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 char buf[1024], seedfile[256]; 44 45 /* If there is a seed file, load it. But such a file cannot be trusted, 46 so use 0 for the entropy estimate */ 47 if (RAND_file_name(seedfile, sizeof(seedfile))) { 48 int fd; 49 fd = open(seedfile, O_RDONLY | O_BINARY | O_CLOEXEC); 50 if (fd >= 0) { 51 ssize_t ret; 52 rk_cloexec(fd); 53 ret = read(fd, buf, sizeof(buf)); 54 if (ret > 0) 55 RAND_add(buf, ret, 0.0); 56 close(fd); 57 } else 58 seedfile[0] = '\0'; 59 } else 60 seedfile[0] = '\0'; 61 62 /* Calling RAND_status() will try to use /dev/urandom if it exists so 63 we do not have to deal with it. */ 64 if (RAND_status() != 1) { 65 #ifndef _WIN32 66 krb5_context context; 67 const char *p; 68 69 /* Try using egd */ 70 if (!krb5_init_context(&context)) { 71 p = krb5_config_get_string(context, NULL, "libdefaults", 72 "egd_socket", NULL); 73 if (p != NULL) 74 RAND_egd_bytes(p, ENTROPY_NEEDED); 75 krb5_free_context(context); 76 } 77 #else 78 /* TODO: Once a Windows CryptoAPI RAND method is defined, we 79 can use that and failover to another method. */ 80 #endif 81 } 82 83 if (RAND_status() == 1) { 84 /* Update the seed file */ 85 if (seedfile[0]) 86 RAND_write_file(seedfile); 87 88 return 0; 89 } else 90 return -1; 91 } 92 93 KRB5_LIB_FUNCTION void KRB5_LIB_CALL 94 krb5_generate_random_block(void *buf, size_t len) 95 { 96 static int rng_initialized = 0; 97 98 HEIMDAL_MUTEX_lock(&crypto_mutex); 99 if (!rng_initialized) { 100 if (seed_something()) 101 krb5_abortx(NULL, "Fatal: could not seed the " 102 "random number generator"); 103 104 rng_initialized = 1; 105 } 106 HEIMDAL_MUTEX_unlock(&crypto_mutex); 107 if (RAND_bytes(buf, len) <= 0) 108 krb5_abortx(NULL, "Failed to generate random block"); 109 } 110