1 /* $OpenBSD: canohost.c,v 1.58 2006/07/22 20:48:22 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/types.h>
18 #include <sys/socket.h>
20 #include <netinet/in.h>
32 static void check_ip_options(int, char *);
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.
40 get_remote_hostname(int sock, int use_dns)
42 struct sockaddr_storage from;
45 struct addrinfo hints, *ai, *aitop;
46 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
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));
56 if (from.ss_family == AF_INET)
57 check_ip_options(sock, ntop);
59 ipv64_normalise_mapped(&from, &fromlen);
61 if (from.ss_family == AF_INET6)
62 fromlen = sizeof(struct sockaddr_in6);
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");
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. */
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
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",
95 * Convert it to all lowercase (which is expected by the rest
98 for (i = 0; name[i]; i++)
100 name[i] = (char)tolower(name[i]);
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
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);
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))
126 /* If we reached the end of the list, the address was not there. */
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!",
132 return xstrdup(ntop);
134 return xstrdup(name);
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.
150 check_ip_options(int sock, char *ipaddr)
154 char text[sizeof(options) * 3 + 1];
155 socklen_t option_size;
160 if ((ip = getprotobyname("ip")) != NULL)
161 ipproto = ip->p_proto;
163 ipproto = IPPROTO_IP;
164 option_size = sizeof(options);
165 if (getsockopt(sock, ipproto, IP_OPTIONS, options,
166 &option_size) >= 0 && option_size != 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",
174 #endif /* IP_OPTIONS */
178 ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
180 struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr;
181 struct sockaddr_in *a4 = (struct sockaddr_in *)addr;
182 struct in_addr inaddr;
185 if (addr->ss_family != AF_INET6 ||
186 !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr))
189 debug3("Normalising mapped IPv4 in IPv6 address");
191 memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr));
192 port = a6->sin6_port;
194 memset(addr, 0, sizeof(*a4));
196 a4->sin_family = AF_INET;
198 memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr));
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
209 get_canonical_hostname(int use_dns)
212 static char *canonical_host_name = NULL;
213 static char *remote_ip = NULL;
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)
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);
228 canonical_host_name = host;
235 * Returns the local/remote IP-address/hostname of socket as a string.
236 * The returned string must be freed.
239 get_socket_address(int sock, int remote, int flags)
241 struct sockaddr_storage addr;
243 char ntop[NI_MAXHOST];
246 /* Get IP address of client. */
247 addrlen = sizeof(addr);
248 memset(&addr, 0, sizeof(addr));
251 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen)
255 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen)
260 /* Work around Linux IPv6 weirdness */
261 if (addr.ss_family == AF_INET6)
262 addrlen = sizeof(struct sockaddr_in6);
264 ipv64_normalise_mapped(&addr, &addrlen);
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));
273 return xstrdup(ntop);
277 get_peer_ipaddr(int sock)
281 if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL)
283 return xstrdup("UNKNOWN");
287 get_local_ipaddr(int sock)
291 if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL)
293 return xstrdup("UNKNOWN");
297 get_local_name(int sock)
299 return get_socket_address(sock, 0, NI_NAMEREQD);
303 * Returns the IP-address of the remote host as a string. The returned
304 * string must not be freed.
308 get_remote_ipaddr(void)
310 static char *canonical_host_ip = NULL;
312 /* Check whether we have cached the ipaddr. */
313 if (canonical_host_ip == NULL) {
314 if (packet_connection_is_on_socket()) {
316 get_peer_ipaddr(packet_get_connection_in());
317 if (canonical_host_ip == NULL)
320 /* If not on socket, return UNKNOWN. */
321 canonical_host_ip = xstrdup("UNKNOWN");
324 return canonical_host_ip;
328 get_remote_name_or_ip(u_int utmp_len, int use_dns)
330 static const char *remote = "";
332 remote = get_canonical_hostname(use_dns);
333 if (utmp_len == 0 || strlen(remote) > utmp_len)
334 remote = get_remote_ipaddr();
338 /* Returns the local/remote port for the socket. */
341 get_sock_port(int sock, int local)
343 struct sockaddr_storage from;
345 char strport[NI_MAXSERV];
348 /* Get IP address of client. */
349 fromlen = sizeof(from);
350 memset(&from, 0, sizeof(from));
352 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
353 error("getsockname failed: %.100s", strerror(errno));
357 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
358 debug("getpeername failed: %.100s", strerror(errno));
363 /* Work around Linux IPv6 weirdness */
364 if (from.ss_family == AF_INET6)
365 fromlen = sizeof(struct sockaddr_in6);
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);
375 /* Returns remote/local port number for the current connection. */
381 * If the connection is not a socket, return 65535. This is
382 * intentionally chosen to be an unprivileged port number.
384 if (!packet_connection_is_on_socket())
387 /* Get socket and return the port number. */
388 return get_sock_port(packet_get_connection_in(), local);
392 get_peer_port(int sock)
394 return get_sock_port(sock, 0);
398 get_remote_port(void)
400 static int port = -1;
402 /* Cache to avoid getpeername() on a dead connection */