1 /*	$NetBSD: canohost.c,v 1.4 2010/11/21 18:29:48 adam Exp $	*/
2 /* $OpenBSD: canohost.c,v 1.66 2010/01/13 01:20:20 dtucker Exp $ */
3 /*
4  * Author: Tatu Ylonen <ylo@cs.hut.fi>
5  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6  *                    All rights reserved
7  * Functions for returning the canonical host name of the remote site.
8  *
9  * As far as I am concerned, the code I have written for this software
10  * can be used freely for any purpose.  Any derived versions of this
11  * software must be clearly marked as such, and if the derived work is
12  * incompatible with the protocol description in the RFC file, it must be
13  * called by a name other than "ssh" or "Secure Shell".
14  */
15 
16 #include "includes.h"
17 __RCSID("$NetBSD: canohost.c,v 1.4 2010/11/21 18:29:48 adam Exp $");
18 #include <sys/types.h>
19 #include <sys/socket.h>
20 
21 #include <netinet/in.h>
22 
23 #include <ctype.h>
24 #include <errno.h>
25 #include <netdb.h>
26 #include <stdio.h>
27 #include <stdlib.h>
28 #include <string.h>
29 #include <stdarg.h>
30 #include <time.h>
31 #include <unistd.h>
32 
33 #include "xmalloc.h"
34 #include "packet.h"
35 #include "log.h"
36 #include "canohost.h"
37 #include "misc.h"
38 
39 static void check_ip_options(int, char *);
40 static char *canonical_host_ip = NULL;
41 static int cached_port = -1;
42 
43 /*
44  * Return the canonical name of the host at the other end of the socket. The
45  * caller should free the returned string with xfree.
46  */
47 
48 static char *
49 get_remote_hostname(int sock, int use_dns)
50 {
51 	struct sockaddr_storage from;
52 	int i;
53 	socklen_t fromlen;
54 	struct addrinfo hints, *ai, *aitop;
55 	char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
56 
57 	/* Get IP address of client. */
58 	fromlen = sizeof(from);
59 	memset(&from, 0, sizeof(from));
60 	if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
61 		debug("getpeername failed: %.100s", strerror(errno));
62 		cleanup_exit(255);
63 	}
64 
65 	if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
66 	    NULL, 0, NI_NUMERICHOST) != 0)
67 		fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
68 
69 	if (from.ss_family == AF_INET)
70 		check_ip_options(sock, ntop);
71 
72 	if (!use_dns)
73 		return xstrdup(ntop);
74 
75 	debug3("Trying to reverse map address %.100s.", ntop);
76 	/* Map the IP address to a host name. */
77 	if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
78 	    NULL, 0, NI_NAMEREQD) != 0) {
79 		/* Host name not found.  Use ip address. */
80 		return xstrdup(ntop);
81 	}
82 
83 	/*
84 	 * if reverse lookup result looks like a numeric hostname,
85 	 * someone is trying to trick us by PTR record like following:
86 	 *	1.1.1.10.in-addr.arpa.	IN PTR	2.3.4.5
87 	 */
88 	memset(&hints, 0, sizeof(hints));
89 	hints.ai_socktype = SOCK_DGRAM;	/*dummy*/
90 	hints.ai_flags = AI_NUMERICHOST;
91 	if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
92 		logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
93 		    name, ntop);
94 		freeaddrinfo(ai);
95 		return xstrdup(ntop);
96 	}
97 
98 	/*
99 	 * Convert it to all lowercase (which is expected by the rest
100 	 * of this software).
101 	 */
102 	for (i = 0; name[i]; i++)
103 		if (isupper((unsigned char)name[i]))
104 			name[i] = (char)tolower((unsigned char)name[i]);
105 	/*
106 	 * Map it back to an IP address and check that the given
107 	 * address actually is an address of this host.  This is
108 	 * necessary because anyone with access to a name server can
109 	 * define arbitrary names for an IP address. Mapping from
110 	 * name to IP address can be trusted better (but can still be
111 	 * fooled if the intruder has access to the name server of
112 	 * the domain).
113 	 */
114 	memset(&hints, 0, sizeof(hints));
115 	hints.ai_family = from.ss_family;
116 	hints.ai_socktype = SOCK_STREAM;
117 	if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
118 		logit("reverse mapping checking getaddrinfo for %.700s "
119 		    "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop);
120 		return xstrdup(ntop);
121 	}
122 	/* Look for the address from the list of addresses. */
123 	for (ai = aitop; ai; ai = ai->ai_next) {
124 		if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
125 		    sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
126 		    (strcmp(ntop, ntop2) == 0))
127 				break;
128 	}
129 	freeaddrinfo(aitop);
130 	/* If we reached the end of the list, the address was not there. */
131 	if (!ai) {
132 		/* Address not found for the host name. */
133 		logit("Address %.100s maps to %.600s, but this does not "
134 		    "map back to the address - POSSIBLE BREAK-IN ATTEMPT!",
135 		    ntop, name);
136 		return xstrdup(ntop);
137 	}
138 	return xstrdup(name);
139 }
140 
141 /*
142  * If IP options are supported, make sure there are none (log and
143  * disconnect them if any are found).  Basically we are worried about
144  * source routing; it can be used to pretend you are somebody
145  * (ip-address) you are not. That itself may be "almost acceptable"
146  * under certain circumstances, but rhosts autentication is useless
147  * if source routing is accepted. Notice also that if we just dropped
148  * source routing here, the other side could use IP spoofing to do
149  * rest of the interaction and could still bypass security.  So we
150  * exit here if we detect any IP options.
151  */
152 /* IPv4 only */
153 static void
154 check_ip_options(int sock, char *ipaddr)
155 {
156 	u_char options[200];
157 	char text[sizeof(options) * 3 + 1];
158 	socklen_t option_size;
159 	u_int i;
160 	int ipproto;
161 	struct protoent *ip;
162 
163 	if ((ip = getprotobyname("ip")) != NULL)
164 		ipproto = ip->p_proto;
165 	else
166 		ipproto = IPPROTO_IP;
167 	option_size = sizeof(options);
168 	if (getsockopt(sock, ipproto, IP_OPTIONS, options,
169 	    &option_size) >= 0 && option_size != 0) {
170 		text[0] = '\0';
171 		for (i = 0; i < option_size; i++)
172 			snprintf(text + i*3, sizeof(text) - i*3,
173 			    " %2.2x", options[i]);
174 		fatal("Connection from %.100s with IP options:%.800s",
175 		    ipaddr, text);
176 	}
177 }
178 
179 /*
180  * Return the canonical name of the host in the other side of the current
181  * connection.  The host name is cached, so it is efficient to call this
182  * several times.
183  */
184 
185 const char *
186 get_canonical_hostname(int use_dns)
187 {
188 	char *host;
189 	static char *canonical_host_name = NULL;
190 	static char *remote_ip = NULL;
191 
192 	/* Check if we have previously retrieved name with same option. */
193 	if (use_dns && canonical_host_name != NULL)
194 		return canonical_host_name;
195 	if (!use_dns && remote_ip != NULL)
196 		return remote_ip;
197 
198 	/* Get the real hostname if socket; otherwise return UNKNOWN. */
199 	if (packet_connection_is_on_socket())
200 		host = get_remote_hostname(packet_get_connection_in(), use_dns);
201 	else
202 		host = "UNKNOWN";
203 
204 	if (use_dns)
205 		canonical_host_name = host;
206 	else
207 		remote_ip = host;
208 	return host;
209 }
210 
211 /*
212  * Returns the local/remote IP-address/hostname of socket as a string.
213  * The returned string must be freed.
214  */
215 static char *
216 get_socket_address(int sock, int remote, int flags)
217 {
218 	struct sockaddr_storage addr;
219 	socklen_t addrlen;
220 	char ntop[NI_MAXHOST];
221 	int r;
222 
223 	/* Get IP address of client. */
224 	addrlen = sizeof(addr);
225 	memset(&addr, 0, sizeof(addr));
226 
227 	if (remote) {
228 		if (getpeername(sock, (struct sockaddr *)&addr, &addrlen)
229 		    < 0)
230 			return NULL;
231 	} else {
232 		if (getsockname(sock, (struct sockaddr *)&addr, &addrlen)
233 		    < 0)
234 			return NULL;
235 	}
236 	/* Get the address in ascii. */
237 	if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
238 	    sizeof(ntop), NULL, 0, flags)) != 0) {
239 		error("get_socket_address: getnameinfo %d failed: %s", flags,
240 		    ssh_gai_strerror(r));
241 		return NULL;
242 	}
243 	return xstrdup(ntop);
244 }
245 
246 char *
247 get_peer_ipaddr(int sock)
248 {
249 	char *p;
250 
251 	if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL)
252 		return p;
253 	return xstrdup("UNKNOWN");
254 }
255 
256 char *
257 get_local_ipaddr(int sock)
258 {
259 	char *p;
260 
261 	if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL)
262 		return p;
263 	return xstrdup("UNKNOWN");
264 }
265 
266 char *
267 get_local_name(int fd)
268 {
269 	char *host, myname[NI_MAXHOST];
270 
271 	/* Assume we were passed a socket */
272 	if ((host = get_socket_address(fd, 0, NI_NAMEREQD)) != NULL)
273 		return host;
274 
275 	/* Handle the case where we were passed a pipe */
276 	if (gethostname(myname, sizeof(myname)) == -1) {
277 		verbose("get_local_name: gethostname: %s", strerror(errno));
278 	} else {
279 		host = xstrdup(myname);
280 	}
281 
282 	return host;
283 }
284 
285 void
286 clear_cached_addr(void)
287 {
288 	if (canonical_host_ip != NULL) {
289 		xfree(canonical_host_ip);
290 		canonical_host_ip = NULL;
291 	}
292 	cached_port = -1;
293 }
294 
295 /*
296  * Returns the IP-address of the remote host as a string.  The returned
297  * string must not be freed.
298  */
299 
300 const char *
301 get_remote_ipaddr(void)
302 {
303 	/* Check whether we have cached the ipaddr. */
304 	if (canonical_host_ip == NULL) {
305 		if (packet_connection_is_on_socket()) {
306 			canonical_host_ip =
307 			    get_peer_ipaddr(packet_get_connection_in());
308 			if (canonical_host_ip == NULL)
309 				cleanup_exit(255);
310 		} else {
311 			/* If not on socket, return UNKNOWN. */
312 			canonical_host_ip = xstrdup("UNKNOWN");
313 		}
314 	}
315 	return canonical_host_ip;
316 }
317 
318 const char *
319 get_remote_name_or_ip(u_int utmp_len, int use_dns)
320 {
321 	static const char *remote = "";
322 	if (utmp_len > 0)
323 		remote = get_canonical_hostname(use_dns);
324 	if (utmp_len == 0 || strlen(remote) > utmp_len)
325 		remote = get_remote_ipaddr();
326 	return remote;
327 }
328 
329 /* Returns the local/remote port for the socket. */
330 
331 int
332 get_sock_port(int sock, int local)
333 {
334 	struct sockaddr_storage from;
335 	socklen_t fromlen;
336 	char strport[NI_MAXSERV];
337 	int r;
338 
339 	/* Get IP address of client. */
340 	fromlen = sizeof(from);
341 	memset(&from, 0, sizeof(from));
342 	if (local) {
343 		if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
344 			error("getsockname failed: %.100s", strerror(errno));
345 			return 0;
346 		}
347 	} else {
348 		if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
349 			debug("getpeername failed: %.100s", strerror(errno));
350 			return -1;
351 		}
352 	}
353 	/* Return port number. */
354 	if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
355 	    strport, sizeof(strport), NI_NUMERICSERV)) != 0)
356 		fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s",
357 		    ssh_gai_strerror(r));
358 	return atoi(strport);
359 }
360 
361 /* Returns remote/local port number for the current connection. */
362 
363 static int
364 get_port(int local)
365 {
366 	/*
367 	 * If the connection is not a socket, return 65535.  This is
368 	 * intentionally chosen to be an unprivileged port number.
369 	 */
370 	if (!packet_connection_is_on_socket())
371 		return 65535;
372 
373 	/* Get socket and return the port number. */
374 	return get_sock_port(packet_get_connection_in(), local);
375 }
376 
377 int
378 get_peer_port(int sock)
379 {
380 	return get_sock_port(sock, 0);
381 }
382 
383 int
384 get_remote_port(void)
385 {
386 	/* Cache to avoid getpeername() on a dead connection */
387 	if (cached_port == -1)
388 		cached_port = get_port(0);
389 
390 	return cached_port;
391 }
392 
393 int
394 get_local_port(void)
395 {
396 	return get_port(1);
397 }
398