GitLab Shell

GitLab Shell handles git SSH sessions for GitLab

GitLab Shell handles git SSH sessions for GitLab and modifies the list of authorized keys. GitLab Shell is not a Unix shell nor a replacement for Bash or Zsh.

When you access the GitLab server over SSH then GitLab Shell will:

1. Limits you to predefined git commands (git push, git pull).
2. Call the GitLab Rails API to check if you are authorized, and what Gitaly server your repository is on
3. Copy data back and forth between the SSH client and the Gitaly server

If you access a GitLab server over HTTP(S) you end up in gitlab-workhorse.

An overview of the four cases described above:

1. git pull over ssh -> gitlab-shell -> API call to gitlab-rails (Authorization) -> accept or decline -> establish Gitaly session
2. git push over ssh -> gitlab-shell (git command is not executed yet) -> establish Gitaly session -> (in Gitaly) gitlab-shell pre-receive hook -> API call to gitlab-rails (authorization) -> accept or decline push

Git hooks

The gitlab-shell repository used to also contain the Git hooks that allow GitLab to validate Git pushes (e.g. "is this user allowed to push to this protected branch"). These hooks also trigger events in GitLab (e.g. to start a CI pipeline after a push).

We are in the process of moving these hooks to Gitaly, because Git hooks require direct disk access to Git repositories, and that is only possible on Gitaly servers. It makes no sense to have to install gitlab-shell on Gitaly servers.

As of GitLab 11.10 the actual Git hooks are in the Gitaly repository, but gitlab-shell must still be installed on Gitaly servers because the hooks rely on configuration data (e.g. the GitLab internal API URL) that is not yet available in Gitaly itself. Also see the transition plan.

Code status

Requirements

GitLab shell will always use your system ruby (normally located at /usr/bin/ruby) and will not use the ruby your installed with a ruby version manager (such as RVM). It requires ruby 2.0 or higher. Please uninstall any old ruby versions from your system:

sudo apt-get remove ruby1.8

Download Ruby and compile it with:

mkdir /tmp/ruby && cd /tmp/ruby
curl -L --progress http://cache.ruby-lang.org/pub/ruby/2.1/ruby-2.1.5.tar.gz | tar xz
cd ruby-2.1.5
./configure --disable-install-rdoc
make
sudo make install

To install gitlab-shell you also need a Go compiler version 1.8 or newer. https://golang.org/dl/

Setup

./bin/install
./bin/compile

Check

./bin/check

Keys

Add key:

./bin/gitlab-keys add-key key-782 "ssh-rsa AAAAx321..."

Remove key:

./bin/gitlab-keys rm-key key-23 "ssh-rsa AAAAx321..."

List all keys:

./bin/gitlab-keys list-keys

Remove all keys from authorized_keys file:

./bin/gitlab-keys clear

Git LFS remark

Starting with GitLab 8.12, GitLab supports Git LFS authentication through ssh.

Migration to Go feature flags

We are starting to migrate some features from Ruby to Go. To be able to do this incrementally, we hide the Go implementation behind a feature flag.

To enable a feature, modify migration option in config.yml and ensure enabled is set to true and feature to be enabled is added to features.

It should look something like this:

migration:
  enabled: true
  features: ['discover']

Here are the following features that can be enabled:

• discover
• 2fa_recovery_codes

Configuring using Omnibus

If you're using Omnibus, these features can be enabled by adding something like this to gitlab.rb:

gitlab_shell['migration'] = { enabled: true, features: ['discover', '2fa_recovery_codes'] }

This is equivalent to having this in config.yml:

migration:
  enabled: true
  features: ['discover', '2fa_recovery_codes']

Releasing a new version

GitLab Shell is versioned by git tags, and the version used by the Rails application is stored in GITLAB_SHELL_VERSION.

For each version, there is a raw version and a tag version:

• The raw version is the version number. For instance, 15.2.8.
• The tag version is the raw version prefixed with v. For instance, v15.2.8.

To release a new version of GitLab Shell and have that version available to the Rails application:

1. Update the CHANGELOG with the tag version and the VERSION file with the raw version.
2. Add a new git tag with the tag version.
3. Update GITLAB_SHELL_VERSION in the Rails application to the raw version. (Note: this can be done as a separate MR to that, or in and MR that will make use of the latest GitLab Shell changes.)

Updating VCR fixtures

In order to generate new VCR fixtures you need to have a local GitLab instance running and have next data:

1. gitlab-org/gitlab-test project.
2. SSH key with access to the project and ID 1 that belongs to Administrator.
3. SSH key without access to the project and ID 2.

You also need to modify secret variable at spec/gitlab_net_spec.rb so tests can connect to your local instance.

Contributing

See CONTRIBUTING.md.

License

See LICENSE.