gossip: formalize passing of siphash_seed.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

gossipd/gossip.c

@@ -1049,25 +1049,16 @@ static struct io_plan *getroute_req(struct io_conn *conn, struct daemon *daemon,
 	u8 *out;
 	struct route_hop *hops;
 	double fuzz;
-	u8 *rawseed;
 	struct siphash_seed seed;
-	size_t seedbytes;
 
-	fromwire_gossip_getroute_request(tmpctx, msg,
+	fromwire_gossip_getroute_request(msg,
 					 &source, &destination,
 					 &msatoshi, &riskfactor, &final_cltv,
-					 &fuzz, &rawseed);
+					 &fuzz, &seed);
 	status_trace("Trying to find a route from %s to %s for %d msatoshi",
 		     pubkey_to_hexstr(tmpctx, &source),
 		     pubkey_to_hexstr(tmpctx, &destination), msatoshi);
 
-	/* Initialize siphash */
-	memset(&seed, 0, sizeof(seed));
-	seedbytes =
-		(tal_len(rawseed) > sizeof(seed)) ?	sizeof(seed) :
-		/*otherwise*/				tal_len(rawseed) ;
-	memcpy(&seed, rawseed, seedbytes);
-
 	hops = get_route(tmpctx, daemon->rstate, &source, &destination,
 			 msatoshi, 1, final_cltv,
 			 fuzz, &seed);

gossipd/gossip_wire.csv

@@ -108,8 +108,7 @@ gossip_getroute_request,,msatoshi,u32
 gossip_getroute_request,,riskfactor,u16
 gossip_getroute_request,,final_cltv,u32
 gossip_getroute_request,,fuzz,double
-gossip_getroute_request,,seedlen,u16
+gossip_getroute_request,,seed,struct siphash_seed
-gossip_getroute_request,,seed,seedlen*u8
 
 gossip_getroute_reply,3106
 gossip_getroute_reply,,num_hops,u16

lightningd/gossip_control.c

@@ -313,7 +313,7 @@ static void json_getroute(struct command *cmd, const char *buffer, const jsmntok
 	 * be selected) at the cost of increasing the probability of
 	 * selecting the higher-fee paths. */
 	double fuzz = 75.0;
-	u8 *seed = tal_arrz(cmd, u8, sizeof(struct siphash_seed));
+	struct siphash_seed seed;
 
 	if (!json_get_params(cmd, buffer, params,
 			     "id", &idtok,
@@ -373,13 +373,17 @@ static void json_getroute(struct command *cmd, const char *buffer, const jsmntok
 	fuzz = fuzz / 100.0;
 
 	if (seedtok) {
-		tal_resize(&seed, seedtok->end - seedtok->start);
+		if (seedtok->end - seedtok->start > sizeof(seed))
-		memcpy(seed, buffer + seedtok->start,
+			command_fail(cmd,
+				     "seed must be < %zu bytes", sizeof(seed));
+
+		memset(&seed, 0, sizeof(seed));
+		memcpy(&seed, buffer + seedtok->start,
 		       seedtok->end - seedtok->start);
 	} else
-		randombytes_buf(seed, tal_len(seed));
+		randombytes_buf(&seed, sizeof(seed));
 
-	u8 *req = towire_gossip_getroute_request(cmd, &source, &destination, msatoshi, riskfactor*1000, cltv, &fuzz, seed);
+	u8 *req = towire_gossip_getroute_request(cmd, &source, &destination, msatoshi, riskfactor*1000, cltv, &fuzz, &seed);
 	subd_req(ld->gossip, ld->gossip, req, -1, 0, json_getroute_reply, cmd);
 	command_still_pending(cmd);
 }

lightningd/payalgo.c

@@ -220,11 +220,11 @@ static void json_pay_getroute_reply(struct subd *gossip UNUSED,
  * false if resolved now. */
 static bool json_pay_try(struct pay *pay)
 {
-	u8 *seed;
 	u8 *req;
 	struct command *cmd = pay->cmd;
 	struct timeabs now = time_now();
 	struct json_result *data;
+	struct siphash_seed seed;
 
 	/* If too late anyway, fail now. */
 	if (time_after(now, pay->expiry)) {
@@ -243,8 +243,7 @@ static bool json_pay_try(struct pay *pay)
 	pay->try_parent = tal(pay, char);
 
 	/* Generate random seed */
-	seed = tal_arr(pay->try_parent, u8, sizeof(struct siphash_seed));
+	randombytes_buf(&seed, sizeof(seed));
-	randombytes_buf(seed, tal_len(seed));
 
 	++pay->getroute_tries;
 
@@ -256,7 +255,7 @@ static bool json_pay_try(struct pay *pay)
 					     pay->riskfactor,
 					     pay->min_final_cltv_expiry,
 					     &pay->fuzz,
-					     seed);
+					     &seed);
 	subd_req(pay->try_parent, cmd->ld->gossip, req, -1, 0, json_pay_getroute_reply, pay);
 
 	return true;

wire/fromwire.c

@@ -4,6 +4,7 @@
 #include <bitcoin/shadouble.h>
 #include <bitcoin/tx.h>
 #include <ccan/build_assert/build_assert.h>
+#include <ccan/crypto/siphash24/siphash24.h>
 #include <ccan/endian/endian.h>
 #include <ccan/mem/mem.h>
 #include <ccan/tal/str/str.h>
@@ -256,3 +257,9 @@ struct bitcoin_tx *fromwire_bitcoin_tx(const tal_t *ctx,
 {
 	return pull_bitcoin_tx(ctx, cursor, max);
 }
+
+void fromwire_siphash_seed(const u8 **cursor, size_t *max,
+			   struct siphash_seed *seed)
+{
+	fromwire(cursor, max, seed, sizeof(*seed));
+}

wire/towire.c

@@ -3,6 +3,7 @@
 #include <bitcoin/shadouble.h>
 #include <bitcoin/tx.h>
 #include <ccan/crypto/ripemd160/ripemd160.h>
+#include <ccan/crypto/siphash24/siphash24.h>
 #include <ccan/endian/endian.h>
 #include <ccan/mem/mem.h>
 #include <ccan/tal/tal.h>
@@ -168,3 +169,8 @@ void towire_bitcoin_tx(u8 **pptr, const struct bitcoin_tx *tx)
 	towire_u8_array(pptr, lin, tal_len(lin));
 	tal_free(tmpctx);
 }
+
+void towire_siphash_seed(u8 **pptr, const struct siphash_seed *seed)
+{
+	towire(pptr, seed, sizeof(*seed));
+}

wire/wire.h

@@ -20,6 +20,7 @@ struct bitcoin_blkid;
 struct bitcoin_txid;
 struct preimage;
 struct ripemd160;
+struct siphash_seed;
 
 /* Makes generate-wire.py work */
 typedef char wirestring;
@@ -60,6 +61,7 @@ void towire_u8_array(u8 **pptr, const u8 *arr, size_t num);
 
 void towire_bitcoin_tx(u8 **pptr, const struct bitcoin_tx *tx);
 void towire_wirestring(u8 **pptr, const char *str);
+void towire_siphash_seed(u8 **cursor, const struct siphash_seed *seed);
 
 const u8 *fromwire(const u8 **cursor, size_t *max, void *copy, size_t n);
 u8 fromwire_u8(const u8 **cursor, size_t *max);
@@ -93,7 +95,8 @@ void fromwire_pad(const u8 **cursor, size_t *max, size_t num);
 
 void fromwire_u8_array(const u8 **cursor, size_t *max, u8 *arr, size_t num);
 char *fromwire_wirestring(const tal_t *ctx, const u8 **cursor, size_t *max);
-
 struct bitcoin_tx *fromwire_bitcoin_tx(const tal_t *ctx,
 				       const u8 **cursor, size_t *max);
+void fromwire_siphash_seed(const u8 **cursor, size_t *max,
+			   struct siphash_seed *seed);
 #endif /* LIGHTNING_WIRE_WIRE_H */