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-rw-r--r--src/methods/aes128_gcm/CMakeLists.txt6
-rw-r--r--src/methods/aes128_gcm/aes128_gcm.c317
2 files changed, 323 insertions, 0 deletions
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,
+};