A shiny new release 0.2.4 of pkgKitten arrived on CRAN earlier, and has also been been uploaded to Debian. pkgKitten makes it simple to create new R packages via a simple function invocation. A wrapper kitten.r exists in the littler package to make it even easier. This release contains several improvements to the (optional) setup of the (wonderful) tinytest package, now supports the (now mandatory) Authors@R and polished a few aspect around the package repository and continuous integrations. The set of changes follows.

Changes in version 0.2.4 (2024-08-30)

The .Rbuildignore stanza now includes .github

The support of and usage illustrations of tinytest are much enhanced (Paul Hudor in #18 adressing #19 and #20)

The .gitignore file now includes C++ related files

Improvements and polish to badges and continuous integration

The DESCRIPTION file now contains an Authors@R entry

More details about the package are at the pkgKitten webpage, the pkgKitten docs site, and the pkgKitten GitHub repo. Courtesy of CRANberries, there is also a diffstat report for the most recent release. If you like this or other open-source work I do, you can sponsor me at GitHub.

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

Release 0.6.37 of the digest package arrived at CRAN today and has also been uploaded to Debian. digest creates hash digests of arbitrary R objects. It can use a number different hashing algorithms (md5, sha-1, sha-256, sha-512, crc32, xxhash32, xxhash64, murmur32, spookyhash, blake3,crc32c, xxh3_64 and xxh3_128), and enables easy comparison of (potentially large and nested) R language objects as it relies on the native serialization in R. It is a mature and widely-used package (with 70.8 million downloads just on the partial cloud mirrors of CRAN which keep logs) as many tasks may involve caching of objects for which it provides convenient general-purpose hash key generation to quickly identify the various objects. This release updates one of the different hashing source functions which, to remain close to their upstream, used Free() and Calloc() (uppercased to use the R allocator) but not the prefixed stricter versions R_Free() and R_Calloc(). R will switch to enforcing these in the next release next year. Kevin had noticed (while doing some other testing) that this now fails under R-devel (with a switch set), and prepares a very nice and clean PR to take care of it. As of today, CRAN is now sending please fix, or else notes so it was a good time to send this to CRAN. We also updated some remaining http URLs in the README.md to https, and switched to Author/Maintainer field to the now also mandatory Authors@R. My CRANberries provides a summary of changes to the previous version. For questions or comments use the issue tracker off the GitHub repo. For documentation (including the changelog) see the documentation site. If you like this or other open-source work I do, you can now sponsor me at GitHub.

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

Here comes the 3rd article of the 5-episode blog post series on Polis, written by Guido Berh rster, member of staff at my company Fre(i)e Software GmbH. Enjoy also this read on Guido's work on Polis,
Mike Table of Contents of the Blog Post Series

Introduction
Initial evaluation and adaptation
Issues extending Polis and adjusting our goals (this article)
Creating (a) new frontend(s) for Polis
Current status and roadmap

Polis - Issues extending Polis and adjusting our Goals After the initial implementation of limited branding support, user feedback and the involvement of an UX designer lead to the conclusion that we needed more far-reaching changes to the user interface in order to reduce visual clutter, rearrange and improve UI elements, and provide better integration with the websites in which conversations are embedded. Challenges when visualizing Data in Polis Polis visualizes groups using a spatial projection of users based on similarities in voting behavior and places them in two to five groups using a clustering algorithm. During our testing and evaluation users were rarely able to interpret the visualization and often intuitively made incorrect assumptions e.g. by associating the filled area of a group with its significance or size. After consultation with a member of the Multi-Agent Systems (MAS) Group at the University of Groningen we chose to temporarily replace the visualization offered by Polis with simple bar charts representing agreement or disagreement with statements of a group or the majority. We intend to revisit this and explore different forms of visualization at a later point in time. The different factors playing into the weight attached to statements which determine the pseuodo-random order in which they are presented for voting ( comment routing ) proved difficult to explain to stakeholders and users and the admission of the ad-hoc and heuristic nature of the used algorithm1 by Polis authors lead to the decision to temporarily remove this feature. Instead, statements should be placed into three groups, namely

metadata questions,
seed statements,
and participant statements

Statements should then be sorted by group but in a fully randomized order within the group so that metadata questions would be presented before seed statements which would be presented before participant s statements. This simpler method was deemed sufficient for the scale of our pilot projects, however we intend to revisit this decision and explore different methods of comment routing in cooperation with our scientific partners at a later point in time. An evaluation of the requirements for implementing mandatory authentication and adding support for additional authentication methods to Polis showed that significant changes to both the administration and participation frontend were needed due to a lack of an abstraction layer or extension mechanism and the current authentication providers being hardcoded in many parts of the code base. A New Frontend is born: Particiapp Based on the implementation details of the participation frontend, the invasive nature of the changes required, and the overhead of keeping up with active upstream development it became clear that a different, more flexible approach to development was needed. This ultimately lead to the creation of Particiapp, a new Open Source project providing the building blocks and necessary abstraction layers for rapid protoyping and experimentation with different fontends which are compatible with but independent from Polis.

Small, Christopher T., Bjorkegren, Michael, Erkkil , Timo, Shaw, Lynette and Megill, Colin (2021). Polis: Scaling deliberation by mapping high dimensional opinion spaces. Recerca. Revista de Pensament i An lisi, 26(2), pp. 1-26.

Prior to arrival in Kenya, you need to apply for an Electronic Travel Authorization (eTA) on their website by uploading all the required documents. This system is in place since Jan 2024 after the country abolished the visa system, implementing the eTA portal. The required documents will depend on the purpose of your visit, which in my case, was to attend a conference. Here is the list of documents I submitted for my eTA:

Scanned copy of my passport
Photograph with white background
Flight tickets (reservation)
Hotel bookings (reservation)
Invitation letter from the conference
Yellow Fever vaccination certificate (optional)
Job contract (optional)

Reservation means I didn t book the flights and hotels, but rather reserved them. Additionally, optional means that those documents were not mandatory to submit, but I submitted them in the Other Documents section in order to support my application. After submitting the eTA, I had to make a payment of around 35 US Dollars (approximately 3000 Indian Rupees). It took 40 hours for me to receive an email from Kenya stating that my eTA has been approved, along with an attached PDF, making this one of my smoothest experiences of obtaining travel documents to travel to a country :). An eTA is technically not a visa, but I put the word visa in the title due to familiarity with the term.

Debian packaging consists of a directory (debian/) containing a number of "hard-coded" filenames such as debian/control, debian/changelog, debian/copyright. In addition to these, many packages will also use a number of optional files that are named via a pattern such as debian/ PACKAGE .install. At a high level the patterns looks deceptively simple. However, if you start working on trying to automatically classify files in debian/ (which could be helpful to tell the user they have a typo in the filename), you will quickly realize these patterns are not machine friendly at all for this purpose.

The patterns deconstructed To appreciate the problem fully, here is a primer on the pattern and all its issues. If you are already well-versed in these, you might want to skip the section. The most common patterns are debian/package.stem or debian/stem and usually the go to example is the install stem ( a concrete example being debian/debhelper.install). However, the full pattern consists of 4 parts where 3 of them are optional.

The package name followed by a period. Optional, but must be the first if present.

The name segment followed by a period. Optional, but must appear between the package name (if present) and the stem. If the package name is not present, then the name segment must be first.

The stem. Mandatory.

An architecture restriction prefixed by a period. Optional, must appear after the stem if present.

To visualize it with [foo] to mark optional parts, it looks like debian/[PACKAGE.][NAME.]STEM[.ARCH] Detecting whether a given file is in fact a packaging file now boils down to reverse engineering its name against this pattern. Again, so far, it might still look manageable. One major complication is that every part (except ARCH) can contain periods. So a trivial "split by period" is not going to cut it. As an example:

debian/g++-3.0.user.service

This example is deliberately crafted to be ambiguous and show this problem in its full glory. This file name can be in multiple ways:

Is the stem service or user.service? (both are known stems from dh_installsystemd and dh_installsystemduser respectively). In fact, it can be both at the same time with "clever" usage of --name=user passed to dh_installsystemd.

The g++-3.0 can be a package prefix or part of the name segment. Even if there is a g++-3.0 package in debian/control, then debhelper (until compat 15) will still happily match this file for the main package if you pass --name=g++-3.0 to the helper. Side bar: Woe is you if there is a g++-3 and a g++-3.0 package in debian/control, then we have multiple options for the package prefix! Though, I do not think that happens in practice.

Therefore, there are a lot of possible ways to split this filename that all matches the pattern but with vastly different meaning and consequences.

Making detection practical To make this detection practical, lets look at the first problems that we need to solve.

We need the possible stems up front to have a chance at all. When multiple stems are an option, go for the longest match (that is, the one with most periods) since --name is rare and "code golfing" is even rarer.

We can make the package prefix mandatory for files with the name segment. This way, the moment there is something before the stem, we know the package prefix will be part of it and can cut it. It does not solve the ambiguity if one package name is a prefix of another package name (from the same source), but it still a lot better. This made its way into debhelper compat 15 and now it is "just" a slow long way to a better future.

A simple solution to the first problem could be to have a static list of known stems. That will get you started but the debhelper eco-system strive on decentralization, so this feels like a mismatch. There is also a second problem with the static list. Namely, a given stem is only "valid" if the command in question is actually in use. Which means you now need to dumpster dive into the mess that is Turning-complete debhelper configuration file known as debian/rules to fully solve that. Thanks to the Turning-completeness, we will never get a perfect solution for a static analysis. Instead, it is time to back out and instead apply some simplifications. Here is a sample flow:

Check whether the dh sequencer is used. If so, use some heuristics to figure out which addons are used.

Delegate to dh_assistant to figure out which commands will be used and which debhelper config file stems it knows about. Here we need to know which sequences are in use from step one (if relevant). Combine this with any other sources for stems you have.

Deconstruct all files in debian/ against the stems and known package names from debian/control. In theory, dumpster diving after --name options would be helpful here, but personally I skipped that part as I want to keep my debian/rules parsing to an absolute minimum.

With this logic, you can now:

Provide typo detection of the stem (debian/foo.intsall -> debian/foo.install) provided to have adequate handling of the corner cases (such as debian/*.conf not needing correction into debian/*.config)

Detect possible invalid package prefix (debian/foo.install without foo being a package). Note this has to be a weak warning unless the package is using debhelper compat 15 or you dumpster dived to validate that dh_install was not passed dh_install --name foo. Agreed, no one should do that, but they can and false positives are the worst kind of positives for a linting tool.

With some limitations, detect files used without the relevant command being active. As an example, the some integration modes of debputy removes dh_install, so a debian/foo.install would not be used.

Associate a given file with a given command to assist users with the documentation look up. Like debian/foo.user.service is related to dh_installsystemduser, so man dh_installsystemduser is a natural start for documentation.

I have added the logic for all these features in debputy though the documentation association is currently not in a user facing command. All the others are now diagnostics emitted by debputy in its editor support mode (debputy lsp server) or via debputy lint. In the editor mode, the diagnostics are currently associated with the package name in debian/control due to technical limitations of how the editor integration works. Some of these features will the latest version of debhelper (moving target at times). Check with debputy lsp features for the Extra dh support feature, which will be enabled if you got all you need. Note: The detection is currently (mostly) ignoring files with architecture restrictions. That might be lifted in the future. However, architecture restricted config files tend to be rare, so they were not a priority at this point. Additionally, debputy for technical reasons ignores stem typos with multiple matches. That sadly means that typos of debian/docs will often be unreported due to its proximity to debian/dirs and vice versa.

Diving a bit deeper on getting the stems To get the stems, debputy has 3 primary sources:

Its own plugins can provide packager provided files. These are only relevant if the package is using debputy.

It is als possible to provide a debputy plugin that identifies packaging files (either static or named ones). Though in practice, we probably do not want people to roll their own debputy plugin for this purpose, since the detection only works if the plugin is installed. I have used this mechanism to have debhelper provide a debhelper-documentation plugin to enrich the auto-detected data and we can assume most people interested in this feature would have debhelper installed.

It asks dh_assistant list-guessed-dh-config-files for config files, which is covered below.

The dh_assistant command uses the same logic as dh to identify the active add-ons and loads them. From there, it scans all commands mentioned in the sequence for the PROMISE: DH NOOP WITHOUT ...-hint and a new INTROSPECTABLE: CONFIG-FILES ...-hint. When these hints reference a packaging file (as an example, via pkgfile(foo)) then dh_assistant records that as a known packaging file for that helper. Additionally, debhelper now also tracks commands that were removed from the sequence. Several of the dh_assistant subcommand now use this to enrich their (JSON) output with notes about these commands being known but not active.

The end result With all of this work, you now get:

$ apt satisfy 'dh-debputy (>= 0.1.43~), debhelper (>= 13.16~), python3-lsprotocol, python3-levenshtein'
# For demo purposes, pull two known repos (feel free to use your own packages here)
$ git clone https://salsa.debian.org/debian/debhelper.git -b debian/13.16
$ git clone https://salsa.debian.org/debian/debputy.git -b debian/0.1.43
$ cd debhelper
$ mv debian/debhelper.install debian/debhelper.intsall
$ debputy lint
warning: File: debian/debhelper.intsall:1:0:1:0: The file "debian/debhelper.intsall" is likely a typo of "debian/debhelper.install"
    File-level diagnostic
$ mv debian/debhelper.intsall debian/debhleper.install
$ debputy lint
warning: File: debian/debhleper.install:1:0:1:0: Possible typo in "debian/debhleper.install". Consider renaming the file to "debian/debhelper.debhleper.install" or "debian/debhelper.install" if it is intended for debhelper
    File-level diagnostic
$ cd ../debputy
$ touch debian/install
$ debputy lint --no-warn-about-check-manifest
warning: File: debian/install:1:0:1:0: The file debian/install is related to a command that is not active in the dh sequence with the current addons
    File-level diagnostic

As mentioned, you also get these diagnostics in the editor via the debputy lsp server feature. Here the diagnostics appear in debian/control over the package name for technical reasons. The editor side still needs a bit more work. Notably, changes to the filename is not triggered automatically and will first be caught on the next change to debian/control. Likewise, changes to debian/rules to add --with to dh might also have some limitations depending on the editor. Saving both files and then triggering an edit of debian/control seems to work reliable but ideally it should not be that involved. The debhelper side could also do with some work to remove the unnecessary support for the name segment with many file stems that do not need them and announce that to debputy. Anyhow, it is still a vast improvement over the status quo that was "Why is my file silently ignored!?".

Here comes the 2nd article of the 5-episode blog post series written by Guido Berh rster, member of staff at my company Fre(i)e Software GmbH. Enjoy also this read on Guido's work on Polis,
Mike Table of Contents of the Blog Post Series

Introduction
Initial evaluation and adaptation (this article)
Issues extending Polis and adjusting our goals
Creating (a) new frontend(s) for Polis
Current status and roadmap

Polis - Initial evaluation and adaptation The Polis code base consists of a number of components, the administration and participation interfaces, a common web backend, and a statistics processing server. Both frontends and the backend are written in a mixture of JavaScript and TypeScript, only the statistics processing server is written in Clojure. In case of self hosting the preferred method of deployment is via Docker containers using Docker Compose or any other orchestrator. The participation frontend for conversations can either be used as a standalone web page or be embedded via an iframe. For our planned use case we initially defined the following goals:

custom branding and the integration into different content management systems (CMS)
better support for mobile devices
mandatory authentication and support for a broader range of authentication methods, including self-hosted solutions and DigiD
support for alternative email sending services
GDPR compliance

After a preliminary evaluation of our own and consulting with Policy Lab UK who were also evaluating and testing Polis and had already made a range of improvements related to self-hosting as well as bug fixes and modernization changes we decided to take their work as a base for our adaptations with the intent of submitting generally useful changes back to the Polis project. Subsequently, a number of changes were implemented, including the removal of hardcoded domain names, the elimination of unnecessary cookies and third-party requests, support for an alternative email sending service, and the option of disabling Facebook and X integration. For the branding our approach was to add an option allowing websites which are embedding conversations in an iframe to load an alternative stylesheet for overriding the native Polis branding. For this to be practical we intended to use CSS custom properties for defining branding-related styles such as colors and fonts. That approach turned out to be problematic because although the Polis participation frontend stylesheet is generated via SCSS and some of the colors are parameterized, however, they are not used consistently throughout the SCSS stylesheets, unfortunately. In addition the frontend templates contain a large amount of hardcoded style attributes. While we succeeded in implementing user-defined stylesheets, it took a disproportionate amount of development resources to parameterize all used colors and fonts via CSS custom properties aggravated by the fact that the SCSS and template files are huge and contain many unused rules and code.

I am getting increasingly frustrated by Fira Mono's lack of italic support so I am looking at alternative fonts again.

Commit Mono This time I seem to be settling on either Commit Mono or Space Mono. For now I'm using Commit Mono because it's a little more compressed than Fira and does have a italic version. I don't like how Space Mono's parenthesis (`()`) is "squarish", it feels visually ambiguous with the square brackets (`[]`), a big no-no for my primary use case (code). So here I am using a new font, again. It required changing a bunch of configuration files in my home directory (which is in a private repository, sorry) and Emacs configuration (thankfully that's public!). One gotcha is I realized I didn't actually have a global font configuration in Emacs, as some Faces define their own font family, which overrides the frame defaults. This is what it looks like, before:
Fira Mono
After:
Commit Mono
(Notice how those screenshots are not sharp? I'm surprised too. The originals look sharp on my display, I suspect this is something to do with the Wayland transition. I've tried with both grim and flameshot, for what its worth.) They are pretty similar! Commit Mono feels a bit more vertically compressed maybe too much so, actually -- the line height feels too low. But it's heavily customizable so that's something that's relatively easy to fix, if it's really a problem. Its weight is also a little heavier and wider than Fira which I find a little distracting right now, but maybe I'll get used to it. All characters seem properly distinguishable, although, if I'd really want to nitpick I'd say the and are too different, with the latter (`REGISTERED SIGN`) being way too small, basically unreadable here. Since I see this sign approximately never, it probably doesn't matter at all. I like how the ampersand (`&`) is more traditional, although I'll miss the exotic one Fira produced... I like how the back quotes ( , `GRAVE ACCENT`) drop down low, nicely aligned with the apostrophe. As I mentioned before, I like how the bar on the "f" aligns with the other top of letters, something in Fira mono that really annoys me now that I've noticed it (it's not aligned!).

A UTF-8 test file Here's the test sheet I've made up to test various characters. I could have sworn I had a good one like this lying around somewhere but couldn't find it so here it is, I guess.

US keyboard coverage:
abcdefghijklmnopqrstuvwxyz 1234567890-=[]\;',./
ABCDEFGHIJKLMNOPQRSTUVWXYZ~!@#$%^&*()_+ :"<>?
latin1 coverage:  
EURO SIGN, TRADE MARK SIGN:  
ambiguity test:
e coC0ODQ iI71lL! 
b6G&0B83  []() /\. 
zs$S52Z%   '" 
all characters in a sentence, uppercase:
the quick fox jumps over the lazy dog
THE QUICK FOX JUMPS OVER THE LAZY DOG
same, in french:
Portez ce vieux whisky au juge blond qui fume.
d s no l, o  un z phyr ha  me v t de gla ons w rmiens, je d ne
d exquis r tis de b uf au kir,   l a  d ge m r, &c tera.
D S NO L, O  UN Z PHYR HA  ME V T DE GLA ONS W RMIENS, JE D NE
D EXQUIS R TIS DE B UF AU KIR,   L A  D GE M R, &C TERA.
Ligatures test:
-<< -< -<- <-- <--- <<- <- -> ->> --> ---> ->- >- >>-
=<< =< =<= <== <=== <<= <= => =>> ==> ===> =>= >= >>=
<-> <--> <---> <----> <=> <==> <===> <====> :: ::: __
<~~ </ </> /> ~~> == != /= ~= <> === !== !=== =/= =!=
<: := *= *+ <* <*> *> <  < >  > <. <.> .> +* =* =: :>
(* *) /* */ [   ]     ++ +++ \/ /\  - -  <!-- <!---
Box drawing alignment tests:
                                                                    
                                 
                           
                                                   
                                       
                                                 
                               
                                
Dashes alignment test:
HYPHEN-MINUS, MINUS SIGN, EN, EM DASH, HORIZONTAL BAR, LOW LINE
--------------------------------------------------
 
 
 
 
__________________________________________________

Update: here is another such sample sheet, it's pretty good and has support for more languages while being still relatively small. So there you have it, got completely nerd swiped by typography again. Now I can go back to writing a too-long proposal again. Sources and inspiration for the above:

the unicode(1) command, to lookup individual characters to disambiguate, for example, - (U+002D HYPHEN-MINUS, the minus sign next to zero on US keyboards) and (U+2212 MINUS SIGN, a math symbol)
searchable list of characters and their names - roughly equivalent to the unicode(1) command, but in one page, amazingly the /usr/share/unicode database doesn't have any one file like this
bits/UTF-8-Unicode-Test-Documents - full list of UTF-8 characters
UTF-8 encoded plain text file - nice examples of edge cases, curly quotes example and box drawing alignment test which, incidentally, showed me I needed specific faces customisation in Emacs to get the Markdown code areas to display properly, also the idea of comparing various dashes
sample sentences in many languages - unused, "Sentences that contain all letters commonly used in a language"
UTF-8 sampler - unused, similar

New features The new option `--no-strict-pinning` instructs the solver to consider all versions of a package and not just the candidate version. For example, you could use `apt install foo=2.0 --no-strict-pinning` to install version 2.0 of foo and upgrade - or downgrade - packages as needed to satisfy `foo=2.0` dependencies. This mostly comes in handy in use cases involving Debian experimental or the Ubuntu proposed pockets, where you want to install a package from there, but try to satisfy from the normal release as much as possible. The implication graph building allows us to implement an `apt why` command, that while not as nicely detailed as aptitude, at least tells you the exact reason why a package is installed. It will only show the strongest dependency chain at first of course, since that is what we record.

What is left to do? At the moment, error information is not stored across backtracking in any way, but we generally will want to show you the first conflict we reach as it is the most natural one; or all conflicts. Currently you get the last conflict which may not be particularly useful. Likewise, errors currently are just rendered as implication graphs of the form `[not] A -> [not] B -> ...`, and we need to put in some work to present those nicely. The test suite is not passing yet, I haven t really started working on it. A challenge is that most packages in the test suite are manually installed as they are mocked, and the solver now doesn t remove those. We plan to implement the replacement logic such that foo can be replaced by `foo2 Conflicts/Replaces/Provides foo` without needing to be automatically installed. Improving the backtracking to be non-chronological conflict-driven clause learning would vastly enhance our backtracking performance. Not that it seems to be an issue right now in my limited testing (mostly noble 64-bit-time_t upgrades). A lot of that complexity you have normally is not there because the manually installed packages and resulting unit propagation (single-solution Depends/Reverse-Depends for Conflicts) already ground us fairly far in what changes we can actually make. Once all the stuff has landed, we need to start rolling it out and gather feedback. On Ubuntu I d like automated feedback on regressions (running solver3 in parallel, checking if result is worse and then submitting an error to the error tracker), on Debian this could just be a role email address to send solver dumps to. At the same time, we can also incrementally start rolling this out. Like phased updates in Ubuntu, we can also roll out the new solver as the default to 10%, 20%, 50% of users before going to the full 100%. This will allow us to capture regressions early and fix them.

About a month ago, Otto Kek l inen asked for editor extensions for debian related files on the debian-devel mailing list. In that thread, I concluded that what we were missing was a "Language Server" (LSP) for our packaging files. Last week, I started a prototype for such a LSP for the debian/control file as a starting point based on the pygls library. The initial prototype worked and I could do very basic diagnostics plus completion suggestion for field names.

Current features I got 4 basic features implemented, though I have only been able to test two of them in emacs.

Diagnostics or linting of basic issues.

Completion suggestions for all known field names that I could think of and values for some fields.

Folding ranges (untested). This feature enables the editor to "fold" multiple lines. It is often used with multi-line comments and that is the feature currently supported.

On save, trim trailing whitespace at the end of lines (untested). Might not be registered correctly on the server end.

Despite its very limited feature set, I feel editing debian/control in emacs is now a much more pleasant experience. Coming back to the features that Otto requested, the above covers a grand total of zero. Sorry, Otto. It is not you, it is me.

Completion suggestions For completion, all known fields are completed. Place the cursor at the start of the line or in a partially written out field name and trigger the completion in your editor. In my case, I can type R-R-R and trigger the completion and the editor will automatically replace it with Rules-Requires-Root as the only applicable match. Your milage may vary since I delegate most of the filtering to the editor, meaning the editor has the final say about whether your input matches anything. The only filtering done on the server side is that the server prunes out fields already used in the paragraph, so you are not presented with the option to repeat an already used field, which would be an error. Admittedly, not an error the language server detects at the moment, but other tools will. When completing field, if the field only has one non-default value such as Essential which can be either no (the default, but you should not use it) or yes, then the completion suggestion will complete the field along with its value. This is mostly only applicable for "yes/no" fields such as Essential and Protected. But it does also trigger for Package-Type at the moment. As for completing values, here the language server can complete the value for simple fields such as "yes/no" fields, Multi-Arch, Package-Type and Priority. I intend to add support for Section as well - maybe also Architecture.

Diagnostics On the diagnostic front, I have added multiple diagnostics:

An error marker for syntax errors.

An error marker for missing a mandatory field like Package or Architecture. This also includes Standards-Version, which is admittedly mandatory by policy rather than tooling falling part.

An error marker for adding Multi-Arch: same to an Architecture: all package.

Error marker for providing an unknown value to a field with a set of known values. As an example, writing foo in Multi-Arch would trigger this one.

Warning marker for using deprecated fields such as DM-Upload-Allowed, or when setting a field to its default value for fields like Essential. The latter rule only applies to selected fields and notably Multi-Arch: no does not trigger a warning.

Info level marker if a field like Priority duplicates the value of the Source paragraph.

Notable omission at this time:

No errors are raised if a field does not have a value.

No errors are raised if a field is duplicated inside a paragraph.

No errors are used if a field is used in the wrong paragraph.

No spellchecking of the Description field.

No understanding that Foo and X[CBS]-Foo are related. As an example, XC-Package-Type is completely ignored despite being the old name for Package-Type.

Quick fixes to solve these problems... :)

Trying it out If you want to try, it is sadly a bit more involved due to things not being uploaded or merged yet. Also, be advised that I will regularly rebase my git branches as I revise the code. The setup:

Build and install the deb of the main branch of pygls from https://salsa.debian.org/debian/pygls The package is in NEW and hopefully this step will soon just be a regular apt install.

Build and install the deb of the rts-locatable branch of my python-debian fork from https://salsa.debian.org/nthykier/python-debian There is a draft MR of it as well on the main repo.

Build and install the deb of the lsp-support branch of debputy from https://salsa.debian.org/debian/debputy

Configure your editor to run debputy lsp debian/control as the language server for debian/control. This is depends on your editor. I figured out how to do it for emacs (see below). I also found a guide for neovim at https://neovim.io/doc/user/lsp. Note that debputy can be run from any directory here. The debian/control is a reference to the file format and not a concrete file in this case.

Obviously, the setup should get easier over time. The first three bullet points should eventually get resolved by merges and upload meaning you end up with an apt install command instead of them. For the editor part, I would obviously love it if we can add snippets for editors to make the automatically pick up the language server when the relevant file is installed.

Using the debputy LSP in emacs The guide I found so far relies on eglot. The guide below assumes you have the elpa-dpkg-dev-el package installed for the debian-control-mode. Though it should be a trivially matter to replace debian-control-mode with a different mode if you use a different mode for your debian/control file. In your emacs init file (such as ~/.emacs or ~/.emacs.d/init.el), you add the follow blob.

(with-eval-after-load 'eglot
    (add-to-list 'eglot-server-programs
        '(debian-control-mode . ("debputy" "lsp" "debian/control"))))

Once you open the debian/control file in emacs, you can type M-x eglot to activate the language server. Not sure why that manual step is needed and if someone knows how to automate it such that eglot activates automatically on opening debian/control, please let me know. For testing completions, I often have to manually activate them (with C-M-i or M-x complete-symbol). Though, it is a bit unclear to me whether this is an emacs setting that I have not toggled or something I need to do on the language server side.

From here As next steps, I will probably look into fixing some of the "known missing" items under diagnostics. The quick fix would be a considerable improvement to assisting users. In the not so distant future, I will probably start to look at supporting other files such as debian/changelog or look into supporting configuration, so I can cover formatting features like wrap-and-sort. I am also very much open to how we can provide integrations for this feature into editors by default. I will probably create a separate binary package for specifically this feature that pulls all relevant dependencies that would be able to provide editor integrations as well.

Debian Public Statement about the EU Cyber Resilience Act and the Product Liability Directive The European Union is currently preparing a regulation "on horizontal cybersecurity requirements for products with digital elements" known as the Cyber Resilience Act (CRA). It is currently in the final "trilogue" phase of the legislative process. The act includes a set of essential cybersecurity and vulnerability handling requirements for manufacturers. It will require products to be accompanied by information and instructions to the user. Manufacturers will need to perform risk assessments and produce technical documentation and, for critical components, have third-party audits conducted. Discovered security issues will have to be reported to European authorities within 25 hours (1). The CRA will be followed up by the Product Liability Directive (PLD) which will introduce compulsory liability for software. While a lot of these regulations seem reasonable, the Debian project believes that there are grave problems for Free Software projects attached to them. Therefore, the Debian project issues the following statement:

Free Software has always been a gift, freely given to society, to take and to use as seen fit, for whatever purpose. Free Software has proven to be an asset in our digital age and the proposed EU Cyber Resilience Act is going to be detrimental to it. a. As the Debian Social Contract states, our goal is "make the best system we can, so that free works will be widely distributed and used." Imposing requirements such as those proposed in the act makes it legally perilous for others to redistribute our work and endangers our commitment to "provide an integrated system of high-quality materials with no legal restrictions that would prevent such uses of the system". (2) b. Knowing whether software is commercial or not isn't feasible, neither in Debian nor in most free software projects - we don't track people's employment status or history, nor do we check who finances upstream projects (the original projects that we integrate in our operating system). c. If upstream projects stop making available their code for fear of being in the scope of CRA and its financial consequences, system security will actually get worse rather than better. d. Having to get legal advice before giving a gift to society will discourage many developers, especially those without a company or other organisation supporting them.
Debian is well known for its security track record through practices of responsible disclosure and coordination with upstream developers and other Free Software projects. We aim to live up to the commitment made in the Debian Social Contract: "We will not hide problems." (3) a.The Free Software community has developed a fine-tuned, tried-and-tested system of responsible disclosure in case of security issues which will be overturned by the mandatory reporting to European authorities within 24 hours (Art. 11 CRA). b. Debian spends a lot of volunteering time on security issues, provides quick security updates and works closely together with upstream projects and in coordination with other vendors. To protect its users, Debian regularly participates in limited embargos to coordinate fixes to security issues so that all other major Linux distributions can also have a complete fix when the vulnerability is disclosed. c. Security issue tracking and remediation is intentionally decentralized and distributed. The reporting of security issues to ENISA and the intended propagation to other authorities and national administrations would collect all software vulnerabilities in one place. This greatly increases the risk of leaking information about vulnerabilities to threat actors, representing a threat for all the users around the world, including European citizens. d. Activists use Debian (e.g. through derivatives such as Tails), among other reasons, to protect themselves from authoritarian governments; handing threat actors exploits they can use for oppression is against what Debian stands for. e. Developers and companies will downplay security issues because a "security" issue now comes with legal implications. Less clarity on what is truly a security issue will hurt users by leaving them vulnerable.
While proprietary software is developed behind closed doors, Free Software development is done in the open, transparent for everyone. To retain parity with proprietary software the open development process needs to be entirely exempt from CRA requirements, just as the development of software in private is. A "making available on the market" can only be considered after development is finished and the software is released.
Even if only "commercial activities" are in the scope of CRA, the Free Software community - and as a consequence, everybody - will lose a lot of small projects. CRA will force many small enterprises and most probably all self employed developers out of business because they simply cannot fulfill the requirements imposed by CRA. Debian and other Linux distributions depend on their work. If accepted as it is, CRA will undermine not only an established community but also a thriving market. CRA needs an exemption for small businesses and, at the very least, solo-entrepreneurs.

Information about the voting process: Debian uses the Condorcet method for voting. Simplistically, plain Condorcets method can be stated like so : "Consider all possible two-way races between candidates. The Condorcet winner, if there is one, is the one candidate who can beat each other candidate in a two-way race with that candidate." The problem is that in complex elections, there may well be a circular relationship in which A beats B, B beats C, and C beats A. Most of the variations on Condorcet use various means of resolving the tie. Debian's variation is spelled out in the constitution, specifically, A.5(3) Sources: (1) CRA proposals and links & PLD proposals and links (2) Debian Social Contract No. 2, 3, and 4 (3) Debian Constitution

Today, 12 years after the meeting where AppStream was first discussed and 11 years after I released a prototype implementation I am excited to announce AppStream 1.0!

Check it out on GitHub, or get the release tarball or read the documentation or release notes!

Some nostalgic memories I was not in the original AppStream meeting, since in 2011 I was extremely busy with finals preparations and ball organization in high school, but I still vividly remember sitting at school in the students lounge during a break and trying to catch the really choppy live stream from the meeting on my borrowed laptop (a futile exercise, I watched parts of the blurry recording later). I was extremely passionate about getting software deployment to work better on Linux and to improve the overall user experience, and spent many hours on the PackageKit IRC channel discussing things with many amazing people like Richard Hughes, Daniel Nicoletti, Sebastian Heinlein and others. At the time I was writing a software deployment tool called Listaller this was before Linux containers were a thing, and building it was very tough due to technical and personal limitations (I had just learned C!). Then in university, when I intended to recreate this tool, but for real and better this time as a new project called Limba, I needed a way to provide metadata for it, and AppStream fit right in! Meanwhile, Richard Hughes was tackling the UI side of things while creating GNOME Software and needed a solution as well. So I implemented a prototype and together we pretty much reshaped the early specification from the original meeting into what would become modern AppStream. Back then I saw AppStream as a necessary side-project for my actual project, and didn t even consider me as the maintainer of it for quite a while (I hadn t been at the meeting afterall). All those years ago I had no idea that ultimately I was developing AppStream not for Limba, but for a new thing that would show up later, with an even more modern design called Flatpak. I also had no idea how incredibly complex AppStream would become and how many features it would have and how much more maintenance work it would be and also not how ubiquitous it would become. The modern Linux desktop uses AppStream everywhere now, it is supported by all major distributions, used by Flatpak for metadata, used for firmware metadata via Richard s fwupd/LVFS, runs on every Steam Deck, can be found in cars and possibly many places I do not know yet.

What is new in 1.0?

API breaks The most important thing that s new with the 1.0 release is a bunch of incompatible changes. For the shared libraries, all deprecated API elements have been removed and a bunch of other changes have been made to improve the overall API and especially make it more binding-friendly. That doesn t mean that the API is completely new and nothing looks like before though, when possible the previous API design was kept and some changes that would have been too disruptive have not been made. Regardless of that, you will have to port your AppStream-using applications. For some larger ones I already submitted patches to build with both AppStream versions, the 0.16.x stable series as well as 1.0+. For the XML specification, some older compatibility for XML that had no or very few users has been removed as well. This affects for example `release` elements that reference downloadable data without an `artifact` block, which has not been supported for a while. For all of these, I checked to remove only things that had close to no users and that were a significant maintenance burden. So as a rule of thumb: If your XML validated with no warnings with the 0.16.x branch of AppStream, it will still be 100% valid with the 1.0 release. Another notable change is that the generated output of AppStream 1.0 will always be 1.0 compliant, you can not make it generate data for versions below that (this greatly reduced the maintenance cost of the project).

Developer element For a long time, you could set the developer name using the top-level `developer_name` tag. With AppStream 1.0, this is changed a bit. There is now a `developer` tag with a `name` child (that can be translated unless the `translate="no"` attribute is set on it). This allows future extensibility, and also allows to set a machine-readable `id` attribute in the `developer` element. This permits software centers to group software by developer easier, without having to use heuristics. If we decide to extend the developer information per-app in future, this is also now possible. Do not worry though the `developer_name` tag is also still read, so there is no high pressure to update. The old 0.16.x stable series also has this feature backported, so it can be available everywhere. Check out the developer tag specification for more details.

Scale factor for screenshots Screenshot images can now have a `scale` attribute, to indicate an (integer) scaling factor to apply. This feature was a breaking change and therefore we could not have it for the longest time, but it is now available. Please wait a bit for AppStream 1.0 to become deployed more widespread though, as using it with older AppStream versions may lead to issues in some cases. Check out the screenshots tag specification for more details.

Screenshot environments It is now possible to indicate the environment a screenshot was recorded in (GNOME, GNOME Dark, KDE Plasma, Windows, etc.) via an `environment` attribute on the respective `screenshot` tag. This was also a breaking change, so use it carefully for now! If projects want to, they can use this feature to supply dedicated screenshots depending on the environment the application page is displayed in. Check out the screenshots tag specification for more details.

References tag This is a feature more important for the scientific community and scientific applications. Using the `references` tag, you can associate the AppStream component with a DOI (Digital object identifier) or provide a link to a CFF file to provide citation information. It also allows to link to other scientific registries. Check out the references tag specification for more details.

Release tags Releases can have tags now, just like components. This is generally not a feature that I expect to be used much, but in certain instances it can become useful with a cooperating software center, for example to tag certain releases as long-term supported versions.

Multi-platform support Thanks to the interest and work of many volunteers, AppStream (mostly) runs on FreeBSD now, a NetBSD port exists, support for macOS was written and a Windows port is on its way! Thank you to everyone working on this

Better compatibility checks For a long time I thought that the AppStream library should just be a thin layer above the XML and that software centers should just implement a lot of the actual logic. This has not been the case for a while, but there was still a lot of complex AppStream features that were hard for software centers to implement and where it makes sense to have one implementation that projects can just use. The validation of component relations is one such thing. This was implemented in 0.16.x as well, but 1.0 vastly improves upon the compatibility checks, so you can now just run as_component_check_relations and retrieve a detailed list of whether the current component will run well on the system. Besides better API for software developers, the `appstreamcli` utility also has much improved support for relation checks, and I wrote about these changes in a previous post. Check it out! With these changes, I hope this feature will be used much more, and beyond just drivers and firmware.

So much more! The changelog for the 1.0 release is huge, and there are many papercuts resolved and changes made that I did not talk about here, like us using gi-docgen (instead of gtkdoc) now for nice API documentation, or the many improvements that went into better binding support, or better search, or just plain bugfixes.

Outlook I expect the transition to 1.0 to take a bit of time. AppStream has not broken its API for many, many years (since 2016), so a bunch of places need to be touched even if the changes themselves are minor in many cases. In hindsight, I should have also released 1.0 much sooner and it should not have become such a mega-release, but that was mainly due to time constraints. So, what s in it for the future? Contrary to what I thought, AppStream does not really seem to be done and fetature complete at a point, there is always something to improve, and people come up with new usecases all the time. So, expect more of the same in future: Bugfixes, validator improvements, documentation improvements, better tools and the occasional new feature. Onwards to 1.0.1!

A trip full of hitchhiking, beautiful places and welcoming locals.

Day 1: Arrival in Kochi Kochi is a city in the state of Kerala, India. This year s DebConf was to be held in Kochi from 3rd September to 17th of September, which I was planning to attend. My friend Suresh, who was planning to join, told me that 29th August 2023 will be Onam, a major festival of the state of Kerala. So, we planned a Kerala trip before the DebConf. We booked early morning flights for Kochi from Delhi and reached Kochi on 28th August. We had booked a hostel named Zostel in Ernakulam. During check-in, they asked me to fill a form which required signing in using a Google account. I told them I don t have a Google account and I don t want to create one either. The people at the front desk seemed receptive, so I went ahead with telling them the problems of such a sign-in being mandatory for check-in. Anyways, they only took a photo of my passport and let me check-in without a Google account. We stayed in a ten room dormitory, which allowed travellers of any gender. The dormitory room was air-conditioned, spacious, clean and beds were also comfortable. There were two bathrooms in the dormitory and they were clean. Plus, there was a separate dormitory room in the hostel exclusive for females. I noticed that that Zostel was not added in the OpenStreetMap and so, I added it :) . The hostel had a small canteen for tea and snacks, a common sitting area outside the dormitories, which had beds too. There was a separate silent room, suitable for people who want to work.
Dormitory room in Zostel Ernakulam, Kochi.

Beds in Zostel Ernakulam, Kochi.
We had lunch at a nearby restaurant and it was hard to find anything vegetarian for me. I bought some freshly made banana chips from the street and they were tasty. As far as I remember, I had a big glass of pineapple juice for lunch. Then I went to the Broadway market and bought some cardamom and cinnamon for home. I also went to a nearby supermarket and bought Matta brown rice for home. Then, I looked for a courier shop to send the things home but all of them were closed due to Onam festival. After returning to the Zostel, I overslept till 9 PM and in the meanwhile, Suresh planned with Saidut and Shwetank (who met us during our stay in Zostel) to go to a place in Fort Kochi for dinner. I suspected I will be disappointed by lack of vegetarian options as they were planning to have fish. I already had a restaurant in mind - Brindhavan restaurant (suggested by Anupa), which was a pure vegetarian restaurant. To reach there, I got off at Palarivattom metro station and started looking for an auto-rickshaw to get to the restaurant. I didn t get any for more than 5 minutes. Since that restaurant was not added to the OpenStreetMap, I didn t even know how far that was and which direction to go to. Then, I saw a Zomato delivery person on a motorcycle and asked him where the restaurant was. It was already 10 PM and the restaurant closes at 10:30. So, I asked him whether he can drop me off. He agreed and dropped me off at that restaurant. It was 4-5 km from that metro station. I tipped him and expressed my gratefulness for the help. He refused to take the tip, but I insisted and he accepted. I entered the restaurant and it was coming to a close, so many items were not available. I ordered some Kadhai Paneer (only item left) with naan. It tasted fine. Since the next day was Thiruvonam, I asked the restaurant about the Sadya thali menu and prices for the next day. I planned to eat Sadya thali at that restaurant, but my plans got changed later.
Onam sadya menu from Brindhavan restaurant.

Day 2: Onam celebrations Next day, on 29th of August 2023, we had plan to leave for Wayanad. Wayanad is a hill station in Kerala and a famous tourist spot. Praveen suggested to visit Munnar as it is far closer to Kochi than Wayanad (80 km vs 250 km). But I had already visited Munnar in my previous trips, so we chose Wayanad. We had a train late night from Ernakulam Junction (at 23:30 hours) to Kozhikode, which is the nearest railway station from Wayanad. So, we checked out in the morning as we had plans to roam around in Kochi before taking the train. Zostel was celebrating Onam on that day. To opt-in, we had to pay 400 rupees, which included a Sadya Thali and a mundu. Me and Suresh paid the amount and opted in for the celebrations. Sadya thali had Rice, Sambhar, Rasam, Avial, Banana Chips, Pineapple Pachadi, Pappadam, many types of pickels and chutneys, Pal Ada Payasam and Coconut jaggery Pasam. And, there was water too :). Those payasams were really great and I had one more round of them. Later, I had a lot of variety of payasams during the DebConf.
Sadya lined up for serving

Sadya thali served on banana leaf.
So, we hung out in the common room and put our luggage there. We played UNO and had conversations with other travellers in the hostel. I had a fun time there and I still think it is one of the best hostel experiences I had. We made good friends with Saiduth (Telangana) and Shwetank (Uttarakhand). They were already aware about the software like debian, and we had some detailed conversations about the Free Software movement. I remember explaining the difference between the terms Open Source and Free Software . I also told them about the Streetcomplete app, a beginner friendly app to edit OpenStreetMap. We had dinner at a place nearby (named Palaraam), but again, the vegetarian options were very limited! After dinner, we came back to the Zostel and me and Suresh left for Ernakulam Junction to catch our train Maveli Express (16604).

Day 3: Going to Wayanad Maveli Express was scheduled to reach Kozhikode at 03:25 (morning). I had set alarms from 03:00 to 03:30, with the gap of 10 minutes. Every time I woke up, I turned off the alarm. Then I woke up and saw train reaching the Kozhikode station and woke up Suresh for deboarding. But then I noticed that the train is actually leaving the station, not arriving! This means we missed our stop. Now we looked at the next stops and whether we can deboard there. I was very sleepy and wanted to take a retiring room at some station before continuing our journey to Wayanad. The next stop was Quilandi and we checked online that it didn t have a retiring room. So, we skipped this stop. We got off at the next stop named Vadakara and found out no retiring room was available. So, we asked about information regarding bus for Wayanad and they said that there is a bus to Wayanad around 07:00 hours from bus station which was a few kilometres from the railway station. We took a bus for Kalpetta (in Wayanad) at around 07:00. The destination of the buses were written in Malayalam, which we could not read. Once again, the locals helped us to get on to the bus to Kalpetta. Vadakara is not a big city and it can be hard to find people who know good Hindi or English, unlike Kochi. Despite language issues, I had no problem there in navigation, thanks to locals. I mostly spent time sleeping during the bus journey. A few hours later, the bus dropped us at Kalpetta. We had a booking at a hostel in Rippon village. It was 16 km from Kalpetta. On the way, we were treated with beautiful views of nature, which was present everywhere in Wayanad. The place was covered with tea gardens and our eyes were treated with beautiful scenery at every corner.
We were treated with such views during the Wayanad trip.
Rippon village was a very quiet place and I liked the calm atmosphere. This place is blessed by nature and has stunning scenery. I found English was more common than Hindi in Wayanad. Locals were very nice and helped me, even if they didn t know my language.
A road in Rippon.
After catching some sleep at the hostel, I went out in the afternoon. I hitchhiked to reach the main road from the hostel. I bought more spices from a nearby shop and realized that I should have waited for my visit to Wayanad to buy cardamom, which I already bought from Kochi. Then, I was looking for post office to send spices home. The people at the spices shop told me that the nearby Rippon post office was closed by that time, but the post office at Meppadi was open, which was 5 km from there. I went to Meppadi and saw the post office closes at 15:00, but I reached five minutes late. My packing was not very good and they asked me to pack it tighter. There was a shop near the post office and the people there gave me a cardboard and tapes, and helped pack my stuff for the post. By the time I went to the post office again, it was 15:30. But they accepted my parcel for post.

Day 4: Kanthanpara Falls, Zostel Wayanad and Karapuzha Dam Kanthanpara waterfalls were 2 km from the hostel. I hitchhiked to the place from the hostel on a scooty. Entry ticket was worth Rs 40. There were good views inside and nothing much to see except the waterfalls.
Entry to Kanthanpara Falls.

Kanthanpara Falls.
We had a booking at Zostel Wayanad for this day and so we shifted there. Again, as with their Ernakulam branch, they asked me to fill a form which required signing in using Google, but when I said I don t have a Google account they checked me in without that. There were tea gardens inside the Zostel boundaries and the property was beautiful.
A view of Zostel Wayanad.

A map of Wayanad showing tourist places.

A view from inside the Zostel Wayanad property.
Later in the evening, I went to Karapuzha Dam. I witnessed a beautiful sunset during the journey. Karapuzha dam had many activites, like ziplining, and was nice to roam around. Chembra Peak is near to the Zostel Wayanad. So, I was planning to trek to the heart shaped lake. It was suggested by Praveen and looking online, this trek seemed worth doing. There was an issue however. The charges for trek were Rs 1770 for upto five people. So, if I go alone I will have to spend Rs 1770 for the trek. If I go with another person, we split Rs 1770 into two, and so on. The optimal way to do it is to go in a group of five (you included :D). I asked front desk at Zostel if they can connect me with people going to Chembra peak the next day, and they told me about a group of four people planning to go to Chembra peak the next day. I got lucky! All four of them were from Kerala and worked in Qatar.

Day 5: Chembra peak trek The date was 1st September 2023. I woke up early (05:30 in the morning) for the Chembra peak trek. I had bought hiking shoes especially for trekking, which turned out to be a very good idea. The ticket counter opens at 07:00. The group of four with which I planned to trek met me around 06:00 in the Zostel. We went to the ticket counter around 06:30. We had breakfast at shops selling Maggi noodles and bread omlette near the ticket counter. It was a hot day and the trek was difficult for an inexperienced person like me. The scenery was green and beautiful throughout.
Terrain during trekking towards the Chembra peak.

Heart-shaped lake at the Chembra peak.

Me at the heart-shaped lake.

Views from the top of the Chembra peak.

View of another peak from the heart-shaped lake.
While returning from the trek, I found out a shop selling bamboo rice, which I bought and will make bamboo rice payasam out of it at home (I have some coconut milk from Kerala too ;)). We returned to Zostel in the afternoon. I had muscle pain after the trek and it has still not completely disappeared. At night, we took a bus from Kalpetta to Kozhikode in order to return to Kochi.

Day 6: Return to Kochi At midnight of 2nd of September, we reached Kozhikode bus stand. Then we roamed around for something to eat. I didn t find anything vegetarian to eat. No surprises there! Then we went to Kozhikode railway station and looked for retiring rooms, but no luck there. We waited at the station and took the next train to Kochi at 03:30 and reached Ernakulam Junction at 07:30 (half hours before train s scheduled time!). From there, we went to Zostel Fort Kochi and stayed one night there and checked out next morning.

Day 7: Roaming around in Fort Kochi On 3rd of September, we roamed around in Fort Kochi. We visited the usual places - St Francis Church, Dutch Palace, Jew Town, Pardesi Synagogue. I also visited some homestays and the owners were very happy to show their place even when I made it clear that I was not looking for a stay. In the evening, we went to Kakkanad to attend DebConf. The story continues in my DebConf23 blog post.

I m one of the few folks left who run and maintain mail servers. Recently I had major troubles receiving mails from the mail servers used by a bank, and when asking my favourite search engine, I m clearly not the only one who ran into such an issue. Actually, I should have checked off the issue and not become a customer at that bank, but the tech nerd in me couldn t resist getting to the bottom of the problem. Since I got it working and this might be useful for others, here we are. :) I was trying to get an online banking account set up, but the corresponding account creation mail didn t arrive me, at all. Looking at my mail server logs, my postfix mail server didn t accept the mail due to:

postfix/smtpd[3319640]: warning: TLS library problem: error:1417A0C1:SSL routines:tls_post_process_client_hello:no shared cipher:../ssl/statem/statem_srvr.c:2283:
postfix/smtpd[3319640]: lost connection after STARTTLS from mx01.arz.at[193.110.182.61]

Huh, what s going on here?! Let s increase the TLS loglevel (setting smtpd_tls_loglevel = 2) and retry. But how can I retry receiving yet another mail? Luckily, on the registration website of the bank there was a URL available, that let me request a one-time password. This triggered another mail, so I did that and managed to grab this in the logs:

postfix/smtpd[3320018]: initializing the server-side TLS engine
postfix/tlsmgr[3320020]: open smtpd TLS cache btree:/var/lib/postfix/smtpd_scache
postfix/tlsmgr[3320020]: tlsmgr_cache_run_event: start TLS smtpd session cache cleanup
postfix/smtpd[3320018]: connect from mx01.arz.at[193.110.182.61]
postfix/smtpd[3320018]: setting up TLS connection from mx01.arz.at[193.110.182.61]
postfix/smtpd[3320018]: mx01.arz.at[193.110.182.61]: TLS cipher list "aNULL:-aNULL:HIGH:MEDIUM:+RC4:@STRENGTH"
postfix/smtpd[3320018]: SSL_accept:before SSL initialization
postfix/smtpd[3320018]: SSL_accept:before SSL initialization
postfix/smtpd[3320018]: SSL3 alert write:fatal:handshake failure
postfix/smtpd[3320018]: SSL_accept:error in error
postfix/smtpd[3320018]: SSL_accept error from mx01.arz.at[193.110.182.61]: -1
postfix/smtpd[3320018]: warning: TLS library problem: error:1417A0C1:SSL routines:tls_post_process_client_hello:no shared cipher:../ssl/statem/statem_srvr.c:2283:
postfix/smtpd[3320018]: lost connection after STARTTLS from mx01.arz.at[193.110.182.61]
postfix/smtpd[3320018]: disconnect from mx01.arz.at[193.110.182.61] ehlo=1 starttls=0/1 commands=1/2
postfix/smtpd[3320018]: connect from mx01.arz.at[193.110.182.61]
postfix/smtpd[3320018]: disconnect from mx01.arz.at[193.110.182.61] ehlo=1 quit=1 commands=2

Ok, so this TLS cipher list aNULL:-aNULL:HIGH:MEDIUM:+RC4:@STRENGTH looked like the tls_medium_cipherlist setting in postfix, but which ciphers might we expect? Let s see what their SMTP server would speak to us:

% testssl --cipher-per-proto -t=smtp mx01.arz.at:25
[...]
Hexcode  Cipher Suite Name (OpenSSL)       KeyExch.   Encryption  Bits     Cipher Suite Name (IANA/RFC)
-----------------------------------------------------------------------------------------------------------------------------
SSLv2
SSLv3
TLS 1
TLS 1.1
TLS 1.2
 xc030   ECDHE-RSA-AES256-GCM-SHA384       ECDH 256   AESGCM      256      TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
 xc028   ECDHE-RSA-AES256-SHA384           ECDH 256   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
 xc014   ECDHE-RSA-AES256-SHA              ECDH 256   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
 x9d     AES256-GCM-SHA384                 RSA        AESGCM      256      TLS_RSA_WITH_AES_256_GCM_SHA384
 x3d     AES256-SHA256                     RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA256
 x35     AES256-SHA                        RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA
 xc02f   ECDHE-RSA-AES128-GCM-SHA256       ECDH 256   AESGCM      128      TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
 xc027   ECDHE-RSA-AES128-SHA256           ECDH 256   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
 xc013   ECDHE-RSA-AES128-SHA              ECDH 256   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
 x9c     AES128-GCM-SHA256                 RSA        AESGCM      128      TLS_RSA_WITH_AES_128_GCM_SHA256
 x3c     AES128-SHA256                     RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA256
 x2f     AES128-SHA                        RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA
TLS 1.3

Looks like a very small subset of ciphers, and they don t seem to be talking TLS v1.3 at all? Not great. :( A nice web service to verify the situation from another point of view is checktls, which also confirmed this:

[000.705] 	<-- 	220 2.0.0 Ready to start TLS
[000.705] 		STARTTLS command works on this server
[001.260] 		Connection converted to SSL
		SSLVersion in use: TLSv1_2
		Cipher in use: ECDHE-RSA-AES256-GCM-SHA384
		Perfect Forward Secrecy: yes
		Session Algorithm in use: Curve P-256 DHE(256 bits)
		Certificate #1 of 3 (sent by MX):
		Cert VALIDATED: ok
		Cert Hostname VERIFIED (mx01.arz.at = *.arz.at   DNS:*.arz.at   DNS:arz.at)
[...]
[001.517] 		TLS successfully started on this server

I got distracted by some other work, and when coming back to this problem, the one-time password procedure no longer worked, as the password reset URL was no longer valid. :( I managed to find the underlying URL, and with some web developer tools tinkering I could still use the website to let me trigger sending further one-time password mails, phew. Let s continue, so my mail server was running Debian/bullseye with postfix v3.5.18-0+deb11u1 and openssl v1.1.1n-0+deb11u5, let s see what it offers:

% testssl --cipher-per-proto -t=smtp mail.example.com:25
[...]
Hexcode  Cipher Suite Name (OpenSSL)       KeyExch.   Encryption  Bits     Cipher Suite Name (IANA/RFC)
-----------------------------------------------------------------------------------------------------------------------------
SSLv2
SSLv3
TLS 1
 xc00a   ECDHE-ECDSA-AES256-SHA            ECDH 253   AES         256      TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
 xc019   AECDH-AES256-SHA                  ECDH 253   AES         256      TLS_ECDH_anon_WITH_AES_256_CBC_SHA
 x3a     ADH-AES256-SHA                    DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA
 x89     ADH-CAMELLIA256-SHA               DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA
 xc009   ECDHE-ECDSA-AES128-SHA            ECDH 253   AES         128      TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
 xc018   AECDH-AES128-SHA                  ECDH 253   AES         128      TLS_ECDH_anon_WITH_AES_128_CBC_SHA
 x34     ADH-AES128-SHA                    DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA
 x9b     ADH-SEED-SHA                      DH 2048    SEED        128      TLS_DH_anon_WITH_SEED_CBC_SHA
 x46     ADH-CAMELLIA128-SHA               DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA
TLS 1.1
 xc00a   ECDHE-ECDSA-AES256-SHA            ECDH 253   AES         256      TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
 xc019   AECDH-AES256-SHA                  ECDH 253   AES         256      TLS_ECDH_anon_WITH_AES_256_CBC_SHA
 x3a     ADH-AES256-SHA                    DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA
 x89     ADH-CAMELLIA256-SHA               DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA
 xc009   ECDHE-ECDSA-AES128-SHA            ECDH 253   AES         128      TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
 xc018   AECDH-AES128-SHA                  ECDH 253   AES         128      TLS_ECDH_anon_WITH_AES_128_CBC_SHA
 x34     ADH-AES128-SHA                    DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA
 x9b     ADH-SEED-SHA                      DH 2048    SEED        128      TLS_DH_anon_WITH_SEED_CBC_SHA
 x46     ADH-CAMELLIA128-SHA               DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA
TLS 1.2
 xc02c   ECDHE-ECDSA-AES256-GCM-SHA384     ECDH 253   AESGCM      256      TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
 xc024   ECDHE-ECDSA-AES256-SHA384         ECDH 253   AES         256      TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384
 xc00a   ECDHE-ECDSA-AES256-SHA            ECDH 253   AES         256      TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
 xcca9   ECDHE-ECDSA-CHACHA20-POLY1305     ECDH 253   ChaCha20    256      TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256
 xc0af   ECDHE-ECDSA-AES256-CCM8           ECDH 253   AESCCM8     256      TLS_ECDHE_ECDSA_WITH_AES_256_CCM_8
 xc0ad   ECDHE-ECDSA-AES256-CCM            ECDH 253   AESCCM      256      TLS_ECDHE_ECDSA_WITH_AES_256_CCM
 xc073   ECDHE-ECDSA-CAMELLIA256-SHA384    ECDH 253   Camellia    256      TLS_ECDHE_ECDSA_WITH_CAMELLIA_256_CBC_SHA384
 xc019   AECDH-AES256-SHA                  ECDH 253   AES         256      TLS_ECDH_anon_WITH_AES_256_CBC_SHA
 xa7     ADH-AES256-GCM-SHA384             DH 2048    AESGCM      256      TLS_DH_anon_WITH_AES_256_GCM_SHA384
 x6d     ADH-AES256-SHA256                 DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA256
 x3a     ADH-AES256-SHA                    DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA
 xc5     ADH-CAMELLIA256-SHA256            DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA256
 x89     ADH-CAMELLIA256-SHA               DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA
 xc05d   ECDHE-ECDSA-ARIA256-GCM-SHA384    ECDH 253   ARIAGCM     256      TLS_ECDHE_ECDSA_WITH_ARIA_256_GCM_SHA384
 xc02b   ECDHE-ECDSA-AES128-GCM-SHA256     ECDH 253   AESGCM      128      TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
 xc023   ECDHE-ECDSA-AES128-SHA256         ECDH 253   AES         128      TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256
 xc009   ECDHE-ECDSA-AES128-SHA            ECDH 253   AES         128      TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
 xc0ae   ECDHE-ECDSA-AES128-CCM8           ECDH 253   AESCCM8     128      TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8
 xc0ac   ECDHE-ECDSA-AES128-CCM            ECDH 253   AESCCM      128      TLS_ECDHE_ECDSA_WITH_AES_128_CCM
 xc072   ECDHE-ECDSA-CAMELLIA128-SHA256    ECDH 253   Camellia    128      TLS_ECDHE_ECDSA_WITH_CAMELLIA_128_CBC_SHA256
 xc018   AECDH-AES128-SHA                  ECDH 253   AES         128      TLS_ECDH_anon_WITH_AES_128_CBC_SHA
 xa6     ADH-AES128-GCM-SHA256             DH 2048    AESGCM      128      TLS_DH_anon_WITH_AES_128_GCM_SHA256
 x6c     ADH-AES128-SHA256                 DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA256
 x34     ADH-AES128-SHA                    DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA
 xbf     ADH-CAMELLIA128-SHA256            DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA256
 x9b     ADH-SEED-SHA                      DH 2048    SEED        128      TLS_DH_anon_WITH_SEED_CBC_SHA
 x46     ADH-CAMELLIA128-SHA               DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA
 xc05c   ECDHE-ECDSA-ARIA128-GCM-SHA256    ECDH 253   ARIAGCM     128      TLS_ECDHE_ECDSA_WITH_ARIA_128_GCM_SHA256
TLS 1.3
 x1302   TLS_AES_256_GCM_SHA384            ECDH 253   AESGCM      256      TLS_AES_256_GCM_SHA384
 x1303   TLS_CHACHA20_POLY1305_SHA256      ECDH 253   ChaCha20    256      TLS_CHACHA20_POLY1305_SHA256
 x1301   TLS_AES_128_GCM_SHA256            ECDH 253   AESGCM      128      TLS_AES_128_GCM_SHA256

Not so bad, but sadly no overlap with any of the ciphers that mx01.arz.at offers. What about disabling STARTTLS for the mx01.arz.at (+ mx02.arz.at being another one used by the relevant domain) mail servers when talking to mine? Let s try that:

% sudo postconf -nf smtpd_discard_ehlo_keyword_address_maps
smtpd_discard_ehlo_keyword_address_maps =
    hash:/etc/postfix/smtpd_discard_ehlo_keywords
% cat /etc/postfix/smtpd_discard_ehlo_keywords
# *disable* starttls for mx01.arz.at / mx02.arz.at:
193.110.182.61 starttls
193.110.182.62 starttls

But the remote mail server doesn t seem to send mails without TLS:

postfix/smtpd[4151799]: connect from mx01.arz.at[193.110.182.61]
postfix/smtpd[4151799]: discarding EHLO keywords: STARTTLS
postfix/smtpd[4151799]: disconnect from mx01.arz.at[193.110.182.61] ehlo=1 quit=1 commands=2

Let s verify this further, but without fiddling with the main mail server too much. We can add a dedicated service to postfix (see serverfault), and run it in verbose mode, to get more detailled logging:

% sudo postconf -Mf
[...]
10025      inet  n       -       -       -       -       smtpd
    -o syslog_name=postfix/smtpd/badstarttls
    -o smtpd_tls_security_level=none
    -o smtpd_helo_required=yes
    -o smtpd_helo_restrictions=pcre:/etc/postfix/helo_badstarttls_allow,reject
    -v
[...]
% cat /etc/postfix/helo_badstarttls_allow
/mx01.arz.at/ OK
/mx02.arz.at/ OK
/193.110.182.61/ OK
/193.110.182.62/ OK

We redirect the traffic from mx01.arz.at + mx02.arz.at towards our new postfix service, listening on port 10025:

% sudo iptables -t nat -A PREROUTING -p tcp -s 193.110.182.61 --dport 25 -j REDIRECT --to-port 10025
% sudo iptables -t nat -A PREROUTING -p tcp -s 193.110.182.62 --dport 25 -j REDIRECT --to-port 10025

With this setup we get very detailed logging, and it seems to confirm our suspicion that the mail server doesn t want to talk unencrypted with us:

[...]
postfix/smtpd/badstarttls/smtpd[3491900]: connect from mx01.arz.at[193.110.182.61]
[...]
postfix/smtpd/badstarttls/smtpd[3491901]: disconnect from mx01.arz.at[193.110.182.61] ehlo=1 quit=1 commands=2
postfix/smtpd/badstarttls/smtpd[3491901]: master_notify: status 1
postfix/smtpd/badstarttls/smtpd[3491901]: connection closed
[...]

Let s step back and revert those changes, back to our original postfix setup. Might the problem be related to our Let s Encrypt certificate? Let s see what we have:

% echo QUIT   openssl s_client -connect mail.example.com:25 -starttls
[...]
issuer=C = US, O = Let's Encrypt, CN = R3
---
No client certificate CA names sent
Peer signing digest: SHA384
Peer signature type: ECDSA
Server Temp Key: X25519, 253 bits
---
SSL handshake has read 4455 bytes and written 427 bytes
Verification: OK
---
New, TLSv1.3, Cipher is TLS_AES_256_GCM_SHA384
Server public key is 384 bit
[...]

We have an ECDSA based certificate, what about switching to RSA instead? Thanks to the wonderful dehydrated, this is as easy as:

% echo KEY_ALGO=rsa > certs/mail.example.com/config
% ./dehydrated -c --domain mail.example.com --force
% sudo systemctl reload postfix

With switching to RSA type key we get:

% echo QUIT   openssl s_client -connect mail.example.com:25 -starttls smtp
CONNECTED(00000003)
[...]
issuer=C = US, O = Let's Encrypt, CN = R3
---
No client certificate CA names sent
Peer signing digest: SHA256
Peer signature type: RSA-PSS
Server Temp Key: X25519, 253 bits
---
SSL handshake has read 5295 bytes and written 427 bytes
Verification: OK
---
New, TLSv1.3, Cipher is TLS_AES_256_GCM_SHA384
Server public key is 4096 bit

Which ciphers do we offer now? Let s check:

% testssl --cipher-per-proto -t=smtp mail.example.com:25
[...]
Hexcode  Cipher Suite Name (OpenSSL)       KeyExch.   Encryption  Bits     Cipher Suite Name (IANA/RFC)
-----------------------------------------------------------------------------------------------------------------------------
SSLv2
SSLv3
TLS 1
 xc014   ECDHE-RSA-AES256-SHA              ECDH 253   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
 x39     DHE-RSA-AES256-SHA                DH 2048    AES         256      TLS_DHE_RSA_WITH_AES_256_CBC_SHA
 x88     DHE-RSA-CAMELLIA256-SHA           DH 2048    Camellia    256      TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA
 xc019   AECDH-AES256-SHA                  ECDH 253   AES         256      TLS_ECDH_anon_WITH_AES_256_CBC_SHA
 x3a     ADH-AES256-SHA                    DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA
 x89     ADH-CAMELLIA256-SHA               DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA
 x35     AES256-SHA                        RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA
 x84     CAMELLIA256-SHA                   RSA        Camellia    256      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA
 xc013   ECDHE-RSA-AES128-SHA              ECDH 253   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
 x33     DHE-RSA-AES128-SHA                DH 2048    AES         128      TLS_DHE_RSA_WITH_AES_128_CBC_SHA
 x9a     DHE-RSA-SEED-SHA                  DH 2048    SEED        128      TLS_DHE_RSA_WITH_SEED_CBC_SHA
 x45     DHE-RSA-CAMELLIA128-SHA           DH 2048    Camellia    128      TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA
 xc018   AECDH-AES128-SHA                  ECDH 253   AES         128      TLS_ECDH_anon_WITH_AES_128_CBC_SHA
 x34     ADH-AES128-SHA                    DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA
 x9b     ADH-SEED-SHA                      DH 2048    SEED        128      TLS_DH_anon_WITH_SEED_CBC_SHA
 x46     ADH-CAMELLIA128-SHA               DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA
 x2f     AES128-SHA                        RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA
 x96     SEED-SHA                          RSA        SEED        128      TLS_RSA_WITH_SEED_CBC_SHA
 x41     CAMELLIA128-SHA                   RSA        Camellia    128      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA
TLS 1.1
 xc014   ECDHE-RSA-AES256-SHA              ECDH 253   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
 x39     DHE-RSA-AES256-SHA                DH 2048    AES         256      TLS_DHE_RSA_WITH_AES_256_CBC_SHA
 x88     DHE-RSA-CAMELLIA256-SHA           DH 2048    Camellia    256      TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA
 xc019   AECDH-AES256-SHA                  ECDH 253   AES         256      TLS_ECDH_anon_WITH_AES_256_CBC_SHA
 x3a     ADH-AES256-SHA                    DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA
 x89     ADH-CAMELLIA256-SHA               DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA
 x35     AES256-SHA                        RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA
 x84     CAMELLIA256-SHA                   RSA        Camellia    256      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA
 xc013   ECDHE-RSA-AES128-SHA              ECDH 253   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
 x33     DHE-RSA-AES128-SHA                DH 2048    AES         128      TLS_DHE_RSA_WITH_AES_128_CBC_SHA
 x9a     DHE-RSA-SEED-SHA                  DH 2048    SEED        128      TLS_DHE_RSA_WITH_SEED_CBC_SHA
 x45     DHE-RSA-CAMELLIA128-SHA           DH 2048    Camellia    128      TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA
 xc018   AECDH-AES128-SHA                  ECDH 253   AES         128      TLS_ECDH_anon_WITH_AES_128_CBC_SHA
 x34     ADH-AES128-SHA                    DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA
 x9b     ADH-SEED-SHA                      DH 2048    SEED        128      TLS_DH_anon_WITH_SEED_CBC_SHA
 x46     ADH-CAMELLIA128-SHA               DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA
 x2f     AES128-SHA                        RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA
 x96     SEED-SHA                          RSA        SEED        128      TLS_RSA_WITH_SEED_CBC_SHA
 x41     CAMELLIA128-SHA                   RSA        Camellia    128      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA
TLS 1.2
 xc030   ECDHE-RSA-AES256-GCM-SHA384       ECDH 253   AESGCM      256      TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
 xc028   ECDHE-RSA-AES256-SHA384           ECDH 253   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
 xc014   ECDHE-RSA-AES256-SHA              ECDH 253   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
 x9f     DHE-RSA-AES256-GCM-SHA384         DH 2048    AESGCM      256      TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
 xcca8   ECDHE-RSA-CHACHA20-POLY1305       ECDH 253   ChaCha20    256      TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
 xccaa   DHE-RSA-CHACHA20-POLY1305         DH 2048    ChaCha20    256      TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256
 xc0a3   DHE-RSA-AES256-CCM8               DH 2048    AESCCM8     256      TLS_DHE_RSA_WITH_AES_256_CCM_8
 xc09f   DHE-RSA-AES256-CCM                DH 2048    AESCCM      256      TLS_DHE_RSA_WITH_AES_256_CCM
 x6b     DHE-RSA-AES256-SHA256             DH 2048    AES         256      TLS_DHE_RSA_WITH_AES_256_CBC_SHA256
 x39     DHE-RSA-AES256-SHA                DH 2048    AES         256      TLS_DHE_RSA_WITH_AES_256_CBC_SHA
 xc077   ECDHE-RSA-CAMELLIA256-SHA384      ECDH 253   Camellia    256      TLS_ECDHE_RSA_WITH_CAMELLIA_256_CBC_SHA384
 xc4     DHE-RSA-CAMELLIA256-SHA256        DH 2048    Camellia    256      TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA256
 x88     DHE-RSA-CAMELLIA256-SHA           DH 2048    Camellia    256      TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA
 xc019   AECDH-AES256-SHA                  ECDH 253   AES         256      TLS_ECDH_anon_WITH_AES_256_CBC_SHA
 xa7     ADH-AES256-GCM-SHA384             DH 2048    AESGCM      256      TLS_DH_anon_WITH_AES_256_GCM_SHA384
 x6d     ADH-AES256-SHA256                 DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA256
 x3a     ADH-AES256-SHA                    DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA
 xc5     ADH-CAMELLIA256-SHA256            DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA256
 x89     ADH-CAMELLIA256-SHA               DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA
 x9d     AES256-GCM-SHA384                 RSA        AESGCM      256      TLS_RSA_WITH_AES_256_GCM_SHA384
 xc0a1   AES256-CCM8                       RSA        AESCCM8     256      TLS_RSA_WITH_AES_256_CCM_8
 xc09d   AES256-CCM                        RSA        AESCCM      256      TLS_RSA_WITH_AES_256_CCM
 x3d     AES256-SHA256                     RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA256
 x35     AES256-SHA                        RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA
 xc0     CAMELLIA256-SHA256                RSA        Camellia    256      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA256
 x84     CAMELLIA256-SHA                   RSA        Camellia    256      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA
 xc051   ARIA256-GCM-SHA384                RSA        ARIAGCM     256      TLS_RSA_WITH_ARIA_256_GCM_SHA384
 xc053   DHE-RSA-ARIA256-GCM-SHA384        DH 2048    ARIAGCM     256      TLS_DHE_RSA_WITH_ARIA_256_GCM_SHA384
 xc061   ECDHE-ARIA256-GCM-SHA384          ECDH 253   ARIAGCM     256      TLS_ECDHE_RSA_WITH_ARIA_256_GCM_SHA384
 xc02f   ECDHE-RSA-AES128-GCM-SHA256       ECDH 253   AESGCM      128      TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
 xc027   ECDHE-RSA-AES128-SHA256           ECDH 253   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
 xc013   ECDHE-RSA-AES128-SHA              ECDH 253   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
 x9e     DHE-RSA-AES128-GCM-SHA256         DH 2048    AESGCM      128      TLS_DHE_RSA_WITH_AES_128_GCM_SHA256
 xc0a2   DHE-RSA-AES128-CCM8               DH 2048    AESCCM8     128      TLS_DHE_RSA_WITH_AES_128_CCM_8
 xc09e   DHE-RSA-AES128-CCM                DH 2048    AESCCM      128      TLS_DHE_RSA_WITH_AES_128_CCM
 xc0a0   AES128-CCM8                       RSA        AESCCM8     128      TLS_RSA_WITH_AES_128_CCM_8
 xc09c   AES128-CCM                        RSA        AESCCM      128      TLS_RSA_WITH_AES_128_CCM
 x67     DHE-RSA-AES128-SHA256             DH 2048    AES         128      TLS_DHE_RSA_WITH_AES_128_CBC_SHA256
 x33     DHE-RSA-AES128-SHA                DH 2048    AES         128      TLS_DHE_RSA_WITH_AES_128_CBC_SHA
 xc076   ECDHE-RSA-CAMELLIA128-SHA256      ECDH 253   Camellia    128      TLS_ECDHE_RSA_WITH_CAMELLIA_128_CBC_SHA256
 xbe     DHE-RSA-CAMELLIA128-SHA256        DH 2048    Camellia    128      TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA256
 x9a     DHE-RSA-SEED-SHA                  DH 2048    SEED        128      TLS_DHE_RSA_WITH_SEED_CBC_SHA
 x45     DHE-RSA-CAMELLIA128-SHA           DH 2048    Camellia    128      TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA
 xc018   AECDH-AES128-SHA                  ECDH 253   AES         128      TLS_ECDH_anon_WITH_AES_128_CBC_SHA
 xa6     ADH-AES128-GCM-SHA256             DH 2048    AESGCM      128      TLS_DH_anon_WITH_AES_128_GCM_SHA256
 x6c     ADH-AES128-SHA256                 DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA256
 x34     ADH-AES128-SHA                    DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA
 xbf     ADH-CAMELLIA128-SHA256            DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA256
 x9b     ADH-SEED-SHA                      DH 2048    SEED        128      TLS_DH_anon_WITH_SEED_CBC_SHA
 x46     ADH-CAMELLIA128-SHA               DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA
 x9c     AES128-GCM-SHA256                 RSA        AESGCM      128      TLS_RSA_WITH_AES_128_GCM_SHA256
 x3c     AES128-SHA256                     RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA256
 x2f     AES128-SHA                        RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA
 xba     CAMELLIA128-SHA256                RSA        Camellia    128      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA256
 x96     SEED-SHA                          RSA        SEED        128      TLS_RSA_WITH_SEED_CBC_SHA
 x41     CAMELLIA128-SHA                   RSA        Camellia    128      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA
 xc050   ARIA128-GCM-SHA256                RSA        ARIAGCM     128      TLS_RSA_WITH_ARIA_128_GCM_SHA256
 xc052   DHE-RSA-ARIA128-GCM-SHA256        DH 2048    ARIAGCM     128      TLS_DHE_RSA_WITH_ARIA_128_GCM_SHA256
 xc060   ECDHE-ARIA128-GCM-SHA256          ECDH 253   ARIAGCM     128      TLS_ECDHE_RSA_WITH_ARIA_128_GCM_SHA256
TLS 1.3
 x1302   TLS_AES_256_GCM_SHA384            ECDH 253   AESGCM      256      TLS_AES_256_GCM_SHA384
 x1303   TLS_CHACHA20_POLY1305_SHA256      ECDH 253   ChaCha20    256      TLS_CHACHA20_POLY1305_SHA256
 x1301   TLS_AES_128_GCM_SHA256            ECDH 253   AESGCM      128      TLS_AES_128_GCM_SHA256

With switching our SSL certificate to RSA, we gained around 51 new cipher options, amongst them being ones that also mx01.arz.at claimed to support. FTR, the result from above is what you get with the default settings for postfix v3.5.18, being:

smtpd_tls_ciphers = medium
smtpd_tls_mandatory_ciphers = medium
smtpd_tls_mandatory_exclude_ciphers =
smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3

But the delay between triggering the password reset mail and getting a mail server connect was getting bigger and bigger. Therefore while waiting for the next mail to arrive, I decided to capture the network traffic, to be able to look further into this if it should continue to be failing:

% sudo tshark -n -i eth0 -s 65535 -w arz.pcap -f "host 193.110.182.61 or host 193.110.182.62"

A few hours later the mail server connected again, and the mail went through!

postfix/smtpd[4162835]: connect from mx01.arz.at[193.110.182.61]
postfix/smtpd[4162835]: Anonymous TLS connection established from mx01.arz.at[193.110.182.61]: TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)
postfix/smtpd[4162835]: E50D6401E6: client=mx01.arz.at[193.110.182.61]
postfix/smtpd[4162835]: disconnect from mx01.arz.at[193.110.182.61] ehlo=2 starttls=1 mail=1 rcpt=1 data=1 quit=1 commands=7

Now also having the captured network traffic, we can check the details there:

[...]
% tshark -o smtp.decryption:true -r arz.pcap
    1 0.000000000 193.110.182.61   203.0.113.42 TCP 74 24699   25 [SYN] Seq=0 Win=29200 Len=0 MSS=1460 SACK_PERM=1 TSval=2261106119 TSecr=0 WS=128
    2 0.000042827 203.0.113.42   193.110.182.61 TCP 74 25   24699 [SYN, ACK] Seq=0 Ack=1 Win=65160 Len=0 MSS=1460 SACK_PERM=1 TSval=3233422181 TSecr=2261106119 WS=128
    3 0.020719269 193.110.182.61   203.0.113.42 TCP 66 24699   25 [ACK] Seq=1 Ack=1 Win=29312 Len=0 TSval=2261106139 TSecr=3233422181
    4 0.022883259 203.0.113.42   193.110.182.61 SMTP 96 S: 220 mail.example.com ESMTP
    5 0.043682626 193.110.182.61   203.0.113.42 TCP 66 24699   25 [ACK] Seq=1 Ack=31 Win=29312 Len=0 TSval=2261106162 TSecr=3233422203
    6 0.043799047 193.110.182.61   203.0.113.42 SMTP 84 C: EHLO mx01.arz.at
    7 0.043811363 203.0.113.42   193.110.182.61 TCP 66 25   24699 [ACK] Seq=31 Ack=19 Win=65280 Len=0 TSval=3233422224 TSecr=2261106162
    8 0.043898412 203.0.113.42   193.110.182.61 SMTP 253 S: 250-mail.example.com   PIPELINING   SIZE 20240000   VRFY   ETRN   AUTH PLAIN   AUTH=PLAIN   ENHANCEDSTATUSCODES   8BITMIME   DSN   SMTPUTF8   CHUNKING
    9 0.064625499 193.110.182.61   203.0.113.42 SMTP 72 C: QUIT
   10 0.064750257 203.0.113.42   193.110.182.61 SMTP 81 S: 221 2.0.0 Bye
   11 0.064760200 203.0.113.42   193.110.182.61 TCP 66 25   24699 [FIN, ACK] Seq=233 Ack=25 Win=65280 Len=0 TSval=3233422245 TSecr=2261106183
   12 0.085573715 193.110.182.61   203.0.113.42 TCP 66 24699   25 [FIN, ACK] Seq=25 Ack=234 Win=30336 Len=0 TSval=2261106204 TSecr=3233422245
   13 0.085610229 203.0.113.42   193.110.182.61 TCP 66 25   24699 [ACK] Seq=234 Ack=26 Win=65280 Len=0 TSval=3233422266 TSecr=2261106204
   14 1799.888108373 193.110.182.61   203.0.113.42 TCP 74 10330   25 [SYN] Seq=0 Win=29200 Len=0 MSS=1460 SACK_PERM=1 TSval=2262906007 TSecr=0 WS=128
   15 1799.888161311 203.0.113.42   193.110.182.61 TCP 74 25   10330 [SYN, ACK] Seq=0 Ack=1 Win=65160 Len=0 MSS=1460 SACK_PERM=1 TSval=3235222069 TSecr=2262906007 WS=128
   16 1799.909030335 193.110.182.61   203.0.113.42 TCP 66 10330   25 [ACK] Seq=1 Ack=1 Win=29312 Len=0 TSval=2262906028 TSecr=3235222069
   17 1799.956621011 203.0.113.42   193.110.182.61 SMTP 96 S: 220 mail.example.com ESMTP
   18 1799.977229656 193.110.182.61   203.0.113.42 TCP 66 10330   25 [ACK] Seq=1 Ack=31 Win=29312 Len=0 TSval=2262906096 TSecr=3235222137
   19 1799.977229698 193.110.182.61   203.0.113.42 SMTP 84 C: EHLO mx01.arz.at
   20 1799.977266759 203.0.113.42   193.110.182.61 TCP 66 25   10330 [ACK] Seq=31 Ack=19 Win=65280 Len=0 TSval=3235222158 TSecr=2262906096
   21 1799.977351663 203.0.113.42   193.110.182.61 SMTP 267 S: 250-mail.example.com   PIPELINING   SIZE 20240000   VRFY   ETRN   STARTTLS   AUTH PLAIN   AUTH=PLAIN   ENHANCEDSTATUSCODES   8BITMIME   DSN   SMTPUTF8   CHUNKING
   22 1800.011494861 193.110.182.61   203.0.113.42 SMTP 76 C: STARTTLS
   23 1800.011589267 203.0.113.42   193.110.182.61 SMTP 96 S: 220 2.0.0 Ready to start TLS
   24 1800.032812294 193.110.182.61   203.0.113.42 TLSv1 223 Client Hello
   25 1800.032987264 203.0.113.42   193.110.182.61 TLSv1.2 2962 Server Hello
   26 1800.032995513 203.0.113.42   193.110.182.61 TCP 1266 25   10330 [PSH, ACK] Seq=3158 Ack=186 Win=65152 Len=1200 TSval=3235222214 TSecr=2262906151 [TCP segment of a reassembled PDU]
   27 1800.053546755 193.110.182.61   203.0.113.42 TCP 66 10330   25 [ACK] Seq=186 Ack=3158 Win=36096 Len=0 TSval=2262906172 TSecr=3235222214
   28 1800.092852469 193.110.182.61   203.0.113.42 TCP 66 10330   25 [ACK] Seq=186 Ack=4358 Win=39040 Len=0 TSval=2262906212 TSecr=3235222214
   29 1800.092892905 203.0.113.42   193.110.182.61 TLSv1.2 900 Certificate, Server Key Exchange, Server Hello Done
   30 1800.113546769 193.110.182.61   203.0.113.42 TCP 66 10330   25 [ACK] Seq=186 Ack=5192 Win=41856 Len=0 TSval=2262906232 TSecr=3235222273
   31 1800.114763363 193.110.182.61   203.0.113.42 TLSv1.2 192 Client Key Exchange, Change Cipher Spec, Encrypted Handshake Message
   32 1800.115000416 203.0.113.42   193.110.182.61 TLSv1.2 117 Change Cipher Spec, Encrypted Handshake Message
   33 1800.136070200 193.110.182.61   203.0.113.42 TLSv1.2 113 Application Data
   34 1800.136155526 203.0.113.42   193.110.182.61 TLSv1.2 282 Application Data
   35 1800.158854473 193.110.182.61   203.0.113.42 TLSv1.2 162 Application Data
   36 1800.159254794 203.0.113.42   193.110.182.61 TLSv1.2 109 Application Data
   37 1800.180286407 193.110.182.61   203.0.113.42 TLSv1.2 144 Application Data
   38 1800.223005960 203.0.113.42   193.110.182.61 TCP 66 25   10330 [ACK] Seq=5502 Ack=533 Win=65152 Len=0 TSval=3235222404 TSecr=2262906299
   39 1802.230300244 203.0.113.42   193.110.182.61 TLSv1.2 146 Application Data
   40 1802.251994333 193.110.182.61   203.0.113.42 TCP 2962 [TCP segment of a reassembled PDU]
   41 1802.252034015 203.0.113.42   193.110.182.61 TCP 66 25   10330 [ACK] Seq=5582 Ack=3429 Win=63616 Len=0 TSval=3235224433 TSecr=2262908371
   42 1802.252279083 193.110.182.61   203.0.113.42 TLSv1.2 1295 Application Data
   43 1802.252288316 203.0.113.42   193.110.182.61 TCP 66 25   10330 [ACK] Seq=5582 Ack=4658 Win=64128 Len=0 TSval=3235224433 TSecr=2262908371
   44 1802.272816060 193.110.182.61   203.0.113.42 TLSv1.2 833 Application Data, Application Data
   45 1802.272827542 203.0.113.42   193.110.182.61 TCP 66 25   10330 [ACK] Seq=5582 Ack=5425 Win=64128 Len=0 TSval=3235224453 TSecr=2262908392
   46 1802.338807683 203.0.113.42   193.110.182.61 TLSv1.2 131 Application Data
   47 1802.398968611 193.110.182.61   203.0.113.42 TCP 66 10330   25 [ACK] Seq=5425 Ack=5647 Win=44800 Len=0 TSval=2262908518 TSecr=3235224519
   48 1863.257457500 193.110.182.61   203.0.113.42 TLSv1.2 101 Application Data
   49 1863.257495688 203.0.113.42   193.110.182.61 TCP 66 25   10330 [ACK] Seq=5647 Ack=5460 Win=64128 Len=0 TSval=3235285438 TSecr=2262969376
   50 1863.257654942 203.0.113.42   193.110.182.61 TLSv1.2 110 Application Data
   51 1863.257721010 203.0.113.42   193.110.182.61 TLSv1.2 97 Encrypted Alert
   52 1863.278242216 193.110.182.61   203.0.113.42 TCP 66 10330   25 [ACK] Seq=5460 Ack=5691 Win=44800 Len=0 TSval=2262969397 TSecr=3235285438
   53 1863.278464176 193.110.182.61   203.0.113.42 TCP 66 10330   25 [RST, ACK] Seq=5460 Ack=5723 Win=44800 Len=0 TSval=2262969397 TSecr=3235285438

% tshark -O tls -r arz.pcap
[...]
Transport Layer Security
    TLSv1 Record Layer: Handshake Protocol: Client Hello
        Content Type: Handshake (22)
        Version: TLS 1.0 (0x0301)
        Length: 152
        Handshake Protocol: Client Hello
            Handshake Type: Client Hello (1)
            Length: 148
            Version: TLS 1.2 (0x0303)
            Random: 4575d1e7c93c09a564edc00b8b56ea6f5d826f8cfe78eb980c451a70a9c5123f
                GMT Unix Time: Dec  5, 2006 21:09:11.000000000 CET
                Random Bytes: c93c09a564edc00b8b56ea6f5d826f8cfe78eb980c451a70a9c5123f
            Session ID Length: 0
            Cipher Suites Length: 26
            Cipher Suites (13 suites)
                Cipher Suite: TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (0xc030)
                Cipher Suite: TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (0xc02f)
                Cipher Suite: TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 (0xc028)
                Cipher Suite: TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 (0xc027)
                Cipher Suite: TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (0xc014)
                Cipher Suite: TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (0xc013)
                Cipher Suite: TLS_RSA_WITH_AES_256_GCM_SHA384 (0x009d)
                Cipher Suite: TLS_RSA_WITH_AES_128_GCM_SHA256 (0x009c)
                Cipher Suite: TLS_RSA_WITH_AES_256_CBC_SHA256 (0x003d)
                Cipher Suite: TLS_RSA_WITH_AES_128_CBC_SHA256 (0x003c)
                Cipher Suite: TLS_RSA_WITH_AES_256_CBC_SHA (0x0035)
                Cipher Suite: TLS_RSA_WITH_AES_128_CBC_SHA (0x002f)
                Cipher Suite: TLS_EMPTY_RENEGOTIATION_INFO_SCSV (0x00ff)
[...]
Transport Layer Security
    TLSv1.2 Record Layer: Handshake Protocol: Server Hello
        Content Type: Handshake (22)
        Version: TLS 1.2 (0x0303)
        Length: 89
        Handshake Protocol: Server Hello
            Handshake Type: Server Hello (2)
            Length: 85
            Version: TLS 1.2 (0x0303)
            Random: cf2ed24e3300e95e5f56023bf8b4e5904b862bb2ed8a5796444f574e47524401
                GMT Unix Time: Feb 23, 2080 23:16:46.000000000 CET
                Random Bytes: 3300e95e5f56023bf8b4e5904b862bb2ed8a5796444f574e47524401
            Session ID Length: 32
            Session ID: 63d041b126ecebf857d685abd9d4593c46a3672e1ad76228f3eacf2164f86fb9
            Cipher Suite: TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (0xc030)
[...]

In this network dump we see what cipher suites are offered, and the TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 here is the Cipher Suite Name in IANA/RFC speak. Whis corresponds to the ECDHE-RSA-AES256-GCM-SHA384 in openssl speak (see Mozilla s Mozilla s cipher suite correspondence table), which we also saw in the postfix log. Mission accomplished! :) Now, if we re interested in avoiding certain ciphers and increase security level, we can e.g. get rid of the SEED, CAMELLIA and all anonymous ciphers, and could accept only TLS v1.2 + v1.3, by further adjusting postfix s main.cf:

smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = aNULL CAMELLIA
smtpd_tls_mandatory_ciphers = high
smtpd_tls_mandatory_protocols = TLSv1.2 TLSv1.3
smtpd_tls_protocols = TLSv1.2 TLSv1.3

Which would then gives us:

% testssl --cipher-per-proto -t=smtp mail.example.com:25
[...]
Hexcode  Cipher Suite Name (OpenSSL)       KeyExch.   Encryption  Bits     Cipher Suite Name (IANA/RFC)
-----------------------------------------------------------------------------------------------------------------------------
SSLv2
SSLv3
TLS 1
TLS 1.1
TLS 1.2
 xc030   ECDHE-RSA-AES256-GCM-SHA384       ECDH 253   AESGCM      256      TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
 xc028   ECDHE-RSA-AES256-SHA384           ECDH 253   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
 xc014   ECDHE-RSA-AES256-SHA              ECDH 253   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
 x9f     DHE-RSA-AES256-GCM-SHA384         DH 2048    AESGCM      256      TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
 xcca8   ECDHE-RSA-CHACHA20-POLY1305       ECDH 253   ChaCha20    256      TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
 xccaa   DHE-RSA-CHACHA20-POLY1305         DH 2048    ChaCha20    256      TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256
 xc0a3   DHE-RSA-AES256-CCM8               DH 2048    AESCCM8     256      TLS_DHE_RSA_WITH_AES_256_CCM_8
 xc09f   DHE-RSA-AES256-CCM                DH 2048    AESCCM      256      TLS_DHE_RSA_WITH_AES_256_CCM
 x6b     DHE-RSA-AES256-SHA256             DH 2048    AES         256      TLS_DHE_RSA_WITH_AES_256_CBC_SHA256
 x39     DHE-RSA-AES256-SHA                DH 2048    AES         256      TLS_DHE_RSA_WITH_AES_256_CBC_SHA
 x9d     AES256-GCM-SHA384                 RSA        AESGCM      256      TLS_RSA_WITH_AES_256_GCM_SHA384
 xc0a1   AES256-CCM8                       RSA        AESCCM8     256      TLS_RSA_WITH_AES_256_CCM_8
 xc09d   AES256-CCM                        RSA        AESCCM      256      TLS_RSA_WITH_AES_256_CCM
 x3d     AES256-SHA256                     RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA256
 x35     AES256-SHA                        RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA
 xc051   ARIA256-GCM-SHA384                RSA        ARIAGCM     256      TLS_RSA_WITH_ARIA_256_GCM_SHA384
 xc053   DHE-RSA-ARIA256-GCM-SHA384        DH 2048    ARIAGCM     256      TLS_DHE_RSA_WITH_ARIA_256_GCM_SHA384
 xc061   ECDHE-ARIA256-GCM-SHA384          ECDH 253   ARIAGCM     256      TLS_ECDHE_RSA_WITH_ARIA_256_GCM_SHA384
 xc02f   ECDHE-RSA-AES128-GCM-SHA256       ECDH 253   AESGCM      128      TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
 xc027   ECDHE-RSA-AES128-SHA256           ECDH 253   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
 xc013   ECDHE-RSA-AES128-SHA              ECDH 253   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
 x9e     DHE-RSA-AES128-GCM-SHA256         DH 2048    AESGCM      128      TLS_DHE_RSA_WITH_AES_128_GCM_SHA256
 xc0a2   DHE-RSA-AES128-CCM8               DH 2048    AESCCM8     128      TLS_DHE_RSA_WITH_AES_128_CCM_8
 xc09e   DHE-RSA-AES128-CCM                DH 2048    AESCCM      128      TLS_DHE_RSA_WITH_AES_128_CCM
 xc0a0   AES128-CCM8                       RSA        AESCCM8     128      TLS_RSA_WITH_AES_128_CCM_8
 xc09c   AES128-CCM                        RSA        AESCCM      128      TLS_RSA_WITH_AES_128_CCM
 x67     DHE-RSA-AES128-SHA256             DH 2048    AES         128      TLS_DHE_RSA_WITH_AES_128_CBC_SHA256
 x33     DHE-RSA-AES128-SHA                DH 2048    AES         128      TLS_DHE_RSA_WITH_AES_128_CBC_SHA
 x9c     AES128-GCM-SHA256                 RSA        AESGCM      128      TLS_RSA_WITH_AES_128_GCM_SHA256
 x3c     AES128-SHA256                     RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA256
 x2f     AES128-SHA                        RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA
 xc050   ARIA128-GCM-SHA256                RSA        ARIAGCM     128      TLS_RSA_WITH_ARIA_128_GCM_SHA256
 xc052   DHE-RSA-ARIA128-GCM-SHA256        DH 2048    ARIAGCM     128      TLS_DHE_RSA_WITH_ARIA_128_GCM_SHA256
 xc060   ECDHE-ARIA128-GCM-SHA256          ECDH 253   ARIAGCM     128      TLS_ECDHE_RSA_WITH_ARIA_128_GCM_SHA256
TLS 1.3
 x1302   TLS_AES_256_GCM_SHA384            ECDH 253   AESGCM      256      TLS_AES_256_GCM_SHA384
 x1303   TLS_CHACHA20_POLY1305_SHA256      ECDH 253   ChaCha20    256      TLS_CHACHA20_POLY1305_SHA256
 x1301   TLS_AES_128_GCM_SHA256            ECDH 253   AESGCM      128      TLS_AES_128_GCM_SHA256

Don t forget to also adjust the smpt_tls_* accordingly (for your sending side). For further information see the Postfix TLS Support documentation. Also check out options like tls_ssl_options (setting it to e.g. NO_COMPRESSION) and tls_preempt_cipherlist (setting it to yes would prefer the servers order of ciphers over clients). Conclusions:

no matter what you change in your mail server settings, be aware that the type of your SSL certificate also matters for what ciphers are offered and used
there are mail servers out there that don t support SSL certificates with ECDSA, using RSA for those ensure better compatibility (nowadays postfix supports parallel usage of ECDSA and RSA keys BTW, check out the smtpd_tls_eccert_file + smtpd_tls_eckey_file options)
testssl is a very useful tool, especially with its cipher-per-proto -t=smtp option to check SMTP servers
if you re uncertain what s going on, consider capturing network data (tshark/tcpdump/ are your friends)
review your postfix configuration and logs every now and then :)

After cycling the Northcape 4000 (from Italy to northern Norway) last year, I signed up for the transcontinental race this year. The Transcontinental is bikepacking race across Europe, self-routed (but with some mandatory checkpoints), unsupported and with a distance of usually somewhere around 4000 km. The cut-off time is 15 days, with the winner usually taking 7-10 days. This year, the route went from Belgium to Thessaloniki in Greece, with control points in northern Italy, Slovenia, Albania and Meteora (Greece). The event was great - it was well organised and communication was a lot better than at the Northcape. It did feel very different from the Northcape, though, being a proper race. Participants are not allowed to draft off each other or help each other, though a quick chat here or there as you pass people is possible, or when you re both stopped at a shop or control point.

My experience The route was beautiful - the first bit through France was a bit monotonic, but especially the views in the alps were amazing. Like with other long events, the first day or two can be hard but once you get into the rhythm of things it s a lot easier. From early on, I lost a lot of time. We started in the rain, and I ran several flats in a row, just 4 hours in. In addition to that, the thread on my pump had worn so it wouldn t fit on some of my spare tubes, and my tubes were all TPU - which are hard to patch. So at 3 AM I found myself by the side of an N-road in France without any usable tubes to put in my rear wheel. I ended up walking 20km to the nearest town with a bike shop, where they fortunately had good old butyl tubes and a working pump. But overall, this cost me about 12 hours in total. In addition to that, my time management wasn t great. On previous rides, I d usually gotten about 8 hours of sleep per night while staying in hotels. On the transcontinental I had meant to get less sleep but still stay in hotels most night, but I found that not all hotels accomodated well for that - especially with a bike. So I ended up getting more sleep than I had intended, and spending more time off the bike than I had planned - close to 11 or 12 hours per day. I hadn t scheduled much time off work after the finish either, so arriving in Greece late wasn t really an option. And then, on an early morning in Croatia (about 2000km in) in heavy fog, I rode into a kerb at 35 km/h, bending the rim of my front wheel (but fortunately not coming off my bike). While I probably would have been able to continue with a replacement wheel (and mailing the broken one home), that would have taken another day to sort out and I almost certainly wouldn t have been able to source a new dynamo wheel in Croatia - which would have made night time riding a lot harder. So I decided to scratch and take the train home from Zagreb. Overall, I really enjoyed the event and I think I ve learned some useful lessons. I ll probably try again next year.

I forgot to write down the details back when it happened, but now that the surprise has been delivered I can write about it. A triangular fabric banner, black with a reflective grey border, and a penguin outline where part of the outline is in the shape of Lake Como screenprinted in white and light blue.

A triangular fabric banner, black with a reflective grey border, and a penguin outline where part of the outline is in the shape of Lake Como screenprinted in white and light blue.

Some time ago, I decided to make a small banner with the GL-Como penguin for a friend, because reasons. However, this friend has a big problem, he, well, is from Pisa (no, I m not from Leghorn, why do you ask?), and I had a screen printing kit, openclipart and no inhibitions. Three fabric banners: one is the one mentioned above, two are square with a yellow corded border, a yellow triangle and a tower of Pisa in black in the middle. The yellow triangles aren't perfectly flat yellow, but somewhat ruined, one more than the other.

Three fabric banners: one is the one mentioned above, two are square with a yellow corded border, a yellow triangle and a tower of Pisa in black in the middle. The yellow triangles aren't perfectly flat yellow, but somewhat ruined, one more than the other.

So, with the encouragement of a few friends who were in the secret, this happened. In two copies, because the first attempt at the print had issues. And yesterday we finally met that friend again, gave him all of the banners, and no violence happened, but he liked them :D

An ISO 7071-style triangle warning sign with a simplified tower of Pisa in black on yellow background.

If somebody is interested, the source image I used is on openclipart, with links to all of the sources I ve used. I don t remember exactly how it happened, but when I was working on the Pisani sign I also stumbled on the no dogs sign and decided that the world needed a mandatory cat sign, and well, here is the full set (all images are a link to the openclipart page).

ISO 7071 no dogs sign, a black dog on white background with a red circle with a diagonal line.

ISO 7071-style mandatory cats sign, a white cat on blue circle background.

ISO 7071-style mandatory dogs sign, a white dog on blue circle background.

ISO 7071-style no cats , a black cat on white background with a red circle with a diagonal line.

Many people seem to be pretending that the pandemic is over. It isn t. People are still getting Covid, becoming sick, and even in some cases becoming disabled. People s plans are still being disrupted. Vulnerable people are still hiding. Conference organisers: please make robust Covid policies, publish them early, and enforce them. And, clearly set expectations for your attendees. Attendees: please don t be the superspreader. Two conferences This year I have attended a number of in-person events. For Eastercon I chose to participate online, remotely. This turns out to have been a very good decision. At least a quarter of attendees got Covid. At BiCon we had about 300 attendees. I m not aware of any Covid cases. Part of the difference between the two may have been in the policies. BiCon s policy was rather more robust. Unlike Eastercon s it had a much better refund policy for people who got Covid and therefore shouldn t come; also BiCon asked attendees to actually show evidence of a negative test. Another part of the difference will have been the venue. The NTU buildings we used at BiCon were modern and well ventilated. But, I think the biggest difference was attendees' attitudes. BiCon attendees are disproportionately likely (compared to society at large) to have long term medical conditions. And the cultural norms are to value and protect those people. Conversely, in my experience, a larger proportion of Eastercon attendees don t always have the same level of consideration. I don t want to give details, but I have reliable reports of quite reprehensible behaviour by some attendees - even members of the convention volunteer staff. Policies Your conference should IMO at the very least:

Require everyone to show evidence of a negative test, on arrival.
Have a good refund policy that allows an attendee who would be a risk to others, to cancel without penalty.
Require everyone to provide proof of vaccination (or medical exemption).
Clearly state that a negative LFT is not an all clear
Instruct people not to attend, or to isolate if already on-site, if:
- they have new symptoms of respiratory illness
- they are a contact of known a positive case; or
- they have any other reason to suspect they ll be bringing Covid to the event.

The rules should be published very early, so that people can see them, and decide if they want to go, before they have to book anything. Don t recommend that people don t spread disease Most of the things that attendees can do to about Covid primarily protect others, rather than themselves. Making those things recommendations or advice is grossly unfair. You re setting up an arsehole filter: nice people will want to protect others, but less public spirited people will tell themselves it s only a recommendation. Make the rules mandatory. But won t we be driving people away ? If you don t have a robust Covid policy, you are already driving people away. And the people who won t come because of reasonable measures like I ve asked for above, are dickheads. You don t want them putting your other attendees at risk. And probably they re annoying in other ways too. Example of something that is not OK Yesterday (2023-08-30 13:44 UTC), less than two weeks before the conference, Debconf 23 s Covid policy still looked like you see below. Today there is a policy, but it is still weak.

Edited 2023-09-01 00:58 +01:00 to fix the link to the Debconf policy.

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Ayisha After a long time I saw a movie that I enjoyed wholeheartedly. And it unexpectedly touched my heart. The name of the movie is Ayisha. The first frame of the movie itself sets the pace where we see Ayisha (Manju Warrier) who decides to help out a gang as lot of women were being hassled. So she agrees to hoodwink cops and help launder some money. Then she is shown to work as a maid for an elite Arab family. To portray a Muslim character in these polarized times really shows guts especially when the othering of the Muslim has been happening 24 7. In fact, just few days back I was shocked to learn that Muslim homes were being marked as Jews homes had been marked in the 1930 s. Not just homes but also businesses too. And after few days in a total hypocritical fashion one of the judges says that you cannot push people to buy or not buy from a shop. This is after systemically doing the whole hate campaign for almost 2 weeks. What value the judge s statements are after 2 weeks ??? The poison has already seeped in But I m drifting from the topic/movie.

The real fun of the movie is the beautiful relationship that happens between Ayisha and Mama, she is the biggest maternal figure in the house and in fact, her command is what goes in the house. The house or palace which is the perfect description is shown as being opulent but not as rich as both Mama and Ayisha are, spiritually and emotionally both giving and sharing of each other. Almost a mother daughter relationship, although with others she is shown as having a bit of an iron hand. Halfway through the movie we come to know that Ayisha was also a dramatist and an actress having worked in early Malayalam movies. I do not want to go through all the ups and downs as that is the beauty of the movie and it needs to be seen for that aspect. I am always sort of in two worlds where should I promote a book or series or movie or not because most of the time it is the unexpected that works. When we have expectation it doesn t. Avatar, the Way of the Water is an exception, not many movies I can recall like that where I had expectations and still the movie surpassed it. So maybe go with no expectations at all

Manju Warrier Manju Warrier should actually be called Manju Warrior as she chose to be with the survivor rather than the sexism that is prevalent in the Malayalam film industry which actually is more or less a mirror of Bollywood and society as whole. These three links should give enough background knowledge as to what has been happening although I m sure my Malayalam friends would more than add to that knowledge whatever may be missing. In quite a few movies, the women are making inroads without significant male strength. Especially Manju s movies have no male lead for the last few movies. Whether that is deliberate part on Manju or an obstacle being put in front of her. Anyone knows that having a male lead and a female lead enriches the value of a movie quite a bit. This doesn t mean one is better than the other but having both enriches the end product, as simple as that. This is sadly not happening. Having POSH training and having an ICC is something that each organization should look forward for. It s kind of mandatory need of hour, especially when we have young people all around us. I am hopeful that people who are from Kerala would shed some more background light on what has been happening.

Books I haven t yet submitted an application for Debconf. But my idea is irrespective of whether or not I m there, I do hope we can have a library where people can donate books and people can take away books as well. A kind of circular marketplace/library where just somebody notes what books are available. Even if 100 odd people are coming to Debconf that easily means 100 books of various languages. That in itself would be interesting and to see what people are reading, wanting to discuss etc. We could even have readings. IIRC, in 2016 we had a children s area, maybe we could do some readings from some books to children which fuels their imagination. Even people like me who are deaf would be willing to look at excerpts and be charmed by them. For instance, in all my forays of fantasy literature except for Babylon Steel I haven t read one book that has a female lead character and I have read probably around 100 odd fantasy books till date. Not a lot but still to my mind, is a big gap as far as literature is concerned. How would more women write fantasy if they don t have heroes to look forward to :(. Or maybe I may be missing some authors and characters that others know and I do not. Do others feel the same or this question hasn t even been asked ??? Dunno. Please let me know.

Debutsav So apparently Debutsav is happening 2 days from now. While I did come to know about it few days back I had to think whether I want to apply for this or apply for Debconf as I physically, emotionally can t do justice to both even though they are a few months apart. I wish all the best for the attendees as well as presenters sharing all the projects and hopefully somebody shares at least some of the projects that are presented there so we may know what new projects or softwares to follow or whatever. Till later.

CAT-6 patch cord & ONU Few months back I was offered a fibre service. Most of the service offering has been using Chinese infrastructure including the ONU (Optical Network Unit). Wikipedia doesn t have a good page on ONU hence had to rely on third-party sites. FS (a name I don t really know) has some (good basic info. on ONU and how it s part and parcel of the whole infrastructure. I also got an ONT (Optical Network Terminal) but it seems to be very basic and mostly dumb. I used the old CAT-6 cable ( a decade old) to connect them and it worked for couple of months. Had to change it, first went to know if a higher cable solution offered themselves. CAT-7 is there but not backward compatible. CAT-8 is the next higher version but apparently it s expensive and also not easily bought. I did quite a few tests on CAT-6 and the ONU and it conks out at best 1 mbps which is still far better than what I am used to. CAT-8 are either not available or simply too expensive for home applications atm. A good summary of CAT-8 and what they stand for can be found here. The networking part is hopeless as most consumer facing CPU s and motherboards don t even offer 10 mbps, so asking anything more is just overkill without any benefit. Which does bring me to the next question, something that I may do in a few months or a year down the road. Just to clarify they may say it is 100 mbps or even 1 Gbps but that s plain wrong.

AMD APU, Asus Motherboard & Dealerships I had been thinking of an AMD APU, could wait a while but sooner or later would have to get one. I got quoted an AMD Ryzen 3 3200G with an Asus A320 Motherboard for around 14k which kinda looked steep to me. Quite a few hardware dealers whom I had traded, consulted over years simply shut down. While there are new people, it s much more harder now to make relationships (due to deafness) rather than before. The easiest to share which was also online was pcpartpicker.com that had an Indian domain now no longer available. The number of offline brick and mortar PC business has also closed quite a bit. There are a few new ones but it takes time and the big guys have made more of a killing. I was shocked quite a bit. Came home and browsed a bit and was hit by this. Both AMD and Intel PC business has taken a beating. AMD a bit more as Intel still holds part of the business segment as traditionally been theirs. There have been proofs and allegations of bribing in the past (do remember the EU Antitrust case against Intel for monopoly) but Intel s own cutting corners with the Spectre and Meltdown flaws hasn t helped its case, nor the suits themselves. AMD on the other hand under expertise of Lisa Su has simply grown strength by strength. Inflation and Profiteering by other big companies has made the outlook for both AMD and Intel a bit lackluster. AMD is supposed to show Zen5 chips in a few days time and the rumor mill has been ongoing. Correction Not few days but 2025. Personally, I would be happy with maybe a Ryzen 5600G with an Asus motherboard. My main motive whenever I buy an APU is not to hit beyond 65 TDP. It s kinda middle of the road. As far as what I could read this year and next year we could have AM4+ or something like those updates, AM5 APU s, CPU s and boards are slated to be launched in 2025. I did see pcpricetracker and it does give idea of various APU prices although have to say pcpartpicker was much intuitive to work with than the above. I just had my system cleaned couple of months so touchwood I should be able to use it for another couple of years or more before I have to get one of these APU s and do hope they are worth it. My idea is to use that not only for testing various softwares but also delve a bit into VR if that s possible. I did read a bit about deafness and VR as well. A good summary can be found here. I am hopeful that there may be few people in the community who may look and respond to that. It s crucial.

TRAI-caller, Privacy 101& Element. While most of us in Debian and FOSS communities do engage in privacy, lots of times it s frustrating. I m always looking for videos that seek to share that view why Privacy is needed by individuals and why Governments and other parties hate it. There are a couple of basic Youtube Videos that does explain the same quite practically.

Now why am I sharing the above. It isn t that people do not privacy and how we hold it dear. I share it because GOI just today blocked Element. While it may be trivial for us to workaround the issues, it does tell what GOI is doing. And it still acts as if surprised why it s press ranking is going to pits. Even our Women Wrestlers have been protesting for a week to just file an FIR (First Information Report) . And these are women who have got medals for the country. More than half of these organizations, specifically the women wrestling team don t have POSH which is a mandatory body supposed to be in every organization. POSH stands for Prevention of Sexual Harassment at Workplace. The gentleman concerned is a known rowdy/Goon hence it took almost a week of protest to do the needful I do try not to report because right now every other day we see somewhere or the other the Govt. curtailing our rights and most people are mute Signing out, till later

In my day job someone today took the time in the team daily to explain his research why some of our configuration is wrong. He spent quite some time on his own to look at the history in git and how everything was setup initially, and ended up in the current - wrong - way. That triggered me to validate that quickly, another 5min of work. So we agreed to change it. A one line change, nothing spectacular, but lifetime was invested to figure out why it should've a different value. When the pull request got opened a few minutes later there was nothing of that story in the commit message. Zero, nada, nothing.

I'm really puzzled why someone invests lifetime to dig into company internal history to try get something right, do a lengthy explanation to the whole team, use the time of others, even mention that there was no explanation of why it's not the default value anymore it should be, and repeat the same mistake by not writing down anything in the commit message. For the current company I'm inclined to propose a commit message validator. For a potential future company I might join, I guess I ask for real world git logs from repositories I should contribute to. Seems that this is another valuable source of information to qualify the company culture. Next up to the existence of whiteboards in the office. I'm really happy that at least a majority of the people contributing to Debian writes somewhat decent commit messages and changelogs. Let that be a reminder to myself to improve in that area the next time I've to change something.

I d like to describe and discuss a threat model for computational devices. This is generic but we will narrow it down to security-related devices. For example, portable hardware dongles used for OpenPGP/OpenSSH keys, FIDO/U2F, OATH HOTP/TOTP, PIV, payment cards, wallets etc and more permanently attached devices like a Hardware Security Module (HSM), a TPM-chip, or the hybrid variant of a mostly permanently-inserted but removable hardware security dongles. Our context is cryptographic hardware engineering, and the purpose of the threat model is to serve as as a thought experiment for how to build and design security devices that offer better protection. The threat model is related to the Evil maid attack. Our focus is to improve security for the end-user rather than the traditional focus to improve security for the organization that provides the token to the end-user, or to improve security for the site that the end-user is authenticating to. This is a critical but often under-appreciated distinction, and leads to surprising recommendations related to onboard key generation, randomness etc below.

The Substitution Attack
An attacker is able to substitute any component of the device (hardware or software) at any time for any period of time.
Your takeaway should be that devices should be designed to mitigate harmful consequences if any component of the device (hardware or software) is substituted for a malicious component for some period of time, at any time, during the lifespan of that component. Some designs protect better against this attack than other designs, and the threat model can be used to understand which designs are really bad, and which are less so.

Terminology The threat model involves at least one device that is well-behaving and one that is not, and we call these Good Device and Bad Device respectively. The bad device may be the same physical device as the good key, but with some minor software modification or a minor component replaced, but could also be a completely separate physical device. We don t care about that distinction, we just care if a particular device has a malicious component in it or not. I ll use terms like security device , device , hardware key , security co-processor etc interchangeably. From an engineering point of view, malicious here includes unintentional behavior such as software or hardware bugs. It is not possible to differentiate an intentionally malicious device from a well-designed device with a critical bug. Don t attribute to malice what can be adequately explained by stupidity, but don t na vely attribute to stupidity what may be deniable malicious.

What is some period of time ? Some period of time can be any length of time: seconds, minutes, days, weeks, etc. It may also occur at any time: During manufacturing, during transportation to the user, after first usage by the user, or after a couple of months usage by the user. Note that we intentionally consider time-of-manufacturing as a vulnerable phase. Even further, the substitution may occur multiple times. So the Good Key may be replaced with a Bad Key by the attacker for one day, then returned, and later this repeats a month later.

What is harmful consequences ? Since a security key has a fairly well-confined scope and purpose, we can get a fairly good exhaustive list of things that could go wrong. Harmful consequences include:

Attacker learns any secret keys stored on a Good Key.

Attacker causes user to trust a public generated by a Bad Key.

Attacker is able to sign something using a Good Key.

Attacker learns the PIN code used to unlock a Good Key.

Attacker learns data that is decrypted by a Good Key.

Thin vs Deep solutions One approach to mitigate many issues arising from device substitution is to have the host (or remote site) require that the device prove that it is the intended unique device before it continues to talk to it. This require an authentication/authorization protocol, which usually involves unique device identity and out-of-band trust anchors. Such trust anchors is often problematic, since a common use-case for security device is to connect it to a host that has never seen the device before. A weaker approach is to have the device prove that it merely belongs to a class of genuine devices from a trusted manufacturer, usually by providing a signature generated by a device-specific private key signed by the device manufacturer. This is weaker since then the user cannot differentiate two different good devices. In both cases, the host (or remote site) would stop talking to the device if it cannot prove that it is the intended key, or at least belongs to a class of known trusted genuine devices. Upon scrutiny, this solution is still vulnerable to a substitution attack, just earlier in the manufacturing chain: how can the process that injects the per-device or per-class identities/secrets know that it is putting them into a good key rather than a malicious device? Consider also the consequences if the cryptographic keys that guarantee that a device is genuine leaks. The model of the thin solution is similar to the old approach to network firewalls: have a filtering firewall that only lets through intended traffic, and then run completely insecure protocols internally such as telnet. The networking world has evolved, and now we have defense in depth: even within strongly firewall ed networks, it is prudent to run for example SSH with publickey-based user authentication even on locally physical trusted networks. This approach requires more thought and adds complexity, since each level has to provide some security checking. I m arguing we need similar defense-in-depth for security devices. Security key designs cannot simply dodge this problem by assuming it is working in a friendly environment where component substitution never occur.

Example: Device authentication using PIN codes To see how this threat model can be applied to reason about security key designs, let s consider a common design. Many security keys uses PIN codes to unlock private key operations, for example on OpenPGP cards that lacks built-in PIN-entry functionality. The software on the computer just sends a PIN code to the device, and the device allows private-key operations if the PIN code was correct. Let s apply the substitution threat model to this design: the attacker replaces the intended good key with a malicious device that saves a copy of the PIN code presented to it, and then gives out error messages. Once the user has entered the PIN code and gotten an error message, presumably temporarily giving up and doing other things, the attacker replaces the device back again. The attacker has learnt the PIN code, and can later use this to perform private-key operations on the good device. This means a good design involves not sending PIN codes in clear, but use a stronger authentication protocol that allows the card to know that the PIN was correct without learning the PIN. This is implemented optionally for many OpenPGP cards today as the key-derivation-function extension. That should be mandatory, and users should not use setups that sends device authentication in the clear, and ultimately security devices should not even include support for that. Compare how I build Gnuk on my PGP card with the `kdf_do=required` option.

Example: Onboard non-predictable key-generation Many devices offer both onboard key-generation, for example OpenPGP cards that generate a Ed25519 key internally on the devices, or externally where the device imports an externally generated cryptographic key. Let s apply the subsitution threat model to this design: the user wishes to generate a key and trust the public key that came out of that process. The attacker substitutes the device for a malicious device during key-generation, imports the private key into a good device and gives that back to the user. Most of the time except during key generation the user uses a good device but still the attacker succeeded in having the user trust a public key which the attacker knows the private key for. The substitution may be a software modification, and the method to leak the private key to the attacker may be out-of-band signalling. This means a good design never generates key on-board, but imports them from a user-controllable environment. That approach should be mandatory, and users should not use setups that generates private keys on-board, and ultimately security devices should not even include support for that.

Example: Non-predictable randomness-generation Many devices claims to generate random data, often with elaborate design documents explaining how good the randomness is. Let s apply the substitution threat model to this design: the attacker replaces the intended good key with a malicious design that generates (for the attacker) predictable randomness. The user will never be able to detect the difference since the random output is, well, random, and typically not distinguishable from weak randomness. The user cannot know if any cryptographic keys generated by a generator was faulty or not. This means a good design never generates non-predictable randomness on the device. That approach should be mandatory, and users should not use setups that generates non-predictable randomness on the device, and ideally devices should not have this functionality.

Case-Study: Tillitis I have warmed up a bit for this. Tillitis is a new security device with interesting properties, and core to its operation is the Compound Device Identifier (CDI), essentially your Ed25519 private key (used for SSH etc) is derived from the CDI that is computed like this:
cdi = blake2s(UDS, blake2s(device_app), USS)
Let s apply the substitution threat model to this design: Consider someone replacing the Tillitis key with a malicious key during postal delivery of the key to the user, and the replacement device is identical with the real Tillitis key but implements the following key derivation function:
cdi = weakprng(UDS , weakprng(device_app), USS)
Where `weakprng` is a compromised algorithm that is predictable for the attacker, but still appears random. Everything will work correctly, but the attacker will be able to learn the secrets used by the user, and the user will typically not be able to tell the difference since the CDI is secret and the Ed25519 public key is not self-verifiable.

Conclusion Remember that it is impossible to fully protect against this attack, that s why it is merely a thought experiment, intended to be used during design of these devices. Consider an attacker that never gives you access to a good key and as a user you only ever use a malicious device. There is no way to have good security in this situation. This is not hypothetical, many well-funded organizations do what they can to derive people from having access to trustworthy security devices. Philosophically it does not seem possible to tell if these organizations have succeeded 100% already and there are only bad security devices around where further resistance is futile, but to end on an optimistic note let s assume that there is a non-negligible chance that they haven t succeeded. In these situations, this threat model becomes useful to improve the situation by identifying less good designs, and that s why the design mantra of mitigate harmful consequences is crucial as a takeaway from this. Let s improve the design of security devices that further the security of its users!

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Multi-platform support Thanks to the interest and work of many volunteers, AppStream (mostly) runs on FreeBSD now, a NetBSD port exists, support for macOS was written and a Windows port is on its way! Thank you to everyone working on this

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