/* * rdbx.c * * a replay database with extended range, using a rollover counter * * David A. McGrew * Cisco Systems, Inc. */ /* * * Copyright (c) 2001-2017, 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. * */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include "rdbx.h" /* * from RFC 3711: * * A receiver reconstructs the index i of a packet with sequence * number SEQ using the estimate * * i = 2^16 * v + SEQ, * * where v is chosen from the set { ROC-1, ROC, ROC+1 } such that i is * closest to the value 2^16 * ROC + 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 srtp_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 srtp_xtd_seq_num_t can be estimated by using a * local srtp_xtd_seq_num_t as a basis. This is done using the function * srtp_index_guess(&local, &guess, seq_from_packet). This function * returns the difference of the guess and the local value. The local * srtp_xtd_seq_num_t can be moved forward to the guess using the function * srtp_index_advance(&guess, delta), where delta is the difference. * * * A srtp_rdbx_t consists of a srtp_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 srtp_index_init(srtp_xtd_seq_num_t *pi) { … } void srtp_index_advance(srtp_xtd_seq_num_t *pi, srtp_sequence_number_t s) { … } /* * srtp_index_guess(local, guess, s) * * given a srtp_xtd_seq_num_t local (which represents the last * known-to-be-good received srtp_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! */ int32_t srtp_index_guess(const srtp_xtd_seq_num_t *local, srtp_xtd_seq_num_t *guess, srtp_sequence_number_t s) { … } /* * rdbx * */ /* * srtp_rdbx_init(&r, ws) initializes the srtp_rdbx_t pointed to by r with * window size ws */ srtp_err_status_t srtp_rdbx_init(srtp_rdbx_t *rdbx, unsigned long ws) { … } /* * srtp_rdbx_dealloc(&r) frees memory for the srtp_rdbx_t pointed to by r */ srtp_err_status_t srtp_rdbx_dealloc(srtp_rdbx_t *rdbx) { … } /* * srtp_rdbx_set_roc(rdbx, roc) initalizes the srtp_rdbx_t at the location rdbx * to have the rollover counter value roc. If that value is less than * the current rollover counter value, then the function returns * srtp_err_status_replay_old; otherwise, srtp_err_status_ok is returned. * */ srtp_err_status_t srtp_rdbx_set_roc(srtp_rdbx_t *rdbx, uint32_t roc) { … } /* * srtp_rdbx_get_packet_index(rdbx) returns the value of the packet index * for the srtp_rdbx_t pointed to by rdbx * */ srtp_xtd_seq_num_t srtp_rdbx_get_packet_index(const srtp_rdbx_t *rdbx) { … } /* * srtp_rdbx_get_window_size(rdbx) returns the value of the window size * for the srtp_rdbx_t pointed to by rdbx * */ unsigned long srtp_rdbx_get_window_size(const srtp_rdbx_t *rdbx) { … } /* * srtp_rdbx_check(&r, delta) checks to see if the srtp_xtd_seq_num_t * which is at rdbx->index + delta is in the rdb */ srtp_err_status_t srtp_rdbx_check(const srtp_rdbx_t *rdbx, int delta) { … } /* * srtp_rdbx_add_index adds the srtp_xtd_seq_num_t at rdbx->window_start + d to * replay_db (and does *not* check if that srtp_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 */ srtp_err_status_t srtp_rdbx_add_index(srtp_rdbx_t *rdbx, int delta) { … } /* * srtp_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 */ int32_t srtp_rdbx_estimate_index(const srtp_rdbx_t *rdbx, srtp_xtd_seq_num_t *guess, srtp_sequence_number_t s) { … } /* * srtp_rdbx_get_roc(rdbx) * * Get the current rollover counter * */ uint32_t srtp_rdbx_get_roc(const srtp_rdbx_t *rdbx) { … } /* * srtp_rdbx_set_roc_seq(rdbx, roc, seq) initalizes the srtp_rdbx_t at the * location rdbx to have the rollover counter value roc and packet sequence * number seq. If the new rollover counter value is less than the current * rollover counter value, then the function returns * srtp_err_status_replay_old, otherwise, srtp_err_status_ok is returned. */ srtp_err_status_t srtp_rdbx_set_roc_seq(srtp_rdbx_t *rdbx, uint32_t roc, uint16_t seq) { … }
Codebase Browser
chromium