smite: compare channel types in minimal form

smite/src/oracles/accept_channel.rs

@@ -154,8 +154,10 @@ fn verify_accept_channel(
         return Err("accept_channel does not include a channel_type".to_string());
     };
 
-    // Check that the channel type matches the one in open_channel.
-    if open_channel.tlvs.channel_type != accept_channel.tlvs.channel_type {
+    // Check that the channel type matches the one in open_channel. Convert
+    // feature vectors to minimal form before comparing.
+    let open_channel_type = open_channel.tlvs.channel_type.as_deref();
+    if open_channel_type.map(trim_features) != Some(trim_features(channel_type)) {
         return Err("accept_channel channel_type does not match open_channel".to_string());
     }
 
@@ -202,6 +204,13 @@ fn verify_accept_channel(
     )
 }
 
+/// Strips the leading zero padding from a feature vector, yielding the smallest
+/// bitmap that represents the same set of feature bits.
+fn trim_features(features: &[u8]) -> &[u8] {
+    let padding = features.iter().take_while(|byte| **byte == 0).count();
+    &features[padding..]
+}
+
 /// Verifies that the initial commitment can cover its fee and satisfies the
 /// channel reserve requirement, returning an error if it breaches either, or
 /// `Ok(())` if both are met.
@@ -495,6 +504,26 @@ mod tests {
         );
     }
 
+    #[test]
+    fn accept_channel_channel_type_padded_differently_than_open_channel() {
+        let mut oc = open_channel();
+        oc.tlvs.channel_type = Some(vec![0x00, 0x00, 0x10, 0x00]);
+        let mut ac = accept_channel();
+        ac.tlvs.channel_type = Some(vec![0x10, 0x00]);
+
+        assert_pass(&ac, Some(&pending_negotiation(oc)));
+    }
+
+    #[test]
+    fn accept_channel_empty_channel_type_padded_differently_than_open_channel() {
+        let mut oc = open_channel();
+        oc.tlvs.channel_type = Some(vec![0x00]);
+        let mut ac = accept_channel();
+        ac.tlvs.channel_type = Some(vec![]);
+
+        assert_pass(&ac, Some(&pending_negotiation(oc)));
+    }
+
     #[test]
     fn accept_channel_reserve_below_the_open_channel_dust_limit() {
         let oc = open_channel();