julien.rbrt.fr
forked from
tangled.org/core
Monorepo for Tangled — https://tangled.org
1package crypto
2
3import (
4 "bytes"
5 "crypto/sha256"
6 "encoding/base64"
7 "fmt"
8 "strings"
9
10 "github.com/hiddeco/sshsig"
11 "golang.org/x/crypto/ssh"
12 "tangled.sh/tangled.sh/core/types"
13)
14
15func VerifySignature(pubKey, signature, payload []byte) (error, bool) {
16 pub, _, _, _, err := ssh.ParseAuthorizedKey(pubKey)
17 if err != nil {
18 return fmt.Errorf("failed to parse public key: %w", err), false
19 }
20
21 sig, err := sshsig.Unarmor(signature)
22 if err != nil {
23 return fmt.Errorf("failed to parse signature: %w", err), false
24 }
25
26 buf := bytes.NewBuffer(payload)
27 sshsig.Verify(buf, sig, pub, sshsig.HashSHA256, "git")
28 return err, err == nil
29}
30
31// VerifyCommitSignature reconstructs the payload used to sign a commit. This is
32// essentially the git cat-file output but without the gpgsig header.
33//
34// Caveats: signature verification will fail on commits with more than one parent,
35// i.e. merge commits, because types.NiceDiff doesn't carry more than one Parent field
36// and we are unable to reconstruct the payload correctly.
37//
38// Ideally this should directly operate on an *object.Commit.
39func VerifyCommitSignature(pubKey string, commit types.NiceDiff) (error, bool) {
40 signature := commit.Commit.PGPSignature
41
42 author := bytes.NewBuffer([]byte{})
43 committer := bytes.NewBuffer([]byte{})
44 commit.Commit.Author.Encode(author)
45 commit.Commit.Committer.Encode(committer)
46
47 payload := strings.Builder{}
48
49 fmt.Fprintf(&payload, "tree %s\n", commit.Commit.Tree)
50 fmt.Fprintf(&payload, "parent %s\n", commit.Commit.Parent)
51 fmt.Fprintf(&payload, "author %s\n", author.String())
52 fmt.Fprintf(&payload, "committer %s\n", committer.String())
53 if commit.Commit.ChangedId != "" {
54 fmt.Fprintf(&payload, "change-id %s\n", commit.Commit.ChangedId)
55 }
56 fmt.Fprintf(&payload, "\n%s", commit.Commit.Message)
57
58 return VerifySignature([]byte(pubKey), []byte(signature), []byte(payload.String()))
59}
60
61// SSHFingerprint computes the fingerprint of the supplied ssh pubkey.
62func SSHFingerprint(pubKey string) (string, error) {
63 pk, _, _, _, err := ssh.ParseAuthorizedKey([]byte(pubKey))
64 if err != nil {
65 return "", err
66 }
67
68 hash := sha256.Sum256(pk.Marshal())
69 return "SHA256:" + base64.StdEncoding.EncodeToString(hash[:]), nil
70}