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