Git dissect

P2P internals - episode 4

   |  Sébastien Blin

It’s been a long time since my previous post, but let’s continue this serie about distributed systems with a tool that a lot of people use every day: git. Git is a versioning tool. Unlike some systems like subversion, you don’t need to have a server to use git. Every member of the project own a (partial or not) copy of the project and can directly send data to another member. [Read More]
p2p  dev  git 

P2P internals - episode 3

DHT

   |  Sébastien Blin

In the previous articles we talked about how to create a peer to peer connection and what issues we can encounter. These problems are generally due to the NAT which needs methods to pass through it (e.g. TURN servers) or some new protocols (like ICE). It is now time to talk about distributed applications and structures created on top of a p2p network. For a lot of distributed applications, all the nodes in the system can’t be stable. [Read More]
p2p  dev 

P2P internals - episode 2

ICE (RFC 6544, RFC 8445)

   |  Sébastien Blin

In the first article of this series, we saw how to make an application (DEL) which is able to transfer a file from one peer to one another by successfully bypassing the NAT thanks to a TURN server. However, this technique is not really effective, because, in a lot of cases, a TURN server is completely useless. Indeed, if both peers are on the same network or both peers has an IPv6 address, the TURN server is not mandatory. [Read More]
p2p  dev 

Dbus on a server

and without any graphical session

   |  Sébastien Blin

Some time ago, I had to run a script to test an application by sending dbus calls. The script was working great, until I moved it on a server with no graphical session. I ran the script as a System V init script, but you can encounter the same problem in a terminal or in a cron. The thing is that a dbus session is generally managed by KDE, Gnome or your graphical session. [Read More]
software  dbus  quickie 

P2P internals - episode 1

TURN over TCP (RFC 6062)

   |  Sébastien Blin

I love distributed systems for a various of reasons. But these systems are complex and require interactions with many layers. Even if a lot of distributed systems and software exists, such systems can be difficult to use for several reasons. Today, our operating systems tend to avoid doing as many calculations as possible (i.e. mobile devices need to save battery and avoid data consumption). Also, IPv4 is still massively used so NATs are still needed, interfaces are mainly created to interact with servers, etc. [Read More]
p2p  dev 

How to host your own Jitsi instance

A short feedback from experience

   |  Sébastien Blin

For the local future CHATONS (Chatons is a french word which means kitten), I am currently helping to host a new Jitsi-meet instance. This instance will be available at this address: https://conference.facil.services/ and this is a little post about how we did it and what problems we encountered. First step - The manual installation For the story, the first attempt for hosting the instance worked during several weeks. But, after a migration to our final server, we started to see a lot of problems with that instance (due to the migration or the installation of the back-up system or the monitoring tools). [Read More]
free software  devops 

(2/3)Retour du nsec - The visual microphone

   |  Sébastien Blin

Suite de la petite série sur le retour du nsec. Dans ce second article, je vais m’intéresser la dernière partie d’une track en 3 points réalisée par un autre membre de mon équipe. La première partie consistait à trouver la fréquence du mouvement du diaphragme d’un haut parleur. Puis de trouver la musique qui était jouée par cette enceinte (bien entendu, le son n’était pas présent). La dernière partie consistait à retrouver une conversation réalisée dans une pièce où un paquet de chips était filmé à très haute fréquence. [Read More]
ctf  sécurité 

(1/3)Retour du nsec - Introduction au badge hacking

   |  Sébastien Blin

Comme expliqué dans mon précédent billet (https://zestedesavoir.com/contenus/2479/r2-pour-changer-de-gdb/), j’ai participé au NorthSec 2018, une grosse compétition de sécurité en Amérique du Nord. Au final, quelques épreuves valent un article, certaines où je n’ai pas les connaissances (par exemple, pour une épreuve web, il fallait réaliser du Prototype pollution attack) et quelques unes assez drôle. Je vais donc m’attarder sur 3 challenges : Pour la conférence, chaque personne possède un badge contenant le programme de la conférence, des LEDs qui clignotent, des PINS, une interface bluetooth et… 2 FLAGS (cet article). [Read More]
ctf  sécurité 

Tarpaulin ou kcov ?

Outils de couverture de code pour les projets Rust

   |  Sébastien Blin

Pour un projet (que je présenterais plus tard sur le forum), j’ai eu besoin d’avoir du retour sur mes tests. Une des métriques m’intéresse est le pourcentage de couverture, car il me permet de connaître les branches que je n’ai pas encore testé et d’ajouter des scénarios. En cherchant un peu sur Internet, je suis tombé sur 2 outils : kcov tarpaulin En voici un petit comparatif. Comparatif Facilité d’installation kcov wget https://github. [Read More]
programmation  tests  rust