1 /* $OpenBSD: canohost.c,v 1.72 2015/03/01 15:44:40 millert Exp $ */
2 /*
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * All rights reserved
6 * Functions for returning the canonical host name of the remote site.
7 *
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose. Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
13 */
14
15 #include "includes.h"
16
17 #include <sys/types.h>
18 #include <sys/socket.h>
19 #include <sys/un.h>
20
21 #include <netinet/in.h>
22 #include <arpa/inet.h>
23
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 <unistd.h>
31
32 #include "xmalloc.h"
33 #include "packet.h"
34 #include "log.h"
35 #include "canohost.h"
36 #include "misc.h"
37
38 static void check_ip_options(int, char *);
39 static char *canonical_host_ip = NULL;
40 static int cached_port = -1;
41
42 /*
43 * Return the canonical name of the host at the other end of the socket. The
44 * caller should free the returned string.
45 */
46
47 static char *
get_remote_hostname(int sock,int use_dns)48 get_remote_hostname(int sock, int use_dns)
49 {
50 struct sockaddr_storage from;
51 socklen_t fromlen;
52 struct addrinfo hints, *ai, *aitop;
53 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
54
55 /* Get IP address of client. */
56 fromlen = sizeof(from);
57 memset(&from, 0, sizeof(from));
58 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
59 debug("getpeername failed: %.100s", strerror(errno));
60 cleanup_exit(255);
61 }
62
63 if (from.ss_family == AF_INET)
64 check_ip_options(sock, ntop);
65
66 ipv64_normalise_mapped(&from, &fromlen);
67
68 if (from.ss_family == AF_INET6)
69 fromlen = sizeof(struct sockaddr_in6);
70
71 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
72 NULL, 0, NI_NUMERICHOST) != 0)
73 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
74
75 if (!use_dns)
76 return xstrdup(ntop);
77
78 debug3("Trying to reverse map address %.100s.", ntop);
79 /* Map the IP address to a host name. */
80 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
81 NULL, 0, NI_NAMEREQD) != 0) {
82 /* Host name not found. Use ip address. */
83 return xstrdup(ntop);
84 }
85
86 /*
87 * if reverse lookup result looks like a numeric hostname,
88 * someone is trying to trick us by PTR record like following:
89 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
90 */
91 memset(&hints, 0, sizeof(hints));
92 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
93 hints.ai_flags = AI_NUMERICHOST;
94 if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
95 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
96 name, ntop);
97 freeaddrinfo(ai);
98 return xstrdup(ntop);
99 }
100
101 /* Names are stores in lowercase. */
102 lowercase(name);
103
104 /*
105 * Map it back to an IP address and check that the given
106 * address actually is an address of this host. This is
107 * necessary because anyone with access to a name server can
108 * define arbitrary names for an IP address. Mapping from
109 * name to IP address can be trusted better (but can still be
110 * fooled if the intruder has access to the name server of
111 * the domain).
112 */
113 memset(&hints, 0, sizeof(hints));
114 hints.ai_family = from.ss_family;
115 hints.ai_socktype = SOCK_STREAM;
116 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
117 logit("reverse mapping checking getaddrinfo for %.700s "
118 "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop);
119 return xstrdup(ntop);
120 }
121 /* Look for the address from the list of addresses. */
122 for (ai = aitop; ai; ai = ai->ai_next) {
123 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
124 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
125 (strcmp(ntop, ntop2) == 0))
126 break;
127 }
128 freeaddrinfo(aitop);
129 /* If we reached the end of the list, the address was not there. */
130 if (!ai) {
131 /* Address not found for the host name. */
132 logit("Address %.100s maps to %.600s, but this does not "
133 "map back to the address - POSSIBLE BREAK-IN ATTEMPT!",
134 ntop, name);
135 return xstrdup(ntop);
136 }
137 return xstrdup(name);
138 }
139
140 /*
141 * If IP options are supported, make sure there are none (log and
142 * disconnect them if any are found). Basically we are worried about
143 * source routing; it can be used to pretend you are somebody
144 * (ip-address) you are not. That itself may be "almost acceptable"
145 * under certain circumstances, but rhosts autentication is useless
146 * if source routing is accepted. Notice also that if we just dropped
147 * source routing here, the other side could use IP spoofing to do
148 * rest of the interaction and could still bypass security. So we
149 * exit here if we detect any IP options.
150 */
151 /* IPv4 only */
152 static void
check_ip_options(int sock,char * ipaddr)153 check_ip_options(int sock, char *ipaddr)
154 {
155 #ifdef IP_OPTIONS
156 u_char options[200];
157 char text[sizeof(options) * 3 + 1];
158 socklen_t option_size, i;
159 int ipproto;
160 struct protoent *ip;
161
162 if ((ip = getprotobyname("ip")) != NULL)
163 ipproto = ip->p_proto;
164 else
165 ipproto = IPPROTO_IP;
166 option_size = sizeof(options);
167 if (getsockopt(sock, ipproto, IP_OPTIONS, options,
168 &option_size) >= 0 && option_size != 0) {
169 text[0] = '\0';
170 for (i = 0; i < option_size; i++)
171 snprintf(text + i*3, sizeof(text) - i*3,
172 " %2.2x", options[i]);
173 fatal("Connection from %.100s with IP options:%.800s",
174 ipaddr, text);
175 }
176 #endif /* IP_OPTIONS */
177 }
178
179 void
ipv64_normalise_mapped(struct sockaddr_storage * addr,socklen_t * len)180 ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
181 {
182 struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr;
183 struct sockaddr_in *a4 = (struct sockaddr_in *)addr;
184 struct in_addr inaddr;
185 u_int16_t port;
186
187 if (addr->ss_family != AF_INET6 ||
188 !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr))
189 return;
190
191 debug3("Normalising mapped IPv4 in IPv6 address");
192
193 memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr));
194 port = a6->sin6_port;
195
196 memset(a4, 0, sizeof(*a4));
197
198 a4->sin_family = AF_INET;
199 *len = sizeof(*a4);
200 memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr));
201 a4->sin_port = port;
202 }
203
204 /*
205 * Return the canonical name of the host in the other side of the current
206 * connection. The host name is cached, so it is efficient to call this
207 * several times.
208 */
209
210 const char *
get_canonical_hostname(int use_dns)211 get_canonical_hostname(int use_dns)
212 {
213 char *host;
214 static char *canonical_host_name = NULL;
215 static char *remote_ip = NULL;
216
217 /* Check if we have previously retrieved name with same option. */
218 if (use_dns && canonical_host_name != NULL)
219 return canonical_host_name;
220 if (!use_dns && remote_ip != NULL)
221 return remote_ip;
222
223 /* Get the real hostname if socket; otherwise return UNKNOWN. */
224 if (packet_connection_is_on_socket())
225 host = get_remote_hostname(packet_get_connection_in(), use_dns);
226 else
227 host = "UNKNOWN";
228
229 if (use_dns)
230 canonical_host_name = host;
231 else
232 remote_ip = host;
233 return host;
234 }
235
236 /*
237 * Returns the local/remote IP-address/hostname of socket as a string.
238 * The returned string must be freed.
239 */
240 static char *
get_socket_address(int sock,int remote,int flags)241 get_socket_address(int sock, int remote, int flags)
242 {
243 struct sockaddr_storage addr;
244 socklen_t addrlen;
245 char ntop[NI_MAXHOST];
246 int r;
247
248 /* Get IP address of client. */
249 addrlen = sizeof(addr);
250 memset(&addr, 0, sizeof(addr));
251
252 if (remote) {
253 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen)
254 < 0)
255 return NULL;
256 } else {
257 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen)
258 < 0)
259 return NULL;
260 }
261
262 /* Work around Linux IPv6 weirdness */
263 if (addr.ss_family == AF_INET6) {
264 addrlen = sizeof(struct sockaddr_in6);
265 ipv64_normalise_mapped(&addr, &addrlen);
266 }
267
268 switch (addr.ss_family) {
269 case AF_INET:
270 case AF_INET6:
271 /* Get the address in ascii. */
272 if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
273 sizeof(ntop), NULL, 0, flags)) != 0) {
274 error("get_socket_address: getnameinfo %d failed: %s",
275 flags, ssh_gai_strerror(r));
276 return NULL;
277 }
278 return xstrdup(ntop);
279 case AF_UNIX:
280 /* Get the Unix domain socket path. */
281 return xstrdup(((struct sockaddr_un *)&addr)->sun_path);
282 default:
283 /* We can't look up remote Unix domain sockets. */
284 return NULL;
285 }
286 }
287
288 char *
get_peer_ipaddr(int sock)289 get_peer_ipaddr(int sock)
290 {
291 char *p;
292
293 if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL)
294 return p;
295 return xstrdup("UNKNOWN");
296 }
297
298 char *
get_local_ipaddr(int sock)299 get_local_ipaddr(int sock)
300 {
301 char *p;
302
303 if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL)
304 return p;
305 return xstrdup("UNKNOWN");
306 }
307
308 char *
get_local_name(int fd)309 get_local_name(int fd)
310 {
311 char *host, myname[NI_MAXHOST];
312
313 /* Assume we were passed a socket */
314 if ((host = get_socket_address(fd, 0, NI_NAMEREQD)) != NULL)
315 return host;
316
317 /* Handle the case where we were passed a pipe */
318 if (gethostname(myname, sizeof(myname)) == -1) {
319 verbose("get_local_name: gethostname: %s", strerror(errno));
320 } else {
321 host = xstrdup(myname);
322 }
323
324 return host;
325 }
326
327 void
clear_cached_addr(void)328 clear_cached_addr(void)
329 {
330 free(canonical_host_ip);
331 canonical_host_ip = NULL;
332 cached_port = -1;
333 }
334
335 /*
336 * Returns the IP-address of the remote host as a string. The returned
337 * string must not be freed.
338 */
339
340 const char *
get_remote_ipaddr(void)341 get_remote_ipaddr(void)
342 {
343 /* Check whether we have cached the ipaddr. */
344 if (canonical_host_ip == NULL) {
345 if (packet_connection_is_on_socket()) {
346 canonical_host_ip =
347 get_peer_ipaddr(packet_get_connection_in());
348 if (canonical_host_ip == NULL)
349 cleanup_exit(255);
350 } else {
351 /* If not on socket, return UNKNOWN. */
352 canonical_host_ip = xstrdup("UNKNOWN");
353 }
354 }
355 return canonical_host_ip;
356 }
357
358 const char *
get_remote_name_or_ip(u_int utmp_len,int use_dns)359 get_remote_name_or_ip(u_int utmp_len, int use_dns)
360 {
361 static const char *remote = "";
362 if (utmp_len > 0)
363 remote = get_canonical_hostname(use_dns);
364 if (utmp_len == 0 || strlen(remote) > utmp_len)
365 remote = get_remote_ipaddr();
366 return remote;
367 }
368
369 /* Returns the local/remote port for the socket. */
370
371 int
get_sock_port(int sock,int local)372 get_sock_port(int sock, int local)
373 {
374 struct sockaddr_storage from;
375 socklen_t fromlen;
376 char strport[NI_MAXSERV];
377 int r;
378
379 /* Get IP address of client. */
380 fromlen = sizeof(from);
381 memset(&from, 0, sizeof(from));
382 if (local) {
383 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
384 error("getsockname failed: %.100s", strerror(errno));
385 return 0;
386 }
387 } else {
388 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
389 debug("getpeername failed: %.100s", strerror(errno));
390 return -1;
391 }
392 }
393
394 /* Work around Linux IPv6 weirdness */
395 if (from.ss_family == AF_INET6)
396 fromlen = sizeof(struct sockaddr_in6);
397
398 /* Non-inet sockets don't have a port number. */
399 if (from.ss_family != AF_INET && from.ss_family != AF_INET6)
400 return 0;
401
402 /* Return port number. */
403 if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
404 strport, sizeof(strport), NI_NUMERICSERV)) != 0)
405 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s",
406 ssh_gai_strerror(r));
407 return atoi(strport);
408 }
409
410 /* Returns remote/local port number for the current connection. */
411
412 static int
get_port(int local)413 get_port(int local)
414 {
415 /*
416 * If the connection is not a socket, return 65535. This is
417 * intentionally chosen to be an unprivileged port number.
418 */
419 if (!packet_connection_is_on_socket())
420 return 65535;
421
422 /* Get socket and return the port number. */
423 return get_sock_port(packet_get_connection_in(), local);
424 }
425
426 int
get_peer_port(int sock)427 get_peer_port(int sock)
428 {
429 return get_sock_port(sock, 0);
430 }
431
432 int
get_remote_port(void)433 get_remote_port(void)
434 {
435 /* Cache to avoid getpeername() on a dead connection */
436 if (cached_port == -1)
437 cached_port = get_port(0);
438
439 return cached_port;
440 }
441
442 int
get_local_port(void)443 get_local_port(void)
444 {
445 return get_port(1);
446 }
447