1/*
2 * Copyright (c) 2001 Damien Miller.  All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 */
24
25#include "includes.h"
26
27#include <openssl/rand.h>
28#include <openssl/crypto.h>
29
30#include "ssh.h"
31#include "misc.h"
32#include "xmalloc.h"
33#include "atomicio.h"
34#include "pathnames.h"
35#include "log.h"
36
37/*
38 * Portable OpenSSH PRNG seeding:
39 * If OpenSSL has not "internally seeded" itself (e.g. pulled data from
40 * /dev/random), then we execute a "ssh-rand-helper" program which
41 * collects entropy and writes it to stdout. The child program must
42 * write at least RANDOM_SEED_SIZE bytes. The child is run with stderr
43 * attached, so error/debugging output should be visible.
44 *
45 * XXX: we should tell the child how many bytes we need.
46 */
47
48RCSID("$Id: entropy.c,v 1.44 2002/06/09 19:41:48 mouring Exp $");
49
50#pragma ident	"%Z%%M%	%I%	%E% SMI"
51
52#ifndef OPENSSL_PRNG_ONLY
53#define RANDOM_SEED_SIZE 48
54static uid_t original_uid, original_euid;
55#endif
56
57void
58seed_rng(void)
59{
60#ifndef OPENSSL_PRNG_ONLY
61	int devnull;
62	int p[2];
63	pid_t pid;
64	int ret;
65	unsigned char buf[RANDOM_SEED_SIZE];
66	mysig_t old_sigchld;
67
68	if (RAND_status() == 1) {
69		debug3("RNG is ready, skipping seeding");
70		return;
71	}
72
73	debug3("Seeding PRNG from %s", SSH_RAND_HELPER);
74
75	if ((devnull = open("/dev/null", O_RDWR)) == -1)
76		fatal("Couldn't open /dev/null: %s", strerror(errno));
77	if (pipe(p) == -1)
78		fatal("pipe: %s", strerror(errno));
79
80	old_sigchld = mysignal(SIGCHLD, SIG_DFL);
81	if ((pid = fork()) == -1)
82		fatal("Couldn't fork: %s", strerror(errno));
83	if (pid == 0) {
84		dup2(devnull, STDIN_FILENO);
85		dup2(p[1], STDOUT_FILENO);
86		/* Keep stderr open for errors */
87		close(p[0]);
88		close(p[1]);
89		close(devnull);
90
91		if (original_uid != original_euid &&
92		    ( seteuid(getuid()) == -1 ||
93		      setuid(original_uid) == -1) ) {
94			fprintf(stderr, "(rand child) setuid(%d): %s\n",
95			    original_uid, strerror(errno));
96			_exit(1);
97		}
98
99		execl(SSH_RAND_HELPER, "ssh-rand-helper", NULL);
100		fprintf(stderr, "(rand child) Couldn't exec '%s': %s\n",
101		    SSH_RAND_HELPER, strerror(errno));
102		_exit(1);
103	}
104
105	close(devnull);
106	close(p[1]);
107
108	memset(buf, '\0', sizeof(buf));
109	ret = atomicio(read, p[0], buf, sizeof(buf));
110	if (ret == -1)
111		fatal("Couldn't read from ssh-rand-helper: %s",
112		    strerror(errno));
113	if (ret != sizeof(buf))
114		fatal("ssh-rand-helper child produced insufficient data");
115
116	close(p[0]);
117
118	if (waitpid(pid, &ret, 0) == -1)
119	       fatal("Couldn't wait for ssh-rand-helper completion: %s",
120		   strerror(errno));
121	mysignal(SIGCHLD, old_sigchld);
122
123	/* We don't mind if the child exits upon a SIGPIPE */
124	if (!WIFEXITED(ret) &&
125	    (!WIFSIGNALED(ret) || WTERMSIG(ret) != SIGPIPE))
126		fatal("ssh-rand-helper terminated abnormally");
127	if (WEXITSTATUS(ret) != 0)
128		fatal("ssh-rand-helper exit with exit status %d", ret);
129
130	RAND_add(buf, sizeof(buf), sizeof(buf));
131	memset(buf, '\0', sizeof(buf));
132
133#endif /* OPENSSL_PRNG_ONLY */
134	if (RAND_status() != 1)
135		fatal("PRNG is not seeded");
136}
137
138void
139init_rng(void)
140{
141	/*
142	 * OpenSSL version numbers: MNNFFPPS: major minor fix patch status
143	 * We match major, minor, fix and status (not patch)
144	 */
145	if ((SSLeay() ^ OPENSSL_VERSION_NUMBER) & ~0xff0L)
146		fatal("OpenSSL version mismatch. Built against %lx, you "
147		    "have %lx", OPENSSL_VERSION_NUMBER, SSLeay());
148
149#ifndef OPENSSL_PRNG_ONLY
150	if ((original_uid = getuid()) == -1)
151		fatal("getuid: %s", strerror(errno));
152	if ((original_euid = geteuid()) == -1)
153		fatal("geteuid: %s", strerror(errno));
154#endif
155}
156
157