From 5b11f76e00db4c7e46a37ded6239f2f6810e4616 Mon Sep 17 00:00:00 2001
From: Bastien Teinturier <31281497+t-bast@users.noreply.github.com>
Date: Fri, 3 Nov 2023 14:05:54 +0100
Subject: [PATCH] Ignore duplicate dual-funding signatures (#2770)

If our peer sends us some `tx_signatures` that we already received, we
can safely ignore them.
---
 .../channel/fsm/ChannelOpenDualFunded.scala   |  3 +++
 ...WaitForDualFundingConfirmedStateSpec.scala | 23 +++++++++++++++++--
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/eclair-core/src/main/scala/fr/acinq/eclair/channel/fsm/ChannelOpenDualFunded.scala b/eclair-core/src/main/scala/fr/acinq/eclair/channel/fsm/ChannelOpenDualFunded.scala
index 2802b7aeac..d95a3f80da 100644
--- a/eclair-core/src/main/scala/fr/acinq/eclair/channel/fsm/ChannelOpenDualFunded.scala
+++ b/eclair-core/src/main/scala/fr/acinq/eclair/channel/fsm/ChannelOpenDualFunded.scala
@@ -473,6 +473,9 @@ trait ChannelOpenDualFunded extends DualFundingHandlers with ErrorHandlers {
                   val d1 = DATA_WAIT_FOR_DUAL_FUNDING_CONFIRMED(commitments1, d.localPushAmount, d.remotePushAmount, d.waitingSince, d.lastChecked, RbfStatus.NoRbf, d.deferred)
                   stay() using d1 storing() sending signingSession1.localSigs calling publishFundingTx(signingSession1.fundingTx)
               }
+            case _ if d.commitments.all.exists(_.fundingTxId == txSigs.txId) =>
+              log.debug("ignoring tx_signatures that we already received for txId={}", txSigs.txId)
+              stay()
             case _ =>
               log.debug("rejecting unexpected tx_signatures for txId={}", txSigs.txId)
               reportRbfFailure(d.rbfStatus, UnexpectedFundingSignatures(d.channelId))
diff --git a/eclair-core/src/test/scala/fr/acinq/eclair/channel/states/c/WaitForDualFundingConfirmedStateSpec.scala b/eclair-core/src/test/scala/fr/acinq/eclair/channel/states/c/WaitForDualFundingConfirmedStateSpec.scala
index 64c77476e8..de59a118b6 100644
--- a/eclair-core/src/test/scala/fr/acinq/eclair/channel/states/c/WaitForDualFundingConfirmedStateSpec.scala
+++ b/eclair-core/src/test/scala/fr/acinq/eclair/channel/states/c/WaitForDualFundingConfirmedStateSpec.scala
@@ -127,11 +127,30 @@ class WaitForDualFundingConfirmedStateSpec extends TestKitBaseClass with Fixture
 
     val aliceSigs = alice.stateData.asInstanceOf[DATA_WAIT_FOR_DUAL_FUNDING_CONFIRMED].latestFundingTx.sharedTx.localSigs
     alice2bob.forward(bob, aliceSigs)
-    bob2alice.expectMsgType[TxAbort]
+    bob2alice.expectNoMessage(100 millis)
 
     val bobSigs = bob.stateData.asInstanceOf[DATA_WAIT_FOR_DUAL_FUNDING_CONFIRMED].latestFundingTx.sharedTx.localSigs
     bob2alice.forward(alice, bobSigs)
-    alice2bob.expectMsgType[TxAbort]
+    alice2bob.expectNoMessage(100 millis)
+
+    assert(alice.stateName == WAIT_FOR_DUAL_FUNDING_CONFIRMED)
+    assert(bob.stateName == WAIT_FOR_DUAL_FUNDING_CONFIRMED)
+  }
+
+  test("recv TxSignatures (duplicate, rbf attempt)", Tag(ChannelStateTestsTags.DualFunding)) { f =>
+    import f._
+
+    val aliceSigs = alice.stateData.asInstanceOf[DATA_WAIT_FOR_DUAL_FUNDING_CONFIRMED].latestFundingTx.sharedTx.localSigs
+    val bobSigs = bob.stateData.asInstanceOf[DATA_WAIT_FOR_DUAL_FUNDING_CONFIRMED].latestFundingTx.sharedTx.localSigs
+    val rbfTx = testBumpFundingFees(f)
+
+    alice2bob.forward(bob, aliceSigs)
+    alice2bob.forward(bob, rbfTx.localSigs)
+    bob2alice.expectNoMessage(100 millis)
+
+    bob2alice.forward(alice, bobSigs)
+    bob2alice.forward(alice, rbfTx.remoteSigs)
+    alice2bob.expectNoMessage(100 millis)
 
     assert(alice.stateName == WAIT_FOR_DUAL_FUNDING_CONFIRMED)
     assert(bob.stateName == WAIT_FOR_DUAL_FUNDING_CONFIRMED)