Add support for a new big-endian handshake format

Because of strange dicisions in the past, fastd currently uses little endian
type and length values in its handshake. As the common network byte order is
big endian, changing the handshake format would be preferable.

This commit adds support for a new big-endian handshake. For now, fastd will
continue to send little-endian handshakes so ensure backwarts compatiblity, but
if it receives a big-endian handshake, it will respond with a big-endian one.

1 files changed, 13 insertions, 11 deletions

diff --git a/src/protocols/ec25519_fhmqvc/handshake.c b/src/protocols/ec25519_fhmqvc/handshake.c
index 5d3e57e..0b547f4 100644
--- a/src/protocols/ec25519_fhmqvc/handshake.c
+++ b/src/protocols/ec25519_fhmqvc/handshake.c
@@ -329,7 +329,7 @@ static void clear_shared_handshake_key(const fastd_peer_t *peer) {
 
 /** Sends a reply to an initial handshake (type 1) */
 static void respond_handshake(const fastd_socket_t *sock, const fastd_peer_address_t *local_addr, const fastd_peer_address_t *remote_addr, fastd_peer_t *peer,
-			      const aligned_int256_t *peer_handshake_key, const fastd_method_info_t *method) {
+			      const aligned_int256_t *peer_handshake_key, const fastd_method_info_t *method, bool little_endian) {
 	pr_debug("responding handshake with %P[%I]...", peer, remote_addr);
 
 	const handshake_key_t *handshake_key = &ctx.protocol_state->handshake_key;
@@ -337,7 +337,7 @@ static void respond_handshake(const fastd_socket_t *sock, const fastd_peer_addre
 	if (!update_shared_handshake_key(peer, handshake_key, peer_handshake_key))
 		return;
 
-	fastd_buffer_t buffer = fastd_handshake_new_reply(2, method, true, 4*(4+PUBLICKEYBYTES) + 2*(4+HASHBYTES));
+	fastd_handshake_buffer_t buffer = fastd_handshake_new_reply(2, little_endian, method, true, 4*(4+PUBLICKEYBYTES) + 2*(4+HASHBYTES));
 
 	fastd_handshake_add(&buffer, RECORD_SENDER_KEY, PUBLICKEYBYTES, &conf.protocol_config->key.public);
 	fastd_handshake_add(&buffer, RECORD_RECIPIENT_KEY, PUBLICKEYBYTES, &peer->key->key);
@@ -352,10 +352,10 @@ static void respond_handshake(const fastd_socket_t *sock, const fastd_peer_addre
 	}
 
 	uint8_t *mac = fastd_handshake_add_zero(&buffer, RECORD_TLV_MAC, HASHBYTES);
-	fastd_hmacsha256(&hmacbuf, peer->protocol_state->shared_handshake_key.w, fastd_handshake_tlv_data(&buffer), fastd_handshake_tlv_len(&buffer));
+	fastd_hmacsha256(&hmacbuf, peer->protocol_state->shared_handshake_key.w, fastd_handshake_tlv_data(&buffer.buffer), fastd_handshake_tlv_len(&buffer.buffer));
 	memcpy(mac, hmacbuf.b, HASHBYTES);
 
-	fastd_send_handshake(sock, local_addr, remote_addr, peer, buffer);
+	fastd_send_handshake(sock, local_addr, remote_addr, peer, buffer.buffer);
 }
 
 /** Sends a reply to a handshake response (type 2) */
@@ -398,7 +398,7 @@ static void finish_handshake(fastd_socket_t *sock, const fastd_peer_address_t *l
 		       &peer->key->key, &sigma, compat ? NULL : shared_handshake_key.w, handshake_key->serial))
 		return;
 
-	fastd_buffer_t buffer = fastd_handshake_new_reply(3, method, false, 4*(4+PUBLICKEYBYTES) + 2*(4+HASHBYTES));
+	fastd_handshake_buffer_t buffer = fastd_handshake_new_reply(3, handshake->little_endian, method, false, 4*(4+PUBLICKEYBYTES) + 2*(4+HASHBYTES));
 
 	fastd_handshake_add(&buffer, RECORD_SENDER_KEY, PUBLICKEYBYTES, &conf.protocol_config->key.public);
 	fastd_handshake_add(&buffer, RECORD_RECIPIENT_KEY, PUBLICKEYBYTES, &peer->key->key);
@@ -408,7 +408,7 @@ static void finish_handshake(fastd_socket_t *sock, const fastd_peer_address_t *l
 	if (!compat) {
 		fastd_sha256_t hmacbuf;
 		uint8_t *mac = fastd_handshake_add_zero(&buffer, RECORD_TLV_MAC, HASHBYTES);
-		fastd_hmacsha256(&hmacbuf, shared_handshake_key.w, fastd_handshake_tlv_data(&buffer), fastd_handshake_tlv_len(&buffer));
+		fastd_hmacsha256(&hmacbuf, shared_handshake_key.w, fastd_handshake_tlv_data(&buffer.buffer), fastd_handshake_tlv_len(&buffer.buffer));
 		memcpy(mac, hmacbuf.b, HASHBYTES);
 	}
 	else {
@@ -417,7 +417,7 @@ static void finish_handshake(fastd_socket_t *sock, const fastd_peer_address_t *l
 		fastd_handshake_add(&buffer, RECORD_T, HASHBYTES, hmacbuf.b);
 	}
 
-	fastd_send_handshake(sock, local_addr, remote_addr, peer, buffer);
+	fastd_send_handshake(sock, local_addr, remote_addr, peer, buffer.buffer);
 }
 
 /** Handles a reply to a handshake response (type 3) */
@@ -521,7 +521,7 @@ static fastd_peer_t * match_sender_key(const fastd_socket_t *sock, const fastd_p
 void fastd_protocol_ec25519_fhmqvc_handshake_init(fastd_socket_t *sock, const fastd_peer_address_t *local_addr, const fastd_peer_address_t *remote_addr, fastd_peer_t *peer) {
 	fastd_protocol_ec25519_fhmqvc_maintenance();
 
-	fastd_buffer_t buffer = fastd_handshake_new_init(3*(4+PUBLICKEYBYTES) /* sender key, recipient key, handshake key */);
+	fastd_handshake_buffer_t buffer = fastd_handshake_new_init(3*(4+PUBLICKEYBYTES) /* sender key, recipient key, handshake key */);
 
 	fastd_handshake_add(&buffer, RECORD_SENDER_KEY, PUBLICKEYBYTES, &conf.protocol_config->key.public);
 
@@ -539,7 +539,7 @@ void fastd_protocol_ec25519_fhmqvc_handshake_init(fastd_socket_t *sock, const fa
 	if (!peer || !fastd_peer_is_established(peer))
 		fastd_peer_exec_shell_command(&conf.on_connect, peer, (local_addr && local_addr->sa.sa_family) ? local_addr : sock->bound_addr, remote_addr);
 
-	fastd_send_handshake(sock, local_addr, remote_addr, peer, buffer);
+	fastd_send_handshake(sock, local_addr, remote_addr, peer, buffer.buffer);
 }
 
 
@@ -557,6 +557,7 @@ static inline void print_unknown_key(const fastd_peer_address_t *addr, const uns
 /** Data attached to an asynchronous on-verify run */
 typedef struct verify_data {
 	aligned_int256_t peer_handshake_key;		/**< The public key of the peer being verified */
+	bool little_endian;				/**< The handshake endianess */
 } verify_data_t;
 
 /** Adds a dynamic peer for an unknown key */
@@ -614,6 +615,7 @@ static bool handle_dynamic(fastd_socket_t *sock, const fastd_peer_address_t *loc
 	verify_data_t verify_data;
 	memset(&verify_data, 0, sizeof(verify_data));
 	memcpy(&verify_data.peer_handshake_key, handshake->records[RECORD_SENDER_HANDSHAKE_KEY].data, PUBLICKEYBYTES);
+	verify_data.little_endian = handshake->little_endian;
 
 	fastd_tristate_t verified = fastd_verify_peer(peer, sock, local_addr, remote_addr, method, &verify_data, sizeof(verify_data));
 
@@ -640,7 +642,7 @@ void fastd_protocol_ec25519_fhmqvc_handle_verify_return(fastd_peer_t *peer, fast
 
 	peer->last_handshake_response_timeout = ctx.now + MIN_HANDSHAKE_INTERVAL;
 	peer->last_handshake_response_address = *remote_addr;
-	respond_handshake(sock, local_addr, remote_addr, peer, &data->peer_handshake_key, method);
+	respond_handshake(sock, local_addr, remote_addr, peer, &data->peer_handshake_key, method, data->little_endian);
 }
 
 #else
@@ -726,7 +728,7 @@ void fastd_protocol_ec25519_fhmqvc_handshake_handle(fastd_socket_t *sock, const
 
 		peer->last_handshake_response_timeout = ctx.now + MIN_HANDSHAKE_INTERVAL;
 		peer->last_handshake_response_address = *remote_addr;
-		respond_handshake(sock, local_addr, remote_addr, peer, &peer_handshake_key, method);
+		respond_handshake(sock, local_addr, remote_addr, peer, &peer_handshake_key, method, handshake->little_endian);
 		return;
 	}