Index: crypto/replay/rdbx.c |
diff --git a/crypto/replay/rdbx.c b/crypto/replay/rdbx.c |
new file mode 100644 |
index 0000000000000000000000000000000000000000..e1279df1478ea0431d5f814e0462ccfb5d0455e4 |
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+++ b/crypto/replay/rdbx.c |
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+/* |
+ * 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 |
+} |