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/opensslconf.h>
28 #include <openssl/rand.h>
29 #include <openssl/crypto.h>
30
31 #include "ssh.h"
32 #include "misc.h"
33 #include "xmalloc.h"
34 #include "atomicio.h"
35 #include "pathnames.h"
36 #include "log.h"
37
38 /*
39 * Portable OpenSSH PRNG seeding:
40 * If OpenSSL has not "internally seeded" itself (e.g. pulled data from
41 * /dev/random), then we execute a "ssh-rand-helper" program which
42 * collects entropy and writes it to stdout. The child program must
43 * write at least RANDOM_SEED_SIZE bytes. The child is run with stderr
44 * attached, so error/debugging output should be visible.
45 *
46 * XXX: we should tell the child how many bytes we need.
47 */
48
49 RCSID("$Id: entropy.c,v 1.44 2002/06/09 19:41:48 mouring Exp $");
50
51 #pragma ident "%Z%%M% %I% %E% SMI"
52
53 #ifndef OPENSSL_PRNG_ONLY
54 #define RANDOM_SEED_SIZE 48
55 static uid_t original_uid, original_euid;
56 #endif
57
58 void
59 seed_rng(void)
60 {
61 #ifndef OPENSSL_PRNG_ONLY
62 int devnull;
63 int p[2];
64 pid_t pid;
65 int ret;
66 unsigned char buf[RANDOM_SEED_SIZE];
67 mysig_t old_sigchld;
68
69 if (RAND_status() == 1) {
70 debug3("RNG is ready, skipping seeding");
71 return;
72 }
73
74 debug3("Seeding PRNG from %s", SSH_RAND_HELPER);
75
76 if ((devnull = open("/dev/null", O_RDWR)) == -1)
77 fatal("Couldn't open /dev/null: %s", strerror(errno));
78 if (pipe(p) == -1)
79 fatal("pipe: %s", strerror(errno));
80
81 old_sigchld = mysignal(SIGCHLD, SIG_DFL);
82 if ((pid = fork()) == -1)
83 fatal("Couldn't fork: %s", strerror(errno));
84 if (pid == 0) {
85 dup2(devnull, STDIN_FILENO);
86 dup2(p[1], STDOUT_FILENO);
87 /* Keep stderr open for errors */
88 close(p[0]);
89 close(p[1]);
90 close(devnull);
91
92 if (original_uid != original_euid &&
93 ( seteuid(getuid()) == -1 ||
94 setuid(original_uid) == -1) ) {
95 fprintf(stderr, "(rand child) setuid(%d): %s\n",
96 original_uid, strerror(errno));
97 _exit(1);
98 }
99
100 execl(SSH_RAND_HELPER, "ssh-rand-helper", NULL);
101 fprintf(stderr, "(rand child) Couldn't exec '%s': %s\n",
102 SSH_RAND_HELPER, strerror(errno));
103 _exit(1);
104 }
105
106 close(devnull);
107 close(p[1]);
108
109 memset(buf, '\0', sizeof(buf));
110 ret = atomicio(read, p[0], buf, sizeof(buf));
111 if (ret == -1)
112 fatal("Couldn't read from ssh-rand-helper: %s",
113 strerror(errno));
114 if (ret != sizeof(buf))
115 fatal("ssh-rand-helper child produced insufficient data");
116
117 close(p[0]);
118
119 if (waitpid(pid, &ret, 0) == -1)
120 fatal("Couldn't wait for ssh-rand-helper completion: %s",
121 strerror(errno));
122 mysignal(SIGCHLD, old_sigchld);
123
124 /* We don't mind if the child exits upon a SIGPIPE */
125 if (!WIFEXITED(ret) &&
126 (!WIFSIGNALED(ret) || WTERMSIG(ret) != SIGPIPE))
127 fatal("ssh-rand-helper terminated abnormally");
128 if (WEXITSTATUS(ret) != 0)
129 fatal("ssh-rand-helper exit with exit status %d", ret);
130
131 RAND_add(buf, sizeof(buf), sizeof(buf));
132 memset(buf, '\0', sizeof(buf));
133
134 #endif /* OPENSSL_PRNG_ONLY */
135 if (RAND_status() != 1)
136 fatal("PRNG is not seeded");
137 }
138
139 void
140 init_rng(void)
141 {
142 /*
143 * OpenSSL version numbers: MNNFFPPS: major minor fix patch status
144 * We match major, minor, fix and status (not patch)
145 */
146 if ((SSLeay() ^ OPENSSL_VERSION_NUMBER) & ~0xff0L)
147 fatal("OpenSSL version mismatch. Built against %lx, you "
148 "have %lx", OPENSSL_VERSION_NUMBER, SSLeay());
149
150 #ifndef OPENSSL_PRNG_ONLY
151 if ((original_uid = getuid()) == -1)
152 fatal("getuid: %s", strerror(errno));
153 if ((original_euid = geteuid()) == -1)
154 fatal("geteuid: %s", strerror(errno));
155 #endif
156 }
157