crypto/external/bsd/heimdal/dist/lib/krb5/crypto-rand.c

   1 /*      $NetBSD: crypto-rand.c,v 1.1.1.1 2011/04/13 18:15:32 elric Exp $        */
   2
   3 /*
   4  * Copyright (c) 1997 - 2008 Kungliga Tekniska Högskolan
   5  * (Royal Institute of Technology, Stockholm, Sweden).
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  *
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  *
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * 3. Neither the name of the Institute nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  */
  35
  36 #include "krb5_locl.h"
  37
  38 #define ENTROPY_NEEDED 128
  39
  40 static HEIMDAL_MUTEX crypto_mutex = HEIMDAL_MUTEX_INITIALIZER;
  41
  42 static int
  43 seed_something(void)
  44 {
  45     char buf[1024], seedfile[256];
  46
  47     /* If there is a seed file, load it. But such a file cannot be trusted,
  48        so use 0 for the entropy estimate */
  49     if (RAND_file_name(seedfile, sizeof(seedfile))) {
  50         int fd;
  51         fd = open(seedfile, O_RDONLY | O_BINARY | O_CLOEXEC);
  52         if (fd >= 0) {
  53             ssize_t ret;
  54             rk_cloexec(fd);
  55             ret = read(fd, buf, sizeof(buf));
  56             if (ret > 0)
  57                 RAND_add(buf, ret, 0.0);
  58             close(fd);
  59         } else
  60             seedfile[0] = '\0';
  61     } else
  62         seedfile[0] = '\0';
  63
  64     /* Calling RAND_status() will try to use /dev/urandom if it exists so
  65        we do not have to deal with it. */
  66     if (RAND_status() != 1) {
  67 #ifndef _WIN32
  68         krb5_context context;
  69         const char *p;
  70
  71         /* Try using egd */
  72         if (!krb5_init_context(&context)) {
  73             p = krb5_config_get_string(context, NULL, "libdefaults",
  74                                        "egd_socket", NULL);
  75             if (p != NULL)
  76                 RAND_egd_bytes(p, ENTROPY_NEEDED);
  77             krb5_free_context(context);
  78         }
  79 #else
  80         /* TODO: Once a Windows CryptoAPI RAND method is defined, we
  81            can use that and failover to another method. */
  82 #endif
  83     }
  84
  85     if (RAND_status() == 1)     {
  86         /* Update the seed file */
  87         if (seedfile[0])
  88             RAND_write_file(seedfile);
  89
  90         return 0;
  91     } else
  92         return -1;
  93 }
  94
  95 KRB5_LIB_FUNCTION void KRB5_LIB_CALL
  96 krb5_generate_random_block(void *buf, size_t len)
  97 {
  98     static int rng_initialized = 0;
  99
 100     HEIMDAL_MUTEX_lock(&crypto_mutex);
 101     if (!rng_initialized) {
 102         if (seed_something())
 103             krb5_abortx(NULL, "Fatal: could not seed the "
 104                         "random number generator");
 105
 106         rng_initialized = 1;
 107     }
 108     HEIMDAL_MUTEX_unlock(&crypto_mutex);
 109     if (RAND_bytes(buf, len) <= 0)
 110         krb5_abortx(NULL, "Failed to generate random block");
 111 }