entropy.c revision 295367 
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 */
76int
77get_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;
115reopen:
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;
160done:
161	mysignal(SIGPIPE, old_sigpipe);
162	if (fd != -1)
163		close(fd);
164	return rval;
165}
166
167static int
168seed_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
183void
184rexec_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
196void
197rexec_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
210void
211seed_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() */
239void
240seed_rng(void)
241{
242}
243
244#endif /* WITH_OPENSSL */
245