xref: /titanic_50/usr/src/cmd/ssh/libssh/common/entropy.c (revision c5c4113dfcabb1eed3d4bdf7609de5170027a794)
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 
48 RCSID("$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
54 static uid_t original_uid, original_euid;
55 #endif
56 
57 void
58 seed_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 
138 void
139 init_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