CI & automation: Multi-architecture build of software with Jenkins and Docker

Multi-arch software building and distribution is a complex and time-consuming maintenance task in which maintainer/developer need to compile somehow their software for all supported architectures, often, on a single machine. Automation solution such as Jenkins allows to automatize this task and facilitating continuous integration and continuous delivery. Multi-arch software building on a single machine involves the use of different techniques:

• Cross-build: using a cross-toochain to build the software for each target system. This solution is simple but with the cost of polluting the host system with many toolchains which maybe incompatible one to another. Maintenance and update of these toolchains are complicated to manage.
• Virtualization solutions such as docker address these problem by using a sandboxed/containerized image with all tools necessary to build the software for each target architecture. Docker facilitate the setup, maintenance and update of different building environments using images.

This post introduces the basic steps of setting up an automation server that allows to build and distribute multi-arch software using Jenkins and docker.

How to list supported ciphers suites of a server?

I run into a problem of how to check whether my SSL ciphers suites configuration works correctly on my server.
Basically, with openssl, client can verify if the server supports a particular cipher suite using the following command:

openssl s_client -cipher "$cipher" -CAfile ca/ca.crt -connect server:port
# $cipher is the cipher suite name

So it is possible to automatically test all cipher suites supported by openssl against the server using a simple snippet of Bash, i found such script in this site https://superuser.com/questions/109213/how-do-i-list-the-ssl-tls-cipher-suites-a-particular-website-offers and modify it a little bit. Below is the script:

#!/usr/bin/env bash

# OpenSSL requires the port number.
SERVER=$1
DELAY=1
ciphers=$(openssl ciphers 'ALL:eNULL' | sed -e 's/:/ /g')

echo Obtaining cipher list from $(openssl version).

for cipher in ${ciphers[@]}
do
    echo -n Testing $cipher...
    result=$(echo -n | openssl s_client -cipher "$cipher"  -connect $SERVER 2>&1)
    if [[ "$result" =~ ":error:" ]] ; then
        error=$(echo -n $result | cut -d':' -f6)
        echo NO \($error\)
    else
        if echo $result | grep -q "Verify return code: 0 (ok)"; then
            echo YES
        else
            echo UNKNOWN RESPONSE
            echo $result
         fi
    fi
sleep $DELAY
done

Interfacing Raspberry Pi and LPC1114FN28 via SPI

In one of my previous posts, i mentioned about building a toy car project using Raspberry Pi as the brain and the LPC1114FN28 for low level control. This post describes in detail of this hobby project.

Basically, in this project, the Raspberry Pi (running a minimal version of Debian, not Rasbian) acts as a master that :

1. performs some high level calculation (software algorithm) base on the data it collects from the LPC chip (slave)
2. Issues a control command to the slave chip (LPC) for low level control
3. Reading image from Raspberry Camera for some vision stuffs
4. Takes care of network communication for remote control
5. Implements easily a lot of funny stuffs...

One question: why do not use the Pi to communicate directly with sensor or actuator ?. Although the Pi is a pretty performance system, it lacks some low level feature that we will need in this project, such as ADC for reading analog sensors, precise PWM hardware controller for motor control, etc. Therefore, i decided to used it along with the LPC chip that is more suitable for these low level stuffs.