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Diffstat (limited to 'srtp/crypto/replay/rdbx.c')
| -rw-r--r-- | srtp/crypto/replay/rdbx.c | 289 |
1 files changed, 0 insertions, 289 deletions
diff --git a/srtp/crypto/replay/rdbx.c b/srtp/crypto/replay/rdbx.c deleted file mode 100644 index 12e4e8f..0000000 --- a/srtp/crypto/replay/rdbx.c +++ /dev/null @@ -1,289 +0,0 @@ -/* - * rdbx.c - * - * a replay database with extended range, using a rollover counter - * - * David A. McGrew - * Cisco Systems, Inc. - */ - -/* - * - * Copyright (c) 2001-2006, Cisco Systems, Inc. - * All rights reserved. - * - * Redistribution and use in source and binary forms, with or without - * modification, are permitted provided that the following conditions - * are met: - * - * Redistributions of source code must retain the above copyright - * notice, this list of conditions and the following disclaimer. - * - * 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. - * - * Neither the name of the Cisco Systems, Inc. nor the names of its - * contributors may be used to endorse or promote products derived - * from this software without specific prior written permission. - * - * 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 HOLDERS 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 "rdbx.h" - -#define rdbx_high_bit_in_bitmask 127 - -/* - * from draft-ietf-avt-srtp-00.txt: - * - * A receiver reconstructs the index i of a packet with sequence - * number s using the estimate - * - * i = 65,536 * t + s, - * - * where t is chosen from the set { r-1, r, r+1 } such that i is - * closest to the value 65,536 * r + s_l. If the value r+1 is used, - * then the rollover counter r in the cryptographic context is - * incremented by one (if the packet containing s is authentic). - */ - - - -/* - * rdbx implementation notes - * - * A xtd_seq_num_t is essentially a sequence number for which some of - * the data on the wire are implicit. It logically consists of a - * rollover counter and a sequence number; the sequence number is the - * explicit part, and the rollover counter is the implicit part. - * - * Upon receiving a sequence_number (e.g. in a newly received SRTP - * packet), the complete xtd_seq_num_t can be estimated by using a - * local xtd_seq_num_t as a basis. This is done using the function - * index_guess(&local, &guess, seq_from_packet). This function - * returns the difference of the guess and the local value. The local - * xtd_seq_num_t can be moved forward to the guess using the function - * index_advance(&guess, delta), where delta is the difference. - * - * - * A rdbx_t consists of a xtd_seq_num_t and a bitmask. The index is highest - * sequence number that has been received, and the bitmask indicates - * which of the recent indicies have been received as well. The - * highest bit in the bitmask corresponds to the index in the bitmask. - */ - - -void -index_init(xtd_seq_num_t *pi) { -#ifdef NO_64BIT_MATH - *pi = make64(0,0); -#else - *pi = 0; -#endif -} - -void -index_advance(xtd_seq_num_t *pi, sequence_number_t s) { -#ifdef NO_64BIT_MATH - /* a > ~b means a+b will generate a carry */ - /* s is uint16 here */ - *pi = make64(high32(*pi) + (s > ~low32(*pi) ? 1 : 0),low32(*pi) + s); -#else - *pi += s; -#endif -} - - -/* - * index_guess(local, guess, s) - * - * given a xtd_seq_num_t local (which represents the last - * known-to-be-good received xtd_seq_num_t) and a sequence number s - * (from a newly arrived packet), sets the contents of *guess to - * contain the best guess of the packet index to which s corresponds, - * and returns the difference between *guess and *local - * - * nota bene - the output is a signed integer, DON'T cast it to a - * unsigned integer! - */ - -int -index_guess(const xtd_seq_num_t *local, - xtd_seq_num_t *guess, - sequence_number_t s) { -#ifdef NO_64BIT_MATH - uint32_t local_roc = ((high32(*local) << 16) | - (low32(*local) >> 16)); - uint16_t local_seq = (uint16_t) (low32(*local)); -#else - uint32_t local_roc = (uint32_t)(*local >> 16); - uint16_t local_seq = (uint16_t) *local; -#endif -#ifdef NO_64BIT_MATH - uint32_t guess_roc = ((high32(*guess) << 16) | - (low32(*guess) >> 16)); - uint16_t guess_seq = (uint16_t) (low32(*guess)); -#else - uint32_t guess_roc = (uint32_t)(*guess >> 16); - uint16_t guess_seq = (uint16_t) *guess; -#endif - int difference; - - if (local_seq < seq_num_median) { - if (s - local_seq > seq_num_median) { - guess_roc = local_roc - 1; - difference = seq_num_max - s + local_seq; - } else { - guess_roc = local_roc; - difference = s - local_seq; - } - } else { - if (local_seq - seq_num_median > s) { - guess_roc = local_roc+1; - difference = seq_num_max - local_seq + s; - } else { - difference = s - local_seq; - guess_roc = local_roc; - } - } - guess_seq = s; - - /* Note: guess_roc is 32 bits, so this generates a 48-bit result! */ -#ifdef NO_64BIT_MATH - *guess = make64(guess_roc >> 16, - (guess_roc << 16) | guess_seq); -#else - *guess = (((uint64_t) guess_roc) << 16) | guess_seq; -#endif - - return difference; -} - -/* - * rdbx - * - */ - - -/* - * rdbx_init(&r) initalizes the rdbx_t pointed to by r - */ - -err_status_t -rdbx_init(rdbx_t *rdbx) { - v128_set_to_zero(&rdbx->bitmask); - index_init(&rdbx->index); - - return err_status_ok; -} - - -/* - * rdbx_check(&r, delta) checks to see if the xtd_seq_num_t - * which is at rdbx->index + delta is in the rdb - */ - -err_status_t -rdbx_check(const rdbx_t *rdbx, int delta) { - - if (delta > 0) { /* if delta is positive, it's good */ - return err_status_ok; - } else if (rdbx_high_bit_in_bitmask + delta < 0) { - /* if delta is lower than the bitmask, it's bad */ - return err_status_replay_old; - } else if (v128_get_bit(&rdbx->bitmask, - rdbx_high_bit_in_bitmask + delta) == 1) { - /* delta is within the window, so check the bitmask */ - return err_status_replay_fail; - } - /* otherwise, the index is okay */ - - return err_status_ok; -} - -/* - * rdbx_add_index adds the xtd_seq_num_t at rdbx->window_start + d to - * replay_db (and does *not* check if that xtd_seq_num_t appears in db) - * - * this function should be called only after replay_check has - * indicated that the index does not appear in the rdbx, e.g., a mutex - * should protect the rdbx between these calls if need be - */ - -err_status_t -rdbx_add_index(rdbx_t *rdbx, int delta) { - - if (delta > 0) { - /* shift forward by delta */ - index_advance(&rdbx->index, delta); - v128_left_shift(&rdbx->bitmask, delta); - v128_set_bit(&rdbx->bitmask, 127); - } else { - /* delta is in window, so flip bit in bitmask */ - v128_set_bit(&rdbx->bitmask, -delta); - } - - /* note that we need not consider the case that delta == 0 */ - - return err_status_ok; -} - - - -/* - * rdbx_estimate_index(rdbx, guess, s) - * - * given an rdbx and a sequence number s (from a newly arrived packet), - * sets the contents of *guess to contain the best guess of the packet - * index to which s corresponds, and returns the difference between - * *guess and the locally stored synch info - */ - -int -rdbx_estimate_index(const rdbx_t *rdbx, - xtd_seq_num_t *guess, - sequence_number_t s) { - - /* - * if the sequence number and rollover counter in the rdbx are - * non-zero, then use the index_guess(...) function, otherwise, just - * set the rollover counter to zero (since the index_guess(...) - * function might incorrectly guess that the rollover counter is - * 0xffffffff) - */ - -#ifdef NO_64BIT_MATH - /* seq_num_median = 0x8000 */ - if (high32(rdbx->index) > 0 || - low32(rdbx->index) > seq_num_median) -#else - if (rdbx->index > seq_num_median) -#endif - return index_guess(&rdbx->index, guess, s); - -#ifdef NO_64BIT_MATH - *guess = make64(0,(uint32_t) s); -#else - *guess = s; -#endif - -#ifdef NO_64BIT_MATH - return s - (uint16_t) low32(rdbx->index); -#else - return s - (uint16_t) rdbx->index; -#endif -} |