From: Matt Corallo <649246+TheBlueMatt@users.noreply.github.com>
Date: Thu, 28 Apr 2022 21:56:49 +0000 (+0000)
Subject: Merge pull request #1454 from TheBlueMatt/2022-04-fuzz-underflow
X-Git-Tag: v0.0.107~49
X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=commitdiff_plain;h=dc8479a6202ea84489e51cba020a600f0a2b9695;hp=f53d13bcb8220b3ce39e51a4d20beb23b3930d1f;p=rust-lightning

Merge pull request #1454 from TheBlueMatt/2022-04-fuzz-underflow

Reject channels if the total reserves are larger than the funding
---

diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs
index cf70749ad..1cb7a689a 100644
--- a/lightning/src/ln/channel.rs
+++ b/lightning/src/ln/channel.rs
@@ -1103,14 +1103,13 @@ impl<Signer: Sign> Channel<Signer> {
 		if msg.channel_reserve_satoshis > msg.funding_satoshis {
 			return Err(ChannelError::Close(format!("Bogus channel_reserve_satoshis ({}). Must be not greater than funding_satoshis: {}", msg.channel_reserve_satoshis, msg.funding_satoshis)));
 		}
-		let funding_value = (msg.funding_satoshis - msg.channel_reserve_satoshis) * 1000;
-		if msg.push_msat > funding_value {
-			return Err(ChannelError::Close(format!("push_msat {} was larger than funding value {}", msg.push_msat, funding_value)));
+		let full_channel_value_msat = (msg.funding_satoshis - msg.channel_reserve_satoshis) * 1000;
+		if msg.push_msat > full_channel_value_msat {
+			return Err(ChannelError::Close(format!("push_msat {} was larger than channel amount minus reserve ({})", msg.push_msat, full_channel_value_msat)));
 		}
 		if msg.dust_limit_satoshis > msg.funding_satoshis {
 			return Err(ChannelError::Close(format!("dust_limit_satoshis {} was larger than funding_satoshis {}. Peer never wants payout outputs?", msg.dust_limit_satoshis, msg.funding_satoshis)));
 		}
-		let full_channel_value_msat = (msg.funding_satoshis - msg.channel_reserve_satoshis) * 1000;
 		if msg.htlc_minimum_msat >= full_channel_value_msat {
 			return Err(ChannelError::Close(format!("Minimum htlc value ({}) was larger than full channel value ({})", msg.htlc_minimum_msat, full_channel_value_msat)));
 		}
@@ -1164,6 +1163,9 @@ impl<Signer: Sign> Channel<Signer> {
 		if holder_selected_channel_reserve_satoshis < MIN_CHAN_DUST_LIMIT_SATOSHIS {
 			return Err(ChannelError::Close(format!("Suitable channel reserve not found. remote_channel_reserve was ({}). dust_limit_satoshis is ({}).", holder_selected_channel_reserve_satoshis, MIN_CHAN_DUST_LIMIT_SATOSHIS)));
 		}
+		if holder_selected_channel_reserve_satoshis * 1000 >= full_channel_value_msat {
+			return Err(ChannelError::Close(format!("Suitable channel reserve not found. remote_channel_reserve was ({}). Channel value is ({} - {}).", holder_selected_channel_reserve_satoshis, full_channel_value_msat, msg.push_msat)));
+		}
 		if msg.channel_reserve_satoshis < MIN_CHAN_DUST_LIMIT_SATOSHIS {
 			log_debug!(logger, "channel_reserve_satoshis ({}) is smaller than our dust limit ({}). We can broadcast stale states without any risk, implying this channel is very insecure for our counterparty.",
 				msg.channel_reserve_satoshis, MIN_CHAN_DUST_LIMIT_SATOSHIS);
diff --git a/lightning/src/ln/functional_tests.rs b/lightning/src/ln/functional_tests.rs
index d9756035f..60fa9c805 100644
--- a/lightning/src/ln/functional_tests.rs
+++ b/lightning/src/ln/functional_tests.rs
@@ -103,7 +103,7 @@ fn test_insane_channel_opens() {
 
 	insane_open_helper("Bogus channel_reserve_satoshis", |mut msg| { msg.channel_reserve_satoshis = msg.funding_satoshis + 1; msg });
 
-	insane_open_helper(r"push_msat \d+ was larger than funding value \d+", |mut msg| { msg.push_msat = (msg.funding_satoshis - msg.channel_reserve_satoshis) * 1000 + 1; msg });
+	insane_open_helper(r"push_msat \d+ was larger than channel amount minus reserve \(\d+\)", |mut msg| { msg.push_msat = (msg.funding_satoshis - msg.channel_reserve_satoshis) * 1000 + 1; msg });
 
 	insane_open_helper("Peer never wants payout outputs?", |mut msg| { msg.dust_limit_satoshis = msg.funding_satoshis + 1 ; msg });