plumbing: object/tag, add signature and verification support

plumbing/object/commit.go

@@ -223,6 +223,10 @@ func (c *Commit) Decode(o plumbing.EncodedObject) (err error) {
 
 // Encode transforms a Commit into a plumbing.EncodedObject.
 func (b *Commit) Encode(o plumbing.EncodedObject) error {
+	return b.encode(o, true)
+}
+
+func (b *Commit) encode(o plumbing.EncodedObject, includeSig bool) error {
 	o.SetType(plumbing.CommitObject)
 	w, err := o.Writer()
 	if err != nil {
@@ -257,7 +261,7 @@ func (b *Commit) Encode(o plumbing.EncodedObject) error {
 		return err
 	}
 
-	if b.PGPSignature != "" {
+	if b.PGPSignature != "" && includeSig {
 		if _, err = fmt.Fprint(w, "pgpsig"); err != nil {
 			return err
 		}
@@ -325,12 +329,9 @@ func (c *Commit) Verify(armoredKeyRing string) (*openpgp.Entity, error) {
 	// Extract signature.
 	signature := strings.NewReader(c.PGPSignature)
 
-	// Remove signature. Keep only the commit components.
-	c.PGPSignature = ""
-
-	// Encode commit and get a reader object.
 	encoded := &plumbing.MemoryObject{}
-	if err := c.Encode(encoded); err != nil {
+	// Encode commit components, excluding signature and get a reader object.
+	if err := c.encode(encoded, false); err != nil {
 		return nil, err
 	}
 	er, err := encoded.Reader()

plumbing/object/tag.go

@@ -6,6 +6,9 @@ import (
 	"fmt"
 	"io"
 	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"
@@ -30,6 +33,8 @@ type Tag struct {
 	Tagger Signature
 	// Message is an arbitrary text message.
 	Message string
+	// PGPSignature is the PGP signature of the tag.
+	PGPSignature string
 	// TargetType is the object type of the target.
 	TargetType plumbing.ObjectType
 	// Target is the hash of the target object.
@@ -124,13 +129,46 @@ func (t *Tag) Decode(o plumbing.EncodedObject) (err error) {
 	if err != nil {
 		return err
 	}
-	t.Message = string(data)
+
+	var pgpsig bool
+	// Check if data contains PGP signature.
+	if bytes.Contains(data, []byte(beginpgp)) {
+		// Split the lines at newline.
+		messageAndSig := bytes.Split(data, []byte("\n"))
+
+		for _, l := range messageAndSig {
+			if pgpsig {
+				if bytes.Contains(l, []byte(endpgp)) {
+					t.PGPSignature += endpgp + "\n"
+					pgpsig = false
+				} else {
+					t.PGPSignature += string(l) + "\n"
+				}
+				continue
+			}
+
+			// Check if it's the beginning of a PGP signature.
+			if bytes.Contains(l, []byte(beginpgp)) {
+				t.PGPSignature += beginpgp + "\n"
+				pgpsig = true
+				continue
+			}
+
+			t.Message += string(l) + "\n"
+		}
+	} else {
+		t.Message = string(data)
+	}
 
 	return nil
 }
 
 // Encode transforms a Tag into a plumbing.EncodedObject.
 func (t *Tag) Encode(o plumbing.EncodedObject) error {
+	return t.encode(o, true)
+}
+
+func (t *Tag) encode(o plumbing.EncodedObject, includeSig bool) error {
 	o.SetType(plumbing.TagObject)
 	w, err := o.Writer()
 	if err != nil {
@@ -156,6 +194,16 @@ func (t *Tag) Encode(o plumbing.EncodedObject) error {
 		return err
 	}
 
+	if t.PGPSignature != "" && includeSig {
+		// Split all the signature lines and write with a newline at the end.
+		lines := strings.Split(t.PGPSignature, "\n")
+		for _, line := range lines {
+			if _, err = fmt.Fprintf(w, "%s\n", line); err != nil {
+				return err
+			}
+		}
+	}
+
 	return err
 }
 
@@ -225,6 +273,31 @@ 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)
+
+	encoded := &plumbing.MemoryObject{}
+	// Encode tag components, excluding signature and get a reader object.
+	if err := t.encode(encoded, false); 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

plumbing/object/tag_test.go

@@ -285,3 +285,94 @@ func (s *TagSuite) TestLongTagNameSerialization(c *C) {
 	c.Assert(err, IsNil)
 	c.Assert(decoded.Name, Equals, longName)
 }
+
+func (s *TagSuite) TestPGPSignatureSerialization(c *C) {
+	encoded := &plumbing.MemoryObject{}
+	decoded := &Tag{}
+	tag := s.tag(c, plumbing.NewHash("b742a2a9fa0afcfa9a6fad080980fbc26b007c69"))
+
+	pgpsignature := `-----BEGIN PGP SIGNATURE-----
+
+iQEcBAABAgAGBQJTZbQlAAoJEF0+sviABDDrZbQH/09PfE51KPVPlanr6q1v4/Ut
+LQxfojUWiLQdg2ESJItkcuweYg+kc3HCyFejeDIBw9dpXt00rY26p05qrpnG+85b
+hM1/PswpPLuBSr+oCIDj5GMC2r2iEKsfv2fJbNW8iWAXVLoWZRF8B0MfqX/YTMbm
+ecorc4iXzQu7tupRihslbNkfvfciMnSDeSvzCpWAHl7h8Wj6hhqePmLm9lAYqnKp
+8S5B/1SSQuEAjRZgI4IexpZoeKGVDptPHxLLS38fozsyi0QyDyzEgJxcJQVMXxVi
+RUysgqjcpT8+iQM1PblGfHR4XAhuOqN5Fx06PSaFZhqvWFezJ28/CLyX5q+oIVk=
+=EFTF
+-----END PGP SIGNATURE-----
+`
+	tag.PGPSignature = pgpsignature
+
+	err := tag.Encode(encoded)
+	c.Assert(err, IsNil)
+
+	err = decoded.Decode(encoded)
+	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)
+}