fuzz: add a fuzz target for amounts parsing

Signed-off-by: Antoine Poinsot <darosior@protonmail.com>

.gitignore

@@ -37,6 +37,8 @@ test/test_protocol
 test/test_sphinx
 tests/.pytest.restart
 tests/plugins/test_libplugin
+tests/fuzz/fuzz-*
+!tests/fuzz/fuzz-*.c
 gossip_store
 .pytest_cache
 tools/headerversions

tests/fuzz/Makefile

@@ -7,12 +7,7 @@ FUZZ_TARGETS_SRC := $(wildcard tests/fuzz/fuzz-*.c)
 FUZZ_TARGETS_OBJS := $(FUZZ_TARGETS_SRC:.c=.o)
 FUZZ_TARGETS_BIN := $(FUZZ_TARGETS_SRC:.c=)
 
-FUZZ_COMMON_OBJS :=			\
-	common/utils.o
-$(FUZZ_TARGETS_OBJS): $(COMMON_HEADERS) $(WIRE_HEADERS) $(COMMON_SRC)
-$(FUZZ_TARGETS_BIN): $(LIBFUZZ_OBJS) $(FUZZ_COMMON_OBJS) $(BITCOIN_OBJS)
-
-tests/fuzz/fuzz-addr:					\
+FUZZ_COMMON_OBJS :=					\
 	common/amount.o					\
 	common/addr.o					\
 	common/base32.o					\
@@ -22,9 +17,12 @@ tests/fuzz/fuzz-addr:					\
 	common/json_stream.o				\
 	common/wireaddr.o				\
 	common/type_to_string.o				\
+	common/utils.o					\
 	wire/fromwire.o					\
 	wire/onion_wiregen.o				\
 	wire/towire.o
+$(FUZZ_TARGETS_OBJS): $(COMMON_HEADERS) $(WIRE_HEADERS) $(COMMON_SRC)
+$(FUZZ_TARGETS_BIN): $(LIBFUZZ_OBJS) $(FUZZ_COMMON_OBJS) $(BITCOIN_OBJS)
 
 ALL_C_SOURCES += $(FUZZ_TARGETS_SRC) $(LIBFUZZ_SRC)
 ALL_FUZZ_TARGETS += $(FUZZ_TARGETS_BIN)

tests/fuzz/fuzz-amount.c

@@ -0,0 +1,61 @@
+#include <assert.h>
+#include <stdint.h>
+#include <tests/fuzz/libfuzz.h>
+
+#include <ccan/tal/tal.h>
+#include <common/amount.h>
+#include <common/utils.h>
+
+void init(int *argc, char ***argv)
+{
+}
+
+void run(const uint8_t *data, size_t size)
+{
+	struct amount_msat msat;
+	struct amount_sat sat;
+	char *string;
+	uint8_t *buf;
+	const char *fmt_msat, *fmt_msatbtc, *fmt_sat, *fmt_satbtc;
+
+
+	/* We should not crash when parsing any string. */
+
+	string = tal_arr(NULL, char, size);
+	for (size_t i = 0; i < size; i++)
+		string[i] = (char) data[i] % (CHAR_MAX + 1);
+
+	parse_amount_msat(&msat, string, tal_count(string));
+	parse_amount_sat(&sat, string, tal_count(string));
+	tal_free(string);
+
+
+	/* Same with the wire primitives. */
+
+	buf = tal_arr(NULL, uint8_t, 8);
+
+	msat = fromwire_amount_msat(&data, &size);
+	towire_amount_msat(&buf, msat);
+	sat = fromwire_amount_sat(&data, &size);
+	towire_amount_sat(&buf, sat);
+
+	tal_free(buf);
+
+
+	/* Format should inconditionally produce valid amount strings according to our
+	 * parser */
+
+	fmt_msat = fmt_amount_msat(NULL, &msat);
+	fmt_msatbtc = fmt_amount_msat_btc(NULL, &msat, true);
+	assert(parse_amount_msat(&msat, fmt_msat, tal_count(fmt_msat)));
+	assert(parse_amount_msat(&msat, fmt_msatbtc, tal_count(fmt_msatbtc)));
+	tal_free(fmt_msat);
+	tal_free(fmt_msatbtc);
+
+	fmt_sat = fmt_amount_sat(NULL, &sat);
+	fmt_satbtc = fmt_amount_sat_btc(NULL, &sat, true);
+	assert(parse_amount_sat(&sat, fmt_sat, tal_count(fmt_sat)));
+	assert(parse_amount_sat(&sat, fmt_satbtc, tal_count(fmt_satbtc)));
+	tal_free(fmt_sat);
+	tal_free(fmt_satbtc);
+}