1 files changed, 52 insertions, 0 deletions
diff --git a/third_party/rust/regex-automata/tests/fuzz/dense.rs b/third_party/rust/regex-automata/tests/fuzz/dense.rs
new file mode 100644
index 0000000000..213891b3e8
--- /dev/null
+++ b/third_party/rust/regex-automata/tests/fuzz/dense.rs
@@ -0,0 +1,52 @@
+// This test was found by a fuzzer input that crafted a way to provide
+// an invalid serialization of ByteClasses that passed our verification.
+// Specifically, the verification step in the deserialization of ByteClasses
+// used an iterator that depends on part of the serialized bytes being correct.
+// (Specifically, the encoding of the number of classes.)
+#[test]
+fn invalid_byte_classes() {
+    let data = include_bytes!(
+        "testdata/deserialize_dense_crash-9486fb7c8a93b12c12a62166b43d31640c0208a9",
+    );
+    let _ = fuzz_run(data);
+}
+
+#[test]
+fn invalid_byte_classes_min() {
+    let data = include_bytes!(
+        "testdata/deserialize_dense_minimized-from-9486fb7c8a93b12c12a62166b43d31640c0208a9",
+    );
+    let _ = fuzz_run(data);
+}
+
+// This is the code from the fuzz target. Kind of sucks to duplicate it here,
+// but this is fundamentally how we interpret the date.
+fn fuzz_run(given_data: &[u8]) -> Option<()> {
+    use regex_automata::dfa::Automaton;
+
+    if given_data.len() < 2 {
+        return None;
+    }
+    let haystack_len = usize::from(given_data[0]);
+    let haystack = given_data.get(1..1 + haystack_len)?;
+    let given_dfa_bytes = given_data.get(1 + haystack_len..)?;
+
+    // We help the fuzzer along by adding a preamble to the bytes that should
+    // at least make these first parts valid. The preamble expects a very
+    // specific sequence of bytes, so it makes sense to just force this.
+    let label = "rust-regex-automata-dfa-dense\x00\x00\x00";
+    assert_eq!(0, label.len() % 4);
+    let endianness_check = 0xFEFFu32.to_ne_bytes().to_vec();
+    let version_check = 2u32.to_ne_bytes().to_vec();
+    let mut dfa_bytes: Vec<u8> = vec![];
+    dfa_bytes.extend(label.as_bytes());
+    dfa_bytes.extend(&endianness_check);
+    dfa_bytes.extend(&version_check);
+    dfa_bytes.extend(given_dfa_bytes);
+    // This is the real test: checking that any input we give to
+    // DFA::from_bytes will never result in a panic.
+    let (dfa, _) =
+        regex_automata::dfa::dense::DFA::from_bytes(&dfa_bytes).ok()?;
+    let _ = dfa.try_search_fwd(&regex_automata::Input::new(haystack));
+    Some(())
+}