The Tor Browser: netwerk/srtp/src/crypto/rng/ctr

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

     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  */

    46 #include "prng.h"

    48 /* single, global prng structure */

    50 ctr_prng_t ctr_prng;

    52 err_status_t

    53 ctr_prng_init(rand_source_func_t random_source) {

    54   uint8_t tmp_key[32];

    55   err_status_t status;

    57   /* initialize output count to zero */

    58   ctr_prng.octet_count = 0;

    60   /* set random source */

    61   ctr_prng.rand = random_source;

    63   /* initialize secret key from random source */

    64   status = random_source(tmp_key, 32);

    65   if (status)

    66     return status;

    68   /* initialize aes ctr context with random key */

    69   status = aes_icm_context_init(&ctr_prng.state, tmp_key, 30);

    70   if (status)

    71     return status;

    73   return err_status_ok;

    74 }

    76 err_status_t

    77 ctr_prng_get_octet_string(void *dest, uint32_t len) {

    78   err_status_t status;

    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   if (ctr_prng.octet_count > MAX_PRNG_OUT_LEN - len) {

    86     status = ctr_prng_init(ctr_prng.rand);

    87     if (status)

    88       return status;

    89   }

    90   ctr_prng.octet_count += len;

    92   /*

    93    * write prng output

    94    */

    95   status = aes_icm_output(&ctr_prng.state, (uint8_t*)dest, len);

    96   if (status)

    97     return status;

    99   return err_status_ok;

   100 }

   102 err_status_t

   103 ctr_prng_deinit(void) {

   105   /* nothing */

   107   return err_status_ok;

   108 }

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