Separate ec25519-fhmqvc into multiple source files

1 files changed, 618 insertions, 0 deletions

diff --git a/src/protocols/ec25519_fhmqvc/handshake.c b/src/protocols/ec25519_fhmqvc/handshake.c
new file mode 100644
index 0000000..80be735
--- /dev/null
+++ b/src/protocols/ec25519_fhmqvc/handshake.c
@@ -0,0 +1,618 @@
+/*
+  Copyright (c) 2012-2013, Matthias Schiffer <mschiffer@universe-factory.net>
+  All rights reserved.
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions are met:
+
+    1. Redistributions of source code must retain the above copyright notice,
+       this list of conditions and the following disclaimer.
+    2. Redistributions in binary form must reproduce the above copyright notice,
+       this list of conditions and the following disclaimer in the documentation
+       and/or other materials provided with the distribution.
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+
+#include "ec25519_fhmqvc.h"
+#include "../../handshake.h"
+
+
+#define PUBLICKEYBYTES 32
+#define SECRETKEYBYTES 32
+#define HASHBYTES FASTD_SHA256_HASH_BYTES
+
+
+#if HASHBYTES != FASTD_HMACSHA256_KEY_BYTES
+#error bug: HASHBYTES != FASTD_HMACSHA256_KEY_BYTES
+#endif
+
+#if HASHBYTES != SECRETKEYBYTES
+#error bug: HASHBYTES != SECRETKEYBYTES
+#endif
+
+
+#define RECORD_SENDER_KEY RECORD_PROTOCOL1
+#define RECORD_RECEIPIENT_KEY RECORD_PROTOCOL2
+#define RECORD_SENDER_HANDSHAKE_KEY RECORD_PROTOCOL3
+#define RECORD_RECEIPIENT_HANDSHAKE_KEY RECORD_PROTOCOL4
+#define RECORD_T RECORD_PROTOCOL5
+
+
+static bool backoff(fastd_context_t *ctx, const fastd_peer_t *peer) {
+	return (peer->protocol_state && is_session_valid(ctx, &peer->protocol_state->session)
+		&& timespec_diff(&ctx->now, &peer->protocol_state->session.established) < 15000);
+}
+
+void fastd_protocol_ec25519_fhmqvc_handshake_init(fastd_context_t *ctx, const 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(ctx);
+
+	fastd_buffer_t 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->key.public.p);
+
+	if (peer)
+		fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES, peer->protocol_config->public_key.p);
+	else
+		pr_debug(ctx, "sending handshake to unknown peer %I", remote_addr);
+
+	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES, ctx->protocol_state->handshake_key.key1.public.p);
+
+	fastd_send_handshake(ctx, sock, local_addr, remote_addr, peer, buffer);
+}
+
+
+static bool update_shared_handshake_key(fastd_context_t *ctx, const fastd_peer_t *peer, const handshake_key_t *handshake_key, const aligned_int256_t *peer_handshake_key) {
+	if (peer->protocol_state->last_handshake_serial == handshake_key->serial) {
+		if (memcmp(&peer->protocol_state->peer_handshake_key, peer_handshake_key, PUBLICKEYBYTES) == 0)
+			return true;
+	}
+
+	fastd_sha256_t hashbuf;
+	fastd_sha256_blocks(&hashbuf,
+			    handshake_key->key2.public.p,
+			    peer_handshake_key->p,
+			    ctx->conf->protocol_config->key.public.p,
+			    peer->protocol_config->public_key.p,
+			    NULL);
+
+	ecc_int256_t d = {{0}}, e = {{0}}, eb, s;
+
+	memcpy(d.p, hashbuf.b, HASHBYTES/2);
+	memcpy(e.p, hashbuf.b+HASHBYTES/2, HASHBYTES/2);
+
+	d.p[15] |= 0x80;
+	e.p[15] |= 0x80;
+
+	ecc_25519_gf_mult(&eb, &e, &ctx->conf->protocol_config->key.secret);
+	ecc_25519_gf_add(&s, &eb, &handshake_key->key2.secret);
+
+	ecc_25519_work_t work, workX;
+	if (!ecc_25519_load_packed(&workX, peer_handshake_key))
+		return false;
+
+	ecc_25519_scalarmult(&work, &ecc_25519_gf_order, &workX);
+	if (!ecc_25519_is_identity(&work))
+		return false;
+
+	if (!ecc_25519_load_packed(&work, &peer->protocol_config->public_key))
+		return false;
+
+	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 false;
+
+	ecc_25519_store_packed(&peer->protocol_state->sigma, &work);
+
+	fastd_sha256_blocks(&peer->protocol_state->shared_handshake_key,
+			    handshake_key->key2.public.p,
+			    peer_handshake_key->p,
+			    ctx->conf->protocol_config->key.public.p,
+			    peer->protocol_config->public_key.p,
+			    peer->protocol_state->sigma.p,
+			    NULL);
+
+	peer->protocol_state->last_handshake_serial = handshake_key->serial;
+	peer->protocol_state->peer_handshake_key = *peer_handshake_key;
+
+	return true;
+}
+
+static void clear_shared_handshake_key(fastd_context_t *ctx UNUSED, const fastd_peer_t *peer) {
+	memset(&peer->protocol_state->sigma, 0, sizeof(peer->protocol_state->sigma));
+	memset(&peer->protocol_state->shared_handshake_key, 0, sizeof(peer->protocol_state->shared_handshake_key));
+
+	peer->protocol_state->last_handshake_serial = 0;
+	memset(&peer->protocol_state->peer_handshake_key, 0, sizeof(peer->protocol_state->peer_handshake_key));
+}
+
+static void respond_handshake(fastd_context_t *ctx, const fastd_socket_t *sock, const fastd_peer_address_t *local_addr, const fastd_peer_address_t *remote_addr, fastd_peer_t *peer,
+			      const handshake_key_t *handshake_key, const aligned_int256_t *peer_handshake_key, const fastd_handshake_t *handshake, const char *method) {
+	pr_debug(ctx, "responding handshake with %P[%I]...", peer, remote_addr);
+
+	if (!update_shared_handshake_key(ctx, peer, handshake_key, peer_handshake_key))
+		return;
+
+	fastd_buffer_t buffer = fastd_handshake_new_reply(ctx, handshake, method, true, 4*(4+PUBLICKEYBYTES) + 2*(4+HASHBYTES));
+
+	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_KEY, PUBLICKEYBYTES, ctx->conf->protocol_config->key.public.p);
+	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES, peer->protocol_config->public_key.p);
+	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES, handshake_key->key2.public.p);
+	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_HANDSHAKE_KEY, PUBLICKEYBYTES, peer_handshake_key->p);
+
+	fastd_sha256_t hmacbuf;
+
+	if (!ctx->conf->secure_handshakes) {
+		fastd_hmacsha256_blocks(&hmacbuf, peer->protocol_state->shared_handshake_key.w, ctx->conf->protocol_config->key.public.p, handshake_key->key2.public.p, NULL);
+		fastd_handshake_add(ctx, &buffer, RECORD_T, HASHBYTES, hmacbuf.b);
+	}
+
+	memset(&hmacbuf, 0, sizeof(hmacbuf));
+	fastd_handshake_add(ctx, &buffer, RECORD_TLV_MAC, HASHBYTES, hmacbuf.b);
+	fastd_hmacsha256(&hmacbuf, peer->protocol_state->shared_handshake_key.w, fastd_handshake_tlv_data(&buffer), fastd_handshake_tlv_len(&buffer));
+	memcpy(buffer.data+buffer.len-HASHBYTES, hmacbuf.b, HASHBYTES);
+
+	fastd_send_handshake(ctx, sock, local_addr, remote_addr, peer, buffer);
+}
+
+static bool establish(fastd_context_t *ctx, fastd_peer_t *peer, const char *method_name, fastd_socket_t *sock,
+		      const fastd_peer_address_t *local_addr, const fastd_peer_address_t *remote_addr, bool initiator,
+		      const aligned_int256_t *A, const aligned_int256_t *B, const aligned_int256_t *X,
+		      const aligned_int256_t *Y, const aligned_int256_t *sigma, uint64_t serial) {
+	if (serial <= peer->protocol_state->last_serial) {
+		pr_debug(ctx, "ignoring handshake from %P[%I] because of handshake key reuse", peer, remote_addr);
+		return false;
+	}
+
+	pr_verbose(ctx, "%I authorized as %P", remote_addr, peer);
+
+	if (!fastd_peer_claim_address(ctx, peer, sock, local_addr, remote_addr)) {
+		pr_warn(ctx, "can't set address %I which is used by a fixed peer", remote_addr);
+		fastd_peer_reset(ctx, peer);
+		return false;
+	}
+
+	const fastd_method_t *method = fastd_method_get_by_name(method_name);
+
+	if (is_session_valid(ctx, &peer->protocol_state->session) && !is_session_valid(ctx, &peer->protocol_state->old_session)) {
+		if (peer->protocol_state->old_session.method)
+			peer->protocol_state->old_session.method->session_free(ctx, peer->protocol_state->old_session.method_state);
+		peer->protocol_state->old_session = peer->protocol_state->session;
+	}
+	else {
+		if (peer->protocol_state->session.method)
+			peer->protocol_state->session.method->session_free(ctx, peer->protocol_state->session.method_state);
+	}
+
+	if (peer->protocol_state->old_session.method) {
+		if (peer->protocol_state->old_session.method != method) {
+			pr_debug(ctx, "method of %P[%I] has changed, terminating old session", peer, remote_addr);
+			peer->protocol_state->old_session.method->session_free(ctx, peer->protocol_state->old_session.method_state);
+			peer->protocol_state->old_session = (protocol_session_t){};
+		}
+		else {
+			peer->protocol_state->old_session.method->session_superseded(ctx, peer->protocol_state->old_session.method_state);
+		}
+	}
+
+	fastd_sha256_t hash;
+	fastd_sha256_blocks(&hash, X->p, Y->p, A->p, B->p, sigma->p, NULL);
+
+	peer->protocol_state->session.established = ctx->now;
+	peer->protocol_state->session.handshakes_cleaned = false;
+	peer->protocol_state->session.refreshing = false;
+	peer->protocol_state->session.method = method;
+	peer->protocol_state->session.method_state = method->session_init(ctx, hash.b, HASHBYTES, initiator);
+	peer->protocol_state->last_serial = serial;
+
+	fastd_peer_seen(ctx, peer);
+
+	fastd_peer_set_established(ctx, peer);
+
+	pr_verbose(ctx, "new session with %P established using method `%s'.", peer, method_name);
+
+	if (initiator)
+		fastd_peer_schedule_handshake_default(ctx, peer);
+	else
+		fastd_protocol_ec25519_fhmqvc_send_empty(ctx, peer, &peer->protocol_state->session);
+
+	return true;
+}
+
+static inline bool has_field(const fastd_handshake_t *handshake, uint8_t type, size_t length) {
+	return (handshake->records[type].length == length);
+}
+
+static void finish_handshake(fastd_context_t *ctx, fastd_socket_t *sock, const fastd_peer_address_t *local_addr, const fastd_peer_address_t *remote_addr, fastd_peer_t *peer, const handshake_key_t *handshake_key, const aligned_int256_t *peer_handshake_key,
+			     const fastd_handshake_t *handshake, const char *method) {
+	pr_debug(ctx, "finishing handshake with %P[%I]...", peer, remote_addr);
+
+	fastd_sha256_t hashbuf;
+	fastd_sha256_blocks(&hashbuf,
+			    peer_handshake_key->p,
+			    handshake_key->key1.public.p,
+			    peer->protocol_config->public_key.p,
+			    ctx->conf->protocol_config->key.public.p,
+			    NULL);
+
+	ecc_int256_t d = {{0}}, e = {{0}}, da, s;
+
+	memcpy(d.p, hashbuf.b, HASHBYTES/2);
+	memcpy(e.p, hashbuf.b+HASHBYTES/2, HASHBYTES/2);
+
+	d.p[15] |= 0x80;
+	e.p[15] |= 0x80;
+
+	ecc_25519_gf_mult(&da, &d, &ctx->conf->protocol_config->key.secret);
+	ecc_25519_gf_add(&s, &da, &handshake_key->key1.secret);
+
+	ecc_25519_work_t work, workY;
+	if (!ecc_25519_load_packed(&workY, peer_handshake_key))
+		return;
+
+	ecc_25519_scalarmult(&work, &ecc_25519_gf_order, &workY);
+	if (!ecc_25519_is_identity(&work))
+		return;
+
+	if (!ecc_25519_load_packed(&work, &peer->protocol_config->public_key))
+		return;
+
+	ecc_25519_scalarmult(&work, &e, &work);
+	ecc_25519_add(&work, &workY, &work);
+	ecc_25519_scalarmult(&work, &s, &work);
+
+	if (ecc_25519_is_identity(&work))
+		return;
+
+	aligned_int256_t sigma;
+	ecc_25519_store_packed(&sigma, &work);
+
+	fastd_sha256_t shared_handshake_key;
+	fastd_sha256_blocks(&shared_handshake_key,
+			    peer_handshake_key->p,
+			    handshake_key->key1.public.p,
+			    peer->protocol_config->public_key.p,
+			    ctx->conf->protocol_config->key.public.p,
+			    sigma.p,
+			    NULL);
+
+	bool valid;
+	if (has_field(handshake, RECORD_TLV_MAC, HASHBYTES)) {
+		uint8_t mac[HASHBYTES];
+		memcpy(mac, handshake->records[RECORD_TLV_MAC].data, HASHBYTES);
+		memset(handshake->records[RECORD_TLV_MAC].data, 0, HASHBYTES);
+
+		valid = fastd_hmacsha256_verify(mac, shared_handshake_key.w, handshake->tlv_data, handshake->tlv_len);
+	}
+	else {
+		valid = fastd_hmacsha256_blocks_verify(handshake->records[RECORD_T].data, shared_handshake_key.w, peer->protocol_config->public_key.p, peer_handshake_key->p, NULL);
+	}
+
+	if (!valid) {
+		pr_warn(ctx, "received invalid protocol handshake response from %P[%I]", peer, remote_addr);
+		return;
+	}
+
+	if (!establish(ctx, peer, method, sock, local_addr, remote_addr, true, &handshake_key->key1.public, peer_handshake_key, &ctx->conf->protocol_config->key.public,
+		       &peer->protocol_config->public_key, &sigma, handshake_key->serial))
+		return;
+
+	fastd_buffer_t buffer = fastd_handshake_new_reply(ctx, handshake, method, false, 4*(4+PUBLICKEYBYTES) + 2*(4+HASHBYTES));
+
+	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_KEY, PUBLICKEYBYTES, ctx->conf->protocol_config->key.public.p);
+	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES, peer->protocol_config->public_key.p);
+	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES, handshake_key->key1.public.p);
+	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_HANDSHAKE_KEY, PUBLICKEYBYTES, peer_handshake_key->p);
+
+	fastd_sha256_t hmacbuf;
+
+	if (!ctx->conf->secure_handshakes) {
+		fastd_hmacsha256_blocks(&hmacbuf, shared_handshake_key.w, ctx->conf->protocol_config->key.public.p, handshake_key->key1.public.p, NULL);
+		fastd_handshake_add(ctx, &buffer, RECORD_T, HASHBYTES, hmacbuf.b);
+	}
+
+	memset(&hmacbuf, 0, sizeof(hmacbuf));
+	fastd_handshake_add(ctx, &buffer, RECORD_TLV_MAC, HASHBYTES, hmacbuf.b);
+	fastd_hmacsha256(&hmacbuf, shared_handshake_key.w, fastd_handshake_tlv_data(&buffer), fastd_handshake_tlv_len(&buffer));
+	memcpy(buffer.data+buffer.len-HASHBYTES, hmacbuf.b, HASHBYTES);
+
+	fastd_send_handshake(ctx, sock, local_addr, remote_addr, peer, buffer);
+}
+
+static void handle_finish_handshake(fastd_context_t *ctx, fastd_socket_t *sock, const fastd_peer_address_t *local_addr, const fastd_peer_address_t *remote_addr,
+				    fastd_peer_t *peer, const handshake_key_t *handshake_key, const aligned_int256_t *peer_handshake_key,
+				    const fastd_handshake_t *handshake, const char *method) {
+	pr_debug(ctx, "handling handshake finish with %P[%I]...", peer, remote_addr);
+
+	if (!update_shared_handshake_key(ctx, peer, handshake_key, peer_handshake_key))
+		return;
+
+	bool valid;
+	if (has_field(handshake, RECORD_TLV_MAC, HASHBYTES)) {
+		uint8_t mac[HASHBYTES];
+		memcpy(mac, handshake->records[RECORD_TLV_MAC].data, HASHBYTES);
+		memset(handshake->records[RECORD_TLV_MAC].data, 0, HASHBYTES);
+
+		valid = fastd_hmacsha256_verify(mac, peer->protocol_state->shared_handshake_key.w, handshake->tlv_data, handshake->tlv_len);
+	}
+	else {
+		valid = fastd_hmacsha256_blocks_verify(handshake->records[RECORD_T].data, peer->protocol_state->shared_handshake_key.w, peer->protocol_config->public_key.p, peer_handshake_key->p, NULL);
+	}
+
+	if (!valid) {
+		pr_warn(ctx, "received invalid protocol handshake finish from %P[%I]", peer, remote_addr);
+		return;
+	}
+
+	establish(ctx, peer, method, sock, local_addr, remote_addr, false, peer_handshake_key, &handshake_key->key2.public, &peer->protocol_config->public_key,
+		  &ctx->conf->protocol_config->key.public, &peer->protocol_state->sigma, handshake_key->serial);
+
+	clear_shared_handshake_key(ctx, peer);
+}
+
+static fastd_peer_t* find_sender_key(fastd_context_t *ctx, const fastd_peer_address_t *address, const unsigned char key[32], fastd_peer_t *peers) {
+	errno = 0;
+
+	fastd_peer_t *ret = NULL, *peer;
+
+	for (peer = peers; peer; peer = peer->next) {
+		if (memcmp(peer->protocol_config->public_key.p, key, PUBLICKEYBYTES) == 0) {
+			if (!fastd_peer_matches_address(ctx, peer, address)) {
+				errno = EPERM;
+				return NULL;
+			}
+
+			ret = peer;
+			continue;
+		}
+
+		if (fastd_peer_owns_address(ctx, peer, address)) {
+			errno = EPERM;
+			return NULL;
+		}
+	}
+
+	if (!ret)
+		errno = ENOENT;
+
+	return ret;
+}
+
+static fastd_peer_t* match_sender_key(fastd_context_t *ctx, const fastd_socket_t *sock, const fastd_peer_address_t *address, fastd_peer_t *peer, const unsigned char key[32]) {
+	errno = 0;
+
+	if (sock->peer && peer != sock->peer)
+		exit_bug(ctx, "packet without correct peer set on dynamic socket");
+
+	if (peer) {
+		if (memcmp(peer->protocol_config->public_key.p, key, PUBLICKEYBYTES) == 0)
+			return peer;
+
+		if (fastd_peer_owns_address(ctx, peer, address)) {
+			errno = EPERM;
+			return NULL;
+		}
+	}
+
+	peer = find_sender_key(ctx, address, key, ctx->peers);
+
+	if (!peer && errno == ENOENT)
+		peer = find_sender_key(ctx, address, key, ctx->peers_temp);
+
+	return peer;
+}
+
+static size_t key_count(fastd_context_t *ctx, const unsigned char key[32]) {
+	size_t ret = 0;
+
+	fastd_peer_config_t *p;
+	for (p = ctx->conf->peers; p; p = p->next) {
+		if (!p->protocol_config)
+			continue;
+
+		if (memcmp(p->protocol_config->public_key.p, key, 32) == 0)
+			ret++;
+	}
+
+	return ret;
+}
+
+bool fastd_protocol_ec25519_fhmqvc_peer_check(fastd_context_t *ctx, fastd_peer_config_t *peer_conf) {
+	if (!peer_conf->protocol_config)
+		return false;
+
+	if (memcmp(peer_conf->protocol_config->public_key.p, ctx->conf->protocol_config->key.public.p, 32) == 0)
+		return false;
+
+	if (key_count(ctx, peer_conf->protocol_config->public_key.p) > 1) {
+		char buf[65];
+		hexdump(buf, peer_conf->protocol_config->public_key.p);
+		pr_warn(ctx, "more than one peer is configured with key %s, disabling %s", buf, peer_conf->name);
+		return false;
+	}
+
+	return true;
+}
+
+bool fastd_protocol_ec25519_fhmqvc_peer_check_temporary(fastd_context_t *ctx, fastd_peer_t *peer) {
+	if (key_count(ctx, peer->protocol_config->public_key.p)) {
+		char buf[65];
+		hexdump(buf, peer->protocol_config->public_key.p);
+		pr_info(ctx, "key %s is configured now, deleting temporary peer.", buf);
+		return false;
+	}
+
+	return true;
+}
+
+static inline fastd_peer_t* add_temporary(fastd_context_t *ctx, const fastd_peer_address_t *local_addr, const fastd_peer_address_t *remote_addr, const unsigned char key[32]) {
+	if (!fastd_peer_allow_unknown(ctx)) {
+		pr_debug(ctx, "ignoring handshake from %I (unknown key)", remote_addr);
+		return NULL;
+	}
+
+	if (key_count(ctx, key)) {
+		pr_debug(ctx, "ignoring handshake from %I (disabled key)", remote_addr);
+		return NULL;
+	}
+
+	fastd_peer_t *peer = fastd_peer_add_temporary(ctx);
+
+	peer->protocol_config = malloc(sizeof(fastd_protocol_peer_config_t));
+	memcpy(peer->protocol_config->public_key.p, key, PUBLICKEYBYTES);
+
+	/* Ugly hack */
+	peer->protocol_state->last_serial--;
+
+	if (!fastd_peer_verify_temporary(ctx, peer, local_addr, remote_addr)) {
+		pr_debug(ctx, "ignoring handshake from %P[%I] (verification failed)", peer, remote_addr);
+		fastd_peer_delete(ctx, peer);
+		return NULL;
+	}
+
+	return peer;
+}
+
+static inline keypair_t* get_handshake_keypair(handshake_key_t *handshake_key, uint8_t type) {
+	return (type % 2) ? &handshake_key->key2 : &handshake_key->key1;
+}
+
+void fastd_protocol_ec25519_fhmqvc_handshake_handle(fastd_context_t *ctx, fastd_socket_t *sock, const fastd_peer_address_t *local_addr, const fastd_peer_address_t *remote_addr, fastd_peer_t *peer, const fastd_handshake_t *handshake, const char *method) {
+	bool temporary_added = false;
+
+	fastd_protocol_ec25519_fhmqvc_maintenance(ctx);
+
+	if (!has_field(handshake, RECORD_SENDER_KEY, PUBLICKEYBYTES)) {
+		pr_debug(ctx, "received handshake without sender key from %I", remote_addr);
+		return;
+	}
+
+	peer = match_sender_key(ctx, sock, remote_addr, peer, handshake->records[RECORD_SENDER_KEY].data);
+	if (!peer) {
+		switch (errno) {
+		case EPERM:
+			pr_debug(ctx, "ignoring handshake from %I (incorrect source address)", remote_addr);
+			return;
+
+		case ENOENT:
+			peer = add_temporary(ctx, local_addr, remote_addr, handshake->records[RECORD_SENDER_KEY].data);
+			if (peer) {
+				temporary_added = true;
+				break;
+			}
+
+			return;
+
+		default:
+			exit_bug(ctx, "match_sender_key: unknown error");
+		}
+	}
+
+	if (fastd_peer_is_temporary(peer) && !temporary_added) {
+		if (!fastd_peer_verify_temporary(ctx, peer, local_addr, remote_addr)) {
+			pr_debug(ctx, "ignoring handshake from %P[%I] (verification failed)", peer, remote_addr);
+			return;
+		}
+	}
+
+	if (!fastd_peer_may_connect(ctx, peer)) {
+		pr_debug(ctx, "ignoring handshake from %P[%I] because of local constraints", peer, remote_addr);
+		return;
+	}
+
+	if (backoff(ctx, peer)) {
+		pr_debug(ctx, "received repeated handshakes from %P[%I], ignoring", peer, remote_addr);
+		return;
+	}
+
+	if (has_field(handshake, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES)) {
+		if (memcmp(ctx->conf->protocol_config->key.public.p, handshake->records[RECORD_RECEIPIENT_KEY].data, PUBLICKEYBYTES) != 0) {
+			pr_debug(ctx, "received protocol handshake with wrong receipient key from %P[%I]", peer, remote_addr);
+			return;
+		}
+	}
+
+	if (!has_field(handshake, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES)) {
+		pr_debug(ctx, "received handshake without sender handshake key from %P[%I]", peer, remote_addr);
+		return;
+	}
+
+	aligned_int256_t peer_handshake_key;
+	memcpy(peer_handshake_key.p, handshake->records[RECORD_SENDER_HANDSHAKE_KEY].data, PUBLICKEYBYTES);
+
+	if (handshake->type == 1) {
+		if (timespec_diff(&ctx->now, &peer->last_handshake_response) < (int)ctx->conf->min_handshake_interval*1000
+		    && fastd_peer_address_equal(remote_addr, &peer->last_handshake_response_address)) {
+			pr_debug(ctx, "not responding repeated handshake from %P[%I]", peer, remote_addr);
+			return;
+		}
+
+		pr_verbose(ctx, "received handshake from %P[%I]%s%s", peer, remote_addr, handshake->peer_version ? " using fastd " : "", handshake->peer_version ?: "");
+
+		peer->last_handshake_response = ctx->now;
+		peer->last_handshake_response_address = *remote_addr;
+		respond_handshake(ctx, sock, local_addr, remote_addr, peer, &ctx->protocol_state->handshake_key, &peer_handshake_key, handshake, method);
+		return;
+	}
+
+	if (!has_field(handshake, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES)) {
+		pr_debug(ctx, "received handshake reply without receipient key from %P[%I]", peer, remote_addr);
+		return;
+	}
+
+	if (!has_field(handshake, RECORD_RECEIPIENT_HANDSHAKE_KEY, PUBLICKEYBYTES)) {
+		pr_debug(ctx, "received handshake reply without receipient handshake key from %P[%I]", peer, remote_addr);
+		return;
+	}
+
+	if (!has_field(handshake, RECORD_TLV_MAC, HASHBYTES)) {
+		if (ctx->conf->secure_handshakes || !has_field(handshake, RECORD_T, HASHBYTES)) {
+			pr_debug(ctx, "received handshake reply without HMAC from %P[%I]", peer, remote_addr);
+			return;
+		}
+	}
+
+	handshake_key_t *handshake_key;
+	if (is_handshake_key_valid(ctx, &ctx->protocol_state->handshake_key) &&
+	    memcmp(get_handshake_keypair(&ctx->protocol_state->handshake_key, handshake->type)->public.p, handshake->records[RECORD_RECEIPIENT_HANDSHAKE_KEY].data, PUBLICKEYBYTES) == 0) {
+		handshake_key = &ctx->protocol_state->handshake_key;
+	}
+	else if (is_handshake_key_valid(ctx, &ctx->protocol_state->prev_handshake_key) &&
+		 memcmp(get_handshake_keypair(&ctx->protocol_state->prev_handshake_key, handshake->type)->public.p, handshake->records[RECORD_RECEIPIENT_HANDSHAKE_KEY].data, PUBLICKEYBYTES) == 0) {
+		handshake_key = &ctx->protocol_state->prev_handshake_key;
+	}
+	else {
+		pr_debug(ctx, "received handshake reply with unexpected receipient handshake key from %P[%I]", peer, remote_addr);
+		return;
+	}
+
+	switch (handshake->type) {
+	case 2:
+		pr_verbose(ctx, "received handshake response from %P[%I]%s%s", peer, remote_addr, handshake->peer_version ? " using fastd " : "", handshake->peer_version ?: "");
+
+		finish_handshake(ctx, sock, local_addr, remote_addr, peer, handshake_key, &peer_handshake_key, handshake, method);
+		break;
+
+	case 3:
+		pr_debug(ctx, "received handshake finish from %P[%I]%s%s", peer, remote_addr, handshake->peer_version ? " using fastd " : "", handshake->peer_version ?: "");
+
+		handle_finish_handshake(ctx, sock, local_addr, remote_addr, peer, handshake_key, &peer_handshake_key, handshake, method);
+		break;
+
+	default:
+		pr_debug(ctx, "received handshake reply with unknown type %u from %P[%I]", handshake->type, peer, remote_addr);
+	}
+}