mirror of
https://codeberg.org/forgejo/forgejo.git
synced 2025-10-25 03:22:36 +00:00
cd19564accThis is, in large part, a refactoring: we rename `CommitVerification` to `ObjectVerification`, and adjust `ParseObjectWithSignature` (previously `ParseCommitWithSignature`) to work on an object, rather than a commit. This in turn, lets us implement `ParseTagWithSignature` on top of it, so commit & tag signature verification will share most of the code. Work sponsored by @glts. Signed-off-by: Gergely Nagy <forgejo@gergo.csillger.hu>
527 lines
16 KiB
Go
527 lines
16 KiB
Go
// Copyright 2021 The Gitea Authors. All rights reserved.
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// Copyright 2024 The Forgejo Authors c/o Codeberg e.V.. 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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"hash"
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"strings"
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"code.gitea.io/gitea/models/db"
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repo_model "code.gitea.io/gitea/models/repo"
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user_model "code.gitea.io/gitea/models/user"
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"code.gitea.io/gitea/modules/git"
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"code.gitea.io/gitea/modules/log"
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"code.gitea.io/gitea/modules/setting"
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"github.com/keybase/go-crypto/openpgp/packet"
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)
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// This file provides functions related to object (commit, tag) verification
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// ObjectVerification represents a commit validation of signature
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type ObjectVerification struct {
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Verified bool
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Warning bool
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Reason string
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SigningUser *user_model.User
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CommittingUser *user_model.User
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SigningEmail string
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SigningKey *GPGKey
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SigningSSHKey *PublicKey
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TrustStatus string
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}
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const (
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// BadSignature is used as the reason when the signature has a KeyID that is in the db
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// but no key that has that ID verifies the signature. This is a suspicious failure.
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BadSignature = "gpg.error.probable_bad_signature"
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// BadDefaultSignature is used as the reason when the signature has a KeyID that matches the
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// default Key but is not verified by the default key. This is a suspicious failure.
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BadDefaultSignature = "gpg.error.probable_bad_default_signature"
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// NoKeyFound is used as the reason when no key can be found to verify the signature.
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NoKeyFound = "gpg.error.no_gpg_keys_found"
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)
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type GitObject struct {
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ID git.ObjectID
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Committer *git.Signature
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Signature *git.ObjectSignature
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Commit *git.Commit
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}
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func commitToGitObject(c *git.Commit) GitObject {
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return GitObject{
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ID: c.ID,
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Committer: c.Committer,
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Signature: c.Signature,
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Commit: c,
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}
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}
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func tagToGitObject(t *git.Tag, gitRepo *git.Repository) GitObject {
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commit, _ := t.Commit(gitRepo)
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return GitObject{
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ID: t.ID,
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Committer: t.Tagger,
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Signature: t.Signature,
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Commit: commit,
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}
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}
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// ParseObjectWithSignature check if signature is good against keystore.
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func ParseObjectWithSignature(ctx context.Context, c *GitObject) *ObjectVerification {
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var committer *user_model.User
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if c.Committer != nil {
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var err error
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// Find Committer account
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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
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if err != nil { // Skipping not user for committer
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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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// We can expect this to often be an ErrUserNotExist. in the case
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// it is not, however, it is important to log it.
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if !user_model.IsErrUserNotExist(err) {
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log.Error("GetUserByEmail: %v", err)
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return &ObjectVerification{
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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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}
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// If no signature just report the committer
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if c.Signature == nil {
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return &ObjectVerification{
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CommittingUser: committer,
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Verified: false, // Default value
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Reason: "gpg.error.not_signed_commit", // Default value
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}
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}
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// If this a SSH signature handle it differently
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if strings.HasPrefix(c.Signature.Signature, "-----BEGIN SSH SIGNATURE-----") {
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return ParseObjectWithSSHSignature(ctx, c, committer)
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}
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// Parsing signature
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sig, err := 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 &ObjectVerification{
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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 := ""
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if sig.IssuerKeyId != nil && (*sig.IssuerKeyId) != 0 {
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keyID = fmt.Sprintf("%X", *sig.IssuerKeyId)
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}
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if keyID == "" && sig.IssuerFingerprint != nil && len(sig.IssuerFingerprint) > 0 {
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keyID = fmt.Sprintf("%X", sig.IssuerFingerprint[12:20])
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}
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defaultReason := 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 == BadSignature {
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defaultReason = 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[GPGKey](ctx, 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 &ObjectVerification{
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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 := GPGKeyList(keys).LoadSubKeys(ctx); err != nil {
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log.Error("LoadSubKeys: %v", err)
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return &ObjectVerification{
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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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committerEmailAddresses, _ := user_model.GetEmailAddresses(ctx, committer.ID)
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activated := false
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for _, e := range committerEmailAddresses {
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if e.IsActivated && strings.EqualFold(e.Email, c.Committer.Email) {
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activated = true
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break
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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 && activated {
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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 := hashAndVerifyWithSubKeysObjectVerification(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 setting.Repository.Signing.SigningKey != "" && setting.Repository.Signing.SigningKey != "default" && setting.Repository.Signing.SigningKey != "none" {
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// OK we should try the default key
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gpgSettings := git.GPGSettings{
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Sign: true,
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KeyID: setting.Repository.Signing.SigningKey,
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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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if err := gpgSettings.LoadPublicKeyContent(); err != nil {
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log.Error("Error getting default signing key: %s %v", gpgSettings.KeyID, err)
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} else if commitVerification := verifyWithGPGSettings(ctx, &gpgSettings, sig, c.Signature.Payload, committer, keyID); commitVerification != nil {
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if commitVerification.Reason == BadSignature {
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defaultReason = BadSignature
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} else {
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return commitVerification
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}
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}
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}
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defaultGPGSettings, err := c.Commit.GetRepositoryDefaultPublicGPGKey(false)
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if err != nil {
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log.Error("Error getting default public gpg key: %v", err)
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} else if defaultGPGSettings == nil {
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log.Warn("Unable to get defaultGPGSettings for unattached commit: %s", c.Commit.ID.String())
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} else if defaultGPGSettings.Sign {
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if commitVerification := verifyWithGPGSettings(ctx, defaultGPGSettings, sig, c.Signature.Payload, committer, keyID); commitVerification != nil {
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if commitVerification.Reason == BadSignature {
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defaultReason = BadSignature
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} else {
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return commitVerification
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}
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}
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}
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return &ObjectVerification{ // Default at this stage
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CommittingUser: committer,
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Verified: false,
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Warning: defaultReason != NoKeyFound,
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Reason: defaultReason,
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SigningKey: &GPGKey{
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KeyID: keyID,
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},
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}
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}
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func verifyWithGPGSettings(ctx context.Context, gpgSettings *git.GPGSettings, sig *packet.Signature, payload string, committer *user_model.User, keyID string) *ObjectVerification {
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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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ekeys, err := checkArmoredGPGKeyString(gpgSettings.PublicKeyContent)
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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 &ObjectVerification{
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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 := base64EncPubKey(pubkey)
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if err != nil {
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return &ObjectVerification{
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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 := &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 := base64EncPubKey(subKey.PublicKey)
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if err != nil {
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return &ObjectVerification{
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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, &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 := hashAndVerifyWithSubKeysObjectVerification(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 &ObjectVerification{
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CommittingUser: committer,
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Verified: false,
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Warning: true,
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Reason: BadSignature,
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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 verifySign(s *packet.Signature, h hash.Hash, k *GPGKey) error {
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// Check if key can sign
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if !k.CanSign {
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return fmt.Errorf("key can not sign")
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}
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// Decode key
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pkey, err := base64DecPubKey(k.Content)
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if err != nil {
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return err
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}
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return pkey.VerifySignature(h, s)
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}
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func hashAndVerify(sig *packet.Signature, payload string, k *GPGKey) (*GPGKey, error) {
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// Generating hash of commit
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hash, err := populateHash(sig.Hash, []byte(payload))
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if err != nil { // Skipping as failed to generate hash
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log.Error("PopulateHash: %v", err)
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return nil, err
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}
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// We will ignore errors in verification as they don't need to be propagated up
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err = verifySign(sig, hash, k)
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if err != nil {
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return nil, nil
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}
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return k, nil
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}
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func hashAndVerifyWithSubKeys(sig *packet.Signature, payload string, k *GPGKey) (*GPGKey, error) {
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verified, err := hashAndVerify(sig, payload, k)
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if err != nil || verified != nil {
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return verified, err
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}
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for _, sk := range k.SubsKey {
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verified, err := hashAndVerify(sig, payload, sk)
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if err != nil || verified != nil {
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return verified, err
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}
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}
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return nil, nil
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}
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func hashAndVerifyWithSubKeysObjectVerification(sig *packet.Signature, payload string, k *GPGKey, committer, signer *user_model.User, email string) *ObjectVerification {
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key, err := hashAndVerifyWithSubKeys(sig, payload, k)
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if err != nil { // Skipping failed to generate hash
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return &ObjectVerification{
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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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if key != nil {
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return &ObjectVerification{ // Everything is ok
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CommittingUser: committer,
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Verified: true,
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Reason: fmt.Sprintf("%s / %s", signer.Name, key.KeyID),
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SigningUser: signer,
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SigningKey: key,
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SigningEmail: email,
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}
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}
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return nil
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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) *ObjectVerification {
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if keyID == "" {
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return nil
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}
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keys, err := db.Find[GPGKey](ctx, FindGPGKeyOptions{
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KeyID: keyID,
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IncludeSubKeys: true,
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})
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if err != nil {
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log.Error("GetGPGKeysByKeyID: %v", err)
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return &ObjectVerification{
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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 []*GPGKey
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if key.PrimaryKeyID != "" {
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primaryKeys, err = db.Find[GPGKey](ctx, FindGPGKeyOptions{
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KeyID: key.PrimaryKeyID,
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IncludeSubKeys: true,
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})
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if err != nil {
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log.Error("GetGPGKeysByKeyID: %v", err)
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return &ObjectVerification{
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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([]*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 := user_model.GetUserByID(ctx, key.OwnerID)
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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 &ObjectVerification{
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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 := hashAndVerifyWithSubKeysObjectVerification(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 &ObjectVerification{
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CommittingUser: committer,
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Verified: false,
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Warning: true,
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Reason: BadSignature,
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}
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}
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// CalculateTrustStatus will calculate the TrustStatus for a commit verification within a repository
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// There are several trust models in Gitea
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func CalculateTrustStatus(verification *ObjectVerification, repoTrustModel repo_model.TrustModelType, isOwnerMemberCollaborator func(*user_model.User) (bool, error), keyMap *map[string]bool) error {
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if !verification.Verified {
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return nil
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}
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// In the Committer trust model a signature is trusted if it matches the committer
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// - it doesn't matter if they're a collaborator, the owner, Gitea or Github
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// NB: This model is commit verification only
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if repoTrustModel == repo_model.CommitterTrustModel {
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// default to "unmatched"
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verification.TrustStatus = "unmatched"
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// We can only verify against users in our database but the default key will match
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// against by email if it is not in the db.
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if (verification.SigningUser.ID != 0 &&
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verification.CommittingUser.ID == verification.SigningUser.ID) ||
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(verification.SigningUser.ID == 0 && verification.CommittingUser.ID == 0 &&
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verification.SigningUser.Email == verification.CommittingUser.Email) {
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verification.TrustStatus = "trusted"
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}
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return nil
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}
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// Now we drop to the more nuanced trust models...
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verification.TrustStatus = "trusted"
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if verification.SigningUser.ID == 0 {
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// This commit is signed by the default key - but this key is not assigned to a user in the DB.
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// However in the repo_model.CollaboratorCommitterTrustModel we cannot mark this as trusted
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// unless the default key matches the email of a non-user.
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if repoTrustModel == repo_model.CollaboratorCommitterTrustModel && (verification.CommittingUser.ID != 0 ||
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verification.SigningUser.Email != verification.CommittingUser.Email) {
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verification.TrustStatus = "untrusted"
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}
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return nil
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}
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// Check we actually have a GPG SigningKey
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var err error
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if verification.SigningKey != nil {
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|
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
|
|
}
|