Don't regenerate session handshake keypair for every handshake so a global state can be used; remove the concept of temporary peers

These changes will fix the possibility of a TCP-SYN-Flood-like DoS attack, at the cost of another
protocol change: as we can't count request IDs when we don't know have temporary peers, request IDs
are removed completely.

1 files changed, 198 insertions, 236 deletions

diff --git a/src/protocol_ec25519_fhmqvc.c b/src/protocol_ec25519_fhmqvc.c
index 93fd9c4..e4a0e93 100644
--- a/src/protocol_ec25519_fhmqvc.c
+++ b/src/protocol_ec25519_fhmqvc.c
@@ -58,26 +58,22 @@ struct _fastd_protocol_config {
 	ecc_public_key_256 public_key;
 };
 
-typedef enum _handshake_state {
-	HANDSHAKE_STATE_INIT,
-	HANDSHAKE_STATE_RESPONSE,
-	HANDSHAKE_STATE_ESTABLISHED
-} handshake_state;
+typedef struct _handshake_key {
+	struct timespec preferred_till;
+	struct timespec valid_till;
 
-struct _fastd_protocol_peer_config {
+	ecc_secret_key_256 secret_key;
 	ecc_public_key_256 public_key;
-};
+} handshake_key;
 
-typedef struct _protocol_handshake {
-	const fastd_peer_config *peer_config;
+struct _fastd_protocol_state {
+	handshake_key prev_handshake_key;
+	handshake_key handshake_key;
+};
 
-	handshake_state state;
-	ecc_secret_key_256 secret_key;
+struct _fastd_protocol_peer_config {
 	ecc_public_key_256 public_key;
-	ecc_public_key_256 peer_key;
-	ecc_public_key_256 sigma;
-	uint8_t shared_handshake_key[HASHBYTES];
-} protocol_handshake;
+};
 
 typedef struct _protocol_session {
 	bool handshakes_cleaned;
@@ -89,9 +85,6 @@ typedef struct _protocol_session {
 struct _fastd_protocol_peer_state {
 	protocol_session old_session;
 	protocol_session session;
-
-	protocol_handshake *initiating_handshake;
-	protocol_handshake *accepting_handshake;
 };
 
 
@@ -116,6 +109,14 @@ static inline bool read_key(uint8_t key[32], const char *hexkey) {
 	return true;
 }
 
+static inline bool is_handshake_key_valid(fastd_context *ctx, const handshake_key *handshake_key) {
+	return timespec_after(&handshake_key->valid_till, &ctx->now);
+}
+
+static inline bool is_handshake_key_preferred(fastd_context *ctx, const handshake_key *handshake_key) {
+	return timespec_after(&handshake_key->preferred_till, &ctx->now);
+}
+
 static inline bool is_session_valid(fastd_context *ctx, const protocol_session *session) {
 	return ctx->conf->method->session_is_valid(ctx, session->method_state);
 }
@@ -123,7 +124,7 @@ static inline bool is_session_valid(fastd_context *ctx, const protocol_session *
 static inline void check_session_refresh(fastd_context *ctx, fastd_peer *peer) {
 	protocol_session *session = &peer->protocol_state->session;
 
-	if (!session->refreshing && ctx->conf->method->session_want_refresh(ctx, session->method_state)) {
+	if (!session->refreshing && ctx->conf->method->session_is_initiator(ctx, session->method_state) && ctx->conf->method->session_want_refresh(ctx, session->method_state)) {
 		pr_debug(ctx, "refreshing session with %P", peer);
 		session->refreshing = true;
 		fastd_task_schedule_handshake(ctx, peer, 0);
@@ -173,89 +174,67 @@ static void init_peer_state(fastd_context *ctx, fastd_peer *peer) {
 	memset(peer->protocol_state, 0, sizeof(fastd_protocol_peer_state));
 }
 
-static inline void free_handshake(protocol_handshake *handshake) {
+static inline void free_handshake_key(handshake_key *handshake) {
 	if (handshake) {
-		memset(handshake, 0, sizeof(protocol_handshake));
+		memset(handshake, 0, sizeof(handshake_key));
 		free(handshake);
 	}
 }
 
-static void protocol_peer_config_purged(fastd_context *ctx, fastd_peer_config *peer_conf) {
-	fastd_peer *peer;
-	for (peer = ctx->peers; peer; peer = peer->next) {
-		if (!peer->protocol_state)
-			continue;
-
-		if (peer->protocol_state->initiating_handshake &&
-		    peer->protocol_state->initiating_handshake->peer_config == peer_conf) {
-			free_handshake(peer->protocol_state->initiating_handshake);
-			peer->protocol_state->initiating_handshake = NULL;
-		}
-
-		if (peer->protocol_state->accepting_handshake &&
-		    peer->protocol_state->accepting_handshake->peer_config == peer_conf) {
-			free_handshake(peer->protocol_state->accepting_handshake);
-			peer->protocol_state->accepting_handshake = NULL;
-		}
+static void maintenance(fastd_context *ctx) {
+	if (!ctx->protocol_state) {
+		ctx->protocol_state = malloc(sizeof(fastd_protocol_state));
+		memset(ctx->protocol_state, 0, sizeof(fastd_protocol_state));
 	}
-}
 
-static protocol_handshake* new_handshake(fastd_context *ctx, fastd_peer *peer, const fastd_peer_config *peer_config, bool initiate) {
-	protocol_handshake **handshake;
+	if (!is_handshake_key_preferred(ctx, &ctx->protocol_state->handshake_key)) {
+		pr_debug(ctx, "generating new handshake key");
 
-	if (initiate)
-		handshake = &peer->protocol_state->initiating_handshake;
-	else
-		handshake = &peer->protocol_state->accepting_handshake;
-
-	free_handshake(*handshake);
-
-	*handshake = malloc(sizeof(protocol_handshake));
+		ctx->protocol_state->prev_handshake_key = ctx->protocol_state->handshake_key;
 
-	(*handshake)->peer_config = peer_config;
+		fastd_random_bytes(ctx, ctx->protocol_state->handshake_key.secret_key.s, 32, false);
+		ecc_25519_secret_sanitize(&ctx->protocol_state->handshake_key.secret_key, &ctx->protocol_state->handshake_key.secret_key);
 
-	(*handshake)->state = HANDSHAKE_STATE_INIT;
+		ecc_25519_work work;
+		ecc_25519_scalarmult_base(&work, &ctx->protocol_state->handshake_key.secret_key);
+		ecc_25519_store(&ctx->protocol_state->handshake_key.public_key, &work);
 
-	fastd_random_bytes(ctx, (*handshake)->secret_key.s, 32, false);
-	ecc_25519_secret_sanitize(&(*handshake)->secret_key, &(*handshake)->secret_key);
+		ctx->protocol_state->handshake_key.preferred_till = ctx->now;
+		ctx->protocol_state->handshake_key.preferred_till.tv_sec += 15;
 
-	ecc_25519_work work;
-	ecc_25519_scalarmult_base(&work, &(*handshake)->secret_key);
-	ecc_25519_store(&(*handshake)->public_key, &work);
-
-	return *handshake;
+		ctx->protocol_state->handshake_key.valid_till = ctx->now;
+		ctx->protocol_state->handshake_key.valid_till.tv_sec += 30;
+	}
 }
 
-static void protocol_handshake_init(fastd_context *ctx, fastd_peer *peer) {
-	init_peer_state(ctx, peer);
-
-	fastd_buffer buffer = fastd_handshake_new_init(ctx, peer, 3*(4+PUBLICKEYBYTES) /* sender key, receipient key, handshake key */);
+static void protocol_handshake_init(fastd_context *ctx, const fastd_peer_address *address, const fastd_peer_config *peer_conf) {
+	maintenance(ctx);
 
-	protocol_handshake *handshake = new_handshake(ctx, peer, peer->config, true);
+	fastd_buffer buffer = fastd_handshake_new_init(ctx, 3*(4+PUBLICKEYBYTES) /* sender key, receipient key, handshake key */);
 
 	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_KEY, PUBLICKEYBYTES, ctx->conf->protocol_config->public_key.p);
 
-	if (handshake->peer_config)
-		fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES, handshake->peer_config->protocol_config->public_key.p);
+	if (peer_conf)
+		fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES, peer_conf->protocol_config->public_key.p);
 	else
-		pr_debug(ctx, "sending handshake to unknown peer %P", peer);
+		pr_debug(ctx, "sending handshake to unknown peer %I", address);
 
-	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES, handshake->public_key.p);
+	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES, ctx->protocol_state->handshake_key.public_key.p);
 
-	fastd_send_handshake(ctx, peer, buffer);
+	fastd_send_handshake(ctx, address, buffer);
 }
 
-static void respond_handshake(fastd_context *ctx, fastd_peer *peer, const fastd_handshake *handshake) {
-	pr_debug(ctx, "responding handshake with %P...", peer);
+static void respond_handshake(fastd_context *ctx, const fastd_peer_address *address, const fastd_peer_config *peer_conf, const handshake_key *handshake_key, const ecc_public_key_256 *peer_handshake_key, const fastd_handshake *handshake) {
+	pr_debug(ctx, "responding handshake with %I...", address);
 
 	uint8_t hashinput[5*PUBLICKEYBYTES];
 	uint8_t hashbuf[HASHBYTES];
 	uint8_t hmacbuf[HMACBYTES];
 
-	memcpy(hashinput, peer->protocol_state->accepting_handshake->public_key.p, PUBLICKEYBYTES);
-	memcpy(hashinput+PUBLICKEYBYTES, peer->protocol_state->accepting_handshake->peer_key.p, PUBLICKEYBYTES);
+	memcpy(hashinput, handshake_key->public_key.p, PUBLICKEYBYTES);
+	memcpy(hashinput+PUBLICKEYBYTES, peer_handshake_key->p, PUBLICKEYBYTES);
 	memcpy(hashinput+2*PUBLICKEYBYTES, ctx->conf->protocol_config->public_key.p, PUBLICKEYBYTES);
-	memcpy(hashinput+3*PUBLICKEYBYTES, peer->protocol_state->accepting_handshake->peer_config->protocol_config->public_key.p, PUBLICKEYBYTES);
+	memcpy(hashinput+3*PUBLICKEYBYTES, peer_conf->protocol_config->public_key.p, PUBLICKEYBYTES);
 
 	crypto_hash_sha256(hashbuf, hashinput, 4*PUBLICKEYBYTES);
 
@@ -268,11 +247,11 @@ static void respond_handshake(fastd_context *ctx, fastd_peer *peer, const fastd_
 	e.s[15] |= 0x80;
 
 	ecc_25519_secret_mult(&eb, &e, &ctx->conf->protocol_config->secret_key);
-	ecc_25519_secret_add(&s, &eb, &peer->protocol_state->accepting_handshake->secret_key);
+	ecc_25519_secret_add(&s, &eb, &handshake_key->secret_key);
 
 	ecc_25519_work work, workX;
-	ecc_25519_load(&work, &peer->protocol_state->accepting_handshake->peer_config->protocol_config->public_key);
-	ecc_25519_load(&workX, &peer->protocol_state->accepting_handshake->peer_key);
+	ecc_25519_load(&work, &peer_conf->protocol_config->public_key);
+	ecc_25519_load(&workX, peer_handshake_key);
 
 	ecc_25519_scalarmult(&work, &d, &work);
 	ecc_25519_add(&work, &workX, &work);
@@ -281,36 +260,46 @@ static void respond_handshake(fastd_context *ctx, fastd_peer *peer, const fastd_
 	if (ecc_25519_is_identity(&work))
 		return;
 
-	ecc_25519_store(&peer->protocol_state->accepting_handshake->sigma, &work);
+	ecc_public_key_256 sigma;
+	ecc_25519_store(&sigma, &work);
 
-	memcpy(hashinput+4*PUBLICKEYBYTES, peer->protocol_state->accepting_handshake->sigma.p, PUBLICKEYBYTES);
-	crypto_hash_sha256(peer->protocol_state->accepting_handshake->shared_handshake_key, hashinput, 5*PUBLICKEYBYTES);
+	uint8_t shared_handshake_key[HASHBYTES];
+	memcpy(hashinput+4*PUBLICKEYBYTES, sigma.p, PUBLICKEYBYTES);
+	crypto_hash_sha256(shared_handshake_key, hashinput, 5*PUBLICKEYBYTES);
 
 	memcpy(hashinput, ctx->conf->protocol_config->public_key.p, PUBLICKEYBYTES);
-	memcpy(hashinput+PUBLICKEYBYTES, peer->protocol_state->accepting_handshake->public_key.p, PUBLICKEYBYTES);
+	memcpy(hashinput+PUBLICKEYBYTES, handshake_key->public_key.p, PUBLICKEYBYTES);
 
-	crypto_auth_hmacsha256(hmacbuf, hashinput, 2*PUBLICKEYBYTES, peer->protocol_state->accepting_handshake->shared_handshake_key);
+	crypto_auth_hmacsha256(hmacbuf, hashinput, 2*PUBLICKEYBYTES, shared_handshake_key);
 
-	fastd_buffer buffer = fastd_handshake_new_reply(ctx, peer, handshake, 4*(4+PUBLICKEYBYTES) + 4+HMACBYTES);
+	fastd_buffer buffer = fastd_handshake_new_reply(ctx, handshake, 4*(4+PUBLICKEYBYTES) + 4+HMACBYTES);
 
 	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_KEY, PUBLICKEYBYTES, ctx->conf->protocol_config->public_key.p);
-	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES, peer->protocol_state->accepting_handshake->peer_config->protocol_config->public_key.p);
-	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES, peer->protocol_state->accepting_handshake->public_key.p);
-	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_HANDSHAKE_KEY, PUBLICKEYBYTES, peer->protocol_state->accepting_handshake->peer_key.p);
+	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES, peer_conf->protocol_config->public_key.p);
+	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES, handshake_key->public_key.p);
+	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_HANDSHAKE_KEY, PUBLICKEYBYTES, peer_handshake_key->p);
 	fastd_handshake_add(ctx, &buffer, RECORD_T, HMACBYTES, hmacbuf);
 
-	fastd_send_handshake(ctx, peer, buffer);
-
-	peer->protocol_state->accepting_handshake->state = HANDSHAKE_STATE_RESPONSE;
+	fastd_send_handshake(ctx, address, buffer);
 }
 
-static void establish(fastd_context *ctx, fastd_peer *peer, const fastd_peer_config *peer_config, bool initiator,
+static void establish(fastd_context *ctx, const fastd_peer_config *peer_conf, const fastd_peer_address *address, bool initiator,
 		      const ecc_public_key_256 *A, const ecc_public_key_256 *B, const ecc_public_key_256 *X,
 		      const ecc_public_key_256 *Y, const ecc_public_key_256 *sigma) {
 	uint8_t hashinput[5*PUBLICKEYBYTES];
 	uint8_t hash[HASHBYTES];
 
-	pr_verbose(ctx, "New session with %P established.", peer);
+	fastd_peer *peer;
+	for (peer = ctx->peers; peer; peer = peer->next) {
+		if (peer->config == peer_conf)
+			break;
+	}
+	if (!peer)
+		exit_bug(ctx, "no peer for config found");
+
+	pr_verbose(ctx, "%I authorized as %P", address, peer);
+
+	init_peer_state(ctx, peer);
 
 	if (is_session_valid(ctx, &peer->protocol_state->session) && !is_session_valid(ctx, &peer->protocol_state->old_session)) {
 		ctx->conf->method->session_free(ctx, peer->protocol_state->old_session.method_state);
@@ -331,43 +320,34 @@ static void establish(fastd_context *ctx, fastd_peer *peer, const fastd_peer_con
 	peer->protocol_state->session.refreshing = false;
 	peer->protocol_state->session.method_state = ctx->conf->method->session_init(ctx, hash, HASHBYTES, initiator);
 
-	free_handshake(peer->protocol_state->initiating_handshake);
-	peer->protocol_state->initiating_handshake = NULL;
-
-	free_handshake(peer->protocol_state->accepting_handshake);
-	peer->protocol_state->accepting_handshake = NULL;
-
 	fastd_peer_seen(ctx, peer);
 
-	if (peer_config != peer->config) {
-		fastd_peer *perm_peer;
-		for (perm_peer = ctx->peers; perm_peer; perm_peer = perm_peer->next) {
-			if (perm_peer->config == peer_config) {
-				peer = fastd_peer_set_established_merge(ctx, perm_peer, peer);
-				break;
-			}
-		}
-	}
-	else {
-		fastd_peer_set_established(ctx, peer);
+	if (!fastd_peer_claim_address(ctx, peer, address)) {
+		pr_warn(ctx, "can't set address %I which is used by a fixed peer", ctx->resolve_returns->addr);
+		fastd_peer_reset(ctx, peer);
+		return;
 	}
 
+	fastd_peer_set_established(ctx, peer);
+
+	pr_verbose(ctx, "new session with %P established.", peer);
+
 	fastd_task_schedule_keepalive(ctx, peer, ctx->conf->keepalive_interval*1000);
 
 	if (!initiator)
 		protocol_send(ctx, peer, fastd_buffer_alloc(0, ctx->conf->method->min_encrypt_head_space(ctx), 0));
 }
 
-static void finish_handshake(fastd_context *ctx, fastd_peer *peer, const fastd_handshake *handshake) {
-	pr_debug(ctx, "finishing handshake with %P...", peer);
+static void finish_handshake(fastd_context *ctx, const fastd_peer_address *address, const fastd_peer_config *peer_conf, const handshake_key *handshake_key, const ecc_public_key_256 *peer_handshake_key, const fastd_handshake *handshake) {
+	pr_debug(ctx, "finishing handshake with %I...", address);
 
 	uint8_t hashinput[5*PUBLICKEYBYTES];
 	uint8_t hashbuf[HASHBYTES];
 	uint8_t hmacbuf[HMACBYTES];
 
-	memcpy(hashinput, peer->protocol_state->initiating_handshake->peer_key.p, PUBLICKEYBYTES);
-	memcpy(hashinput+PUBLICKEYBYTES, peer->protocol_state->initiating_handshake->public_key.p, PUBLICKEYBYTES);
-	memcpy(hashinput+2*PUBLICKEYBYTES, peer->protocol_state->initiating_handshake->peer_config->protocol_config->public_key.p, PUBLICKEYBYTES);
+	memcpy(hashinput, peer_handshake_key->p, PUBLICKEYBYTES);
+	memcpy(hashinput+PUBLICKEYBYTES, handshake_key->public_key.p, PUBLICKEYBYTES);
+	memcpy(hashinput+2*PUBLICKEYBYTES, peer_conf->protocol_config->public_key.p, PUBLICKEYBYTES);
 	memcpy(hashinput+3*PUBLICKEYBYTES, ctx->conf->protocol_config->public_key.p, PUBLICKEYBYTES);
 
 	crypto_hash_sha256(hashbuf, hashinput, 4*PUBLICKEYBYTES);
@@ -381,11 +361,11 @@ static void finish_handshake(fastd_context *ctx, fastd_peer *peer, const fastd_h
 	e.s[15] |= 0x80;
 
 	ecc_25519_secret_mult(&da, &d, &ctx->conf->protocol_config->secret_key);
-	ecc_25519_secret_add(&s, &da, &peer->protocol_state->initiating_handshake->secret_key);
+	ecc_25519_secret_add(&s, &da, &handshake_key->secret_key);
 
 	ecc_25519_work work, workY;
-	ecc_25519_load(&work, &peer->protocol_state->initiating_handshake->peer_config->protocol_config->public_key);
-	ecc_25519_load(&workY, &peer->protocol_state->initiating_handshake->peer_key);
+	ecc_25519_load(&work, &peer_conf->protocol_config->public_key);
+	ecc_25519_load(&workY, peer_handshake_key);
 
 	ecc_25519_scalarmult(&work, &e, &work);
 	ecc_25519_add(&work, &workY, &work);
@@ -394,72 +374,103 @@ static void finish_handshake(fastd_context *ctx, fastd_peer *peer, const fastd_h
 	if (ecc_25519_is_identity(&work))
 		return;
 
-	ecc_25519_store(&peer->protocol_state->initiating_handshake->sigma, &work);
+	ecc_public_key_256 sigma;
+	ecc_25519_store(&sigma, &work);
 
-	memcpy(hashinput+4*PUBLICKEYBYTES, peer->protocol_state->initiating_handshake->sigma.p, PUBLICKEYBYTES);
-	crypto_hash_sha256(peer->protocol_state->initiating_handshake->shared_handshake_key, hashinput, 5*PUBLICKEYBYTES);
+	uint8_t shared_handshake_key[HASHBYTES];
+	memcpy(hashinput+4*PUBLICKEYBYTES, sigma.p, PUBLICKEYBYTES);
+	crypto_hash_sha256(shared_handshake_key, hashinput, 5*PUBLICKEYBYTES);
 
-	memcpy(hashinput, peer->protocol_state->initiating_handshake->peer_config->protocol_config->public_key.p, PUBLICKEYBYTES);
-	memcpy(hashinput+PUBLICKEYBYTES, peer->protocol_state->initiating_handshake->peer_key.p, PUBLICKEYBYTES);
+	memcpy(hashinput, peer_conf->protocol_config->public_key.p, PUBLICKEYBYTES);
+	memcpy(hashinput+PUBLICKEYBYTES, peer_handshake_key->p, PUBLICKEYBYTES);
 
-	if(crypto_auth_hmacsha256_verify(handshake->records[RECORD_T].data, hashinput, 2*PUBLICKEYBYTES, peer->protocol_state->initiating_handshake->shared_handshake_key) != 0) {
-		pr_warn(ctx, "received invalid protocol handshake response from %P", peer);
+	if(crypto_auth_hmacsha256_verify(handshake->records[RECORD_T].data, hashinput, 2*PUBLICKEYBYTES, shared_handshake_key) != 0) {
+		pr_warn(ctx, "received invalid protocol handshake response from %I", address);
 		return;
 	}
 
 	memcpy(hashinput, ctx->conf->protocol_config->public_key.p, PUBLICKEYBYTES);
-	memcpy(hashinput+PUBLICKEYBYTES, peer->protocol_state->initiating_handshake->public_key.p, PUBLICKEYBYTES);
-	crypto_auth_hmacsha256(hmacbuf, hashinput, 2*PUBLICKEYBYTES, peer->protocol_state->initiating_handshake->shared_handshake_key);
+	memcpy(hashinput+PUBLICKEYBYTES, handshake_key->public_key.p, PUBLICKEYBYTES);
+	crypto_auth_hmacsha256(hmacbuf, hashinput, 2*PUBLICKEYBYTES, shared_handshake_key);
 
-	fastd_buffer buffer = fastd_handshake_new_reply(ctx, peer, handshake, 4*(4+PUBLICKEYBYTES) + 4+HMACBYTES);
+	fastd_buffer buffer = fastd_handshake_new_reply(ctx, handshake, 4*(4+PUBLICKEYBYTES) + 4+HMACBYTES);
 
 	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_KEY, PUBLICKEYBYTES, ctx->conf->protocol_config->public_key.p);
-	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES, peer->protocol_state->initiating_handshake->peer_config->protocol_config->public_key.p);
-	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES, peer->protocol_state->initiating_handshake->public_key.p);
-	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_HANDSHAKE_KEY, PUBLICKEYBYTES, peer->protocol_state->initiating_handshake->peer_key.p);
+	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES, peer_conf->protocol_config->public_key.p);
+	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES, handshake_key->public_key.p);
+	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_HANDSHAKE_KEY, PUBLICKEYBYTES, peer_handshake_key->p);
 	fastd_handshake_add(ctx, &buffer, RECORD_T, HMACBYTES, hmacbuf);
 
-	fastd_send_handshake(ctx, peer, buffer);
+	fastd_send_handshake(ctx, address, buffer);
 
-	establish(ctx, peer, peer->protocol_state->initiating_handshake->peer_config, true,
-		  &peer->protocol_state->initiating_handshake->public_key,
-		  &peer->protocol_state->initiating_handshake->peer_key,
-		  &ctx->conf->protocol_config->public_key,
-		  &peer->protocol_state->initiating_handshake->peer_config->protocol_config->public_key,
-		  &peer->protocol_state->initiating_handshake->sigma);
+	establish(ctx, peer_conf, address, true, &handshake_key->public_key, peer_handshake_key, &ctx->conf->protocol_config->public_key,
+		  &peer_conf->protocol_config->public_key, &sigma);
 }
 
-static void handle_finish_handshake(fastd_context *ctx, fastd_peer *peer, const fastd_handshake *handshake) {
-	pr_debug(ctx, "handling handshake finish with %P...", peer);
+static void handle_finish_handshake(fastd_context *ctx, const fastd_peer_address *address, const fastd_peer_config *peer_conf, const handshake_key *handshake_key, const ecc_public_key_256 *peer_handshake_key, const fastd_handshake *handshake) {
+	pr_debug(ctx, "handling handshake finish with %I...", address);
+
+	uint8_t hashinput[5*PUBLICKEYBYTES];
+	uint8_t hashbuf[HASHBYTES];
+
+	memcpy(hashinput, handshake_key->public_key.p, PUBLICKEYBYTES);
+	memcpy(hashinput+PUBLICKEYBYTES, peer_handshake_key->p, PUBLICKEYBYTES);
+	memcpy(hashinput+2*PUBLICKEYBYTES, ctx->conf->protocol_config->public_key.p, PUBLICKEYBYTES);
+	memcpy(hashinput+3*PUBLICKEYBYTES, peer_conf->protocol_config->public_key.p, PUBLICKEYBYTES);
+
+	crypto_hash_sha256(hashbuf, hashinput, 4*PUBLICKEYBYTES);
+
+	ecc_secret_key_256 d = {{0}}, e = {{0}}, eb, s;
+
+	memcpy(d.s, hashbuf, HASHBYTES/2);
+	memcpy(e.s, hashbuf+HASHBYTES/2, HASHBYTES/2);
+
+	d.s[15] |= 0x80;
+	e.s[15] |= 0x80;
 
-	uint8_t hashinput[2*PUBLICKEYBYTES];
+	ecc_25519_secret_mult(&eb, &e, &ctx->conf->protocol_config->secret_key);
+	ecc_25519_secret_add(&s, &eb, &handshake_key->secret_key);
 
-	memcpy(hashinput, peer->protocol_state->accepting_handshake->peer_config->protocol_config->public_key.p, PUBLICKEYBYTES);
-	memcpy(hashinput+PUBLICKEYBYTES, peer->protocol_state->accepting_handshake->peer_key.p, PUBLICKEYBYTES);
+	ecc_25519_work work, workX;
+	ecc_25519_load(&work, &peer_conf->protocol_config->public_key);
+	ecc_25519_load(&workX, peer_handshake_key);
 
-	if(crypto_auth_hmacsha256_verify(handshake->records[RECORD_T].data, hashinput, 2*PUBLICKEYBYTES, peer->protocol_state->accepting_handshake->shared_handshake_key) != 0) {
-		pr_warn(ctx, "received invalid protocol handshake finish from %P", peer);
+	ecc_25519_scalarmult(&work, &d, &work);
+	ecc_25519_add(&work, &workX, &work);
+	ecc_25519_scalarmult(&work, &s, &work);
+
+	if (ecc_25519_is_identity(&work))
+		return;
+
+	ecc_public_key_256 sigma;
+	ecc_25519_store(&sigma, &work);
+
+	uint8_t shared_handshake_key[HASHBYTES];
+	memcpy(hashinput+4*PUBLICKEYBYTES, sigma.p, PUBLICKEYBYTES);
+	crypto_hash_sha256(shared_handshake_key, hashinput, 5*PUBLICKEYBYTES);
+
+	memcpy(hashinput, peer_conf->protocol_config->public_key.p, PUBLICKEYBYTES);
+	memcpy(hashinput+PUBLICKEYBYTES, peer_handshake_key->p, PUBLICKEYBYTES);
+
+	if(crypto_auth_hmacsha256_verify(handshake->records[RECORD_T].data, hashinput, 2*PUBLICKEYBYTES, shared_handshake_key) != 0) {
+		pr_warn(ctx, "received invalid protocol handshake finish from %I", address);
 		return;
 	}
 
-	establish(ctx, peer, peer->protocol_state->accepting_handshake->peer_config, false,
-		  &peer->protocol_state->accepting_handshake->peer_key,
-		  &peer->protocol_state->accepting_handshake->public_key,
-		  &peer->protocol_state->accepting_handshake->peer_config->protocol_config->public_key,
-		  &ctx->conf->protocol_config->public_key,
-		  &peer->protocol_state->accepting_handshake->sigma);
+	establish(ctx, peer_conf, address, false, peer_handshake_key, &handshake_key->public_key, &peer_conf->protocol_config->public_key,
+		  &ctx->conf->protocol_config->public_key, &sigma);
 }
 
-static inline const fastd_peer_config* match_sender_key(fastd_context *ctx, fastd_peer *peer, const unsigned char key[32]) {
-	if (peer->config) {
-		if (memcmp(peer->config->protocol_config->public_key.p, key, PUBLICKEYBYTES) == 0)
-			return peer->config;
+static const fastd_peer_config* match_sender_key(fastd_context *ctx, const fastd_peer_address *address, const fastd_peer_config *peer_conf, const unsigned char key[32]) {
+	if (peer_conf) {
+		if (memcmp(peer_conf->protocol_config->public_key.p, key, PUBLICKEYBYTES) == 0)
+			return peer_conf;
 	}
 
-	if (fastd_peer_is_temporary(peer) || fastd_peer_is_floating(peer) || fastd_peer_is_dynamic(peer)) {
+	if (!peer_conf || fastd_peer_config_is_floating(peer_conf) || fastd_peer_config_is_dynamic(peer_conf)) {
 		fastd_peer_config *config;
 		for (config = ctx->conf->peers; config; config = config->next) {
-			if (!fastd_peer_config_is_floating(config) && !fastd_peer_config_matches_dynamic(config, &peer->address))
+			if (!fastd_peer_config_is_floating(config) && !fastd_peer_config_matches_dynamic(config, address))
 				continue;
 
 			if (memcmp(config->protocol_config->public_key.p, key, PUBLICKEYBYTES) == 0) {
@@ -477,129 +488,89 @@ static inline const fastd_peer_config* match_sender_key(fastd_context *ctx, fast
 	return NULL;
 }
 
-static void kill_handshakes(fastd_context *ctx, fastd_peer *peer) {
-	pr_debug(ctx, "there is a handshake conflict, retrying in a moment...");
-
-	free_handshake(peer->protocol_state->initiating_handshake);
-	peer->protocol_state->initiating_handshake = NULL;
-
-	free_handshake(peer->protocol_state->accepting_handshake);
-	peer->protocol_state->accepting_handshake = NULL;
-}
-
 static inline bool has_field(const fastd_handshake *handshake, uint8_t type, size_t length) {
 	return (handshake->records[type].length == length);
 }
 
-static void protocol_handshake_handle(fastd_context *ctx, fastd_peer *peer, const fastd_handshake *handshake) {
-	init_peer_state(ctx, peer);
+static void protocol_handshake_handle(fastd_context *ctx, const fastd_peer_address *address, const fastd_peer_config *peer_conf, const fastd_handshake *handshake) {
+	handshake_key *handshake_key;
+
+	maintenance(ctx);
 
 	if (!has_field(handshake, RECORD_SENDER_KEY, PUBLICKEYBYTES)) {
-		pr_debug(ctx, "received handshake without sender key from %P", peer);
+		pr_debug(ctx, "received handshake without sender key from %I", address);
 		return;
 	}
 
-	const fastd_peer_config *peer_config = match_sender_key(ctx, peer, handshake->records[RECORD_SENDER_KEY].data);
-	if (!peer_config) {
-		pr_debug(ctx, "ignoring handshake from %P (unknown key or unresolved host)", peer);
+	peer_conf = match_sender_key(ctx, address, peer_conf, handshake->records[RECORD_SENDER_KEY].data);
+	if (!peer_conf) {
+		pr_debug(ctx, "ignoring handshake from %I (unknown key or unresolved host)", address);
 		return;
 	}
 
 	if (handshake->type > 1 && !has_field(handshake, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES)) {
-		pr_debug(ctx, "received handshake reply without receipient key from %P", peer);
+		pr_debug(ctx, "received handshake reply without receipient key from %I", address);
 		return;
 	}
 	else if(has_field(handshake, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES)) {
 		if (memcmp(ctx->conf->protocol_config->public_key.p, handshake->records[RECORD_RECEIPIENT_KEY].data, PUBLICKEYBYTES) != 0) {
-			pr_debug(ctx, "received protocol handshake with wrong receipient key from %P", peer);
+			pr_debug(ctx, "received protocol handshake with wrong receipient key from %I", address);
 			return;
 		}
 	}
 
 	if (!has_field(handshake, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES)) {
-		pr_debug(ctx, "received handshake without sender handshake key from %P", peer);
+		pr_debug(ctx, "received handshake without sender handshake key from %I", address);
 		return;
 	}
 
 	if (handshake->type > 1 && !has_field(handshake, RECORD_RECEIPIENT_HANDSHAKE_KEY, PUBLICKEYBYTES)) {
-		pr_debug(ctx, "received handshake reply without receipient handshake key from %P", peer);
+		pr_debug(ctx, "received handshake reply without receipient handshake key from %I", address);
 		return;
 	}
 
 	if (handshake->type > 1 && !has_field(handshake, RECORD_T, HMACBYTES)) {
-		pr_debug(ctx, "received handshake reply without HMAC from %P", peer);
+		pr_debug(ctx, "received handshake reply without HMAC from %I", address);
 		return;
 	}
 
 	switch(handshake->type) {
 	case 1:
-		new_handshake(ctx, peer, peer_config, false);
-		memcpy(peer->protocol_state->accepting_handshake->peer_key.p, handshake->records[RECORD_SENDER_HANDSHAKE_KEY].data, PUBLICKEYBYTES);
-		respond_handshake(ctx, peer, handshake);
+		respond_handshake(ctx, address, peer_conf, &ctx->protocol_state->handshake_key, handshake->records[RECORD_SENDER_HANDSHAKE_KEY].data, handshake);
 		break;
 
 	case 2:
-		if (!peer->protocol_state->initiating_handshake || peer->protocol_state->initiating_handshake->state != HANDSHAKE_STATE_INIT) {
-			pr_debug(ctx, "received unexpected handshake response from %P", peer);
-			return;
-		}
-
-		if (peer->protocol_state->initiating_handshake->peer_config != peer_config) {
-			if (peer->protocol_state->initiating_handshake->peer_config) {
-				pr_debug(ctx, "received handshake response with wrong sender key from %P", peer);
-				return;
-			}
-			else {
-				peer->protocol_state->initiating_handshake->peer_config = peer_config;
-			}
+		if (is_handshake_key_valid(ctx, &ctx->protocol_state->handshake_key) && memcmp(ctx->protocol_state->handshake_key.public_key.p, handshake->records[RECORD_RECEIPIENT_HANDSHAKE_KEY].data, PUBLICKEYBYTES) == 0) {
+			handshake_key = &ctx->protocol_state->handshake_key;
 		}
-
-		if (memcmp(peer->protocol_state->initiating_handshake->public_key.p, handshake->records[RECORD_RECEIPIENT_HANDSHAKE_KEY].data, PUBLICKEYBYTES) != 0) {
-			pr_debug(ctx, "received handshake response with unexpected receipient handshake key from %P", peer);
-			return;
+		else if (is_handshake_key_valid(ctx, &ctx->protocol_state->prev_handshake_key) && memcmp(ctx->protocol_state->prev_handshake_key.public_key.p, handshake->records[RECORD_RECEIPIENT_HANDSHAKE_KEY].data, PUBLICKEYBYTES) == 0) {
+			handshake_key = &ctx->protocol_state->prev_handshake_key;
 		}
-
-		pr_debug(ctx, "received handshake response from %P", peer);
-
-		if (peer->protocol_state->accepting_handshake) {
-			kill_handshakes(ctx, peer);
+		else {
+			pr_debug(ctx, "received handshake response with unexpected receipient handshake key from %I", address);
 			return;
 		}
 
-		memcpy(peer->protocol_state->initiating_handshake->peer_key.p, handshake->records[RECORD_SENDER_HANDSHAKE_KEY].data, PUBLICKEYBYTES);
+		pr_debug(ctx, "received handshake response from %I", address);
 
-		finish_handshake(ctx, peer, handshake);
+		finish_handshake(ctx, address, peer_conf, handshake_key, handshake->records[RECORD_SENDER_HANDSHAKE_KEY].data, handshake);
 		break;
 
 	case 3:
-		if (!peer->protocol_state->accepting_handshake || peer->protocol_state->accepting_handshake->state != HANDSHAKE_STATE_RESPONSE) {
-			pr_debug(ctx, "received unexpected protocol handshake finish from %P", peer);
-			return;
+		if (is_handshake_key_valid(ctx, &ctx->protocol_state->handshake_key) && memcmp(ctx->protocol_state->handshake_key.public_key.p, handshake->records[RECORD_RECEIPIENT_HANDSHAKE_KEY].data, PUBLICKEYBYTES) == 0) {
+			handshake_key = &ctx->protocol_state->handshake_key;
 		}
-
-		if (peer->protocol_state->accepting_handshake->peer_config != peer_config) {
-			pr_debug(ctx, "received protocol handshake finish with wrong sender key from %P", peer);
-			return;
+		else if (is_handshake_key_valid(ctx, &ctx->protocol_state->prev_handshake_key) && memcmp(ctx->protocol_state->prev_handshake_key.public_key.p, handshake->records[RECORD_RECEIPIENT_HANDSHAKE_KEY].data, PUBLICKEYBYTES) == 0) {
+			handshake_key = &ctx->protocol_state->prev_handshake_key;
 		}
-
-		if (memcmp(peer->protocol_state->accepting_handshake->public_key.p, handshake->records[RECORD_RECEIPIENT_HANDSHAKE_KEY].data, PUBLICKEYBYTES) != 0) {
-			pr_debug(ctx, "received handshake response with unexpected receipient handshake key from %P", peer);
+		else {
+			pr_debug(ctx, "received handshake response with unexpected receipient handshake key from %I", address);
 			return;
 		}
 
-		if (memcmp(peer->protocol_state->accepting_handshake->peer_key.p, handshake->records[RECORD_SENDER_HANDSHAKE_KEY].data, PUBLICKEYBYTES) != 0) {
-			pr_debug(ctx, "received handshake response with unexpected sender handshake key from %P", peer);
-			return;
-		}
+		pr_debug(ctx, "received handshake finish from %I", address);
 
-		pr_debug(ctx, "received handshake finish from %P", peer);
-
-		if (peer->protocol_state->initiating_handshake && peer->protocol_state->initiating_handshake->state != HANDSHAKE_STATE_INIT) {
-			kill_handshakes(ctx, peer);
-			return;
-		}
-
-		handle_finish_handshake(ctx, peer, handshake);
+		handle_finish_handshake(ctx, address, peer_conf, handshake_key, handshake->records[RECORD_SENDER_HANDSHAKE_KEY].data, handshake);
 		break;
 
 	default:
@@ -609,12 +580,8 @@ static void protocol_handshake_handle(fastd_context *ctx, fastd_peer *peer, cons
 
 static void protocol_handle_recv(fastd_context *ctx, fastd_peer *peer, fastd_buffer buffer) {
 	if (!fastd_peer_is_established(peer)) {
-		pr_debug(ctx, "received unexpected packet from %P", peer);
-
-		if (fastd_peer_is_temporary(peer)) {
-			pr_debug(ctx, "sending handshake to temporary peer %P", peer);
-			fastd_task_schedule_handshake(ctx, peer, 0);
-		}
+		pr_debug(ctx, "received unexpected packet from %P, scheduling handshake", peer);
+		fastd_task_schedule_handshake(ctx, peer, 0);
 
 		goto fail;
 	}
@@ -690,7 +657,7 @@ static void protocol_send(fastd_context *ctx, fastd_peer *peer, fastd_buffer buf
 	if (!ctx->conf->method->encrypt(ctx, session->method_state, &send_buffer, buffer))
 		goto fail;
 	
-	fastd_send(ctx, peer, send_buffer);
+	fastd_send(ctx, &peer->address, send_buffer);
 
 	fastd_task_delete_peer_keepalives(ctx, peer);
 	fastd_task_schedule_keepalive(ctx, peer, ctx->conf->keepalive_interval*1000);
@@ -702,9 +669,6 @@ static void protocol_send(fastd_context *ctx, fastd_peer *peer, fastd_buffer buf
 
 static void protocol_free_peer_state(fastd_context *ctx, fastd_peer *peer) {
 	if (peer->protocol_state) {
-		free_handshake(peer->protocol_state->initiating_handshake);
-		free_handshake(peer->protocol_state->accepting_handshake);
-
 		ctx->conf->method->session_free(ctx, peer->protocol_state->old_session.method_state);
 		ctx->conf->method->session_free(ctx, peer->protocol_state->session.method_state);
 
@@ -712,7 +676,6 @@ static void protocol_free_peer_state(fastd_context *ctx, fastd_peer *peer) {
 	}
 }
 
-
 static void hexdump(const char *desc, unsigned char d[32]) {
 	printf("%s", desc);
 
@@ -746,7 +709,6 @@ const fastd_protocol fastd_protocol_ec25519_fhmqvc = {
 
 	.init = protocol_init,
 	.peer_configure = protocol_peer_configure,
-	.peer_config_purged = protocol_peer_config_purged,
 
 	.handshake_init = protocol_handshake_init,
 	.handshake_handle = protocol_handshake_handle,