plumbing: object/tag, add signature verification

2 files changed, 94 insertions, 0 deletions

diff --git a/plumbing/object/tag.go b/plumbing/object/tag.go
index 6295205..9b4250f 100644
--- a/plumbing/object/tag.go
+++ b/plumbing/object/tag.go
@@ -8,6 +8,8 @@ import (
 	stdioutil "io/ioutil"
 	"strings"
 
+	"golang.org/x/crypto/openpgp"
+
 	"gopkg.in/src-d/go-git.v4/plumbing"
 	"gopkg.in/src-d/go-git.v4/plumbing/storer"
 	"gopkg.in/src-d/go-git.v4/utils/ioutil"
@@ -267,6 +269,33 @@ func (t *Tag) String() string {
 	)
 }
 
+// Verify performs PGP verification of the tag with a provided armored
+// keyring and returns openpgp.Entity associated with verifying key on success.
+func (t *Tag) Verify(armoredKeyRing string) (*openpgp.Entity, error) {
+	keyRingReader := strings.NewReader(armoredKeyRing)
+	keyring, err := openpgp.ReadArmoredKeyRing(keyRingReader)
+	if err != nil {
+		return nil, err
+	}
+
+	// Extract signature.
+	signature := strings.NewReader(t.PGPSignature)
+
+	// Remove signature. Keep only the tag components.
+	t.PGPSignature = ""
+
+	encoded := &plumbing.MemoryObject{}
+	if err := t.Encode(encoded); err != nil {
+		return nil, err
+	}
+	er, err := encoded.Reader()
+	if err != nil {
+		return nil, err
+	}
+
+	return openpgp.CheckArmoredDetachedSignature(keyring, er, signature)
+}
+
 // TagIter provides an iterator for a set of tags.
 type TagIter struct {
 	storer.EncodedObjectIter
diff --git a/plumbing/object/tag_test.go b/plumbing/object/tag_test.go
index edd23f5..9900093 100644
--- a/plumbing/object/tag_test.go
+++ b/plumbing/object/tag_test.go
@@ -311,3 +311,68 @@ RUysgqjcpT8+iQM1PblGfHR4XAhuOqN5Fx06PSaFZhqvWFezJ28/CLyX5q+oIVk=
 	c.Assert(err, IsNil)
 	c.Assert(decoded.PGPSignature, Equals, pgpsignature)
 }
+
+func (s *TagSuite) TestVerify(c *C) {
+	ts := time.Unix(1511524851, 0)
+	loc, _ := time.LoadLocation("Asia/Kolkata")
+	tag := &Tag{
+		Name:   "v0.2",
+		Tagger: Signature{Name: "Sunny", Email: "me@darkowlzz.space", When: ts.In(loc)},
+		Message: `This is a signed tag
+`,
+		TargetType: plumbing.CommitObject,
+		Target:     plumbing.NewHash("064f92fe00e70e6b64cb358a65039daa4b6ae8d2"),
+		PGPSignature: `
+-----BEGIN PGP SIGNATURE-----
+
+iQFHBAABCAAxFiEEoRt6IzxHaZkkUslhQyLeMqcmyU4FAloYCg8THG1lQGRhcmtv
+d2x6ei5zcGFjZQAKCRBDIt4ypybJTs0cCACjQZe2610t3gfbUPbgQiWDL9uvlCeb
+sNSeTC6hLAFSvHTMqLr/6RpiLlfQXyATD7TZUH0DUSLsERLheG82OgVxkOTzPCpy
+GL6iGKeZ4eZ1KiV+SBPjqizC9ShhGooPUw9oUSVdj4jsaHDdDHtY63Pjl0KvJmms
+OVi9SSxjeMbmaC81C8r0ZuOLTXJh/JRKh2BsehdcnK3736BK+16YRD7ugXLpkQ5d
+nsCFVbuYYoLMoJL5NmEun0pbUrpY+MI8VPK0f9HV5NeaC4NksC+ke/xYMT+P2lRL
+CN+9zcCIU+mXr2fCl1xOQcnQzwOElObDxpDcPcxVn0X+AhmPc+uj0mqD
+=l75D
+-----END PGP SIGNATURE-----
+`,
+	}
+
+	armoredKeyRing := `
+-----BEGIN PGP PUBLIC KEY BLOCK-----
+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+=FPev
+-----END PGP PUBLIC KEY BLOCK-----
+`
+
+	e, err := tag.Verify(armoredKeyRing)
+	c.Assert(err, IsNil)
+
+	_, ok := e.Identities["Sunny <me@darkowlzz.space>"]
+	c.Assert(ok, Equals, true)
+}