Reject 0-value trampoline payments (#1851)

It doesn't make any sense to forward empty payments. This is also checked when adding the htlcs in the outgoing channel, but we should fail early here.
ACINQ · Jun 28, 2021 · 85ed433 · 85ed433
1 parent 45204e2
commit 85ed433
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diff --git a/eclair-core/src/main/scala/fr/acinq/eclair/payment/relay/NodeRelay.scala b/eclair-core/src/main/scala/fr/acinq/eclair/payment/relay/NodeRelay.scala
@@ -111,6 +111,8 @@ object NodeRelay {
       Some(TrampolineExpiryTooSoon)
     } else if (payloadOut.invoiceFeatures.isDefined && payloadOut.paymentSecret.isEmpty) {
       Some(InvalidOnionPayload(UInt64(8), 0)) // payment secret field is missing
+    } else if (payloadOut.amountToForward <= MilliSatoshi(0)) {
+      Some(InvalidOnionPayload(UInt64(2), 0))
     } else {
       None
     }

diff --git a/eclair-core/src/test/scala/fr/acinq/eclair/payment/relay/NodeRelayerSpec.scala b/eclair-core/src/test/scala/fr/acinq/eclair/payment/relay/NodeRelayerSpec.scala
@@ -353,6 +353,39 @@ class NodeRelayerSpec extends ScalaTestWithActorTestKit(ConfigFactory.load("appl
     register.expectNoMessage(100 millis)
   }
 
+  test("fail to relay when amount is 0 (single-part)") { f =>
+    import f._
+
+    val p = createValidIncomingPacket(5000000 msat, 5000000 msat, CltvExpiry(500000), 0 msat, CltvExpiry(490000))
+    val (nodeRelayer, _) = f.createNodeRelay(p)
+    nodeRelayer ! NodeRelay.Relay(p)
+
+    val fwd = register.expectMessageType[Register.Forward[CMD_FAIL_HTLC]]
+    assert(fwd.channelId === p.add.channelId)
+    assert(fwd.message === CMD_FAIL_HTLC(p.add.id, Right(InvalidOnionPayload(UInt64(2), 0)), commit = true))
+
+    register.expectNoMessage(100 millis)
+  }
+
+  test("fail to relay when amount is 0 (multi-part)") { f =>
+    import f._
+
+    val p = Seq(
+      createValidIncomingPacket(4000000 msat, 5000000 msat, CltvExpiry(500000), 0 msat, CltvExpiry(490000)),
+      createValidIncomingPacket(1000000 msat, 5000000 msat, CltvExpiry(500000), 0 msat, CltvExpiry(490000))
+    )
+    val (nodeRelayer, _) = f.createNodeRelay(p.head)
+    p.foreach(p => nodeRelayer ! NodeRelay.Relay(p))
+
+    p.foreach { p =>
+      val fwd = register.expectMessageType[Register.Forward[CMD_FAIL_HTLC]]
+      assert(fwd.channelId === p.add.channelId)
+      assert(fwd.message === CMD_FAIL_HTLC(p.add.id, Right(InvalidOnionPayload(UInt64(2), 0)), commit = true))
+    }
+
+    register.expectNoMessage(100 millis)
+  }
+
   test("fail to relay because outgoing balance isn't sufficient (low fees)") { f =>
     import f._