mirror of
https://github.com/go-gitea/gitea.git
synced 2026-08-26 23:03:48 +00:00
Artem Lytkin
c8660364d9
With SIGNING_FORMAT = ssh the OpenPGP verification path builds its GPGSettings from the instance signing key but leaves the format empty, so it runs `gpg -a --export` on an SSH public key path. Depending on the local gpg setup that either exports nothing, so an OpenPGP signed commit reports gpg.error.generate_hash instead of a missing key, or it fails outright and logs an export error for every such commit. Both guards are needed. The first covers SIGNING_KEY set to a path with SIGNING_FORMAT=ssh; the second covers the shipped default SIGNING_KEY=default, where the format comes from git's own gpg.format and never gets reconciled with the hardcoded "openpgp". Drop either one and a working config goes back to broken. Also raise minimum git version to 2.18 which was already required before this change. Fixes: https://github.com/go-gitea/gitea/issues/37452 Co-authored-by: wxiaoguang <wxiaoguang@gmail.com> Co-authored-by: silverwind <me@silverwind.io>
456 lines
16 KiB
Go
456 lines
16 KiB
Go
// Copyright 2025 The Gitea Authors. All rights reserved.
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// SPDX-License-Identifier: MIT
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package asymkey
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import (
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"context"
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"fmt"
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"slices"
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"strings"
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asymkey_model "gitea.dev/models/asymkey"
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"gitea.dev/models/db"
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user_model "gitea.dev/models/user"
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"gitea.dev/modules/cache"
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"gitea.dev/modules/cachegroup"
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"gitea.dev/modules/git"
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"gitea.dev/modules/log"
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"gitea.dev/modules/setting"
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"gitea.dev/modules/util"
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"github.com/42wim/sshsig"
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"github.com/ProtonMail/go-crypto/openpgp/packet"
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)
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// ParseCommitWithSignature check if signature is good against keystore.
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func ParseCommitWithSignature(ctx context.Context, c *git.Commit) *asymkey_model.CommitVerification {
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committer, err := user_model.GetUserByEmail(ctx, c.Committer.Email)
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if err != nil && !user_model.IsErrUserNotExist(err) {
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log.Error("GetUserByEmail: %v", err)
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return &asymkey_model.CommitVerification{
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Verified: false,
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Reason: "gpg.error.no_committer_account", // this error is not right, but such error should seldom happen
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}
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}
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return ParseCommitWithSignatureCommitter(ctx, c, committer)
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}
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// ParseCommitWithSignatureCommitter parses a commit's GPG or SSH signature.
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// The caller guarantees that the committer user is related to the commit by checking its activated email addresses or no-reply address.
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// If the commit is singed by an instance key, then committer can be nil.
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// If the signature exists, even if committer is nil, the returned CommittingUser will be a non-nil fake user (e.g.: instance key)
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func ParseCommitWithSignatureCommitter(ctx context.Context, c *git.Commit, committer *user_model.User) *asymkey_model.CommitVerification {
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// If no signature, just report the committer
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if c.Signature == nil {
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return &asymkey_model.CommitVerification{
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CommittingUser: committer,
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Verified: false,
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Reason: "gpg.error.not_signed_commit",
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}
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}
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// to support instance key, we need a fake committer user (not really needed, but legacy code accesses the committer without nil-check)
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if committer == nil {
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committer = &user_model.User{
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Name: c.Committer.Name,
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Email: c.Committer.Email,
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}
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}
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if strings.HasPrefix(c.Signature.Signature, "-----BEGIN SSH SIGNATURE-----") {
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return parseCommitWithSSHSignature(ctx, c, committer)
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}
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return parseCommitWithGPGSignature(ctx, c, committer)
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}
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func getInstanceCommitSignSettings(fmt string) *git.CommitSignSettings {
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settingFmt := util.IfZero(setting.Repository.Signing.SigningFormat, git.SigningKeyFormatOpenPGP)
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if settingFmt != fmt {
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return nil
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}
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if slices.Contains([]string{"", "default", "none"}, setting.Repository.Signing.SigningKey) {
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return nil
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}
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return &git.CommitSignSettings{
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Sign: true,
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Name: setting.Repository.Signing.SigningName,
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Email: setting.Repository.Signing.SigningEmail,
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Format: fmt,
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KeyID: setting.Repository.Signing.SigningKey,
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}
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}
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func getGitGlobalCommitSignSettings(fmt string) *git.CommitSignSettings {
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css := git.GlobalCommitSignSettings.Value()
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if css.Format != fmt || !css.Sign {
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return nil
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}
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return css
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}
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func parseCommitWithGPGSignature(ctx context.Context, c *git.Commit, committer *user_model.User) *asymkey_model.CommitVerification {
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// Parsing signature
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sig, err := asymkey_model.ExtractSignature(c.Signature.Signature)
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if err != nil { // Skipping failed to extract sign
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log.Error("SignatureRead err: %v", err)
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return &asymkey_model.CommitVerification{
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CommittingUser: committer,
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Verified: false,
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Reason: "gpg.error.extract_sign",
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}
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}
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keyID := asymkey_model.TryGetKeyIDFromSignature(sig)
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defaultReason := asymkey_model.NoKeyFound
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// First check if the sig has a keyID and if so just look at that
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if commitVerification := HashAndVerifyForKeyID(
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ctx,
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sig,
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c.Signature.Payload,
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committer,
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keyID,
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setting.AppName,
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""); commitVerification != nil {
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if commitVerification.Reason == asymkey_model.BadSignature {
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defaultReason = asymkey_model.BadSignature
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} else {
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return commitVerification
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}
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}
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// Now try to associate the signature with the committer, if present
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if committer.ID != 0 {
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keys, err := db.Find[asymkey_model.GPGKey](ctx, asymkey_model.FindGPGKeyOptions{
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OwnerID: committer.ID,
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})
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if err != nil { // Skipping failed to get gpg keys of user
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log.Error("ListGPGKeys: %v", err)
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return &asymkey_model.CommitVerification{
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CommittingUser: committer,
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Verified: false,
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Reason: "gpg.error.failed_retrieval_gpg_keys",
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}
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}
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if err := asymkey_model.GPGKeyList(keys).LoadSubKeys(ctx); err != nil {
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log.Error("LoadSubKeys: %v", err)
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return &asymkey_model.CommitVerification{
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CommittingUser: committer,
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Verified: false,
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Reason: "gpg.error.failed_retrieval_gpg_keys",
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}
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}
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for _, k := range keys {
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// Pre-check (& optimization) that emails attached to key can be attached to the committer email and can validate
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canValidate := false
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email := ""
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if k.Verified {
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canValidate = true
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email = c.Committer.Email
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}
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if !canValidate {
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for _, e := range k.Emails {
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if e.IsActivated && strings.EqualFold(e.Email, c.Committer.Email) {
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canValidate = true
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email = e.Email
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break
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}
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}
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}
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if !canValidate {
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continue // Skip this key
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}
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commitVerification := asymkey_model.HashAndVerifyWithSubKeysCommitVerification(sig, c.Signature.Payload, k, committer, committer, email)
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if commitVerification != nil {
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return commitVerification
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}
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}
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}
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if instanceSettings := getInstanceCommitSignSettings(git.SigningKeyFormatOpenPGP); instanceSettings != nil {
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if commitVerification := verifyCommitSignByGPGSettings(ctx, instanceSettings, sig, c.Signature.Payload, committer, keyID); commitVerification != nil {
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if commitVerification.Reason != asymkey_model.BadSignature {
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return commitVerification
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}
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defaultReason = commitVerification.Reason
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}
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}
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if globalSettings := getGitGlobalCommitSignSettings(git.SigningKeyFormatOpenPGP); globalSettings != nil {
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if commitVerification := verifyCommitSignByGPGSettings(ctx, globalSettings, sig, c.Signature.Payload, committer, keyID); commitVerification != nil {
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if commitVerification.Reason != asymkey_model.BadSignature {
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return commitVerification
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}
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defaultReason = commitVerification.Reason
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}
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}
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return &asymkey_model.CommitVerification{ // Default at this stage
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CommittingUser: committer,
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Verified: false,
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Warning: defaultReason != asymkey_model.NoKeyFound,
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Reason: defaultReason,
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SigningKey: &asymkey_model.GPGKey{KeyID: keyID},
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}
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}
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func checkKeyEmails(ctx context.Context, email string, keys ...*asymkey_model.GPGKey) (bool, string) {
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uid := int64(0)
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var userEmails []*user_model.EmailAddress
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var user *user_model.User
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for _, key := range keys {
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for _, e := range key.Emails {
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if e.IsActivated && (email == "" || strings.EqualFold(e.Email, email)) {
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return true, e.Email
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}
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}
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if key.Verified && key.OwnerID != 0 {
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if uid != key.OwnerID {
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userEmails, _ = cache.GetWithContextCache(ctx, cachegroup.UserEmailAddresses, key.OwnerID, user_model.GetEmailAddresses)
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uid = key.OwnerID
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user, _ = cache.GetWithContextCache(ctx, cachegroup.User, uid, user_model.GetUserByID)
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}
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for _, e := range userEmails {
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if e.IsActivated && (email == "" || strings.EqualFold(e.Email, email)) {
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return true, e.Email
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}
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}
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if user != nil && strings.EqualFold(email, user.GetPlaceholderEmail()) {
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return true, user.GetPlaceholderEmail()
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}
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}
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}
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return false, email
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}
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func HashAndVerifyForKeyID(ctx context.Context, sig *packet.Signature, payload string, committer *user_model.User, keyID, name, email string) *asymkey_model.CommitVerification {
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if keyID == "" {
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return nil
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}
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keys, err := cache.GetWithContextCache(ctx, cachegroup.GPGKeyWithSubKeys, keyID, asymkey_model.FindGPGKeyWithSubKeys)
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if err != nil {
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log.Error("GetGPGKeysByKeyID: %v", err)
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return &asymkey_model.CommitVerification{
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CommittingUser: committer,
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Verified: false,
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Reason: "gpg.error.failed_retrieval_gpg_keys",
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}
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}
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if len(keys) == 0 {
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return nil
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}
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for _, key := range keys {
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var primaryKeys []*asymkey_model.GPGKey
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if key.PrimaryKeyID != "" {
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primaryKeys, err = cache.GetWithContextCache(ctx, cachegroup.GPGKeyWithSubKeys, key.PrimaryKeyID, asymkey_model.FindGPGKeyWithSubKeys)
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if err != nil {
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log.Error("GetGPGKeysByKeyID: %v", err)
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return &asymkey_model.CommitVerification{
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CommittingUser: committer,
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Verified: false,
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Reason: "gpg.error.failed_retrieval_gpg_keys",
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}
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}
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}
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activated, email := checkKeyEmails(ctx, email, append([]*asymkey_model.GPGKey{key}, primaryKeys...)...)
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if !activated {
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continue
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}
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signer := &user_model.User{
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Name: name,
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Email: email,
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}
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if key.OwnerID > 0 {
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owner, err := cache.GetWithContextCache(ctx, cachegroup.User, key.OwnerID, user_model.GetUserByID)
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if err == nil {
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signer = owner
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} else if !user_model.IsErrUserNotExist(err) {
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log.Error("Failed to user_model.GetUserByID: %d for key ID: %d (%s) %v", key.OwnerID, key.ID, key.KeyID, err)
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return &asymkey_model.CommitVerification{
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CommittingUser: committer,
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Verified: false,
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Reason: "gpg.error.no_committer_account",
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}
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}
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}
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commitVerification := asymkey_model.HashAndVerifyWithSubKeysCommitVerification(sig, payload, key, committer, signer, email)
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if commitVerification != nil {
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return commitVerification
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}
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}
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// This is a bad situation ... We have a key id that is in our database but the signature doesn't match.
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return &asymkey_model.CommitVerification{
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CommittingUser: committer,
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Verified: false,
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Warning: true,
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Reason: asymkey_model.BadSignature,
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SigningKey: &asymkey_model.GPGKey{KeyID: keyID},
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}
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}
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func verifyCommitSignByGPGSettings(ctx context.Context, gpgSettings *git.CommitSignSettings, sig *packet.Signature, payload string, committer *user_model.User, keyID string) *asymkey_model.CommitVerification {
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// First try to find the key in the db
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if commitVerification := HashAndVerifyForKeyID(ctx, sig, payload, committer, gpgSettings.KeyID, gpgSettings.Name, gpgSettings.Email); commitVerification != nil {
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return commitVerification
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}
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// Otherwise we have to parse the key
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pubKeyContent, err := gpgSettings.PublicKeyContent()
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if err != nil {
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log.Error("gpgSettings.PublicKeyContent: %v", err)
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return nil
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}
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ekeys, err := asymkey_model.CheckArmoredGPGKeyString(pubKeyContent)
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if err != nil {
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log.Error("Unable to get default signing key: %v", err)
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return &asymkey_model.CommitVerification{
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CommittingUser: committer,
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Verified: false,
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Reason: "gpg.error.generate_hash",
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}
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}
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for _, ekey := range ekeys {
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pubkey := ekey.PrimaryKey
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content, err := asymkey_model.Base64EncPubKey(pubkey)
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if err != nil {
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return &asymkey_model.CommitVerification{
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CommittingUser: committer,
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Verified: false,
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Reason: "gpg.error.generate_hash",
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}
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}
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k := &asymkey_model.GPGKey{
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Content: content,
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CanSign: pubkey.CanSign(),
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KeyID: pubkey.KeyIdString(),
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}
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for _, subKey := range ekey.Subkeys {
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content, err := asymkey_model.Base64EncPubKey(subKey.PublicKey)
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if err != nil {
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return &asymkey_model.CommitVerification{
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CommittingUser: committer,
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Verified: false,
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Reason: "gpg.error.generate_hash",
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}
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}
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k.SubsKey = append(k.SubsKey, &asymkey_model.GPGKey{
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Content: content,
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CanSign: subKey.PublicKey.CanSign(),
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KeyID: subKey.PublicKey.KeyIdString(),
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})
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}
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if commitVerification := asymkey_model.HashAndVerifyWithSubKeysCommitVerification(sig, payload, k, committer, &user_model.User{
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Name: gpgSettings.Name,
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Email: gpgSettings.Email,
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}, gpgSettings.Email); commitVerification != nil {
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return commitVerification
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}
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if keyID == k.KeyID {
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// This is a bad situation ... We have a key id that matches our default key but the signature doesn't match.
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return &asymkey_model.CommitVerification{
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CommittingUser: committer,
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Verified: false,
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Warning: true,
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Reason: asymkey_model.BadSignature,
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SigningKey: &asymkey_model.GPGKey{KeyID: keyID},
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}
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}
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}
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return nil
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}
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func verifyCommitSignBySSHSettings(c *git.Commit, committerUser, signerUser *user_model.User, committerGitEmail, publicKeyContent string) *asymkey_model.CommitVerification {
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fingerprint, err := asymkey_model.CalcFingerprint(publicKeyContent)
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if err != nil {
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log.Error("Error calculating the fingerprint public key %q, err: %v", publicKeyContent, err)
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return nil
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}
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sshPubKey := &asymkey_model.PublicKey{
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Verified: true,
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Content: publicKeyContent,
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Fingerprint: fingerprint,
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HasUsed: true,
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}
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return verifyCommitSignBySSHPublicKey(c.Signature.Signature, c.Signature.Payload, sshPubKey, committerUser, signerUser, committerGitEmail)
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}
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// parseCommitWithSSHSignature check if signature is good against keystore.
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func parseCommitWithSSHSignature(ctx context.Context, c *git.Commit, committerUser *user_model.User) *asymkey_model.CommitVerification {
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// Now try to associate the signature with the committer, if present
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if committerUser.ID != 0 {
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keys, err := db.Find[asymkey_model.PublicKey](ctx, asymkey_model.FindPublicKeyOptions{
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OwnerID: committerUser.ID,
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NotKeytype: asymkey_model.KeyTypePrincipal,
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})
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if err != nil { // Skipping failed to get ssh keys of user
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log.Error("ListPublicKeys: %v", err)
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return &asymkey_model.CommitVerification{
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CommittingUser: committerUser,
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Verified: false,
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Reason: "gpg.error.failed_retrieval_gpg_keys",
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}
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}
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for _, k := range keys {
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if k.Verified {
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commitVerification := verifyCommitSignBySSHPublicKey(c.Signature.Signature, c.Signature.Payload, k, committerUser, committerUser, c.Committer.Email)
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if commitVerification != nil {
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return commitVerification
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}
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}
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}
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}
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// Try the pre-set trusted keys (for key-rotation purpose)
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// At the moment, we still use the SigningName&SigningEmail for the rotated keys.
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// Maybe in the future we can extend the key format to "ssh-xxx .... old-user@example.com" to support different signer emails.
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for _, k := range setting.Repository.Signing.TrustedSSHKeys {
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signerUser := &user_model.User{
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Name: setting.Repository.Signing.SigningName,
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Email: setting.Repository.Signing.SigningEmail,
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}
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commitVerification := verifyCommitSignBySSHSettings(c, committerUser, signerUser, c.Committer.Email, k)
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if commitVerification != nil && commitVerification.Verified {
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return commitVerification
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}
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}
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// Try the configured instance-wide SSH public key
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if instanceSettings := getInstanceCommitSignSettings(git.SigningKeyFormatSSH); instanceSettings != nil {
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pubKeyContent, err := instanceSettings.PublicKeyContent()
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if err != nil {
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log.Error("commitSignSettings.PublicKeyContent: %v", err)
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} else {
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signerUser := &user_model.User{Name: instanceSettings.Name, Email: instanceSettings.Email}
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commitVerification := verifyCommitSignBySSHSettings(c, committerUser, signerUser, instanceSettings.Email, pubKeyContent)
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if commitVerification != nil && commitVerification.Verified {
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return commitVerification
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}
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}
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}
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return &asymkey_model.CommitVerification{
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CommittingUser: committerUser,
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Verified: false,
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Reason: asymkey_model.NoKeyFound,
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}
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}
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func verifyCommitSignBySSHPublicKey(sig, payload string, k *asymkey_model.PublicKey, committer, signer *user_model.User, email string) *asymkey_model.CommitVerification {
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if err := sshsig.Verify(strings.NewReader(payload), []byte(sig), []byte(k.Content), "git"); err != nil {
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return nil
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}
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return &asymkey_model.CommitVerification{ // Everything is ok
|
|
CommittingUser: committer,
|
|
Verified: true,
|
|
Reason: fmt.Sprintf("%s / %s", signer.Name, k.Fingerprint),
|
|
SigningUser: signer,
|
|
SigningSSHKey: k,
|
|
SigningEmail: email,
|
|
}
|
|
}
|