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Damien Miller040f3832000-04-03 14:50:43 +10001/*
Damien Miller62116dc2001-12-24 01:41:47 +11002 * Copyright (c) 2001 Damien Miller. All rights reserved.
Damien Miller040f3832000-04-03 14:50:43 +10003 *
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.
Damien Miller040f3832000-04-03 14:50:43 +100012 *
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
Damien Miller5f056372000-04-16 12:31:48 +100027#include <openssl/rand.h>
Damien Miller767c7fc2001-02-27 09:20:57 +110028#include <openssl/crypto.h>
Damien Miller040f3832000-04-03 14:50:43 +100029
Ben Lindstrom226cfa02001-01-22 05:34:40 +000030#include "ssh.h"
Damien Millera1072a82001-02-18 15:28:11 +110031#include "misc.h"
Ben Lindstrom226cfa02001-01-22 05:34:40 +000032#include "xmalloc.h"
33#include "atomicio.h"
Ben Lindstromcb577332001-01-22 21:06:19 +000034#include "pathnames.h"
Ben Lindstrom226cfa02001-01-22 05:34:40 +000035#include "log.h"
36
Damien Miller14c12cb2000-06-07 22:20:23 +100037/*
Damien Miller62116dc2001-12-24 01:41:47 +110038 * 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.
Damien Miller14c12cb2000-06-07 22:20:23 +100046 */
Damien Miller62116dc2001-12-24 01:41:47 +110047
Damien Millerc46b6bc2003-05-16 15:51:44 +100048RCSID("$Id: entropy.c,v 1.45 2003/05/16 05:51:45 djm Exp $");
Damien Miller6c21c512002-01-22 21:57:53 +110049
50#ifndef OPENSSL_PRNG_ONLY
Damien Miller62116dc2001-12-24 01:41:47 +110051#define RANDOM_SEED_SIZE 48
Damien Miller62116dc2001-12-24 01:41:47 +110052static uid_t original_uid, original_euid;
Damien Miller6c21c512002-01-22 21:57:53 +110053#endif
Damien Miller62116dc2001-12-24 01:41:47 +110054
Damien Miller14c12cb2000-06-07 22:20:23 +100055void
56seed_rng(void)
57{
Damien Miller6c21c512002-01-22 21:57:53 +110058#ifndef OPENSSL_PRNG_ONLY
Damien Miller62116dc2001-12-24 01:41:47 +110059 int devnull;
60 int p[2];
61 pid_t pid;
62 int ret;
63 unsigned char buf[RANDOM_SEED_SIZE];
Damien Millera370f4d2002-04-18 22:53:22 +100064 mysig_t old_sigchld;
Kevin Stevesef4eea92001-02-05 12:42:17 +000065
Damien Miller62116dc2001-12-24 01:41:47 +110066 if (RAND_status() == 1) {
67 debug3("RNG is ready, skipping seeding");
68 return;
Damien Miller08006472000-06-26 13:55:31 +100069 }
Kevin Stevesef4eea92001-02-05 12:42:17 +000070
Kevin Steves58193072002-03-11 00:16:34 +000071 debug3("Seeding PRNG from %s", SSH_RAND_HELPER);
Damien Miller62116dc2001-12-24 01:41:47 +110072
73 if ((devnull = open("/dev/null", O_RDWR)) == -1)
74 fatal("Couldn't open /dev/null: %s", strerror(errno));
75 if (pipe(p) == -1)
76 fatal("pipe: %s", strerror(errno));
77
Damien Millera370f4d2002-04-18 22:53:22 +100078 old_sigchld = mysignal(SIGCHLD, SIG_DFL);
Damien Miller62116dc2001-12-24 01:41:47 +110079 if ((pid = fork()) == -1)
80 fatal("Couldn't fork: %s", strerror(errno));
81 if (pid == 0) {
82 dup2(devnull, STDIN_FILENO);
83 dup2(p[1], STDOUT_FILENO);
84 /* Keep stderr open for errors */
85 close(p[0]);
86 close(p[1]);
87 close(devnull);
88
89 if (original_uid != original_euid &&
Tim Ricef02dccc2002-04-21 11:26:10 -070090 ( seteuid(getuid()) == -1 ||
91 setuid(original_uid) == -1) ) {
Damien Millerc46b6bc2003-05-16 15:51:44 +100092 fprintf(stderr, "(rand child) setuid(%li): %s\n",
93 (long int)original_uid, strerror(errno));
Damien Miller62116dc2001-12-24 01:41:47 +110094 _exit(1);
95 }
96
97 execl(SSH_RAND_HELPER, "ssh-rand-helper", NULL);
98 fprintf(stderr, "(rand child) Couldn't exec '%s': %s\n",
99 SSH_RAND_HELPER, strerror(errno));
100 _exit(1);
101 }
102
103 close(devnull);
104 close(p[1]);
105
106 memset(buf, '\0', sizeof(buf));
107 ret = atomicio(read, p[0], buf, sizeof(buf));
108 if (ret == -1)
109 fatal("Couldn't read from ssh-rand-helper: %s",
110 strerror(errno));
111 if (ret != sizeof(buf))
112 fatal("ssh-rand-helper child produced insufficient data");
113
114 close(p[0]);
115
116 if (waitpid(pid, &ret, 0) == -1)
117 fatal("Couldn't wait for ssh-rand-helper completion: %s",
Ben Lindstrom5a6abda2002-06-09 19:41:48 +0000118 strerror(errno));
Damien Millera370f4d2002-04-18 22:53:22 +1000119 mysignal(SIGCHLD, old_sigchld);
Damien Miller62116dc2001-12-24 01:41:47 +1100120
121 /* We don't mind if the child exits upon a SIGPIPE */
122 if (!WIFEXITED(ret) &&
123 (!WIFSIGNALED(ret) || WTERMSIG(ret) != SIGPIPE))
124 fatal("ssh-rand-helper terminated abnormally");
125 if (WEXITSTATUS(ret) != 0)
126 fatal("ssh-rand-helper exit with exit status %d", ret);
127
128 RAND_add(buf, sizeof(buf), sizeof(buf));
Damien Miller14c12cb2000-06-07 22:20:23 +1000129 memset(buf, '\0', sizeof(buf));
Damien Miller6c21c512002-01-22 21:57:53 +1100130
131#endif /* OPENSSL_PRNG_ONLY */
132 if (RAND_status() != 1)
133 fatal("PRNG is not seeded");
Damien Miller14c12cb2000-06-07 22:20:23 +1000134}
135
Damien Miller60bc5172001-03-19 09:38:15 +1100136void
137init_rng(void)
Damien Miller767c7fc2001-02-27 09:20:57 +1100138{
Damien Millerbb7c9762001-02-26 20:49:58 +1100139 /*
Damien Miller62116dc2001-12-24 01:41:47 +1100140 * OpenSSL version numbers: MNNFFPPS: major minor fix patch status
141 * We match major, minor, fix and status (not patch)
Damien Millerbb7c9762001-02-26 20:49:58 +1100142 */
Damien Miller62116dc2001-12-24 01:41:47 +1100143 if ((SSLeay() ^ OPENSSL_VERSION_NUMBER) & ~0xff0L)
144 fatal("OpenSSL version mismatch. Built against %lx, you "
145 "have %lx", OPENSSL_VERSION_NUMBER, SSLeay());
Kevin Stevesef4eea92001-02-05 12:42:17 +0000146
Damien Miller6c21c512002-01-22 21:57:53 +1100147#ifndef OPENSSL_PRNG_ONLY
Damien Miller62116dc2001-12-24 01:41:47 +1100148 if ((original_uid = getuid()) == -1)
149 fatal("getuid: %s", strerror(errno));
150 if ((original_euid = geteuid()) == -1)
151 fatal("geteuid: %s", strerror(errno));
Damien Miller6c21c512002-01-22 21:57:53 +1100152#endif
Damien Millerf9b625c2000-07-09 22:42:32 +1000153}
Damien Miller6c21c512002-01-22 21:57:53 +1100154