From 3e8e646b91b7256ab46eb767951d2028f0dda0eb Mon Sep 17 00:00:00 2001 From: Matthias Schiffer Date: Mon, 18 Nov 2013 03:49:25 +0100 Subject: Some work towards a composable GMAC method --- src/methods/generic_gmac/generic_gmac.c | 345 ++++++++++++++++++++++++++++++++ 1 file changed, 345 insertions(+) create mode 100644 src/methods/generic_gmac/generic_gmac.c (limited to 'src/methods/generic_gmac/generic_gmac.c') diff --git a/src/methods/generic_gmac/generic_gmac.c b/src/methods/generic_gmac/generic_gmac.c new file mode 100644 index 0000000..2a44858 --- /dev/null +++ b/src/methods/generic_gmac/generic_gmac.c @@ -0,0 +1,345 @@ +/* + Copyright (c) 2012-2013, Matthias Schiffer + 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 "../common.h" + + +struct fastd_method_session_state { + fastd_method_common_t common; + + const fastd_cipher_t *cipher; + const fastd_cipher_context_t *cipher_ctx; + fastd_cipher_state_t *cipher_state; + size_t ivlen; + + const fastd_cipher_t *gmac_cipher; + const fastd_cipher_context_t *gmac_cipher_ctx; + fastd_cipher_state_t *gmac_cipher_state; + size_t gmac_ivlen; + + const fastd_mac_t *ghash; + const fastd_mac_context_t *ghash_ctx; + fastd_mac_state_t *ghash_state; +}; + + +static bool cipher_get(fastd_context_t *ctx, const char *name, const fastd_cipher_t **cipher, const fastd_cipher_context_t **cctx, const fastd_cipher_t **gmac_cipher, const fastd_cipher_context_t **gmac_cctx) { + if (!fastd_mac_available("ghash")) + return false; + + size_t len = strlen(name); + + if (len < 5) + return false; + + if (strcmp(name+len-5, "-gmac")) + return false; + + char cipher_name[len]; + memcpy(cipher_name, name, len-4); + strncpy(cipher_name+len-4, "ctr", 4); + + char *gmac_cipher_name = strchr(cipher_name, '+'); + + if (!gmac_cipher_name) + return false; + + *gmac_cipher_name = 0; + gmac_cipher_name++; + + if (ctx) { + *cipher = fastd_cipher_get_by_name(ctx, cipher_name, cctx); + *gmac_cipher = fastd_cipher_get_by_name(ctx, gmac_cipher_name, gmac_cctx); + return *cipher && *gmac_cipher; + } + else { + return fastd_cipher_available(cipher_name) && fastd_cipher_available(gmac_cipher_name); + } +} + + +static bool method_provides(const char *name) { + return cipher_get(NULL, name, NULL, NULL, NULL, NULL); +} + +static size_t method_max_packet_size(fastd_context_t *ctx) { + return (fastd_max_packet_size(ctx) + COMMON_HEADBYTES + 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 size_t method_key_length(fastd_context_t *ctx, const char *name) { + const fastd_cipher_t *cipher = NULL; + const fastd_cipher_context_t *cctx; + + const fastd_cipher_t *gmac_cipher = NULL; + const fastd_cipher_context_t *gmac_cctx; + + if (!cipher_get(ctx, name, &cipher, &cctx, &gmac_cipher, &gmac_cctx)) + exit_bug(ctx, "generic-gmac: can't get cipher key length"); + + return cipher->key_length(ctx, cctx) + gmac_cipher->key_length(ctx, gmac_cctx); +} + +static fastd_method_session_state_t* method_session_init(fastd_context_t *ctx, const char *name, const uint8_t *secret, bool initiator) { + fastd_method_session_state_t *session = malloc(sizeof(fastd_method_session_state_t)); + + fastd_method_common_init(ctx, &session->common, initiator); + + if (!cipher_get(ctx, name, &session->cipher, &session->cipher_ctx, &session->gmac_cipher, &session->gmac_cipher_ctx)) + exit_bug(ctx, "generic-gmac: can't instanciate cipher"); + + session->cipher_state = session->cipher->init_state(ctx, session->cipher_ctx, secret); + session->ivlen = session->cipher->iv_length(ctx, session->cipher_state); + if (session->ivlen && session->ivlen <= COMMON_NONCEBYTES) + exit_bug(ctx, "generic-gmac: iv_length to small"); + + session->gmac_cipher_state = session->gmac_cipher->init_state(ctx, session->gmac_cipher_ctx, secret + session->cipher->key_length(ctx, session->cipher_ctx)); + session->gmac_ivlen = session->gmac_cipher->iv_length(ctx, session->gmac_cipher_state); + if (session->gmac_ivlen <= COMMON_NONCEBYTES) + exit_bug(ctx, "generic-gmac: gmac cipher iv_length to small"); + + static const fastd_block128_t zeroblock = {}; + fastd_block128_t H; + + uint8_t zeroiv[session->gmac_ivlen]; + memset(zeroiv, 0, session->gmac_ivlen); + + session->gmac_cipher->crypt(ctx, session->gmac_cipher_state, &H, &zeroblock, sizeof(fastd_block128_t), zeroiv); + + session->ghash = fastd_mac_get_by_name(ctx, "ghash", &session->ghash_ctx); + if (!session->ghash) + exit_bug(ctx, "generic-gmac: can't instanciate ghash mac"); + + session->ghash_state = session->ghash->init_state(ctx, session->ghash_ctx, H.b); + + return session; +} + +static bool method_session_is_valid(fastd_context_t *ctx, fastd_method_session_state_t *session) { + return (session && fastd_method_session_common_is_valid(ctx, &session->common)); +} + +static bool method_session_is_initiator(fastd_context_t *ctx UNUSED, fastd_method_session_state_t *session) { + return fastd_method_session_common_is_initiator(&session->common); +} + +static bool method_session_want_refresh(fastd_context_t *ctx, fastd_method_session_state_t *session) { + return fastd_method_session_common_want_refresh(ctx, &session->common); +} + +static void method_session_superseded(fastd_context_t *ctx, fastd_method_session_state_t *session) { + fastd_method_session_common_superseded(ctx, &session->common); +} + +static void method_session_free(fastd_context_t *ctx, fastd_method_session_state_t *session) { + if (session) { + session->cipher->free_state(ctx, session->cipher_state); + session->gmac_cipher->free_state(ctx, session->gmac_cipher_state); + session->ghash->free_state(ctx, session->ghash_state); + + free(session); + } +} + +static inline void put_size(fastd_block128_t *out, size_t len) { + memset(out, 0, sizeof(fastd_block128_t)); + out->b[3] = len >> 29; + out->b[4] = len >> 21; + out->b[5] = len >> 13; + out->b[6] = len >> 5; + out->b[7] = 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(COMMON_HEADBYTES, 16), sizeof(fastd_block128_t)+tail_len); + + if (tail_len) + memset(in.data+in.len, 0, tail_len); + + int n_blocks = block_count(in.len, sizeof(fastd_block128_t)); + + fastd_block128_t *inblocks = in.data; + fastd_block128_t *outblocks = out->data; + fastd_block128_t sig; + + uint8_t gmac_nonce[session->gmac_ivlen]; + memset(gmac_nonce, 0, session->gmac_ivlen); + memcpy(gmac_nonce, session->common.send_nonce, COMMON_NONCEBYTES); + gmac_nonce[session->gmac_ivlen-1] = 1; + + bool ok = session->gmac_cipher->crypt(ctx, session->gmac_cipher_state, outblocks, inblocks, sizeof(fastd_block128_t), gmac_nonce); + + if (ok) { + uint8_t nonce[session->ivlen]; + if (session->ivlen) { + memset(nonce, 0, session->ivlen); + memcpy(nonce, session->common.send_nonce, COMMON_NONCEBYTES); + nonce[session->ivlen-1] = 1; + } + + ok = session->cipher->crypt(ctx, session->cipher_state, outblocks+1, inblocks+1, (n_blocks-1)*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 = session->ghash->hash(ctx, session->ghash_state, &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, COMMON_HEADBYTES); + + memcpy(out->data, session->common.send_nonce, COMMON_NONCEBYTES); + fastd_method_increment_nonce(&session->common); + + ((uint8_t*)out->data)[COMMON_NONCEBYTES] = 0; /* flags */ + + 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 < COMMON_HEADBYTES+sizeof(fastd_block128_t)) + return false; + + if (!method_session_is_valid(ctx, session)) + return false; + + if (((const uint8_t*)in.data)[COMMON_NONCEBYTES]) /* flags */ + return false; + + int64_t age; + if (!fastd_method_is_nonce_valid(ctx, &session->common, in.data, &age)) + return false; + + uint8_t gmac_nonce[session->gmac_ivlen]; + memset(gmac_nonce, 0, session->gmac_ivlen); + memcpy(gmac_nonce, in.data, COMMON_NONCEBYTES); + gmac_nonce[session->gmac_ivlen-1] = 1; + + uint8_t nonce[session->ivlen]; + if (session->ivlen) { + memset(nonce, 0, session->ivlen); + memcpy(nonce, in.data, COMMON_NONCEBYTES); + nonce[session->ivlen-1] = 1; + } + + fastd_buffer_push_head(ctx, &in, COMMON_HEADBYTES); + + 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 = block_count(in.len, sizeof(fastd_block128_t)); + + fastd_block128_t *inblocks = in.data; + fastd_block128_t *outblocks = out->data; + fastd_block128_t sig; + + bool ok = session->gmac_cipher->crypt(ctx, session->gmac_cipher_state, outblocks, inblocks, sizeof(fastd_block128_t), gmac_nonce); + + if (ok) + ok = session->cipher->crypt(ctx, session->cipher_state, outblocks+1, inblocks+1, (n_blocks-1)*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 = session->ghash->hash(ctx, session->ghash_state, &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 (!fastd_method_reorder_check(ctx, peer, &session->common, nonce, age)) { + fastd_buffer_free(*out); + *out = fastd_buffer_alloc(ctx, 0, 0, 0); + } + + return true; +} + +const fastd_method_t fastd_method_generic_gmac = { + .provides = method_provides, + + .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, + + .key_length = method_key_length, + .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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