Adding upstream version 9.0.3.

Signed-off-by: Daniel Baumann <daniel@debian.org>

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
+}