1 /* $OpenBSD: canohost.c,v 1.54 2006/07/05 02:42:09 stevesk Exp $ */
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * Functions for returning the canonical host name of the remote site.
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".
17 #include <sys/socket.h>
19 #include <netinet/in.h>
28 static void check_ip_options(int, char *);
31 * Return the canonical name of the host at the other end of the socket. The
32 * caller should free the returned string with xfree.
36 get_remote_hostname(int sock, int use_dns)
38 struct sockaddr_storage from;
41 struct addrinfo hints, *ai, *aitop;
42 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
44 /* Get IP address of client. */
45 fromlen = sizeof(from);
46 memset(&from, 0, sizeof(from));
47 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
48 debug("getpeername failed: %.100s", strerror(errno));
52 if (from.ss_family == AF_INET)
53 check_ip_options(sock, ntop);
55 ipv64_normalise_mapped(&from, &fromlen);
57 if (from.ss_family == AF_INET6)
58 fromlen = sizeof(struct sockaddr_in6);
60 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
61 NULL, 0, NI_NUMERICHOST) != 0)
62 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
67 debug3("Trying to reverse map address %.100s.", ntop);
68 /* Map the IP address to a host name. */
69 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
70 NULL, 0, NI_NAMEREQD) != 0) {
71 /* Host name not found. Use ip address. */
76 * if reverse lookup result looks like a numeric hostname,
77 * someone is trying to trick us by PTR record like following:
78 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
80 memset(&hints, 0, sizeof(hints));
81 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
82 hints.ai_flags = AI_NUMERICHOST;
83 if (getaddrinfo(name, "0", &hints, &ai) == 0) {
84 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
91 * Convert it to all lowercase (which is expected by the rest
94 for (i = 0; name[i]; i++)
96 name[i] = (char)tolower(name[i]);
98 * Map it back to an IP address and check that the given
99 * address actually is an address of this host. This is
100 * necessary because anyone with access to a name server can
101 * define arbitrary names for an IP address. Mapping from
102 * name to IP address can be trusted better (but can still be
103 * fooled if the intruder has access to the name server of
106 memset(&hints, 0, sizeof(hints));
107 hints.ai_family = from.ss_family;
108 hints.ai_socktype = SOCK_STREAM;
109 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
110 logit("reverse mapping checking getaddrinfo for %.700s "
111 "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop);
112 return xstrdup(ntop);
114 /* Look for the address from the list of addresses. */
115 for (ai = aitop; ai; ai = ai->ai_next) {
116 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
117 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
118 (strcmp(ntop, ntop2) == 0))
122 /* If we reached the end of the list, the address was not there. */
124 /* Address not found for the host name. */
125 logit("Address %.100s maps to %.600s, but this does not "
126 "map back to the address - POSSIBLE BREAK-IN ATTEMPT!",
128 return xstrdup(ntop);
130 return xstrdup(name);
134 * If IP options are supported, make sure there are none (log and
135 * disconnect them if any are found). Basically we are worried about
136 * source routing; it can be used to pretend you are somebody
137 * (ip-address) you are not. That itself may be "almost acceptable"
138 * under certain circumstances, but rhosts autentication is useless
139 * if source routing is accepted. Notice also that if we just dropped
140 * source routing here, the other side could use IP spoofing to do
141 * rest of the interaction and could still bypass security. So we
142 * exit here if we detect any IP options.
146 check_ip_options(int sock, char *ipaddr)
150 char text[sizeof(options) * 3 + 1];
151 socklen_t option_size;
156 if ((ip = getprotobyname("ip")) != NULL)
157 ipproto = ip->p_proto;
159 ipproto = IPPROTO_IP;
160 option_size = sizeof(options);
161 if (getsockopt(sock, ipproto, IP_OPTIONS, options,
162 &option_size) >= 0 && option_size != 0) {
164 for (i = 0; i < option_size; i++)
165 snprintf(text + i*3, sizeof(text) - i*3,
166 " %2.2x", options[i]);
167 fatal("Connection from %.100s with IP options:%.800s",
170 #endif /* IP_OPTIONS */
174 ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
176 struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr;
177 struct sockaddr_in *a4 = (struct sockaddr_in *)addr;
178 struct in_addr inaddr;
181 if (addr->ss_family != AF_INET6 ||
182 !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr))
185 debug3("Normalising mapped IPv4 in IPv6 address");
187 memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr));
188 port = a6->sin6_port;
190 memset(addr, 0, sizeof(*a4));
192 a4->sin_family = AF_INET;
194 memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr));
199 * Return the canonical name of the host in the other side of the current
200 * connection. The host name is cached, so it is efficient to call this
205 get_canonical_hostname(int use_dns)
208 static char *canonical_host_name = NULL;
209 static char *remote_ip = NULL;
211 /* Check if we have previously retrieved name with same option. */
212 if (use_dns && canonical_host_name != NULL)
213 return canonical_host_name;
214 if (!use_dns && remote_ip != NULL)
217 /* Get the real hostname if socket; otherwise return UNKNOWN. */
218 if (packet_connection_is_on_socket())
219 host = get_remote_hostname(packet_get_connection_in(), use_dns);
224 canonical_host_name = host;
231 * Returns the local/remote IP-address/hostname of socket as a string.
232 * The returned string must be freed.
235 get_socket_address(int sock, int remote, int flags)
237 struct sockaddr_storage addr;
239 char ntop[NI_MAXHOST];
242 /* Get IP address of client. */
243 addrlen = sizeof(addr);
244 memset(&addr, 0, sizeof(addr));
247 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen)
251 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen)
256 /* Work around Linux IPv6 weirdness */
257 if (addr.ss_family == AF_INET6)
258 addrlen = sizeof(struct sockaddr_in6);
260 ipv64_normalise_mapped(&addr, &addrlen);
262 /* Get the address in ascii. */
263 if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
264 sizeof(ntop), NULL, 0, flags)) != 0) {
265 error("get_socket_address: getnameinfo %d failed: %s", flags,
266 r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r));
269 return xstrdup(ntop);
273 get_peer_ipaddr(int sock)
277 if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL)
279 return xstrdup("UNKNOWN");
283 get_local_ipaddr(int sock)
287 if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL)
289 return xstrdup("UNKNOWN");
293 get_local_name(int sock)
295 return get_socket_address(sock, 0, NI_NAMEREQD);
299 * Returns the IP-address of the remote host as a string. The returned
300 * string must not be freed.
304 get_remote_ipaddr(void)
306 static char *canonical_host_ip = NULL;
308 /* Check whether we have cached the ipaddr. */
309 if (canonical_host_ip == NULL) {
310 if (packet_connection_is_on_socket()) {
312 get_peer_ipaddr(packet_get_connection_in());
313 if (canonical_host_ip == NULL)
316 /* If not on socket, return UNKNOWN. */
317 canonical_host_ip = xstrdup("UNKNOWN");
320 return canonical_host_ip;
324 get_remote_name_or_ip(u_int utmp_len, int use_dns)
326 static const char *remote = "";
328 remote = get_canonical_hostname(use_dns);
329 if (utmp_len == 0 || strlen(remote) > utmp_len)
330 remote = get_remote_ipaddr();
334 /* Returns the local/remote port for the socket. */
337 get_sock_port(int sock, int local)
339 struct sockaddr_storage from;
341 char strport[NI_MAXSERV];
344 /* Get IP address of client. */
345 fromlen = sizeof(from);
346 memset(&from, 0, sizeof(from));
348 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
349 error("getsockname failed: %.100s", strerror(errno));
353 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
354 debug("getpeername failed: %.100s", strerror(errno));
359 /* Work around Linux IPv6 weirdness */
360 if (from.ss_family == AF_INET6)
361 fromlen = sizeof(struct sockaddr_in6);
363 /* Return port number. */
364 if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
365 strport, sizeof(strport), NI_NUMERICSERV)) != 0)
366 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s",
367 r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r));
368 return atoi(strport);
371 /* Returns remote/local port number for the current connection. */
377 * If the connection is not a socket, return 65535. This is
378 * intentionally chosen to be an unprivileged port number.
380 if (!packet_connection_is_on_socket())
383 /* Get socket and return the port number. */
384 return get_sock_port(packet_get_connection_in(), local);
388 get_peer_port(int sock)
390 return get_sock_port(sock, 0);
394 get_remote_port(void)
396 static int port = -1;
398 /* Cache to avoid getpeername() on a dead connection */