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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 | #include <openssl/err.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 | #include "buffer.h" | |
38 | #include "bufaux.h" | |
39 | ||
40 | /* | |
41 | * Portable OpenSSH PRNG seeding: | |
42 | * If OpenSSL has not "internally seeded" itself (e.g. pulled data from | |
43 | * /dev/random), then we execute a "ssh-rand-helper" program which | |
44 | * collects entropy and writes it to stdout. The child program must | |
45 | * write at least RANDOM_SEED_SIZE bytes. The child is run with stderr | |
46 | * attached, so error/debugging output should be visible. | |
47 | * | |
48 | * XXX: we should tell the child how many bytes we need. | |
49 | */ | |
50 | ||
51 | RCSID("$Id$"); | |
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 = signal(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(%li): %s\n", | |
96 | (long int)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 | signal(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 | original_uid = getuid(); | |
152 | original_euid = geteuid(); | |
153 | #endif | |
154 | } | |
155 | ||
156 | #ifndef OPENSSL_PRNG_ONLY | |
157 | void | |
158 | rexec_send_rng_seed(Buffer *m) | |
159 | { | |
160 | u_char buf[RANDOM_SEED_SIZE]; | |
161 | ||
162 | if (RAND_bytes(buf, sizeof(buf)) <= 0) { | |
163 | error("Couldn't obtain random bytes (error %ld)", | |
164 | ERR_get_error()); | |
165 | buffer_put_string(m, "", 0); | |
166 | } else | |
167 | buffer_put_string(m, buf, sizeof(buf)); | |
168 | } | |
169 | ||
170 | void | |
171 | rexec_recv_rng_seed(Buffer *m) | |
172 | { | |
173 | u_char *buf; | |
174 | u_int len; | |
175 | ||
176 | buf = buffer_get_string_ret(m, &len); | |
177 | if (buf != NULL) { | |
178 | debug3("rexec_recv_rng_seed: seeding rng with %u bytes", len); | |
179 | RAND_add(buf, len, len); | |
180 | } | |
181 | } | |
182 | #endif |