1 /*
2  * Copyright (c) 2005 Reyk Floeter <reyk@openbsd.org>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include "includes.h"
18 
19 #include <sys/types.h>
20 #include <sys/ioctl.h>
21 
22 #include <netinet/in.h>
23 #include <arpa/inet.h>
24 #include <netinet/ip.h>
25 
26 #include <errno.h>
27 #include <fcntl.h>
28 #include <stdarg.h>
29 #include <string.h>
30 #include <unistd.h>
31 
32 #include "openbsd-compat/sys-queue.h"
33 #include "log.h"
34 #include "misc.h"
35 #include "sshbuf.h"
36 #include "channels.h"
37 #include "ssherr.h"
38 
39 /*
40  * This file contains various portability code for network support,
41  * including tun/tap forwarding and routing domains.
42  */
43 
44 #if defined(SYS_RDOMAIN_LINUX) || defined(SSH_TUN_LINUX)
45 #include <linux/if.h>
46 #endif
47 
48 #if defined(SYS_RDOMAIN_LINUX)
49 char *
sys_get_rdomain(int fd)50 sys_get_rdomain(int fd)
51 {
52 	char dev[IFNAMSIZ + 1];
53 	socklen_t len = sizeof(dev) - 1;
54 
55 	if (getsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE, dev, &len) == -1) {
56 		error("%s: cannot determine VRF for fd=%d : %s",
57 		    __func__, fd, strerror(errno));
58 		return NULL;
59 	}
60 	dev[len] = '\0';
61 	return strdup(dev);
62 }
63 
64 int
sys_set_rdomain(int fd,const char * name)65 sys_set_rdomain(int fd, const char *name)
66 {
67 	if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE,
68 	    name, strlen(name)) == -1) {
69 		error("%s: setsockopt(%d, SO_BINDTODEVICE, %s): %s",
70 		      __func__, fd, name, strerror(errno));
71 		return -1;
72 	}
73 	return 0;
74 }
75 
76 int
sys_valid_rdomain(const char * name)77 sys_valid_rdomain(const char *name)
78 {
79 	int fd;
80 
81 	/*
82 	 * This is a pretty crappy way to test. It would be better to
83 	 * check whether "name" represents a VRF device, but apparently
84 	 * that requires an rtnetlink transaction.
85 	 */
86 	if ((fd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
87 		return 0;
88 	if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE,
89 	    name, strlen(name)) == -1) {
90 		close(fd);
91 		return 0;
92 	}
93 	close(fd);
94 	return 1;
95 }
96 #elif defined(SYS_RDOMAIN_XXX)
97 /* XXX examples */
98 char *
sys_get_rdomain(int fd)99 sys_get_rdomain(int fd)
100 {
101 	return NULL;
102 }
103 
104 int
sys_set_rdomain(int fd,const char * name)105 sys_set_rdomain(int fd, const char *name)
106 {
107 	return -1;
108 }
109 
110 int
valid_rdomain(const char * name)111 valid_rdomain(const char *name)
112 {
113 	return 0;
114 }
115 
116 void
sys_set_process_rdomain(const char * name)117 sys_set_process_rdomain(const char *name)
118 {
119 	fatal("%s: not supported", __func__);
120 }
121 #endif /* defined(SYS_RDOMAIN_XXX) */
122 
123 /*
124  * This is the portable version of the SSH tunnel forwarding, it
125  * uses some preprocessor definitions for various platform-specific
126  * settings.
127  *
128  * SSH_TUN_LINUX	Use the (newer) Linux tun/tap device
129  * SSH_TUN_FREEBSD	Use the FreeBSD tun/tap device
130  * SSH_TUN_COMPAT_AF	Translate the OpenBSD address family
131  * SSH_TUN_PREPEND_AF	Prepend/remove the address family
132  */
133 
134 /*
135  * System-specific tunnel open function
136  */
137 
138 #if defined(SSH_TUN_LINUX)
139 #include <linux/if_tun.h>
140 #define TUN_CTRL_DEV "/dev/net/tun"
141 
142 int
sys_tun_open(int tun,int mode,char ** ifname)143 sys_tun_open(int tun, int mode, char **ifname)
144 {
145 	struct ifreq ifr;
146 	int fd = -1;
147 	const char *name = NULL;
148 
149 	if (ifname != NULL)
150 		*ifname = NULL;
151 	if ((fd = open(TUN_CTRL_DEV, O_RDWR)) == -1) {
152 		debug("%s: failed to open tunnel control device \"%s\": %s",
153 		    __func__, TUN_CTRL_DEV, strerror(errno));
154 		return (-1);
155 	}
156 
157 	bzero(&ifr, sizeof(ifr));
158 
159 	if (mode == SSH_TUNMODE_ETHERNET) {
160 		ifr.ifr_flags = IFF_TAP;
161 		name = "tap%d";
162 	} else {
163 		ifr.ifr_flags = IFF_TUN;
164 		name = "tun%d";
165 	}
166 	ifr.ifr_flags |= IFF_NO_PI;
167 
168 	if (tun != SSH_TUNID_ANY) {
169 		if (tun > SSH_TUNID_MAX) {
170 			debug("%s: invalid tunnel id %x: %s", __func__,
171 			    tun, strerror(errno));
172 			goto failed;
173 		}
174 		snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), name, tun);
175 	}
176 
177 	if (ioctl(fd, TUNSETIFF, &ifr) == -1) {
178 		debug("%s: failed to configure tunnel (mode %d): %s", __func__,
179 		    mode, strerror(errno));
180 		goto failed;
181 	}
182 
183 	if (tun == SSH_TUNID_ANY)
184 		debug("%s: tunnel mode %d fd %d", __func__, mode, fd);
185 	else
186 		debug("%s: %s mode %d fd %d", __func__, ifr.ifr_name, mode, fd);
187 
188 	if (ifname != NULL && (*ifname = strdup(ifr.ifr_name)) == NULL)
189 		goto failed;
190 
191 	return (fd);
192 
193  failed:
194 	close(fd);
195 	return (-1);
196 }
197 #endif /* SSH_TUN_LINUX */
198 
199 #ifdef SSH_TUN_FREEBSD
200 #include <sys/socket.h>
201 #include <net/if.h>
202 
203 #ifdef HAVE_NET_IF_TUN_H
204 #include <net/if_tun.h>
205 #endif
206 
207 int
sys_tun_open(int tun,int mode,char ** ifname)208 sys_tun_open(int tun, int mode, char **ifname)
209 {
210 	struct ifreq ifr;
211 	char name[100];
212 	int fd = -1, sock;
213 	const char *tunbase = "tun";
214 #if defined(TUNSIFHEAD) && !defined(SSH_TUN_PREPEND_AF)
215 	int flag;
216 #endif
217 
218 	if (ifname != NULL)
219 		*ifname = NULL;
220 
221 	if (mode == SSH_TUNMODE_ETHERNET) {
222 #ifdef SSH_TUN_NO_L2
223 		debug("%s: no layer 2 tunnelling support", __func__);
224 		return (-1);
225 #else
226 		tunbase = "tap";
227 #endif
228 	}
229 
230 	/* Open the tunnel device */
231 	if (tun <= SSH_TUNID_MAX) {
232 		snprintf(name, sizeof(name), "/dev/%s%d", tunbase, tun);
233 		fd = open(name, O_RDWR);
234 	} else if (tun == SSH_TUNID_ANY) {
235 		for (tun = 100; tun >= 0; tun--) {
236 			snprintf(name, sizeof(name), "/dev/%s%d",
237 			    tunbase, tun);
238 			if ((fd = open(name, O_RDWR)) >= 0)
239 				break;
240 		}
241 	} else {
242 		debug("%s: invalid tunnel %u\n", __func__, tun);
243 		return (-1);
244 	}
245 
246 	if (fd < 0) {
247 		debug("%s: %s open failed: %s", __func__, name,
248 		    strerror(errno));
249 		return (-1);
250 	}
251 
252 	/* Turn on tunnel headers */
253 #if defined(TUNSIFHEAD) && !defined(SSH_TUN_PREPEND_AF)
254 	flag = 1;
255 	if (mode != SSH_TUNMODE_ETHERNET &&
256 	    ioctl(fd, TUNSIFHEAD, &flag) == -1) {
257 		debug("%s: ioctl(%d, TUNSIFHEAD, 1): %s", __func__, fd,
258 		    strerror(errno));
259 		close(fd);
260 	}
261 #endif
262 
263 	debug("%s: %s mode %d fd %d", __func__, name, mode, fd);
264 
265 	/* Set the tunnel device operation mode */
266 	snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "%s%d", tunbase, tun);
267 	if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) == -1)
268 		goto failed;
269 
270 	if (ioctl(sock, SIOCGIFFLAGS, &ifr) == -1)
271 		goto failed;
272 	if ((ifr.ifr_flags & IFF_UP) == 0) {
273 		ifr.ifr_flags |= IFF_UP;
274 		if (ioctl(sock, SIOCSIFFLAGS, &ifr) == -1)
275 			goto failed;
276 	}
277 
278 	if (ifname != NULL && (*ifname = strdup(ifr.ifr_name)) == NULL)
279 		goto failed;
280 
281 	close(sock);
282 	return (fd);
283 
284  failed:
285 	if (fd >= 0)
286 		close(fd);
287 	if (sock >= 0)
288 		close(sock);
289 	debug("%s: failed to set %s mode %d: %s", __func__, name,
290 	    mode, strerror(errno));
291 	return (-1);
292 }
293 #endif /* SSH_TUN_FREEBSD */
294 
295 /*
296  * System-specific channel filters
297  */
298 
299 #if defined(SSH_TUN_FILTER)
300 /*
301  * The tunnel forwarding protocol prepends the address family of forwarded
302  * IP packets using OpenBSD's numbers.
303  */
304 #define OPENBSD_AF_INET		2
305 #define OPENBSD_AF_INET6	24
306 
307 int
sys_tun_infilter(struct ssh * ssh,struct Channel * c,char * buf,int _len)308 sys_tun_infilter(struct ssh *ssh, struct Channel *c, char *buf, int _len)
309 {
310 	int r;
311 	size_t len;
312 	char *ptr = buf;
313 #if defined(SSH_TUN_PREPEND_AF)
314 	char rbuf[CHAN_RBUF];
315 	struct ip iph;
316 #endif
317 #if defined(SSH_TUN_PREPEND_AF) || defined(SSH_TUN_COMPAT_AF)
318 	u_int32_t af;
319 #endif
320 
321 	/* XXX update channel input filter API to use unsigned length */
322 	if (_len < 0)
323 		return -1;
324 	len = _len;
325 
326 #if defined(SSH_TUN_PREPEND_AF)
327 	if (len <= sizeof(iph) || len > sizeof(rbuf) - 4)
328 		return -1;
329 	/* Determine address family from packet IP header. */
330 	memcpy(&iph, buf, sizeof(iph));
331 	af = iph.ip_v == 6 ? OPENBSD_AF_INET6 : OPENBSD_AF_INET;
332 	/* Prepend address family to packet using OpenBSD constants */
333 	memcpy(rbuf + 4, buf, len);
334 	len += 4;
335 	POKE_U32(rbuf, af);
336 	ptr = rbuf;
337 #elif defined(SSH_TUN_COMPAT_AF)
338 	/* Convert existing address family header to OpenBSD value */
339 	if (len <= 4)
340 		return -1;
341 	af = PEEK_U32(buf);
342 	/* Put it back */
343 	POKE_U32(buf, af == AF_INET6 ? OPENBSD_AF_INET6 : OPENBSD_AF_INET);
344 #endif
345 
346 	if ((r = sshbuf_put_string(c->input, ptr, len)) != 0)
347 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
348 	return (0);
349 }
350 
351 u_char *
sys_tun_outfilter(struct ssh * ssh,struct Channel * c,u_char ** data,size_t * dlen)352 sys_tun_outfilter(struct ssh *ssh, struct Channel *c,
353     u_char **data, size_t *dlen)
354 {
355 	u_char *buf;
356 	u_int32_t af;
357 	int r;
358 
359 	/* XXX new API is incompatible with this signature. */
360 	if ((r = sshbuf_get_string(c->output, data, dlen)) != 0)
361 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
362 	if (*dlen < sizeof(af))
363 		return (NULL);
364 	buf = *data;
365 
366 #if defined(SSH_TUN_PREPEND_AF)
367 	/* skip address family */
368 	*dlen -= sizeof(af);
369 	buf = *data + sizeof(af);
370 #elif defined(SSH_TUN_COMPAT_AF)
371 	/* translate address family */
372 	af = (PEEK_U32(buf) == OPENBSD_AF_INET6) ? AF_INET6 : AF_INET;
373 	POKE_U32(buf, af);
374 #endif
375 	return (buf);
376 }
377 #endif /* SSH_TUN_FILTER */
378