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 "ssh.h"
47#include "misc.h"
48#include "xmalloc.h"
49#include "atomicio.h"
50#include "pathnames.h"
51#include "log.h"
52#include "buffer.h"
53
54/*
55 * Portable OpenSSH PRNG seeding:
56 * If OpenSSL has not "internally seeded" itself (e.g. pulled data from
57 * /dev/random), then collect RANDOM_SEED_SIZE bytes of randomness from
58 * PRNGd.
59 */
60#ifndef OPENSSL_PRNG_ONLY
61
62#define RANDOM_SEED_SIZE 48
63
64/*
65 * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
66 * listening either on 'tcp_port', or via Unix domain socket at *
67 * 'socket_path'.
68 * Either a non-zero tcp_port or a non-null socket_path must be
69 * supplied.
70 * Returns 0 on success, -1 on error
71 */
72int
73get_random_bytes_prngd(unsigned char *buf, int len,
74    unsigned short tcp_port, char *socket_path)
75{
76	int fd, addr_len, rval, errors;
77	u_char msg[2];
78	struct sockaddr_storage addr;
79	struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
80	struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
81	mysig_t old_sigpipe;
82
83	/* Sanity checks */
84	if (socket_path == NULL && tcp_port == 0)
85		fatal("You must specify a port or a socket");
86	if (socket_path != NULL &&
87	    strlen(socket_path) >= sizeof(addr_un->sun_path))
88		fatal("Random pool path is too long");
89	if (len <= 0 || len > 255)
90		fatal("Too many bytes (%d) to read from PRNGD", len);
91
92	memset(&addr, '\0', sizeof(addr));
93
94	if (tcp_port != 0) {
95		addr_in->sin_family = AF_INET;
96		addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
97		addr_in->sin_port = htons(tcp_port);
98		addr_len = sizeof(*addr_in);
99	} else {
100		addr_un->sun_family = AF_UNIX;
101		strlcpy(addr_un->sun_path, socket_path,
102		    sizeof(addr_un->sun_path));
103		addr_len = offsetof(struct sockaddr_un, sun_path) +
104		    strlen(socket_path) + 1;
105	}
106
107	old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
108
109	errors = 0;
110	rval = -1;
111reopen:
112	fd = socket(addr.ss_family, SOCK_STREAM, 0);
113	if (fd == -1) {
114		error("Couldn't create socket: %s", strerror(errno));
115		goto done;
116	}
117
118	if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
119		if (tcp_port != 0) {
120			error("Couldn't connect to PRNGD port %d: %s",
121			    tcp_port, strerror(errno));
122		} else {
123			error("Couldn't connect to PRNGD socket \"%s\": %s",
124			    addr_un->sun_path, strerror(errno));
125		}
126		goto done;
127	}
128
129	/* Send blocking read request to PRNGD */
130	msg[0] = 0x02;
131	msg[1] = len;
132
133	if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
134		if (errno == EPIPE && errors < 10) {
135			close(fd);
136			errors++;
137			goto reopen;
138		}
139		error("Couldn't write to PRNGD socket: %s",
140		    strerror(errno));
141		goto done;
142	}
143
144	if (atomicio(read, fd, buf, len) != (size_t)len) {
145		if (errno == EPIPE && errors < 10) {
146			close(fd);
147			errors++;
148			goto reopen;
149		}
150		error("Couldn't read from PRNGD socket: %s",
151		    strerror(errno));
152		goto done;
153	}
154
155	rval = 0;
156done:
157	mysignal(SIGPIPE, old_sigpipe);
158	if (fd != -1)
159		close(fd);
160	return rval;
161}
162
163static int
164seed_from_prngd(unsigned char *buf, size_t bytes)
165{
166#ifdef PRNGD_PORT
167	debug("trying egd/prngd port %d", PRNGD_PORT);
168	if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
169		return 0;
170#endif
171#ifdef PRNGD_SOCKET
172	debug("trying egd/prngd socket %s", PRNGD_SOCKET);
173	if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
174		return 0;
175#endif
176	return -1;
177}
178
179void
180rexec_send_rng_seed(Buffer *m)
181{
182	u_char buf[RANDOM_SEED_SIZE];
183
184	if (RAND_bytes(buf, sizeof(buf)) <= 0) {
185		error("Couldn't obtain random bytes (error %ld)",
186		    ERR_get_error());
187		buffer_put_string(m, "", 0);
188	} else
189		buffer_put_string(m, buf, sizeof(buf));
190}
191
192void
193rexec_recv_rng_seed(Buffer *m)
194{
195	u_char *buf;
196	u_int len;
197
198	buf = buffer_get_string_ret(m, &len);
199	if (buf != NULL) {
200		debug3("rexec_recv_rng_seed: seeding rng with %u bytes", len);
201		RAND_add(buf, len, len);
202	}
203}
204#endif /* OPENSSL_PRNG_ONLY */
205
206void
207seed_rng(void)
208{
209#ifndef OPENSSL_PRNG_ONLY
210	unsigned char buf[RANDOM_SEED_SIZE];
211#endif
212	/*
213	 * OpenSSL version numbers: MNNFFPPS: major minor fix patch status
214	 * We match major, minor, fix and status (not patch) for <1.0.0.
215	 * After that, we acceptable compatible fix versions (so we
216	 * allow 1.0.1 to work with 1.0.0). Going backwards is only allowed
217	 * within a patch series.
218	 */
219	u_long version_mask = SSLeay() >= 0x1000000f ?  ~0xffff0L : ~0xff0L;
220	if (((SSLeay() ^ OPENSSL_VERSION_NUMBER) & version_mask) ||
221	    (SSLeay() >> 12) < (OPENSSL_VERSION_NUMBER >> 12))
222		fatal("OpenSSL version mismatch. Built against %lx, you "
223		    "have %lx", (u_long)OPENSSL_VERSION_NUMBER, SSLeay());
224
225#ifndef OPENSSL_PRNG_ONLY
226	if (RAND_status() == 1) {
227		debug3("RNG is ready, skipping seeding");
228		return;
229	}
230
231	if (seed_from_prngd(buf, sizeof(buf)) == -1)
232		fatal("Could not obtain seed from PRNGd");
233	RAND_add(buf, sizeof(buf), sizeof(buf));
234	memset(buf, '\0', sizeof(buf));
235
236#endif /* OPENSSL_PRNG_ONLY */
237	if (RAND_status() != 1)
238		fatal("PRNG is not seeded");
239}
240