Simplify onion message codec

eclair-core/src/main/scala/fr/acinq/eclair/wire/protocol/MessageOnion.scala

@@ -122,11 +122,10 @@ object MessageOnionCodecs {
 
   def messageOnionPerHopPayloadCodec(isLastPacket: Boolean): Codec[PerHopPayload] = if (isLastPacket) finalPerHopPayloadCodec.upcast[PerHopPayload] else relayPerHopPayloadCodec.upcast[PerHopPayload]
 
-  val messageOnionPacketCodec: Codec[OnionRoutingPacket] =
-    (variableSizePrefixedBytes(uint16.xmap(_ - 66, _ + 66),
-      ("version" | uint8) ~
-        ("publicKey" | bytes(33)),
-      ("onionPayload" | bytes)) ~
-      ("hmac" | bytes32) flattenLeftPairs).as[OnionRoutingPacket]
+  val messageOnionPacketCodec: Codec[OnionRoutingPacket] = variableSizeBytes(uint16, bytes).exmap[OnionRoutingPacket](
+    // The Sphinx packet header contains a version (1 byte), a public key (33 bytes) and a mac (32 bytes) -> total 66 bytes
+    bytes => OnionRoutingCodecs.onionRoutingPacketCodec(bytes.length.toInt - 66).decode(bytes.bits).map(_.value),
+    onion => OnionRoutingCodecs.onionRoutingPacketCodec(onion.payload.length.toInt).encode(onion).map(_.bytes)
+  )
 
 }

eclair-core/src/test/scala/fr/acinq/eclair/wire/protocol/CommonCodecsSpec.scala

@@ -196,6 +196,57 @@ class CommonCodecsSpec extends AnyFunSuite {
     }
   }
 
+  test("encode/decode bytevector32") {
+    val testCases = Seq(
+      (hex"0000000000000000000000000000000000000000000000000000000000000000", Some(ByteVector32.Zeroes)),
+      (hex"0101010101010101010101010101010101010101010101010101010101010101", Some(ByteVector32(hex"0101010101010101010101010101010101010101010101010101010101010101"))),
+      (hex"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff", Some(ByteVector32(hex"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"))),
+      // Ignore additional trailing bytes
+      (hex"000000000000000000000000000000000000000000000000000000000000000000", Some(ByteVector32.Zeroes)),
+      (hex"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff00", Some(ByteVector32(hex"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"))),
+      // Not enough bytes
+      (hex"00000000000000000000000000000000000000000000000000000000000000", None),
+      (hex"", None)
+    )
+
+    for ((encoded, expected_opt) <- testCases) {
+      expected_opt match {
+        case Some(expected) =>
+          val decoded = bytes32.decode(encoded.bits).require.value
+          assert(decoded === expected)
+          assert(expected.bytes === bytes32.encode(decoded).require.bytes)
+        case None =>
+          assert(bytes32.decode(encoded.bits).isFailure)
+      }
+    }
+  }
+
+  test("encode/decode bytevector64") {
+    val testCases = Seq(
+      (hex"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000", Some(ByteVector64.Zeroes)),
+      (hex"01010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101", Some(ByteVector64(hex"01010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101"))),
+      (hex"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff", Some(ByteVector64(hex"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"))),
+      // Ignore additional trailing bytes
+      (hex"0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000", Some(ByteVector64.Zeroes)),
+      (hex"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff00", Some(ByteVector64(hex"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"))),
+      // Not enough bytes
+      (hex"000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000", None),
+      (hex"00000000000000000000000000000000000000000000000000000000000000", None),
+      (hex"", None)
+    )
+
+    for ((encoded, expected_opt) <- testCases) {
+      expected_opt match {
+        case Some(expected) =>
+          val decoded = bytes64.decode(encoded.bits).require.value
+          assert(decoded === expected)
+          assert(expected.bytes === bytes64.encode(decoded).require.bytes)
+        case None =>
+          assert(bytes64.decode(encoded.bits).isFailure)
+      }
+    }
+  }
+
   test("encode/decode with private key codec") {
     val value = PrivateKey(randomBytes32())
     val wire = privateKey.encode(value).require

eclair-core/src/test/scala/fr/acinq/eclair/wire/protocol/MessageOnionCodecsSpec.scala

@@ -51,19 +51,39 @@ class MessageOnionCodecsSpec extends AnyFunSuiteLike {
     assert(finalPerHopPayloadCodec.decode(serialized.bits).require.value === payload)
   }
 
-  test("onion packet can be any size"){
+  test("onion packet can be any size") {
     { // small onion
-      val onion = OnionRoutingPacket(1, hex"032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991", hex"012345679abcdef", ByteVector32(hex"0000111122223333444455556666777788889999aaaabbbbccccddddeeee0000"))
-      val serialized = hex"004a01032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e6686809910012345679abcdef0000111122223333444455556666777788889999aaaabbbbccccddddeeee0000"
+      val onion = OnionRoutingPacket(1, hex"032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991", hex"0012345679abcdef", ByteVector32(hex"0000111122223333444455556666777788889999aaaabbbbccccddddeeee0000"))
+      val serialized = hex"004a 01 032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991 0012345679abcdef 0000111122223333444455556666777788889999aaaabbbbccccddddeeee0000"
       assert(messageOnionPacketCodec.encode(onion).require.bytes === serialized)
       assert(messageOnionPacketCodec.decode(serialized.bits).require.value === onion)
     }
     { // larger onion
-      val onion = OnionRoutingPacket(2, hex"027f31ebc5462c1fdce1b737ecff52d37d75dea43ce11c74d25aa297165faa2007", hex"012345679abcdef012345679abcdef012345679abcdef012345679abcdef012345679abcdef", ByteVector32(hex"eeee0000111122223333444455556666777788889999aaaabbbbccccddddeeee"))
-      val serialized = hex"006802027f31ebc5462c1fdce1b737ecff52d37d75dea43ce11c74d25aa297165faa20070012345679abcdef012345679abcdef012345679abcdef012345679abcdef012345679abcdefeeee0000111122223333444455556666777788889999aaaabbbbccccddddeeee"
+      val onion = OnionRoutingPacket(2, hex"027f31ebc5462c1fdce1b737ecff52d37d75dea43ce11c74d25aa297165faa2007", hex"0012345679abcdef012345679abcdef012345679abcdef012345679abcdef012345679abcdef", ByteVector32(hex"eeee0000111122223333444455556666777788889999aaaabbbbccccddddeeee"))
+      val serialized = hex"0068 02 027f31ebc5462c1fdce1b737ecff52d37d75dea43ce11c74d25aa297165faa2007 0012345679abcdef012345679abcdef012345679abcdef012345679abcdef012345679abcdef eeee0000111122223333444455556666777788889999aaaabbbbccccddddeeee"
       assert(messageOnionPacketCodec.encode(onion).require.bytes === serialized)
       assert(messageOnionPacketCodec.decode(serialized.bits).require.value === onion)
     }
+    { // onion with trailing additional bytes
+      val onion = OnionRoutingPacket(0, hex"032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991", hex"ffffffff", ByteVector32.Zeroes)
+      val serialized = hex"0046 00 032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991 ffffffff 0000000000000000000000000000000000000000000000000000000000000000 0a01020000030400000000"
+      assert(messageOnionPacketCodec.encode(onion).require.bytes === serialized.dropRight(11))
+      assert(messageOnionPacketCodec.decode(serialized.bits).require.value === onion)
+    }
+    { // onion with empty payload
+      val onion = OnionRoutingPacket(0, hex"032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991", hex"", ByteVector32.Zeroes)
+      val serialized = hex"0042 00 032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991 0000000000000000000000000000000000000000000000000000000000000000"
+      assert(messageOnionPacketCodec.encode(onion).require.bytes === serialized)
+      assert(messageOnionPacketCodec.decode(serialized.bits).require.value === onion)
+    }
+    { // onion length too big
+      val serialized = hex"0048 00 032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991 ffffffff 0000000000000000000000000000000000000000000000000000000000000000"
+      assert(messageOnionPacketCodec.decode(serialized.bits).isFailure)
+    }
+    { // onion length way too big
+      val serialized = hex"00ff 00 032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991 ffffffff 0000000000000000000000000000000000000000000000000000000000000000"
+      assert(messageOnionPacketCodec.decode(serialized.bits).isFailure)
+    }
   }
 
 }