Do not validate non spec obu-size

Author: JoTurk

codecs/av1_depacketizer.go

@@ -138,22 +138,29 @@ func (d *AV1Depacketizer) Unmarshal(payload []byte) (buff []byte, err error) {
 
 		// obu_has_size_field should be set to 0 for AV1 RTP packets.
 		// But we still check it to be sure, if we get obu size we just use it, instead of calculating it.
-		if obuHeader.HasSizeField {
+		if obuHeader.HasSizeField { //nolint:nestif
 			obuSize, n, err := obu.ReadLeb128(obuBuffer[obuHeader.Size():])
 			if err != nil {
 				return nil, err
 			}
 
-			// We validate the obu_size_field if it is present.
 			sizeFromOBUSize := obuHeader.Size() + int(obuSize) + int(n) //nolint:gosec
 			if lengthField != sizeFromOBUSize {
-				return nil, fmt.Errorf(
-					"%w: OBU size %d does not match calculated size %d",
-					errShortPacket, obuSize, sizeFromOBUSize,
-				)
-			}
+				payloadOffset := obuHeader.Size() + int(n) //nolint:gosec // n is a single digit
+				if payloadOffset > len(obuBuffer) {
+					return nil, fmt.Errorf(
+						"%w: OBU header/size exceeds payload length %d",
+						errShortPacket, len(obuBuffer),
+					)
+				}
 
-			buff = append(buff, obuBuffer...)
+				obuPayloadSize := len(obuBuffer) - payloadOffset
+				buff = append(buff, obuHeader.Marshal()...)
+				buff = append(buff, obu.WriteToLeb128(uint(obuPayloadSize))...) // nolint: gosec // G104
+				buff = append(buff, obuBuffer[payloadOffset:]...)
+			} else {
+				buff = append(buff, obuBuffer...)
+			}
 		} else {
 			obuHeader.HasSizeField = true
 			buff = append(buff, obuHeader.Marshal()...)

codecs/av1_depacketizer_test.go

@@ -114,6 +114,7 @@ func TestAV1Depacketizer_validateOBUSize(t *testing.T) {
 	tests := []struct {
 		name    string
 		payload []byte
+		expect  []byte
 		err     error
 	}{
 		{
@@ -135,7 +136,11 @@ func TestAV1Depacketizer_validateOBUSize(t *testing.T) {
 				0x04,             // LEB128 size
 				0x03, 0x01, 0x02, // OBU data
 			},
-			err: errShortPacket,
+			expect: []byte{
+				0x22,             // OBU header
+				0x03,             // Corrected size
+				0x03, 0x01, 0x02, // OBU data
+			},
 		},
 		{
 			name: "OBU size smaller than length field",
@@ -146,15 +151,26 @@ func TestAV1Depacketizer_validateOBUSize(t *testing.T) {
 				0x02,             // LEB128 size
 				0x03, 0x01, 0x02, // OBU data
 			},
-			err: errShortPacket,
+			expect: []byte{
+				0x22,             // OBU header
+				0x03,             // Corrected size
+				0x03, 0x01, 0x02, // OBU data
+			},
 		},
 	}
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			d := AV1Depacketizer{}
-			_, err := d.Unmarshal(tt.payload)
-			assert.ErrorIs(t, err, tt.err)
+			obu, err := d.Unmarshal(tt.payload)
+			if tt.err != nil {
+				assert.ErrorIs(t, err, tt.err)
+
+				return
+			}
+
+			assert.NoError(t, err)
+			assert.Equal(t, tt.expect, obu)
 		})
 	}
 }