2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * Functions for returning the canonical host name of the remote site.
7 * As far as I am concerned, the code I have written for this software
8 * can be used freely for any purpose. Any derived versions of this
9 * software must be clearly marked as such, and if the derived work is
10 * incompatible with the protocol description in the RFC file, it must be
11 * called by a name other than "ssh" or "Secure Shell".
15 RCSID("$OpenBSD: canohost.c,v 1.35 2002/11/26 02:38:54 stevesk Exp $");
22 static void check_ip_options(int, char *);
25 * Return the canonical name of the host at the other end of the socket. The
26 * caller should free the returned string with xfree.
30 get_remote_hostname(int socket, int verify_reverse_mapping)
32 struct sockaddr_storage from;
35 struct addrinfo hints, *ai, *aitop;
36 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
38 /* Get IP address of client. */
39 fromlen = sizeof(from);
40 memset(&from, 0, sizeof(from));
41 if (getpeername(socket, (struct sockaddr *)&from, &fromlen) < 0) {
42 debug("getpeername failed: %.100s", strerror(errno));
46 if (from.ss_family == AF_INET6) {
47 struct sockaddr_in6 *from6 = (struct sockaddr_in6 *)&from;
49 /* Detect IPv4 in IPv6 mapped address and convert it to */
50 /* plain (AF_INET) IPv4 address */
51 if (IN6_IS_ADDR_V4MAPPED(&from6->sin6_addr)) {
52 struct sockaddr_in *from4 = (struct sockaddr_in *)&from;
56 memcpy(&addr, ((char *)&from6->sin6_addr) + 12, sizeof(addr));
57 port = from6->sin6_port;
59 memset(&from, 0, sizeof(from));
61 from4->sin_family = AF_INET;
62 fromlen = sizeof(*from4);
63 memcpy(&from4->sin_addr, &addr, sizeof(addr));
64 from4->sin_port = port;
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");
75 if (from.ss_family == AF_INET)
76 check_ip_options(socket, ntop);
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. */
84 log("Could not reverse map address %.100s.", ntop);
90 name[sizeof(name) - 1] = '\0';
92 * Convert it to all lowercase (which is expected by the rest
95 for (i = 0; name[i]; i++)
97 name[i] = tolower(name[i]);
99 if (!verify_reverse_mapping)
100 return xstrdup(name);
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 log("reverse mapping checking getaddrinfo for %.700s "
115 "failed - POSSIBLE BREAKIN ATTEMPT!", name);
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 log("Address %.100s maps to %.600s, but this does not "
130 "map back to the address - POSSIBLE BREAKIN 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 socket, char *ipaddr)
153 char text[sizeof(options) * 3 + 1];
154 socklen_t option_size;
158 if ((ip = getprotobyname("ip")) != NULL)
159 ipproto = ip->p_proto;
161 ipproto = IPPROTO_IP;
162 option_size = sizeof(options);
163 if (getsockopt(socket, ipproto, IP_OPTIONS, options,
164 &option_size) >= 0 && option_size != 0) {
166 for (i = 0; i < option_size; i++)
167 snprintf(text + i*3, sizeof(text) - i*3,
168 " %2.2x", options[i]);
169 log("Connection from %.100s with IP options:%.800s",
171 packet_disconnect("Connection from %.100s with IP options:%.800s",
177 * Return the canonical name of the host in the other side of the current
178 * connection. The host name is cached, so it is efficient to call this
183 get_canonical_hostname(int verify_reverse_mapping)
185 static char *canonical_host_name = NULL;
186 static int verify_reverse_mapping_done = 0;
188 /* Check if we have previously retrieved name with same option. */
189 if (canonical_host_name != NULL) {
190 if (verify_reverse_mapping_done != verify_reverse_mapping)
191 xfree(canonical_host_name);
193 return canonical_host_name;
196 /* Get the real hostname if socket; otherwise return UNKNOWN. */
197 if (packet_connection_is_on_socket())
198 canonical_host_name = get_remote_hostname(
199 packet_get_connection_in(), verify_reverse_mapping);
201 canonical_host_name = xstrdup("UNKNOWN");
203 verify_reverse_mapping_done = verify_reverse_mapping;
204 return canonical_host_name;
208 * Returns the local/remote IP-address/hostname of socket as a string.
209 * The returned string must be freed.
212 get_socket_address(int socket, int remote, int flags)
214 struct sockaddr_storage addr;
216 char ntop[NI_MAXHOST];
218 /* Get IP address of client. */
219 addrlen = sizeof(addr);
220 memset(&addr, 0, sizeof(addr));
223 if (getpeername(socket, (struct sockaddr *)&addr, &addrlen)
227 if (getsockname(socket, (struct sockaddr *)&addr, &addrlen)
232 /* Work around Linux IPv6 weirdness */
233 if (addr.ss_family == AF_INET6)
234 addrlen = sizeof(struct sockaddr_in6);
236 /* Get the address in ascii. */
237 if (getnameinfo((struct sockaddr *)&addr, addrlen, ntop, sizeof(ntop),
238 NULL, 0, flags) != 0) {
239 error("get_socket_address: getnameinfo %d failed", flags);
242 return xstrdup(ntop);
246 get_peer_ipaddr(int socket)
250 if ((p = get_socket_address(socket, 1, NI_NUMERICHOST)) != NULL)
252 return xstrdup("UNKNOWN");
256 get_local_ipaddr(int socket)
260 if ((p = get_socket_address(socket, 0, NI_NUMERICHOST)) != NULL)
262 return xstrdup("UNKNOWN");
266 get_local_name(int socket)
268 return get_socket_address(socket, 0, NI_NAMEREQD);
272 * Returns the IP-address of the remote host as a string. The returned
273 * string must not be freed.
277 get_remote_ipaddr(void)
279 static char *canonical_host_ip = NULL;
281 /* Check whether we have cached the ipaddr. */
282 if (canonical_host_ip == NULL) {
283 if (packet_connection_is_on_socket()) {
285 get_peer_ipaddr(packet_get_connection_in());
286 if (canonical_host_ip == NULL)
289 /* If not on socket, return UNKNOWN. */
290 canonical_host_ip = xstrdup("UNKNOWN");
293 return canonical_host_ip;
297 get_remote_name_or_ip(u_int utmp_len, int verify_reverse_mapping)
299 static const char *remote = "";
301 remote = get_canonical_hostname(verify_reverse_mapping);
302 if (utmp_len == 0 || strlen(remote) > utmp_len)
303 remote = get_remote_ipaddr();
307 /* Returns the local/remote port for the socket. */
310 get_sock_port(int sock, int local)
312 struct sockaddr_storage from;
314 char strport[NI_MAXSERV];
316 /* Get IP address of client. */
317 fromlen = sizeof(from);
318 memset(&from, 0, sizeof(from));
320 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
321 error("getsockname failed: %.100s", strerror(errno));
325 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
326 debug("getpeername failed: %.100s", strerror(errno));
331 /* Work around Linux IPv6 weirdness */
332 if (from.ss_family == AF_INET6)
333 fromlen = sizeof(struct sockaddr_in6);
335 /* Return port number. */
336 if (getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
337 strport, sizeof(strport), NI_NUMERICSERV) != 0)
338 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed");
339 return atoi(strport);
342 /* Returns remote/local port number for the current connection. */
348 * If the connection is not a socket, return 65535. This is
349 * intentionally chosen to be an unprivileged port number.
351 if (!packet_connection_is_on_socket())
354 /* Get socket and return the port number. */
355 return get_sock_port(packet_get_connection_in(), local);
359 get_peer_port(int sock)
361 return get_sock_port(sock, 0);
365 get_remote_port(void)