Organize method and protocol source files into distinct source directories

7 files changed, 698 insertions, 0 deletions

diff --git a/src/methods/CMakeLists.txt b/src/methods/CMakeLists.txt
new file mode 100644
index 0000000..55f41d2
--- /dev/null
+++ b/src/methods/CMakeLists.txt
@@ -0,0 +1,19 @@
+set(METHODS null)
+
+if(WITH_METHOD_XSALSA20_POLY1305)
+  list(APPEND METHODS xsalsa20_poly1305)
+endif(WITH_METHOD_XSALSA20_POLY1305)
+
+if(WITH_METHOD_AES128_GCM)
+  list(APPEND METHODS aes128_gcm)
+endif(WITH_METHOD_AES128_GCM)
+
+
+set(METHOD_OBJECTS "")
+
+foreach(method ${METHODS})
+  add_subdirectory(${method})
+  list(APPEND METHOD_OBJECTS $<TARGET_OBJECTS:method_${method}>)
+endforeach(method)
+
+set(METHOD_OBJECTS "${METHOD_OBJECTS}" PARENT_SCOPE)
diff --git a/src/methods/aes128_gcm/CMakeLists.txt b/src/methods/aes128_gcm/CMakeLists.txt
new file mode 100644
index 0000000..1c5aa3f
--- /dev/null
+++ b/src/methods/aes128_gcm/CMakeLists.txt
@@ -0,0 +1,6 @@
+include_directories(BEFORE ${FASTD_SOURCE_DIR}/src ${FASTD_BINARY_DIR} ${NACL_INCLUDE_DIR})
+
+add_library(method_aes128_gcm OBJECT
+  aes128_gcm.c
+)
+set_property(TARGET method_aes128_gcm PROPERTY COMPILE_FLAGS "${FASTD_CFLAGS}")
diff --git a/src/methods/aes128_gcm/aes128_gcm.c b/src/methods/aes128_gcm/aes128_gcm.c
new file mode 100644
index 0000000..46dba5c
--- /dev/null
+++ b/src/methods/aes128_gcm/aes128_gcm.c
@@ -0,0 +1,317 @@
+/*
+  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 <fastd.h>
+#include <crypto.h>
+
+
+#define KEYBYTES 16
+#define NONCEBYTES 7
+
+struct fastd_method_session_state {
+	struct timespec valid_till;
+	struct timespec refresh_after;
+
+	uint8_t send_nonce[NONCEBYTES];
+	uint8_t receive_nonce[NONCEBYTES];
+
+	struct timespec receive_last;
+	uint64_t receive_reorder_seen;
+
+	fastd_crypto_aes128ctr_state_t *cstate_aes128ctr;
+	fastd_crypto_ghash_state_t *cstate_ghash;
+};
+
+
+static inline void increment_nonce(uint8_t nonce[NONCEBYTES]) {
+	nonce[0] += 2;
+
+	if (nonce[0] == 0 || nonce[0] == 1) {
+		int i;
+		for (i = 1; i < NONCEBYTES; i++) {
+			nonce[i]++;
+			if (nonce[i] != 0)
+				break;
+		}
+	}
+}
+
+static inline bool is_nonce_valid(const uint8_t nonce[NONCEBYTES], const uint8_t old_nonce[NONCEBYTES], int64_t *age) {
+	if ((nonce[0] & 1) != (old_nonce[0] & 1))
+		return false;
+
+	int i;
+	*age = 0;
+
+	for (i = NONCEBYTES-1; i >= 0; i--) {
+		*age *= 256;
+		*age += old_nonce[i]-nonce[i];
+	}
+
+	*age /= 2;
+	return true;
+}
+
+static size_t method_max_packet_size(fastd_context_t *ctx) {
+	return (fastd_max_packet_size(ctx) + NONCEBYTES + sizeof(fastd_block128_t));
+}
+
+
+static size_t method_min_encrypt_head_space(fastd_context_t *ctx UNUSED) {
+	return sizeof(fastd_block128_t);
+}
+
+static size_t method_min_decrypt_head_space(fastd_context_t *ctx UNUSED) {
+	return 0;
+}
+
+static size_t method_min_encrypt_tail_space(fastd_context_t *ctx UNUSED) {
+	return (sizeof(fastd_block128_t)-1);
+}
+
+static size_t method_min_decrypt_tail_space(fastd_context_t *ctx UNUSED) {
+	return (2*sizeof(fastd_block128_t)-1);
+}
+
+
+static fastd_method_session_state_t* method_session_init(fastd_context_t *ctx, uint8_t *secret, size_t length, bool initiator) {
+	int i;
+
+	if (length < KEYBYTES)
+		exit_bug(ctx, "aes128-gcm: tried to init with short secret");
+
+	fastd_method_session_state_t *session = malloc(sizeof(fastd_method_session_state_t));
+
+	session->valid_till = ctx->now;
+	session->valid_till.tv_sec += ctx->conf->key_valid;
+
+	session->refresh_after = ctx->now;
+	session->refresh_after.tv_sec += ctx->conf->key_refresh - fastd_rand(ctx, 0, ctx->conf->key_refresh_splay);
+
+	fastd_block128_t key;
+	memcpy(key.b, secret, sizeof(fastd_block128_t));
+	session->cstate_aes128ctr = ctx->conf->crypto_aes128ctr->set_key(ctx, ctx->crypto_aes128ctr, &key);
+
+	static const fastd_block128_t zeroblock = {};
+	fastd_block128_t H;
+
+	ctx->conf->crypto_aes128ctr->crypt(ctx, session->cstate_aes128ctr, &H, &zeroblock, sizeof(fastd_block128_t), &zeroblock);
+
+	session->cstate_ghash = ctx->conf->crypto_ghash->set_h(ctx, ctx->crypto_ghash, &H);
+
+	session->send_nonce[0] = initiator ? 3 : 2;
+	session->receive_nonce[0] = initiator ? 0 : 1;
+
+	for (i = 1; i < NONCEBYTES; i++) {
+		session->send_nonce[i] = 0;
+		session->receive_nonce[i] = 0;
+	}
+
+	return session;
+}
+
+static bool method_session_is_valid(fastd_context_t *ctx, fastd_method_session_state_t *session) {
+	return (session && timespec_after(&session->valid_till, &ctx->now));
+}
+
+static bool method_session_is_initiator(fastd_context_t *ctx UNUSED, fastd_method_session_state_t *session) {
+	return (session->send_nonce[0] & 1);
+}
+
+static bool method_session_want_refresh(fastd_context_t *ctx, fastd_method_session_state_t *session) {
+	return timespec_after(&ctx->now, &session->refresh_after);
+}
+
+static void method_session_superseded(fastd_context_t *ctx, fastd_method_session_state_t *session) {
+	struct timespec valid_max = ctx->now;
+	valid_max.tv_sec += ctx->conf->key_valid_old;
+
+	if (timespec_after(&session->valid_till, &valid_max))
+		session->valid_till = valid_max;
+}
+
+static void method_session_free(fastd_context_t *ctx, fastd_method_session_state_t *session) {
+	if(session) {
+		ctx->conf->crypto_aes128ctr->free_state(ctx, session->cstate_aes128ctr);
+		ctx->conf->crypto_ghash->free_state(ctx, session->cstate_ghash);
+
+		secure_memzero(session, sizeof(fastd_method_session_state_t));
+		free(session);
+	}
+}
+
+static inline void put_size(fastd_block128_t *out, size_t len) {
+	memset(out, 0, sizeof(fastd_block128_t)-5);
+	out->b[sizeof(fastd_block128_t)-5] = len >> 29;
+	out->b[sizeof(fastd_block128_t)-4] = len >> 21;
+	out->b[sizeof(fastd_block128_t)-3] = len >> 13;
+	out->b[sizeof(fastd_block128_t)-2] = len >> 5;
+	out->b[sizeof(fastd_block128_t)-1] = len << 3;
+}
+
+static bool method_encrypt(fastd_context_t *ctx, fastd_peer_t *peer UNUSED, fastd_method_session_state_t *session, fastd_buffer_t *out, fastd_buffer_t in) {
+	fastd_buffer_pull_head(ctx, &in, sizeof(fastd_block128_t));
+	memset(in.data, 0, sizeof(fastd_block128_t));
+
+	size_t tail_len = alignto(in.len, sizeof(fastd_block128_t))-in.len;
+	*out = fastd_buffer_alloc(ctx, in.len, alignto(NONCEBYTES, 16), sizeof(fastd_block128_t)+tail_len);
+
+	if (tail_len)
+		memset(in.data+in.len, 0, tail_len);
+
+	fastd_block128_t nonce;
+	memcpy(nonce.b, session->send_nonce, NONCEBYTES);
+	memset(nonce.b+NONCEBYTES, 0, sizeof(fastd_block128_t)-NONCEBYTES-1);
+	nonce.b[sizeof(fastd_block128_t)-1] = 1;
+
+	int n_blocks = (in.len+sizeof(fastd_block128_t)-1)/sizeof(fastd_block128_t);
+
+	fastd_block128_t *inblocks = in.data;
+	fastd_block128_t *outblocks = out->data;
+	fastd_block128_t sig;
+
+	bool ok = ctx->conf->crypto_aes128ctr->crypt(ctx, session->cstate_aes128ctr, outblocks, inblocks, n_blocks*sizeof(fastd_block128_t), &nonce);
+
+	if (ok) {
+		if (tail_len)
+			memset(out->data+out->len, 0, tail_len);
+
+		put_size(&outblocks[n_blocks], in.len-sizeof(fastd_block128_t));
+
+		ok = ctx->conf->crypto_ghash->hash(ctx, session->cstate_ghash, &sig, outblocks+1, n_blocks);
+	}
+
+	if (!ok) {
+		/* restore original buffer */
+		fastd_buffer_push_head(ctx, &in, sizeof(fastd_block128_t));
+		fastd_buffer_free(*out);
+		return false;
+	}
+
+	xor_a(&outblocks[0], &sig);
+
+	fastd_buffer_free(in);
+
+	fastd_buffer_pull_head(ctx, out, NONCEBYTES);
+	memcpy(out->data, session->send_nonce, NONCEBYTES);
+	increment_nonce(session->send_nonce);
+
+	return true;
+}
+
+static bool method_decrypt(fastd_context_t *ctx, fastd_peer_t *peer, fastd_method_session_state_t *session, fastd_buffer_t *out, fastd_buffer_t in) {
+	if (in.len < NONCEBYTES+sizeof(fastd_block128_t))
+		return false;
+
+	if (!method_session_is_valid(ctx, session))
+		return false;
+
+	fastd_block128_t nonce;
+	memcpy(nonce.b, in.data, NONCEBYTES);
+	memset(nonce.b+NONCEBYTES, 0, sizeof(fastd_block128_t)-NONCEBYTES-1);
+	nonce.b[sizeof(fastd_block128_t)-1] = 1;
+
+	int64_t age;
+	if (!is_nonce_valid(nonce.b, session->receive_nonce, &age))
+		return false;
+
+	if (age >= 0) {
+		if (timespec_diff(&ctx->now, &session->receive_last) > (int)ctx->conf->reorder_time*1000)
+			return false;
+
+		if (age > ctx->conf->reorder_count)
+			return false;
+	}
+
+	fastd_buffer_push_head(ctx, &in, NONCEBYTES);
+
+	size_t tail_len = alignto(in.len, sizeof(fastd_block128_t))-in.len;
+	*out = fastd_buffer_alloc(ctx, in.len, 0, tail_len);
+
+	int n_blocks = (in.len+sizeof(fastd_block128_t)-1)/sizeof(fastd_block128_t);
+
+	fastd_block128_t *inblocks = in.data;
+	fastd_block128_t *outblocks = out->data;
+	fastd_block128_t sig;
+
+	bool ok = ctx->conf->crypto_aes128ctr->crypt(ctx, session->cstate_aes128ctr, outblocks, inblocks, n_blocks*sizeof(fastd_block128_t), &nonce);
+
+	if (ok) {
+		if (tail_len)
+			memset(in.data+in.len, 0, tail_len);
+
+		put_size(&inblocks[n_blocks], in.len-sizeof(fastd_block128_t));
+
+		ok = ctx->conf->crypto_ghash->hash(ctx, session->cstate_ghash, &sig, inblocks+1, n_blocks);
+	}
+
+	if (!ok || memcmp(&sig, &outblocks[0], sizeof(fastd_block128_t)) != 0) {
+		fastd_buffer_free(*out);
+		return false;
+	}
+
+	fastd_buffer_free(in);
+
+	fastd_buffer_push_head(ctx, out, sizeof(fastd_block128_t));
+
+	if (age < 0) {
+		session->receive_reorder_seen >>= age;
+		session->receive_reorder_seen |= (1 >> (age+1));
+		memcpy(session->receive_nonce, nonce.b, NONCEBYTES);
+		session->receive_last = ctx->now;
+	}
+	else if (age == 0 || session->receive_reorder_seen & (1 << (age-1))) {
+		pr_debug(ctx, "dropping duplicate packet from %P (age %u)", peer, (unsigned)age);
+		fastd_buffer_free(*out);
+		*out = fastd_buffer_alloc(ctx, 0, 0, 0);
+	}
+	else {
+		pr_debug2(ctx, "accepting reordered packet from %P (age %u)", peer, (unsigned)age);
+		session->receive_reorder_seen |= (1 << (age-1));
+	}
+
+	return true;
+}
+
+const fastd_method_t fastd_method_aes128_gcm = {
+	.name = "aes128-gcm",
+
+	.max_packet_size = method_max_packet_size,
+	.min_encrypt_head_space = method_min_encrypt_head_space,
+	.min_decrypt_head_space = method_min_decrypt_head_space,
+	.min_encrypt_tail_space = method_min_encrypt_tail_space,
+	.min_decrypt_tail_space = method_min_decrypt_tail_space,
+
+	.session_init = method_session_init,
+	.session_is_valid = method_session_is_valid,
+	.session_is_initiator = method_session_is_initiator,
+	.session_want_refresh = method_session_want_refresh,
+	.session_superseded = method_session_superseded,
+	.session_free = method_session_free,
+
+	.encrypt = method_encrypt,
+	.decrypt = method_decrypt,
+};
diff --git a/src/methods/null/CMakeLists.txt b/src/methods/null/CMakeLists.txt
new file mode 100644
index 0000000..91c1832
--- /dev/null
+++ b/src/methods/null/CMakeLists.txt
@@ -0,0 +1,6 @@
+include_directories(BEFORE ${FASTD_SOURCE_DIR}/src ${FASTD_BINARY_DIR})
+
+add_library(method_null OBJECT
+  null.c
+)
+set_property(TARGET method_null PROPERTY COMPILE_FLAGS "${FASTD_CFLAGS}")
diff --git a/src/methods/null/null.c b/src/methods/null/null.c
new file mode 100644
index 0000000..643e5e1
--- /dev/null
+++ b/src/methods/null/null.c
@@ -0,0 +1,96 @@
+/*
+  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 <fastd.h>
+
+
+struct fastd_method_session_state {
+	bool valid;
+	bool initiator;
+};
+
+
+static size_t method_max_packet_size(fastd_context_t *ctx) {
+	return fastd_max_packet_size(ctx);
+}
+
+static size_t method_min_head_tail_space(fastd_context_t *ctx UNUSED) {
+	return 0;
+}
+
+static fastd_method_session_state_t* method_session_init(fastd_context_t *ctx UNUSED, uint8_t *secret UNUSED, size_t length UNUSED, bool initiator) {
+	fastd_method_session_state_t *session = malloc(sizeof(fastd_method_session_state_t));
+
+	session->valid = true;
+	session->initiator = initiator;
+
+	return session;
+}
+
+static bool method_session_is_valid(fastd_context_t *ctx UNUSED, fastd_method_session_state_t *session) {
+	return (session && session->valid);
+}
+
+static bool method_session_is_initiator(fastd_context_t *ctx UNUSED, fastd_method_session_state_t *session) {
+	return (session->initiator);
+}
+
+static bool method_session_want_refresh(fastd_context_t *ctx UNUSED, fastd_method_session_state_t *session UNUSED) {
+	return false;
+}
+
+static void method_session_superseded(fastd_context_t *ctx UNUSED, fastd_method_session_state_t *session) {
+	session->valid = false;
+}
+
+static void method_session_free(fastd_context_t *ctx UNUSED, fastd_method_session_state_t *session) {
+	free(session);
+}
+
+static bool method_passthrough(fastd_context_t *ctx UNUSED, fastd_peer_t *peer UNUSED, fastd_method_session_state_t *session UNUSED, fastd_buffer_t *out, fastd_buffer_t in) {
+	*out = in;
+	return true;
+}
+
+const fastd_method_t fastd_method_null = {
+	.name = "null",
+
+	.max_packet_size = method_max_packet_size,
+	.min_encrypt_head_space = method_min_head_tail_space,
+	.min_decrypt_head_space = method_min_head_tail_space,
+	.min_encrypt_tail_space = method_min_head_tail_space,
+	.min_decrypt_tail_space = method_min_head_tail_space,
+
+	.session_init = method_session_init,
+	.session_is_valid = method_session_is_valid,
+	.session_is_initiator = method_session_is_initiator,
+	.session_want_refresh = method_session_want_refresh,
+	.session_superseded = method_session_superseded,
+	.session_free = method_session_free,
+
+	.encrypt = method_passthrough,
+	.decrypt = method_passthrough,
+};
diff --git a/src/methods/xsalsa20_poly1305/CMakeLists.txt b/src/methods/xsalsa20_poly1305/CMakeLists.txt
new file mode 100644
index 0000000..09b029c
--- /dev/null
+++ b/src/methods/xsalsa20_poly1305/CMakeLists.txt
@@ -0,0 +1,6 @@
+include_directories(BEFORE ${FASTD_SOURCE_DIR}/src ${FASTD_BINARY_DIR} ${NACL_INCLUDE_DIR})
+
+add_library(method_xsalsa20_poly1305 OBJECT
+  xsalsa20_poly1305.c
+)
+set_property(TARGET method_xsalsa20_poly1305 PROPERTY COMPILE_FLAGS "${FASTD_CFLAGS}")
diff --git a/src/methods/xsalsa20_poly1305/xsalsa20_poly1305.c b/src/methods/xsalsa20_poly1305/xsalsa20_poly1305.c
new file mode 100644
index 0000000..d891aa5
--- /dev/null
+++ b/src/methods/xsalsa20_poly1305/xsalsa20_poly1305.c
@@ -0,0 +1,248 @@
+/*
+  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 <fastd.h>
+
+#include <crypto_secretbox_xsalsa20poly1305.h>
+
+
+#define NONCEBYTES 7
+
+
+struct fastd_method_session_state {
+	struct timespec valid_till;
+	struct timespec refresh_after;
+
+	uint8_t key[crypto_secretbox_xsalsa20poly1305_KEYBYTES];
+
+	uint8_t send_nonce[NONCEBYTES];
+	uint8_t receive_nonce[NONCEBYTES];
+
+	struct timespec receive_last;
+	uint64_t receive_reorder_seen;
+};
+
+
+static inline void increment_nonce(uint8_t nonce[NONCEBYTES]) {
+	nonce[0] += 2;
+
+	if (nonce[0] == 0 || nonce[0] == 1) {
+		int i;
+		for (i = 1; i < NONCEBYTES; i++) {
+			nonce[i]++;
+			if (nonce[i] != 0)
+				break;
+		}
+	}
+}
+
+static inline bool is_nonce_valid(const uint8_t nonce[NONCEBYTES], const uint8_t old_nonce[NONCEBYTES], int64_t *age) {
+	if ((nonce[0] & 1) != (old_nonce[0] & 1))
+		return false;
+
+	int i;
+	*age = 0;
+
+	for (i = NONCEBYTES-1; i >= 0; i--) {
+		*age *= 256;
+		*age += old_nonce[i]-nonce[i];
+	}
+
+	*age /= 2;
+	return true;
+}
+
+static size_t method_max_packet_size(fastd_context_t *ctx) {
+	return (fastd_max_packet_size(ctx) + NONCEBYTES + crypto_secretbox_xsalsa20poly1305_ZEROBYTES - crypto_secretbox_xsalsa20poly1305_BOXZEROBYTES);
+}
+
+static size_t method_min_encrypt_head_space(fastd_context_t *ctx UNUSED) {
+	return crypto_secretbox_xsalsa20poly1305_ZEROBYTES;
+}
+
+static size_t method_min_decrypt_head_space(fastd_context_t *ctx UNUSED) {
+	return (crypto_secretbox_xsalsa20poly1305_BOXZEROBYTES - NONCEBYTES);
+}
+
+static size_t method_min_tail_space(fastd_context_t *ctx UNUSED) {
+	return 0;
+}
+
+static fastd_method_session_state_t* method_session_init(fastd_context_t *ctx, uint8_t *secret, size_t length, bool initiator) {
+	int i;
+
+	if (length < crypto_secretbox_xsalsa20poly1305_KEYBYTES)
+		exit_bug(ctx, "xsalsa20-poly1305: tried to init with short secret");
+
+	fastd_method_session_state_t *session = malloc(sizeof(fastd_method_session_state_t));
+
+	session->valid_till = ctx->now;
+	session->valid_till.tv_sec += ctx->conf->key_valid;
+
+	session->refresh_after = ctx->now;
+	session->refresh_after.tv_sec += ctx->conf->key_refresh - fastd_rand(ctx, 0, ctx->conf->key_refresh_splay);
+
+	memcpy(session->key, secret, crypto_secretbox_xsalsa20poly1305_KEYBYTES);
+
+	session->send_nonce[0] = initiator ? 3 : 2;
+	session->receive_nonce[0] = initiator ? 0 : 1;
+
+	for (i = 1; i < NONCEBYTES; i++) {
+		session->send_nonce[i] = 0;
+		session->receive_nonce[i] = 0;
+	}
+
+	return session;
+}
+
+static bool method_session_is_valid(fastd_context_t *ctx, fastd_method_session_state_t *session) {
+	return (session && timespec_after(&session->valid_till, &ctx->now));
+}
+
+static bool method_session_is_initiator(fastd_context_t *ctx UNUSED, fastd_method_session_state_t *session) {
+	return (session->send_nonce[0] & 1);
+}
+
+static bool method_session_want_refresh(fastd_context_t *ctx, fastd_method_session_state_t *session) {
+	return timespec_after(&ctx->now, &session->refresh_after);
+}
+
+static void method_session_superseded(fastd_context_t *ctx, fastd_method_session_state_t *session) {
+	struct timespec valid_max = ctx->now;
+	valid_max.tv_sec += ctx->conf->key_valid_old;
+
+	if (timespec_after(&session->valid_till, &valid_max))
+		session->valid_till = valid_max;
+}
+
+static void method_session_free(fastd_context_t *ctx UNUSED, fastd_method_session_state_t *session) {
+	if(session) {
+		secure_memzero(session, sizeof(fastd_method_session_state_t));
+		free(session);
+	}
+}
+
+static bool method_encrypt(fastd_context_t *ctx, fastd_peer_t *peer UNUSED, fastd_method_session_state_t *session, fastd_buffer_t *out, fastd_buffer_t in) {
+	fastd_buffer_pull_head(ctx, &in, crypto_secretbox_xsalsa20poly1305_ZEROBYTES);
+	memset(in.data, 0, crypto_secretbox_xsalsa20poly1305_ZEROBYTES);
+
+	*out = fastd_buffer_alloc(ctx, in.len, 0, 0);
+
+	uint8_t nonce[crypto_secretbox_xsalsa20poly1305_NONCEBYTES];
+	memcpy(nonce, session->send_nonce, NONCEBYTES);
+	memset(nonce+NONCEBYTES, 0, crypto_secretbox_xsalsa20poly1305_NONCEBYTES-NONCEBYTES);
+
+	crypto_secretbox_xsalsa20poly1305(out->data, in.data, in.len, nonce, session->key);
+
+	fastd_buffer_free(in);
+
+	fastd_buffer_push_head(ctx, out, crypto_secretbox_xsalsa20poly1305_BOXZEROBYTES-NONCEBYTES);
+	memcpy(out->data, session->send_nonce, NONCEBYTES);
+
+	increment_nonce(session->send_nonce);
+
+	return true;
+}
+
+static bool method_decrypt(fastd_context_t *ctx, fastd_peer_t *peer, fastd_method_session_state_t *session, fastd_buffer_t *out, fastd_buffer_t in) {
+	if (in.len < NONCEBYTES)
+		return false;
+
+	if (!method_session_is_valid(ctx, session))
+		return false;
+
+	uint8_t nonce[crypto_secretbox_xsalsa20poly1305_NONCEBYTES];
+	memcpy(nonce, in.data, NONCEBYTES);
+	memset(nonce+NONCEBYTES, 0, crypto_secretbox_xsalsa20poly1305_NONCEBYTES-NONCEBYTES);
+
+	int64_t age;
+	if (!is_nonce_valid(nonce, session->receive_nonce, &age))
+		return false;
+
+	if (age >= 0) {
+		if (timespec_diff(&ctx->now, &session->receive_last) > (int)ctx->conf->reorder_time*1000)
+			return false;
+
+		if (age > ctx->conf->reorder_count)
+			return false;
+	}
+
+	fastd_buffer_pull_head(ctx, &in, crypto_secretbox_xsalsa20poly1305_BOXZEROBYTES-NONCEBYTES);
+	memset(in.data, 0, crypto_secretbox_xsalsa20poly1305_BOXZEROBYTES);
+
+	*out = fastd_buffer_alloc(ctx, in.len, 0, 0);
+
+	if (crypto_secretbox_xsalsa20poly1305_open(out->data, in.data, in.len, nonce, session->key) != 0) {
+		fastd_buffer_free(*out);
+
+		/* restore input buffer */
+		fastd_buffer_push_head(ctx, &in, crypto_secretbox_xsalsa20poly1305_BOXZEROBYTES-NONCEBYTES);
+		memcpy(in.data, nonce, NONCEBYTES);
+		return false;
+	}
+
+	fastd_buffer_free(in);
+
+	if (age < 0) {
+		session->receive_reorder_seen >>= age;
+		session->receive_reorder_seen |= (1 >> (age+1));
+		memcpy(session->receive_nonce, nonce, NONCEBYTES);
+		session->receive_last = ctx->now;
+	}
+	else if (age == 0 || session->receive_reorder_seen & (1 << (age-1))) {
+		pr_debug(ctx, "dropping duplicate packet from %P (age %u)", peer, (unsigned)age);
+		fastd_buffer_free(*out);
+		*out = fastd_buffer_alloc(ctx, crypto_secretbox_xsalsa20poly1305_ZEROBYTES, 0, 0);
+	}
+	else {
+		pr_debug2(ctx, "accepting reordered packet from %P (age %u)", peer, (unsigned)age);
+		session->receive_reorder_seen |= (1 << (age-1));
+	}
+
+	fastd_buffer_push_head(ctx, out, crypto_secretbox_xsalsa20poly1305_ZEROBYTES);
+
+	return true;
+}
+
+const fastd_method_t fastd_method_xsalsa20_poly1305 = {
+	.name = "xsalsa20-poly1305",
+
+	.max_packet_size = method_max_packet_size,
+	.min_encrypt_head_space = method_min_encrypt_head_space,
+	.min_decrypt_head_space = method_min_decrypt_head_space,
+	.min_encrypt_tail_space = method_min_tail_space,
+	.min_decrypt_tail_space = method_min_tail_space,
+
+	.session_init = method_session_init,
+	.session_is_valid = method_session_is_valid,
+	.session_is_initiator = method_session_is_initiator,
+	.session_want_refresh = method_session_want_refresh,
+	.session_superseded = method_session_superseded,
+	.session_free = method_session_free,
+
+	.encrypt = method_encrypt,
+	.decrypt = method_decrypt,
+};