The OpenSSH project added support for a hybrid Streamlined NTRU Prime post-quantum key encapsulation method sntrup761 to strengthen their X25519-based default in their version 8.5 released on 2021-03-03. While there has been a lot of talk about post-quantum crypto generally, my impression has been that there has been a slowdown in implementing and deploying them in the past two years. Why is that? Regardless of the answer, we can try to collaboratively change things, and one effort that appears strangely missing are IETF documents for these algorithms.
Building on some earlier work that added X25519/X448 to SSH, writing a similar document was relatively straight-forward once I had spent a day reading OpenSSH and TinySSH source code to understand how it worked. While I am not perfectly happy with how the final key is derived from the sntrup761/X25519 secrets – it is a SHA512 call on the concatenated secrets – I think the construct deserves to be better documented, to pave the road for increased confidence or better designs. Also, reusing the RFC5656§4 structs makes for a worse specification (one unnecessary normative reference), but probably a simpler implementation. I have published draft-josefsson-ntruprime-ssh-00 here. Credit here goes to Jan Mojžíš of TinySSH that designed the earlier sntrup4591761x25519-sha512@tinyssh.org in 2018, Markus Friedl who added it to OpenSSH in 2019, and Damien Miller that changed it to sntrup761 in 2020. Does anyone have more to add to the history of this work?
Once I had sharpened my xml2rfc skills, preparing a document describing the hybrid construct between the sntrup761 key-encapsulation mechanism and the X25519 key agreement method in a non-SSH fashion was easy. I do not know if this work is useful, but it may serve as a reference for further study. I published draft-josefsson-ntruprime-hybrid-00 here.
Finally, how about a IETF document on the base Streamlined NTRU Prime? Explaining all the details, and especially the math behind it would be a significant effort. I started doing that, but realized it is a subjective call when to stop explaining things. If we can’t assume that the reader knows about lattice math, is a document like this the best place to teach it? I settled for the most minimal approach instead, merely giving an introduction to the algorithm, included SageMath and C reference implementations together with test vectors. The IETF audience rarely understands math, so I think it is better to focus on the bits on the wire and the algorithm interfaces. Everything here was created by the Streamlined NTRU Prime team, I merely modified it a bit hoping I didn’t break too much. I have now published draft-josefsson-ntruprime-streamlined-00 here.
I maintain the IETF documents on my ietf-ntruprime GitLab page, feel free to open merge requests or raise issues to help improve them.
To have confidence in the code was working properly, I ended up preparing a branch with sntrup761 for the GNU-project Nettle and have submitted it upstream for review. I had the misfortune of having to understand and implement NIST’s DRBG-CTR to compute the sntrup761 known-answer tests, and what a mess it is. Why does a deterministic random generator support re-seeding? Why does it support non-full entropy derivation? What’s with the key size vs block size confusion? What’s with the optional parameters? What’s with having multiple algorithm descriptions? Luckily I was able to extract a minimal but working implementation that is easy to read. I can’t locate DRBG-CTR test vectors, anyone? Does anyone have sntrup761 test vectors that doesn’t use DRBG-CTR? One final reflection on publishing known-answer tests for an algorithm that uses random data: are the test vectors stable over different ways to implement the algorithm? Just consider of some optimization moved one randomness-extraction call before another, then wouldn’t the output be different? Are there other ways to verify correctness of implementations?
Let’s reflect on some of my recent work that started with understanding Trisquel GNU/Linux, improving transparency into apt-archives, working on reproducible builds of Trisquel, strengthening verification of apt-archives with Sigstore, and finally thinking about security device threat models. A theme in all this is improving methods to have trust in machines, or generally any external entity. While I believe that everything starts by trusting something, usually something familiar and well-known, we need to deal with misuse of that trust that leads to failure to deliver what is desired and expected from the trusted entity. How can an entity behave to invite trust? Let’s argue for some properties that can be quantitatively measured, with a focus on computer software and hardware:
Deterministic Behavior – given a set of circumstances, it should behave the same.
Verifiability and Transparency – the method (the source code) should be accessible for understanding (compare scientific method) and its binaries verifiable, i.e., it should be possible to verify that the entity actually follows the intended deterministic method (implying efforts like reproducible builds and bootstrappable builds).
Accountable – the entity should behave the same for everyone, and deviation should be possible prove in a way that is hard to deny, implying efforts such as Certificate Transparency and more generic checksum logs like Sigstore and Sigsum.
Liberating – the tools and documentation should be available as free software to enable you to replace the trusted entity if so desired. An entity that wants to restrict you from being able to replace the trusted entity is vulnerable to corruption and may stop acting trustworthy. This point of view reinforces that open source misses the point; it has become too common to use trademark laws to restrict re-use of open source software (e.g., firefox, chrome, rust).
Essentially, this boils down to: Trust, Verify and Hold Accountable. To put this dogma in perspective, it helps to understand that this approach may be harmful to human relationships (which could explain the social awkwardness of hackers), but it remains useful as a method to improve the design of computer systems, and a useful method to evaluate safety of computer systems. When a system fails some of the criteria above, we know we have more work to do to improve it.
How far have we come on this journey? Through earlier efforts, we are in a fairly good situation. Richard Stallman through GNU/FSF made us aware of the importance of free software, the Reproducible/Bootstrappable build projects made us aware of the importance of verifiability, and Certificate Transparency highlighted the need for accountable signature logs leading to efforts like Sigstore for software. None of these efforts would have seen the light of day unless people wrote free software and packaged them into distributions that we can use, and built hardware that we can run it on. While there certainly exists more work to be done on the software side, with the recent amazing full-source build of Guix based on a 357-byte hand-written seed, I believe that we are closing that loop on the software engineering side.
So what remains? Some inspiration for further work:
Accountable binary software distribution remains unresolved in practice, although we have some software components around (e.g., apt-sigstore and guix git authenticate). What is missing is using them for verification by default and/or to improve the signature process to use trustworthy hardware devices, and committing the signatures to transparency logs.
Trustworthy hardware to run trustworthy software on remains a challenge, and we owe FSF’s Respect Your Freedom credit for raising awareness of this. Many modern devices requires non-free software to work which fails most of the criteria above and are thus inherently untrustworthy.
Verifying rebuilds of currently published binaries on trustworthy hardware is unresolved.
Completing a full-source rebuild from a small seed on trustworthy hardware remains, preferably on a platform wildly different than X86 such as Raptor’s Talos II.
We need improved security hardware devices and improved established practices on how to use them. For example, while Gnuk on the FST enable a trustworthy software and hardware solution, the best process for using it that I can think of generate the cryptographic keys on a more complex device. Efforts like Tillitis are inspiring here.
Onwards and upwards, happy hacking!
Update 2023-05-03: Added the “Liberating” property regarding free software, instead of having it be part of the “Verifiability and Transparency”.
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 naïvely 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!
The absolute number may not be impressive, but what I hope is at least a useful contribution is that there actually is a number on how much of Trisquel is reproducible. Hopefully this will inspire others to help improve the actual metric.
When I set about to understand how Trisquel worked, I identified a number of things that would improve my confidence in it. The lowest hanging fruit for me was to manually audit the package archive, and I wrote a tool called debdistdiff to automate this for me. That led me to think about apt archive transparency more in general. I have made some further work in that area (hint: apt-verify) that deserve its own blog post eventually. Most of apt archive transparency is futile if we don’t trust the intended packages that are in the archive. One way to measurable increase trust in the package are to provide reproducible builds of the packages, which should by now be an established best practice. Code review is still important, but since it will never provide positive guarantees we need other processes that can identify sub-optimal situations automatically. The way reproducible builds easily identify negative results is what I believe has driven much of its success: its results are tangible and measurable. The field of software engineering is in need of more such practices.
The design of my setup to build Trisquel reproducible are as follows.
The project debdistget is responsible for downloading Release/Packages files (which are the most relevant files from dists/) from apt archives, and works by commiting them into GitLab-hosted git-repositories. I maintain several such repositories for popular apt-archives, including for Trisquel and its upstream Ubuntu. GitLab invokes a schedule pipeline to do the downloading, and there is some race conditions here.
The project debdistdiff is used to produce the list of added and modified packages, which are the input to actually being able to know what packages to reproduce. It publishes human readable summary of difference for several distributions, including Trisquel vs Ubuntu. Early on I decided that rebuilding all of the upstream Ubuntu packages is out of scope for me: my personal trust in the official Debian/Ubuntu apt archives are greater than my trust of the added/modified packages in Trisquel.
The final project reproduce-trisquel puts the pieces together briefly as follows, everything being driven from its .gitlab-ci.yml file.
There is a (manually triggered) job generate-build-image to create a build image to speed up CI/CD runs, using a simple Dockerfile.
There is a (manually triggered) job generate-package-lists that uses debdistdiff to generate and store package lists and puts its output in lists/. The reason this is manually triggered right now is due to a race condition.
There is a (scheduled) job that does two things: from the package lists, the script generate-ci-packages.sh builds a GitLab CI/CD instruction file ci-packages.yml that describes jobs for each package to build. The second part is generate-readme.sh that re-generate the project’s README.md based on the build logs and diffoscope outputs that stored in the git repository.
Through the ci-packages.yml file, there is a large number of jobs that are dynamically defined, which currently are manually triggered to not overload the build servers. The script build-package.sh is invoked and attempts to rebuild a package, and stores build log and diffoscope output in the git project itself.
I did not expect to be able to use the GitLab shared runners to do the building, however they turned out to work quite well and I postponed setting up my own runner. There is a manually curated lists/disabled-aramo.txt with some packages that all required too much disk space or took over two hours to build. Today I finally took the time to setup a GitLab runner using podman running Trisquel aramo, and I expect to complete builds of the remaining packages soon — one of my Dell R630 server with 256GB RAM and dual 2680v4 CPUs should deliver sufficient performance.
Current limitations and ideas on further work (most are filed as project issues) include:
We don’t support *.buildinfo files. As far as I am aware, Trisquel does not publish them for their builds. Improving this would be a first step forward, anyone able to help? Compare buildinfo.debian.net. For example, many packages differ only in their NT_GNU_BUILD_ID symbol inside the ELF binary, see example diffoscope output for libgpg-error. By poking around in jenkins.trisquel.org I managed to discover that Trisquel built initramfs-utils in the randomized path /build/initramfs-tools-bzRLUp and hard-coding that path allowed me to reproduce that package. I expect the same to hold for many other packages. Unfortunately, this failure turned into success with that package moved the needle from 42% reproducibility to 43% however I didn’t let that stand in the way of a good headline.
The mechanism to download the Release/Package-files from dists/ is not fool-proof: we may not capture all ever published such files. While this is less of a concern for reproducibility, it is more of a concern for apt transparency. Still, having Trisquel provide a service similar to snapshot.debian.org would help.
Having at least one other CPU architecture would be nice.
Due to lack of time and mental focus, handling incremental updates of new versions of packages is not yet working. This means we only ever build one version of a package, and never discover any newly published versions of the same package. Now that Trisquel aramo is released, the expected rate of new versions should be low, but still happens due to security or backports.
Porting this to test supposedly FSDG-compliant distributions such as PureOS and Gnuinos should be relatively easy. I’m also looking at Devuan because of Gnuinos.
The elephant in the room is how reproducible Ubuntu is in the first place.
Happy Easter Hacking!
Update 2023-04-17: The original project “reproduce-trisquel” that was announced here has been archived and replaced with two projects, one generic “debdistreproduce” and one with results for Trisquel: “reproduce/trisquel“.
I’ve used hardware-backed OpenPGP keys since 2006 when I imported newly generated rsa1024 subkeys to a FSFE Fellowship card. This worked well for several years, and I recall buying more ZeitControl cards for multi-machine usage and backup purposes. As a side note, I recall being unsatisfied with the weak 1024-bit RSA subkeys at the time – my primary key was a somewhat stronger 1280-bit RSA key created back in 2002 — but OpenPGP cards at the time didn’t support more than 1024 bit RSA, and were (and still often are) also limited to power-of-two RSA key sizes which I dislike.
I had my master key on disk with a strong password for a while, mostly to refresh expiration time of the subkeys and to sign other’s OpenPGP keys. At some point I stopped carrying around encrypted copies of my master key. That was my main setup when I migrated to a new stronger RSA 3744 bit key with rsa2048 subkeys on a YubiKey NEO back in 2014. At that point, signing other’s OpenPGP keys was a rare enough occurrence that I settled with bringing out my offline machine to perform this operation, transferring the public key to sign on USB sticks. In 2019 I re-evaluated my OpenPGP setup and ended up creating a offline Ed25519 key with subkeys on a FST-01G running Gnuk. My approach for signing other’s OpenPGP keys were still to bring out my offline machine and sign things using the master secret using USB sticks for storage and transport. Which meant I almost never did that, because it took too much effort. So my 2019-era Ed25519 key still only has a handful of signatures on it, since I had essentially stopped signing other’s keys which is the traditional way of getting signatures in return.
None of this caused any critical problem for me because I continued to use my old 2014-era RSA3744 key in parallel with my new 2019-era Ed25519 key, since too many systems didn’t handle Ed25519. However, during 2022 this changed, and the only remaining environment that I still used my RSA3744 key for was in Debian — and they require OpenPGP signatures on the new key to allow it to replace an older key. I was in denial about this sub-optimal solution during 2022 and endured its practical consequences, having to use the YubiKey NEO (which I had replaced with a permanently inserted YubiKey Nano at some point) for Debian-related purposes alone.
In December 2022 I bought a new laptop and setup a FST-01SZ with my Ed25519 key, and while I have taken a vacation from Debian, I continue to extend the expiration period on the old RSA3744-key in case I will ever have to use it again, so the overall OpenPGP setup was still sub-optimal. Having two valid OpenPGP keys at the same time causes people to use both for email encryption (leading me to have to use both devices), and the WKD Key Discovery protocol doesn’t like two valid keys either. At FOSDEM’23 I ran into Andre Heinecke at GnuPG and I couldn’t help complain about how complex and unsatisfying all OpenPGP-related matters were, and he mildly ignored my rant and asked why I didn’t put the master key on another smartcard. The comment sunk in when I came home, and recently I connected all the dots and this post is a summary of what I did to move my offline OpenPGP master key to a Nitrokey Start.
First a word about device choice, I still prefer to use hardware devices that are as compatible with free software as possible, but the FST-01G or FST-01SZ are no longer easily available for purchase. I got a comment about Nitrokey start in my last post, and had two of them available to experiment with. There are things to dislike with the Nitrokey Start compared to the YubiKey (e.g., relative insecure chip architecture, the bulkier form factor and lack of FIDO/U2F/OATH support) but – as far as I know – there is no more widely available owner-controlled device that is manufactured for an intended purpose of implementing an OpenPGP card. Thus it hits the sweet spot for me.
Nitrokey Start
The first step is to run latest firmware on the Nitrokey Start – for bug-fixes and important OpenSSH 9.0 compatibility – and there are reproducible-built firmware published that you can install using pynitrokey. I run Trisquel 11 aramo on my laptop, which does not include the Python Pip package (likely because it promotes installing non-free software) so that was a slight complication. Building the firmware locally may have worked, and I would like to do that eventually to confirm the published firmware, however to save time I settled with installing the Ubuntu 22.04 packages on my machine:
$ sha256sum python3-pip*
ded6b3867a4a4cbaff0940cab366975d6aeecc76b9f2d2efa3deceb062668b1c python3-pip_22.0.2+dfsg-1ubuntu0.2_all.deb
e1561575130c41dc3309023a345de337e84b4b04c21c74db57f599e267114325 python3-pip-whl_22.0.2+dfsg-1ubuntu0.2_all.deb
$ doas dpkg -i python3-pip*
...
$ doas apt install -f
...
$
Installing pynitrokey downloaded a bunch of dependencies, and it would be nice to audit the license and security vulnerabilities for each of them. (Verbose output below slightly redacted.)
jas@kaka:~$ pip3 install --user pynitrokey
Collecting pynitrokey
Downloading pynitrokey-0.4.34-py3-none-any.whl (572 kB)
Collecting frozendict~=2.3.4
Downloading frozendict-2.3.5-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (113 kB)
Requirement already satisfied: click<9,>=8.0.0 in /usr/lib/python3/dist-packages (from pynitrokey) (8.0.3)
Collecting ecdsa
Downloading ecdsa-0.18.0-py2.py3-none-any.whl (142 kB)
Collecting python-dateutil~=2.7.0
Downloading python_dateutil-2.7.5-py2.py3-none-any.whl (225 kB)
Collecting fido2<2,>=1.1.0
Downloading fido2-1.1.0-py3-none-any.whl (201 kB)
Collecting tlv8
Downloading tlv8-0.10.0.tar.gz (16 kB)
Preparing metadata (setup.py) ... done
Requirement already satisfied: certifi>=14.5.14 in /usr/lib/python3/dist-packages (from pynitrokey) (2020.6.20)
Requirement already satisfied: pyusb in /usr/lib/python3/dist-packages (from pynitrokey) (1.2.1.post1)
Collecting urllib3~=1.26.7
Downloading urllib3-1.26.15-py2.py3-none-any.whl (140 kB)
Collecting spsdk<1.8.0,>=1.7.0
Downloading spsdk-1.7.1-py3-none-any.whl (684 kB)
Collecting typing_extensions~=4.3.0
Downloading typing_extensions-4.3.0-py3-none-any.whl (25 kB)
Requirement already satisfied: cryptography<37,>=3.4.4 in /usr/lib/python3/dist-packages (from pynitrokey) (3.4.8)
Collecting intelhex
Downloading intelhex-2.3.0-py2.py3-none-any.whl (50 kB)
Collecting nkdfu
Downloading nkdfu-0.2-py3-none-any.whl (16 kB)
Requirement already satisfied: requests in /usr/lib/python3/dist-packages (from pynitrokey) (2.25.1)
Collecting tqdm
Downloading tqdm-4.65.0-py3-none-any.whl (77 kB)
Collecting nrfutil<7,>=6.1.4
Downloading nrfutil-6.1.7.tar.gz (845 kB)
Preparing metadata (setup.py) ... done
Requirement already satisfied: cffi in /usr/lib/python3/dist-packages (from pynitrokey) (1.15.0)
Collecting crcmod
Downloading crcmod-1.7.tar.gz (89 kB)
Preparing metadata (setup.py) ... done
Collecting libusb1==1.9.3
Downloading libusb1-1.9.3-py3-none-any.whl (60 kB)
Collecting pc_ble_driver_py>=0.16.4
Downloading pc_ble_driver_py-0.17.0-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (2.9 MB)
Collecting piccata
Downloading piccata-2.0.3-py3-none-any.whl (21 kB)
Collecting protobuf<4.0.0,>=3.17.3
Downloading protobuf-3.20.3-cp310-cp310-manylinux_2_12_x86_64.manylinux2010_x86_64.whl (1.1 MB)
Collecting pyserial
Downloading pyserial-3.5-py2.py3-none-any.whl (90 kB)
Collecting pyspinel>=1.0.0a3
Downloading pyspinel-1.0.3.tar.gz (58 kB)
Preparing metadata (setup.py) ... done
Requirement already satisfied: pyyaml in /usr/lib/python3/dist-packages (from nrfutil<7,>=6.1.4->pynitrokey) (5.4.1)
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Building wheels for collected packages: nrfutil, crcmod, sly, tlv8, commentjson, hexdump, pyspinel, fire, intervaltree, lark-parser, naturalsort, future
Building wheel for nrfutil (setup.py) ... done
Created wheel for nrfutil: filename=nrfutil-6.1.7-py3-none-any.whl size=898520 sha256=de6f8803f51d6c26d24dc7df6292064a468ff3f389d73370433fde5582b84a10
Stored in directory: /home/jas/.cache/pip/wheels/39/2b/9b/98ab2dd716da746290e6728bdb557b14c1c9a54cb9ed86e13b
Building wheel for crcmod (setup.py) ... done
Created wheel for crcmod: filename=crcmod-1.7-cp310-cp310-linux_x86_64.whl size=31422 sha256=5149ac56fcbfa0606760eef5220fcedc66be560adf68cf38c604af3ad0e4a8b0
Stored in directory: /home/jas/.cache/pip/wheels/85/4c/07/72215c529bd59d67e3dac29711d7aba1b692f543c808ba9e86
Building wheel for sly (setup.py) ... done
Created wheel for sly: filename=sly-0.4-py3-none-any.whl size=27352 sha256=f614e413918de45c73d1e9a8dca61ca07dc760d9740553400efc234c891f7fde
Stored in directory: /home/jas/.cache/pip/wheels/a2/23/4a/6a84282a0d2c29f003012dc565b3126e427972e8b8157ea51f
Building wheel for tlv8 (setup.py) ... done
Created wheel for tlv8: filename=tlv8-0.10.0-py3-none-any.whl size=11266 sha256=3ec8b3c45977a3addbc66b7b99e1d81b146607c3a269502b9b5651900a0e2d08
Stored in directory: /home/jas/.cache/pip/wheels/e9/35/86/66a473cc2abb0c7f21ed39c30a3b2219b16bd2cdb4b33cfc2c
Building wheel for commentjson (setup.py) ... done
Created wheel for commentjson: filename=commentjson-0.9.0-py3-none-any.whl size=12092 sha256=28b6413132d6d7798a18cf8c76885dc69f676ea763ffcb08775a3c2c43444f4a
Stored in directory: /home/jas/.cache/pip/wheels/7d/90/23/6358a234ca5b4ec0866d447079b97fedf9883387d1d7d074e5
Building wheel for hexdump (setup.py) ... done
Created wheel for hexdump: filename=hexdump-3.3-py3-none-any.whl size=8913 sha256=79dfadd42edbc9acaeac1987464f2df4053784fff18b96408c1309b74fd09f50
Stored in directory: /home/jas/.cache/pip/wheels/26/28/f7/f47d7ecd9ae44c4457e72c8bb617ef18ab332ee2b2a1047e87
Building wheel for pyspinel (setup.py) ... done
Created wheel for pyspinel: filename=pyspinel-1.0.3-py3-none-any.whl size=65033 sha256=01dc27f81f28b4830a0cf2336dc737ef309a1287fcf33f57a8a4c5bed3b5f0a6
Stored in directory: /home/jas/.cache/pip/wheels/95/ec/4b/6e3e2ee18e7292d26a65659f75d07411a6e69158bb05507590
Building wheel for fire (setup.py) ... done
Created wheel for fire: filename=fire-0.5.0-py2.py3-none-any.whl size=116951 sha256=3d288585478c91a6914629eb739ea789828eb2d0267febc7c5390cb24ba153e8
Stored in directory: /home/jas/.cache/pip/wheels/90/d4/f7/9404e5db0116bd4d43e5666eaa3e70ab53723e1e3ea40c9a95
Building wheel for intervaltree (setup.py) ... done
Created wheel for intervaltree: filename=intervaltree-3.1.0-py2.py3-none-any.whl size=26119 sha256=5ff1def22ba883af25c90d90ef7c6518496fcd47dd2cbc53a57ec04cd60dc21d
Stored in directory: /home/jas/.cache/pip/wheels/fa/80/8c/43488a924a046b733b64de3fac99252674c892a4c3801c0a61
Building wheel for lark-parser (setup.py) ... done
Created wheel for lark-parser: filename=lark_parser-0.7.8-py2.py3-none-any.whl size=62527 sha256=3d2ec1d0f926fc2688d40777f7ef93c9986f874169132b1af590b6afc038f4be
Stored in directory: /home/jas/.cache/pip/wheels/29/30/94/33e8b58318aa05cb1842b365843036e0280af5983abb966b83
Building wheel for naturalsort (setup.py) ... done
Created wheel for naturalsort: filename=naturalsort-1.5.1-py3-none-any.whl size=7526 sha256=bdecac4a49f2416924548cae6c124c85d5333e9e61c563232678ed182969d453
Stored in directory: /home/jas/.cache/pip/wheels/a6/8e/c9/98cfa614fff2979b457fa2d9ad45ec85fa417e7e3e2e43be51
Building wheel for future (setup.py) ... done
Created wheel for future: filename=future-0.18.3-py3-none-any.whl size=492037 sha256=57a01e68feca2b5563f5f624141267f399082d2f05f55886f71b5d6e6cf2b02c
Stored in directory: /home/jas/.cache/pip/wheels/5e/a9/47/f118e66afd12240e4662752cc22cefae5d97275623aa8ef57d
Successfully built nrfutil crcmod sly tlv8 commentjson hexdump pyspinel fire intervaltree lark-parser naturalsort future
Installing collected packages: tlv8, sortedcontainers, sly, pyserial, pyelftools, piccata, naturalsort, libusb1, lark-parser, intelhex, hexdump, fastjsonschema, crcmod, asn1crypto, wrapt, urllib3, typing_extensions, tqdm, termcolor, ruamel.yaml.clib, python-dateutil, pyspinel, pypemicro, pycryptodome, psutil, protobuf, prettytable, oscrypto, milksnake, libusbsio, jinja2, intervaltree, humanfriendly, future, frozendict, fido2, ecdsa, deepmerge, commentjson, click-option-group, click-command-tree, capstone, astunparse, argparse-addons, ruamel.yaml, pyocd-pemicro, pylink-square, pc_ble_driver_py, fire, cmsis-pack-manager, bincopy, pyocd, nrfutil, nkdfu, spsdk, pynitrokey
WARNING: The script nitropy is installed in '/home/jas/.local/bin' which is not on PATH.
Consider adding this directory to PATH or, if you prefer to suppress this warning, use --no-warn-script-location.
Successfully installed argparse-addons-0.12.0 asn1crypto-1.5.1 astunparse-1.6.3 bincopy-17.10.3 capstone-4.0.2 click-command-tree-1.1.0 click-option-group-0.5.5 cmsis-pack-manager-0.2.10 commentjson-0.9.0 crcmod-1.7 deepmerge-0.3.0 ecdsa-0.18.0 fastjsonschema-2.16.3 fido2-1.1.0 fire-0.5.0 frozendict-2.3.5 future-0.18.3 hexdump-3.3 humanfriendly-10.0 intelhex-2.3.0 intervaltree-3.1.0 jinja2-3.0.3 lark-parser-0.7.8 libusb1-1.9.3 libusbsio-2.1.11 milksnake-0.1.5 naturalsort-1.5.1 nkdfu-0.2 nrfutil-6.1.7 oscrypto-1.3.0 pc_ble_driver_py-0.17.0 piccata-2.0.3 prettytable-2.5.0 protobuf-3.20.3 psutil-5.9.4 pycryptodome-3.17 pyelftools-0.29 pylink-square-0.11.1 pynitrokey-0.4.34 pyocd-0.31.0 pyocd-pemicro-1.1.5 pypemicro-0.1.11 pyserial-3.5 pyspinel-1.0.3 python-dateutil-2.7.5 ruamel.yaml-0.17.21 ruamel.yaml.clib-0.2.7 sly-0.4 sortedcontainers-2.4.0 spsdk-1.7.1 termcolor-2.2.0 tlv8-0.10.0 tqdm-4.65.0 typing_extensions-4.3.0 urllib3-1.26.15 wrapt-1.15.0
jas@kaka:~$
Then upgrading the device worked remarkable well, although I wish that the tool would have printed URLs and checksums for the firmware files to allow easy confirmation.
jas@kaka:~$ PATH=$PATH:/home/jas/.local/bin
jas@kaka:~$ nitropy start list
Command line tool to interact with Nitrokey devices 0.4.34
:: 'Nitrokey Start' keys:
FSIJ-1.2.15-5D271572: Nitrokey Nitrokey Start (RTM.12.1-RC2-modified)
jas@kaka:~$ nitropy start update
Command line tool to interact with Nitrokey devices 0.4.34
Nitrokey Start firmware update tool
Platform: Linux-5.15.0-67-generic-x86_64-with-glibc2.35
System: Linux, is_linux: True
Python: 3.10.6
Saving run log to: /tmp/nitropy.log.gc5753a8
Admin PIN:
Firmware data to be used:
- FirmwareType.REGNUAL: 4408, hash: ...b'72a30389' valid (from ...built/RTM.13/regnual.bin)
- FirmwareType.GNUK: 129024, hash: ...b'25a4289b' valid (from ...prebuilt/RTM.13/gnuk.bin)
Currently connected device strings:
Device:
Vendor: Nitrokey
Product: Nitrokey Start
Serial: FSIJ-1.2.15-5D271572
Revision: RTM.12.1-RC2-modified
Config: *:*:8e82
Sys: 3.0
Board: NITROKEY-START-G
initial device strings: [{'name': '', 'Vendor': 'Nitrokey', 'Product': 'Nitrokey Start', 'Serial': 'FSIJ-1.2.15-5D271572', 'Revision': 'RTM.12.1-RC2-modified', 'Config': '*:*:8e82', 'Sys': '3.0', 'Board': 'NITROKEY-START-G'}]
Please note:
- Latest firmware available is:
RTM.13 (published: 2022-12-08T10:59:11Z)
- provided firmware: None
- all data will be removed from the device!
- do not interrupt update process - the device may not run properly!
- the process should not take more than 1 minute
Do you want to continue? [yes/no]: yes
...
Starting bootloader upload procedure
Device: Nitrokey Start FSIJ-1.2.15-5D271572
Connected to the device
Running update!
Do NOT remove the device from the USB slot, until further notice
Downloading flash upgrade program...
Executing flash upgrade...
Waiting for device to appear:
Wait 20 seconds.....
Downloading the program
Protecting device
Finish flashing
Resetting device
Update procedure finished. Device could be removed from USB slot.
Currently connected device strings (after upgrade):
Device:
Vendor: Nitrokey
Product: Nitrokey Start
Serial: FSIJ-1.2.19-5D271572
Revision: RTM.13
Config: *:*:8e82
Sys: 3.0
Board: NITROKEY-START-G
device can now be safely removed from the USB slot
final device strings: [{'name': '', 'Vendor': 'Nitrokey', 'Product': 'Nitrokey Start', 'Serial': 'FSIJ-1.2.19-5D271572', 'Revision': 'RTM.13', 'Config': '*:*:8e82', 'Sys': '3.0', 'Board': 'NITROKEY-START-G'}]
finishing session 2023-03-16 21:49:07.371291
Log saved to: /tmp/nitropy.log.gc5753a8
jas@kaka:~$
jas@kaka:~$ nitropy start list
Command line tool to interact with Nitrokey devices 0.4.34
:: 'Nitrokey Start' keys:
FSIJ-1.2.19-5D271572: Nitrokey Nitrokey Start (RTM.13)
jas@kaka:~$
Before importing the master key to this device, it should be configured. Note the commands in the beginning to make sure scdaemon/pcscd is not running because they may have cached state from earlier cards. Change PIN code as you like after this, my experience with Gnuk was that the Admin PIN had to be changed first, then you import the key, and then you change the PIN.
jas@kaka:~$ gpg-connect-agent "SCD KILLSCD" "SCD BYE" /bye
OK
ERR 67125247 Slut på fil <GPG Agent>
jas@kaka:~$ ps auxww|grep -e pcsc -e scd
jas 11651 0.0 0.0 3468 1672 pts/0 R+ 21:54 0:00 grep --color=auto -e pcsc -e scd
jas@kaka:~$ gpg --card-edit
Reader ...........: 20A0:4211:FSIJ-1.2.19-5D271572:0
Application ID ...: D276000124010200FFFE5D2715720000
Application type .: OpenPGP
Version ..........: 2.0
Manufacturer .....: unmanaged S/N range
Serial number ....: 5D271572
Name of cardholder: [not set]
Language prefs ...: [not set]
Salutation .......:
URL of public key : [not set]
Login data .......: [not set]
Signature PIN ....: forced
Key attributes ...: rsa2048 rsa2048 rsa2048
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 3 3
Signature counter : 0
KDF setting ......: off
Signature key ....: [none]
Encryption key....: [none]
Authentication key: [none]
General key info..: [none]
gpg/card> admin
Admin commands are allowed
gpg/card> kdf-setup
gpg/card> passwd
gpg: OpenPGP card no. D276000124010200FFFE5D2715720000 detected
1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit
Your selection? 3
PIN changed.
1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit
Your selection? q
gpg/card> name
Cardholder's surname: Josefsson
Cardholder's given name: Simon
gpg/card> lang
Language preferences: sv
gpg/card> sex
Salutation (M = Mr., F = Ms., or space): m
gpg/card> login
Login data (account name): jas
gpg/card> url
URL to retrieve public key: https://josefsson.org/key-20190320.txt
gpg/card> forcesig
gpg/card> key-attr
Changing card key attribute for: Signature key
Please select what kind of key you want:
(1) RSA
(2) ECC
Your selection? 2
Please select which elliptic curve you want:
(1) Curve 25519
(4) NIST P-384
Your selection? 1
The card will now be re-configured to generate a key of type: ed25519
Note: There is no guarantee that the card supports the requested size.
If the key generation does not succeed, please check the
documentation of your card to see what sizes are allowed.
Changing card key attribute for: Encryption key
Please select what kind of key you want:
(1) RSA
(2) ECC
Your selection? 2
Please select which elliptic curve you want:
(1) Curve 25519
(4) NIST P-384
Your selection? 1
The card will now be re-configured to generate a key of type: cv25519
Changing card key attribute for: Authentication key
Please select what kind of key you want:
(1) RSA
(2) ECC
Your selection? 2
Please select which elliptic curve you want:
(1) Curve 25519
(4) NIST P-384
Your selection? 1
The card will now be re-configured to generate a key of type: ed25519
gpg/card>
jas@kaka:~$ gpg --card-edit
Reader ...........: 20A0:4211:FSIJ-1.2.19-5D271572:0
Application ID ...: D276000124010200FFFE5D2715720000
Application type .: OpenPGP
Version ..........: 2.0
Manufacturer .....: unmanaged S/N range
Serial number ....: 5D271572
Name of cardholder: Simon Josefsson
Language prefs ...: sv
Salutation .......: Mr.
URL of public key : https://josefsson.org/key-20190320.txt
Login data .......: jas
Signature PIN ....: not forced
Key attributes ...: ed25519 cv25519 ed25519
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 3 3
Signature counter : 0
KDF setting ......: on
Signature key ....: [none]
Encryption key....: [none]
Authentication key: [none]
General key info..: [none]
jas@kaka:~$
Once setup, bring out your offline machine and boot it and mount your USB stick with the offline key. The paths below will be different, and this is using a somewhat unorthodox approach of working with fresh GnuPG configuration paths that I chose for the USB stick.
jas@kaka:/media/jas/2c699cbd-b77e-4434-a0d6-0c4965864296$ cp -a gnupghome-backup-masterkey gnupghome-import-nitrokey-5D271572
jas@kaka:/media/jas/2c699cbd-b77e-4434-a0d6-0c4965864296$ gpg --homedir $PWD/gnupghome-import-nitrokey-5D271572 --edit-key B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE
gpg (GnuPG) 2.2.27; Copyright (C) 2021 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Secret key is available.
sec ed25519/D73CF638C53C06BE
created: 2019-03-20 expired: 2019-10-22 usage: SC
trust: ultimate validity: expired
[ expired] (1). Simon Josefsson <simon@josefsson.org>
gpg> keytocard
Really move the primary key? (y/N) y
Please select where to store the key:
(1) Signature key
(3) Authentication key
Your selection? 1
sec ed25519/D73CF638C53C06BE
created: 2019-03-20 expired: 2019-10-22 usage: SC
trust: ultimate validity: expired
[ expired] (1). Simon Josefsson <simon@josefsson.org>
gpg>
Save changes? (y/N) y
jas@kaka:/media/jas/2c699cbd-b77e-4434-a0d6-0c4965864296$
Don’t forget to change the PIN at this point. At this point it is useful to confirm that the Nitrokey has the master key available and that is possible to sign statements with it, back on your regular machine:
jas@kaka:~$ gpg --card-status
Reader ...........: 20A0:4211:FSIJ-1.2.19-5D271572:0
Application ID ...: D276000124010200FFFE5D2715720000
Application type .: OpenPGP
Version ..........: 2.0
Manufacturer .....: unmanaged S/N range
Serial number ....: 5D271572
Name of cardholder: Simon Josefsson
Language prefs ...: sv
Salutation .......: Mr.
URL of public key : https://josefsson.org/key-20190320.txt
Login data .......: jas
Signature PIN ....: not forced
Key attributes ...: ed25519 cv25519 ed25519
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 3 3
Signature counter : 1
KDF setting ......: on
Signature key ....: B1D2 BD13 75BE CB78 4CF4 F8C4 D73C F638 C53C 06BE
created ....: 2019-03-20 23:37:24
Encryption key....: [none]
Authentication key: [none]
General key info..: pub ed25519/D73CF638C53C06BE 2019-03-20 Simon Josefsson <simon@josefsson.org>
sec> ed25519/D73CF638C53C06BE created: 2019-03-20 expires: 2023-09-19
card-no: FFFE 5D271572
ssb> ed25519/80260EE8A9B92B2B created: 2019-03-20 expires: 2023-09-19
card-no: FFFE 42315277
ssb> ed25519/51722B08FE4745A2 created: 2019-03-20 expires: 2023-09-19
card-no: FFFE 42315277
ssb> cv25519/02923D7EE76EBD60 created: 2019-03-20 expires: 2023-09-19
card-no: FFFE 42315277
jas@kaka:~$ echo foo|gpg -a --sign|gpg --verify
gpg: Signature made Thu Mar 16 22:11:02 2023 CET
gpg: using EDDSA key B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE
gpg: Good signature from "Simon Josefsson <simon@josefsson.org>" [ultimate]
jas@kaka:~$
Finally to retrieve and sign a key, for example Andre Heinecke’s that I could confirm the OpenPGP key identifier from his business card.
jas@kaka:~$ gpg --locate-external-keys aheinecke@gnupg.com
gpg: key 1FDF723CF462B6B1: public key "Andre Heinecke <aheinecke@gnupg.com>" imported
gpg: Total number processed: 1
gpg: imported: 1
gpg: marginals needed: 3 completes needed: 1 trust model: pgp
gpg: depth: 0 valid: 2 signed: 7 trust: 0-, 0q, 0n, 0m, 0f, 2u
gpg: depth: 1 valid: 7 signed: 64 trust: 7-, 0q, 0n, 0m, 0f, 0u
gpg: next trustdb check due at 2023-05-26
pub rsa3072 2015-12-08 [SC] [expires: 2025-12-05]
94A5C9A03C2FE5CA3B095D8E1FDF723CF462B6B1
uid [ unknown] Andre Heinecke <aheinecke@gnupg.com>
sub ed25519 2017-02-13 [S]
sub ed25519 2017-02-13 [A]
sub rsa3072 2015-12-08 [E] [expires: 2025-12-05]
sub rsa3072 2015-12-08 [A] [expires: 2025-12-05]
jas@kaka:~$ gpg --edit-key "94A5C9A03C2FE5CA3B095D8E1FDF723CF462B6B1"
gpg (GnuPG) 2.2.27; Copyright (C) 2021 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
pub rsa3072/1FDF723CF462B6B1
created: 2015-12-08 expires: 2025-12-05 usage: SC
trust: unknown validity: unknown
sub ed25519/2978E9D40CBABA5C
created: 2017-02-13 expires: never usage: S
sub ed25519/DC74D901C8E2DD47
created: 2017-02-13 expires: never usage: A
The following key was revoked on 2017-02-23 by RSA key 1FDF723CF462B6B1 Andre Heinecke <aheinecke@gnupg.com>
sub cv25519/1FFE3151683260AB
created: 2017-02-13 revoked: 2017-02-23 usage: E
sub rsa3072/8CC999BDAA45C71F
created: 2015-12-08 expires: 2025-12-05 usage: E
sub rsa3072/6304A4B539CE444A
created: 2015-12-08 expires: 2025-12-05 usage: A
[ unknown] (1). Andre Heinecke <aheinecke@gnupg.com>
gpg> sign
pub rsa3072/1FDF723CF462B6B1
created: 2015-12-08 expires: 2025-12-05 usage: SC
trust: unknown validity: unknown
Primary key fingerprint: 94A5 C9A0 3C2F E5CA 3B09 5D8E 1FDF 723C F462 B6B1
Andre Heinecke <aheinecke@gnupg.com>
This key is due to expire on 2025-12-05.
Are you sure that you want to sign this key with your
key "Simon Josefsson <simon@josefsson.org>" (D73CF638C53C06BE)
Really sign? (y/N) y
gpg> quit
Save changes? (y/N) y
jas@kaka:~$
This is on my day-to-day machine, using the NitroKey Start with the offline key. No need to boot the old offline machine just to sign keys or extend expiry anymore! At FOSDEM’23 I managed to get at least one DD signature on my new key, and the Debian keyring maintainers accepted my Ed25519 key. Hopefully I can now finally let my 2014-era RSA3744 key expire in 2023-09-19 and not extend it any further. This should finish my transition to a simpler OpenPGP key setup, yay!
I’ve always found the operation of apt software package repositories to be a mystery. There appears to be a lack of transparency into which people have access to important apt package repositories out there, how the automatic non-human update mechanism is implemented, and what changes are published. I’m thinking of big distributions like Ubuntu and Debian, but also the free GNU/Linux distributions like Trisquel and PureOS that are derived from the more well-known distributions.
As far as I can tell, anyone who has the OpenPGP private key trusted by a apt-based GNU/Linux distribution can sign a modified Release/InRelease file and if my machine somehow downloads that version of the release file, my machine could be made to download and install packages that the distribution didn’t intend me to install. Further, it seems that anyone who has access to the main HTTP server, or any of its mirrors, or is anywhere on the network between them and my machine (when plaintext HTTP is used), can either stall security updates on my machine (on a per-IP basis), or use it to send my machine (again, on a per-IP basis to avoid detection) a modified Release/InRelease file if they had been able to obtain the private signing key for the archive. These are mighty powers that warrant overview.
I’ve always put off learning about the processes to protect the apt infrastructure, mentally filing it under “so many people rely on this infrastructure that enough people are likely to have invested time reviewing and improving these processes”. Simultaneous, I’ve always followed the more free-software friendly Debian-derived distributions such as gNewSense and have run it on some machines. I’ve never put them into serious production use, because the trust issues with their apt package repositories has been a big question mark for me. The “enough people” part of my rationale for deferring this is not convincing. Even the simple question of “is someone updating the apt repository” is not easy to understand on a running gNewSense system. At some point in time the gNewSense cron job to pull in security updates from Debian must have stopped working, and I wouldn’t have had any good mechanism to notice that. Most likely it happened without any public announcement. I’ve recently switched to Trisquel on production machines, and these questions has come back to haunt me.
The situation is unsatisfying and I looked into what could be done to improve it. I could try to understand who are the key people involved in each project, and may even learn what hardware component is used, or what software is involved to update and sign apt repositories. Is the server running non-free software? Proprietary BIOS or NIC firmware? Are the GnuPG private keys on disk? Smartcard? TPM? YubiKey? HSM? Where is the server co-located, and who has access to it? I tried to do a bit of this, and discovered things like Trisquel having a DSA1024 key in its default apt trust store (although for fairness, it seems that apt by default does not trust such signatures). However, I’m not certain understanding this more would scale to securing my machines against attacks on this infrastructure. Even people with the best intentions, and the state of the art hardware and software, will have problems.
To increase my trust in Trisquel I set out to understand how it worked. To make it easier to sort out what the interesting parts of the Trisquel archive to audit further were, I created debdistdiff to produce human readable text output comparing one apt archive with another apt archive. There is a GitLab CI/CD cron job that runs this every day, producing output comparing Trisquel vs Ubuntu and PureOS vs Debian. Working with these output files has made me learn more about how the process works, and I even stumbled upon something that is likely a bug where Trisquel aramo was imported from Ubuntu jammy while it contained a couple of package (e.g., gcc-8, python3.9) that were removed for the final Ubuntu jammy release.
After working on auditing the Trisquel archive manually that way, I realized that whatever I could tell from comparing Trisquel with Ubuntu, it would only be something based on a current snapshot of the archives. Tomorrow it may look completely different. What felt necessary was to audit the differences of the Trisquel archive continously. I was quite happy to have developed debdistdiff for one purpose (comparing two different archives like Trisquel and Ubuntu) and discovered that the tool could be used for another purpose (comparing the Trisquel archive at two different points in time). At this time I realized that I needed a log of all different apt archive metadata to be able to produce an audit log of the differences in time for the archive. I create manually curated git-repositories with the Release/InRelease and the Packages files for each architecture/component of the well-known distributions Trisquel, Ubuntu, Debian and PureOS. Eventually I wrote scripts to automate this, which are now published in the debdistget project.
At this point, one of the early question about per-IP substitution of Release files were lingering in my mind. However with the tooling I now had available, coming up with a way to resolve this was simple! Merely have apt compute a SHA256 checksum of the just downloaded InRelease file, and see if my git repository had the same file. At this point I started reading the Apt source code, and now I had more doubts about the security of my systems than I ever had before. Oh boy how the name Apt has never before felt more… Apt?! Oh well, we must leave some exercises for the students. Eventually I realized I wanted to touch as little of apt code basis as possible, and noticed the SigVerify::CopyAndVerify function called ExecGPGV which called apt-key verify which called GnuPG’s gpgv. By setting Apt::Key::gpgvcommand I could get apt-key verify to call another tool than gpgv. See where I’m going? I thought wrapping this up would now be trivial but for some reason the hash checksum I computed locally never matched what was on my server. I gave up and started working on other things instead.
Today I came back to this idea, and started to debug exactly how the local files looked that I got from apt and how they differed from what I had in my git repositories, that came straight from the apt archives. Eventually I traced this back to SplitClearSignedFile which takes an InRelease file and splits it into two files, probably mimicking the (old?) way of distributing both Release and Release.gpg. So the clearsigned InRelease file is split into one cleartext file (similar to the Release file) and one OpenPGP signature file (similar to the Release.gpg file). But why didn’t the cleartext variant of the InRelease file hash to the same value as the hash of the Release file? Sadly they differ by the final newline.
Having solved this technicality, wrapping the pieces up was easy, and I came up with a project apt-canary that provides a script apt-canary-gpgv that verify the local apt release files against something I call a “apt canary witness” file stored at a URL somewhere.
I’m now running apt-canary on my Trisquel aramo laptop, a Trisquel nabia server, and Talos II ppc64el Debian machine. This means I have solved the per-IP substitution worries (or at least made them less likely to occur, having to send the same malicious release files to both GitLab and my system), and allow me to have an audit log of all release files that I actually use for installing and downloading packages.
What do you think? There are clearly a lot of work and improvements to be made. This is a proof-of-concept implementation of an idea, but instead of refining it until perfection and delaying feedback, I wanted to publish this to get others to think about the problems and various ways to resolve them.
Btw, I’m going to be at FOSDEM’23 this weekend, helping to manage the Security Devroom. Catch me if you want to chat about this or other things. Happy Hacking!
I use GnuPG to compute cryptographic signatures for my emails, git commits/tags, and software release artifacts (tarballs). Part of GnuPG is gpg-agent which talks to OpenSSH, which I login to remote servers and to clone git repositories. I dislike storing cryptographic keys on general-purpose machines, and have used hardware-backed OpenPGP keys since around 2006 when I got a FSFE Fellowship Card. GnuPG via gpg-agent handles this well, and the private key never leaves the hardware. The ZeitControl cards were (to my knowledge) proprietary hardware running some non-free operating system and OpenPGP implementation. By late 2012 the YubiKey NEO supported OpenPGP, and while the hardware and operating system on it was not free, at least it ran a free software OpenPGP implementation and eventually I setup my primary RSA key on it. This worked well for a couple of years, and when I in 2019 wished to migrate to a new key, the FST-01G device with open hardware running free software that supported Ed25519 had become available. I created a key and have been using the FST-01G on my main laptop since then. This little device has been working, the signature counter on it is around 14501 which means around 10 signatures/day since then!
Currently I am in the process of migrating towards a new laptop, and moving the FST-01G device between them is cumbersome, especially if I want to use both laptops in parallel. That’s why I need to setup a new hardware device to hold my OpenPGP key, which can go with my new laptop. This is a good time to re-visit alternatives. I quickly decided that I did not want to create a new key, only to import my current one to keep everything working. My requirements on the device to chose hasn’t changed since 2019, see my summary at the end of the earlier blog post. Unfortunately the FST-01G is out of stock and the newer FST-01SZ has also out of stock. While Tillitis looks promising (and I have one to play with), it does not support OpenPGP (yet). What to do? Fortunately, I found some FST-01SZ device in my drawer, and decided to use it pending a more satisfactory answer. Hopefully once I get around to generate a new OpenPGP key in a year or so, I will do a better survey of options that are available on the market then. What are your (freedom-respecting) OpenPGP hardware recommendations?
FST-01SZ circuit board
Similar to setting up the FST-01G, the FST-01SZ needs to be setup before use. I’m doing the following from Trisquel 11 but any GNU/Linux system would work. When the device is inserted at first time, some kernel messages are shown (see /var/log/syslog or use the dmesg command):
usb 3-3: new full-speed USB device number 39 using xhci_hcd
usb 3-3: New USB device found, idVendor=234b, idProduct=0004, bcdDevice= 2.00
usb 3-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 3-3: Product: Fraucheky
usb 3-3: Manufacturer: Free Software Initiative of Japan
usb 3-3: SerialNumber: FSIJ-0.0
usb-storage 3-3:1.0: USB Mass Storage device detected
scsi host1: usb-storage 3-3:1.0
scsi 1:0:0:0: Direct-Access FSIJ Fraucheky 1.0 PQ: 0 ANSI: 0
sd 1:0:0:0: Attached scsi generic sg2 type 0
sd 1:0:0:0: [sdc] 128 512-byte logical blocks: (65.5 kB/64.0 KiB)
sd 1:0:0:0: [sdc] Write Protect is off
sd 1:0:0:0: [sdc] Mode Sense: 03 00 00 00
sd 1:0:0:0: [sdc] No Caching mode page found
sd 1:0:0:0: [sdc] Assuming drive cache: write through
sdc:
sd 1:0:0:0: [sdc] Attached SCSI removable disk
Interestingly, the NeuG software installed on the device I got appears to be version 1.0.9:
jas@kaka:~$ head /media/jas/Fraucheky/README
NeuG - a true random number generator implementation
Version 1.0.9
2018-11-20
Niibe Yutaka
Free Software Initiative of Japan
What's NeuG?
============
jas@kaka:~$
I could not find version 1.0.9 published anywhere, but the device came with a SD-card that contain a copy of the source, so I uploaded it until a more canonical place is located. Putting the device in the serial mode can be done using a sudo eject /dev/sdc command which results in the following syslog output.
usb 3-3: reset full-speed USB device number 39 using xhci_hcd
usb 3-3: device firmware changed
usb 3-3: USB disconnect, device number 39
sdc: detected capacity change from 128 to 0
usb 3-3: new full-speed USB device number 40 using xhci_hcd
usb 3-3: New USB device found, idVendor=234b, idProduct=0001, bcdDevice= 2.00
usb 3-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 3-3: Product: NeuG True RNG
usb 3-3: Manufacturer: Free Software Initiative of Japan
usb 3-3: SerialNumber: FSIJ-1.0.9-42315277
cdc_acm 3-3:1.0: ttyACM0: USB ACM device
Now download Gnuk, verify its integrity and build it. You may need some additional packages installed, try apt-get install gcc-arm-none-eabi openocd python3-usb. As you can see, I’m using the stable 1.2 branch of Gnuk, currently on version 1.2.20. The ./configure parameters deserve some explanation. The kdf_do=required sets up the device to require KDF usage. The --enable-factory-reset allows me to use the command factory-reset (with admin PIN) inside gpg --card-edit to completely wipe the card. Some may consider that too dangerous, but my view is that if someone has your admin PIN it is game over anyway. The --vidpid=234b:0000 is specifies the USB VID/PID to use, and --target=FST_01SZ is critical to set the platform (you’ll may brick the device if you pick the wrong --target setting).
jas@kaka:~/src$ rm -rf gnuk neug
jas@kaka:~/src$ git clone https://gitlab.com/jas/neug.git
Cloning into 'neug'...
remote: Enumerating objects: 2034, done.
remote: Counting objects: 100% (2034/2034), done.
remote: Compressing objects: 100% (603/603), done.
remote: Total 2034 (delta 1405), reused 2013 (delta 1405), pack-reused 0
Receiving objects: 100% (2034/2034), 910.34 KiB | 3.50 MiB/s, done.
Resolving deltas: 100% (1405/1405), done.
jas@kaka:~/src$ git clone https://salsa.debian.org/gnuk-team/gnuk/gnuk.git
Cloning into 'gnuk'...
remote: Enumerating objects: 13765, done.
remote: Counting objects: 100% (959/959), done.
remote: Compressing objects: 100% (337/337), done.
remote: Total 13765 (delta 629), reused 907 (delta 599), pack-reused 12806
Receiving objects: 100% (13765/13765), 12.59 MiB | 3.05 MiB/s, done.
Resolving deltas: 100% (10077/10077), done.
jas@kaka:~/src$ cd neug
jas@kaka:~/src/neug$ git describe
release/1.0.9
jas@kaka:~/src/neug$ git tag -v `git describe`
object 5d51022a97a5b7358d0ea62bbbc00628c6cec06a
type commit
tag release/1.0.9
tagger NIIBE Yutaka <gniibe@fsij.org> 1542701768 +0900
Version 1.0.9.
gpg: Signature made Tue Nov 20 09:16:08 2018 CET
gpg: using EDDSA key 249CB3771750745D5CDD323CE267B052364F028D
gpg: issuer "gniibe@fsij.org"
gpg: Good signature from "NIIBE Yutaka <gniibe@fsij.org>" [unknown]
gpg: aka "NIIBE Yutaka <gniibe@debian.org>" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg: There is no indication that the signature belongs to the owner.
Primary key fingerprint: 249C B377 1750 745D 5CDD 323C E267 B052 364F 028D
jas@kaka:~/src/neug$ cd ../gnuk/
jas@kaka:~/src/gnuk$ git checkout STABLE-BRANCH-1-2
Branch 'STABLE-BRANCH-1-2' set up to track remote branch 'STABLE-BRANCH-1-2' from 'origin'.
Switched to a new branch 'STABLE-BRANCH-1-2'
jas@kaka:~/src/gnuk$ git describe
release/1.2.20
jas@kaka:~/src/gnuk$ git tag -v `git describe`
object 9d3c08bd2beb73ce942b016d4328f0a596096c02
type commit
tag release/1.2.20
tagger NIIBE Yutaka <gniibe@fsij.org> 1650594032 +0900
Gnuk: Version 1.2.20
gpg: Signature made Fri Apr 22 04:20:32 2022 CEST
gpg: using EDDSA key 249CB3771750745D5CDD323CE267B052364F028D
gpg: Good signature from "NIIBE Yutaka <gniibe@fsij.org>" [unknown]
gpg: aka "NIIBE Yutaka <gniibe@debian.org>" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg: There is no indication that the signature belongs to the owner.
Primary key fingerprint: 249C B377 1750 745D 5CDD 323C E267 B052 364F 028D
jas@kaka:~/src/gnuk/src$ git submodule update --init
Submodule 'chopstx' (https://salsa.debian.org/gnuk-team/chopstx/chopstx.git) registered for path '../chopstx'
Cloning into '/home/jas/src/gnuk/chopstx'...
Submodule path '../chopstx': checked out 'e12a7e0bb3f004c7bca41cfdb24c8b66daf3db89'
jas@kaka:~/src/gnuk$ cd chopstx
jas@kaka:~/src/gnuk/chopstx$ git describe
release/1.21
jas@kaka:~/src/gnuk/chopstx$ git tag -v `git describe`
object e12a7e0bb3f004c7bca41cfdb24c8b66daf3db89
type commit
tag release/1.21
tagger NIIBE Yutaka <gniibe@fsij.org> 1650593697 +0900
Chopstx: Version 1.21
gpg: Signature made Fri Apr 22 04:14:57 2022 CEST
gpg: using EDDSA key 249CB3771750745D5CDD323CE267B052364F028D
gpg: Good signature from "NIIBE Yutaka <gniibe@fsij.org>" [unknown]
gpg: aka "NIIBE Yutaka <gniibe@debian.org>" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg: There is no indication that the signature belongs to the owner.
Primary key fingerprint: 249C B377 1750 745D 5CDD 323C E267 B052 364F 028D
jas@kaka:~/src/gnuk/chopstx$ cd ../src
jas@kaka:~/src/gnuk/src$ kdf_do=required ./configure --enable-factory-reset --vidpid=234b:0000 --target=FST_01SZ
Header file is: board-fst-01sz.h
Debug option disabled
Configured for bare system (no-DFU)
PIN pad option disabled
CERT.3 Data Object is NOT supported
Card insert/removal by HID device is NOT supported
Life cycle management is supported
Acknowledge button is supported
KDF DO is required before key import/generation
jas@kaka:~/src/gnuk/src$ make | less
jas@kaka:~/src/gnuk/src$ cd ../regnual/
jas@kaka:~/src/gnuk/regnual$ make | less
jas@kaka:~/src/gnuk/regnual$ cd ../../
jas@kaka:~/src$ sudo python3 neug/tool/neug_upgrade.py -f gnuk/regnual/regnual.bin gnuk/src/build/gnuk.bin
gnuk/regnual/regnual.bin: 4608
gnuk/src/build/gnuk.bin: 109568
CRC32: b93ca829
Device:
Configuration: 1
Interface: 1
20000e00:20005000
Downloading flash upgrade program...
start 20000e00
end 20002000
# 20002000: 32 : 4
Run flash upgrade program...
Wait 1 second...
Wait 1 second...
Device:
08001000:08020000
Downloading the program
start 08001000
end 0801ac00
jas@kaka:~/src$
The kernel log will contain the following, and the card is ready to use as an OpenPGP card. You may unplug it and re-insert it as you wish.
usb 3-3: reset full-speed USB device number 41 using xhci_hcd
usb 3-3: device firmware changed
usb 3-3: USB disconnect, device number 41
usb 3-3: new full-speed USB device number 42 using xhci_hcd
usb 3-3: New USB device found, idVendor=234b, idProduct=0000, bcdDevice= 2.00
usb 3-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 3-3: Product: Gnuk Token
usb 3-3: Manufacturer: Free Software Initiative of Japan
usb 3-3: SerialNumber: FSIJ-1.2.20-42315277
Setting up the card is the next step, and there are many tutorials around for this, eventually I settled with the following sequence. Let’s start with setting the admin PIN. First make sure that pcscd nor scdaemon is running, which is good hygien since those processes cache some information and with a stale connection this easily leads to confusion. Cache invalidation… sigh.
jas@kaka:~$ gpg-connect-agent "SCD KILLSCD" "SCD BYE" /bye
jas@kaka:~$ ps auxww|grep -e pcsc -e scd
jas 30221 0.0 0.0 3468 1692 pts/3 R+ 11:49 0:00 grep --color=auto -e pcsc -e scd
jas@kaka:~$ gpg --card-edit
Reader ...........: 234B:0000:FSIJ-1.2.20-42315277:0
Application ID ...: D276000124010200FFFE423152770000
Application type .: OpenPGP
Version ..........: 2.0
Manufacturer .....: unmanaged S/N range
Serial number ....: 42315277
Name of cardholder: [not set]
Language prefs ...: [not set]
Salutation .......:
URL of public key : [not set]
Login data .......: [not set]
Signature PIN ....: forced
Key attributes ...: rsa2048 rsa2048 rsa2048
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 3 3
Signature counter : 0
KDF setting ......: off
Signature key ....: [none]
Encryption key....: [none]
Authentication key: [none]
General key info..: [none]
gpg/card> admin
Admin commands are allowed
gpg/card> kdf-setup
gpg/card> passwd
gpg: OpenPGP card no. D276000124010200FFFE423152770000 detected
1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit
Your selection? 3
PIN changed.
1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit
Your selection?
Now it would be natural to setup the PIN and reset code. However the Gnuk software is configured to not allow this until the keys are imported. You would get the following somewhat cryptical error messages if you try. This took me a while to understand, since this is device-specific, and some other OpenPGP implementations allows you to configure a PIN and reset code before key import.
Your selection? 4
Error setting the Reset Code: Card error
1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit
Your selection? 1
Error changing the PIN: Conditions of use not satisfied
1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit
Your selection? q
Continue to configure the card and make it ready for key import. Some settings deserve comments. The lang field may be used to setup the language, but I have rarely seen it use, and I set it to ‘sv‘ (Swedish) mostly to be able to experiment if any software adhears to it. The URL is important to point to somewhere where your public key is stored, the fetch command of gpg --card-edit downloads it and sets up GnuPG with it when you are on a clean new laptop. The forcesig command changes the default so that a PIN code is not required for every digital signature operation, remember that I averaged 10 signatures per day for the past 2-3 years? Think of the wasted energy typing those PIN codes every time! Changing the cryptographic key type is required when I import 25519-based keys.
gpg/card> name
Cardholder's surname: Josefsson
Cardholder's given name: Simon
gpg/card> lang
Language preferences: sv
gpg/card> sex
Salutation (M = Mr., F = Ms., or space): m
gpg/card> login
Login data (account name): jas
gpg/card> url
URL to retrieve public key: https://josefsson.org/key-20190320.txt
gpg/card> forcesig
gpg/card> key-attr
Changing card key attribute for: Signature key
Please select what kind of key you want:
(1) RSA
(2) ECC
Your selection? 2
Please select which elliptic curve you want:
(1) Curve 25519
(4) NIST P-384
Your selection? 1
The card will now be re-configured to generate a key of type: ed25519
Note: There is no guarantee that the card supports the requested size.
If the key generation does not succeed, please check the
documentation of your card to see what sizes are allowed.
Changing card key attribute for: Encryption key
Please select what kind of key you want:
(1) RSA
(2) ECC
Your selection? 2
Please select which elliptic curve you want:
(1) Curve 25519
(4) NIST P-384
Your selection? 1
The card will now be re-configured to generate a key of type: cv25519
Changing card key attribute for: Authentication key
Please select what kind of key you want:
(1) RSA
(2) ECC
Your selection? 2
Please select which elliptic curve you want:
(1) Curve 25519
(4) NIST P-384
Your selection? 1
The card will now be re-configured to generate a key of type: ed25519
gpg/card>
Reader ...........: 234B:0000:FSIJ-1.2.20-42315277:0
Application ID ...: D276000124010200FFFE423152770000
Application type .: OpenPGP
Version ..........: 2.0
Manufacturer .....: unmanaged S/N range
Serial number ....: 42315277
Name of cardholder: Simon Josefsson
Language prefs ...: sv
Salutation .......: Mr.
URL of public key : https://josefsson.org/key-20190320.txt
Login data .......: jas
Signature PIN ....: not forced
Key attributes ...: ed25519 cv25519 ed25519
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 3 3
Signature counter : 0
KDF setting ......: on
Signature key ....: [none]
Encryption key....: [none]
Authentication key: [none]
General key info..: [none]
gpg/card>
The device is now ready for key import! Bring out your offline laptop and boot it and use the keytocard command on the subkeys to import them. This assumes you saved a copy of the GnuPG home directory after generating the master and subkeys before, which I did in my own previous tutorial when I generated the keys. This may be a bit unusual, and there are simpler ways to do this (e.g., import a copy of the secret keys into a fresh GnuPG home directory).
$ cp -a gnupghome-backup-mastersubkeys gnupghome-import-fst01sz-42315277-2022-12-24
$ ps auxww|grep -e pcsc -e scd
$ gpg --homedir $PWD/gnupghome-import-fst01sz-42315277-2022-12-24 --edit-key B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE
...
Secret key is available.
gpg: checking the trustdb
gpg: marginals needed: 3 completes needed: 1 trust model: pgp
gpg: depth: 0 valid: 1 signed: 0 trust: 0-, 0q, 0n, 0m, 0f, 1u
sec ed25519/D73CF638C53C06BE
created: 2019-03-20 expired: 2019-10-22 usage: SC
trust: ultimate validity: expired
ssb cv25519/02923D7EE76EBD60
created: 2019-03-20 expired: 2019-10-22 usage: E
ssb ed25519/80260EE8A9B92B2B
created: 2019-03-20 expired: 2019-10-22 usage: A
ssb ed25519/51722B08FE4745A2
created: 2019-03-20 expired: 2019-10-22 usage: S
[ expired] (1). Simon Josefsson <simon@josefsson.org>
gpg> key 1
sec ed25519/D73CF638C53C06BE
created: 2019-03-20 expired: 2019-10-22 usage: SC
trust: ultimate validity: expired
ssb* cv25519/02923D7EE76EBD60
created: 2019-03-20 expired: 2019-10-22 usage: E
ssb ed25519/80260EE8A9B92B2B
created: 2019-03-20 expired: 2019-10-22 usage: A
ssb ed25519/51722B08FE4745A2
created: 2019-03-20 expired: 2019-10-22 usage: S
[ expired] (1). Simon Josefsson <simon@josefsson.org>
gpg> keytocard
Please select where to store the key:
(2) Encryption key
Your selection? 2
sec ed25519/D73CF638C53C06BE
created: 2019-03-20 expired: 2019-10-22 usage: SC
trust: ultimate validity: expired
ssb* cv25519/02923D7EE76EBD60
created: 2019-03-20 expired: 2019-10-22 usage: E
ssb ed25519/80260EE8A9B92B2B
created: 2019-03-20 expired: 2019-10-22 usage: A
ssb ed25519/51722B08FE4745A2
created: 2019-03-20 expired: 2019-10-22 usage: S
[ expired] (1). Simon Josefsson <simon@josefsson.org>
gpg> key 1
sec ed25519/D73CF638C53C06BE
created: 2019-03-20 expired: 2019-10-22 usage: SC
trust: ultimate validity: expired
ssb cv25519/02923D7EE76EBD60
created: 2019-03-20 expired: 2019-10-22 usage: E
ssb ed25519/80260EE8A9B92B2B
created: 2019-03-20 expired: 2019-10-22 usage: A
ssb ed25519/51722B08FE4745A2
created: 2019-03-20 expired: 2019-10-22 usage: S
[ expired] (1). Simon Josefsson <simon@josefsson.org>
gpg> key 2
sec ed25519/D73CF638C53C06BE
created: 2019-03-20 expired: 2019-10-22 usage: SC
trust: ultimate validity: expired
ssb cv25519/02923D7EE76EBD60
created: 2019-03-20 expired: 2019-10-22 usage: E
ssb* ed25519/80260EE8A9B92B2B
created: 2019-03-20 expired: 2019-10-22 usage: A
ssb ed25519/51722B08FE4745A2
created: 2019-03-20 expired: 2019-10-22 usage: S
[ expired] (1). Simon Josefsson <simon@josefsson.org>
gpg> keytocard
Please select where to store the key:
(3) Authentication key
Your selection? 3
sec ed25519/D73CF638C53C06BE
created: 2019-03-20 expired: 2019-10-22 usage: SC
trust: ultimate validity: expired
ssb cv25519/02923D7EE76EBD60
created: 2019-03-20 expired: 2019-10-22 usage: E
ssb* ed25519/80260EE8A9B92B2B
created: 2019-03-20 expired: 2019-10-22 usage: A
ssb ed25519/51722B08FE4745A2
created: 2019-03-20 expired: 2019-10-22 usage: S
[ expired] (1). Simon Josefsson <simon@josefsson.org>
gpg> key 2
sec ed25519/D73CF638C53C06BE
created: 2019-03-20 expired: 2019-10-22 usage: SC
trust: ultimate validity: expired
ssb cv25519/02923D7EE76EBD60
created: 2019-03-20 expired: 2019-10-22 usage: E
ssb ed25519/80260EE8A9B92B2B
created: 2019-03-20 expired: 2019-10-22 usage: A
ssb ed25519/51722B08FE4745A2
created: 2019-03-20 expired: 2019-10-22 usage: S
[ expired] (1). Simon Josefsson <simon@josefsson.org>
gpg> key 3
sec ed25519/D73CF638C53C06BE
created: 2019-03-20 expired: 2019-10-22 usage: SC
trust: ultimate validity: expired
ssb cv25519/02923D7EE76EBD60
created: 2019-03-20 expired: 2019-10-22 usage: E
ssb ed25519/80260EE8A9B92B2B
created: 2019-03-20 expired: 2019-10-22 usage: A
ssb* ed25519/51722B08FE4745A2
created: 2019-03-20 expired: 2019-10-22 usage: S
[ expired] (1). Simon Josefsson <simon@josefsson.org>
gpg> keytocard
Please select where to store the key:
(1) Signature key
(3) Authentication key
Your selection? 1
sec ed25519/D73CF638C53C06BE
created: 2019-03-20 expired: 2019-10-22 usage: SC
trust: ultimate validity: expired
ssb cv25519/02923D7EE76EBD60
created: 2019-03-20 expired: 2019-10-22 usage: E
ssb ed25519/80260EE8A9B92B2B
created: 2019-03-20 expired: 2019-10-22 usage: A
ssb* ed25519/51722B08FE4745A2
created: 2019-03-20 expired: 2019-10-22 usage: S
[ expired] (1). Simon Josefsson <simon@josefsson.org>
gpg> quit
Save changes? (y/N) y
$
Now insert it into your daily laptop and have GnuPG and learn about the new private keys and forget about any earlier locally available card bindings — this usually manifests itself by GnuPG asking you to insert a OpenPGP card with another serial number. Earlier I did rm -rf ~/.gnupg/private-keys-v1.d/ but the scd serialno followed by learn --force is nicer. I also sets up trust setting for my own key.
jas@kaka:~$ gpg-connect-agent "scd serialno" "learn --force" /bye
...
jas@kaka:~$ echo "B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE:6:" | gpg --import-ownertrust
jas@kaka:~$ gpg --card-status
Reader ...........: 234B:0000:FSIJ-1.2.20-42315277:0
Application ID ...: D276000124010200FFFE423152770000
Application type .: OpenPGP
Version ..........: 2.0
Manufacturer .....: unmanaged S/N range
Serial number ....: 42315277
Name of cardholder: Simon Josefsson
Language prefs ...: sv
Salutation .......: Mr.
URL of public key : https://josefsson.org/key-20190320.txt
Login data .......: jas
Signature PIN ....: not forced
Key attributes ...: ed25519 cv25519 ed25519
Max. PIN lengths .: 127 127 127
PIN retry counter : 5 5 5
Signature counter : 3
KDF setting ......: on
Signature key ....: A3CC 9C87 0B9D 310A BAD4 CF2F 5172 2B08 FE47 45A2
created ....: 2019-03-20 23:40:49
Encryption key....: A9EC 8F4D 7F1E 50ED 3DEF 49A9 0292 3D7E E76E BD60
created ....: 2019-03-20 23:40:26
Authentication key: CA7E 3716 4342 DF31 33DF 3497 8026 0EE8 A9B9 2B2B
created ....: 2019-03-20 23:40:37
General key info..: sub ed25519/51722B08FE4745A2 2019-03-20 Simon Josefsson <simon@josefsson.org>
sec# ed25519/D73CF638C53C06BE created: 2019-03-20 expires: 2023-09-19
ssb> ed25519/80260EE8A9B92B2B created: 2019-03-20 expires: 2023-09-19
card-no: FFFE 42315277
ssb> ed25519/51722B08FE4745A2 created: 2019-03-20 expires: 2023-09-19
card-no: FFFE 42315277
ssb> cv25519/02923D7EE76EBD60 created: 2019-03-20 expires: 2023-09-19
card-no: FFFE 42315277
jas@kaka:~$
Verify that you can digitally sign and authenticate using the key and you are done!
jas@kaka:~$ echo foo|gpg -a --sign|gpg --verify
gpg: Signature made Sat Dec 24 13:49:59 2022 CET
gpg: using EDDSA key A3CC9C870B9D310ABAD4CF2F51722B08FE4745A2
gpg: Good signature from "Simon Josefsson <simon@josefsson.org>" [ultimate]
jas@kaka:~$ ssh-add -L
ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAILzCFcHHrKzVSPDDarZPYqn89H5TPaxwcORgRg+4DagE cardno:FFFE42315277
jas@kaka:~$
So time to relax and celebrate christmas? Hold on… not so fast! Astute readers will have noticed that the output said ‘PIN retry counter: 5 5 5‘. That’s not the default PIN retry counter for Gnuk! How did that happen? Indeed, good catch and great question, my dear reader. I wanted to include how you can modify the Gnuk source code, re-build it and re-flash the Gnuk as well. This method is different than flashing Gnuk onto a device that is running NeuG so the commands I used to flash the firmware in the start of this blog post no longer works in a device running Gnuk. Fortunately modern Gnuk supports updating firmware by specifying the Admin PIN code only, and provides a simple script to achieve this as well. The PIN retry counter setting is hard coded in the openpgp-do.c file, and we run a a perl command to modify the file, rebuild Gnuk and upgrade the FST-01SZ. This of course wipes all your settings, so you will have the opportunity to practice all the commands earlier in this post once again!
jas@kaka:~/src/gnuk/src$ perl -pi -e 's/PASSWORD_ERRORS_MAX 3/PASSWORD_ERRORS_MAX 5/' openpgp-do.c
jas@kaka:~/src/gnuk/src$ make | less
jas@kaka:~/src/gnuk/src$ cd ../tool/
jas@kaka:~/src/gnuk/tool$ ./upgrade_by_passwd.py
Admin password:
Device:
Configuration: 1
Interface: 0
../regnual/regnual.bin: 4608
../src/build/gnuk.bin: 110592
CRC32: b93ca829
Device:
Configuration: 1
Interface: 0
20002a00:20005000
Downloading flash upgrade program...
start 20002a00
end 20003c00
Run flash upgrade program...
Waiting for device to appear:
Wait 1 second...
Wait 1 second...
Device:
08001000:08020000
Downloading the program
start 08001000
end 0801b000
Protecting device
Finish flashing
Resetting device
Update procedure finished
jas@kaka:~/src/gnuk/tool$
Now finally, I wish you all a Merry Christmas and Happy Hacking!
I’m about to migrate to a new laptop, having done a brief pre-purchase review of options on Fosstodon and reaching a decision to buy the NovaCustom NV41. Given the rapid launch and decline of Mastodon instances, I thought I’d better summarize my process and conclusion on my self-hosted blog until the fediverse self-hosting situation improves.
Since 2010 my main portable computing device has been the Lenovo X201 that replaced the Dell Precision M65 that I bought in 2006. I have been incredibly happy with the X201, even to the point that in 2015 when I wanted to find a replacement, I couldn’t settle on a decision and eventually realized I couldn’t articulate what was wrong with the X201 and decided to just buy another X201 second-hand for my second office. There is still no deal-breaker with the X201, and I’m doing most of my computing on it including writing this post. However, today I can better articulate what is lacking with the X201 that I desire, and the state of the available options on the market has improved since my last attempt in 2015.
Briefly, my desired properties are:
Portable – weight under 1.5kg
Screen size 9-14″
ISO keyboard layout, preferably Swedish layout
Mouse trackpad, WiFi, USB and external screen connector
Decent market availability: I should be able to purchase it from Sweden and have consumer protection, warranty, and some hope of getting service parts for the device
Manufactured and sold by a vendor that is supportive of free software
Preferably RJ45 connector (for data center visits)
My workload for the machine is Emacs, Firefox, Nextcloud client, GNOME, Evolution (mail & calendar), LibreOffice Calc/Writer, compiling software and some podman/qemu for testing. I have used Debian as the main operating system for the entire life of this laptop, but have experimented with PureOS recently. My current X201 is useful enough for this, although support for 4K displays and a faster machine wouldn’t hurt.
Based on my experience in 2015 that led me to make no decision, I changed perspective. This is a judgement call and I will not be able to fulfil all criteria. I will have to decide on a balance and the final choice will include elements that I really dislike, but still it will hopefully be better than nothing. The conflict for me mainly center around these parts:
Non-free BIOS. This is software that runs on the main CPU and has full control of everything. I want this to run free software as much as possible. Coreboot is the main project in this area, although I prefer the more freedom-oriented Libreboot.
Proprietary and software-upgradeable parts of the main CPU. This includes CPU microcode that is not distributed as free software. The Intel Management Engine (AMD and other CPU vendors has similar technology) falls into this category as well, and is problematic because it is an entire non-free operating system running within the CPU, with many security and freedom problems. This aspect is explored in the Libreboot FAQ further. Even if these parts can be disabled (Intel ME) or not utilized (CPU microcode), I believe the mere presence of these components in the design of the CPU is a problem, and I would prefer a CPU without these properties.
Non-free software in other microprocessors in the laptop. Ultimately, I tend agree with the FSF’s “secondary processor” argument but when it is possible to chose between a secondary processor that runs free software and one that runs proprietary software, I would prefer as many secondary processors as possible to run free software. The libreboot binary blob reduction policy describes a move towards stronger requirements.
Non-free firmware that has to be loaded during runtime into CPU or secondary processors. Using Linux-libre solves this but can cause some hardware to be unusable.
WiFi, BlueTooth and physical network interface (NIC/RJ45). This is the most notable example of secondary processor problem with running non-free software and requiring non-free firmware. Sometimes these may even require non-free drivers, although in recent years this has usually been reduced into requiring non-free firmware.
A simple choice for me would be to buy one of the FSF RYF certified laptops. Right now that list only contains the 10+ year old Lenovo series, and I actually already have a X200 with libreboot that I bought earlier for comparison. The reason the X200 didn’t work out as a replacement for me was the lack of a mouse trackpad, concerns about non-free EC firmware, Intel ME uncertainty (is it really neutralized?) and non-free CPU microcode (what are the bugs that it fixes?), but primarily that for some reason that I can’t fully articulate it feels weird to use a laptop manufactured by Lenovo but modified by third parties to be useful. I believe in market forces to pressure manufacturers into Doing The Right Thing, and feel that there is no incentive for Lenovo to use libreboot in the future when this market niche is already fulfilled by re-sellers modifying Lenovo laptops. So I’d be happier buying a laptop from someone who is natively supportive of they way I’m computing. I’m sure this aspect could be discussed a lot more, and maybe I’ll come back to do that, and could even reconsider my thinking (the right-to-repair argument is compelling). I will definitely continue to monitor the list of RYF-certified laptops to see if future entries are more suitable options for me.
Eventually I decided to buy the NovaCustom NV41 laptop, and it arrived quickly and I’m in the process of setting it up. I hope to write a separate blog about it next.
The Guile bindings for GnuTLS has been part of GnuTLS since spring 2007 when Ludovic Courtès contributed it after some initial discussion. I have been looking into getting back to do GnuTLS coding, and during a recent GnuTLS meeting one topic was Guile bindings. It seemed like a fairly self-contained project to pick up on. It is interesting to re-read the old thread when this work was included: some of the concerns brought up there now have track record to be evaluated on. My opinion that the cost of introducing a new project per language binding today is smaller than the cost of maintaining language bindings as part of the core project. I believe the cost/benefit ratio has changed during the past 15 years: introducing a new project used to come with a significant cost but this is no longer the case, as tooling and processes for packaging have improved. I have had similar experience with Java, C# and Emacs Lisp bindings for GNU Libidn as well, where maintaining them centralized slow down the pace of updates. Andreas Metzler pointed to a similar conclusion reached by Russ Allbery.
There are many ways to separate a project into two projects; just copying the files into a new git repository would have been the simplest and was my original plan. However Ludo’ mentioned git-filter-branch in an email, and the idea of keeping all git history for some of the relevant files seemed worth pursuing to me. I quickly found git-filter-repo which appears to be the recommend approach, and experimenting with it I found a way to filter out the GnuTLS repo into a small git repository that Guile-GnuTLS could be based on. The commands I used were the following, if you want to reproduce things.
I debated with myself back and forth whether to include some files that would be named the same in the new repository but would share little to no similar lines, for example configure.ac, Makefile.am not to mention README and NEWS. Initially I thought it would be nice to preserve the history for all lines that went into the new project, but this is a subjective judgement call. What brought me over to a more minimal approach was that the contributor history and attribution would be quite strange for the new repository: Should Guile-GnuTLS attribute the work of the thousands of commits to configure.ac which had nothing to do with Guile? Should the people who wrote that be mentioned as contributor of Guile-GnuTLS? I think not.
The next step was to get a reasonable GitLab CI/CD pipeline up, to make sure the project builds on some free GNU/Linux distributions like Trisquel and PureOS as well as the usual non-free distributions like Debian and Fedora to have coverage of dpkg and rpm based distributions. I included builds on Alpine and ArchLinux as well, because they tend to trigger other portability issues. I wish there were GNU Guix docker images available for easy testing on that platform as well. The GitLab CI/CD rules for a project like this are fairly simple.
To get things out of the door, I tagged the result as v3.7.9 and published a GitLab release page for Guile-GnuTLS that includes OpenPGP-signed source tarballs manually uploaded built on my laptop. The URLs for these tarballs are not very pleasant to work with, and discovering new releases automatically appears unreliable, but I don’t know of a better approach.
To finish this project, I have proposed a GnuTLS merge request to remove all Guile-related parts from the GnuTLS core.
Doing some GnuTLS-related work again felt nice, it was quite some time ago so thank you for giving me this opportunity. Thoughts or comments? Happy hacking!
To protect web resources with Kerberos you may use Apache HTTPD with mod_auth_gssapi — however, all web scripts (e.g., PHP) run under Apache will have access to the Kerberos long-term symmetric secret credential (keytab). If someone can get it, they can impersonate your server, which is bad.
This should give you a working and running web server. Verify it is operational under the proper hostname, I’ll use foo.sjd.se in this writeup.
root@foo:~# curl --head http://foo.sjd.se/ HTTP/1.1 200 OK …
The next step is to create a keytab containing the Kerberos V5 secrets for your host, the exact steps depends on your environment (usually kadmin ktadd or ipa-getkeytab), but use the string “HTTP/foo.sjd.se” and then confirm using something like the following.
The file should be owned by root and not be in the default /etc/krb5.keytab location, so Apache’s libapache2-mod-auth-gssapi will have to use gssproxy to use it.
Then configure gssproxy to find the credential and use it with Apache.
You should see something like this in the log file:
Sep 18 07:03:15 foo gssproxy[4076]: [2022/09/18 05:03:15]: Exiting after receiving a signal Sep 18 07:03:15 foo systemd[1]: Stopping GSSAPI Proxy Daemon… Sep 18 07:03:15 foo systemd[1]: gssproxy.service: Deactivated successfully. Sep 18 07:03:15 foo systemd[1]: Stopped GSSAPI Proxy Daemon. Sep 18 07:03:15 foo gssproxy[4092]: [2022/09/18 05:03:15]: Debug Enabled (level: 1) Sep 18 07:03:15 foo systemd[1]: Starting GSSAPI Proxy Daemon… Sep 18 07:03:15 foo gssproxy[4093]: [2022/09/18 05:03:15]: Kernel doesn't support GSS-Proxy (can't open /proc/net/rpc/use-gss-proxy: 2 (No such file or directory)) Sep 18 07:03:15 foo gssproxy[4093]: [2022/09/18 05:03:15]: Problem with kernel communication! NFS server will not work Sep 18 07:03:15 foo systemd[1]: Started GSSAPI Proxy Daemon. Sep 18 07:03:15 foo gssproxy[4093]: [2022/09/18 05:03:15]: Initialization complete.
The NFS-related errors is due to a default gssproxy configuration file, it is harmless and if you don’t use NFS with GSS-API you can silence it like this:
To instruct Apache — or actually, the MIT Kerberos V5 GSS-API library used by mod_auth_gssap loaded by Apache — to use gssproxy instead of using /etc/krb5.keytab as usual, Apache needs to be started in an environment that has GSS_USE_PROXY=1 set. The background is covered by the gssproxy-mech(8) man page and explained by the gssproxy README.
When systemd is used the following can be used to set the environment variable, note the final command to reload systemd.
Enable the configuration and restart Apache — the suggested use of reload is not sufficient, because then it won’t be restarted with the newly introduced GSS_USE_PROXY variable. This just applies to the first time, after the first restart you may use reload again.
root@foo:~# a2enconf private Enabling conf private. To activate the new configuration, you need to run: systemctl reload apache2 root@foo:~# systemctl restart apache2
When you have debug messages enabled, the log may look like this:
To verify that the server is working properly you may acquire tickets locally and then use curl to retrieve the GSS-API protected resource. The "--negotiate" enables SPNEGO and "--user :" asks curl to use username from the environment.
root@foo:~# klist
Ticket cache: FILE:/tmp/krb5cc_0
Default principal: jas@GSSPROXY.EXAMPLE.ORG
Valid starting Expires Service principal
09/18/22 07:40:37 09/19/22 07:40:37 krbtgt/GSSPROXY.EXAMPLE.ORG@GSSPROXY.EXAMPLE.ORG
root@foo:~# curl --negotiate --user : http://foo.sjd.se/private
OK
root@foo:~#
