Update libsrtp to version 2.0

srtp/crypto/replay/rdbx.c

-/*
- * 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.
- *
- */
-
-#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 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 = s - local_seq - seq_num_max;
-    } else {
-      guess_roc = local_roc;
-      difference = s - local_seq;
-    }
-  } else {
-    if (local_seq - seq_num_median > s) {
-      guess_roc = local_roc + 1;
-      difference = s - local_seq + seq_num_max;
-    } else {
-      guess_roc = local_roc;
-      difference = s - local_seq;
-    }
-  }
-  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
-}