Don't attempt to append zero length fragments

Before the fragmentBuffer would process zero length fragments. Since they are zero length the append would not do anything. This would result in an infinite loop.
pion · May 10, 2022 · e0b2ce3 · e0b2ce3
1 parent ba1a176
commit e0b2ce3
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Showing 2 changed files with 15 additions and 1 deletion.
diff --git a/fragment_buffer.go b/fragment_buffer.go
@@ -76,7 +76,7 @@ func (f *fragmentBuffer) pop() (content []byte, epoch uint16) {
 		for _, f := range frags {
 			if f.handshakeHeader.FragmentOffset == targetOffset {
 				fragmentEnd := (f.handshakeHeader.FragmentOffset + f.handshakeHeader.FragmentLength)
-				if fragmentEnd != f.handshakeHeader.Length {
+				if fragmentEnd != f.handshakeHeader.Length && f.handshakeHeader.FragmentLength != 0 {
 					if !appendMessage(fragmentEnd) {
 						return false
 					}

diff --git a/fragment_buffer_test.go b/fragment_buffer_test.go
@@ -73,6 +73,20 @@ func TestFragmentBuffer(t *testing.T) {
 			},
 			Epoch: 0,
 		},
+		// Assert that a zero length fragment doesn't cause the fragmentBuffer to enter an infinite loop
+		{
+			Name: "Zero Length Fragment",
+			In: [][]byte{
+				{
+					0x16, 0xfe, 0xfd, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0d, 0x00, 0x00,
+					0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+				},
+			},
+			Expected: [][]byte{
+				{0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00},
+			},
+			Epoch: 0,
+		},
 	} {
 		fragmentBuffer := newFragmentBuffer()
 		for _, frag := range test.In {