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Diffstat (limited to 'src/method_xsalsa20_poly1305.c')
| -rw-r--r-- | src/method_xsalsa20_poly1305.c | 205 |
1 files changed, 205 insertions, 0 deletions
diff --git a/src/method_xsalsa20_poly1305.c b/src/method_xsalsa20_poly1305.c new file mode 100644 index 0000000..5194a4d --- /dev/null +++ b/src/method_xsalsa20_poly1305.c @@ -0,0 +1,205 @@ +/* + Copyright (c) 2012, 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]; +}; + + +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]) { + if ((nonce[0] & 1) != (old_nonce[0] & 1)) + return false; + + int i; + for (i = NONCEBYTES-1; i >= 0; i--) { + if (nonce[i] > old_nonce[i]) + return true; + if (nonce[i] < old_nonce[i]) + return false; + } + + return false; +} + +static size_t method_max_packet_size(fastd_context *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 *ctx) { + return crypto_secretbox_xsalsa20poly1305_ZEROBYTES; +} + +static size_t method_min_decrypt_head_space(fastd_context *ctx) { + return (crypto_secretbox_xsalsa20poly1305_BOXZEROBYTES - NONCEBYTES); +} + +static fastd_method_session_state* method_session_init(fastd_context *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 *session = malloc(sizeof(fastd_method_session_state)); + + 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; + + 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 *ctx, fastd_method_session_state *session) { + return (session && timespec_after(&session->valid_till, &ctx->now)); +} + +static bool method_session_is_initiator(fastd_context *ctx, fastd_method_session_state *session) { + return (session->send_nonce[0] & 1); +} + +static bool method_session_want_refresh(fastd_context *ctx, fastd_method_session_state *session) { + return (method_session_is_initiator(ctx, session) && timespec_after(&ctx->now, &session->refresh_after)); +} + +static void method_session_free(fastd_context *ctx, fastd_method_session_state *session) { + if(session) { + memset(session, 0, sizeof(fastd_method_session_state)); + free(session); + } +} + +static bool method_encrypt(fastd_context *ctx, fastd_method_session_state *session, fastd_buffer *out, fastd_buffer in) { + fastd_buffer_pull_head(&in, crypto_secretbox_xsalsa20poly1305_ZEROBYTES); + memset(in.data, 0, crypto_secretbox_xsalsa20poly1305_ZEROBYTES); + + *out = fastd_buffer_alloc(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(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 *ctx, fastd_method_session_state *session, fastd_buffer *out, fastd_buffer 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); + + if (!is_nonce_valid(nonce, session->receive_nonce)) + return false; + + fastd_buffer_pull_head(&in, crypto_secretbox_xsalsa20poly1305_BOXZEROBYTES-NONCEBYTES); + memset(in.data, 0, crypto_secretbox_xsalsa20poly1305_BOXZEROBYTES); + + *out = fastd_buffer_alloc(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(&in, crypto_secretbox_xsalsa20poly1305_BOXZEROBYTES-NONCEBYTES); + memcpy(in.data, nonce, NONCEBYTES); + return false; + } + + fastd_buffer_free(in); + + fastd_buffer_push_head(out, crypto_secretbox_xsalsa20poly1305_ZEROBYTES); + + memcpy(session->receive_nonce, nonce, NONCEBYTES); + + return true; +} + +const fastd_method 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, + + .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_free = method_session_free, + + .encrypt = method_encrypt, + .decrypt = method_decrypt, +}; |