git.md

Our git setup consists of three interdependent services:

• git-rw.torproject.org: ssh accessible and writeable git repositories
• https://git.torproject.org: read-only anonymous access
• https://gitweb.torproject.org/: web browsing repositories

When a developer pushes to git-rw, the repository is mirrored to git and so made available via the gitweb service.

Some repositories are also mirrored to GitLab and we are considering migrating all repositories there. At the time of writing (May 2021), the git infrastructure documented in this wiki page is considered legacy and new repositories should instead be created on GitLab.

• Howto
  • Regular repositories
    • Creating a new repository
    • Adding developers to a repository
    • Deleting accidentally pushed tags/branches
  • User repositories
  • Learning what git repos you can read/write
  • Commit hooks
    • Standard Commit Hooks for Canonical Repositories
  • Migrating a repository to GitLab
    • User part: importing the repository into GitLab
    • TPA part: lock down the repository and add redirections
  • Destroying a repository
  • Mirroring a gitolite repository to GitLab
  • Archiving a repository
  • GitHub and GitLab Mirrors implementation details
  • Pager playbook
    • gitweb out of sync
• Reference
  • Design
  • GitLab migration
    • Security concerns
    • Migration roadmap
  • Issues

Howto

Regular repositories

Creating a new repository

Creating a new top-level repository is not something that should be done often. The top-level repositories are all shown on the gitweb, and we'd like to keep the noise down. If you're not sure if you need a top-level repository then perhaps request a user repository first, and use that until you know you need a top-level repository.

Some projects, for example pluggable-transports, have a path hierarchy for their repositories. This should be encouraged to help keep this organised.

A request for a new top-level repository should include: the users that should have access to it, the repository name (including any folder it should live in), and a short description. If the users that should have access to this repository should be kept in sync with some other repository, a group might be created or re-used as part of the request.

For example:

Please create a new repository metrics/awesome-pipeline.git.

This should be accessible by the same set of users that have access to the
metrics-cloud repository.

The description for the repository is: Tor Metrics awesome pipeline repository.

This message was signed for trac.torproject.org on 2018-10-16 at 19:00:00 UTC.

The git team may ask for additional information to clarify the request if necessary, and may ask for replies to that information to be signed if they would affect the access to the repository. In the case that replies are to be signed, include the ticket number in the signed text to avoid replay attacks.

The git team member will edit the gitolite configuration to add a new block (alphabetically sorted within the configuration file) that looks like the following:

repo metrics-cloud
    RW                                       = @metrics-cloud
    config hooks.email-enabled               = true
    config hooks.mailinglist                 = tor-commits@lists.torproject.org
    config hooks.irc-enabled                 = true
    config hooks.ircproject                  = or
    config hooks.githuburl                   = torproject/metrics-cloud
    config hooks.gitlaburl                   = torproject/metrics/metrics-cloud
metrics-cloud "The Tor Project" = "Configurations for Tor Metrics cloud orchestration"

Deconstructing this:

repo metrics-cloud

Starts a repository block.

    RW                                       = @metrics-cloud

Allows non-destructive read/write but not branch/tag deletion or non-fast-forward pushes. Alternatives would include "R" for read-only, or "RW+" to allow for destructive actions. We only allow destructive actions for user's personal repositories.

In this case, the permissions are delegated to a group (starting with @) and not an individual user.

    config hooks.email-enabled               = true
    config hooks.mailinglist                 = tor-commits@lists.torproject.org

This enables the email hook to send one email per commit to the commits list. For all top-level repositories, the mailing list should be tor-commits@lists.torproject.org.

    config hooks.irc-enabled                 = true
    config hooks.ircproject                  = or

This enables the IRC hook to send one message per commit to an IRC channel. If the project is set to "or" the messages will be sent to #tor-bots.

    config hooks.githuburl                   = torproject/metrics-cloud
    config hooks.gitlaburl                   = torproject/metrics/metrics-cloud

These enable pushing a mirror to external services. The external service will have to be configured to accept these pushes, and we should avoid adding mirror URLs where things aren't configured yet so we don't trigger any IPS or abuse detection system by making loads of bad push attempts.

metrics-cloud "The Tor Project" = "Configurations for Tor Metrics cloud orchestration"

The last line of this file is what is used to provide configuration to gitweb. Starting with the path, then the owner, then the short description.

Upon push, the new repository will be created. It may take some minutes to appear on the gitweb. Do not fear, the old list that did not yet include the new repository has just been cached.

Push takes ages. Don't Ctrl-C it or you can end up in an inconsistent state. Just let it run. A future git team member might work on backgrounding the sync task.

Groups are defined at the top of the file, again in alphabetical order (not part of the repository block):

@metrics-cloud                               = karsten irl

Adding developers to a repository

If you want access to an existing repository please have somebody who already has access to ask that you be added by filing a trac ticket. This should be GPG signed as above.

Request a user be added to an existing repository

The git team member will either add a permissions line to the configuration for the repository or will add a username to the group, depending on how the repository is configured.

Deleting accidentally pushed tags/branches

These requests are for a destructive action and should be signed. You should also sanity check the request and not just blindly copy/paste the list of branch names.

The git team member will need to:

1. Edit the gitolite configuration to allow RW+ access for the specified branch or tag.
2. Push an empty reference to the remote reference to delete it. In doing this, all the hooks will run ensuring that the gitweb mirror and all other external mirrors are kept in sync.
3. Revert the commit that gave the git team member this access.

The additional permission line will look something like:

    RW+ refs/heads/travis-ci                = irl
    RW+ refs/tags/badtag-v1.0               = irl

This is to protect the git team member from accidentally deleting everything, do not just give yourself RW+ permissions for the whole repository unless you are feeling brave, even when someone has accidentally pushed their entire history of personal branches to the canonical repository.

User repositories

Developers who have a tpo LDAP account can request personal git repositories be created on our git infrastructure. Please file a ticket in Trac using the link below. User repositories have the path user/<username>/<repository>.git.

Request a new user repository

This request should contain: username, repository name, and a short description. Here is an example where irl is requesting a new example repository:

Please create a new user repository user/irl/example.git.

The description for the repository is: Iain's example repository.

This message was signed for trac.torproject.org on 2018-10-16 at 19:00:00 UTC.

Please use GPG to clearsign this text, it will be checked against the GPG key that you have linked to you in our LDAP. Additionally, ensure that it is wrapped as a code block (within !{{{ }}}).

There have not yet been any cases where user repositories have allowed access by other users than the owner. Let's keep it that way or this will get complicated.

Users will have full access to their own repos and can therefore delete branches, tags, and perform non-fast-forward pushes.

Learning what git repos you can read/write

Once you have an LDAP account and have an ssh key set up for it, run:

ssh git@git-rw.torproject.org

and it will tell you what bits you have on which repos. The first column is who can read (@ for everybody, R for you, blank for not you), and the second column is who can write (@ for everybody, W for you, blank for not you).

Commit hooks

There are a variety of commit hooks that are easy to add for your git repo, ranging from irc notifications to email notifications to github auto-syncing. Clone the gitolite-admin repo and look at the "config hooks" lines for examples. You can request changes by filing a trac ticket as described above, or just request the hooks when you first ask for your repo to be set up.

Hooks are stored in /srv/git.torproject.org/git-helpers on the server.

Standard Commit Hooks for Canonical Repositories

Changes to most repositories are reported to:

• the #tor-bots IRC channel (or #tor-internal for private admin repositories)

• Some repositories have a dedicated mailing list for commits at https://lists.torproject.org

Migrating a repository to GitLab

Moving a repository from Gitolite to GitLab proceeds in two parts. One part can be done by any user with access to GitLab. The second part needs to be done by TPA.

User part: importing the repository into GitLab

This is the part you need to do as a user to move to GitLab:

1. import the Gitolite repository in GitLab:

   • create a new project
   • pick the "Import project" button
   • pick the "Repo by URL" button
   • copy-paste the https://git.torproject.org/... Git Repository URL
   • pick a project name and namespace (should ideally match the original project as close as possible)
   • add a description (again, matching the original from gitweb/gitolite)
   • pick the "Create project" button

   This will import the git repository into a new GitLab project.

2. if the repository is to be archived on GitLab, make it so in Settings -> General -> Advanced -> Archive project

3. file a ticket with TPA to request a redirection. make sure you mention both the path to the gitolite and GitLab repositories

That's it, you are done! The remaining steps will be executed by TPA.

Note that you can migrate multiple repositories at once by following those steps multiple times. In that case, create a single ticket for TPA with the before/after names, and how they should be handled.

For example, here's the table of repositories migrated by the applications team:

Gitolite	GitLab	fate
builders/tor-browser-build	tpo/applications/tor-browser-build	migrated
builders/rbm	tpo/applications/rbm	migrated
tor-android-service	tpo/applications/tor-android-service	migrated
tor-browser	tpo/applications/tor-browser	migrated
tor-browser-spec	tpo/applications/tor-browser-spec	migrated
tor-launcher	tpo/applications/tor-launcher	archived
torbutton	tpo/applications/torbutton	archived

The above shows 5 repositories that have been migrated to GitLab and are still active, two that have be migrated and archived. There's a third possible fate that is "destroy" in which case TPA will simply mark the repository as inactive and will not migrate it.

Note the verb tense matters here: if the repository is marked as "migrated" or "archived", TPA will assume the repository has already been migrated and/or archived! It is your responsibility to do that migration, unless otherwise noted.

So if you do want TPA to actually migrate the repositories for you, please make that explicit in the issue and use the proper verb tenses.

See issue tpo/tpa/team#41181 for an example issue as well, although that one doesn't use the proper verb tenses

TPA part: lock down the repository and add redirections

This part handles the server side of things. It will install a pre-receive hook in the Git repository to forbid pushes, redirections in the Git web interfaces, and document the change in gitolite.

It assumes the repository has already been migrated.

1. (optional) triage the ticket with the labels ~Git and ~Gitweb, and the milestone %legacy Git infrastructure retirement (TPA-RFC-36)

2. make an (executable) pre-receive hook in git-rw with an exit status of 1 warning about the new code location, this can be done with this Fabric command:

   fab -H cupani.torproject.org gitolite.migrate-repo pluggable-transports/goptlib tpo/anti-censorship/pluggable-transports/goptlib --issue-url=https://gitlab.torproject.org/tpo/tpa/team/-/issues/41182

3. in Puppet, add a line for this project in modules/profile/files/git/gitolite2gitlab.txt (in tor-puppet.git), for example:

   pluggable-transports/goptlib tpo/anti-censorship/pluggable-transports/goptlib

   the Fabric task should already have done this for you.

4. in Gitolite, mark the project as "Migrated to GitLab", for example

   @@ -715,7 +715,7 @@ repo debian/goptlib
        config hooks.irc-enabled                 = true
        config hooks.ircproject                  = or
        config hooks.projectname                 = debian-goptlib
   -    config gitweb.category                   = Packaging
   +    config gitweb.category                   = Migrated to GitLab
    debian/goptlib "The Tor Project" = "Debian packaging for the goptlib pluggable transport library"
    
    repo debian/torproject-keyring

Destroying a repository

Instead of migrating a repository to GitLab, you might want to simply get rid of it. This can be relevant in case the repository is a duplicate, or it's a fork and all branches were merged, for example.

We generally prefer to archive repositories that said, so in general you should follow the migration procedure instead.

To destroy a repository:

1. file a ticket with TPA to request the destruction of the repository or repositories. make sure to explain why you believe the repositories can be destroyed.

2. if you're not TPA, you're done, wait for a response or requests for clarification. the rest of this procedure is relevant only for TPA

3. if you're TPA, examine the request thoroughly. make sure that:

   1. the GitLab user requesting the destruction has access to the Gitolite repository. normally, usernames should generally match as LDAP users were imported when GitLab was created, but it's good to watch out for homograph attacks, for example

   2. there's a reasonable explanation for the destruction, e.g. that no important data will actually be lost when the repository is destroyed

4. install a redirection and schedule destruction of the repository, with the command:

   fab -H cupani.torproject.org gitolite.destroy-repo --issue-url=$URL $REPOSITORY

   for example, this is how the user/nickm/githax repository was disabled and scheduled for destruction:

   anarcat@angela:tsa-misc$ fab -H cupani.torproject.org gitolite.destroy-repo --issue-url='https://gitlab.torproject.org/tpo/tpa/team/-/issues/41189' user/nickm/githax
   INFO: preparing destroying of Gitolite repository user/nickm/githax in /srv/git.torproject.org/repositories/user/nickm/githax.git
   INFO: uploading 468 bytes to /srv/git.torproject.org/repositories/user/nickm/githax.git/hooks/pre-receive
   INFO: making /srv/git.torproject.org/repositories/user/nickm/githax.git/hooks/pre-receive executable
   INFO: scheduling destruction of /srv/git.torproject.org/repositories/user/nickm/githax.git in 30 days on cupani.torproject.org
   INFO: scheduling rm -rf "/srv/git.torproject.org/repositories/user/nickm/githax.git" to run on cupani.torproject.org in 30 days
   warning: commands will be executed using /bin/sh
   job 2 at Sat Jul  8 14:57:00 2023
   INFO: scheduling destruction of /srv/gitweb.torproject.org/repositories/user/nickm/githax.git in 30 days on vineale.torproject.org
   INFO: scheduling rm -rf "/srv/gitweb.torproject.org/repositories/user/nickm/githax.git" to run on cupani.torproject.org in 30 days
   warning: commands will be executed using /bin/sh
   job 3 at Sat Jul  8 14:57:00 2023
   INFO: now modify gitolite.conf to add "config gitweb.category = Scheduled for destruction"

5. as noted in the last line, change the gitolite.conf file to move the project to the Scheduled for destruction category

Mirroring a gitolite repository to GitLab

This procedure is DEPRECATED. Instead, consider migrating the repository to GitLab permanently or simply destroying the repository if its data is worthless.

This procedure is kept for historical purposes only.

1. import the Gitolite repository in GitLab:

   • create a new project
   • pick the "Import project" button
   • pick the "Repo by URL" button
   • copy-paste the https://git.torproject.org/... Git Repository URL
   • pick a project name and namespace (should ideally match the original project as close as possible)
   • add a description (again, matching the original from gitweb/gitolite)
   • pick the "Create project" button

   This will import the git repository into a new GitLab project.

2. grant Developer access to the gitolite-merge-bot user in the project

3. in Gitolite, add the GitLab project URL to enable the mirror hook, for example:

   modified   conf/gitolite.conf
   @@ -1502,6 +1502,7 @@ repo translation
        RW+                                      = emmapeel
        config hooks.irc-enabled                 = true
        config hooks.ircproject                  = or
   +    config hooks.gitlaburl                   = tpo/web/translation
    translation "The Tor Project" = "Translations, one branch per project"
    
    repo translation-tools

   In that example, the translation.git repository will push to the tpo/web/translation mirror.

Archiving a repository

IMPORTANT: this procedure is DEPRECATED. Repositories archived on Gitolite still will be migrated to GitLab, follow the migration procedure instead. Note that even repositories that should be archived in Gitolite MUST be migrated to GitLab and then archived.

If a repository is not to be migrated or mirrored to GitLab (see below) but just archived, use the following procedure.

4. make an (executable) pre-receive hook in git-rw with an exit status of 1 warning about the new code location, example:

   $ cat /srv/git.torproject.org/repositories/project/help/wiki.git/hooks/pre-receive 
   #!/bin/sh
   
   cat <<EOF
   This repository has been archived and should not be used anymore.
   
   See this issue for details:
   
   https://gitlab.torproject.org/tpo/tpa/services/-/issues/TODO
   EOF
   
   exit 1

5. Make sure the hook is executable:

   chmod +x hooks/pre-receive

6. in Gitolite, make the project part of the "Attic", for example

   repo project/foo
        RW                                       = anarcat
   -    config gitweb.category                   = Old category
   -project/foo "The Tor Project" = "foo project"
   +    config gitweb.category                   = Attic
   +project/foo "The Tor Project" = "foo project (deprecated)"
    
    repo project/bar
        RW                                       = @jenkins-admins

The description file in the repository should also be updated similarly.

GitHub and GitLab Mirrors implementation details

Some repositories are mirrored to https://github.com/torproject organization and to the https://gitlab.torproject.org/ server, through gitolite hooks. See above on how to migrate and mirror such repositories to GitLab.

This used to be through a git push --mirror $REMOTE command, but now we do a git push --force $REMOTE '+refs/*:refs/*', because the --mirror argument was destroying merge requests on the GitLab side. This, for example, is what you get with --mirror:

user@tor-dev:~/src/gitlab.torproject.org/xxx/xxx$ git push --mirror git@gitlab.torproject.org:ahf/test-push-mirror.git --dry-run
To gitlab.torproject.org:ahf/test-push-mirror.git
   dd75357..964d4c0  master -> master
 - [deleted]         test-branch
 - [deleted]         refs/merge-requests/1/head
 - [deleted]         refs/merge-requests/1/merge

This is exactly what we want to avoid: it correctly moves the master branch forward, but the mirroring deletes the refs/merge-requests/* content at the destination.

Instead with just --force:

user@tor-dev:~/src/gitlab.torproject.org/xxx/xxx$ git push --force git@gitlab.torproject.org:ahf/test-push-mirror.git '+refs/*:refs/*' --dry-run
To gitlab.torproject.org:ahf/test-push-mirror.git
   dd75357..964d4c0  master -> master

Here master gets moved forward properly, but we do not delete anything at the destination that is unknown at the source.

Adding --prune here would give the same behavior as git push --mirror:

user@tor-dev:~/src/gitlab.torproject.org/xxx/xxx$ git push --prune --force git@gitlab.torproject.org:ahf/test-push-mirror.git '+refs/*:refs/*' --dry-run
To gitlab.torproject.org:ahf/test-push-mirror.git
   dd75357..964d4c0  master -> master
 - [deleted]         test-branch
 - [deleted]         refs/merge-requests/1/head
 - [deleted]         refs/merge-requests/1/merge

Since we move everything under refs/* with the refspec we pass, this should include tags as well as branches.

The only downside of this approach is this: if a person pushes to Gitlab a branch that does not not exist on Gitolite, the branch will remain on Gitlab until it's manually deleted. That is fine: if the branch does exist, it will simply be overwritten next time Gitolite pushes to Gitlab.

See also bug 41 for a larger discussion on this solution.

Pager playbook

gitweb out of sync

If vineale is down for an extended period of time, it's a good idea to trigger a re-sync of all the repositories to ensure that the latest version is available to clone from the anonymous endpoints.

Create an empty commit in the gitolite-admin.git repository using:

git commit -m "trigger resync" --allow-empty

and push this commit. This will run through the post-commit hook that includes syncing everything.

Reference

Design

git-rw runs on cupani.torproject.org and runs as the git user. Users in the gitolite (gid 1504) group can become the git user. The gitolite installation is contained inside /srv/git.torproject.org with the repositories being found in the repositories folder there.

The gitolite installation itself is not from Debian packages. It's a manual install, in /srv/git.torproject.org/gitolite/src, of an extremely old version (v0.95-38-gb0ce84d, december 2009).

Anonymous git and gitweb run on vineale.torproject.org and as the gitweb user. Users in the gitweb (gid 1505) group can become the gitweb user. Data for these services can be found in /srv/gitweb.torproject.org.

The gitolite configuration is found at git@git-rw.torproject.org:gitolite-admin.git and is not mirrored to gitweb.

The gitolite group on the git-rw server defined in LDAP and has total control of the gitolite installation, as its members can sudo to git.

The git user gets redirected through the /srv/git.torproject.org/gitolite/src/gl-auth-command through the /etc/ssh/userkeys/git authorized_keys file. This, in turn, gets generated from LDAP, somewhere inside the ud-generate command, because exportOptions is set to GITOLITE on the cupani host. All users with a valid LDAP account get their SSH key added to the list and only gitolite configuration restricts further access.

Access to push to this repository is controlled by the gitolite-admin repository entry in the gitolite configuration file, and not by LDAP groups.

GitLab migration

As mentioned in the lead, the gitolite/gitweb infrastructure is, as of May 2021, considered legacy and users are encouraged to create new repositories, and migrate old ones to GitLab. In the intermediate period, repositories can be mirrored between gitolite and GitLab as well.

Security concerns

This section is a summary of the discussions that happened in tpo/tpa/gitlab#36 and tpo/tpa/gitlab#81.

Some developers expressed concerns about using GitLab as a canonical location for source code repositories, mainly because of the much broader attack surface GitLab provides, compared to the legacy, gitolite-based infrastructure, especially considering that the web application basically has write access to everything.

Of course, GitLab is larger, and if there's an unauthenticated attack against GitLab, that could compromise our repositories. And there is a stead flow of new vulnerabilities in GitLab (sorted by priority), including remote code execution. And although none of those provide unauthenticated code execution, our anonymous portal provides a bypass to that protection, so this is a real threat that must be addressed.

When we think about authenticated users, however, gitolite has a problem: our current gitolite install is pretty old, and (deliberately) does not follow new upstream releases. Great care has been taken to run a gitolite version that is specifically older, to ensure a smaller attack surface, because it has less features than newer gitolite versions. That's why it's such a weird version.

It is worrisome that we use an old version of the software that is essentially unmaintained. It is technical debt that makes maintenance harder. It's true that this old gitolite has a much smalller attack surface than gitlab (or even more recent gitolite), but the chosen approach to fix this problem has to do with having other mechanisms to ensure code integrity (code signing and supply chain integrity) or secrecy (ie. encrypted repositories) than trusting the transport.

We are actively maintaining gitlab, following upstream releases quite closely. Upstream is actively auditing their code base, and many vulnerabilities published are actually a result of those internal audits.

If we are worried about trust in our supply chain, GitLab security is only part of the problem. It's a problem that currently exists with Gitolite. For example, what happens if a developer's laptop gets compromised? How do we audit changes to gitolite repositories, assuming it's not compromised? GitLab provides actually more possibilities for such audits. Solutions like code reviews, signed commits, reproducible builds, and transparency logs provide better, long-term and service-agnostic solutions to those problems.

In the end, it came up to a trade-off: GitLab is much easier to use. Convenience won over hardened security, especially considering the cost of running two services in parallel. Or, as Nick Mathewson put it:

I'm proposing that, since this is an area where the developers would need to shoulder most of the burden, the development teams should be responsible for coming up with solutions that work for them on some reasonable timeframe, and that this shouldn't be admin's problem assuming that the timeframe is long enough.

For now, the result of that discussion is a summary of git repository integrity solutions, which is therefore delegated to teams.

Migration roadmap

TODO.

Issues

There is no issue tracker specifically for this project, File or search for issues in the team issue tracker, with the ~Git label.