diff options
Diffstat (limited to 'models/asymkey/gpg_key_object_verification.go')
| -rw-r--r-- | models/asymkey/gpg_key_object_verification.go | 520 |
1 files changed, 520 insertions, 0 deletions
diff --git a/models/asymkey/gpg_key_object_verification.go b/models/asymkey/gpg_key_object_verification.go new file mode 100644 index 0000000..24d72a5 --- /dev/null +++ b/models/asymkey/gpg_key_object_verification.go @@ -0,0 +1,520 @@ +// Copyright 2021 The Gitea Authors. All rights reserved. +// Copyright 2024 The Forgejo Authors c/o Codeberg e.V.. All rights reserved. +// SPDX-License-Identifier: MIT + +package asymkey + +import ( + "context" + "fmt" + "hash" + "strings" + + "code.gitea.io/gitea/models/db" + repo_model "code.gitea.io/gitea/models/repo" + user_model "code.gitea.io/gitea/models/user" + "code.gitea.io/gitea/modules/git" + "code.gitea.io/gitea/modules/log" + "code.gitea.io/gitea/modules/setting" + + "github.com/ProtonMail/go-crypto/openpgp/packet" +) + +// This file provides functions related to object (commit, tag) verification + +// ObjectVerification represents a commit validation of signature +type ObjectVerification struct { + Verified bool + Warning bool + Reason string + SigningUser *user_model.User + CommittingUser *user_model.User + SigningEmail string + SigningKey *GPGKey + SigningSSHKey *PublicKey + TrustStatus string +} + +const ( + // BadSignature is used as the reason when the signature has a KeyID that is in the db + // but no key that has that ID verifies the signature. This is a suspicious failure. + BadSignature = "gpg.error.probable_bad_signature" + // BadDefaultSignature is used as the reason when the signature has a KeyID that matches the + // default Key but is not verified by the default key. This is a suspicious failure. + BadDefaultSignature = "gpg.error.probable_bad_default_signature" + // NoKeyFound is used as the reason when no key can be found to verify the signature. + NoKeyFound = "gpg.error.no_gpg_keys_found" +) + +type GitObject struct { + ID git.ObjectID + Committer *git.Signature + Signature *git.ObjectSignature + Commit *git.Commit +} + +func commitToGitObject(c *git.Commit) GitObject { + return GitObject{ + ID: c.ID, + Committer: c.Committer, + Signature: c.Signature, + Commit: c, + } +} + +func tagToGitObject(t *git.Tag, gitRepo *git.Repository) GitObject { + commit, _ := t.Commit(gitRepo) + return GitObject{ + ID: t.ID, + Committer: t.Tagger, + Signature: t.Signature, + Commit: commit, + } +} + +// ParseObjectWithSignature check if signature is good against keystore. +func ParseObjectWithSignature(ctx context.Context, c *GitObject) *ObjectVerification { + var committer *user_model.User + if c.Committer != nil { + var err error + // Find Committer account + committer, err = user_model.GetUserByEmail(ctx, c.Committer.Email) // This finds the user by primary email or activated email so commit will not be valid if email is not + if err != nil { // Skipping not user for committer + committer = &user_model.User{ + Name: c.Committer.Name, + Email: c.Committer.Email, + } + // We can expect this to often be an ErrUserNotExist. in the case + // it is not, however, it is important to log it. + if !user_model.IsErrUserNotExist(err) { + log.Error("GetUserByEmail: %v", err) + return &ObjectVerification{ + CommittingUser: committer, + Verified: false, + Reason: "gpg.error.no_committer_account", + } + } + } + } + + // If no signature just report the committer + if c.Signature == nil { + return &ObjectVerification{ + CommittingUser: committer, + Verified: false, // Default value + Reason: "gpg.error.not_signed_commit", // Default value + } + } + + // If this a SSH signature handle it differently + if strings.HasPrefix(c.Signature.Signature, "-----BEGIN SSH SIGNATURE-----") { + return ParseObjectWithSSHSignature(ctx, c, committer) + } + + // Parsing signature + sig, err := extractSignature(c.Signature.Signature) + if err != nil { // Skipping failed to extract sign + log.Error("SignatureRead err: %v", err) + return &ObjectVerification{ + CommittingUser: committer, + Verified: false, + Reason: "gpg.error.extract_sign", + } + } + + keyID := tryGetKeyIDFromSignature(sig) + defaultReason := NoKeyFound + + // First check if the sig has a keyID and if so just look at that + if commitVerification := hashAndVerifyForKeyID( + ctx, + sig, + c.Signature.Payload, + committer, + keyID, + setting.AppName, + ""); commitVerification != nil { + if commitVerification.Reason == BadSignature { + defaultReason = BadSignature + } else { + return commitVerification + } + } + + // Now try to associate the signature with the committer, if present + if committer.ID != 0 { + keys, err := db.Find[GPGKey](ctx, FindGPGKeyOptions{ + OwnerID: committer.ID, + }) + if err != nil { // Skipping failed to get gpg keys of user + log.Error("ListGPGKeys: %v", err) + return &ObjectVerification{ + CommittingUser: committer, + Verified: false, + Reason: "gpg.error.failed_retrieval_gpg_keys", + } + } + + if err := GPGKeyList(keys).LoadSubKeys(ctx); err != nil { + log.Error("LoadSubKeys: %v", err) + return &ObjectVerification{ + CommittingUser: committer, + Verified: false, + Reason: "gpg.error.failed_retrieval_gpg_keys", + } + } + + committerEmailAddresses, _ := user_model.GetEmailAddresses(ctx, committer.ID) + activated := false + for _, e := range committerEmailAddresses { + if e.IsActivated && strings.EqualFold(e.Email, c.Committer.Email) { + activated = true + break + } + } + + for _, k := range keys { + // Pre-check (& optimization) that emails attached to key can be attached to the committer email and can validate + canValidate := false + email := "" + if k.Verified && activated { + canValidate = true + email = c.Committer.Email + } + if !canValidate { + for _, e := range k.Emails { + if e.IsActivated && strings.EqualFold(e.Email, c.Committer.Email) { + canValidate = true + email = e.Email + break + } + } + } + if !canValidate { + continue // Skip this key + } + + commitVerification := hashAndVerifyWithSubKeysObjectVerification(sig, c.Signature.Payload, k, committer, committer, email) + if commitVerification != nil { + return commitVerification + } + } + } + + if setting.Repository.Signing.SigningKey != "" && setting.Repository.Signing.SigningKey != "default" && setting.Repository.Signing.SigningKey != "none" { + // OK we should try the default key + gpgSettings := git.GPGSettings{ + Sign: true, + KeyID: setting.Repository.Signing.SigningKey, + Name: setting.Repository.Signing.SigningName, + Email: setting.Repository.Signing.SigningEmail, + } + if err := gpgSettings.LoadPublicKeyContent(); err != nil { + log.Error("Error getting default signing key: %s %v", gpgSettings.KeyID, err) + } else if commitVerification := verifyWithGPGSettings(ctx, &gpgSettings, sig, c.Signature.Payload, committer, keyID); commitVerification != nil { + if commitVerification.Reason == BadSignature { + defaultReason = BadSignature + } else { + return commitVerification + } + } + } + + defaultGPGSettings, err := c.Commit.GetRepositoryDefaultPublicGPGKey(false) + if err != nil { + log.Error("Error getting default public gpg key: %v", err) + } else if defaultGPGSettings == nil { + log.Warn("Unable to get defaultGPGSettings for unattached commit: %s", c.Commit.ID.String()) + } else if defaultGPGSettings.Sign { + if commitVerification := verifyWithGPGSettings(ctx, defaultGPGSettings, sig, c.Signature.Payload, committer, keyID); commitVerification != nil { + if commitVerification.Reason == BadSignature { + defaultReason = BadSignature + } else { + return commitVerification + } + } + } + + return &ObjectVerification{ // Default at this stage + CommittingUser: committer, + Verified: false, + Warning: defaultReason != NoKeyFound, + Reason: defaultReason, + SigningKey: &GPGKey{ + KeyID: keyID, + }, + } +} + +func verifyWithGPGSettings(ctx context.Context, gpgSettings *git.GPGSettings, sig *packet.Signature, payload string, committer *user_model.User, keyID string) *ObjectVerification { + // First try to find the key in the db + if commitVerification := hashAndVerifyForKeyID(ctx, sig, payload, committer, gpgSettings.KeyID, gpgSettings.Name, gpgSettings.Email); commitVerification != nil { + return commitVerification + } + + // Otherwise we have to parse the key + ekeys, err := checkArmoredGPGKeyString(gpgSettings.PublicKeyContent) + if err != nil { + log.Error("Unable to get default signing key: %v", err) + return &ObjectVerification{ + CommittingUser: committer, + Verified: false, + Reason: "gpg.error.generate_hash", + } + } + for _, ekey := range ekeys { + pubkey := ekey.PrimaryKey + content, err := base64EncPubKey(pubkey) + if err != nil { + return &ObjectVerification{ + CommittingUser: committer, + Verified: false, + Reason: "gpg.error.generate_hash", + } + } + k := &GPGKey{ + Content: content, + CanSign: pubkey.CanSign(), + KeyID: pubkey.KeyIdString(), + } + for _, subKey := range ekey.Subkeys { + content, err := base64EncPubKey(subKey.PublicKey) + if err != nil { + return &ObjectVerification{ + CommittingUser: committer, + Verified: false, + Reason: "gpg.error.generate_hash", + } + } + k.SubsKey = append(k.SubsKey, &GPGKey{ + Content: content, + CanSign: subKey.PublicKey.CanSign(), + KeyID: subKey.PublicKey.KeyIdString(), + }) + } + if commitVerification := hashAndVerifyWithSubKeysObjectVerification(sig, payload, k, committer, &user_model.User{ + Name: gpgSettings.Name, + Email: gpgSettings.Email, + }, gpgSettings.Email); commitVerification != nil { + return commitVerification + } + if keyID == k.KeyID { + // This is a bad situation ... We have a key id that matches our default key but the signature doesn't match. + return &ObjectVerification{ + CommittingUser: committer, + Verified: false, + Warning: true, + Reason: BadSignature, + } + } + } + return nil +} + +func verifySign(s *packet.Signature, h hash.Hash, k *GPGKey) error { + // Check if key can sign + if !k.CanSign { + return fmt.Errorf("key can not sign") + } + // Decode key + pkey, err := base64DecPubKey(k.Content) + if err != nil { + return err + } + return pkey.VerifySignature(h, s) +} + +func hashAndVerify(sig *packet.Signature, payload string, k *GPGKey) (*GPGKey, error) { + // Generating hash of commit + hash, err := populateHash(sig.Hash, []byte(payload)) + if err != nil { // Skipping as failed to generate hash + log.Error("PopulateHash: %v", err) + return nil, err + } + // We will ignore errors in verification as they don't need to be propagated up + err = verifySign(sig, hash, k) + if err != nil { + return nil, nil + } + return k, nil +} + +func hashAndVerifyWithSubKeys(sig *packet.Signature, payload string, k *GPGKey) (*GPGKey, error) { + verified, err := hashAndVerify(sig, payload, k) + if err != nil || verified != nil { + return verified, err + } + for _, sk := range k.SubsKey { + verified, err := hashAndVerify(sig, payload, sk) + if err != nil || verified != nil { + return verified, err + } + } + return nil, nil +} + +func hashAndVerifyWithSubKeysObjectVerification(sig *packet.Signature, payload string, k *GPGKey, committer, signer *user_model.User, email string) *ObjectVerification { + key, err := hashAndVerifyWithSubKeys(sig, payload, k) + if err != nil { // Skipping failed to generate hash + return &ObjectVerification{ + CommittingUser: committer, + Verified: false, + Reason: "gpg.error.generate_hash", + } + } + + if key != nil { + return &ObjectVerification{ // Everything is ok + CommittingUser: committer, + Verified: true, + Reason: fmt.Sprintf("%s / %s", signer.Name, key.KeyID), + SigningUser: signer, + SigningKey: key, + SigningEmail: email, + } + } + return nil +} + +func hashAndVerifyForKeyID(ctx context.Context, sig *packet.Signature, payload string, committer *user_model.User, keyID, name, email string) *ObjectVerification { + if keyID == "" { + return nil + } + keys, err := db.Find[GPGKey](ctx, FindGPGKeyOptions{ + KeyID: keyID, + IncludeSubKeys: true, + }) + if err != nil { + log.Error("GetGPGKeysByKeyID: %v", err) + return &ObjectVerification{ + CommittingUser: committer, + Verified: false, + Reason: "gpg.error.failed_retrieval_gpg_keys", + } + } + if len(keys) == 0 { + return nil + } + for _, key := range keys { + var primaryKeys []*GPGKey + if key.PrimaryKeyID != "" { + primaryKeys, err = db.Find[GPGKey](ctx, FindGPGKeyOptions{ + KeyID: key.PrimaryKeyID, + IncludeSubKeys: true, + }) + if err != nil { + log.Error("GetGPGKeysByKeyID: %v", err) + return &ObjectVerification{ + CommittingUser: committer, + Verified: false, + Reason: "gpg.error.failed_retrieval_gpg_keys", + } + } + } + + activated, email := checkKeyEmails(ctx, email, append([]*GPGKey{key}, primaryKeys...)...) + if !activated { + continue + } + + signer := &user_model.User{ + Name: name, + Email: email, + } + if key.OwnerID != 0 { + owner, err := user_model.GetUserByID(ctx, key.OwnerID) + if err == nil { + signer = owner + } else if !user_model.IsErrUserNotExist(err) { + log.Error("Failed to user_model.GetUserByID: %d for key ID: %d (%s) %v", key.OwnerID, key.ID, key.KeyID, err) + return &ObjectVerification{ + CommittingUser: committer, + Verified: false, + Reason: "gpg.error.no_committer_account", + } + } + } + commitVerification := hashAndVerifyWithSubKeysObjectVerification(sig, payload, key, committer, signer, email) + if commitVerification != nil { + return commitVerification + } + } + // This is a bad situation ... We have a key id that is in our database but the signature doesn't match. + return &ObjectVerification{ + CommittingUser: committer, + Verified: false, + Warning: true, + Reason: BadSignature, + } +} + +// CalculateTrustStatus will calculate the TrustStatus for a commit verification within a repository +// There are several trust models in Gitea +func CalculateTrustStatus(verification *ObjectVerification, repoTrustModel repo_model.TrustModelType, isOwnerMemberCollaborator func(*user_model.User) (bool, error), keyMap *map[string]bool) error { + if !verification.Verified { + return nil + } + + // In the Committer trust model a signature is trusted if it matches the committer + // - it doesn't matter if they're a collaborator, the owner, Gitea or Github + // NB: This model is commit verification only + if repoTrustModel == repo_model.CommitterTrustModel { + // default to "unmatched" + verification.TrustStatus = "unmatched" + + // We can only verify against users in our database but the default key will match + // against by email if it is not in the db. + if (verification.SigningUser.ID != 0 && + verification.CommittingUser.ID == verification.SigningUser.ID) || + (verification.SigningUser.ID == 0 && verification.CommittingUser.ID == 0 && + verification.SigningUser.Email == verification.CommittingUser.Email) { + verification.TrustStatus = "trusted" + } + return nil + } + + // Now we drop to the more nuanced trust models... + verification.TrustStatus = "trusted" + + if verification.SigningUser.ID == 0 { + // This commit is signed by the default key - but this key is not assigned to a user in the DB. + + // However in the repo_model.CollaboratorCommitterTrustModel we cannot mark this as trusted + // unless the default key matches the email of a non-user. + if repoTrustModel == repo_model.CollaboratorCommitterTrustModel && (verification.CommittingUser.ID != 0 || + verification.SigningUser.Email != verification.CommittingUser.Email) { + verification.TrustStatus = "untrusted" + } + return nil + } + + // Check we actually have a GPG SigningKey + var err error + if verification.SigningKey != nil { + var isMember bool + if keyMap != nil { + var has bool + isMember, has = (*keyMap)[verification.SigningKey.KeyID] + if !has { + isMember, err = isOwnerMemberCollaborator(verification.SigningUser) + (*keyMap)[verification.SigningKey.KeyID] = isMember + } + } else { + isMember, err = isOwnerMemberCollaborator(verification.SigningUser) + } + + if !isMember { + verification.TrustStatus = "untrusted" + if verification.CommittingUser.ID != verification.SigningUser.ID { + // The committing user and the signing user are not the same + // This should be marked as questionable unless the signing user is a collaborator/team member etc. + verification.TrustStatus = "unmatched" + } + } else if repoTrustModel == repo_model.CollaboratorCommitterTrustModel && verification.CommittingUser.ID != verification.SigningUser.ID { + // The committing user and the signing user are not the same and our trustmodel states that they must match + verification.TrustStatus = "unmatched" + } + } + + return err +} |