src/external/heimdal/krb5/crypto-rand.c

   1 /*
   2  * Copyright (c) 1997 - 2008 Kungliga Tekniska Högskolan
   3  * (Royal Institute of Technology, Stockholm, Sweden).
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * 3. Neither the name of the Institute nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #include "krb5_locl.h"
  35
  36 #define ENTROPY_NEEDED 128
  37
  38 static HEIMDAL_MUTEX crypto_mutex = HEIMDAL_MUTEX_INITIALIZER;
  39
  40 static int
  41 seed_something(void)
  42 {
  43 #ifndef NO_RANDFILE
  44     char buf[1024], seedfile[256];
  45
  46     /* If there is a seed file, load it. But such a file cannot be trusted,
  47        so use 0 for the entropy estimate */
  48     if (RAND_file_name(seedfile, sizeof(seedfile))) {
  49         int fd;
  50         fd = open(seedfile, O_RDONLY | O_BINARY | O_CLOEXEC);
  51         if (fd >= 0) {
  52             ssize_t ret;
  53             rk_cloexec(fd);
  54             ret = read(fd, buf, sizeof(buf));
  55             if (ret > 0)
  56                 RAND_add(buf, ret, 0.0);
  57             close(fd);
  58         } else
  59             seedfile[0] = '\0';
  60     } else
  61         seedfile[0] = '\0';
  62 #endif
  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 NO_RAND_EGD_METHOD
  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 #ifndef NO_RANDFILE
  87         /* Update the seed file */
  88         if (seedfile[0])
  89             RAND_write_file(seedfile);
  90 #endif
  91
  92         return 0;
  93     } else
  94         return -1;
  95 }
  96
  97 KRB5_LIB_FUNCTION void KRB5_LIB_CALL
  98 krb5_generate_random_block(void *buf, size_t len)
  99 {
 100     static int rng_initialized = 0;
 101
 102     HEIMDAL_MUTEX_lock(&crypto_mutex);
 103     if (!rng_initialized) {
 104         if (seed_something())
 105             krb5_abortx(NULL, "Fatal: could not seed the "
 106                         "random number generator");
 107
 108         rng_initialized = 1;
 109     }
 110     HEIMDAL_MUTEX_unlock(&crypto_mutex);
 111     if (RAND_bytes(buf, len) <= 0)
 112         krb5_abortx(NULL, "Failed to generate random block");
 113 }