fuzz: target for onion_message

Fuzz the decoding and encoding of onion_message.

tests/fuzz/fuzz-wire-onion_message.c

@@ -0,0 +1,38 @@
+#include "config.h"
+#include <ccan/mem/mem.h>
+#include <tests/fuzz/libfuzz.h>
+#include <tests/fuzz/wire.h>
+#include <wire/peer_wire.h>
+
+struct onion_message {
+	struct pubkey blinding;
+	u8 *onionmsg;
+};
+
+static void *encode(const tal_t *ctx, const struct onion_message *s)
+{
+	return towire_onion_message(ctx, &s->blinding, s->onionmsg);
+}
+
+static struct onion_message *decode(const tal_t *ctx, const void *p)
+{
+	struct onion_message *s = tal(ctx, struct onion_message);
+
+	if (fromwire_onion_message(s, p, &s->blinding, &s->onionmsg))
+		return s;
+	return tal_free(s);
+}
+
+static bool equal(const struct onion_message *x, const struct onion_message *y)
+{
+	if (memcmp(&x->blinding, &y->blinding, sizeof(x->blinding)) != 0)
+		return false;
+	return memeq(x->onionmsg, tal_bytelen(x->onionmsg), y->onionmsg,
+		     tal_bytelen(y->onionmsg));
+}
+
+void run(const u8 *data, size_t size)
+{
+	test_decode_encode(data, size, WIRE_ONION_MESSAGE,
+			   struct onion_message);
+}