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1 | /* $OpenBSD: canohost.c,v 1.58 2006/07/22 20:48:22 stevesk 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 | ||
20 | #include <netinet/in.h> | |
21 | ||
22 | #include <ctype.h> | |
23 | #include <errno.h> | |
24 | #include <netdb.h> | |
25 | #include <string.h> | |
26 | ||
27 | #include "packet.h" | |
28 | #include "xmalloc.h" | |
29 | #include "log.h" | |
30 | #include "canohost.h" | |
31 | ||
32 | static void check_ip_options(int, char *); | |
33 | ||
34 | /* | |
35 | * Return the canonical name of the host at the other end of the socket. The | |
36 | * caller should free the returned string with xfree. | |
37 | */ | |
38 | ||
39 | static char * | |
40 | get_remote_hostname(int sock, int use_dns) | |
41 | { | |
42 | struct sockaddr_storage from; | |
43 | int i; | |
44 | socklen_t fromlen; | |
45 | struct addrinfo hints, *ai, *aitop; | |
46 | char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST]; | |
47 | ||
48 | /* Get IP address of client. */ | |
49 | fromlen = sizeof(from); | |
50 | memset(&from, 0, sizeof(from)); | |
51 | if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { | |
52 | debug("getpeername failed: %.100s", strerror(errno)); | |
53 | cleanup_exit(255); | |
54 | } | |
55 | ||
56 | if (from.ss_family == AF_INET) | |
57 | check_ip_options(sock, ntop); | |
58 | ||
59 | ipv64_normalise_mapped(&from, &fromlen); | |
60 | ||
61 | if (from.ss_family == AF_INET6) | |
62 | fromlen = sizeof(struct sockaddr_in6); | |
63 | ||
64 | if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop), | |
65 | NULL, 0, NI_NUMERICHOST) != 0) | |
66 | fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed"); | |
67 | ||
68 | if (!use_dns) | |
69 | return xstrdup(ntop); | |
70 | ||
71 | debug3("Trying to reverse map address %.100s.", ntop); | |
72 | /* Map the IP address to a host name. */ | |
73 | if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), | |
74 | NULL, 0, NI_NAMEREQD) != 0) { | |
75 | /* Host name not found. Use ip address. */ | |
76 | return xstrdup(ntop); | |
77 | } | |
78 | ||
79 | /* | |
80 | * if reverse lookup result looks like a numeric hostname, | |
81 | * someone is trying to trick us by PTR record like following: | |
82 | * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 | |
83 | */ | |
84 | memset(&hints, 0, sizeof(hints)); | |
85 | hints.ai_socktype = SOCK_DGRAM; /*dummy*/ | |
86 | hints.ai_flags = AI_NUMERICHOST; | |
87 | if (getaddrinfo(name, "0", &hints, &ai) == 0) { | |
88 | logit("Nasty PTR record \"%s\" is set up for %s, ignoring", | |
89 | name, ntop); | |
90 | freeaddrinfo(ai); | |
91 | return xstrdup(ntop); | |
92 | } | |
93 | ||
94 | /* | |
95 | * Convert it to all lowercase (which is expected by the rest | |
96 | * of this software). | |
97 | */ | |
98 | for (i = 0; name[i]; i++) | |
99 | if (isupper(name[i])) | |
100 | name[i] = (char)tolower(name[i]); | |
101 | /* | |
102 | * Map it back to an IP address and check that the given | |
103 | * address actually is an address of this host. This is | |
104 | * necessary because anyone with access to a name server can | |
105 | * define arbitrary names for an IP address. Mapping from | |
106 | * name to IP address can be trusted better (but can still be | |
107 | * fooled if the intruder has access to the name server of | |
108 | * the domain). | |
109 | */ | |
110 | memset(&hints, 0, sizeof(hints)); | |
111 | hints.ai_family = from.ss_family; | |
112 | hints.ai_socktype = SOCK_STREAM; | |
113 | if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { | |
114 | logit("reverse mapping checking getaddrinfo for %.700s " | |
115 | "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop); | |
116 | return xstrdup(ntop); | |
117 | } | |
118 | /* Look for the address from the list of addresses. */ | |
119 | for (ai = aitop; ai; ai = ai->ai_next) { | |
120 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, | |
121 | sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && | |
122 | (strcmp(ntop, ntop2) == 0)) | |
123 | break; | |
124 | } | |
125 | freeaddrinfo(aitop); | |
126 | /* If we reached the end of the list, the address was not there. */ | |
127 | if (!ai) { | |
128 | /* Address not found for the host name. */ | |
129 | logit("Address %.100s maps to %.600s, but this does not " | |
130 | "map back to the address - POSSIBLE BREAK-IN ATTEMPT!", | |
131 | ntop, name); | |
132 | return xstrdup(ntop); | |
133 | } | |
134 | return xstrdup(name); | |
135 | } | |
136 | ||
137 | /* | |
138 | * If IP options are supported, make sure there are none (log and | |
139 | * disconnect them if any are found). Basically we are worried about | |
140 | * source routing; it can be used to pretend you are somebody | |
141 | * (ip-address) you are not. That itself may be "almost acceptable" | |
142 | * under certain circumstances, but rhosts autentication is useless | |
143 | * if source routing is accepted. Notice also that if we just dropped | |
144 | * source routing here, the other side could use IP spoofing to do | |
145 | * rest of the interaction and could still bypass security. So we | |
146 | * exit here if we detect any IP options. | |
147 | */ | |
148 | /* IPv4 only */ | |
149 | static void | |
150 | check_ip_options(int sock, char *ipaddr) | |
151 | { | |
152 | #ifdef IP_OPTIONS | |
153 | u_char options[200]; | |
154 | char text[sizeof(options) * 3 + 1]; | |
155 | socklen_t option_size; | |
156 | u_int i; | |
157 | int ipproto; | |
158 | struct protoent *ip; | |
159 | ||
160 | if ((ip = getprotobyname("ip")) != NULL) | |
161 | ipproto = ip->p_proto; | |
162 | else | |
163 | ipproto = IPPROTO_IP; | |
164 | option_size = sizeof(options); | |
165 | if (getsockopt(sock, ipproto, IP_OPTIONS, options, | |
166 | &option_size) >= 0 && option_size != 0) { | |
167 | text[0] = '\0'; | |
168 | for (i = 0; i < option_size; i++) | |
169 | snprintf(text + i*3, sizeof(text) - i*3, | |
170 | " %2.2x", options[i]); | |
171 | fatal("Connection from %.100s with IP options:%.800s", | |
172 | ipaddr, text); | |
173 | } | |
174 | #endif /* IP_OPTIONS */ | |
175 | } | |
176 | ||
177 | void | |
178 | ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len) | |
179 | { | |
180 | struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr; | |
181 | struct sockaddr_in *a4 = (struct sockaddr_in *)addr; | |
182 | struct in_addr inaddr; | |
183 | u_int16_t port; | |
184 | ||
185 | if (addr->ss_family != AF_INET6 || | |
186 | !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr)) | |
187 | return; | |
188 | ||
189 | debug3("Normalising mapped IPv4 in IPv6 address"); | |
190 | ||
191 | memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr)); | |
192 | port = a6->sin6_port; | |
193 | ||
194 | memset(addr, 0, sizeof(*a4)); | |
195 | ||
196 | a4->sin_family = AF_INET; | |
197 | *len = sizeof(*a4); | |
198 | memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr)); | |
199 | a4->sin_port = port; | |
200 | } | |
201 | ||
202 | /* | |
203 | * Return the canonical name of the host in the other side of the current | |
204 | * connection. The host name is cached, so it is efficient to call this | |
205 | * several times. | |
206 | */ | |
207 | ||
208 | const char * | |
209 | get_canonical_hostname(int use_dns) | |
210 | { | |
211 | char *host; | |
212 | static char *canonical_host_name = NULL; | |
213 | static char *remote_ip = NULL; | |
214 | ||
215 | /* Check if we have previously retrieved name with same option. */ | |
216 | if (use_dns && canonical_host_name != NULL) | |
217 | return canonical_host_name; | |
218 | if (!use_dns && remote_ip != NULL) | |
219 | return remote_ip; | |
220 | ||
221 | /* Get the real hostname if socket; otherwise return UNKNOWN. */ | |
222 | if (packet_connection_is_on_socket()) | |
223 | host = get_remote_hostname(packet_get_connection_in(), use_dns); | |
224 | else | |
225 | host = "UNKNOWN"; | |
226 | ||
227 | if (use_dns) | |
228 | canonical_host_name = host; | |
229 | else | |
230 | remote_ip = host; | |
231 | return host; | |
232 | } | |
233 | ||
234 | /* | |
235 | * Returns the local/remote IP-address/hostname of socket as a string. | |
236 | * The returned string must be freed. | |
237 | */ | |
238 | static char * | |
239 | get_socket_address(int sock, int remote, int flags) | |
240 | { | |
241 | struct sockaddr_storage addr; | |
242 | socklen_t addrlen; | |
243 | char ntop[NI_MAXHOST]; | |
244 | int r; | |
245 | ||
246 | /* Get IP address of client. */ | |
247 | addrlen = sizeof(addr); | |
248 | memset(&addr, 0, sizeof(addr)); | |
249 | ||
250 | if (remote) { | |
251 | if (getpeername(sock, (struct sockaddr *)&addr, &addrlen) | |
252 | < 0) | |
253 | return NULL; | |
254 | } else { | |
255 | if (getsockname(sock, (struct sockaddr *)&addr, &addrlen) | |
256 | < 0) | |
257 | return NULL; | |
258 | } | |
259 | ||
260 | /* Work around Linux IPv6 weirdness */ | |
261 | if (addr.ss_family == AF_INET6) | |
262 | addrlen = sizeof(struct sockaddr_in6); | |
263 | ||
264 | ipv64_normalise_mapped(&addr, &addrlen); | |
265 | ||
266 | /* Get the address in ascii. */ | |
267 | if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop, | |
268 | sizeof(ntop), NULL, 0, flags)) != 0) { | |
269 | error("get_socket_address: getnameinfo %d failed: %s", flags, | |
270 | r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r)); | |
271 | return NULL; | |
272 | } | |
273 | return xstrdup(ntop); | |
274 | } | |
275 | ||
276 | char * | |
277 | get_peer_ipaddr(int sock) | |
278 | { | |
279 | char *p; | |
280 | ||
281 | if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL) | |
282 | return p; | |
283 | return xstrdup("UNKNOWN"); | |
284 | } | |
285 | ||
286 | char * | |
287 | get_local_ipaddr(int sock) | |
288 | { | |
289 | char *p; | |
290 | ||
291 | if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL) | |
292 | return p; | |
293 | return xstrdup("UNKNOWN"); | |
294 | } | |
295 | ||
296 | char * | |
297 | get_local_name(int sock) | |
298 | { | |
299 | return get_socket_address(sock, 0, NI_NAMEREQD); | |
300 | } | |
301 | ||
302 | /* | |
303 | * Returns the IP-address of the remote host as a string. The returned | |
304 | * string must not be freed. | |
305 | */ | |
306 | ||
307 | const char * | |
308 | get_remote_ipaddr(void) | |
309 | { | |
310 | static char *canonical_host_ip = NULL; | |
311 | ||
312 | /* Check whether we have cached the ipaddr. */ | |
313 | if (canonical_host_ip == NULL) { | |
314 | if (packet_connection_is_on_socket()) { | |
315 | canonical_host_ip = | |
316 | get_peer_ipaddr(packet_get_connection_in()); | |
317 | if (canonical_host_ip == NULL) | |
318 | cleanup_exit(255); | |
319 | } else { | |
320 | /* If not on socket, return UNKNOWN. */ | |
321 | canonical_host_ip = xstrdup("UNKNOWN"); | |
322 | } | |
323 | } | |
324 | return canonical_host_ip; | |
325 | } | |
326 | ||
327 | const char * | |
328 | get_remote_name_or_ip(u_int utmp_len, int use_dns) | |
329 | { | |
330 | static const char *remote = ""; | |
331 | if (utmp_len > 0) | |
332 | remote = get_canonical_hostname(use_dns); | |
333 | if (utmp_len == 0 || strlen(remote) > utmp_len) | |
334 | remote = get_remote_ipaddr(); | |
335 | return remote; | |
336 | } | |
337 | ||
338 | /* Returns the local/remote port for the socket. */ | |
339 | ||
340 | static int | |
341 | get_sock_port(int sock, int local) | |
342 | { | |
343 | struct sockaddr_storage from; | |
344 | socklen_t fromlen; | |
345 | char strport[NI_MAXSERV]; | |
346 | int r; | |
347 | ||
348 | /* Get IP address of client. */ | |
349 | fromlen = sizeof(from); | |
350 | memset(&from, 0, sizeof(from)); | |
351 | if (local) { | |
352 | if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) { | |
353 | error("getsockname failed: %.100s", strerror(errno)); | |
354 | return 0; | |
355 | } | |
356 | } else { | |
357 | if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { | |
358 | debug("getpeername failed: %.100s", strerror(errno)); | |
359 | return -1; | |
360 | } | |
361 | } | |
362 | ||
363 | /* Work around Linux IPv6 weirdness */ | |
364 | if (from.ss_family == AF_INET6) | |
365 | fromlen = sizeof(struct sockaddr_in6); | |
366 | ||
367 | /* Return port number. */ | |
368 | if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0, | |
369 | strport, sizeof(strport), NI_NUMERICSERV)) != 0) | |
370 | fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s", | |
371 | r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r)); | |
372 | return atoi(strport); | |
373 | } | |
374 | ||
375 | /* Returns remote/local port number for the current connection. */ | |
376 | ||
377 | static int | |
378 | get_port(int local) | |
379 | { | |
380 | /* | |
381 | * If the connection is not a socket, return 65535. This is | |
382 | * intentionally chosen to be an unprivileged port number. | |
383 | */ | |
384 | if (!packet_connection_is_on_socket()) | |
385 | return 65535; | |
386 | ||
387 | /* Get socket and return the port number. */ | |
388 | return get_sock_port(packet_get_connection_in(), local); | |
389 | } | |
390 | ||
391 | int | |
392 | get_peer_port(int sock) | |
393 | { | |
394 | return get_sock_port(sock, 0); | |
395 | } | |
396 | ||
397 | int | |
398 | get_remote_port(void) | |
399 | { | |
400 | static int port = -1; | |
401 | ||
402 | /* Cache to avoid getpeername() on a dead connection */ | |
403 | if (port == -1) | |
404 | port = get_port(0); | |
405 | ||
406 | return port; | |
407 | } | |
408 | ||
409 | int | |
410 | get_local_port(void) | |
411 | { | |
412 | return get_port(1); | |
413 | } |