, however, is that the keycard implements only a restricted set of operations. So it is easier to create an open hardware and software design that is audited and verified, which is much harder to accomplish for a general-purpose computer. Like air-gapped systems, keycards address the scenario where an attacker wants to get the private key material. While an attacker could fool the keycard into signing or decrypting some data, this is possible only while the key is physically connected, and the keycard software will prompt the user for a password before doing the operation, though the keycard can cache the password for some time. In effect, it thwarts offline attacks: to brute-force the key's password, the attacker needs to be on the target system and try to guess the keycard's password, which will lock itself after a limited number of tries. It also provides for a clean and standard interface to store keys offline: a single GnuPG command moves private key material to a keycard (the keytocard command in the --edit-key interface), whereas moving private key material to a LUKS-encrypted device or air-gapped computer is more complex. Keycards are also useful if you operate on multiple computers. A common problem when using GnuPG on multiple machines is how to safely copy and synchronize private key material among different devices, which introduces new security problems. Indeed, a "good rule of thumb in a forensics lab", according to Robert J. Hansen on the GnuPG mailing list, is to "store the minimum personal data possible on your systems". Keycards provide the best of both worlds here: you can use your private key on multiple computers without actually storing it in multiple places. In fact, Mike Gerwitz went as far as saying:

For users that need their GPG key on multiple boxes, I consider a smartcard to be essential. Otherwise, the user is just furthering her risk of compromise.

Keycard tradeoffs As Gerwitz hinted, there are multiple downsides to using a keycard, however. Another DD, Wouter Verhelst clearly expressed the tradeoffs:

Smartcards are useful. They ensure that the private half of your key is never on any hard disk or other general storage device, and therefore that it cannot possibly be stolen (because there's only one possible copy of it). Smartcards are a pain in the ass. They ensure that the private half of your key is never on any hard disk or other general storage device but instead sits in your wallet, so whenever you need to access it, you need to grab your wallet to be able to do so, which takes more effort than just firing up GnuPG. If your laptop doesn't have a builtin cardreader, you also need to fish the reader from your backpack or wherever, etc.

"Smartcards" here refer to older OpenPGP cards that relied on the IEC 7816 smartcard connectors and therefore needed a specially-built smartcard reader. Newer keycards simply use a standard USB connector. In any case, it's true that having an external device introduces new issues: attackers can steal your keycard, you can simply lose it, or wash it with your dirty laundry. A laptop or a computer can also be lost, of course, but it is much easier to lose a small USB keycard than a full laptop and I have yet to hear of someone shoving a full laptop into a washing machine. When you lose your keycard, unless a separate revocation certificate is available somewhere, you lose complete control of the key, which is catastrophic. But, even if you revoke the lost key, you need to create a new one, which involves rebuilding the web of trust for the key a rather expensive operation as it usually requires meeting other OpenPGP users in person to exchange fingerprints. You should therefore think about how to back up the certification key, which is a problem that already exists for online keys; of course, everyone has a revocation certificates and backups of their OpenPGP keys... right? In the keycard scenario, backups may be multiple keycards distributed geographically. Note that, contrary to an air-gapped system, a key generated on a keycard cannot be backed up, by design. For subkeys, this is not a problem as they do not need to be backed up (except encryption keys). But, for a certification key, this means users need to generate the key on the host and transfer it to the keycard, which means the host is expected to have enough entropy to generate cryptographic-strength random numbers, for example. Also consider the possibility of combining different approaches: you could, for example, use a keycard for day-to-day operation, but keep a backup of the certification key on a LUKS-encrypted offline volume. Keycards introduce a new element into the trust chain: you need to trust the keycard manufacturer to not have any hostile code in the key's firmware or hardware. In addition, you need to trust that the implementation is correct. Keycards are harder to update: the firmware may be deliberately inaccessible to the host for security reasons or may require special software to manipulate. Keycards may be slower than the CPU in performing certain operations because they are small embedded microcontrollers with limited computing power. Finally, keycards may encourage users to trust multiple machines with their secrets, which works against the "minimum personal data" principle. A completely different approach called the trusted physical console (TPC) does the opposite: instead of trying to get private key material onto all of those machines, just have them on a single machine that is used for everything. Unlike a keycard, the TPC is an actual computer, say a laptop, which has the advantage of needing no special procedure to manage keys. The downside is, of course, that you actually need to carry that laptop everywhere you go, which may be problematic, especially in some corporate environments that restrict bringing your own devices.

Quick keycard "howto" Getting keys onto a keycard is easy enough:

1. Start with a temporary key to test the procedure:

       export GNUPGHOME=$(mktemp -d)
       gpg --generate-key
   

2. Edit the key using its user ID (UID):

       gpg --edit-key UID
   

3. Use the key command to select the first subkey, then copy it to the keycard (you can also use the addcardkey command to just generate a new subkey directly on the keycard):

       gpg> key 1
       gpg> keytocard
   

4. If you want to move the subkey, use the save command, which will remove the local copy of the private key, so the keycard will be the only copy of the secret key. Otherwise use the quit command to save the key on the keycard, but keep the secret key in your normal keyring; answer "n" to "save changes?" and "y" to "quit without saving?" . This way the keycard is a backup of your secret key.
5. Once you are satisfied with the results, repeat steps 1 through 4 with your normal keyring (unset $GNUPGHOME)

When a key is moved to a keycard, --list-secret-keys will show it as sec> (or ssb> for subkeys) instead of the usual sec keyword. If the key is completely missing (for example, if you moved it to a LUKS container), the # sign is used instead. If you need to use a key from a keycard backup, you simply do gpg --card-edit with the key plugged in, then type the fetch command at the prompt to fetch the public key that corresponds to the private key on the keycard (which stays on the keycard). This is the same procedure as the one to use the secret key on another computer.

Conclusion There are already informal OpenPGP best-practices guides out there and some recommend storing keys offline, but they rarely explain what exactly that means. Storing your primary secret key offline is important in dealing with possible compromises and we examined the main ways of doing so: either with an air-gapped system, LUKS-encrypted keyring, or by using keycards. Each approach has its own tradeoffs, but I recommend getting familiar with keycards if you use multiple computers and want a standardized interface with minimal configuration trouble. And of course, those approaches can be combined. This tutorial, for example, uses a keycard on an air-gapped computer, which neatly resolves the question of how to transmit signatures between the air-gapped system and the world. It is definitely not for the faint of heart, however. Once one has decided to use a keycard, the next order of business is to choose a specific device. That choice will be addressed in a followup article, where I will look at performance, physical design, and other considerations.

This article first appeared in the Linux Weekly News.

While the adoption of OpenPGP by the general population is marginal at best, it is a critical component for the security community and particularly for Linux distributions. For example, every package uploaded into Debian is verified by the central repository using the maintainer's OpenPGP keys and the repository itself is, in turn, signed using a separate key. If upstream packages also use such signatures, this creates a complete trust path from the original upstream developer to users. Beyond that, pull requests for the Linux kernel are verified using signatures as well. Therefore, the stakes are high: a compromise of the release key, or even of a single maintainer's key, could enable devastating attacks against many machines. That has led the Debian community to develop a good grasp of best practices for cryptographic signatures (which are typically handled using GNU Privacy Guard, also known as GnuPG or GPG). For example, weak (less than 2048 bits) and vulnerable PGPv3 keys were removed from the keyring in 2015, and there is a strong culture of cross-signing keys between Debian members at in-person meetings. Yet even Debian developers (DDs) do not seem to have established practices on how to actually store critical private key material, as we can see in this discussion on the debian-project mailing list. That email boiled down to a simple request: can I have a "key dongles for dummies" tutorial? Key dongles, or keycards as we'll call them here, are small devices that allow users to store keys on an offline device and provide one possible solution for protecting private key material. In this article, I hope to use my experience in this domain to clarify the issue of how to store those precious private keys that, if compromised, could enable arbitrary code execution on millions of machines all over the world.

Why store keys offline? Before we go into details about storing keys offline, it may be useful to do a small reminder of how the OpenPGP standard works. OpenPGP keys are made of a main public/private key pair, the certification key, used to sign user identifiers and subkeys. My public key, shown below, has the usual main certification/signature key (marked SC) but also an encryption subkey (marked E), a separate signature key (S), and two authentication keys (marked A) which I use as RSA keys to log into servers using SSH, thanks to the Monkeysphere project.

    pub   rsa4096/792152527B75921E 2009-05-29 [SC] [expires: 2018-04-19]
      8DC901CE64146C048AD50FBB792152527B75921E
    uid                 [ultimate] Antoine Beaupr  <anarcat@anarc.at>
    uid                 [ultimate] Antoine Beaupr  <anarcat@koumbit.org>
    uid                 [ultimate] Antoine Beaupr  <anarcat@orangeseeds.org>
    uid                 [ultimate] Antoine Beaupr  <anarcat@debian.org>
    sub   rsa2048/B7F648FED2DF2587 2012-07-18 [A]
    sub   rsa2048/604E4B3EEE02855A 2012-07-20 [A]
    sub   rsa4096/A51D5B109C5A5581 2009-05-29 [E]
    sub   rsa2048/3EA1DDDDB261D97B 2017-08-23 [S]

All the subkeys (sub) and identities (uid) are bound by the main certification key using cryptographic self-signatures. So while an attacker stealing a private subkey can spoof signatures in my name or authenticate to other servers, that key can always be revoked by the main certification key. But if the certification key gets stolen, all bets are off: the attacker can create or revoke identities or subkeys as they wish. In a catastrophic scenario, an attacker could even steal the key and remove your copies, taking complete control of the key, without any possibility of recovery. Incidentally, this is why it is so important to generate a revocation certificate and store it offline. So by moving the certification key offline, we reduce the attack surface on the OpenPGP trust chain: day-to-day keys (e.g. email encryption or signature) can stay online but if they get stolen, the certification key can revoke those keys without having to revoke the main certification key as well. Note that a stolen encryption key is a different problem: even if we revoke the encryption subkey, this will only affect future encrypted messages. Previous messages will be readable by the attacker with the stolen subkey even if that subkey gets revoked, so the benefits of revoking encryption certificates are more limited.

Common strategies for offline key storage Considering the security tradeoffs, some propose storing those critical keys offline to reduce those threats. But where exactly? In an attempt to answer that question, Jonathan McDowell, a member of the Debian keyring maintenance team, said that there are three options: use an external LUKS-encrypted volume, an air-gapped system, or a keycard. Full-disk encryption like LUKS adds an extra layer of security by hiding the content of the key from an attacker. Even though private keyrings are usually protected by a passphrase, they are easily identifiable as a keyring. But when a volume is fully encrypted, it's not immediately obvious to an attacker there is private key material on the device. According to Sean Whitton, another advantage of LUKS over plain GnuPG keyring encryption is that you can pass the --iter-time argument when creating a LUKS partition to increase key-derivation delay, which makes brute-forcing much harder. Indeed, GnuPG 2.x doesn't have a run-time option to configure the key-derivation algorithm, although a patch was introduced recently to make the delay configurable at compile time in gpg-agent, which is now responsible for all secret key operations. The downside of external volumes is complexity: GnuPG makes it difficult to extract secrets out of its keyring, which makes the first setup tricky and error-prone. This is easier in the 2.x series thanks to the new storage system and the associated keygrip files, but it still requires arcane knowledge of GPG internals. It is also inconvenient to use secret keys stored outside your main keyring when you actually do need to use them, as GPG doesn't know where to find those keys anymore. Another option is to set up a separate air-gapped system to perform certification operations. An example is the PGP clean room project, which is a live system based on Debian and designed by DD Daniel Pocock to operate an OpenPGP and X.509 certificate authority using commodity hardware. The basic principle is to store the secrets on a different machine that is never connected to the network and, therefore, not exposed to attacks, at least in theory. I have personally discarded that approach because I feel air-gapped systems provide a false sense of security: data eventually does need to come in and out of the system, somehow, even if only to propagate signatures out of the system, which exposes the system to attacks. System updates are similarly problematic: to keep the system secure, timely security updates need to be deployed to the air-gapped system. A common use pattern is to share data through USB keys, which introduce a vulnerability where attacks like BadUSB can infect the air-gapped system. From there, there is a multitude of exotic ways of exfiltrating the data using LEDs, infrared cameras, or the good old TEMPEST attack. I therefore concluded the complexity tradeoffs of an air-gapped system are not worth it. Furthermore, the workflow for air-gapped systems is complex: even though PGP clean room went a long way, it's still lacking even simple scripts that allow signing or transferring keys, which is a problem shared by the external LUKS storage approach.

Keycard advantages The approach I have chosen is to use a cryptographic keycard: an external device, usually connected through the USB port, that stores the private key material and performs critical cryptographic operations on the behalf of the host. For example, the FST-01 keycard can perform RSA and ECC public-key decryption without ever exposing the private key material to the host. In effect, a keycard is a miniature computer that performs restricted computations for another host. Keycards usually support multiple "slots" to store subkeys. The OpenPGP standard specifies there are three subkeys available by default: for signature, authentication, and encryption. Finally, keycards can have an actual physical keypad to enter passwords so a potential keylogger cannot capture them, although the keycards I have access to do not feature such a keypad. We could easily draw a parallel between keycards and an air-gapped system; in effect, a keycard is a miniaturized air-gapped computer and suffers from similar problems. An attacker can intercept data on the host system and attack the device in the same way, if not more easily, because a keycard is actually "online" (i.e. clearly not air-gapped) when connected. The advantage over a fully-fledged air-gapped computer, however, is that the keycard implements only a restricted set of operations. So it is easier to create an open hardware and software design that is audited and verified, which is much harder to accomplish for a general-purpose computer. Like air-gapped systems, keycards address the scenario where an attacker wants to get the private key material. While an attacker could fool the keycard into signing or decrypting some data, this is possible only while the key is physically connected, and the keycard software will prompt the user for a password before doing the operation, though the keycard can cache the password for some time. In effect, it thwarts offline attacks: to brute-force the key's password, the attacker needs to be on the target system and try to guess the keycard's password, which will lock itself after a limited number of tries. It also provides for a clean and standard interface to store keys offline: a single GnuPG command moves private key material to a keycard (the keytocard command in the --edit-key interface), whereas moving private key material to a LUKS-encrypted device or air-gapped computer is more complex. Keycards are also useful if you operate on multiple computers. A common problem when using GnuPG on multiple machines is how to safely copy and synchronize private key material among different devices, which introduces new security problems. Indeed, a "good rule of thumb in a forensics lab", according to Robert J. Hansen on the GnuPG mailing list, is to "store the minimum personal data possible on your systems". Keycards provide the best of both worlds here: you can use your private key on multiple computers without actually storing it in multiple places. In fact, Mike Gerwitz went as far as saying:

For users that need their GPG key on multiple boxes, I consider a smartcard to be essential. Otherwise, the user is just furthering her risk of compromise.

Keycard tradeoffs As Gerwitz hinted, there are multiple downsides to using a keycard, however. Another DD, Wouter Verhelst clearly expressed the tradeoffs:

Smartcards are useful. They ensure that the private half of your key is never on any hard disk or other general storage device, and therefore that it cannot possibly be stolen (because there's only one possible copy of it). Smartcards are a pain in the ass. They ensure that the private half of your key is never on any hard disk or other general storage device but instead sits in your wallet, so whenever you need to access it, you need to grab your wallet to be able to do so, which takes more effort than just firing up GnuPG. If your laptop doesn't have a builtin cardreader, you also need to fish the reader from your backpack or wherever, etc.

"Smartcards" here refer to older OpenPGP cards that relied on the IEC 7816 smartcard connectors and therefore needed a specially-built smartcard reader. Newer keycards simply use a standard USB connector. In any case, it's true that having an external device introduces new issues: attackers can steal your keycard, you can simply lose it, or wash it with your dirty laundry. A laptop or a computer can also be lost, of course, but it is much easier to lose a small USB keycard than a full laptop and I have yet to hear of someone shoving a full laptop into a washing machine. When you lose your keycard, unless a separate revocation certificate is available somewhere, you lose complete control of the key, which is catastrophic. But, even if you revoke the lost key, you need to create a new one, which involves rebuilding the web of trust for the key a rather expensive operation as it usually requires meeting other OpenPGP users in person to exchange fingerprints. You should therefore think about how to back up the certification key, which is a problem that already exists for online keys; of course, everyone has a revocation certificates and backups of their OpenPGP keys... right? In the keycard scenario, backups may be multiple keycards distributed geographically. Note that, contrary to an air-gapped system, a key generated on a keycard cannot be backed up, by design. For subkeys, this is not a problem as they do not need to be backed up (except encryption keys). But, for a certification key, this means users need to generate the key on the host and transfer it to the keycard, which means the host is expected to have enough entropy to generate cryptographic-strength random numbers, for example. Also consider the possibility of combining different approaches: you could, for example, use a keycard for day-to-day operation, but keep a backup of the certification key on a LUKS-encrypted offline volume. Keycards introduce a new element into the trust chain: you need to trust the keycard manufacturer to not have any hostile code in the key's firmware or hardware. In addition, you need to trust that the implementation is correct. Keycards are harder to update: the firmware may be deliberately inaccessible to the host for security reasons or may require special software to manipulate. Keycards may be slower than the CPU in performing certain operations because they are small embedded microcontrollers with limited computing power. Finally, keycards may encourage users to trust multiple machines with their secrets, which works against the "minimum personal data" principle. A completely different approach called the trusted physical console (TPC) does the opposite: instead of trying to get private key material onto all of those machines, just have them on a single machine that is used for everything. Unlike a keycard, the TPC is an actual computer, say a laptop, which has the advantage of needing no special procedure to manage keys. The downside is, of course, that you actually need to carry that laptop everywhere you go, which may be problematic, especially in some corporate environments that restrict bringing your own devices.

Quick keycard "howto" Getting keys onto a keycard is easy enough:

1. Start with a temporary key to test the procedure:

       export GNUPGHOME=$(mktemp -d)
       gpg --generate-key
   

2. Edit the key using its user ID (UID):

       gpg --edit-key UID
   

3. Use the key command to select the first subkey, then copy it to the keycard (you can also use the addcardkey command to just generate a new subkey directly on the keycard):

       gpg> key 1
       gpg> keytocard
   

4. If you want to move the subkey, use the save command, which will remove the local copy of the private key, so the keycard will be the only copy of the secret key. Otherwise use the quit command to save the key on the keycard, but keep the secret key in your normal keyring; answer "n" to "save changes?" and "y" to "quit without saving?" . This way the keycard is a backup of your secret key.
5. Once you are satisfied with the results, repeat steps 1 through 4 with your normal keyring (unset $GNUPGHOME)

When a key is moved to a keycard, --list-secret-keys will show it as sec> (or ssb> for subkeys) instead of the usual sec keyword. If the key is completely missing (for example, if you moved it to a LUKS container), the # sign is used instead. If you need to use a key from a keycard backup, you simply do gpg --card-edit with the key plugged in, then type the fetch command at the prompt to fetch the public key that corresponds to the private key on the keycard (which stays on the keycard). This is the same procedure as the one to use the secret key on another computer.

Conclusion There are already informal OpenPGP best-practices guides out there and some recommend storing keys offline, but they rarely explain what exactly that means. Storing your primary secret key offline is important in dealing with possible compromises and we examined the main ways of doing so: either with an air-gapped system, LUKS-encrypted keyring, or by using keycards. Each approach has its own tradeoffs, but I recommend getting familiar with keycards if you use multiple computers and want a standardized interface with minimal configuration trouble. And of course, those approaches can be combined. This tutorial, for example, uses a keycard on an air-gapped computer, which neatly resolves the question of how to transmit signatures between the air-gapped system and the world. It is definitely not for the faint of heart, however. Once one has decided to use a keycard, the next order of business is to choose a specific device. That choice will be addressed in a followup article, where I will look at performance, physical design, and other considerations.

This article first appeared in the Linux Weekly News.

Changes

• myrepos: mention related software
• icns: OpenJPEG 2 fixes (1 2 3 4), fix minor buffer overrun
• check-all-the-things: fix cwd usage, dependencies updates (1, 2), increased verbosity, TODO items (for errcheck, coccinelle, DR.CHECKER, RATS, qmllint, xmlpatternsvalidator, gfapy-validate, phpstan, psalm, ansible-lint)
• spelling dictionaries:
  • codespell: delte, defualt, Debiab, aiffer, syntesis, reprociblbe, thether, suport, mimimum, isssue, reseting
  • lintian: delte, Debiab, aiffer, syntesis, reprociblbe
• Debian Planets: add BCCD, Pardus
• Debian derivatives census: improve db handling
• Debian PTS: fix backports issue
• Debian member portfolio: https (1, 2, 3), drop alioth files, fix duck & lists search
• Debian security tracker: BlueBourne NFUs, u-boot issues, kanboard CVE list fixes, fix version typo
• Debian puppet: SSL exception (1, 2), comment fixes
• Debian website: add missing section title
• Debian wiki pages: AutomaticPackagingTools, CrossCompiling, DebianDevelopment, DebianLive/buster, DebianYeeloong/ko, Derivatives/Census (QA, BCCD, EmmabuntusDE (1, 2), ev3dev, Netrunner (1, 2), Pardus), DeveloperNews, Diagrams, EmDebian/CrossDebootstrap, InstallingDebianOn/Asus/Transformer T300 Chi/Stretch, IRC, JamesAmontgomery, JensKorte/reportbug-by-mail, LocalGroupsTemplate, Mobile, MultimediaFetchingTools, OfflineMasterKey (1, 2), Outreachy/Round15 (Projects/SocialEventAndConferenceCalendars), PaulWise/InterestingSoftware, PortTemplate, qa.debian.org, research/publications, RISC-V, Sprints/2017/DebianCloudOct2017, SystemBuildTools, Teams (Dpkg/FAQ, Publicity/micronews, ReleaseTeam/ReleaseCheckList), template
• File Formats wiki pages: ZED (1, 2)

Issues

• Crashes in firefox-esr, lugaru, minetest-mod-animals
• Conffile removal in fonts-beng-extra
• Upstream renamed openggsn
• Strictness in ftp.d.o
• Features in unattended-upgrades
• Missing hashes in caffeine-developers PPA
• Missing conffile removal in di-netboot-assistant
• Incorrect upgrades in unattended-upgrades
• Incorrect URL in reproducible-check
• Verbosity in github-backup
• Minor issues in unattended-upgrades
• Usability issue in Firefox
• Upstreaming needed for Hone Linux-Sensor
• New upstream version of samba

Review

• Spam: reported 1 LWN comment, 5 Debian bug reports and 338 Debian mailing list posts
• Debian packages: sponsored minetest-mod-unifieddyes 20170925-1
• Debian wiki: RecentChanges for the month
• Debian screenshots:
  • approved banshee, blender, bsdgames, chromium, eficas, elpa-visual-fill-column, elpa-writegood-mode, glirc, gnome-builder, gnome-shell-extension-taskbar, gwenview, knocker, krita, ksysguard, masscan, mediainfo-gui, mousepad, mysql-workbench, nitrogen, ola, pavucontrol, qupzilla, tiger, transmission-gtk, virtualbox, vlc, wavemon, wfuzz
  • deleted mysql-workbench (ugly, Windows), udisks2 (of other software)
  • rejected elpa-* (MacOS and taken from upstream), 0ad (RPi logo), synaptic (weird overlaid stuff), dehydrated (hilarious but not a screenshot), di-netboot-assistant (of other software), wfuzz (help output)
  • approved deletion of udisks2 (of other software), scottfree (manual page), agenda.app (of other software)
  • rejected deletion of reportbug/abe/nlkt (bogus reason)

Administration

• icns: merged patches
• Debian: help guest user with access, investigate/escalate broken network, restart broken stunnels, investigate static.d.o storage, investigate weird RAID mails, ask hoster to investigate power issue,
• Debian mentors: lintian/security updates & reboot
• Debian wiki: merged & deployed patch, redirect DDTSS translator, redirect user support requests, whitelist email addresses, update email for accounts with bouncing email,
• Debian derivatives census: merged/deployed patches
• Debian PTS: debugged cron mails, deployed changes, reran scripts, fixed configuration file
• Openmoko: debug reboot issue, debug load issues

Communication

• Inform derivatives that are using Alioth about the pending shutdown
• Inquire about Netrunner, Pardus in the Debian derivatives census.
• Invite OB2D Linux to the Debian derivatives census
• Welcome Rohan Garg (of Netrunner), Aaron Weeden (of BCCD), Muhammet Kara (of Pardus) to the Debian derivatives census

Sponsors The samba bug was sponsored by my employer. All other work was done on a volunteer basis.