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