alice.pds.demo.boltless.dev
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crypto: helpers to verify commit signatures
Signed-off-by: Anirudh Oppiliappan <anirudh@tangled.sh>
author
Anirudh Oppiliappan
committer
Tangled
date
(May 31, 2025, 12:03 PM UTC)
commit
d0fbcd5e
d0fbcd5e403b4cb1cf73b2a02ac4e624f9fef1a0
parent
ea1b3729
ea1b37296145f86a892f2fd880ece1288ad2da01
+74
-1
+70
crypto/verify.go
+70
crypto/verify.go
···
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+
package crypto
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+
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import (
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"bytes"
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"crypto/sha256"
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"encoding/base64"
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"fmt"
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"strings"
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+
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"github.com/hiddeco/sshsig"
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"golang.org/x/crypto/ssh"
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"tangled.sh/tangled.sh/core/types"
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)
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func VerifySignature(pubKey, signature, payload []byte) (error, bool) {
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pub, _, _, _, err := ssh.ParseAuthorizedKey(pubKey)
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if err != nil {
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return fmt.Errorf("failed to parse public key: %w", err), false
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}
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sig, err := sshsig.Unarmor(signature)
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if err != nil {
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return fmt.Errorf("failed to parse signature: %w", err), false
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}
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buf := bytes.NewBuffer(payload)
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sshsig.Verify(buf, sig, pub, sshsig.HashSHA256, "git")
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return err, err == nil
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}
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// VerifyCommitSignature reconstructs the payload used to sign a commit. This is
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// essentially the git cat-file output but without the gpgsig header.
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//
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// Caveats: signature verification will fail on commits with more than one parent,
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// i.e. merge commits, because types.NiceDiff doesn't carry more than one Parent field
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// and we are unable to reconstruct the payload correctly.
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//
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// Ideally this should directly operate on an *object.Commit.
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func VerifyCommitSignature(pubKey string, commit types.NiceDiff) (error, bool) {
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signature := commit.Commit.PGPSignature
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author := bytes.NewBuffer([]byte{})
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committer := bytes.NewBuffer([]byte{})
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commit.Commit.Author.Encode(author)
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commit.Commit.Committer.Encode(committer)
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payload := strings.Builder{}
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fmt.Fprintf(&payload, "tree %s\n", commit.Commit.Tree)
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fmt.Fprintf(&payload, "parent %s\n", commit.Commit.Parent)
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fmt.Fprintf(&payload, "author %s\n", author.String())
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fmt.Fprintf(&payload, "committer %s\n", committer.String())
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if commit.Commit.ChangedId != "" {
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fmt.Fprintf(&payload, "change-id %s\n", commit.Commit.ChangedId)
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}
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fmt.Fprintf(&payload, "\n%s", commit.Commit.Message)
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return VerifySignature([]byte(pubKey), []byte(signature), []byte(payload.String()))
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}
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// SSHFingerprint computes the fingerprint of the supplied ssh pubkey.
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func SSHFingerprint(pubKey string) (string, error) {
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pk, _, _, _, err := ssh.ParseAuthorizedKey([]byte(pubKey))
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if err != nil {
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return "", err
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}
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hash := sha256.Sum256(pk.Marshal())
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return "SHA256:" + base64.StdEncoding.EncodeToString(hash[:]), nil
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}
+2
-1
go.mod
+2
-1
go.mod
···
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github.com/go-git/go-git/v5 v5.14.0
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github.com/google/uuid v1.6.0
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github.com/gorilla/sessions v1.4.0
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github.com/hiddeco/sshsig v0.2.0
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github.com/ipfs/go-cid v0.5.0
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github.com/lestrrat-go/jwx/v2 v2.1.6
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github.com/mattn/go-sqlite3 v1.14.24
···
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github.com/urfave/cli/v3 v3.3.3
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github.com/whyrusleeping/cbor-gen v0.3.1
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github.com/yuin/goldmark v1.4.13
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golang.org/x/crypto v0.38.0
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golang.org/x/net v0.39.0
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golang.org/x/xerrors v0.0.0-20240903120638-7835f813f4da
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tangled.sh/icyphox.sh/atproto-oauth v0.0.0-20250526154904-3906c5336421
···
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go.uber.org/atomic v1.11.0 // indirect
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go.uber.org/multierr v1.11.0 // indirect
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go.uber.org/zap v1.27.0 // indirect
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golang.org/x/crypto v0.38.0 // indirect
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golang.org/x/exp v0.0.0-20250408133849-7e4ce0ab07d0 // indirect
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golang.org/x/sync v0.13.0 // indirect
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golang.org/x/sys v0.33.0 // indirect
+2
go.sum
+2
go.sum
···
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160
github.com/hashicorp/golang-lru/v2 v2.0.7/go.mod h1:QeFd9opnmA6QUJc5vARoKUSoFhyfM2/ZepoAG6RGpeM=
161
161
github.com/hexops/gotextdiff v1.0.3 h1:gitA9+qJrrTCsiCl7+kh75nPqQt1cx4ZkudSTLoUqJM=
162
162
github.com/hexops/gotextdiff v1.0.3/go.mod h1:pSWU5MAI3yDq+fZBTazCSJysOMbxWL1BSow5/V2vxeg=
163
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github.com/hiddeco/sshsig v0.2.0 h1:gMWllgKCITXdydVkDL+Zro0PU96QI55LwUwebSwNTSw=
164
+
github.com/hiddeco/sshsig v0.2.0/go.mod h1:nJc98aGgiH6Yql2doqH4CTBVHexQA40Q+hMMLHP4EqE=
163
165
github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
164
166
github.com/ianlancetaylor/demangle v0.0.0-20200824232613-28f6c0f3b639/go.mod h1:aSSvb/t6k1mPoxDqO4vJh6VOCGPwU4O0C2/Eqndh1Sc=
165
167
github.com/ipfs/bbloom v0.0.4 h1:Gi+8EGJ2y5qiD5FbsbpX/TMNcJw8gSqr7eyjHa4Fhvs=