plumbing/object: fix pgp signature encoder/decoder

The way of reading pgp signatures was searching for pgp begin line in
the header. This caused problems when this string appeared and was not
part of the signature. For example if it appears in the message as an
example or is part of the author name the decoder starts treating it as
a signature. In this state the code was not able to notice then the
header ended so it entered in an infinite loop searching for pgp end
string.

Now it uses the same method as original git. Searches for gpgsig section
in header and starts getting all lines until the next part.

In encoder the string used to add signatures was incorrect. It is now
changed to the proper "gpgsig" string instead of "pgpsig".

Signed-off-by: Javi Fontan <jfontan@gmail.com>

Author: jfontan

plumbing/object/commit.go

@@ -17,8 +17,9 @@ import (
 )
 
 const (
-	beginpgp string = "-----BEGIN PGP SIGNATURE-----"
-	endpgp   string = "-----END PGP SIGNATURE-----"
+	beginpgp  string = "-----BEGIN PGP SIGNATURE-----"
+	endpgp    string = "-----END PGP SIGNATURE-----"
+	headerpgp string = "gpgsig"
 )
 
 // Hash represents the hash of an object
@@ -181,23 +182,13 @@ func (c *Commit) Decode(o plumbing.EncodedObject) (err error) {
 		}
 
 		if pgpsig {
-			// Check if it's the end of a PGP signature.
-			if bytes.Contains(line, []byte(endpgp)) {
-				c.PGPSignature += endpgp + "\n"
-				pgpsig = false
-			} else {
-				// Trim the left padding.
+			if len(line) > 0 && line[0] == ' ' {
 				line = bytes.TrimLeft(line, " ")
 				c.PGPSignature += string(line)
+				continue
+			} else {
+				pgpsig = false
 			}
-			continue
-		}
-
-		// Check if it's the beginning of a PGP signature.
-		if bytes.Contains(line, []byte(beginpgp)) {
-			c.PGPSignature += beginpgp + "\n"
-			pgpsig = true
-			continue
 		}
 
 		if !message {
@@ -217,6 +208,9 @@ func (c *Commit) Decode(o plumbing.EncodedObject) (err error) {
 				c.Author.Decode(split[1])
 			case "committer":
 				c.Committer.Decode(split[1])
+			case headerpgp:
+				c.PGPSignature += string(split[1]) + "\n"
+				pgpsig = true
 			}
 		} else {
 			c.Message += string(line)
@@ -269,13 +263,14 @@ func (b *Commit) encode(o plumbing.EncodedObject, includeSig bool) (err error) {
 	}
 
 	if b.PGPSignature != "" && includeSig {
-		if _, err = fmt.Fprint(w, "pgpsig"); err != nil {
+		if _, err = fmt.Fprint(w, "\n"+headerpgp); err != nil {
 			return err
 		}
 
 		// Split all the signature lines and write with a left padding and
 		// newline at the end.
-		lines := strings.Split(b.PGPSignature, "\n")
+		signature := strings.TrimSuffix(b.PGPSignature, "\n")
+		lines := strings.Split(signature, "\n")
 		for _, line := range lines {
 			if _, err = fmt.Fprintf(w, " %s\n", line); err != nil {
 				return err

plumbing/object/commit_test.go

@@ -324,6 +324,38 @@ RUysgqjcpT8+iQM1PblGfHR4XAhuOqN5Fx06PSaFZhqvWFezJ28/CLyX5q+oIVk=
 	err = decoded.Decode(encoded)
 	c.Assert(err, IsNil)
 	c.Assert(decoded.PGPSignature, Equals, pgpsignature)
+
+	// signature in author name
+
+	commit.PGPSignature = ""
+	commit.Author.Name = beginpgp
+	encoded = &plumbing.MemoryObject{}
+	decoded = &Commit{}
+
+	err = commit.Encode(encoded)
+	c.Assert(err, IsNil)
+
+	err = decoded.Decode(encoded)
+	c.Assert(err, IsNil)
+	c.Assert(decoded.PGPSignature, Equals, "")
+	c.Assert(decoded.Author.Name, Equals, beginpgp)
+
+	// broken signature
+
+	commit.PGPSignature = beginpgp + "\n" +
+		"some\n" +
+		"trash\n" +
+		endpgp +
+		"text\n"
+	encoded = &plumbing.MemoryObject{}
+	decoded = &Commit{}
+
+	err = commit.Encode(encoded)
+	c.Assert(err, IsNil)
+
+	err = decoded.Decode(encoded)
+	c.Assert(err, IsNil)
+	c.Assert(decoded.PGPSignature, Equals, commit.PGPSignature)
 }
 
 func (s *SuiteCommit) TestStat(c *C) {