tests: Add fuzzing harness for SigHasLowR(...) and ecdsa_signature_parse_der_lax(...)

src/test/fuzz/secp256k1_ecdsa_signature_parse_der_lax.cpp

@@ -0,0 +1,33 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <key.h>
+#include <secp256k1.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <cstdint>
+#include <vector>
+
+bool SigHasLowR(const secp256k1_ecdsa_signature* sig);
+int ecdsa_signature_parse_der_lax(const secp256k1_context* ctx, secp256k1_ecdsa_signature* sig, const unsigned char* input, size_t inputlen);
+
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+    const std::vector<uint8_t> signature_bytes = ConsumeRandomLengthByteVector(fuzzed_data_provider);
+    if (signature_bytes.data() == nullptr) {
+        return;
+    }
+    secp256k1_context* secp256k1_context_verify = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY);
+    secp256k1_ecdsa_signature sig_der_lax;
+    const bool parsed_der_lax = ecdsa_signature_parse_der_lax(secp256k1_context_verify, &sig_der_lax, signature_bytes.data(), signature_bytes.size()) == 1;
+    if (parsed_der_lax) {
+        ECC_Start();
+        (void)SigHasLowR(&sig_der_lax);
+        ECC_Stop();
+    }
+    secp256k1_context_destroy(secp256k1_context_verify);
+}