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forgejo-federation/docs/content/doc/advanced/signing.en-us.md
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Sign merges, CRUD, Wiki and Repository initialisation with gpg key (#7631) 
This PR fixes #7598 by providing a configurable way of signing commits across the Gitea instance. Per repository configurability and import/generation of trusted secure keys is not provided by this PR - from a security PoV that's probably impossible to do properly. Similarly web-signing, that is asking the user to sign something, is not implemented - this could be done at a later stage however.

## Features
- [x] If commit.gpgsign is set in .gitconfig sign commits and files created through repofiles. (merges should already have been signed.)
- [x] Verify commits signed with the default gpg as valid
- [x] Signer, Committer and Author can all be different
    - [x] Allow signer to be arbitrarily different - We still require the key to have an activated email on Gitea. A more complete implementation would be to use a keyserver and mark external-or-unactivated with an "unknown" trust level icon.
- [x] Add a signing-key.gpg endpoint to get the default gpg pub key if available
    - Rather than add a fake web-flow user I've added this as an endpoint on /api/v1/signing-key.gpg
    - [x] Try to match the default key with a user on gitea - this is done at verification time
- [x] Make things configurable?
    - app.ini configuration done
    - [x] when checking commits are signed need to check if they're actually verifiable too
- [x] Add documentation

I have decided that adjusting the docker to create a default gpg key is not the correct thing to do and therefore have not implemented this.
2019-10-16 14:42:42 +01:00

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date title slug weight toc draft menu
2019-08-17T10:20:00+01:00 GPG Commit Signatures signing 20 false false
sidebar
parent name weight identifier
advanced GPG Commit Signatures 20 signing

GPG Commit Signatures

Gitea will verify GPG commit signatures in the provided tree by checking if the commits are signed by a key within the gitea database, or if the commit matches the default key for git.

Keys are not checked to determine if they have expired or revoked. Keys are also not checked with keyservers.

A commit will be marked with a grey unlocked icon if no key can be found to verify it. If a commit is marked with a red unlocked icon, it is reported to be signed with a key with an id.

Please note: The signer of a commit does not have to be an author or committer of a commit.

This functionality requires git >= 1.7.9 but for full functionality this requires git >= 2.0.0.

Automatic Signing

There are a number of places where Gitea will generate commits itself:

  • Repository Initialisation
  • Wiki Changes
  • CRUD actions using the editor or the API
  • Merges from Pull Requests

Depending on configuration and server trust you may want Gitea to sign these commits.

General Configuration

Gitea's configuration for signing can be found with the [repository.signing] section of app.ini:

...
[repository.signing]
SIGNING_KEY = default
SIGNING_NAME =
SIGNING_EMAIL =
INITIAL_COMMIT = always
CRUD_ACTIONS = pubkey, twofa, parentsigned
WIKI = never
MERGES = pubkey, twofa, basesigned, commitssigned

...

SIGNING_KEY

The first option to discuss is the SIGNING_KEY. There are three main options:

  • none - this prevents Gitea from signing any commits
  • default - Gitea will default to the key configured within git config
  • KEYID - Gitea will sign commits with the gpg key with the ID KEYID. In this case you should provide a SIGNING_NAME and SIGNING_EMAIL to be displayed for this key.

The default option will interrogate git config for commit.gpgsign option - if this is set, then it will use the results of the user.signingkey, user.name and user.email as appropriate.

Please note: by adjusting git's config file within Gitea's repositories, SIGNING_KEY=default could be used to provide different signing keys on a per-repository basis. However, this is cleary not an ideal UI and therefore subject to change.

INITIAL_COMMIT

This option determines whether Gitea should sign the initial commit when creating a repository. The possible values are:

  • never: Never sign
  • pubkey: Only sign if the user has a public key
  • twofa: Only sign if the user logs in with two factor authentication
  • always: Always sign

Options other than never and always can be combined as a comma separated list.

WIKI

This options determines if Gitea should sign commits to the Wiki. The possible values are:

  • never: Never sign
  • pubkey: Only sign if the user has a public key
  • twofa: Only sign if the user logs in with two factor authentication
  • parentsigned: Only sign if the parent commit is signed.
  • always: Always sign

Options other than never and always can be combined as a comma separated list.

CRUD_ACTIONS

This option determines if Gitea should sign commits from the web editor or API CRUD actions. The possible values are:

  • never: Never sign
  • pubkey: Only sign if the user has a public key
  • twofa: Only sign if the user logs in with two factor authentication
  • parentsigned: Only sign if the parent commit is signed.
  • always: Always sign

Options other than never and always can be combined as a comma separated list.

MERGES

This option determines if Gitea should sign merge commits from PRs. The possible options are:

  • never: Never sign
  • pubkey: Only sign if the user has a public key
  • twofa: Only sign if the user logs in with two factor authentication
  • basesigned: Only sign if the parent commit in the base repo is signed.
  • headsigned: Only sign if the head commit in the head branch is signed.
  • commitssigned: Only sign if all the commits in the head branch to the merge point are signed.
  • always: Always sign

Options other than never and always can be combined as a comma separated list.

Installing and generating a GPG key for Gitea

It is up to a server administrator to determine how best to install a signing key. Gitea generates all its commits using the server git command at present - and therefore the server gpg will be used for signing (if configured.) Administrators should review best-practices for gpg - in particular it is probably advisable to only install a signing secret subkey without the master signing and certifying secret key.

Obtaining the Public Key of the Signing Key

The public key used to sign Gitea's commits can be obtained from the API at:

/api/v1/signing-key.gpg

In cases where there is a repository specific key this can be obtained from:

/api/v1/repos/:username/:reponame/signing-key.gpg