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#ifdef __APPLE__
37KRB5_LIB_FUNCTION void KRB5_LIB_CALL
38krb5_generate_random_block(void *buf, size_t len)
39{
40    CCRandomCopyBytes(kCCRandomDefault, buf, len);
41}
42#else
43
44#define ENTROPY_NEEDED 128
45
46static HEIMDAL_MUTEX crypto_mutex = HEIMDAL_MUTEX_INITIALIZER;
47
48static int
49seed_something(void)
50{
51    char buf[1024], seedfile[256];
52
53    /* If there is a seed file, load it. But such a file cannot be trusted,
54       so use 0 for the entropy estimate */
55
56    if (krb5_homedir_access(NULL) && RAND_file_name(seedfile, sizeof(seedfile))) {
57	int fd;
58	fd = open(seedfile, O_RDONLY | O_BINARY | O_CLOEXEC);
59	if (fd >= 0) {
60	    ssize_t ret;
61	    rk_cloexec(fd);
62	    ret = read(fd, buf, sizeof(buf));
63	    if (ret > 0)
64		RAND_add(buf, ret, 0.0);
65	    close(fd);
66	} else
67	    seedfile[0] = '\0';
68    } else
69	seedfile[0] = '\0';
70
71    /* Calling RAND_status() will try to use /dev/urandom if it exists so
72       we do not have to deal with it. */
73    if (RAND_status() != 1) {
74#ifndef _WIN32
75	krb5_context context;
76	const char *p;
77
78	/* Try using egd */
79	if (!krb5_init_context(&context)) {
80	    p = krb5_config_get_string(context, NULL, "libdefaults",
81				       "egd_socket", NULL);
82	    if (p != NULL)
83		RAND_egd_bytes(p, ENTROPY_NEEDED);
84	    krb5_free_context(context);
85	}
86#else
87	/* TODO: Once a Windows CryptoAPI RAND method is defined, we
88	   can use that and failover to another method. */
89#endif
90    }
91
92    if (RAND_status() == 1)	{
93	/* Update the seed file */
94	if (seedfile[0])
95	    RAND_write_file(seedfile);
96
97	return 0;
98    } else
99	return -1;
100}
101
102KRB5_LIB_FUNCTION void KRB5_LIB_CALL
103krb5_generate_random_block(void *buf, size_t len)
104{
105    static int rng_initialized = 0;
106
107    HEIMDAL_MUTEX_lock(&crypto_mutex);
108    if (!rng_initialized) {
109	if (seed_something())
110	    krb5_abortx(NULL, "Fatal: could not seed the "
111			"random number generator");
112
113	rng_initialized = 1;
114    }
115    HEIMDAL_MUTEX_unlock(&crypto_mutex);
116    if (RAND_bytes(buf, len) <= 0)
117	krb5_abortx(NULL, "Failed to generate random block");
118}
119
120#endif /* __APPLE__ */
121