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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 #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