xref: /freebsd/crypto/openssh/entropy.c (revision a0ee8cc636cd5c2374ec44ca71226564ea0bca95)
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/socket.h>
29 #ifdef HAVE_SYS_UN_H
30 # include <sys/un.h>
31 #endif
32 
33 #include <netinet/in.h>
34 #include <arpa/inet.h>
35 
36 #include <errno.h>
37 #include <signal.h>
38 #include <string.h>
39 #include <unistd.h>
40 #include <stddef.h> /* for offsetof */
41 
42 #include <openssl/rand.h>
43 #include <openssl/crypto.h>
44 #include <openssl/err.h>
45 
46 #include "openbsd-compat/openssl-compat.h"
47 
48 #include "ssh.h"
49 #include "misc.h"
50 #include "xmalloc.h"
51 #include "atomicio.h"
52 #include "pathnames.h"
53 #include "log.h"
54 #include "buffer.h"
55 
56 /*
57  * Portable OpenSSH PRNG seeding:
58  * If OpenSSL has not "internally seeded" itself (e.g. pulled data from
59  * /dev/random), then collect RANDOM_SEED_SIZE bytes of randomness from
60  * PRNGd.
61  */
62 #ifndef OPENSSL_PRNG_ONLY
63 
64 #define RANDOM_SEED_SIZE 48
65 
66 /*
67  * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
68  * listening either on 'tcp_port', or via Unix domain socket at *
69  * 'socket_path'.
70  * Either a non-zero tcp_port or a non-null socket_path must be
71  * supplied.
72  * Returns 0 on success, -1 on error
73  */
74 int
75 get_random_bytes_prngd(unsigned char *buf, int len,
76     unsigned short tcp_port, char *socket_path)
77 {
78 	int fd, addr_len, rval, errors;
79 	u_char msg[2];
80 	struct sockaddr_storage addr;
81 	struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
82 	struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
83 	mysig_t old_sigpipe;
84 
85 	/* Sanity checks */
86 	if (socket_path == NULL && tcp_port == 0)
87 		fatal("You must specify a port or a socket");
88 	if (socket_path != NULL &&
89 	    strlen(socket_path) >= sizeof(addr_un->sun_path))
90 		fatal("Random pool path is too long");
91 	if (len <= 0 || len > 255)
92 		fatal("Too many bytes (%d) to read from PRNGD", len);
93 
94 	memset(&addr, '\0', sizeof(addr));
95 
96 	if (tcp_port != 0) {
97 		addr_in->sin_family = AF_INET;
98 		addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
99 		addr_in->sin_port = htons(tcp_port);
100 		addr_len = sizeof(*addr_in);
101 	} else {
102 		addr_un->sun_family = AF_UNIX;
103 		strlcpy(addr_un->sun_path, socket_path,
104 		    sizeof(addr_un->sun_path));
105 		addr_len = offsetof(struct sockaddr_un, sun_path) +
106 		    strlen(socket_path) + 1;
107 	}
108 
109 	old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
110 
111 	errors = 0;
112 	rval = -1;
113 reopen:
114 	fd = socket(addr.ss_family, SOCK_STREAM, 0);
115 	if (fd == -1) {
116 		error("Couldn't create socket: %s", strerror(errno));
117 		goto done;
118 	}
119 
120 	if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
121 		if (tcp_port != 0) {
122 			error("Couldn't connect to PRNGD port %d: %s",
123 			    tcp_port, strerror(errno));
124 		} else {
125 			error("Couldn't connect to PRNGD socket \"%s\": %s",
126 			    addr_un->sun_path, strerror(errno));
127 		}
128 		goto done;
129 	}
130 
131 	/* Send blocking read request to PRNGD */
132 	msg[0] = 0x02;
133 	msg[1] = len;
134 
135 	if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
136 		if (errno == EPIPE && errors < 10) {
137 			close(fd);
138 			errors++;
139 			goto reopen;
140 		}
141 		error("Couldn't write to PRNGD socket: %s",
142 		    strerror(errno));
143 		goto done;
144 	}
145 
146 	if (atomicio(read, fd, buf, len) != (size_t)len) {
147 		if (errno == EPIPE && errors < 10) {
148 			close(fd);
149 			errors++;
150 			goto reopen;
151 		}
152 		error("Couldn't read from PRNGD socket: %s",
153 		    strerror(errno));
154 		goto done;
155 	}
156 
157 	rval = 0;
158 done:
159 	mysignal(SIGPIPE, old_sigpipe);
160 	if (fd != -1)
161 		close(fd);
162 	return rval;
163 }
164 
165 static int
166 seed_from_prngd(unsigned char *buf, size_t bytes)
167 {
168 #ifdef PRNGD_PORT
169 	debug("trying egd/prngd port %d", PRNGD_PORT);
170 	if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
171 		return 0;
172 #endif
173 #ifdef PRNGD_SOCKET
174 	debug("trying egd/prngd socket %s", PRNGD_SOCKET);
175 	if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
176 		return 0;
177 #endif
178 	return -1;
179 }
180 
181 void
182 rexec_send_rng_seed(Buffer *m)
183 {
184 	u_char buf[RANDOM_SEED_SIZE];
185 
186 	if (RAND_bytes(buf, sizeof(buf)) <= 0) {
187 		error("Couldn't obtain random bytes (error %ld)",
188 		    ERR_get_error());
189 		buffer_put_string(m, "", 0);
190 	} else
191 		buffer_put_string(m, buf, sizeof(buf));
192 }
193 
194 void
195 rexec_recv_rng_seed(Buffer *m)
196 {
197 	u_char *buf;
198 	u_int len;
199 
200 	buf = buffer_get_string_ret(m, &len);
201 	if (buf != NULL) {
202 		debug3("rexec_recv_rng_seed: seeding rng with %u bytes", len);
203 		RAND_add(buf, len, len);
204 	}
205 }
206 #endif /* OPENSSL_PRNG_ONLY */
207 
208 void
209 seed_rng(void)
210 {
211 #ifndef OPENSSL_PRNG_ONLY
212 	unsigned char buf[RANDOM_SEED_SIZE];
213 #endif
214 	if (!ssh_compatible_openssl(OPENSSL_VERSION_NUMBER, SSLeay()))
215 		fatal("OpenSSL version mismatch. Built against %lx, you "
216 		    "have %lx", (u_long)OPENSSL_VERSION_NUMBER, SSLeay());
217 
218 #ifndef OPENSSL_PRNG_ONLY
219 	if (RAND_status() == 1) {
220 		debug3("RNG is ready, skipping seeding");
221 		return;
222 	}
223 
224 	if (seed_from_prngd(buf, sizeof(buf)) == -1)
225 		fatal("Could not obtain seed from PRNGd");
226 	RAND_add(buf, sizeof(buf), sizeof(buf));
227 	memset(buf, '\0', sizeof(buf));
228 
229 #endif /* OPENSSL_PRNG_ONLY */
230 	if (RAND_status() != 1)
231 		fatal("PRNG is not seeded");
232 }
233