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 "sshbuf.h"
57#include "ssherr.h"
58
59/*
60 * Portable OpenSSH PRNG seeding:
61 * If OpenSSL has not "internally seeded" itself (e.g. pulled data from
62 * /dev/random), then collect RANDOM_SEED_SIZE bytes of randomness from
63 * PRNGd.
64 */
65#ifndef OPENSSL_PRNG_ONLY
66
67#define RANDOM_SEED_SIZE 48
68
69/*
70 * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
71 * listening either on 'tcp_port', or via Unix domain socket at *
72 * 'socket_path'.
73 * Either a non-zero tcp_port or a non-null socket_path must be
74 * supplied.
75 * Returns 0 on success, -1 on error
76 */
77int
78get_random_bytes_prngd(unsigned char *buf, int len,
79    unsigned short tcp_port, char *socket_path)
80{
81	int fd, addr_len, rval, errors;
82	u_char msg[2];
83	struct sockaddr_storage addr;
84	struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
85	struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
86	mysig_t old_sigpipe;
87
88	/* Sanity checks */
89	if (socket_path == NULL && tcp_port == 0)
90		fatal("You must specify a port or a socket");
91	if (socket_path != NULL &&
92	    strlen(socket_path) >= sizeof(addr_un->sun_path))
93		fatal("Random pool path is too long");
94	if (len <= 0 || len > 255)
95		fatal("Too many bytes (%d) to read from PRNGD", len);
96
97	memset(&addr, '\0', sizeof(addr));
98
99	if (tcp_port != 0) {
100		addr_in->sin_family = AF_INET;
101		addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
102		addr_in->sin_port = htons(tcp_port);
103		addr_len = sizeof(*addr_in);
104	} else {
105		addr_un->sun_family = AF_UNIX;
106		strlcpy(addr_un->sun_path, socket_path,
107		    sizeof(addr_un->sun_path));
108		addr_len = offsetof(struct sockaddr_un, sun_path) +
109		    strlen(socket_path) + 1;
110	}
111
112	old_sigpipe = signal(SIGPIPE, SIG_IGN);
113
114	errors = 0;
115	rval = -1;
116reopen:
117	fd = socket(addr.ss_family, SOCK_STREAM, 0);
118	if (fd == -1) {
119		error("Couldn't create socket: %s", strerror(errno));
120		goto done;
121	}
122
123	if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
124		if (tcp_port != 0) {
125			error("Couldn't connect to PRNGD port %d: %s",
126			    tcp_port, strerror(errno));
127		} else {
128			error("Couldn't connect to PRNGD socket \"%s\": %s",
129			    addr_un->sun_path, strerror(errno));
130		}
131		goto done;
132	}
133
134	/* Send blocking read request to PRNGD */
135	msg[0] = 0x02;
136	msg[1] = len;
137
138	if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
139		if (errno == EPIPE && errors < 10) {
140			close(fd);
141			errors++;
142			goto reopen;
143		}
144		error("Couldn't write to PRNGD socket: %s",
145		    strerror(errno));
146		goto done;
147	}
148
149	if (atomicio(read, fd, buf, len) != (size_t)len) {
150		if (errno == EPIPE && errors < 10) {
151			close(fd);
152			errors++;
153			goto reopen;
154		}
155		error("Couldn't read from PRNGD socket: %s",
156		    strerror(errno));
157		goto done;
158	}
159
160	rval = 0;
161done:
162	signal(SIGPIPE, old_sigpipe);
163	if (fd != -1)
164		close(fd);
165	return rval;
166}
167
168static int
169seed_from_prngd(unsigned char *buf, size_t bytes)
170{
171#ifdef PRNGD_PORT
172	debug("trying egd/prngd port %d", PRNGD_PORT);
173	if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
174		return 0;
175#endif
176#ifdef PRNGD_SOCKET
177	debug("trying egd/prngd socket %s", PRNGD_SOCKET);
178	if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
179		return 0;
180#endif
181	return -1;
182}
183
184void
185rexec_send_rng_seed(struct sshbuf *m)
186{
187	u_char buf[RANDOM_SEED_SIZE];
188	size_t len = sizeof(buf);
189	int r;
190
191	if (RAND_bytes(buf, sizeof(buf)) <= 0) {
192		error("Couldn't obtain random bytes (error %ld)",
193		    ERR_get_error());
194		len = 0;
195	}
196	if ((r = sshbuf_put_string(m, buf, len)) != 0)
197		fatal("%s: buffer error: %s", __func__, ssh_err(r));
198	explicit_bzero(buf, sizeof(buf));
199}
200
201void
202rexec_recv_rng_seed(struct sshbuf *m)
203{
204	u_char *buf = NULL;
205	size_t len = 0;
206	int r;
207
208	if ((r = sshbuf_get_string_direct(m, &buf, &len)) != 0
209		fatal("%s: buffer error: %s", __func__, ssh_err(r));
210
211	debug3("rexec_recv_rng_seed: seeding rng with %u bytes", len);
212	RAND_add(buf, len, len);
213}
214#endif /* OPENSSL_PRNG_ONLY */
215
216void
217seed_rng(void)
218{
219#ifndef OPENSSL_PRNG_ONLY
220	unsigned char buf[RANDOM_SEED_SIZE];
221#endif
222	if (!ssh_compatible_openssl(OPENSSL_VERSION_NUMBER, SSLeay()))
223		fatal("OpenSSL version mismatch. Built against %lx, you "
224		    "have %lx", (u_long)OPENSSL_VERSION_NUMBER, SSLeay());
225
226#ifndef OPENSSL_PRNG_ONLY
227	if (RAND_status() == 1) {
228		debug3("RNG is ready, skipping seeding");
229		return;
230	}
231
232	if (seed_from_prngd(buf, sizeof(buf)) == -1)
233		fatal("Could not obtain seed from PRNGd");
234	RAND_add(buf, sizeof(buf), sizeof(buf));
235	memset(buf, '\0', sizeof(buf));
236
237#endif /* OPENSSL_PRNG_ONLY */
238	if (RAND_status() != 1)
239		fatal("PRNG is not seeded");
240}
241
242#else /* WITH_OPENSSL */
243
244/* Handled in arc4random() */
245void
246seed_rng(void)
247{
248}
249
250#endif /* WITH_OPENSSL */
251