gitian-builder/README.md

Gitian

Read about the project goals at the "project home page":https://gitian.org/ .

This package can do a deterministic build of a package inside a VM.

Deterministic build inside a VM

This performs a build inside a VM, with deterministic inputs and outputs. If the build script takes care of all sources of non-determinism (mostly caused by timestamps), the result will always be the same. This allows multiple independent verifiers to sign a binary with the assurance that it really came from the source they reviewed.

Synopsis:

Install prereqs:

sudo apt-get install apt-cacher-ng python-vm-builder ruby

If you want to use kvm: sudo apt-get install qemu-kvm

or alternatively, lxc (no need for hardware support): sudo apt-get install debootstrap lxc

Create the base VM for use in further builds (requires sudo, please review the script):

bin/make-base-vm
bin/make-base-vm --arch i386

or for lxc:

bin/make-base-vm --lxc
bin/make-base-vm --lxc --arch i386

Copy any additional build inputs into a directory named inputs.

Then execute the build using a YAML description file (can be run as non-root):

export USE_LXC=1 # LXC only
bin/gbuild <package>.yml

or if you need to specify a commit for one of the git remotes:

bin/gbuild --commit <dir>=<hash> <package>.yml

The resulting report will appear in result/<package>-res.yml

To sign the result, perform:

bin/gsign --signer <signer> --release <release-name> <package>.yml

Where is your signing PGP key ID and is the name for the current release. This will put the result and signature in the sigs//. The sigs/ directory can be managed through git to coordinate multiple signers.

After you've merged everybody's signatures, verify them:

bin/gverify --release <release-name> <package>.yml

Poking around

• Log files are captured to the var directory
• You can run the utilities in libexec by running PATH="libexec:$PATH"
• To start the target VM run start-target 32 lucid-i386 or start-target 64 lucid-amd64
• To ssh into the target run on-target or on-target -u root
• On the target, the build directory contains the code as it is compiled and install contains intermediate libraries
• By convention, the script in <package>.yml starts with any environment setup you would need to manually compile things on the target

TODO:

• disable sudo in target, just in case of a hypervisor exploit
• tar and other archive timestamp setter

LXC tips

bin/gbuild runs lxc-start, which may require root. If you are in the admin group, you can add the following sudoers line to prevent asking for the password every time:

%admin ALL=NOPASSWD: /usr/bin/lxc-start

Recent distributions allow lxc-start to be run by non-priviledged users, so you might be able to rip-out the sudo calls in libexec/*.

If you have a runaway lxc-start command, just use kill -9 on it.

The machine configuration requires access to lxcbr0 and assumes that the host address is 10.0.3.1 . If lxc does not configure lxcbr0 on boot, you can do so manually:

sudo brctl addbr lxcbr0
sudo ifconfig lxcbr0 10.0.3.1/24 up

Tests

Not very extensive, currently.

python -m unittest discover test