object: fix panic when reading object header

When the first line of the pgp signature is an empty line or some header
is malformed it crashes as there's no data for the header element. For
example, if author name is "\n".

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

2 files changed, 45 insertions, 5 deletions

diff --git a/plumbing/object/commit.go b/plumbing/object/commit.go
index 00ae3f1..e254342 100644
--- a/plumbing/object/commit.go
+++ b/plumbing/object/commit.go
@@ -199,17 +199,23 @@ func (c *Commit) Decode(o plumbing.EncodedObject) (err error) {
 			}
 
 			split := bytes.SplitN(line, []byte{' '}, 2)
+
+			var data []byte
+			if len(split) == 2 {
+				data = split[1]
+			}
+
 			switch string(split[0]) {
 			case "tree":
-				c.TreeHash = plumbing.NewHash(string(split[1]))
+				c.TreeHash = plumbing.NewHash(string(data))
 			case "parent":
-				c.ParentHashes = append(c.ParentHashes, plumbing.NewHash(string(split[1])))
+				c.ParentHashes = append(c.ParentHashes, plumbing.NewHash(string(data)))
 			case "author":
-				c.Author.Decode(split[1])
+				c.Author.Decode(data)
 			case "committer":
-				c.Committer.Decode(split[1])
+				c.Committer.Decode(data)
 			case headerpgp:
-				c.PGPSignature += string(split[1]) + "\n"
+				c.PGPSignature += string(data) + "\n"
 				pgpsig = true
 			}
 		} else {
diff --git a/plumbing/object/commit_test.go b/plumbing/object/commit_test.go
index b5dfbe3..e72b703 100644
--- a/plumbing/object/commit_test.go
+++ b/plumbing/object/commit_test.go
@@ -325,6 +325,22 @@ RUysgqjcpT8+iQM1PblGfHR4XAhuOqN5Fx06PSaFZhqvWFezJ28/CLyX5q+oIVk=
 	c.Assert(err, IsNil)
 	c.Assert(decoded.PGPSignature, Equals, pgpsignature)
 
+	// signature with extra empty line, it caused "index out of range" when
+	// parsing it
+
+	pgpsignature2 := "\n" + pgpsignature
+
+	commit.PGPSignature = pgpsignature2
+	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, pgpsignature2)
+
 	// signature in author name
 
 	commit.PGPSignature = ""
@@ -461,3 +477,21 @@ func (s *SuiteCommit) TestPatchCancel(c *C) {
 	c.Assert(err, ErrorMatches, "operation canceled")
 
 }
+
+func (s *SuiteCommit) TestMalformedHeader(c *C) {
+	encoded := &plumbing.MemoryObject{}
+	decoded := &Commit{}
+	commit := *s.Commit
+
+	commit.PGPSignature = "\n"
+	commit.Author.Name = "\n"
+	commit.Author.Email = "\n"
+	commit.Committer.Name = "\n"
+	commit.Committer.Email = "\n"
+
+	err := commit.Encode(encoded)
+	c.Assert(err, IsNil)
+
+	err = decoded.Decode(encoded)
+	c.Assert(err, IsNil)
+}