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