1 /* $OpenBSD: canohost.c,v 1.71 2014/07/15 15:54:14 millert 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/types.h>
18 #include <sys/socket.h>
21 #include <netinet/in.h>
22 #include <arpa/inet.h>
38 static void check_ip_options(int, char *);
39 static char *canonical_host_ip = NULL;
40 static int cached_port = -1;
43 * Return the canonical name of the host at the other end of the socket. The
44 * caller should free the returned string.
48 get_remote_hostname(int sock, int use_dns)
50 struct sockaddr_storage from;
52 struct addrinfo hints, *ai, *aitop;
53 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
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));
63 if (from.ss_family == AF_INET)
64 check_ip_options(sock, ntop);
66 ipv64_normalise_mapped(&from, &fromlen);
68 if (from.ss_family == AF_INET6)
69 fromlen = sizeof(struct sockaddr_in6);
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");
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. */
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
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",
101 /* Names are stores in lowercase. */
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
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);
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))
129 /* If we reached the end of the list, the address was not there. */
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!",
135 return xstrdup(ntop);
137 return xstrdup(name);
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.
153 check_ip_options(int sock, char *ipaddr)
157 char text[sizeof(options) * 3 + 1];
158 socklen_t option_size, i;
162 if ((ip = getprotobyname("ip")) != NULL)
163 ipproto = ip->p_proto;
165 ipproto = IPPROTO_IP;
166 option_size = sizeof(options);
167 if (getsockopt(sock, ipproto, IP_OPTIONS, options,
168 &option_size) >= 0 && option_size != 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",
176 #endif /* IP_OPTIONS */
180 ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
182 struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr;
183 struct sockaddr_in *a4 = (struct sockaddr_in *)addr;
184 struct in_addr inaddr;
187 if (addr->ss_family != AF_INET6 ||
188 !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr))
191 debug3("Normalising mapped IPv4 in IPv6 address");
193 memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr));
194 port = a6->sin6_port;
196 memset(a4, 0, sizeof(*a4));
198 a4->sin_family = AF_INET;
200 memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr));
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
211 get_canonical_hostname(int use_dns)
214 static char *canonical_host_name = NULL;
215 static char *remote_ip = NULL;
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)
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);
230 canonical_host_name = host;
237 * Returns the local/remote IP-address/hostname of socket as a string.
238 * The returned string must be freed.
241 get_socket_address(int sock, int remote, int flags)
243 struct sockaddr_storage addr;
245 char ntop[NI_MAXHOST];
248 /* Get IP address of client. */
249 addrlen = sizeof(addr);
250 memset(&addr, 0, sizeof(addr));
253 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen)
257 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen)
262 /* Work around Linux IPv6 weirdness */
263 if (addr.ss_family == AF_INET6)
264 addrlen = sizeof(struct sockaddr_in6);
266 if (addr.ss_family == AF_UNIX) {
267 /* Get the Unix domain socket path. */
268 return xstrdup(((struct sockaddr_un *)&addr)->sun_path);
271 ipv64_normalise_mapped(&addr, &addrlen);
273 /* Get the address in ascii. */
274 if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
275 sizeof(ntop), NULL, 0, flags)) != 0) {
276 error("get_socket_address: getnameinfo %d failed: %s", flags,
277 ssh_gai_strerror(r));
280 return xstrdup(ntop);
284 get_peer_ipaddr(int sock)
288 if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL)
290 return xstrdup("UNKNOWN");
294 get_local_ipaddr(int sock)
298 if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL)
300 return xstrdup("UNKNOWN");
304 get_local_name(int fd)
306 char *host, myname[NI_MAXHOST];
308 /* Assume we were passed a socket */
309 if ((host = get_socket_address(fd, 0, NI_NAMEREQD)) != NULL)
312 /* Handle the case where we were passed a pipe */
313 if (gethostname(myname, sizeof(myname)) == -1) {
314 verbose("get_local_name: gethostname: %s", strerror(errno));
316 host = xstrdup(myname);
323 clear_cached_addr(void)
325 free(canonical_host_ip);
326 canonical_host_ip = NULL;
331 * Returns the IP-address of the remote host as a string. The returned
332 * string must not be freed.
336 get_remote_ipaddr(void)
338 /* Check whether we have cached the ipaddr. */
339 if (canonical_host_ip == NULL) {
340 if (packet_connection_is_on_socket()) {
342 get_peer_ipaddr(packet_get_connection_in());
343 if (canonical_host_ip == NULL)
346 /* If not on socket, return UNKNOWN. */
347 canonical_host_ip = xstrdup("UNKNOWN");
350 return canonical_host_ip;
354 get_remote_name_or_ip(u_int utmp_len, int use_dns)
356 static const char *remote = "";
358 remote = get_canonical_hostname(use_dns);
359 if (utmp_len == 0 || strlen(remote) > utmp_len)
360 remote = get_remote_ipaddr();
364 /* Returns the local/remote port for the socket. */
367 get_sock_port(int sock, int local)
369 struct sockaddr_storage from;
371 char strport[NI_MAXSERV];
374 /* Get IP address of client. */
375 fromlen = sizeof(from);
376 memset(&from, 0, sizeof(from));
378 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
379 error("getsockname failed: %.100s", strerror(errno));
383 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
384 debug("getpeername failed: %.100s", strerror(errno));
389 /* Work around Linux IPv6 weirdness */
390 if (from.ss_family == AF_INET6)
391 fromlen = sizeof(struct sockaddr_in6);
393 /* Unix domain sockets don't have a port number. */
394 if (from.ss_family == AF_UNIX)
397 /* Return port number. */
398 if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
399 strport, sizeof(strport), NI_NUMERICSERV)) != 0)
400 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s",
401 ssh_gai_strerror(r));
402 return atoi(strport);
405 /* Returns remote/local port number for the current connection. */
411 * If the connection is not a socket, return 65535. This is
412 * intentionally chosen to be an unprivileged port number.
414 if (!packet_connection_is_on_socket())
417 /* Get socket and return the port number. */
418 return get_sock_port(packet_get_connection_in(), local);
422 get_peer_port(int sock)
424 return get_sock_port(sock, 0);
428 get_remote_port(void)
430 /* Cache to avoid getpeername() on a dead connection */
431 if (cached_port == -1)
432 cached_port = get_port(0);