Add current version of libSRTP from CVS.

libsrtp/crypto/replay/rdb.c

+/*
+ * rdb.c
+ *
+ * Implements a replay database for packet security
+ *
+ * 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 "rdb.h"
+
+
+/*
+ * this implementation of a replay database works as follows:
+ * 
+ * window_start is the index of the first packet in the window
+ * bitmask      a bit-buffer, containing the most recently entered
+ *              index as the leftmost bit 
+ *
+ */
+
+/* rdb_init initalizes rdb */
+
+err_status_t
+rdb_init(rdb_t *rdb) {
+  v128_set_to_zero(&rdb->bitmask);
+  rdb->window_start = 0;
+  return err_status_ok;
+}
+
+/*
+ * rdb_check checks to see if index appears in rdb
+ */
+
+err_status_t
+rdb_check(const rdb_t *rdb, uint32_t p_index) {
+  
+  /* if the index appears after (or at very end of) the window, its good */
+  if (p_index >= rdb->window_start + rdb_bits_in_bitmask)
+    return err_status_ok;
+  
+  /* if the index appears before the window, its bad */
+  if (p_index < rdb->window_start)
+    return err_status_replay_old;
+
+  /* otherwise, the index appears within the window, so check the bitmask */
+  if (v128_get_bit(&rdb->bitmask, (p_index - rdb->window_start)) == 1)
+    return err_status_replay_fail;    
+      
+  /* otherwise, the index is okay */
+  return err_status_ok;
+}
+
+/*
+ * rdb_add_index adds index to rdb_t (and does *not* check if
+ * index appears in db)
+ *
+ * this function should be called only after rdb_check has
+ * indicated that the index does not appear in the rdb, e.g., a mutex
+ * should protect the rdb between these calls
+ */
+
+err_status_t
+rdb_add_index(rdb_t *rdb, uint32_t p_index) {
+  int delta;  
+
+  /* here we *assume* that p_index > rdb->window_start */
+
+  delta = (p_index - rdb->window_start);    
+  if (delta < rdb_bits_in_bitmask) {
+
+    /* if the p_index is within the window, set the appropriate bit */
+    v128_set_bit(&rdb->bitmask, delta);
+
+  } else { 
+    
+    delta -= rdb_bits_in_bitmask - 1;
+
+    /* shift the window forward by delta bits*/
+    v128_left_shift(&rdb->bitmask, delta);
+    v128_set_bit(&rdb->bitmask, rdb_bits_in_bitmask-1);
+    rdb->window_start += delta;
+
+  }    
+
+  return err_status_ok;
+}
+
+err_status_t
+rdb_increment(rdb_t *rdb) {
+
+  if (rdb->window_start++ > 0x7fffffff)
+    return err_status_key_expired;
+  return err_status_ok;
+}
+
+uint32_t
+rdb_get_value(const rdb_t *rdb) {
+  return rdb->window_start;
+}