The Tor Browser: comparison netwerk/srtp/src/crypto/replay/rdbx.c

--1:000000000000
+:57e5368a13e6
+/*
+* 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"
+/*
+* 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 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, ws) initializes the rdbx_t pointed to by r with window size ws
+*/
+err_status_t
+rdbx_init(rdbx_t *rdbx, unsigned long ws) {
+if (ws == 0)
+return err_status_bad_param;
+if (bitvector_alloc(&rdbx->bitmask, ws) != 0)
+return err_status_alloc_fail;
+index_init(&rdbx->index);
+return err_status_ok;
+}
+/*
+*  rdbx_dealloc(&r) frees memory for the rdbx_t pointed to by r
+*/
+err_status_t
+rdbx_dealloc(rdbx_t *rdbx) {
+bitvector_dealloc(&rdbx->bitmask);
+return err_status_ok;
+}
+/*
+* rdbx_set_roc(rdbx, roc) initalizes the 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
+* err_status_replay_old; otherwise, err_status_ok is returned.
+*
+*/
+err_status_t
+rdbx_set_roc(rdbx_t *rdbx, uint32_t roc) {
+bitvector_set_to_zero(&rdbx->bitmask);
+#ifdef NO_64BIT_MATH
+#error not yet implemented
+#else
+/* make sure that we're not moving backwards */
+if (roc < (rdbx->index >> 16))
+return err_status_replay_old;
+rdbx->index &= 0xffff;   /* retain lowest 16 bits */
+rdbx->index |= ((uint64_t)roc) << 16;  /* set ROC */
+#endif
+return err_status_ok;
+}
+/*
+* rdbx_get_packet_index(rdbx) returns the value of the packet index
+* for the rdbx_t pointed to by rdbx
+*
+*/
+xtd_seq_num_t
+rdbx_get_packet_index(const rdbx_t *rdbx) {
+return rdbx->index;
+}
+/*
+* rdbx_get_window_size(rdbx) returns the value of the window size
+* for the rdbx_t pointed to by rdbx
+*
+*/
+unsigned long
+rdbx_get_window_size(const rdbx_t *rdbx) {
+return bitvector_get_length(&rdbx->bitmask);
+}
+/*
+* 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 ((int)(bitvector_get_length(&rdbx->bitmask) - 1) + delta < 0) {
+/* if delta is lower than the bitmask, it's bad */
+return err_status_replay_old;
+} else if (bitvector_get_bit(&rdbx->bitmask,
+			       (int)(bitvector_get_length(&rdbx->bitmask) - 1) + 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);
+bitvector_left_shift(&rdbx->bitmask, delta);
+bitvector_set_bit(&rdbx->bitmask, bitvector_get_length(&rdbx->bitmask) - 1);
+} else {
+/* delta is in window */
+bitvector_set_bit(&rdbx->bitmask, bitvector_get_length(&rdbx->bitmask) -1 + 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
+}

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comparison: netwerk/srtp/src/crypto/replay/rdbx.c

netwerk/srtp/src/crypto/replay/rdbx.c