diff options
Diffstat (limited to 'src/methods/aes128_gcm')
| -rw-r--r-- | src/methods/aes128_gcm/CMakeLists.txt | 6 | ||||
| -rw-r--r-- | src/methods/aes128_gcm/aes128_gcm.c | 317 |
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, +}; 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