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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 <sys/types.h> | |
28 | #include <sys/wait.h> | |
29 | ||
30 | #ifdef HAVE_SYS_STAT_H | |
31 | # include <sys/stat.h> | |
32 | #endif | |
33 | ||
34 | #ifdef HAVE_FCNTL_H | |
35 | # include <fcntl.h> | |
36 | #endif | |
37 | #include <stdarg.h> | |
38 | #include <string.h> | |
39 | #include <signal.h> | |
40 | #include <unistd.h> | |
41 | ||
42 | #include <openssl/rand.h> | |
43 | #include <openssl/crypto.h> | |
44 | #include <openssl/err.h> | |
45 | ||
46 | #include "ssh.h" | |
47 | #include "misc.h" | |
48 | #include "xmalloc.h" | |
49 | #include "atomicio.h" | |
50 | #include "pathnames.h" | |
51 | #include "log.h" | |
52 | #include "buffer.h" | |
53 | ||
54 | /* | |
55 | * Portable OpenSSH PRNG seeding: | |
56 | * If OpenSSL has not "internally seeded" itself (e.g. pulled data from | |
57 | * /dev/random), then we execute a "ssh-rand-helper" program which | |
58 | * collects entropy and writes it to stdout. The child program must | |
59 | * write at least RANDOM_SEED_SIZE bytes. The child is run with stderr | |
60 | * attached, so error/debugging output should be visible. | |
61 | * | |
62 | * XXX: we should tell the child how many bytes we need. | |
63 | */ | |
64 | ||
65 | #ifndef OPENSSL_PRNG_ONLY | |
66 | #define RANDOM_SEED_SIZE 48 | |
67 | static uid_t original_uid, original_euid; | |
68 | #endif | |
69 | ||
70 | void | |
71 | seed_rng(void) | |
72 | { | |
73 | #ifndef OPENSSL_PRNG_ONLY | |
74 | int devnull; | |
75 | int p[2]; | |
76 | pid_t pid; | |
77 | int ret; | |
78 | unsigned char buf[RANDOM_SEED_SIZE]; | |
79 | mysig_t old_sigchld; | |
80 | ||
81 | if (RAND_status() == 1) { | |
82 | debug3("RNG is ready, skipping seeding"); | |
83 | return; | |
84 | } | |
85 | ||
86 | debug3("Seeding PRNG from %s", SSH_RAND_HELPER); | |
87 | ||
88 | if ((devnull = open("/dev/null", O_RDWR)) == -1) | |
89 | fatal("Couldn't open /dev/null: %s", strerror(errno)); | |
90 | if (pipe(p) == -1) | |
91 | fatal("pipe: %s", strerror(errno)); | |
92 | ||
93 | old_sigchld = signal(SIGCHLD, SIG_DFL); | |
94 | if ((pid = fork()) == -1) | |
95 | fatal("Couldn't fork: %s", strerror(errno)); | |
96 | if (pid == 0) { | |
97 | dup2(devnull, STDIN_FILENO); | |
98 | dup2(p[1], STDOUT_FILENO); | |
99 | /* Keep stderr open for errors */ | |
100 | close(p[0]); | |
101 | close(p[1]); | |
102 | close(devnull); | |
103 | ||
104 | if (original_uid != original_euid && | |
105 | ( seteuid(getuid()) == -1 || | |
106 | setuid(original_uid) == -1) ) { | |
107 | fprintf(stderr, "(rand child) setuid(%li): %s\n", | |
108 | (long int)original_uid, strerror(errno)); | |
109 | _exit(1); | |
110 | } | |
111 | ||
112 | execl(SSH_RAND_HELPER, "ssh-rand-helper", NULL); | |
113 | fprintf(stderr, "(rand child) Couldn't exec '%s': %s\n", | |
114 | SSH_RAND_HELPER, strerror(errno)); | |
115 | _exit(1); | |
116 | } | |
117 | ||
118 | close(devnull); | |
119 | close(p[1]); | |
120 | ||
121 | memset(buf, '\0', sizeof(buf)); | |
122 | ret = atomicio(read, p[0], buf, sizeof(buf)); | |
123 | if (ret == -1) | |
124 | fatal("Couldn't read from ssh-rand-helper: %s", | |
125 | strerror(errno)); | |
126 | if (ret != sizeof(buf)) | |
127 | fatal("ssh-rand-helper child produced insufficient data"); | |
128 | ||
129 | close(p[0]); | |
130 | ||
131 | if (waitpid(pid, &ret, 0) == -1) | |
132 | fatal("Couldn't wait for ssh-rand-helper completion: %s", | |
133 | strerror(errno)); | |
134 | signal(SIGCHLD, old_sigchld); | |
135 | ||
136 | /* We don't mind if the child exits upon a SIGPIPE */ | |
137 | if (!WIFEXITED(ret) && | |
138 | (!WIFSIGNALED(ret) || WTERMSIG(ret) != SIGPIPE)) | |
139 | fatal("ssh-rand-helper terminated abnormally"); | |
140 | if (WEXITSTATUS(ret) != 0) | |
141 | fatal("ssh-rand-helper exit with exit status %d", ret); | |
142 | ||
143 | RAND_add(buf, sizeof(buf), sizeof(buf)); | |
144 | memset(buf, '\0', sizeof(buf)); | |
145 | ||
146 | #endif /* OPENSSL_PRNG_ONLY */ | |
147 | if (RAND_status() != 1) | |
148 | fatal("PRNG is not seeded"); | |
149 | } | |
150 | ||
151 | void | |
152 | init_rng(void) | |
153 | { | |
154 | /* | |
155 | * OpenSSL version numbers: MNNFFPPS: major minor fix patch status | |
156 | * We match major, minor, fix and status (not patch) | |
157 | */ | |
158 | if ((SSLeay() ^ OPENSSL_VERSION_NUMBER) & ~0xff0L) | |
159 | fatal("OpenSSL version mismatch. Built against %lx, you " | |
160 | "have %lx", OPENSSL_VERSION_NUMBER, SSLeay()); | |
161 | ||
162 | #ifndef OPENSSL_PRNG_ONLY | |
163 | original_uid = getuid(); | |
164 | original_euid = geteuid(); | |
165 | #endif | |
166 | } | |
167 | ||
168 | #ifndef OPENSSL_PRNG_ONLY | |
169 | void | |
170 | rexec_send_rng_seed(Buffer *m) | |
171 | { | |
172 | u_char buf[RANDOM_SEED_SIZE]; | |
173 | ||
174 | if (RAND_bytes(buf, sizeof(buf)) <= 0) { | |
175 | error("Couldn't obtain random bytes (error %ld)", | |
176 | ERR_get_error()); | |
177 | buffer_put_string(m, "", 0); | |
178 | } else | |
179 | buffer_put_string(m, buf, sizeof(buf)); | |
180 | } | |
181 | ||
182 | void | |
183 | rexec_recv_rng_seed(Buffer *m) | |
184 | { | |
185 | u_char *buf; | |
186 | u_int len; | |
187 | ||
188 | buf = buffer_get_string_ret(m, &len); | |
189 | if (buf != NULL) { | |
190 | debug3("rexec_recv_rng_seed: seeding rng with %u bytes", len); | |
191 | RAND_add(buf, len, len); | |
192 | } | |
193 | } | |
194 | #endif |