Line data    Source code

       1             : /*
       2             :  * ctr_prng.c 
       3             :  *
       4             :  * counter mode based pseudorandom source
       5             :  *
       6             :  * David A. McGrew
       7             :  * Cisco Systems, Inc.
       8             :  */
       9             : /*
      10             :  *      
      11             :  * Copyright(c) 2001-2006 Cisco Systems, Inc.
      12             :  * All rights reserved.
      13             :  * 
      14             :  * Redistribution and use in source and binary forms, with or without
      15             :  * modification, are permitted provided that the following conditions
      16             :  * are met:
      17             :  * 
      18             :  *   Redistributions of source code must retain the above copyright
      19             :  *   notice, this list of conditions and the following disclaimer.
      20             :  * 
      21             :  *   Redistributions in binary form must reproduce the above
      22             :  *   copyright notice, this list of conditions and the following
      23             :  *   disclaimer in the documentation and/or other materials provided
      24             :  *   with the distribution.
      25             :  * 
      26             :  *   Neither the name of the Cisco Systems, Inc. nor the names of its
      27             :  *   contributors may be used to endorse or promote products derived
      28             :  *   from this software without specific prior written permission.
      29             :  * 
      30             :  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
      31             :  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
      32             :  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
      33             :  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
      34             :  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
      35             :  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
      36             :  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
      37             :  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
      38             :  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
      39             :  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
      40             :  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
      41             :  * OF THE POSSIBILITY OF SUCH DAMAGE.
      42             :  *
      43             :  */
      44             : 
      45             : 
      46             : #include "prng.h"
      47             : 
      48             : /* single, global prng structure */
      49             : 
      50             : ctr_prng_t ctr_prng;
      51             : 
      52             : err_status_t
      53           0 : ctr_prng_init(rand_source_func_t random_source) {
      54             :   uint8_t tmp_key[32];
      55             :   err_status_t status;
      56             : 
      57             :   /* initialize output count to zero */
      58           0 :   ctr_prng.octet_count = 0;
      59             : 
      60             :   /* set random source */
      61           0 :   ctr_prng.rand = random_source;
      62             :   
      63             :   /* initialize secret key from random source */
      64           0 :   status = random_source(tmp_key, 32);
      65           0 :   if (status) 
      66           0 :     return status;
      67             : 
      68             :   /* initialize aes ctr context with random key */
      69           0 :   status = aes_icm_context_init(&ctr_prng.state, tmp_key, 30);
      70           0 :   if (status) 
      71           0 :     return status;
      72             : 
      73           0 :   return err_status_ok;
      74             : }
      75             : 
      76             : err_status_t
      77           0 : ctr_prng_get_octet_string(void *dest, uint32_t len) {
      78             :   err_status_t status;
      79             : 
      80             :   /* 
      81             :    * if we need to re-initialize the prng, do so now 
      82             :    *
      83             :    * avoid 32-bit overflows by subtracting instead of adding
      84             :    */
      85           0 :   if (ctr_prng.octet_count > MAX_PRNG_OUT_LEN - len) {
      86           0 :     status = ctr_prng_init(ctr_prng.rand);    
      87           0 :     if (status)
      88           0 :       return status;
      89             :   }
      90           0 :   ctr_prng.octet_count += len;
      91             : 
      92             :   /*
      93             :    * write prng output 
      94             :    */
      95           0 :   status = aes_icm_output(&ctr_prng.state, (uint8_t*)dest, len);
      96           0 :   if (status)
      97           0 :     return status;
      98             :   
      99           0 :   return err_status_ok;
     100             : }
     101             : 
     102             : err_status_t
     103           0 : ctr_prng_deinit(void) {
     104             : 
     105             :   /* nothing */
     106             :   
     107           0 :   return err_status_ok;  
     108             : }