Add fuzzing for Witness struct

Author: RCasatta

.github/workflows/fuzz.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        fuzz_target: [deser_net_msg, deserialize_address, deserialize_amount, deserialize_block, deserialize_psbt, deserialize_script, deserialize_transaction, outpoint_string, uint128_fuzz, script_bytes_to_asm_fmt]
+        fuzz_target: [deser_net_msg, deserialize_address, deserialize_amount, deserialize_block, deserialize_psbt, deserialize_script, deserialize_transaction, deserialize_witness, outpoint_string, uint128_fuzz, script_bytes_to_asm_fmt]
     steps:
       - name: Install test dependencies
         run: sudo apt-get update -y && sudo apt-get install -y binutils-dev libunwind8-dev libcurl4-openssl-dev libelf-dev libdw-dev cmake gcc libiberty-dev

fuzz/Cargo.toml

@@ -59,3 +59,7 @@ path = "fuzz_targets/uint128_fuzz.rs"
 [[bin]]
 name = "script_bytes_to_asm_fmt"
 path = "fuzz_targets/script_bytes_to_asm_fmt.rs"
+
+[[bin]]
+name = "deserialize_witness"
+path = "fuzz_targets/deserialize_witness.rs"

fuzz/fuzz_targets/deserialize_transaction.rs

@@ -10,7 +10,7 @@ fn do_test(data: &[u8]) {
             let len = ser.len();
             let calculated_weight = tx.get_weight();
             for input in &mut tx.input {
-                input.witness = vec![];
+                input.witness = bitcoin::blockdata::witness::Witness::default();
             }
             let no_witness_len = bitcoin::consensus::encode::serialize(&tx).len();
             // For 0-input transactions, `no_witness_len` will be incorrect because

fuzz/fuzz_targets/deserialize_witness.rs

@@ -0,0 +1,59 @@
+extern crate bitcoin;
+
+use bitcoin::consensus::{serialize, deserialize};
+use bitcoin::blockdata::witness::Witness;
+
+fn do_test(data: &[u8]) {
+    let w: Result<Witness, _> = deserialize(data);
+    if let Ok(witness) = w {
+        let serialized = serialize(&witness);
+        assert_eq!(data, serialized);
+    }
+}
+
+#[cfg(feature = "afl")]
+#[macro_use] extern crate afl;
+#[cfg(feature = "afl")]
+fn main() {
+    fuzz!(|data| {
+        do_test(&data);
+    });
+}
+
+#[cfg(feature = "honggfuzz")]
+#[macro_use] extern crate honggfuzz;
+#[cfg(feature = "honggfuzz")]
+fn main() {
+    loop {
+        fuzz!(|data| {
+            do_test(data);
+        });
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    fn extend_vec_from_hex(hex: &str, out: &mut Vec<u8>) {
+        let mut b = 0;
+        for (idx, c) in hex.as_bytes().iter().enumerate() {
+            b <<= 4;
+            match *c {
+                b'A'..=b'F' => b |= c - b'A' + 10,
+                b'a'..=b'f' => b |= c - b'a' + 10,
+                b'0'..=b'9' => b |= c - b'0',
+                _ => panic!("Bad hex"),
+            }
+            if (idx & 1) == 1 {
+                out.push(b);
+                b = 0;
+            }
+        }
+    }
+
+    #[test]
+    fn duplicate_crash() {
+        let mut a = Vec::new();
+        extend_vec_from_hex("00", &mut a);
+        super::do_test(&a);
+    }
+}