1 /*
2  * Copyright (c) 1996, David Mazieres <dm@uun.org>
3  * Copyright (c) 2008, Damien Miller <djm@openbsd.org>
4  * Copyright (c) 2013, Markus Friedl <markus@openbsd.org>
5  *
6  * Permission to use, copy, modify, and distribute this software for any
7  * purpose with or without fee is hereby granted, provided that the above
8  * copyright notice and this permission notice appear in all copies.
9  *
10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17  */
18 
19 #include "../config.h"
20 
21 #ifndef SSH_RANDOM_DEV
22 # define SSH_RANDOM_DEV "/dev/urandom"
23 #endif /* SSH_RANDOM_DEV */
24 
25 #include <sys/types.h>
26 #ifdef HAVE_SYS_RANDOM_H
27 # include <sys/random.h>
28 #endif
29 
30 #include <errno.h>
31 #include <fcntl.h>
32 #include <stdlib.h>
33 #include <string.h>
34 #include <unistd.h>
35 #ifdef WITH_OPENSSL
36 #include <openssl/rand.h>
37 #include <openssl/err.h>
38 #endif
39 
40 #include "log.h"
41 
42 int _ssh_compat_getentropy(void *, size_t);
43 
44 static int
45 seed_from_prngd(unsigned char *buf, size_t bytes)
46 {
47 	return -1;
48 }
49 
50 int
51 _ssh_compat_getentropy(void *s, size_t len)
52 {
53 #if defined(WITH_OPENSSL) && defined(OPENSSL_PRNG_ONLY)
54 	if (RAND_bytes(s, len) <= 0)
55 		fatal("Couldn't obtain random bytes (error 0x%lx)",
56 		    (unsigned long)ERR_get_error());
57 #else
58 	int fd, save_errno;
59 	ssize_t r;
60 	size_t o = 0;
61 
62 #ifdef WITH_OPENSSL
63 	if (RAND_bytes(s, len) == 1)
64 		return 0;
65 #endif
66 #ifdef HAVE_GETENTROPY
67 	if ((r = getentropy(s, len)) == 0)
68 		return 0;
69 #endif /* HAVE_GETENTROPY */
70 #ifdef HAVE_GETRANDOM
71 	if ((r = getrandom(s, len, 0)) > 0 && (size_t)r == len)
72 		return 0;
73 #endif /* HAVE_GETRANDOM */
74 
75 	if ((fd = open(SSH_RANDOM_DEV, O_RDONLY)) == -1) {
76 		save_errno = errno;
77 		/* Try egd/prngd before giving up. */
78 		if (seed_from_prngd(s, len) == 0)
79 			return 0;
80 		fatal("Couldn't open %s: %s", SSH_RANDOM_DEV,
81 		    strerror(save_errno));
82 	}
83 	while (o < len) {
84 		r = read(fd, (u_char *)s + o, len - o);
85 		if (r < 0) {
86 			if (errno == EAGAIN || errno == EINTR ||
87 			    errno == EWOULDBLOCK)
88 				continue;
89 			fatal("read %s: %s", SSH_RANDOM_DEV, strerror(errno));
90 		}
91 		o += r;
92 	}
93 	close(fd);
94 #endif /* WITH_OPENSSL */
95 	return 0;
96 }