[Zellic Audit] Fix Pushing Data

src/builder.rs

@@ -354,11 +354,18 @@ impl NotU8Pushable for usize {
 }
 impl NotU8Pushable for Vec<u8> {
     fn bitcoin_script_push(self, builder: StructuredScript) -> StructuredScript {
-        // Push the element with a minimal opcode if it is a single number.
-        if self.len() == 1 {
-            builder.push_int(self[0].into())
-        } else {
-            builder.push_slice(PushBytesBuf::try_from(self.to_vec()).unwrap())
+        match self[..] {
+            [x] if (1..=16).contains(&x) => {
+                // use decicated opcode for pushing a single byte with value 1 <= x <= 16.
+                // Note that we don't use a special opcode used for pushing the value 0 - pushing this
+                // as an integer would push an empty array rather than a 0x00 value
+                builder.push_int(x.into())
+            }
+            [129] => {
+                // 129 is equivalent to -1 when interpreting as signed - use dedicated opcode for pushing this
+                builder.push_int(-1)
+            }
+            _ => builder.push_slice(PushBytesBuf::try_from(self).unwrap()),
         }
     }
 }
@@ -375,11 +382,20 @@ impl NotU8Pushable for ::bitcoin::XOnlyPublicKey {
 impl NotU8Pushable for Witness {
     fn bitcoin_script_push(self, mut builder: StructuredScript) -> StructuredScript {
         for element in self.into_iter() {
-            // Push the element with a minimal opcode if it is a single number.
-            if element.len() == 1 {
-                builder = builder.push_int(element[0].into());
-            } else {
-                builder = builder.push_slice(PushBytesBuf::try_from(element.to_vec()).unwrap());
+            match element[..] {
+                [x] if (1..=16).contains(&x) => {
+                    // use decicated opcode for pushing a single byte with value 1 <= x <= 16.
+                    // Note that we don't use a special opcode used for pushing the value 0 - pushing this
+                    // as an integer would push an empty array rather than a 0x00 value
+                    builder = builder.push_int(x.into());
+                }
+                [129] => {
+                    // 129 is equivalent to -1 when interpreting as signed - use dedicated opcode for pushing this
+                    builder = builder.push_int(-1);
+                }
+                _ => {
+                    builder = builder.push_slice(PushBytesBuf::try_from(element.to_vec()).unwrap());
+                }
             }
         }
         builder

tests/test.rs

@@ -260,24 +260,27 @@ fn test_non_optimal_opcodes() {
 #[test]
 fn test_push_witness() {
     for i in 0..512 {
-        let mut witness = Witness::new();
-        let vec = vec![129u8; i];
-        witness.push(vec.clone());
-        let script = script! {
-            { witness }
-        };
-        let reference_script = script! {
-            { vec }
-        };
-        assert_eq!(
-            script.compile().as_bytes(),
-            reference_script.compile().as_bytes(),
-            "here"
-        );
+        for x in vec![0, 37, 42, 127, 128, 129, 211, 255] {
+            let mut witness = Witness::new();
+            let vec = vec![x; i];
+            witness.push(vec.clone());
+            let script = script! {
+                { witness }
+            };
+            let reference_script = script! {
+                { vec }
+            };
+            assert_eq!(
+                script.compile().as_bytes(),
+                reference_script.compile().as_bytes(),
+                "here"
+            );
+        }
     }
 
     let mut witness = Witness::new();
-    for i in 0..16 {
+    witness.push([]); //presentation of 0 with `consensus_encode` is [0] instead of [], but `push_int` in this repository encodes 0 as []
+    for i in 1..16 {
         let mut varint = Vec::new();
         encode::VarInt(i).consensus_encode(&mut varint).unwrap();
         witness.push(varint);
@@ -308,7 +311,8 @@ fn test_push_witness() {
 fn test_push_scriptbuf() {
     let script_buf = script! {
         { 1 }
-    }.compile();
+    }
+    .compile();
     let script = script! {
         { script_buf.clone() }
     };