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 #define RANDOM_SEED_SIZE 48
28
29 #ifdef WITH_OPENSSL
30
31 #include <sys/types.h>
32 #include <sys/socket.h>
33 #ifdef HAVE_SYS_UN_H
34 # include <sys/un.h>
35 #endif
36
37 #include <netinet/in.h>
38 #include <arpa/inet.h>
39
40 #include <errno.h>
41 #include <signal.h>
42 #include <stdlib.h>
43 #include <string.h>
44 #include <unistd.h>
45 #include <stddef.h> /* for offsetof */
46
47 #include <openssl/rand.h>
48 #include <openssl/crypto.h>
49 #include <openssl/err.h>
50
51 #include "openbsd-compat/openssl-compat.h"
52
53 #include "ssh.h"
54 #include "misc.h"
55 #include "xmalloc.h"
56 #include "atomicio.h"
57 #include "pathnames.h"
58 #include "log.h"
59 #include "sshbuf.h"
60 #include "ssherr.h"
61
62 /*
63 * Portable OpenSSH PRNG seeding:
64 * If OpenSSL has not "internally seeded" itself (e.g. pulled data from
65 * /dev/random), then collect RANDOM_SEED_SIZE bytes of randomness from
66 * PRNGd.
67 */
68 #ifndef OPENSSL_PRNG_ONLY
69
70 /*
71 * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
72 * listening either on 'tcp_port', or via Unix domain socket at *
73 * 'socket_path'.
74 * Either a non-zero tcp_port or a non-null socket_path must be
75 * supplied.
76 * Returns 0 on success, -1 on error
77 */
78 int
get_random_bytes_prngd(unsigned char * buf,int len,unsigned short tcp_port,char * socket_path)79 get_random_bytes_prngd(unsigned char *buf, int len,
80 unsigned short tcp_port, char *socket_path)
81 {
82 int fd, addr_len, rval, errors;
83 u_char msg[2];
84 struct sockaddr_storage addr;
85 struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
86 struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
87 sshsig_t old_sigpipe;
88
89 /* Sanity checks */
90 if (socket_path == NULL && tcp_port == 0)
91 fatal("You must specify a port or a socket");
92 if (socket_path != NULL &&
93 strlen(socket_path) >= sizeof(addr_un->sun_path))
94 fatal("Random pool path is too long");
95 if (len <= 0 || len > 255)
96 fatal("Too many bytes (%d) to read from PRNGD", len);
97
98 memset(&addr, '\0', sizeof(addr));
99
100 if (tcp_port != 0) {
101 addr_in->sin_family = AF_INET;
102 addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
103 addr_in->sin_port = htons(tcp_port);
104 addr_len = sizeof(*addr_in);
105 } else {
106 addr_un->sun_family = AF_UNIX;
107 strlcpy(addr_un->sun_path, socket_path,
108 sizeof(addr_un->sun_path));
109 addr_len = offsetof(struct sockaddr_un, sun_path) +
110 strlen(socket_path) + 1;
111 }
112
113 old_sigpipe = ssh_signal(SIGPIPE, SIG_IGN);
114
115 errors = 0;
116 rval = -1;
117 reopen:
118 fd = socket(addr.ss_family, SOCK_STREAM, 0);
119 if (fd == -1) {
120 error("Couldn't create socket: %s", strerror(errno));
121 goto done;
122 }
123
124 if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
125 if (tcp_port != 0) {
126 error("Couldn't connect to PRNGD port %d: %s",
127 tcp_port, strerror(errno));
128 } else {
129 error("Couldn't connect to PRNGD socket \"%s\": %s",
130 addr_un->sun_path, strerror(errno));
131 }
132 goto done;
133 }
134
135 /* Send blocking read request to PRNGD */
136 msg[0] = 0x02;
137 msg[1] = len;
138
139 if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
140 if (errno == EPIPE && errors < 10) {
141 close(fd);
142 errors++;
143 goto reopen;
144 }
145 error("Couldn't write to PRNGD socket: %s",
146 strerror(errno));
147 goto done;
148 }
149
150 if (atomicio(read, fd, buf, len) != (size_t)len) {
151 if (errno == EPIPE && errors < 10) {
152 close(fd);
153 errors++;
154 goto reopen;
155 }
156 error("Couldn't read from PRNGD socket: %s",
157 strerror(errno));
158 goto done;
159 }
160
161 rval = 0;
162 done:
163 ssh_signal(SIGPIPE, old_sigpipe);
164 if (fd != -1)
165 close(fd);
166 return rval;
167 }
168
169 static int
seed_from_prngd(unsigned char * buf,size_t bytes)170 seed_from_prngd(unsigned char *buf, size_t bytes)
171 {
172 #ifdef PRNGD_PORT
173 debug("trying egd/prngd port %d", PRNGD_PORT);
174 if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
175 return 0;
176 #endif
177 #ifdef PRNGD_SOCKET
178 debug("trying egd/prngd socket %s", PRNGD_SOCKET);
179 if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
180 return 0;
181 #endif
182 return -1;
183 }
184
185 void
rexec_send_rng_seed(struct sshbuf * m)186 rexec_send_rng_seed(struct sshbuf *m)
187 {
188 u_char buf[RANDOM_SEED_SIZE];
189 size_t len = sizeof(buf);
190 int r;
191
192 if (RAND_bytes(buf, sizeof(buf)) <= 0) {
193 error("Couldn't obtain random bytes (error %ld)",
194 ERR_get_error());
195 len = 0;
196 }
197 if ((r = sshbuf_put_string(m, buf, len)) != 0)
198 fatal("%s: buffer error: %s", __func__, ssh_err(r));
199 explicit_bzero(buf, sizeof(buf));
200 }
201
202 void
rexec_recv_rng_seed(struct sshbuf * m)203 rexec_recv_rng_seed(struct sshbuf *m)
204 {
205 const u_char *buf = NULL;
206 size_t len = 0;
207 int r;
208
209 if ((r = sshbuf_get_string_direct(m, &buf, &len)) != 0)
210 fatal("%s: buffer error: %s", __func__, ssh_err(r));
211
212 debug3("rexec_recv_rng_seed: seeding rng with %lu bytes",
213 (unsigned long)len);
214 RAND_add(buf, len, len);
215 }
216 #endif /* OPENSSL_PRNG_ONLY */
217
218 void
seed_rng(void)219 seed_rng(void)
220 {
221 unsigned char buf[RANDOM_SEED_SIZE];
222
223 /* Initialise libcrypto */
224 ssh_libcrypto_init();
225
226 if (!ssh_compatible_openssl(OPENSSL_VERSION_NUMBER,
227 OpenSSL_version_num()))
228 fatal("OpenSSL version mismatch. Built against %lx, you "
229 "have %lx", (u_long)OPENSSL_VERSION_NUMBER,
230 OpenSSL_version_num());
231
232 #ifndef OPENSSL_PRNG_ONLY
233 if (RAND_status() == 1)
234 debug3("RNG is ready, skipping seeding");
235 else {
236 if (seed_from_prngd(buf, sizeof(buf)) == -1)
237 fatal("Could not obtain seed from PRNGd");
238 RAND_add(buf, sizeof(buf), sizeof(buf));
239 }
240 #endif /* OPENSSL_PRNG_ONLY */
241
242 if (RAND_status() != 1)
243 fatal("PRNG is not seeded");
244
245 /* Ensure arc4random() is primed */
246 arc4random_buf(buf, sizeof(buf));
247 explicit_bzero(buf, sizeof(buf));
248 }
249
250 #else /* WITH_OPENSSL */
251
252 #include <stdlib.h>
253 #include <string.h>
254
255 /* Actual initialisation is handled in arc4random() */
256 void
seed_rng(void)257 seed_rng(void)
258 {
259 unsigned char buf[RANDOM_SEED_SIZE];
260
261 /* Ensure arc4random() is primed */
262 arc4random_buf(buf, sizeof(buf));
263 explicit_bzero(buf, sizeof(buf));
264 }
265
266 #endif /* WITH_OPENSSL */
267