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12 years ago
# Gitian
Read about the project goals at the [project home page](https://gitian.org/).
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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.
## Prerequisites:
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### Gentoo:
layman -a luke-jr # needed for vmbuilder
sudo emerge dev-vcs/git net-misc/apt-cacher-ng app-emulation/vmbuilder dev-lang/ruby
sudo emerge app-emulation/qemu
export KVM=qemu-system-x86_64
### Ubuntu:
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sudo apt-get install git apache2 apt-cacher-ng python-vm-builder ruby
sudo apt-get install qemu-kvm # for KVM mode
sudo apt-get install debootstrap lxc # for LXC mode
### OSX with MacPorts:
sudo port install ruby coreutils
export PATH=$PATH:/opt/local/libexec/gnubin # Needed for sha256sum
#### VirtualBox:
Install virtualbox from http://www.virtualbox.org, and make sure `VBoxManage` is in your `$PATH`.
## Create the base VM for use in further builds
**NOTE:** requires `sudo`, please review the script
### KVM
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bin/make-base-vm
bin/make-base-vm --arch i386
### LXC
bin/make-base-vm --lxc
bin/make-base-vm --lxc --arch i386
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Set the `USE_LXC` environment variable to use `LXC` instead of `KVM`:
export USE_LXC=1
### VirtualBox
Command-line `VBoxManage` must be in your `$PATH`.
#### Setup:
`make-base-vm` cannot yet make VirtualBox virtual machines ( _patches welcome_, it should be possible to use `VBoxManage`, boot-from-network Linux images and PXE booting to do it). So you must either get or manually create VirtualBox machines that:
1. Are named `Gitian-<suite>-<arch>` -- e.g. Gitian-lucid-i386 for a 32-bit, Ubuntu 10 machine.
2. Have a booted-up snapshot named `Gitian-Clean` . The build script resets the VM to that snapshot to get reproducible builds.
3. Has the VM's NAT networking setup to forward port `localhost:2223` on the host machine to port `22` of the VM; e.g.:
```
VBoxManage modifyvm Gitian-lucid-i386 --natpf1 "guestssh,tcp,,2223,,22"
```
The final setup needed is to create an `ssh` key that will be used to login to the virtual machine:
ssh-keygen -t dsa -f var/id_dsa -N ""
ssh -p 2223 ubuntu@localhost 'mkdir -p .ssh && chmod 700 .ssh && cat >> .ssh/authorized_keys' < var/id_dsa.pub
Then log into the vm and copy the `ssh` keys to root's `authorized_keys` file.
ssh -p 2223 ubuntu@localhost
# Now in the vm
sudo bash
mkdir -p .ssh && chmod 700 .ssh && cat ~ubuntu/.ssh/authorized_keys >> .ssh/authorized_keys
Set the `USE_VBOX` environment variable to use `VBOX` instead of `KVM`:
export USE_VBOX=1
## Sanity-testing
If you have everything set-up properly, you should be able to:
PATH=$PATH:$(pwd)/libexec
make-clean-vm --suite lucid --arch i386
# For LXC:
LXC_ARCH=i386 LXC_SUITE=lucid on-target ls -la
# For KVM:
start-target 32 lucid-i386
on-target ls -la
stop-target
## Building
Copy any additional build inputs into a directory named _inputs_.
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Then execute the build using a `YAML` description file (can be run as non-root):
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export USE_LXC=1 # LXC only
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bin/gbuild <package>.yml
or if you need to specify a commit for one of the git remotes:
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bin/gbuild --commit <dir>=<hash> <package>.yml
The resulting report will appear in `result/<package>-res.yml`
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To sign the result, perform:
bin/gsign --signer <signer> --release <release-name> <package>.yml
Where `<signer>` is your signing PGP key ID and `<release-name>` is the name for the current release. This will put the result and signature in the `sigs/<package>/<release-name>`. The `sigs/<package>` directory can be managed through git to coordinate multiple signers.
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After you've merged everybody's signatures, verify them:
bin/gverify --release <release-name> <package>.yml
## Poking around
* Log files are captured to the _var_ directory
* You can run the utilities in libexec by running `PATH="libexec:$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
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## 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 br0 and assumes that the host address is `10.0.2.2`:
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sudo brctl addbr br0
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sudo ifconfig br0 10.0.2.2/24 up
## Tests
Not very extensive, currently.
`python -m unittest discover test`