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1 | /* | |
2 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
3 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
4 | * All rights reserved | |
5 | * Functions for returning the canonical host name of the remote site. | |
6 | * | |
7 | * As far as I am concerned, the code I have written for this software | |
8 | * can be used freely for any purpose. Any derived versions of this | |
9 | * software must be clearly marked as such, and if the derived work is | |
10 | * incompatible with the protocol description in the RFC file, it must be | |
11 | * called by a name other than "ssh" or "Secure Shell". | |
12 | */ | |
13 | ||
14 | #include "includes.h" | |
15 | RCSID("$OpenBSD: canohost.c,v 1.48 2005/12/28 22:46:06 stevesk Exp $"); | |
16 | ||
17 | #include "packet.h" | |
18 | #include "xmalloc.h" | |
19 | #include "log.h" | |
20 | #include "canohost.h" | |
21 | ||
22 | static void check_ip_options(int, char *); | |
23 | ||
24 | /* | |
25 | * Return the canonical name of the host at the other end of the socket. The | |
26 | * caller should free the returned string with xfree. | |
27 | */ | |
28 | ||
29 | static char * | |
30 | get_remote_hostname(int sock, int use_dns) | |
31 | { | |
32 | struct sockaddr_storage from; | |
33 | int i; | |
34 | socklen_t fromlen; | |
35 | struct addrinfo hints, *ai, *aitop; | |
36 | char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST]; | |
37 | ||
38 | /* Get IP address of client. */ | |
39 | fromlen = sizeof(from); | |
40 | memset(&from, 0, sizeof(from)); | |
41 | if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { | |
42 | debug("getpeername failed: %.100s", strerror(errno)); | |
43 | cleanup_exit(255); | |
44 | } | |
45 | ||
46 | ipv64_normalise_mapped(&from, &fromlen); | |
47 | ||
48 | if (from.ss_family == AF_INET6) | |
49 | fromlen = sizeof(struct sockaddr_in6); | |
50 | ||
51 | if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop), | |
52 | NULL, 0, NI_NUMERICHOST) != 0) | |
53 | fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed"); | |
54 | ||
55 | if (from.ss_family == AF_INET) | |
56 | check_ip_options(sock, ntop); | |
57 | ||
58 | if (!use_dns) | |
59 | return xstrdup(ntop); | |
60 | ||
61 | debug3("Trying to reverse map address %.100s.", ntop); | |
62 | /* Map the IP address to a host name. */ | |
63 | if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), | |
64 | NULL, 0, NI_NAMEREQD) != 0) { | |
65 | /* Host name not found. Use ip address. */ | |
66 | return xstrdup(ntop); | |
67 | } | |
68 | ||
69 | /* | |
70 | * if reverse lookup result looks like a numeric hostname, | |
71 | * someone is trying to trick us by PTR record like following: | |
72 | * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 | |
73 | */ | |
74 | memset(&hints, 0, sizeof(hints)); | |
75 | hints.ai_socktype = SOCK_DGRAM; /*dummy*/ | |
76 | hints.ai_flags = AI_NUMERICHOST; | |
77 | if (getaddrinfo(name, "0", &hints, &ai) == 0) { | |
78 | logit("Nasty PTR record \"%s\" is set up for %s, ignoring", | |
79 | name, ntop); | |
80 | freeaddrinfo(ai); | |
81 | return xstrdup(ntop); | |
82 | } | |
83 | ||
84 | /* | |
85 | * Convert it to all lowercase (which is expected by the rest | |
86 | * of this software). | |
87 | */ | |
88 | for (i = 0; name[i]; i++) | |
89 | if (isupper(name[i])) | |
90 | name[i] = tolower(name[i]); | |
91 | /* | |
92 | * Map it back to an IP address and check that the given | |
93 | * address actually is an address of this host. This is | |
94 | * necessary because anyone with access to a name server can | |
95 | * define arbitrary names for an IP address. Mapping from | |
96 | * name to IP address can be trusted better (but can still be | |
97 | * fooled if the intruder has access to the name server of | |
98 | * the domain). | |
99 | */ | |
100 | memset(&hints, 0, sizeof(hints)); | |
101 | hints.ai_family = from.ss_family; | |
102 | hints.ai_socktype = SOCK_STREAM; | |
103 | if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { | |
104 | logit("reverse mapping checking getaddrinfo for %.700s " | |
105 | "failed - POSSIBLE BREAK-IN ATTEMPT!", name); | |
106 | return xstrdup(ntop); | |
107 | } | |
108 | /* Look for the address from the list of addresses. */ | |
109 | for (ai = aitop; ai; ai = ai->ai_next) { | |
110 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, | |
111 | sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && | |
112 | (strcmp(ntop, ntop2) == 0)) | |
113 | break; | |
114 | } | |
115 | freeaddrinfo(aitop); | |
116 | /* If we reached the end of the list, the address was not there. */ | |
117 | if (!ai) { | |
118 | /* Address not found for the host name. */ | |
119 | logit("Address %.100s maps to %.600s, but this does not " | |
120 | "map back to the address - POSSIBLE BREAK-IN ATTEMPT!", | |
121 | ntop, name); | |
122 | return xstrdup(ntop); | |
123 | } | |
124 | return xstrdup(name); | |
125 | } | |
126 | ||
127 | /* | |
128 | * If IP options are supported, make sure there are none (log and | |
129 | * disconnect them if any are found). Basically we are worried about | |
130 | * source routing; it can be used to pretend you are somebody | |
131 | * (ip-address) you are not. That itself may be "almost acceptable" | |
132 | * under certain circumstances, but rhosts autentication is useless | |
133 | * if source routing is accepted. Notice also that if we just dropped | |
134 | * source routing here, the other side could use IP spoofing to do | |
135 | * rest of the interaction and could still bypass security. So we | |
136 | * exit here if we detect any IP options. | |
137 | */ | |
138 | /* IPv4 only */ | |
139 | static void | |
140 | check_ip_options(int sock, char *ipaddr) | |
141 | { | |
142 | #ifdef IP_OPTIONS | |
143 | u_char options[200]; | |
144 | char text[sizeof(options) * 3 + 1]; | |
145 | socklen_t option_size; | |
146 | u_int i; | |
147 | int ipproto; | |
148 | struct protoent *ip; | |
149 | ||
150 | if ((ip = getprotobyname("ip")) != NULL) | |
151 | ipproto = ip->p_proto; | |
152 | else | |
153 | ipproto = IPPROTO_IP; | |
154 | option_size = sizeof(options); | |
155 | if (getsockopt(sock, ipproto, IP_OPTIONS, options, | |
156 | &option_size) >= 0 && option_size != 0) { | |
157 | text[0] = '\0'; | |
158 | for (i = 0; i < option_size; i++) | |
159 | snprintf(text + i*3, sizeof(text) - i*3, | |
160 | " %2.2x", options[i]); | |
161 | fatal("Connection from %.100s with IP options:%.800s", | |
162 | ipaddr, text); | |
163 | } | |
164 | #endif /* IP_OPTIONS */ | |
165 | } | |
166 | ||
167 | void | |
168 | ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len) | |
169 | { | |
170 | struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr; | |
171 | struct sockaddr_in *a4 = (struct sockaddr_in *)addr; | |
172 | struct in_addr inaddr; | |
173 | u_int16_t port; | |
174 | ||
175 | if (addr->ss_family != AF_INET6 || | |
176 | !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr)) | |
177 | return; | |
178 | ||
179 | debug3("Normalising mapped IPv4 in IPv6 address"); | |
180 | ||
181 | memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr)); | |
182 | port = a6->sin6_port; | |
183 | ||
184 | memset(addr, 0, sizeof(*a4)); | |
185 | ||
186 | a4->sin_family = AF_INET; | |
187 | *len = sizeof(*a4); | |
188 | memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr)); | |
189 | a4->sin_port = port; | |
190 | } | |
191 | ||
192 | /* | |
193 | * Return the canonical name of the host in the other side of the current | |
194 | * connection. The host name is cached, so it is efficient to call this | |
195 | * several times. | |
196 | */ | |
197 | ||
198 | const char * | |
199 | get_canonical_hostname(int use_dns) | |
200 | { | |
201 | char *host; | |
202 | static char *canonical_host_name = NULL; | |
203 | static char *remote_ip = NULL; | |
204 | ||
205 | /* Check if we have previously retrieved name with same option. */ | |
206 | if (use_dns && canonical_host_name != NULL) | |
207 | return canonical_host_name; | |
208 | if (!use_dns && remote_ip != NULL) | |
209 | return remote_ip; | |
210 | ||
211 | /* Get the real hostname if socket; otherwise return UNKNOWN. */ | |
212 | if (packet_connection_is_on_socket()) | |
213 | host = get_remote_hostname(packet_get_connection_in(), use_dns); | |
214 | else | |
215 | host = "UNKNOWN"; | |
216 | ||
217 | if (use_dns) | |
218 | canonical_host_name = host; | |
219 | else | |
220 | remote_ip = host; | |
221 | return host; | |
222 | } | |
223 | ||
224 | /* | |
225 | * Returns the local/remote IP-address/hostname of socket as a string. | |
226 | * The returned string must be freed. | |
227 | */ | |
228 | static char * | |
229 | get_socket_address(int sock, int remote, int flags) | |
230 | { | |
231 | struct sockaddr_storage addr; | |
232 | socklen_t addrlen; | |
233 | char ntop[NI_MAXHOST]; | |
234 | int r; | |
235 | ||
236 | /* Get IP address of client. */ | |
237 | addrlen = sizeof(addr); | |
238 | memset(&addr, 0, sizeof(addr)); | |
239 | ||
240 | if (remote) { | |
241 | if (getpeername(sock, (struct sockaddr *)&addr, &addrlen) | |
242 | < 0) | |
243 | return NULL; | |
244 | } else { | |
245 | if (getsockname(sock, (struct sockaddr *)&addr, &addrlen) | |
246 | < 0) | |
247 | return NULL; | |
248 | } | |
249 | ||
250 | /* Work around Linux IPv6 weirdness */ | |
251 | if (addr.ss_family == AF_INET6) | |
252 | addrlen = sizeof(struct sockaddr_in6); | |
253 | ||
254 | ipv64_normalise_mapped(&addr, &addrlen); | |
255 | ||
256 | /* Get the address in ascii. */ | |
257 | if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop, | |
258 | sizeof(ntop), NULL, 0, flags)) != 0) { | |
259 | error("get_socket_address: getnameinfo %d failed: %s", flags, | |
260 | r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r)); | |
261 | return NULL; | |
262 | } | |
263 | return xstrdup(ntop); | |
264 | } | |
265 | ||
266 | char * | |
267 | get_peer_ipaddr(int sock) | |
268 | { | |
269 | char *p; | |
270 | ||
271 | if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL) | |
272 | return p; | |
273 | return xstrdup("UNKNOWN"); | |
274 | } | |
275 | ||
276 | char * | |
277 | get_local_ipaddr(int sock) | |
278 | { | |
279 | char *p; | |
280 | ||
281 | if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL) | |
282 | return p; | |
283 | return xstrdup("UNKNOWN"); | |
284 | } | |
285 | ||
286 | char * | |
287 | get_local_name(int sock) | |
288 | { | |
289 | return get_socket_address(sock, 0, NI_NAMEREQD); | |
290 | } | |
291 | ||
292 | /* | |
293 | * Returns the IP-address of the remote host as a string. The returned | |
294 | * string must not be freed. | |
295 | */ | |
296 | ||
297 | const char * | |
298 | get_remote_ipaddr(void) | |
299 | { | |
300 | static char *canonical_host_ip = NULL; | |
301 | ||
302 | /* Check whether we have cached the ipaddr. */ | |
303 | if (canonical_host_ip == NULL) { | |
304 | if (packet_connection_is_on_socket()) { | |
305 | canonical_host_ip = | |
306 | get_peer_ipaddr(packet_get_connection_in()); | |
307 | if (canonical_host_ip == NULL) | |
308 | cleanup_exit(255); | |
309 | } else { | |
310 | /* If not on socket, return UNKNOWN. */ | |
311 | canonical_host_ip = xstrdup("UNKNOWN"); | |
312 | } | |
313 | } | |
314 | return canonical_host_ip; | |
315 | } | |
316 | ||
317 | const char * | |
318 | get_remote_name_or_ip(u_int utmp_len, int use_dns) | |
319 | { | |
320 | static const char *remote = ""; | |
321 | if (utmp_len > 0) | |
322 | remote = get_canonical_hostname(use_dns); | |
323 | if (utmp_len == 0 || strlen(remote) > utmp_len) | |
324 | remote = get_remote_ipaddr(); | |
325 | return remote; | |
326 | } | |
327 | ||
328 | /* Returns the local/remote port for the socket. */ | |
329 | ||
330 | static int | |
331 | get_sock_port(int sock, int local) | |
332 | { | |
333 | struct sockaddr_storage from; | |
334 | socklen_t fromlen; | |
335 | char strport[NI_MAXSERV]; | |
336 | int r; | |
337 | ||
338 | /* Get IP address of client. */ | |
339 | fromlen = sizeof(from); | |
340 | memset(&from, 0, sizeof(from)); | |
341 | if (local) { | |
342 | if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) { | |
343 | error("getsockname failed: %.100s", strerror(errno)); | |
344 | return 0; | |
345 | } | |
346 | } else { | |
347 | if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { | |
348 | debug("getpeername failed: %.100s", strerror(errno)); | |
349 | return -1; | |
350 | } | |
351 | } | |
352 | ||
353 | /* Work around Linux IPv6 weirdness */ | |
354 | if (from.ss_family == AF_INET6) | |
355 | fromlen = sizeof(struct sockaddr_in6); | |
356 | ||
357 | /* Return port number. */ | |
358 | if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0, | |
359 | strport, sizeof(strport), NI_NUMERICSERV)) != 0) | |
360 | fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s", | |
361 | r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r)); | |
362 | return atoi(strport); | |
363 | } | |
364 | ||
365 | /* Returns remote/local port number for the current connection. */ | |
366 | ||
367 | static int | |
368 | get_port(int local) | |
369 | { | |
370 | /* | |
371 | * If the connection is not a socket, return 65535. This is | |
372 | * intentionally chosen to be an unprivileged port number. | |
373 | */ | |
374 | if (!packet_connection_is_on_socket()) | |
375 | return 65535; | |
376 | ||
377 | /* Get socket and return the port number. */ | |
378 | return get_sock_port(packet_get_connection_in(), local); | |
379 | } | |
380 | ||
381 | int | |
382 | get_peer_port(int sock) | |
383 | { | |
384 | return get_sock_port(sock, 0); | |
385 | } | |
386 | ||
387 | int | |
388 | get_remote_port(void) | |
389 | { | |
390 | static int port = -1; | |
391 | ||
392 | /* Cache to avoid getpeername() on a dead connection */ | |
393 | if (port == -1) | |
394 | port = get_port(0); | |
395 | ||
396 | return port; | |
397 | } | |
398 | ||
399 | int | |
400 | get_local_port(void) | |
401 | { | |
402 | return get_port(1); | |
403 | } | |
404 | ||
405 | void | |
406 | resolve_localhost(char **host) | |
407 | { | |
408 | struct hostent *hostinfo; | |
409 | ||
410 | hostinfo = gethostbyname(*host); | |
411 | if (hostinfo == NULL || hostinfo->h_name == NULL) { | |
412 | debug("gethostbyname(%s) failed", *host); | |
413 | return; | |
414 | } | |
415 | if (hostinfo->h_addrtype == AF_INET) { | |
416 | struct in_addr addr; | |
417 | addr = *(struct in_addr *)(hostinfo->h_addr); | |
418 | if (ntohl(addr.s_addr) == INADDR_LOOPBACK) { | |
419 | char buf[MAXHOSTNAMELEN]; | |
420 | if (gethostname(buf, sizeof(buf)) < 0) { | |
421 | debug("gethostname() failed"); | |
422 | return; | |
423 | } | |
424 | hostinfo = gethostbyname(buf); | |
425 | xfree(*host); | |
426 | if (hostinfo == NULL || hostinfo->h_name == NULL) { | |
427 | *host = xstrdup(buf); | |
428 | } else { | |
429 | *host = xstrdup(hostinfo->h_name); | |
430 | } | |
431 | } | |
432 | } | |
433 | } |