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-rw-r--r--models/asymkey/gpg_key_object_verification.go520
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diff --git a/models/asymkey/gpg_key_object_verification.go b/models/asymkey/gpg_key_object_verification.go
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+// 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
+}