Improve fuzz test coverage by building a resolver

Author: TheBlueMatt

fuzz/src/parse.rs

@@ -9,9 +9,14 @@
 
 use bitcoin::Network;
 
-use bitcoin_payment_instructions::hrn_resolution::DummyHrnResolver;
+use bitcoin_payment_instructions::amount::Amount;
+use bitcoin_payment_instructions::hrn::HumanReadableName;
+use bitcoin_payment_instructions::hrn_resolution::{
+	DummyHrnResolver, HrnResolution, HrnResolutionFuture, HrnResolver, LNURLResolutionFuture,
+};
 use bitcoin_payment_instructions::PaymentInstructions;
 
+use std::sync::Mutex;
 use std::future::Future;
 use std::pin::Pin;
 use std::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
@@ -25,13 +30,86 @@ fn clone_fn(p: *const ()) -> RawWaker {
 
 fn dummy_fn(_: *const ()) {}
 
+struct Resolver<'a>(
+	Mutex<(Option<Result<HrnResolution, &'static str>>, Option<Result<&'a [u8], &'static str>>)>,
+);
+
+impl HrnResolver for Resolver<'_> {
+	fn resolve_hrn<'a>(&'a self, _: &'a HumanReadableName) -> HrnResolutionFuture<'a> {
+		Box::pin(async {
+			let us = self.0.lock().unwrap();
+			us.0.take().unwrap()
+		})
+	}
+
+	fn resolve_lnurl<'a>(&'a self, _: String, _: Amount, _: [u8; 32]) -> LNURLResolutionFuture<'a> {
+		Box::pin(async {
+			let us = self.0.lock().unwrap();
+			us.1.take().unwrap()
+		})
+	}
+}
+
 #[inline]
-pub fn do_test(data: &[u8]) {
+pub fn do_test(mut data: &[u8]) {
+	if data.len() < 2 {
+		return;
+	}
+
+	let mut bolt11 = None;
+
+	let resolution = if (data[0] & 0b1100_0000) == 0b1100_0000 {
+		Err("HRN resolution failed in fuzzing")
+	} else if (data[0] & 0b1100_0000) == 0b1000_0000 {
+		let result_len = (((data[0] & 0b0011_1111) as usize) << 8) | (data[1] as usize);
+		if data.len() <= result_len + 2 {
+			return;
+		}
+		let result = data[2..result_len + 2].to_vec();
+
+		data = &data[result_len + 2..];
+		HrnResolution::DNSSEC { result, proof: Some(vec![8; 32]) }
+	} else {
+		if data.len() <= 16 + 2 {
+			return;
+		}
+		let lnurl_resolution_fails = (data[0] & 0b1100_0000) == 0b0100_0000;
+		let min = Amount::from_milli_sats(u64::from_le_bytes((&data[..8]).try_into().unwrap()));
+		data = &data[8..];
+		let max = Amount::from_milli_sats(u64::from_le_bytes((&data[..8]).try_into().unwrap()));
+		data = &data[8..];
+
+		let bolt11_len = ((data[0] as usize) << 8) | (data[1] as usize);
+		if data.len() <= bolt11_len + 2 {
+			return;
+		}
+
+		bolt11 = if lnurl_resolution_fails {
+			Some(Err("LNURL resolution failed in fuzzing"))
+		} else {
+			Some(Ok(&data[2..bolt11_len + 2]))
+		};
+		data = &data[bolt11_len + 2..];
+
+		let mut expected_description_hash = [0; 32];
+		expected_description_hash[31] = 42;
+
+		HrnResolution::LNURLPay {
+			min_value: if let Ok(min) = min { min } else { return },
+			max_value: if let Ok(max) = max { max } else { return },
+			expected_description_hash,
+			recipient_description: Some("Payment in fuzzing".to_owned()),
+			callback: "https://callback.uri/in/fuzzing".to_owned(),
+		}
+	};
+
+	let resolver = Resolver(Mutex::new((Some(resolution), bolt11)));
+
 	if let Ok(s) = std::str::from_utf8(data) {
 		let waker = unsafe { Waker::from_raw(clone_fn(std::ptr::null())) };
 
-		let fut = PaymentInstructions::parse(s, Network::Bitcoin, &DummyHrnResolver, true);
-		// With a DummyHrnResolver, all instructions should resolve on the first `poll`.
+		let fut = PaymentInstructions::parse(s, Network::Bitcoin, &resolver, true);
+		// With our resolver, all instructions should resolve on the first `poll`.
 		let res = Future::poll(Pin::new(&mut Box::pin(fut)), &mut Context::from_waker(&waker));
 		assert!(matches!(res, Poll::Ready(_)));