tests: Add fuzzing harness for CHKDF_HMAC_SHA256_L32

Author: practicalswift

src/Makefile.test.include

@@ -36,6 +36,7 @@ FUZZ_TARGETS = \
   test/fuzz/crypto_aes256 \
   test/fuzz/crypto_aes256cbc \
   test/fuzz/crypto_common \
+  test/fuzz/crypto_hkdf_hmac_sha256_l32 \
   test/fuzz/crypto_poly1305 \
   test/fuzz/cuckoocache \
   test/fuzz/decode_tx \
@@ -507,6 +508,12 @@ test_fuzz_crypto_common_LDADD = $(FUZZ_SUITE_LD_COMMON)
 test_fuzz_crypto_common_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 test_fuzz_crypto_common_SOURCES = test/fuzz/crypto_common.cpp
 
+test_fuzz_crypto_hkdf_hmac_sha256_l32_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
+test_fuzz_crypto_hkdf_hmac_sha256_l32_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+test_fuzz_crypto_hkdf_hmac_sha256_l32_LDADD = $(FUZZ_SUITE_LD_COMMON)
+test_fuzz_crypto_hkdf_hmac_sha256_l32_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
+test_fuzz_crypto_hkdf_hmac_sha256_l32_SOURCES = test/fuzz/crypto_hkdf_hmac_sha256_l32.cpp
+
 test_fuzz_crypto_poly1305_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 test_fuzz_crypto_poly1305_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_crypto_poly1305_LDADD = $(FUZZ_SUITE_LD_COMMON)

src/test/fuzz/crypto_hkdf_hmac_sha256_l32.cpp

@@ -0,0 +1,25 @@
+// 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 <crypto/hkdf_sha256_32.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+
+    const std::vector<uint8_t> initial_key_material = ConsumeRandomLengthByteVector(fuzzed_data_provider);
+
+    CHKDF_HMAC_SHA256_L32 hkdf_hmac_sha256_l32(initial_key_material.data(), initial_key_material.size(), fuzzed_data_provider.ConsumeRandomLengthString(1024));
+    while (fuzzed_data_provider.ConsumeBool()) {
+        std::vector<uint8_t> out(32);
+        hkdf_hmac_sha256_l32.Expand32(fuzzed_data_provider.ConsumeRandomLengthString(128), out.data());
+    }
+}