forgejo/models/asymkey/ssh_key_object_verification.go
Gusted b55c72828e feat(sec): Add SSH signing support for instances (#6897)
- Add support to set `gpg.format` in the Git config, via the new `[repository.signing].FORMAT` option. This is to tell Git that the instance would like to use SSH instead of OpenPGP to sign its commits. This is guarded behind a Git version check for v2.34.0 and a check that a `ssh-keygen` binary is present.
- Add support to recognize the public SSH key that is given to `[repository.signing].SIGNING_KEY` as the signing key by the instance.
- Thus this allows the instance to use SSH commit signing for commits that the instance creates (e.g. initial and squash commits) instead of using PGP.
- Technically (although I have no clue how as this is not documented) you can have a different PGP signing key for different repositories; this is not implemented for SSH signing.
- Add unit and integration testing.
  - `TestInstanceSigning` was reworked from `TestGPGGit`, now also includes testing for SHA256 repositories. Is the main integration test that actually signs commits and checks that they are marked as verified by Forgejo.
  - `TestParseCommitWithSSHSignature` is a unit test that makes sure that if a SSH instnace signing key is set, that it is used to possibly verify instance SSH signed commits.
  - `TestSyncConfigGPGFormat` is a unit test that makes sure the correct git config is set according to the signing format setting. Also checks that the guarded git version check and ssh-keygen binary presence check is done correctly.
  - `TestSSHInstanceKey` is a unit test that makes sure the parsing of a SSH signing key is done correctly.
  - `TestAPISSHSigningKey` is a integration test that makes sure the newly added API route `/api/v1/signing-key.ssh` responds correctly.

Documentation PR: forgejo/docs#1122

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/6897
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: Gusted <postmaster@gusted.xyz>
Co-committed-by: Gusted <postmaster@gusted.xyz>
2025-04-11 13:25:35 +00:00

103 lines
3.1 KiB
Go

// Copyright 2021 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package asymkey
import (
"bytes"
"context"
"fmt"
"strings"
"forgejo.org/models/db"
user_model "forgejo.org/models/user"
"forgejo.org/modules/log"
"forgejo.org/modules/setting"
"github.com/42wim/sshsig"
"golang.org/x/crypto/ssh"
)
// ParseObjectWithSSHSignature check if signature is good against keystore.
func ParseObjectWithSSHSignature(ctx context.Context, c *GitObject, committer *user_model.User) *ObjectVerification {
// Now try to associate the signature with the committer, if present
if committer.ID != 0 {
keys, err := db.Find[PublicKey](ctx, FindPublicKeyOptions{
OwnerID: committer.ID,
NotKeytype: KeyTypePrincipal,
})
if err != nil { // Skipping failed to get ssh keys of user
log.Error("ListPublicKeys: %v", err)
return &ObjectVerification{
CommittingUser: committer,
Verified: false,
Reason: "gpg.error.failed_retrieval_gpg_keys",
}
}
committerEmailAddresses, err := user_model.GetEmailAddresses(ctx, committer.ID)
if err != nil {
log.Error("GetEmailAddresses: %v", err)
}
// Add the noreply email address as verified address.
committerEmailAddresses = append(committerEmailAddresses, &user_model.EmailAddress{
IsActivated: true,
Email: committer.GetPlaceholderEmail(),
})
activated := false
for _, e := range committerEmailAddresses {
if e.IsActivated && strings.EqualFold(e.Email, c.Committer.Email) {
activated = true
break
}
}
for _, k := range keys {
if k.Verified && activated {
commitVerification := verifySSHObjectVerification(c.Signature.Signature, c.Signature.Payload, k, committer, committer, c.Committer.Email)
if commitVerification != nil {
return commitVerification
}
}
}
}
// If the SSH instance key is set, try to verify it with that key.
if setting.SSHInstanceKey != nil {
instanceSSHKey := &PublicKey{
Content: string(ssh.MarshalAuthorizedKey(setting.SSHInstanceKey)),
Fingerprint: ssh.FingerprintSHA256(setting.SSHInstanceKey),
}
instanceUser := &user_model.User{
Name: setting.Repository.Signing.SigningName,
Email: setting.Repository.Signing.SigningEmail,
}
commitVerification := verifySSHObjectVerification(c.Signature.Signature, c.Signature.Payload, instanceSSHKey, committer, instanceUser, setting.Repository.Signing.SigningEmail)
if commitVerification != nil {
return commitVerification
}
}
return &ObjectVerification{
CommittingUser: committer,
Verified: false,
Reason: NoKeyFound,
}
}
func verifySSHObjectVerification(sig, payload string, k *PublicKey, committer, signer *user_model.User, email string) *ObjectVerification {
if err := sshsig.Verify(bytes.NewBuffer([]byte(payload)), []byte(sig), []byte(k.Content), "git"); err != nil {
return nil
}
return &ObjectVerification{ // Everything is ok
CommittingUser: committer,
Verified: true,
Reason: fmt.Sprintf("%s / %s", signer.Name, k.Fingerprint),
SigningUser: signer,
SigningSSHKey: k,
SigningEmail: email,
}
}