Search Results: "tach"

28 September 2017

Ricardo Mones: Long time no post

Seems the breakage of my desktop computer more than 3 months ago did also caused also a hiatus on my online publishing activities... it was not really intended, it happened I was just busy with other things _ .

With a broken computer being able to build software on the laptop became a priority. Around September 2016 or so the good'n'old black MacBook decided to stop working. I didn't really need a replacement by that time, but never liked to have just a single working system, and in October just found an offer which I could not resist and bought a ThinkPad X260. It helped to build my final project (it was faster than the desktop), but lacking time for FOSS hadn't used it for much more.

Setting up the laptop for software (Debian packages and Claws Mail, mainly) was somewhat easy. Finding a replacement for the broken desktop was a bit more difficult. I considered a lot of configurations and prices, from those new Ryzen to just buying the same components (pretty difficult now because they're discontinued). In the end, I decided to spend the minimum and make good use of everything else still working (memory, discs and wireless card), so I finally got an AMD A10-7860K on top of an Asus A88M-PLUS. This board has more SATA ports, so I added an unused SSD, remains of a broken laptop, to install the new system Debian Stretch, of course while keeping the existing software RAID partitions of the spinning drives.


The last thing distracting from the usual routine was replacing the car. Our child is growing as expected and the Fiesta was starting to appear small and uncomfortable, specially for long distance travel. We went for an hybrid model, with a high capacity boot. Given our budget, we only found 3 models below the limit: Kia Niro, Hyundai Ioniq and Toyota Auris TS. The color was decided by the kid (after forbidding black), and this was the winner...

In the middle of all of this we also took some vacation to travel to the south of Galicia, mostly around Vigo area, but also visiting Oporto and other nice places.

18 September 2017

Carl Chenet: The Github threat

Many voices arise now and then against risks linked to the Github use by Free Software projects. Yet the infatuation for the collaborative forge of the Octocat Californian start-ups doesn t seem to fade away.

These recent years, Github and its services take an important role in software engineering as they are seen as easy to use, efficient for a daily workload with interesting functions in enterprise collaborative workflow or amid a Free Software project. What are the arguments against using its services and are they valid? We will list them first, then we ll examine their validity.

1. Critical points

1.1 Centralization

The Github application belongs to a single entity, Github Inc, a US company which manage it alone. So, a unique company under US legislation manages the access to most of Free Software application code sources, which may be a problem with groups using it when a code source is no longer available, for political or technical reason.

The Octocat, the Github mascot

This centralization leads to another trouble: as it obtained critical mass, it becomes more and more difficult not having a Github account. People who don t use Github, by choice or not, are becoming a silent minority. It is now fashionable to use Github, and not doing so is seen as out of date . The same phenomenon is a classic, and even the norm, for proprietary social networks (Facebook, Twitter, Instagram).

1.2 A Proprietary Software

When you interact with Github, you are using a proprietary software, with no access to its source code and which may not work the way you think it is. It is a problem at different levels. First, ideologically, but foremost in practice. In the Github case, we send them code we can control outside of their interface. We also send them personal information (profile, Github interactions). And mostly, Github forces any project which goes through the US platform to use a crucial proprietary tools: its bug tracking system.

Windows, the epitome of proprietary software, even if others took the same path

1.3 The Uniformization

Working with Github interface seems easy and intuitive to most. Lots of companies now use it as a source repository, and many developers leaving a company find the same Github working environment in the next one. This pervasive presence of Github in free software development environment is a part of the uniformization of said developers working space.

Uniforms always bring Army in my mind, here the Clone army

2 Critical points cross-examination

2.1 Regarding the centralization

2.1.1 Service availability rate

As said above, nowadays, Github is the main repository of Free Software source code. As such it is a favorite target for cyberattacks. DDOS hit it in March and August 2015. On December 15, 2015, an outage led to the inaccessibility of 5% of the repositories. The same occurred on November 15. And these are only the incident reported by Github itself. One can imagine that the mean outage rate of the platform is underestimated.

2.1.2 Chain reaction could block Free Software development

Today many dependency maintenance tools, as npm for javascript, Bundler for Ruby or even pip for Python can access an application source code directly from Github. Free Software projects getting more and more linked and codependents, if one component is down, all the developing process stop.

One of the best examples is the npmgate. Any company could legally demand that Github take down some source code from its repository, which could create a chain reaction and blocking the development of many Free Software projects, as suffered the Node.js community from the decisions of Npm, Inc, the company managing npm.

2.2 A historical precedent: SourceForge

Github didn t appear out of the blue. In his time, its predecessor, SourceForge, was also extremely popular.

Heavily centralized, based on strong interaction with the community, SourceForge is now seen as an aging SAAS (Software As A Service) and sees most of its customers fleeing to Github. Which creates lots of hurdles for those who stayed. The Gimp project suffered from spams and terrible advertising, which led to the departure of the VLC project, then from installers corrupted with adwares instead of the official Gimp installer for Windows. And finally, the Project Gimp s SourceForge account was hacked by SourceForge team itself!

These are very recent examples of what can do a commercial entity when it is under its stakeholders pressure. It is vital to really understand what it means to trust them with data and exchange centralization, where it could have tremendous repercussion on the day-to-day life and the habits of the Free Software and open source community.

2.3. Regarding proprietary software

2.3.1 One community, several opinions on proprietary software

Mostly based on ideology, this point deals with the definition every member of the community gives to Free Software and open source. Mostly about one thing: is it viral or not? Or GPL vs MIT/BSD.

Those on the side of the viral Free Software will have trouble to use a proprietary software as this last one shouldn t even exist. It must be assimilated, to quote Star Trek, as it is a connected black box, endangering privacy, corrupting for profit our uses and restrain our freedom to use as we re pleased what we own, etc.

Those on the side of complete freedom have no qualms using proprietary software as their very existence is a consequence of freedom without restriction. They even agree that code they developed may be a part of proprietary software, which is quite a common occurrence. This part of the Free Software community has no qualm using Github, which is well within their ideology parameters. Just take a look at the Janson amphitheater during Fosdem and check how many Apple laptops running on macOS are around.

FreeBSD, the main BSD project under the BSD license

2.3.2 Data loss and data restrictions linked to proprietary software use

Even without ideological consideration, and just focusing on Github infrastructure, the bug tracking system is a major problem by itself.

Bug report builds the memory of Free Software projects. It is the entrance point for new contributors, the place to find bug reporting, requests for new functions, etc. The project history can t be limited only to the code. It s very common to find bug reports when you copy and paste an error message in a search engine. Not their historical importance is precious for the project itself, but also for its present and future users.

Github gives the ability to extract bug reports through its API. What would happen if Github is down or if the platform doesn t support this feature anymore? In my opinion, not that many projects ever thought of this outcome. How could they move all the data generated by Github into a new bug tracking system? One old example now is Astrid, a TODO list bought by Yahoo a few years ago. Very popular, it grew fast until it was closed overnight, with only a few weeks for its users to extract their data. It was only a to-do list. The same situation with Github would be tremendously difficult to manage for several projects if they even have the ability to deal with it. Code would still be available and could still live somewhere else, but the project memory would be lost. A project like Debian has today more than 800,000 bug reports, which are a data treasure trove about problems solved, function requests and where the development stand on each. The developers of the Cpython project have anticipated the problem and decided not to use Github bug tracking systems.

Issues, the Github proprietary bug tracking system

Another thing we could lose if Github suddenly disappear: all the work currently done regarding the push requests (aka PRs). This Github function gives the ability to clone one project s Github repository, to modify it to fit your needs, then to offer your own modification to the original repository. The original repository s owner will then review said modification, and if he or she agrees with them will fuse them into the original repository. As such, it s one of the main advantages of Github, since it can be done easily through its graphic interface.

However reviewing all the PRs may be quite long, and most of the successful projects have several ongoing PRs. And this PRs and/or the proprietary bug tracking system are commonly used as a platform for comment and discussion between developers.

Code itself is not lost if Github is down (except one specific situation as seen below), but the peer review works materialized in the PRs and the bug tracking system is lost. Let s remember than the PR mechanism let you clone and modify projects and then generate PRs directly from its proprietary web interface without downloading a single code line on your computer. In this particular case, if Github is down, all the code and the work in progress is lost. Some also use Github as a bookmark place. They follow their favorite projects activity through the Watch function. This technological watch style of data collection would also be lost if Github is down.

Debian, one of the main Free Software projects with at least a thousand official contributors

2.4 Uniformization

The Free Software community is walking a thigh rope between normalization needed for an easier interoperability between its products and an attraction for novelty led by a strong need for differentiation from what is already there.

Github popularized the use of Git, a great tool now used through various sectors far away from its original programming field. Step by step, Git is now so prominent it s almost impossible to even think to another source control manager, even if awesome alternate solutions, unfortunately not as popular, exist as Mercurial.

A new Free Software project is now a Git repository on Github with README.md added as a quick description. All the other solutions are ostracized? How? None or very few potential contributors would notice said projects. It seems very difficult now to encourage potential contributors into learning a new source control manager AND a new forge for every project they want to contribute. Which was a basic requirement a few years ago. It s quite sad because Github, offering an original experience to its users, cut them out of a whole possibility realm. Maybe Github is one of the best web versioning control systems. But being the main one doesn t let room for a new competitor to grow. And it let Github initiate development newcomers into a narrow function set, totally unrelated to the strength of the Git tool itself.

3. Centralization, uniformization, proprietary software What s next? Laziness?

Fight against centralization is a main part of the Free Software ideology as centralization strengthens the power of those who manage it and who through it control those who are managed by it. Uniformization allergies born against main software companies and their wishes to impose a closed commercial software world was for a long time the main fuel for innovation thirst and intelligent alternative development. As we said above, part of the Free Software community was built as a reaction to proprietary software and their threat. The other part, without hoping for their disappearance, still chose a development model opposite to proprietary software, at least in the beginning, as now there s more and more bridges between the two.

The Github effect is a morbid one because of its consequences: at least centralization, uniformization, proprietary software usage as their bug tracking system. But some years ago the Dear Github buzz showed one more side effect, one I ve never thought about: laziness. For those who don t know what it is about, this letter is a complaint from several spokespersons from several Free Software projects which demand to Github team to finally implement, after years of polite asking, new functions. Since when Free Software project facing a roadblock request for clemency and don t build themselves the path they need? When Torvalds was involved in the Bitkeeper problem and the Linux kernel development team couldn t use anymore their revision control software, he developed Git. The mere fact of not being able to use one tool or functions lacking is the main motivation to seek alternative solutions and, as such, of the Free Software movement. Every Free Software community member able to code should have this reflex. You don t like what Github offers? Switch to Gitlab. You don t like it Gitlab? Improve it or make your own solution.

The Gitlab logo

Let s be crystal clear. I ve never said that every Free Software developers blocked should code his or her own alternative. We all have our own priorities, and some of us even like their beauty sleep, including me. But, to see that this open letter to Github has 1340 names attached to it, among them some spokespersons for major Free Software project showed me that need, willpower and strength to code a replacement are here. Maybe said replacement will be born from this letter, it would be the best outcome of this buzz.

In the end, Github usage is just another example of Internet usage massification. As Internet users are bound to go to massively centralized social network as Facebook or Twitter, developers are following the same path with Github. Even if a large fraction of developers realize the threat linked this centralized and proprietary organization, the whole community is following this centralization and uniformization trend. Github service is useful, free or with a reasonable price (depending on the functions you need) easy to use and up most of the time. Why would we try something else? Maybe because others are using us while we are savoring the convenience? The Free Software community seems to be quite sleepy to me.

The lion enjoying the hearth warm

About Me Carl Chenet, Free Software Indie Hacker, founder of the French-speaking Hacker News-like Journal du hacker. Follow me on social networks Translated from French by St phanie Chaptal. Original article written in 2015.

10 September 2017

intrigeri: Can you reproduce this Tails ISO image?

Thanks to a Mozilla Open Source Software award, we have been working on making the Tails ISO images build reproducibly. We have made huge progress: since a few months, ISO images built by Tails core developers and our CI system have always been identical. But we're not done yet and we need your help! Our first call for testing build reproducibility in August uncovered a number of remaining issues. We think that we have fixed them all since, and we now want to find out what other problems may prevent you from building our ISO image reproducibly. Please try to build an ISO image today, and tell us whether it matches ours! Build an ISO These instructions have been tested on Debian Stretch and testing/sid. If you're using another distribution, you may need to adjust them. If you get stuck at some point in the process, see our more detailed build documentation and don't hesitate to contact us: Setup the build environment You need a system that supports KVM, 1 GiB of free memory, and about 20 GiB of disk space.
  1. Install the build dependencies: 
    sudo apt install \
    git \
    rake \
    libvirt-daemon-system \
    dnsmasq-base \
    ebtables \
    qemu-system-x86 \
    qemu-utils \
    vagrant \
    vagrant-libvirt \
    vmdebootstrap && \
sudo systemctl restart libvirtd
  2. Ensure your user is in the relevant groups: 
    for group in kvm libvirt libvirt-qemu ; do
   sudo adduser "$(whoami)" "$group"
done
  3. Logout and log back in to apply the new group memberships.
Build Tails 3.2~alpha2 This should produce a Tails ISO image: 
git clone https://git-tails.immerda.ch/tails && \
cd tails && \
git checkout 3.2-alpha2 && \
git submodule update --init && \
rake build
Send us feedback! No matter how your build attempt turned out we are interested in your feedback. Gather system information To gather the information we need about your system, run the following commands in the terminal where you've run rake build: 
sudo apt install apt-show-versions && \
(
  for f in /etc/issue /proc/cpuinfo
  do
    echo "--- File: $ f  ---"
    cat "$ f "
    echo
  done
  for c in free locale env 'uname -a' '/usr/sbin/libvirtd --version' \
            'qemu-system-x86_64 --version' 'vagrant --version'
  do
    echo "--- Command: $ c  ---"
    eval "$ c "
    echo
  done
  echo '--- APT package versions ---'
  apt-show-versions qemu:amd64 linux-image-amd64:amd64 vagrant \
                    libvirt0:amd64
)   bzip2 > system-info.txt.bz2
Then check that the generated file doesn't contain any sensitive information you do not want to leak: 
bzless system-info.txt.bz2
Next, please follow the instructions below that match your situation! If the build failed Sorry about that. Please help us fix it by opening a ticket: If the build succeeded Compute the SHA-512 checksum of the resulting ISO image: 
sha512sum tails-amd64-3.2~alpha2.iso
Compare your checksum with ours: 
9b4e9e7ee7b2ab6a3fb959d4e4a2db346ae322f9db5409be4d5460156fa1101c23d834a1886c0ce6bef2ed6fe378a7e76f03394c7f651cc4c9a44ba608dda0bc
If the checksums match: success, congrats for reproducing Tails 3.2~alpha2! Please send an email to tails-dev@boum.org (public) or tails@boum.org (private) with the subject "Reproduction of Tails 3.2~alpha2 successful" and system-info.txt.bz2 attached. Thanks in advance! Then you can stop reading here. Else, if the checksums differ: too bad, but really it's good news as the whole point of the exercise is precisely to identify such problems :) Now you are in a great position to help improve the reproducibility of Tails ISO images by following these instructions:
  1. Install diffoscope version 83 or higher and all the packages it recommends. For example, if you're using Debian Stretch: 
    sudo apt remove diffoscope && \
echo 'deb http://ftp.debian.org/debian stretch-backports main' \
    sudo tee /etc/apt/sources.list.d/stretch-backports.list && \
sudo apt update && \
sudo apt -o APT::Install-Recommends="true" \
         install diffoscope/stretch-backports
  2. Download the official Tails 3.2~alpha2 ISO image.
  3. Compare the official Tails 3.2~alpha2 ISO image with yours: 
    diffoscope \
       --text diffoscope.txt \
       --html diffoscope.html \
       --max-report-size 262144000 \
       --max-diff-block-lines 10000 \
       --max-diff-input-lines 10000000 \
       path/to/official/tails-amd64-3.2~alpha2.iso \
       path/to/your/own/tails-amd64-3.2~alpha2.iso
bzip2 diffoscope. txt,html
  4. Send an email to tails-dev@boum.org (public) or tails@boum.org (private) with the subject "Reproduction of Tails 3.2~alpha2 failed", attaching:
    • system-info.txt.bz2;
    • the smallest file among diffoscope.txt.bz2 and diffoscope.html.bz2, except if they are larger than 100 KiB, in which case better upload the file somewhere (e.g. share.riseup.net and share the link in your email.
Thanks a lot! Credits Thanks to Ulrike & anonym who authored a draft on which this blog post is based.

Sylvain Beucler: dot-zed archive file format

TL,DR: I reverse-engineered the .zed encrypted archive format.
Following a clean-room design, I'm providing a description that can be implemented by a third-party.
Interested? :) (reference version at: https://www.beuc.net/zed/) .zed archive file format Introduction Archives with the .zed extension are conceptually similar to an encrypted .zip file. In addition to a specific format, .zed files support multiple users: files are encrypted using the archive master key, which itself is encrypted for each user and/or authentication method (password, RSA key through certificate or PKCS#11 token). Metadata such as filenames is partially encrypted. .zed archives are used as stand-alone or attached to e-mails with the help of a MS Outlook plugin. A variant, which is not covered here, can encrypt/decrypt MS Windows folders on the fly like ecryptfs. In the spirit of academic and independent research this document provides a description of the file format and encryption algorithms for this encrypted file archive. See the conventions section for conventions and acronyms used in this document. Structure overview The .zed file format is composed of several layers. Or as a diagram: 
+----------------------------------------------------------------------------------------------------+
  .zed archive (MS-CBF)                                                                               
                                                                                                      
   stream #1                         stream #2                       stream #3...                     
  +------------------------------+  +---------------------------+  +---------------------------+      
    metadata (MS-OLEPS)               encryption (AES)               encryption (AES)                 
                                      512-bytes chunks               512-bytes chunks                 
    +--------------------------+                                                                      
      obfuscation (static key)        +-----------------------+      +-----------------------+        
      +----------------------+       -  compression (zlib)     -    -  compression (zlib)     -       
       _ctlfile (TLV)                                                                            ...  
      +----------------------+          +---------------+              +---------------+               
    +--------------------------+          file contents                  file contents                
                                                                                                      
    +--------------------------+     -  +---------------+      -    -  +---------------+      -       
      _catalog (TLV)                                                                                  
    +--------------------------+      +-----------------------+      +-----------------------+        
  +------------------------------+  +---------------------------+  +---------------------------+      
+----------------------------------------------------------------------------------------------------+
Encryption schemes Several AES key sizes are supported, such as 128 and 256 bits. The Cipher Block Chaining (CBC) block cipher mode of operation is used to decrypt multiple AES 16-byte blocks, which means an initialisation vector (IV) is stored in clear along with the ciphertext. All filenames and file contents are encrypted using the same encryption mode, key and IV (e.g. if you remove and re-add a file in the archive, the resulting stream will be identical). No cleartext padding is used during encryption; instead, several end-of-stream handlers are available, so the ciphertext has exactly the size of the cleartext (e.g. the size of the compressed file). The following variants were identified in the 'encryption_mode' field. STREAM This is the end-of-stream handler for: This end-of-stream handler is apparently specific to the .zed format, and applied when the cleartext's does not end on a 16-byte boundary ; in this case special processing is performed on the last partial 16-byte block. The encryption and decryption phases are identical: let's assume the last partial block of cleartext (for encryption) or ciphertext (for decryption) was appended after all the complete 16-byte blocks of ciphertext: In either case, if the full ciphertext is less then one AES block (< 16 bytes), then the IV is used instead of the second-to-last block. CTS CTS or CipherText Stealing is the end-of-stream handler for: It matches the CBC-CS3 variant as described in Recommendation for Block Cipher Modes of Operation: Three Variants of Ciphertext Stealing for CBC Mode. Empty cleartext Since empty filenames or metadata are invalid, and since all files are compressed (resulting in a minimum 8-byte zlib cleartext), no empty cleartext was encrypted in the archive. metadata stream It is named 05356861616161716149656b7a6565636e576a33317a7868304e63 (hexadecimal), i.e. the character with code 5 followed by '5haaaaqaIekzeecnWj31zxh0Nc' (ASCII). The format used is OLE Property Set (MS-OLEPS). It introduces 2 property names "_ctlfile" (index 3) and "_catalog" (index 4), and 2 instances of said properties each containing an application-specific VT_BLOB (type 0x0041). _ctlfile: obfuscated global properties and access list This subpart is stored under index 3 ("_ctlfile") of the MS-OLEPS metadata. It consists of: The ciphertext is encrypted with AES-CBC "STREAM" mode using 128-bit static key 37F13CF81C780AF26B6A52654F794AEF (hexadecimal) and the prepended IV so as to obfuscate the access list. The ciphertext is continuous and not split in chunks (unlike files), even when it is larger than 512 bytes. The decrypted text contain properties in a TLV format as described in _ctlfile TLV: Archives may include "mandatory" users that cannot be removed. They are typically used to add an enterprise wide recovery RSA key to all archives. Extreme care must be taken to protect these key, as it can decrypt all past archives generated from within that company. _catalog: file list This subpart is stored under index 4 ("_catalog") of the MS-OLEPS metadata. It contains a series of 'fileprops' TLV structures, one for each file or directory. The file hierarchy can be reconstructed by checking the 'parent_id' field of each file entry. If 'parent_id' is 0 then the file is located at the top-level of the hierarchy, otherwise it's located under the directory with the matching 'file_id'. TLV format This format is a series of fields : Value semantics depend on its Type. It may contain an uint32be integer, a UTF-16LE string, a character sequence, or an inner TLV structure. Unless otherwise noted, TLV structures appear once. Some fields are optional and may not be present at all (e.g. 'archive_createdwith'). Some fields are unique within a structure (e.g. 'files_iv'), other may be repeated within a structure to form a list (e.g. 'fileprops' and 'passworduser'). The following top-level types that have been identified, and detailed in the next sections: Some additional unidentified types may be present. _ctlfile TLV _catalog TLV Decrypting the archive AES key rsauser The user accessing the archive will be authenticated by comparing his/her X509 certificate with the one stored in the 'certificate' field using DER format. The 'files_key_ciphertext' field is then decrypted using the PKCS#1 v1.5 encryption mechanism, with the private key that matches the user certificate. passworduser An intermediary user key, a user IV and an integrity checksum will be derived from the user password, using the deprecated PKCS#12 method as described at rfc7292 appendix B. Note: this is not PKCS#5 (nor PBKDF1/PBKDF2), this is an incompatible method from PKCS#12 that notably does not use HMAC. The 'pkcs12_hashfunc' field defines the underlying hash function. The following values have been identified: PBA - Password-based authentication The user accessing the archive will be authenticated by deriving an 8-byte sequence from his/her password. The parameters for the derivation function are: The derivation is checked against 'pba_checksum'. PBE - Password-based encryption Once the user is identified, 2 new values are derived from the password with different parameters to produce the IV and the key decryption key, with the same hash function: The parameters specific to user key are: The user key needs to be truncated to a length of 'encryption_strength', as specified in bytes in the archive properties. The parameters specific to user IV are: Once the key decryption key and the IV are derived, 'files_key_ciphertext' is decrypted using AES CBC, with PKCS#7 padding. Identifying file streams The name of the MS-CFB stream is derived by shuffling the bytes from the 'file_id' field and then encoding the result as hexadecimal. The reordering is: 
Initial  offset: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Shuffled offset: 3 2 1 0 5 4 7 6 8 9 10 11 12 13 14 15
The 16th byte is usually a NUL byte, hence the stream identifier is a 30-character-long string. Decrypting files The compressed stream is split in chunks of 512 bytes, each of them encrypted separately using AES CBS and the global archive encryption scheme. Decryption uses the global AES key (retrieved using the user credentials), and the global IV (retrieved from the deobfuscated archive metadata). The IV for each chunk is computed by: Each chunk is an independent stream and the decryption process involves end-of-stream handling even if this is not the end of the actual file. This is particularly important for the CTS handler. Note: this is not to be confused with CTR block cipher mode of operation with operates differently and requires a nonce. Decompressing files Compressed streams are zlib stream with default compression options and can be decompressed following the zlib format. Test cases Excluded for brevity, cf. https://www.beuc.net/zed/#test-cases. Conventions and references Feedback Feel free to send comments at beuc@beuc.net. If you have .zed files that you think are not covered by this document, please send them as well (replace sensitive files with other ones). The author's GPG key can be found at 8FF1CB6E8D89059F. Copyright (C) 2017 Sylvain Beucler Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved. This file is offered as-is, without any warranty.

Sylvain Beucler: dot-zed archive file format

TL,DR: I reverse-engineered the .zed encrypted archive format.
Following a clean-room design, I'm providing a description that can be implemented by a third-party.
Interested? :) (reference version at: https://www.beuc.net/zed/) .zed archive file format Introduction Archives with the .zed extension are conceptually similar to an encrypted .zip file. In addition to a specific format, .zed files support multiple users: files are encrypted using the archive master key, which itself is encrypted for each user and/or authentication method (password, RSA key through certificate or PKCS#11 token). Metadata such as filenames is partially encrypted. .zed archives are used as stand-alone or attached to e-mails with the help of a MS Outlook plugin. A variant, which is not covered here, can encrypt/decrypt MS Windows folders on the fly like ecryptfs. In the spirit of academic and independent research this document provides a description of the file format and encryption algorithms for this encrypted file archive. See the conventions section for conventions and acronyms used in this document. Structure overview The .zed file format is composed of several layers. Or as a diagram: 
+----------------------------------------------------------------------------------------------------+
  .zed archive (MS-CBF)                                                                               
                                                                                                      
   stream #1                         stream #2                       stream #3...                     
  +------------------------------+  +---------------------------+  +---------------------------+      
    metadata (MS-OLEPS)               encryption (AES)               encryption (AES)                 
                                      512-bytes chunks               512-bytes chunks                 
    +--------------------------+                                                                      
      obfuscation (static key)        +-----------------------+      +-----------------------+        
      +----------------------+       -  compression (zlib)     -    -  compression (zlib)     -       
       _ctlfile (TLV)                                                                            ...  
      +----------------------+          +---------------+              +---------------+               
    +--------------------------+          file contents                  file contents                
                                                                                                      
    +--------------------------+     -  +---------------+      -    -  +---------------+      -       
      _catalog (TLV)                                                                                  
    +--------------------------+      +-----------------------+      +-----------------------+        
  +------------------------------+  +---------------------------+  +---------------------------+      
+----------------------------------------------------------------------------------------------------+
Encryption schemes Several AES key sizes are supported, such as 128 and 256 bits. The Cipher Block Chaining (CBC) block cipher mode of operation is used to decrypt multiple AES 16-byte blocks, which means an initialisation vector (IV) is stored in clear along with the ciphertext. All filenames and file contents are encrypted using the same encryption mode, key and IV (e.g. if you remove and re-add a file in the archive, the resulting stream will be identical). No cleartext padding is used during encryption; instead, several end-of-stream handlers are available, so the ciphertext has exactly the size of the cleartext (e.g. the size of the compressed file). The following variants were identified in the 'encryption_mode' field. STREAM This is the end-of-stream handler for: This end-of-stream handler is apparently specific to the .zed format, and applied when the cleartext's does not end on a 16-byte boundary ; in this case special processing is performed on the last partial 16-byte block. The encryption and decryption phases are identical: let's assume the last partial block of cleartext (for encryption) or ciphertext (for decryption) was appended after all the complete 16-byte blocks of ciphertext: In either case, if the full ciphertext is less then one AES block (< 16 bytes), then the IV is used instead of the second-to-last block. CTS CTS or CipherText Stealing is the end-of-stream handler for: It matches the CBC-CS3 variant as described in Recommendation for Block Cipher Modes of Operation: Three Variants of Ciphertext Stealing for CBC Mode. Empty cleartext Since empty filenames or metadata are invalid, and since all files are compressed (resulting in a minimum 8-byte zlib cleartext), no empty cleartext was encrypted in the archive. metadata stream It is named 05356861616161716149656b7a6565636e576a33317a7868304e63 (hexadecimal), i.e. the character with code 5 followed by '5haaaaqaIekzeecnWj31zxh0Nc' (ASCII). The format used is OLE Property Set (MS-OLEPS). It introduces 2 property names "_ctlfile" (index 3) and "_catalog" (index 4), and 2 instances of said properties each containing an application-specific VT_BLOB (type 0x0041). _ctlfile: obfuscated global properties and access list This subpart is stored under index 3 ("_ctlfile") of the MS-OLEPS metadata. It consists of: The ciphertext is encrypted with AES-CBC "STREAM" mode using 128-bit static key 37F13CF81C780AF26B6A52654F794AEF (hexadecimal) and the prepended IV so as to obfuscate the access list. The ciphertext is continuous and not split in chunks (unlike files), even when it is larger than 512 bytes. The decrypted text contain properties in a TLV format as described in _ctlfile TLV: Archives may include "mandatory" users that cannot be removed. They are typically used to add an enterprise wide recovery RSA key to all archives. Extreme care must be taken to protect these key, as it can decrypt all past archives generated from within that company. _catalog: file list This subpart is stored under index 4 ("_catalog") of the MS-OLEPS metadata. It contains a series of 'fileprops' TLV structures, one for each file or directory. The file hierarchy can be reconstructed by checking the 'parent_id' field of each file entry. If 'parent_id' is 0 then the file is located at the top-level of the hierarchy, otherwise it's located under the directory with the matching 'file_id'. TLV format This format is a series of fields : Value semantics depend on its Type. It may contain an uint32be integer, a UTF-16LE string, a character sequence, or an inner TLV structure. Unless otherwise noted, TLV structures appear once. Some fields are optional and may not be present at all (e.g. 'archive_createdwith'). Some fields are unique within a structure (e.g. 'files_iv'), other may be repeated within a structure to form a list (e.g. 'fileprops' and 'passworduser'). The following top-level types that have been identified, and detailed in the next sections: Some additional unidentified types may be present. _ctlfile TLV _catalog TLV Decrypting the archive AES key rsauser The user accessing the archive will be authenticated by comparing his/her X509 certificate with the one stored in the 'certificate' field using DER format. The 'files_key_ciphertext' field is then decrypted using the PKCS#1 v1.5 encryption mechanism, with the private key that matches the user certificate. passworduser An intermediary user key, a user IV and an integrity checksum will be derived from the user password, using the deprecated PKCS#12 method as described at rfc7292 appendix B. Note: this is not PKCS#5 (nor PBKDF1/PBKDF2), this is an incompatible method from PKCS#12 that notably does not use HMAC. The 'pkcs12_hashfunc' field defines the underlying hash function. The following values have been identified: PBA - Password-based authentication The user accessing the archive will be authenticated by deriving an 8-byte sequence from his/her password. The parameters for the derivation function are: The derivation is checked against 'pba_checksum'. PBE - Password-based encryption Once the user is identified, 2 new values are derived from the password with different parameters to produce the IV and the key decryption key, with the same hash function: The parameters specific to user key are: The user key needs to be truncated to a length of 'encryption_strength', as specified in bytes in the archive properties. The parameters specific to user IV are: Once the key decryption key and the IV are derived, 'files_key_ciphertext' is decrypted using AES CBC, with PKCS#7 padding. Identifying file streams The name of the MS-CFB stream is derived by shuffling the bytes from the 'file_id' field and then encoding the result as hexadecimal. The reordering is: 
Initial  offset: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Shuffled offset: 3 2 1 0 5 4 7 6 8 9 10 11 12 13 14 15
The 16th byte is usually a NUL byte, hence the stream identifier is a 30-character-long string. Decrypting files The compressed stream is split in chunks of 512 bytes, each of them encrypted separately using AES CBS and the global archive encryption scheme. Decryption uses the global AES key (retrieved using the user credentials), and the global IV (retrieved from the deobfuscated archive metadata). The IV for each chunk is computed by: Each chunk is an independent stream and the decryption process involves end-of-stream handling even if this is not the end of the actual file. This is particularly important for the CTS handler. Note: this is not to be confused with CTR block cipher mode of operation with operates differently and requires a nonce. Decompressing files Compressed streams are zlib stream with default compression options and can be decompressed following the zlib format. Test cases Excluded for brevity, cf. https://www.beuc.net/zed/#test-cases. Conventions and references Feedback Feel free to send comments at beuc@beuc.net. If you have .zed files that you think are not covered by this document, please send them as well (replace sensitive files with other ones). The author's GPG key can be found at 8FF1CB6E8D89059F. Copyright (C) 2017 Sylvain Beucler Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved. This file is offered as-is, without any warranty.

8 September 2017

Vincent Fourmond: Extract many attachement from many mails in one go using ripmime

I was recently looking for a way to extract many attachments from a series of emails. I first had a look at the AttachmentExtractor thunderbird plugin, but it seems very old and not maintained anymore. So I've come up with another very simple solution that also works with any other mail client.Just copy all the mails you want to extract attachments from to a single (temporary) mail folder, find out which file holds the mail folder and use ripmime on that file (ripmime is packaged for Debian). For my case, it looked like:
~ ripmime -i .icedove/XXXXXXX.default/Mail/pop.xxxx/tmp -d target-directory
Simple solution, but it saved me quite some time. Hope it helps !

7 September 2017

Gunnar Wolf: It was thirty years ago today... (and a bit more): My first ever public speech!

I came across a folder with the most unexpected treasure trove: The text for my first ever public speech! (and some related materials)
In 1985, being nine years old, I went to the IDESE school, to learn Logo. I found my diploma over ten years ago and blogged about it in this same space. Of course, I don't expect any of you to remember what I wrote twelve years ago about a (then) twenty years old piece of paper! I add to this very old stuff about Gunnar the four pages describing my game, Evitamono ("Avoid the monkey", approximately). I still remember the game quite vividly, including traumatic issues which were quite common back then; I wrote that the sprites were accidentally deleted twice and the game once . I remember several of my peers telling about such experiences. Well, that is good if you account for the second system syndrome! I also found the amazing course material for how to program sound and graphics in the C64 BASIC. That was a course taken by ten year old kids. Kids that understood that you had to write [255,129,165,244,219,165,0,102] (see pages 3-5) into a memory location starting at 53248 to redefine a character so it looked as the graphic element you wanted. Of course, it was done with a set of POKEs, as everything in C64. Or that you could program sound by setting the seven SID registers for each of the three voices containing low frequency, high frequency, low pulse, high pulse, wave control, wave length, wave amplitude in memory locations 54272 through 54292... And so on and on and on... And as a proof that I did take the course: ...I don't think I could make most of my current BSc students make sense out of what is in the manual. But, being a kid in the 1980s, that was the only way to get a computer to do what you wanted. Yay for primitivity! :-D
AttachmentSize
Speech for "Evitamono"1.29 MB
Coursee material for sound and graphics programming in C64 BASIC15.82 MB
Proof that I was there!4.86 MB

31 August 2017

Chris Lamb: Free software activities in August 2017

Here is my monthly update covering what I have been doing in the free software world in August 2017 (previous month):
Reproducible builds

Whilst anyone can inspect the source code of free software for malicious flaws, most software is distributed pre-compiled to end users. The motivation behind the Reproducible Builds effort is to allow verification that no flaws have been introduced either maliciously or accidentally during this compilation process by promising identical results are always generated from a given source, thus allowing multiple third-parties to come to a consensus on whether a build was compromised. I have generously been awarded a grant from the Core Infrastructure Initiative to fund my work in this area. This month I:
  • Presented a status update at Debconf17 in Montr al, Canada alongside Holger Levsen, Maria Glukhova, Steven Chamberlain, Vagrant Cascadian, Valerie Young and Ximin Luo.
  • I worked on the following issues upstream:
    • glib2.0: Please make the output of gio-querymodules reproducible. (...)
    • gcab: Please make the output reproducible. (...)
    • gtk+2.0: Please make the immodules.cache files reproducible. (...)
    • desktop-file-utils: Please make the output reproducible. (...)
  • Within Debian:
  • Categorised a large number of packages and issues in the Reproducible Builds "notes" repository.
  • Worked on publishing our weekly reports. (#118, #119, #120, #121 & #122)

I also made the following changes to our tooling:
diffoscope

diffoscope is our in-depth and content-aware diff utility that can locate and diagnose reproducibility issues.

  • Use name attribute over path to avoid leaking comparison full path in output. (commit)
  • Add missing skip_unless_module_exists import. (commit)
  • Tidy diffoscope.progress and the XML comparator (commit, commit)

disorderfs

disorderfs is our FUSE-based filesystem that deliberately introduces non-determinism into directory system calls in order to flush out reproducibility issues.

  • Add a simple autopkgtest smoke test. (commit)


Debian
Patches contributed
  • openssh: Quote the IP address in ssh-keygen -f suggestions. (#872643)
  • libgfshare:
    • SIGSEGV if /dev/urandom is not accessible. (#873047)
    • Add bindnow hardening. (#872740)
    • Support nodoc build profile. (#872739)
  • devscripts:
  • memcached: Add hardening to systemd .service file. (#871610)
  • googler: Tidy long and short package descriptions. (#872461)
  • gnome-split: Homepage points to domain-parked website. (#873037)
Uploads
  • python-django 1:1.11.4-1 New upstream release.
  • redis:
    • 4:4.0.1-3 Drop yet more non-deterministic tests.
    • 4:4.0.1-4 Tighten systemd/seccomp hardening.
    • 4:4.0.1-5 Drop even more tests with timing issues.
    • 4:4.0.1-6 Don't install completions to /usr/share/bash-completion/completions/debian/bash_completion/.
    • 4:4.0.1-7 Don't let sentinel integration tests fail the build as they use too many timers to be meaningful. (#872075)
  • python-gflags 1.5.1-3 If SOURCE_DATE_EPOCH is set, either use that as a source of current dates or the UTC-version of the file's modification time (#836004), don't call update-alternatives --remove in postrm. update debian/watch/Homepage & refresh/tidy the packaging.
  • bfs 1.1.1-1 New upstream release, tidy autopkgtest & patches, organising the latter with Pq-Topic.
  • python-daiquiri 1.2.2-1 New upstream release, tidy autopkgtests & update travis.yml from travis.debian.net.
  • aptfs 2:0.10-2 Add upstream signing key, refer to /usr/share/common-licenses/GPL-3 in debian/copyright & tidy autopkgtests.
  • adminer 4.3.1-2 Add a simple autopkgtest & don't install the Selenium-based tests in the binary package.
  • zoneminder (1.30.4+dfsg-2) Prevent build failures with GCC 7 (#853717) & correct example /etc/fstab entries in README.Debian (#858673).

Finally, I reviewed and sponsored uploads of astral, inflection, more-itertools, trollius-redis & wolfssl.
Debian LTS

This month I have been paid to work 18 hours on Debian Long Term Support (LTS). In that time I did the following:
  • "Frontdesk" duties, triaging CVEs, etc.
  • Issued DLA 1049-1 for libsndfile preventing a remote denial of service attack.
  • Issued DLA 1052-1 against subversion to correct an arbitrary code execution vulnerability.
  • Issued DLA 1054-1 for the libgxps XML Paper Specification library to prevent a remote denial of service attack.
  • Issued DLA 1056-1 for cvs to prevent a command injection vulnerability.
  • Issued DLA 1059-1 for the strongswan VPN software to close a denial of service attack.
Debian bugs filed
  • wget: Please hash the hostname in ~/.wget-hsts files. (#870813)
  • debian-policy: Clarify whether mailing lists in Maintainers/Uploaders may be moderated. (#871534)
  • git-buildpackage: "pq export" discards text within square brackets. (#872354)
  • qa.debian.org: Escape HTML in debcheck before outputting. (#872646)
  • pristine-tar: Enable multithreaded compression in pristine-xz. (#873229)
  • tryton-meta: Please combine tryton-modules-* into a single source package with multiple binaries. (#873042)
  • azure-cli:
  • fwupd-tests: Don't ship test files to generic /usr/share/installed-tests dir. (#872458)
  • libvorbis: Maintainer fields points to a moderated mailing list. (#871258)
  • rmlint-gui: Ship a rmlint-gui binary. (#872162)
  • template-glib: debian/copyright references online source without quotation. (#873619)
FTP Team

As a Debian FTP assistant I ACCEPTed 147 packages: abiword, adacgi, adasockets, ahven, animal-sniffer, astral, astroidmail, at-at-clojure, audacious, backdoor-factory, bdfproxy, binutils, blag-fortune, bluez-qt, cheshire-clojure, core-match-clojure, core-memoize-clojure, cypari2, data-priority-map-clojure, debian-edu, debian-multimedia, deepin-gettext-tools, dehydrated-hook-ddns-tsig, diceware, dtksettings, emacs-ivy, farbfeld, gcc-7-cross-ports, git-lfs, glewlwyd, gnome-recipes, gnome-shell-extension-tilix-dropdown, gnupg2, golang-github-aliyun-aliyun-oss-go-sdk, golang-github-approvals-go-approval-tests, golang-github-cheekybits-is, golang-github-chzyer-readline, golang-github-denverdino-aliyungo, golang-github-glendc-gopher-json, golang-github-gophercloud-gophercloud, golang-github-hashicorp-go-rootcerts, golang-github-matryer-try, golang-github-opentracing-contrib-go-stdlib, golang-github-opentracing-opentracing-go, golang-github-tdewolff-buffer, golang-github-tdewolff-minify, golang-github-tdewolff-parse, golang-github-tdewolff-strconv, golang-github-tdewolff-test, golang-gopkg-go-playground-validator.v8, gprbuild, gsl, gtts, hunspell-dz, hyperlink, importmagic, inflection, insighttoolkit4, isa-support, jaraco.itertools, java-classpath-clojure, java-jmx-clojure, jellyfish1, lazymap-clojure, libblockdev, libbytesize, libconfig-zomg-perl, libdazzle, libglvnd, libjs-emojify, libjwt, libmysofa, libundead, linux, lua-mode, math-combinatorics-clojure, math-numeric-tower-clojure, mediagoblin, medley-clojure, more-itertools, mozjs52, openssh-ssh1, org-mode, oysttyer, pcscada, pgsphere, poppler, puppetdb, py3status, pycryptodome, pysha3, python-cliapp, python-coloredlogs, python-consul, python-deprecation, python-django-celery-results, python-dropbox, python-fswrap, python-hbmqtt, python-intbitset, python-meshio, python-parameterized, python-pgpy, python-py-zipkin, python-pymeasure, python-thriftpy, python-tinyrpc, python-udatetime, python-wither, python-xapp, pythonqt, r-cran-bit, r-cran-bit64, r-cran-blob, r-cran-lmertest, r-cran-quantmod, r-cran-ttr, racket-mode, restorecond, rss-bridge, ruby-declarative, ruby-declarative-option, ruby-errbase, ruby-google-api-client, ruby-rash-alt, ruby-representable, ruby-test-xml, ruby-uber, sambamba, semodule-utils, shimdandy, sjacket-clojure, soapysdr, stencil-clojure, swath, template-glib, tools-analyzer-jvm-clojure, tools-namespace-clojure, uim, util-linux, vim-airline, vim-airline-themes, volume-key, wget2, xchat, xfce4-eyes-plugin & xorg-gtest. I additionally filed 6 RC bugs against packages that had incomplete debian/copyright files against: gnome-recipes, golang-1.9, libdazzle, poppler, python-py-zipkin & template-glib.

29 August 2017

Colin Watson: env chdir

I was recently asked to sort things out so that snap builds on Launchpad could themselves install snaps as build-dependencies. To make this work we need to start doing builds in LXD containers rather than in chroots. As a result I ve been doing some quite extensive refactoring of launchpad-buildd: it previously had the assumption that it was going to use a chroot for everything baked into lots of untested helper shell scripts, and I ve been rewriting those in Python with unit tests and with a single Backend abstraction that isolates the high-level logic from the details of where each build is being performed. This is all interesting work in its own right, but it s not what I want to talk about here. While I was doing all this refactoring, I ran across a couple of methods I wrote a while back which looked something like this: 
def chroot(self, args, echo=False):
    """Run a command in the chroot.
    :param args: the command and arguments to run.
    """
    args = set_personality(
        args, self.options.arch, series=self.options.series)
    if echo:
        print("Running in chroot: %s" %
              ' '.join("'%s'" % arg for arg in args))
        sys.stdout.flush()
    subprocess.check_call([
        "/usr/bin/sudo", "/usr/sbin/chroot", self.chroot_path] + args)
def run_build_command(self, args, env=None, echo=False):
    """Run a build command in the chroot.
    This is unpleasant because we need to run it in /build under sudo
    chroot, and there's no way to do this without either a helper
    program in the chroot or unpleasant quoting.  We go for the
    unpleasant quoting.
    :param args: the command and arguments to run.
    :param env: dictionary of additional environment variables to set.
    """
    args = [shell_escape(arg) for arg in args]
    if env:
        args = ["env"] + [
            "%s=%s" % (key, shell_escape(value))
            for key, value in env.items()] + args
    command = "cd /build && %s" % " ".join(args)
    self.chroot(["/bin/sh", "-c", command], echo=echo)
(I ve already replaced the chroot method with a call to Backend.run, but it s easier to see what I m talking about in the original form.) One thing to notice about this code is that it uses several adverbial commands: that is, commands that run another command in a different way. For example, sudo runs another command as another user, while chroot runs another command with a different root directory, and env runs another command with different environment variables set. These commands chain neatly, and they also have the useful property that they take the subsidiary command and its arguments as a list of arguments. coreutils has several other commands that behave this way, and adverbio is another useful example. By contrast, su -c is something you might call a quasi-adverbial command: it does modify the behaviour of another command, but it takes it as a single argument which it then passes to sh -c. Every time you have something that s passed to a shell like this, you need a corresponding layer of shell quoting to escape any shell metacharacters that should be interpreted literally. This is often cumbersome and is easy to get wrong. My Python implementation is as follows, and I wouldn t be totally surprised to discover that it contained a bug: 
import re
non_meta_re = re.compile(r'^[a-zA-Z0-9+,./:=@_-]+$')
def shell_escape(arg):
    if non_meta_re.match(arg):
        return arg
    else:
        return "'%s'" % arg.replace("'", "'\\''")
Python >= 3.3 has shlex.quote, which is an improvement and we should probably use that instead, but it s still another thing to forget to call. This is why process-spawning libraries such as Python s subprocess, Perl s system and open, and my own libpipeline for C encourage programmers to use a list syntax and to avoid involving the shell entirely wherever possible. One thing that the standard Unix tools don t let you do in an adverbial way is to change your working directory, and I ve run into this annoying limitation several times. This means that it s difficult to chain that operation together with other adverbs, for example to run a command in a particular working directory inside a chroot. The workaround I used above was to invoke a shell that runs cd /build && ..., but that s another command that s only quasi-adverbial, since the extra shell means an extra layer of shell quoting. (Ian Jackson rightly observes that you can in fact write the necessary adverb as something like sh -ec 'cd "$1"; shift; exec "$@"' chdir. I think that s a bit uglier than I ideally want to use in production code, but you might reasonably think that it s worth it to avoid the extra layer of shell quoting.) I therefore decided that this was a feature that belonged in coreutils, and after a bit of mailing list discussion we felt it was best implemented as a new option to env(1). I sent a patch for this which has been accepted. This means that we have a new composable adverb, env --chdir=NEWDIR, which will allow the run_build_command method above to be rewritten as something like this: 
def run_build_command(self, args, env=None, echo=False):
    """Run a build command in the chroot.
    :param args: the command and arguments to run.
    :param env: dictionary of additional environment variables to set.
    """
    env_args = ["env", "--chdir=/build"]
    if env:
        for key, value in env.items():
            env_args.append("%s=%s" % (key, value))
    self.chroot(env_args + args, echo=echo)
The env --chdir option will be in coreutils 8.28. We won t be able to use it in launchpad-buildd until that s available in all Ubuntu series we might want to build for, so in this particular application that s going to take a few years; but other applications may well be able to make use of it sooner.

Carl Chenet: Send scheduled messages to both Twitter and Mastodon with the Remindr bot

Do you need to send messages to both Twitter and Mastodon? Use the Remindr bot! Remindr is written in Python, released under the GPLv3 license. 1. How to install Remindr Install Remindr from PyPI: 
# pip3 install remindr
2. How to configure Remindr First, start by writing a messages.txt file with the following content: 
o en Send scheduled messages to both Twitter and Mastodon with the Remindr bot https://carlchenet.com/send-scheduled-messages-to-both-twitter-and-mastodon-with-the-remindr-bot #remindr #twitter #mastodon
x en Follow Carl Chenet for great news about Free Software! https://carlchenet.com #freesoftware
The first field only indicates if the line is the next one to be considered by Remindr, the o indicates the next line to be sent, x means it won t. The second field is the 2-letters code language your content is using, in my example en or fr. Next content on the line will compose the body of your messages to Mastodon and Twitter. You need to configure the Mastodon and the Twitter credentials in order to allow Remindr to send the messages. First you need to generate the credentials. For Twitter, you need to manually create an app on apps.twitter.com. For Mastodon, just launch the following command: 
$ register_remindr_app
Some information will be asked by the command. At the end, two files are created, remindr_usercred.txt and remindr_clientcred.txt. You re going to need them for the Remindr configuration above. For the Remindr configuration, here is a complete configuration using the 
[mastodon]
instance_url=https://mastodon.social
user_credentials=remindr_usercred.txt
client_credentials=remindr_clientcred.txt
[twitter]
consumer_key=a6lv2gZxkvk6UbQ30N4vFmlwP
consumer_secret=j4VxM2slv0Ud4rbgZeGbBzPG1zoauBGLiUMOX0MGF6nsjcyn4a
access_token=1234567897-Npq5fYybhacYxnTqb42Kbb3A0bKgmB3wm2hGczB
access_token_secret=HU1sjUif010DkcQ3SmUAdObAST14dZvZpuuWxGAV0xFnC
[image]
path_to_image=/home/chaica/blog-carl-chenet.png
[entrylist]
path_to_list=/etc/remindr/messages.txt
Your configuration is complete! Now we have to check if everything is fine.

Read the full documentation on Readthedocs.

3. How to use Remindr Now let s try your configuration by launching Remindr the first time by-hand: 
$ remindr -c /etc/remindr/remindr.ini
The messages should appear on both Twitter and Mastodon. 4. How to schedule the Remindr execution The easiest way is to use you user crontab. Just add the following line in your crontab file, editing it with crontab -e 
00 10 * * * remindr -c /etc/remindr/remindr.ini
From now on, your message will be sent every day at 10:00AM. Going further with Remindr and finally You can help me developing tools for Mastodon and other social networks by donating anything through Liberaypay (also possible with cryptocurrencies). Any contribution will be appreciated. That s a big factor motivation
Donate You also may follow my account @carlchenet on Mastodon

27 August 2017

Carl Chenet: The Importance of Choosing the Correct Mastodon Instance

Remember, Mastodon is a new decentralized social network, based on a free software which is rapidly gaining users (already there is more than 1.5 million accounts). As I ve created my account in June, I was a fast addict and I ve already created several tools for this network, Feed2toot, Remindr and Boost (mostly written in Python).

Now, with all this experience I have to stress out the importance of choosing the correct Mastodon instance.

Some technical reminders on how Mastodon works

First, let s quickly clarify something about the decentralized part. In Mastodon, decentralization is made through a federation of dedicated servers, called instances , each one with a complete independent administration. Your user account is created on one specific instance. You have two choices:

  • Create your own instance. Which requires advanced technical knowledge.
  • Create your user account on a public instance. Which is the easiest and fastest way to start using Mastodon.

You can move your user account from one instance to another, but you have to follow a special procedure which can be quite long, considering your own interest for technical manipulation and the total amount of your followers you ll have to warn about your change. As such, you ll have to create another account on a new instance and import three lists: the one with your followers, the one with the accounts you have blocked, and the one with the account you have muted.

From this working process, several technical and human factors will interest us.

A good technical administration for instance

As a social network, Mastodon is truly decentralized, with more than 1.5 million users on more than 2350 existing instances. As such, the most common usage is to create an account on an open instance. To create its own instance is way too difficult for the average user. Yet, using an open instance creates a strong dependence on the technical administrator of the chosen instance.

The technical administrator will have to deal with several obligations to ensure its service continuity, with high-quality hardware and regular back-ups. All of these have a price, either in money and in time. Regarding the time factor, it would be better to choose an administration team over an individual, as life events can change quite fast everyone s interests. As such, Framasoft, a French association dedicated to promoting the Free software use, offers its own Mastodon instance named: Framapiaf. The creator of the mastodon project, also offers a quite solid instance, Mastodon.social (see below).

Regarding the money factor, many instance administrators with a large number of users are currently asking for donation via Patreon, as hosting an instance server or renting one cost money.

Mastodon.social, the first instance of the Mastodon network

The Ideological Trend Of Your Instance

If anybody could have guessed the previous technical points since the recent registration explosion on the Mastodon social network, the following point took almost everyone by surprise. Little by little, different instances show their culture , their protest action, and their propaganda on this social network.

As the instance administrator has all the powers over its instance, he or she can block the instance of interacting with some other instances, or ban its instance s users from any interaction with other instances users.

With everyone having in mind the main advantages to have federalized instance from, this partial independence of some instances from the federation was a huge surprise. One of the most recent example was when the Unixcorn.xyz instance administrator banned its users from reading Aeris account, which was on its own instance. It was a cataclysm with several consequences, which I ve named the #AerisGate as it shows the different views on moderation and on its reception by various Mastodon users.

If you don t manage your own instance, when you ll have to choose the one where to create your account, make sure that the content you plan to toot is within the rules and compatible with the ideology of said instance s administrator. Yes, I know, it may seem surprising but, as stated above, by entering a public instance you become dependent on someone else s infrastructure, who may have an ideological way to conceive its Mastodon hosting service. As such, if you re a nazi, for example, don t open your Mastodon account on a far-left LGBT instance. Your account wouldn t stay open for long.

The moderation rules are described in the about/more page of the instance, and may contain ideological elements.

To ease the process for newcomers, it is now possible to use a great tool to select what instance should be the best to host your account.

Remember that, as stated above, Mastodon is decentralized, and as such there is no central authority which can be reached in case you have a conflict with your instance administrator. And nobody can force said administrator to follow its own rules, or not to change them on the fly. Think Twice Before Creating Your Account

If you want to create an account on an instance you don t control, you need to check two elements: the availability of the instance hosting service in the long run, often linked to the administrator or the administration group of said instance, and the ideological orientation of your instance. With these two elements checked, you ll be able to let your Mastodon account growth peacefully, without fearing an outage of your instance, or simple your account blocked one morning because it doesn t align with your instance s ideological line.

in Conclusion

To help me get involved in free software and writing articles for this blog, please consider a donation through my Liberapay page, even if it s only a few cents per week. My contact Bitcoin and Monero are also available on this page. Follow me on Mastodon Translated from French to English by St phanie Chaptal.

24 August 2017

Urvika Gola: Much awaited.. DebConf 17 in Montreal.

On 5th August I got a chance to attend, speak and experience DebConf 2017 at Montreal, Canada. The conference was stretch ed from 6 August to 12 August .
debconf_picture1Seasons of Debian Summer of Code & Winter of Outreachy
Pretty late for me to document my DebConf fun-learning-experiences, thanks to my delaying tactics.. I need to overcome.
But better late than ever, I had amazing time at DebConf. I got to meet and learn from my Outreachy Mentor, Daniel Pocock!
img_5634-e1503506917678.jpgPicture of Daniel and me captured by : Dorina Mosku
One thing about DebConf I loved was the amount of Diversity in Debian family! As a beginner, I got to get a big picture of what all projects are there. Daniel helped me a lot in getting started with packaging in Debian. I really appreciate the time he took out to guide me @DebConf and Pranav, remotely. One specific line I liked about Daniel s talk on Open Day, 5th August Free Communications with Free Software and Debian while talking about free RTC (Real Time Communication) is that, ..Instead of communication controlling the user, the user can control the communcation.. I talked about free RTC, my Project Lumicall and about my journey being an Outreachy Intern with Debian. I also covered my co-speaker s project work on Lumicall being a GSoC 2016 student.
IMG_0796Picture captured by Aigars Mahinovs
debconf_picture2Managing Debian s RTC services Daniel Pocock
Meeting the Outreachy family feels amaazzing! Karen Sandler, executive director of the Software Freedom Conservancy gave a talk on the Significance and Impact of Outreachy and Debian s support for the programme.
DG58B_gXUAA2GsAwith Karen Sandler and Outreachy alumini
DebConf 2017 has been a wonderful conference with the community being very welcoming and helpful

21 August 2017

Carl Chenet: Remind people about your great content using social networks with Remindr

Each time I remind people about one of my best blog posts, I do have positive reviews and a peak of traffic on my blog. But as an IT guy, I hate (so much) manually (gosh!) posting reminders of my articles on both my Twitter account and my Mastodon account. So I wrote Remindr. Each time you launch it, it posts a content through both Mastodon and Twitter. You can attach an image for each message and using different languages is managed for your different content is managed. Under the hood, it s a self hosted (my instance just runs on my workstation) Python 3 application released under the GPLv3 license. Going further with Remindr How does exactly Remindr work? Remindr iterates through a list of messages in a file you write and extract one line for each execution of Remindr, adding a user-defined prefix and send them to both the Mastodon and Twitter social networks. Here is the format of the file: 
o en Automatically Send Toots To The Mastodon Social Network https://carlchenet.com/automatically-send-toots-to-the-mastodon-social-network/ #Mastodon
x fr Sur Mastodon, cr er son compte de secours  ou tout perdre https://carlchenet.com/sur-mastodon-creer-son-compte-de-secours-ou-tout-perdre/ #Mastodon
x en Automatically boost cool toots on Mastodon with the Boost bot https://carlchenet.com/automatically-boost-cool-toots-on-mastodon-with-the-boost-bot/ #Mastodon
x en Cryptocurrencies On the New Social Network Mastodon #Mastodon #bitcoin #ethereum #monero
The first field only indicates if the line is the next one to be considered by Remindr, the o indicates the next line to be sent. The second field is the 2-letters code language your content is using, in my example en or fr. Next content on the line will compose the body of your messages to Mastodon and Twitter. So each time you launch Remindr, one of the lines of your file will be sent to Mastodon and Twitter. How easy to use is that? and finally You can help me developing tools for Mastodon and other social networks by donating anything through Liberaypay (also possible with cryptocurrencies). Any contribution will be appreciated. That s a big factor motivation
Donate You also may follow my account @carlchenet on Mastodon Carl Chenet On Mastodon

20 August 2017

Vincent Bernat: IPv6 route lookup on Linux

TL;DR: With its implementation of IPv6 routing tables using radix trees, Linux offers subpar performance (450 ns for a full view 40,000 routes) compared to IPv4 (50 ns for a full view 500,000 routes) but fair memory usage (20 MiB for a full view).
In a previous article, we had a look at IPv4 route lookup on Linux. Let s see how different IPv6 is.

Lookup trie implementation Looking up a prefix in a routing table comes down to find the most specific entry matching the requested destination. A common structure for this task is the trie, a tree structure where each node has its parent as prefix. With IPv4, Linux uses a level-compressed trie (or LPC-trie), providing good performances with low memory usage. For IPv6, Linux uses a more classic radix tree (or Patricia trie). There are three reasons for not sharing:
  • The IPv6 implementation (introduced in Linux 2.1.8, 1996) predates the IPv4 implementation based on LPC-tries (in Linux 2.6.13, commit 19baf839ff4a).
  • The feature set is different. Notably, IPv6 supports source-specific routing1 (since Linux 2.1.120, 1998).
  • The IPv4 address space is denser than the IPv6 address space. Level-compression is therefore quite efficient with IPv4. This may not be the case with IPv6.
The trie in the below illustration encodes 6 prefixes: Radix tree For more in-depth explanation on the different ways to encode a routing table into a trie and a better understanding of radix trees, see the explanations for IPv4. The following figure shows the in-memory representation of the previous radix tree. Each node corresponds to a struct fib6_node. When a node has the RTN_RTINFO flag set, it embeds a pointer to a struct rt6_info containing information about the next-hop. Memory representation of a routing table The fib6_lookup_1() function walks the radix tree in two steps:
  1. walking down the tree to locate the potential candidate, and
  2. checking the candidate and, if needed, backtracking until a match.
Here is a slightly simplified version without source-specific routing: 
static struct fib6_node *fib6_lookup_1(struct fib6_node *root,
                                       struct in6_addr  *addr)
 
    struct fib6_node *fn;
    __be32 dir;
    /* Step 1: locate potential candidate */
    fn = root;
    for (;;)  
        struct fib6_node *next;
        dir = addr_bit_set(addr, fn->fn_bit);
        next = dir ? fn->right : fn->left;
        if (next)  
            fn = next;
            continue;
         
        break;
     
    /* Step 2: check prefix and backtrack if needed */
    while (fn)  
        if (fn->fn_flags & RTN_RTINFO)  
            struct rt6key *key;
            key = fn->leaf->rt6i_dst;
            if (ipv6_prefix_equal(&key->addr, addr, key->plen))  
                if (fn->fn_flags & RTN_RTINFO)
                    return fn;
             
         
        if (fn->fn_flags & RTN_ROOT)
            break;
        fn = fn->parent;
     
    return NULL;

Caching While IPv4 lost its route cache in Linux 3.6 (commit 5e9965c15ba8), IPv6 still has a caching mechanism. However cache entries are directly put in the radix tree instead of a distinct structure. Since Linux 2.1.30 (1997) and until Linux 4.2 (commit 45e4fd26683c), almost any successful route lookup inserts a cache entry in the radix tree. For example, a router forwarding a ping between 2001:db8:1::1 and 2001:db8:3::1 would get those two cache entries: 
$ ip -6 route show cache
2001:db8:1::1 dev r2-r1  metric 0
    cache
2001:db8:3::1 via 2001:db8:2::2 dev r2-r3  metric 0
    cache
These entries are cleaned up by the ip6_dst_gc() function controlled by the following parameters: 
$ sysctl -a   grep -F net.ipv6.route
net.ipv6.route.gc_elasticity = 9
net.ipv6.route.gc_interval = 30
net.ipv6.route.gc_min_interval = 0
net.ipv6.route.gc_min_interval_ms = 500
net.ipv6.route.gc_thresh = 1024
net.ipv6.route.gc_timeout = 60
net.ipv6.route.max_size = 4096
net.ipv6.route.mtu_expires = 600
The garbage collector is triggered at most every 500 ms when there are more than 1024 entries or at least every 30 seconds. The garbage collection won t run for more than 60 seconds, except if there are more than 4096 routes. When running, it will first delete entries older than 30 seconds. If the number of cache entries is still greater than 4096, it will continue to delete more recent entries (but no more recent than 512 jiffies, which is the value of gc_elasticity) after a 500 ms pause. Starting from Linux 4.2 (commit 45e4fd26683c), only a PMTU exception would create a cache entry. A router doesn t have to handle those exceptions, so only hosts would get cache entries. And they should be pretty rare. Martin KaFai Lau explains:
Out of all IPv6 RTF_CACHE routes that are created, the percentage that has a different MTU is very small. In one of our end-user facing proxy server, only 1k out of 80k RTF_CACHE routes have a smaller MTU. For our DC traffic, there is no MTU exception.
Here is how a cache entry with a PMTU exception looks like: 
$ ip -6 route show cache
2001:db8:1::50 via 2001:db8:1::13 dev out6  metric 0
    cache  expires 573sec mtu 1400 pref medium

Performance We consider three distinct scenarios:
Excerpt of an Internet full view
In this scenario, Linux acts as an edge router attached to the default-free zone. Currently, the size of such a routing table is a little bit above 40,000 routes.
/48 prefixes spread linearly with different densities
Linux acts as a core router inside a datacenter. Each customer or rack gets one or several /48 networks, which need to be routed around. With a density of 1, /48 subnets are contiguous.
/128 prefixes spread randomly in a fixed /108 subnet
Linux acts as a leaf router for a /64 subnet with hosts getting their IP using autoconfiguration. It is assumed all hosts share the same OUI and therefore, the first 40 bits are fixed. In this scenario, neighbor reachability information for the /64 subnet are converted into routes by some external process and redistributed among other routers sharing the same subnet2.

Route lookup performance With the help of a small kernel module, we can accurately benchmark3 the ip6_route_output_flags() function and correlate the results with the radix tree size: Maximum depth and lookup time Getting meaningful results is challenging due to the size of the address space. None of the scenarios have a fallback route and we only measure time for successful hits4. For the full view scenario, only the range from 2400::/16 to 2a06::/16 is scanned (it contains more than half of the routes). For the /128 scenario, the whole /108 subnet is scanned. For the /48 scenario, the range from the first /48 to the last one is scanned. For each range, 5000 addresses are picked semi-randomly. This operation is repeated until we get 5000 hits or until 1 million tests have been executed. The relation between the maximum depth and the lookup time is incomplete and I can t explain the difference of performance between the different densities of the /48 scenario. We can extract two important performance points:
  • With a full view, the lookup time is 450 ns. This is almost ten times the budget for forwarding at 10 Gbps which is about 50 ns.
  • With an almost empty routing table, the lookup time is 150 ns. This is still over the time budget for forwarding at 10 Gbps.
With IPv4, the lookup time for an almost empty table was 20 ns while the lookup time for a full view (500,000 routes) was a bit above 50 ns. How to explain such a difference? First, the maximum depth of the IPv4 LPC-trie with 500,000 routes was 6, while the maximum depth of the IPv6 radix tree for 40,000 routes is 40. Second, while both IPv4 s fib_lookup() and IPv6 s ip6_route_output_flags() functions have a fixed cost implied by the evaluation of routing rules, IPv4 has several optimizations when the rules are left unmodified5. Those optimizations are removed on the first modification. If we cancel those optimizations, the lookup time for IPv4 is impacted by about 30 ns. This still leaves a 100 ns difference with IPv6 to be explained. Let s compare how time is spent in each lookup function. Here is a CPU flamegraph for IPv4 s fib_lookup(): IPv4 route lookup flamegraph Only 50% of the time is spent in the actual route lookup. The remaining time is spent evaluating the routing rules (about 30 ns). This ratio is dependent on the number of routes we inserted (only 1000 in this example). It should be noted the fib_table_lookup() function is executed twice: once with the local routing table and once with the main routing table. The equivalent flamegraph for IPv6 s ip6_route_output_flags() is depicted below: IPv6 route lookup flamegraph Here is an approximate breakdown on the time spent:
  • 50% is spent in the route lookup in the main table,
  • 15% is spent in handling locking (IPv4 is using the more efficient RCU mechanism),
  • 5% is spent in the route lookup of the local table,
  • most of the remaining is spent in routing rule evaluation (about 100 ns)6.
Why does the evaluation of routing rules is less efficient with IPv6? Again, I don t have a definitive answer.

History The following graph shows the performance progression of route lookups through Linux history: IPv6 route lookup performance progression All kernels are compiled with GCC 4.9 (from Debian Jessie). This version is able to compile older kernels as well as current ones. The kernel configuration is the default one with CONFIG_SMP, CONFIG_IPV6, CONFIG_IPV6_MULTIPLE_TABLES and CONFIG_IPV6_SUBTREES options enabled. Some other unrelated options are enabled to be able to boot them in a virtual machine and run the benchmark. There are three notable performance changes:
  • In Linux 3.1, Eric Dumazet delays a bit the copy of route metrics to fix the undesirable sharing of route-specific metrics by all cache entries (commit 21efcfa0ff27). Each cache entry now gets its own metrics, which explains the performance hit for the non-/128 scenarios.
  • In Linux 3.9, Yoshifuji Hideaki removes the reference to the neighbor entry in struct rt6_info (commit 887c95cc1da5). This should have lead to a performance increase. The small regression may be due to cache-related issues.
  • In Linux 4.2, Martin KaFai Lau prevents the creation of cache entries for most route lookups. The most sensible performance improvement comes with commit 4b32b5ad31a6. The second one is from commit 45e4fd26683c, which effectively removes creation of cache entries, except for PMTU exceptions.

Insertion performance Another interesting performance-related metric is the insertion time. Linux is able to insert a full view in less than two seconds. For some reason, the insertion time is not linear above 50,000 routes and climbs very fast to 60 seconds for 500,000 routes. Insertion time Despite its more complex insertion logic, the IPv4 subsystem is able to insert 2 million routes in less than 10 seconds.

Memory usage Radix tree nodes (struct fib6_node) and routing information (struct rt6_info) are allocated with the slab allocator7. It is therefore possible to extract the information from /proc/slabinfo when the kernel is booted with the slab_nomerge flag: 
# sed -ne 2p -e '/^ip6_dst/p' -e '/^fib6_nodes/p' /proc/slabinfo   cut -f1 -d:
   name            <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab>
fib6_nodes         76101  76104     64   63    1
ip6_dst_cache      40090  40090    384   10    1
In the above example, the used memory is 76104 64+40090 384 bytes (about 20 MiB). The number of struct rt6_info matches the number of routes while the number of nodes is roughly twice the number of routes: Nodes The memory usage is therefore quite predictable and reasonable, as even a small single-board computer can support several full views (20 MiB for each): Memory usage The LPC-trie used for IPv4 is more efficient: when 512 MiB of memory is needed for IPv6 to store 1 million routes, only 128 MiB are needed for IPv4. The difference is mainly due to the size of struct rt6_info (336 bytes) compared to the size of IPv4 s struct fib_alias (48 bytes): IPv4 puts most information about next-hops in struct fib_info structures that are shared with many entries.

Conclusion The takeaways from this article are:
  • upgrade to Linux 4.2 or more recent to avoid excessive caching,
  • route lookups are noticeably slower compared to IPv4 (by an order of magnitude),
  • CONFIG_IPV6_MULTIPLE_TABLES option incurs a fixed penalty of 100 ns by lookup,
  • memory usage is fair (20 MiB for 40,000 routes).
Compared to IPv4, IPv6 in Linux doesn t foster the same interest, notably in term of optimizations. Hopefully, things are changing as its adoption and use at scale are increasing.
  1. For a given destination prefix, it s possible to attach source-specific prefixes: 
    ip -6 route add 2001:db8:1::/64 \
  from 2001:db8:3::/64 \
  via fe80::1 \
  dev eth0
    Lookup is first done on the destination address, then on the source address.
  2. This is quite different of the classic scenario where Linux acts as a gateway for a /64 subnet. In this case, the neighbor subsystem stores the reachability information for each host and the routing table only contains a single /64 prefix.
  3. The measurements are done in a virtual machine with one vCPU and no neighbors. The host is an Intel Core i5-4670K running at 3.7 GHz during the experiment (CPU governor set to performance). The benchmark is single-threaded. Many lookups are performed and the result reported is the median value. Timings of individual runs are computed from the TSC.
  4. Most of the packets in the network are expected to be routed to a destination. However, this also means the backtracking code path is not used in the /128 and /48 scenarios. Having a fallback route gives far different results and make it difficult to ensure we explore the address space correctly.
  5. The exact same optimizations could be applied for IPv6. Nobody did it yet.
  6. Compiling out table support effectively removes those last 100 ns.
  7. There is also per-CPU pointers allocated directly (4 bytes per entry per CPU on a 64-bit architecture). We ignore this detail.

13 August 2017

Enrico Zini: Consensually doing things together?

On 2017-08-06 I have a talk at DebConf17 in Montreal titled "Consensually doing things together?" (video). Here are the talk notes. Abstract At DebConf Heidelberg I talked about how Free Software has a lot to do about consensually doing things together. Is that always true, at least in Debian? I d like to explore what motivates one to start a project and what motivates one to keep maintaining it. What are the energy levels required to manage bits of Debian as the project keeps growing. How easy it is to say no. Whether we have roles in Debian that require irreplaceable heroes to keep them going. What could be done to make life easier for heroes, easy enough that mere mortals can help, or take their place. Unhappy is the community that needs heroes, and unhappy is the community that needs martyrs. I d like to try and make sure that now, or in the very near future, Debian is not such an unhappy community. Consensually doing things together I gave a talk in Heidelberg. Valhalla made stickers Debian France distributed many of them. There's one on my laptop. Which reminds me of what we ought to be doing. Of what we have a chance to do, if we play our cards right. I'm going to talk about relationships. Consensual relationships. Relationships in short. Nonconsensual relationships are usually called abuse. I like to see Debian as a relationship between multiple people. And I'd like it to be a consensual one. I'd like it not to be abuse. Consent From wikpedia:
In Canada "consent means the voluntary agreement of the complainant to engage in sexual activity" without abuse or exploitation of "trust, power or authority", coercion or threats.[7] Consent can also be revoked at any moment.[8] There are 3 pillars often included in the description of sexual consent, or "the way we let others know what we're up for, be it a good-night kiss or the moments leading up to sex." They are:
  • Knowing exactly what and how much I'm agreeing to
  • Expressing my intent to participate
  • Deciding freely and voluntarily to participate[20]
Saying "I've decided I won't do laundry anymore" when the other partner is tired, or busy doing things. Is different than saying "I've decided I won't do laundry anymore" when the other partner has a chance to say "why? tell me more" and take part in negotiation. Resources: Relationships Debian is the Universal Operating System. Debian is made and maintained by people. The long term health of debian is a consequence of the long term health of the relationship between Debian contributors. Debian doesn't need to be technically perfect, it needs to be socially healthy. Technical problems can be fixed by a healty community. graph showing relationship between avoidance, accomodation, compromise, competition, collaboration The Thomas-Kilmann Conflict Mode Instrument: source png. Motivations Quick poll: What are your motivations to be in a relationship? Which of those motivations are healthy/unhealthy? "Galadriel" (noun, by Francesca Ciceri): a task you have to do otherwise Sauron takes over Middle Earth See: http://blog.zouish.org/nonupdd/#/22/1 What motivates me to start a project or pick one up? What motivates me to keep maintaning a project? What motivates you? What's an example of a sustainable motivation? Is it really all consensual in Debian? Energy Energy that thing which is measured in spoons. The metaphore comes from people suffering with chronic health issues:
"Spoons" are a visual representation used as a unit of measure used to quantify how much energy a person has throughout a given day. Each activity requires a given number of spoons, which will only be replaced as the person "recharges" through rest. A person who runs out of spoons has no choice but to rest until their spoons are replenished.
For example, in Debian, I could spend: What is one person capable of doing? Have reasonable expectations, on others: Have reasonable expectations, on yourself: Debian is a shared responsibility When spoons are limited, what takes more energy tends not to get done As the project grows, project-wide tasks become harder Are they still humanly achievable? I don't want Debian to have positions that require hero-types to fill them Dictatorship of who has more spoons: Perfectionism You are in a relationship that is just perfect. All your friends look up to you. You give people relationship advice. You are safe in knowing that You Are Doing It Right. Then one day you have an argument in public. You don't just have to deal with the argument, but also with your reputation and self-perception shattering. One things I hate about Debian: consistent technical excellence. I don't want to be required to always be right. One of my favourite moments in the history of Debian is the openssl bug Debian doesn't need to be technically perfect, it needs to be socially healthy, technical problems can be fixed. I want to remove perfectionism from Debian: if we discover we've been wrong all the time in something important, it's not the end of Debian, it's the beginning of an improved Debian. Too good to be true There comes a point in most people's dating experience where one learns that when some things feel too good to be true, they might indeed be. There are people who cannot say no: There are people who cannot take a no: Note the diversity statement: it's not a problem to have one of those (and many other) tendencies, as long as one manages to keep interacting constructively with the rest of the community Also, it is important to be aware of these patterns, to be able to compensate for one's own tendencies. What happens when an avoidant person meets a narcissistic person, and they are both unaware of the risks? Resources: Note: there are problems with the way these resources are framed: Red flag / green flag http://pervocracy.blogspot.ca/2012/07/green-flags.html Ask for examples of red/green flags in Debian. Green flags: Red flags: Apologies / Dealing with issues I don't see the usefulness of apologies that are about accepting blame, or making a person stop complaining. I see apologies as opportunities to understand the problem I caused, help fix it, and possibly find ways of avoiding causing that problem again in the future. A Better Way to Say Sorry lists a 4 step process, which is basically what we do when in bug reports already: 1, Try to understand and reproduce the exact problem the person had. 2. Try to find the cause of the issue. 3. Try to find a solution for the issue. 4. Verify with the reporter that the solution does indeed fix the issue. This is just to say
My software ate
the files
that where in
your home directory and which
you were probably
needing
for work Forgive me
it was so quick to write
without tests
and it worked so well for me
(inspired by a 1934 poem by William Carlos Williams) Don't be afraid to fail Don't be afraid to fail or drop the ball. I think that anything that has a label attached of "if you don't do it, nobody will", shouldn't fall on anybody's shoulders and should be shared no matter what. Shared or dropped. Share the responsibility for a healthy relationship Don't expect that the more experienced mates will take care of everything. In a project with active people counted by the thousand, it's unlikely that harassment isn't happening. Is anyone writing anti-harassment? Do we have stats? Is having an email address and a CoC giving us a false sense of security?
When you get involved in a new community, such as Debian, find out early where, if that happens, you can find support, understanding, and help to make it stop. If you cannot find any, or if the only thing you can find is people who say "it never happens here", consider whether you really want to be in that community.
(from http://www.enricozini.org/blog/2016/debian/you-ll-thank-me-later/)
There are some nice people in the world. I mean nice people, the sort I couldn t describe myself as. People who are friends with everyone, who are somehow never involved in any argument, who seem content to spend their time drawing pictures of bumblebees on flowers that make everyone happy. Those people are great to have around. You want to hold onto them as much as you can. But people only have so much tolerance for jerkiness, and really nice people often have less tolerance than the rest of us. The trouble with not ejecting a jerk whether their shenanigans are deliberate or incidental is that you allow the average jerkiness of the community to rise slightly. The higher it goes, the more likely it is that those really nice people will come around less often, or stop coming around at all. That, in turn, makes the average jerkiness rise even more, which teaches the original jerk that their behavior is acceptable and makes your community more appealing to other jerks. Meanwhile, more people at the nice end of the scale are drifting away.
(from https://eev.ee/blog/2016/07/22/on-a-technicality/) Give people freedom If someone tries something in Debian, try to acknowledge and accept their work. You can give feedback on what they are doing, and try not to stand in their way, unless what they are doing is actually hurting you. In that case, try to collaborate, so that you all can get what you need. It's ok if you don't like everything that they are doing. I personally don't care if people tell me I'm good when I do something, I perceive it a bit like "good boy" or "good dog". I rather prefer if people show an interest, say "that looks useful" or "how does it work?" or "what do you need to deploy this?" Acknowledge that I've done something. I don't care if it's especially liked, give me the freedom to keep doing it. Don't give me rewards, give me space and dignity. Rather than feeding my ego, feed by freedom, and feed my possibility to create.

11 August 2017

Mike Gabriel: @DebConf 2017: Ayatana Indicators

On last Tuesday, I gave a 20 min talk about Ayatana Indicators at DebConf 17 in Montreal. Ayatana Indicators Talk The talk had video coverage, so big thanks to the DebConf video team for making it possible to send the below video link around to people in the world: http://meetings-archive.debian.net/pub/debian-meetings/2017/debconf17/ay... The document of notes shown in the video is available on Debian's Infinote (Gobby) server: 
$ sudo apt-get install gobby
$ sudo gobby infinote://gobby.debian.org/debconf17/talk/ayatana-indicators
The major outcome of this talk was getting to know Dimitri John Ledkov from the Foundation Team at Canonical Ltd. We agreed on investigating the following actions, targetting the Ubuntu 18.04 LTS release and later on Debian 10 (aka buster): Upstream Todos Debian/Ubuntu Todos Please get in Touch... As this is going to be quite an effort, esp. if we want to get this done until 18.04 LTS, let me say, that this blog post is a call for help. If you are attached to Ubuntu and have used desktops with indicator support until now, please get in touch with the Ayatana Indicators team upstream as well as downstream (Debian/Ubuntu). Contact: Looking forward to meeting you online or on person and possibly working together with you on this transition project.

Mike Gabriel: @DebConf17: Story Telling about Debian Edu in Northern Germany

Last Monday, I gave a 20min talk about our little FLOSS school project "IT-Zukunft Schule" at the Debian Conference 17 in Montreal. The talk had video coverage, so may want to peek in, if you couldn't manage to watch the life stream: http://meetings-archive.debian.net/pub/debian-meetings/2017/debconf17/su... I'd like to share some major outcomes (so far) of this talk.
  1. I realized how attached I am to "IT-Zukunft Schule" and how much it means to me that our kids grow up in a world of freedom and choice. Also and esp. when it comes to choosing your daily communication tools and computer working environment
  2. I met Foteini Tsiami and Alkis Georgopoulos from Greece. They work on LTSP and have deployed 1000+ schools in Greece with LTSP + Debian GNU/Linux + MATE Desktop Environment
  3. I met Vagrant Cascadian who is the maintainer of LTSP in Debian and also a major LTSP upstream contributor
  4. I received a lot of fine feedback that was very encouraging to go on with our local work in Schleswig-Holstein
If you have some more time for watching DebConf talks on video, I dearly recommend the talk given by Alkis and Foteini on their Greek FLOSS success story. If you don't have that much time, please skip through the video until you are at 26:15 and enjoy the map that shows how much Debian + LTSP has spread over all of Greece. http://meetings-archive.debian.net/pub/debian-meetings/2017/debconf17/lt... Unfortunately, the schools in Greece are so much smaller than schools in Germany. Most schools there have between 50 and 300 students. So at the Greek schools, it is possible to have a teacher machine being the server for one computer lab. This teacher / server machine provides the infrastructure for a room full of LTSP fat clients (no hard drive inside) and that's it. For German schools, unfortunately, we need a larger scale setup. German schools often have 800+ students and network services need to be spread over more than one server machine. So, the current approach with one server running LDAP, Kerberos etc. is quite appropriate, but also extendible, possibly on municipality level or on county level. We (from IT-Zukunft Schule) are quite positive that there will be opportunities for introducing FLOSS approaches more on the county level in Schleswig-Holstein in the near future. So stay tuned...

7 August 2017

Gunnar Wolf: #DebConf17, Montreal An evening out

I have been in Montreal only for a day. Yesterday night, I left DebConf just after I finished presenting the Continuous Key-Signing Party introduction to go out with a long-time friend from Mexico and his family. We went to the Mont Royal park, from where you can have a beautiful city view: What I was most amazed of as a Mexico City dweller is of the sky, of the air... Not just in this picture, but as we arrived, or later when a full moon rose. This city has beautiful air, and a very beautiful view. We later went for dinner to a place I heartfully recommend to other non-vegetarian attendees: Portuguese-style grill. Delicious. Of course, were I to go past it, I'd just drive on (as it had a very long queue waiting to enter). The secret: Do your request on the phone. Make a short queue to pick it up. Have somebody in the group wait for a table, or eat at the nearby Parc Lafontaine. And... Thoroughly enjoy :-) Anyway, I'm leaving for the venue, about to use the Bixi service for the first time. See you guys soon! (if you are at DebConf17, of course. And you should all be here!)
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5 August 2017

Daniel Silverstone: USB Device Stacks, on RTFM, part 2

Previously we talked about all the different kinds of descriptors which USB devices use to communicate their capability. This is important stuff because to write any useful USB device firmware we need to be able to determine how to populate our descriptors. However, having that data on the device is entirely worthless without an understanding of how it gets from the device to the host so that it can be acted upon. To understand that, let's look at the USB wire protocol.
Note, I'll again be talking mostly about USB2.0 low- and full-speed. I believe that high speed is approximately the same but with faster wires, except not quite that simple.

Down to the wire I don't intend to talk about the actual electrical signalling, though it's not un-reasonable for you to know that USB is a pair of wires forming a differentially signalled bidirectional serial communications link. The host is responsible for managing all the framing and timing on the link, and for formatting the communications into packets. There are a number of packet types which can appear on the USB link:
Packet type Purpose
Token Packet When the host wishes to send a message to the Control endpoint to configure the device, read data IN, or write data OUT, it uses this to start the transaction.
Data(0/1) Packet Following a Setup, In, or Out token, a Data packet is a transfer of data (in either direction). The 0 and 1 alternate to provide a measure of confidence against lost packets.
Handshake Packet Following a data packet of some kind, the other end may ACK the packet (all was well), NAK the packet (report that the device cannot, temporarily, send/receive data, or that an interrupt endpoint isn't triggered), or STALL the bus in which case the host needs to intervene.
Start of Frame Every 1ms (full-speed) the host will send a SOF packet which carries a frame number. This can be used to help keep time on very simple devices. It also divides the bus into frames within which bandwidth is allocated.
As an example, when the host wishes to perform a control transfer, the following packets are transacted in turn:
  1. Setup Token - The host addresses the device and endpoint (OUT0)
  2. Data0 Packet - The host transmits a GET_DESCRIPTOR for the device descriptor
  3. Ack Packet - The device acknowledges receipt of the request
This marks the end of the first transaction. The device decodes the GET_DESCRIPTOR request and prepares the device descriptor for transmission. The transmission occurs as the next transaction on the bus. In this example, we're assuming 8 byte maximum transmission sizes, for illustrative purposes.
  1. In Token - The host addresses the device and endpoint (IN0)
  2. Data1 Packet - The device transmits the first 8 bytes of the descriptor
  3. Ack Packet - The host acknowledges the data packet
  4. In Token - The host addresses the device and endpoint (IN0)
  5. Data0 Packet - The device transmits the remaining 4 bytes of the descriptor (padded)
  6. Ack Packet - The host acknowledges the data packet
The second transaction is now complete, and the host has all the data it needs to proceed. Finally a status transaction occurs in which:
  1. Out Token - The host addresses the device and endpoint (OUT0)
  2. Data1 Packet - The host transmits a 0 byte data packet to indicate successful completion
  3. Ack Packet - The device acknowledges the completion, indicating its own satisfaction
And thus ends the full control transaction in which the host retrieves the device descriptor. From a high level, we need only consider the activity which occurs at the point of the acknowledgement packets. In the above example:
  1. On the first ACK the device prepares IN0 to transmit the descriptor, readying whatever low level device stack there is with a pointer to the descriptor and its length in bytes.
  2. On the second ACK the low levels are still thinking.
  3. On the third ACK the transmission from IN0 is complete and the endpoint no longer expects to transfer data.
  4. On the fourth ACK the control transaction is entirely complete.

Thinking at the low levels of the control interface Before we can build a high level USB stack, we need to consider the activity which might occur at the lower levels. At the low levels, particularly of the device control interface, work has to be done at each and every packet. The hardware likely deals with the token packet for us, leaving the data packets for us to process, and the resultant handshake packets will be likely handled by the hardware in response to our processing the data packets. Since every control transaction is initiated by a setup token, let's look at the setup requests which can come our way...
Setup Packet (Data) Format
Field Name Byte start Byte length Encoding Meaning
bmRequestType 0 1 Bitmap Describes the kind of request, and the target of it. See below.
bRequest 1 1 Code The request code itself, meanings of the rest of the fields vary by bRequest
wValue 2 2 Number A 16 bit value whose meaning varies by request type
wIndex 4 2 Number A 16 bit value whose meaning varies by request type but typically encodes an interface number or endpoint.
wLength 6 2 Number A 16 bit value indicating the length of the transfer to come.
Since bRequest is essentially a switch against which multiple kinds of setup packet are selected between, here's the meanings of a few...
GET_DESCRIPTOR (Device) setup packet
Field Name Value Meaning
bmRequestType 0x08 Data direction is IN (from device to host), recipient is the device
bRequest 0x06 GET_DESCRIPTOR (in this instance, the device descriptor is requested)
wValue 0x0001 This means the device descriptor
wIndex 0x0000 Irrelevant, there's only 1 device descriptor anyway
wLength 12 This is the length of a device descriptor (12 bytes)
SET_ADDRESS to set a device's USB address
Field Name Value Meaning
bmRequestType 0x00 Data direction is OUT (from host to device), recipient is the device
bRequest 0x05 SET_ADDRESS (Set the device's USB address)
wValue 0x00nn The address for the device to adopt (max 127)
wIndex 0x0000 Irrelevant for address setting
wLength 0 There's no data transfer expected for this setup operation
Most hardware blocks will implement an interrupt at the point that the Data packet following the Setup packet has been receive. This is typically called receiving a 'Setup' packet and then it's up to the device stack low levels to determine what to do and dispatch a handler. Otherwise an interrupt will fire for the IN or OUT tokens and if the endpoint is zero, the low level stack will handle it once more. One final thing worth noting about SET_ADDRESS is that it doesn't take effect until the completion of the zero-length "status" transaction following the setup transaction. As such, the status request from the host will still be sent to address zero (the default for new devices).

A very basic early "packet trace" This is an example, and is not guaranteed to be the packet sequence in all cases. It's a good indication of the relative complexity involved in getting a fresh USB device onto the bus though... When a device first attaches to the bus, the bus is in RESET state and so the first event a device sees is a RESET which causes it to set its address to zero, clear any endpoints, clear the configuration, and become ready for control transfers. Shortly after this, the device will become suspended. Next, the host kicks in and sends a port reset of around 30ms. After this, the host is ready to interrogate the device. The host sends a GET_DESCRIPTOR to the device, whose address at this point is zero. Using the information it receives from this, it can set up the host-side memory buffers since the device descriptor contains the maximum transfer size which the device supports. The host is now ready to actually 'address' the device, and so it sends another reset to the device, again around 30ms in length. The host sends a SET_ADDRESS control request to the device, telling it that its new address is nn. Once the acknowledgement has been sent from the host for the zero-data status update from the device, the device sets its internal address to the value supplied in the request. From now on, the device shall respond only to requests to nn rather than to zero. At this point, the host will begin interrogating further descriptors, looking at the configuration descriptors and the strings, to build its host-side representation of the device. These will be GET_DESCRIPTOR and GET_STRING_DESCRIPTOR requests and may continue for some time. Once the host has satisfied itself that it knows everything it needs to about the device, it will issue a SET_CONFIGURATION request which basically starts everything up in the device. Once the configuration is set, interrupt endpoints will be polled, bulk traffic will be transferred, Isochronous streams begin to run, etc.

Okay, but how do we make this concrete? So far, everything we've spoken about has been fairly abstract, or at least "soft". But to transfer data over USB does require some hardware. (Okay, okay, we could do it all virtualised, but there's no fun in that). The hardware I'm going to be using for the duration of this series is the STM32 on the blue-pill development board. This is a very simple development board which does (in theory at least) support USB device mode. If we view the schematic for the blue-pill, we can see a very "lightweight" USB interface which has a pullup resistor for D+. This is the way that a device signals to the host that it is present, and that it wants to speak at full-speed. If the pullup were on D- then it would be a low-speed device. High speed devices need a little more complexity which I'm not going to go into for today. The USB lines connect to pins PA11 and PA12 which are the USB pins on the STM32 on the board. Since USB is quite finicky, the STM32 doesn't let you remap that function elsewhere, so this is all looking quite good for us so far. The specific STM32 on the blue-pill is the STM32F103C8T6. By viewing its product page on ST's website we can find the reference manual for the part. Jumping to section 23 we learn that this STM32 supports full-speed USB2.0 which is convenient given the past article and a half. We also learn it supports up to eight endpoints active at any one time, and offers double-buffering for our bulk and isochronous transfers. It has some internal memory for packet buffering, so it won't use our RAM bandwidth while performing transfers, which is lovely. I'm not going to distill the rest of that section here, because there's a large amount of data which explains how the USB macrocell operates. However useful things to note are:
  • How IN OUT and SETUP transfers work.
  • How the endpoint buffer memory is configured.
  • That all bus-powered devices MUST respond to suspend/resume properly
  • That the hardware will prioritise endpoint interrupts for us so that we only need deal with the most pressing item at any given time.
  • There is an 'Enable Function' bit in the address register which must be set or we won't see any transactions at all.
  • How the endpoint registers signal events to the device firmware.
Next time, we're going to begin the process of writing a very hacky setup routine to try and initialise the USB device macrocell so that we can see incoming transactions through the ITM. It should be quite exciting, but given how complex this will be for me to learn, it might be a little while before it comes through.

3 August 2017

Elena 'valhalla' Grandi: Debian Day in Varese

Debian Day in Varese

I'm stuck home instead of being able to go to DebConf, but that doesn't mean that Debian Day will be left uncelebrated!

Since many of the locals are away for the holidays, we of @Gruppo Linux Como and @LIFO aren't going to organize a full day of celebrations, but at the very least we are meeting for a dinner in Varese, at some restaurant that will be open on that date.

Everybody is welcome: to join us please add your name (nickname or identifier of any kind, as long as it fits in the box) on dudle.inf.tu-dresden.de/debday before thursday, August 10th, so that we can
get a reservation at the restaurant.

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