1 /* $OpenBSD: canohost.c,v 1.70 2014/01/19 04:17:29 dtucker 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>
20 #include <netinet/in.h>
21 #include <arpa/inet.h>
37 static void check_ip_options(int, char *);
38 static char *canonical_host_ip = NULL;
39 static int cached_port = -1;
42 * Return the canonical name of the host at the other end of the socket. The
43 * caller should free the returned string.
47 get_remote_hostname(int sock, int use_dns)
49 struct sockaddr_storage from;
51 struct addrinfo hints, *ai, *aitop;
52 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
54 /* Get IP address of client. */
55 fromlen = sizeof(from);
56 memset(&from, 0, sizeof(from));
57 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
58 debug("getpeername failed: %.100s", strerror(errno));
62 if (from.ss_family == AF_INET)
63 check_ip_options(sock, ntop);
65 ipv64_normalise_mapped(&from, &fromlen);
67 if (from.ss_family == AF_INET6)
68 fromlen = sizeof(struct sockaddr_in6);
70 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
71 NULL, 0, NI_NUMERICHOST) != 0)
72 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
77 debug3("Trying to reverse map address %.100s.", ntop);
78 /* Map the IP address to a host name. */
79 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
80 NULL, 0, NI_NAMEREQD) != 0) {
81 /* Host name not found. Use ip address. */
86 * if reverse lookup result looks like a numeric hostname,
87 * someone is trying to trick us by PTR record like following:
88 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
90 memset(&hints, 0, sizeof(hints));
91 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
92 hints.ai_flags = AI_NUMERICHOST;
93 if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
94 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
100 /* Names are stores in lowercase. */
104 * Map it back to an IP address and check that the given
105 * address actually is an address of this host. This is
106 * necessary because anyone with access to a name server can
107 * define arbitrary names for an IP address. Mapping from
108 * name to IP address can be trusted better (but can still be
109 * fooled if the intruder has access to the name server of
112 memset(&hints, 0, sizeof(hints));
113 hints.ai_family = from.ss_family;
114 hints.ai_socktype = SOCK_STREAM;
115 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
116 logit("reverse mapping checking getaddrinfo for %.700s "
117 "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop);
118 return xstrdup(ntop);
120 /* Look for the address from the list of addresses. */
121 for (ai = aitop; ai; ai = ai->ai_next) {
122 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
123 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
124 (strcmp(ntop, ntop2) == 0))
128 /* If we reached the end of the list, the address was not there. */
130 /* Address not found for the host name. */
131 logit("Address %.100s maps to %.600s, but this does not "
132 "map back to the address - POSSIBLE BREAK-IN ATTEMPT!",
134 return xstrdup(ntop);
136 return xstrdup(name);
140 * If IP options are supported, make sure there are none (log and
141 * disconnect them if any are found). Basically we are worried about
142 * source routing; it can be used to pretend you are somebody
143 * (ip-address) you are not. That itself may be "almost acceptable"
144 * under certain circumstances, but rhosts autentication is useless
145 * if source routing is accepted. Notice also that if we just dropped
146 * source routing here, the other side could use IP spoofing to do
147 * rest of the interaction and could still bypass security. So we
148 * exit here if we detect any IP options.
152 check_ip_options(int sock, char *ipaddr)
156 char text[sizeof(options) * 3 + 1];
157 socklen_t option_size, i;
161 if ((ip = getprotobyname("ip")) != NULL)
162 ipproto = ip->p_proto;
164 ipproto = IPPROTO_IP;
165 option_size = sizeof(options);
166 if (getsockopt(sock, ipproto, IP_OPTIONS, options,
167 &option_size) >= 0 && option_size != 0) {
169 for (i = 0; i < option_size; i++)
170 snprintf(text + i*3, sizeof(text) - i*3,
171 " %2.2x", options[i]);
172 fatal("Connection from %.100s with IP options:%.800s",
175 #endif /* IP_OPTIONS */
179 ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
181 struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr;
182 struct sockaddr_in *a4 = (struct sockaddr_in *)addr;
183 struct in_addr inaddr;
186 if (addr->ss_family != AF_INET6 ||
187 !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr))
190 debug3("Normalising mapped IPv4 in IPv6 address");
192 memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr));
193 port = a6->sin6_port;
195 memset(a4, 0, sizeof(*a4));
197 a4->sin_family = AF_INET;
199 memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr));
204 * Return the canonical name of the host in the other side of the current
205 * connection. The host name is cached, so it is efficient to call this
210 get_canonical_hostname(int use_dns)
213 static char *canonical_host_name = NULL;
214 static char *remote_ip = NULL;
216 /* Check if we have previously retrieved name with same option. */
217 if (use_dns && canonical_host_name != NULL)
218 return canonical_host_name;
219 if (!use_dns && remote_ip != NULL)
222 /* Get the real hostname if socket; otherwise return UNKNOWN. */
223 if (packet_connection_is_on_socket())
224 host = get_remote_hostname(packet_get_connection_in(), use_dns);
229 canonical_host_name = host;
236 * Returns the local/remote IP-address/hostname of socket as a string.
237 * The returned string must be freed.
240 get_socket_address(int sock, int remote, int flags)
242 struct sockaddr_storage addr;
244 char ntop[NI_MAXHOST];
247 /* Get IP address of client. */
248 addrlen = sizeof(addr);
249 memset(&addr, 0, sizeof(addr));
252 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen)
256 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen)
261 /* Work around Linux IPv6 weirdness */
262 if (addr.ss_family == AF_INET6)
263 addrlen = sizeof(struct sockaddr_in6);
265 ipv64_normalise_mapped(&addr, &addrlen);
267 /* Get the address in ascii. */
268 if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
269 sizeof(ntop), NULL, 0, flags)) != 0) {
270 error("get_socket_address: getnameinfo %d failed: %s", flags,
271 ssh_gai_strerror(r));
274 return xstrdup(ntop);
278 get_peer_ipaddr(int sock)
282 if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL)
284 return xstrdup("UNKNOWN");
288 get_local_ipaddr(int sock)
292 if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL)
294 return xstrdup("UNKNOWN");
298 get_local_name(int fd)
300 char *host, myname[NI_MAXHOST];
302 /* Assume we were passed a socket */
303 if ((host = get_socket_address(fd, 0, NI_NAMEREQD)) != NULL)
306 /* Handle the case where we were passed a pipe */
307 if (gethostname(myname, sizeof(myname)) == -1) {
308 verbose("get_local_name: gethostname: %s", strerror(errno));
310 host = xstrdup(myname);
317 clear_cached_addr(void)
319 free(canonical_host_ip);
320 canonical_host_ip = NULL;
325 * Returns the IP-address of the remote host as a string. The returned
326 * string must not be freed.
330 get_remote_ipaddr(void)
332 /* Check whether we have cached the ipaddr. */
333 if (canonical_host_ip == NULL) {
334 if (packet_connection_is_on_socket()) {
336 get_peer_ipaddr(packet_get_connection_in());
337 if (canonical_host_ip == NULL)
340 /* If not on socket, return UNKNOWN. */
341 canonical_host_ip = xstrdup("UNKNOWN");
344 return canonical_host_ip;
348 get_remote_name_or_ip(u_int utmp_len, int use_dns)
350 static const char *remote = "";
352 remote = get_canonical_hostname(use_dns);
353 if (utmp_len == 0 || strlen(remote) > utmp_len)
354 remote = get_remote_ipaddr();
358 /* Returns the local/remote port for the socket. */
361 get_sock_port(int sock, int local)
363 struct sockaddr_storage from;
365 char strport[NI_MAXSERV];
368 /* Get IP address of client. */
369 fromlen = sizeof(from);
370 memset(&from, 0, sizeof(from));
372 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
373 error("getsockname failed: %.100s", strerror(errno));
377 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
378 debug("getpeername failed: %.100s", strerror(errno));
383 /* Work around Linux IPv6 weirdness */
384 if (from.ss_family == AF_INET6)
385 fromlen = sizeof(struct sockaddr_in6);
387 /* Return port number. */
388 if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
389 strport, sizeof(strport), NI_NUMERICSERV)) != 0)
390 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s",
391 ssh_gai_strerror(r));
392 return atoi(strport);
395 /* Returns remote/local port number for the current connection. */
401 * If the connection is not a socket, return 65535. This is
402 * intentionally chosen to be an unprivileged port number.
404 if (!packet_connection_is_on_socket())
407 /* Get socket and return the port number. */
408 return get_sock_port(packet_get_connection_in(), local);
412 get_peer_port(int sock)
414 return get_sock_port(sock, 0);
418 get_remote_port(void)
420 /* Cache to avoid getpeername() on a dead connection */
421 if (cached_port == -1)
422 cached_port = get_port(0);