Update libsrtp to version 2.0

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 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)
+{
+#ifdef NO_64BIT_MATH
+    *pi = make64(0, 0);
+#else
+    *pi = 0;
+#endif
+}
+
+void srtp_index_advance (srtp_xtd_seq_num_t *pi, srtp_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
+}
+
+
+/*
+ * 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!
+ */
+
+int srtp_index_guess (const srtp_xtd_seq_num_t *local, srtp_xtd_seq_num_t *guess, srtp_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
+ *
+ */
+
+
+/*
+ *  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)
+{
+    if (ws == 0) {
+        return srtp_err_status_bad_param;
+    }
+
+    if (bitvector_alloc(&rdbx->bitmask, ws) != 0) {
+        return srtp_err_status_alloc_fail;
+    }
+
+    srtp_index_init(&rdbx->index);
+
+    return srtp_err_status_ok;
+}
+
+/*
+ *  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)
+{
+    bitvector_dealloc(&rdbx->bitmask);
+
+    return srtp_err_status_ok;
+}
+
+/*
+ * 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)
+{
+    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 srtp_err_status_replay_old;
+    }
+
+    rdbx->index &= 0xffff;                /* retain lowest 16 bits */
+    rdbx->index |= ((uint64_t)roc) << 16; /* set ROC */
+#endif
+
+    return srtp_err_status_ok;
+}
+
+/*
+ * 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)
+{
+    return rdbx->index;
+}
+
+/*
+ * 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)
+{
+    return bitvector_get_length(&rdbx->bitmask);
+}
+
+/*
+ * 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)
+{
+
+    if (delta > 0) {     /* if delta is positive, it's good */
+        return srtp_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 srtp_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 srtp_err_status_replay_fail;
+    }
+    /* otherwise, the index is okay */
+
+    return srtp_err_status_ok;
+}
+
+/*
+ * 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)
+{
+
+    if (delta > 0) {
+        /* shift forward by delta */
+        srtp_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 srtp_err_status_ok;
+}
+
+
+
+/*
+ * 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
+ */
+int srtp_rdbx_estimate_index (const srtp_rdbx_t *rdbx, srtp_xtd_seq_num_t *guess, srtp_sequence_number_t s)
+{
+
+    /*
+     * if the sequence number and rollover counter in the rdbx are
+     * non-zero, then use the srtp_index_guess(...) function, otherwise, just
+     * set the rollover counter to zero (since the srtp_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 srtp_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
+}