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 1.34 2002/09/23 20:46:27 stevesk Exp $");
16 RCSID("$FreeBSD: src/crypto/openssh/canohost.c,v 1.1.1.1.2.7 2003/02/03 17:31:06 des Exp $");
23 static void check_ip_options(int, char *);
26 * Return the canonical name of the host at the other end of the socket. The
27 * caller should free the returned string with xfree.
31 get_remote_hostname(int socket, int verify_reverse_mapping)
33 struct sockaddr_storage from;
36 struct addrinfo hints, *ai, *aitop;
37 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
39 /* Get IP address of client. */
40 fromlen = sizeof(from);
41 memset(&from, 0, sizeof(from));
42 if (getpeername(socket, (struct sockaddr *) &from, &fromlen) < 0) {
43 debug("getpeername failed: %.100s", strerror(errno));
47 if (from.ss_family == AF_INET6) {
48 struct sockaddr_in6 *from6 = (struct sockaddr_in6 *)&from;
50 /* Detect IPv4 in IPv6 mapped address and convert it to */
51 /* plain (AF_INET) IPv4 address */
52 if (IN6_IS_ADDR_V4MAPPED(&from6->sin6_addr)) {
53 struct sockaddr_in *from4 = (struct sockaddr_in *)&from;
57 memcpy(&addr, ((char *)&from6->sin6_addr) + 12, sizeof(addr));
58 port = from6->sin6_port;
60 memset(&from, 0, sizeof(from));
62 from4->sin_family = AF_INET;
63 memcpy(&from4->sin_addr, &addr, sizeof(addr));
64 from4->sin_port = port;
69 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
70 NULL, 0, NI_NUMERICHOST) != 0)
71 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
73 if (from.ss_family == AF_INET)
74 check_ip_options(socket, ntop);
76 debug3("Trying to reverse map address %.100s.", ntop);
77 /* Map the IP address to a host name. */
78 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
79 NULL, 0, NI_NAMEREQD) != 0) {
80 /* Host name not found. Use ip address. */
82 log("Could not reverse map address %.100s.", ntop);
88 name[sizeof(name) - 1] = '\0';
90 * Convert it to all lowercase (which is expected by the rest
93 for (i = 0; name[i]; i++)
95 name[i] = tolower(name[i]);
97 if (!verify_reverse_mapping)
100 * Map it back to an IP address and check that the given
101 * address actually is an address of this host. This is
102 * necessary because anyone with access to a name server can
103 * define arbitrary names for an IP address. Mapping from
104 * name to IP address can be trusted better (but can still be
105 * fooled if the intruder has access to the name server of
108 memset(&hints, 0, sizeof(hints));
109 hints.ai_family = from.ss_family;
110 hints.ai_socktype = SOCK_STREAM;
111 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
112 log("reverse mapping checking getaddrinfo for %.700s "
113 "failed - POSSIBLE BREAKIN ATTEMPT!", name);
114 return xstrdup(ntop);
116 /* Look for the address from the list of addresses. */
117 for (ai = aitop; ai; ai = ai->ai_next) {
118 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
119 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
120 (strcmp(ntop, ntop2) == 0))
124 /* If we reached the end of the list, the address was not there. */
126 /* Address not found for the host name. */
127 log("Address %.100s maps to %.600s, but this does not "
128 "map back to the address - POSSIBLE BREAKIN ATTEMPT!",
130 return xstrdup(ntop);
132 return xstrdup(name);
136 * If IP options are supported, make sure there are none (log and
137 * disconnect them if any are found). Basically we are worried about
138 * source routing; it can be used to pretend you are somebody
139 * (ip-address) you are not. That itself may be "almost acceptable"
140 * under certain circumstances, but rhosts autentication is useless
141 * if source routing is accepted. Notice also that if we just dropped
142 * source routing here, the other side could use IP spoofing to do
143 * rest of the interaction and could still bypass security. So we
144 * exit here if we detect any IP options.
148 check_ip_options(int socket, char *ipaddr)
151 char text[sizeof(options) * 3 + 1];
152 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(socket, 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 log("Connection from %.100s with IP options:%.800s",
169 packet_disconnect("Connection from %.100s with IP options:%.800s",
175 * Return the canonical name of the host in the other side of the current
176 * connection. The host name is cached, so it is efficient to call this
181 get_canonical_hostname(int verify_reverse_mapping)
183 static char *canonical_host_name = NULL;
184 static int verify_reverse_mapping_done = 0;
186 /* Check if we have previously retrieved name with same option. */
187 if (canonical_host_name != NULL) {
188 if (verify_reverse_mapping_done != verify_reverse_mapping)
189 xfree(canonical_host_name);
191 return canonical_host_name;
194 /* Get the real hostname if socket; otherwise return UNKNOWN. */
195 if (packet_connection_is_on_socket())
196 canonical_host_name = get_remote_hostname(
197 packet_get_connection_in(), verify_reverse_mapping);
199 canonical_host_name = xstrdup("UNKNOWN");
201 verify_reverse_mapping_done = verify_reverse_mapping;
202 return canonical_host_name;
206 * Returns the remote IP-address of socket as a string. The returned
207 * string must be freed.
210 get_socket_address(int socket, int remote, int flags)
212 struct sockaddr_storage addr;
214 char ntop[NI_MAXHOST];
216 /* Get IP address of client. */
217 addrlen = sizeof(addr);
218 memset(&addr, 0, sizeof(addr));
221 if (getpeername(socket, (struct sockaddr *)&addr, &addrlen)
225 if (getsockname(socket, (struct sockaddr *)&addr, &addrlen)
229 /* Get the address in ascii. */
230 if (getnameinfo((struct sockaddr *)&addr, addrlen, ntop, sizeof(ntop),
231 NULL, 0, flags) != 0) {
232 error("get_socket_ipaddr: getnameinfo %d failed", flags);
235 return xstrdup(ntop);
239 get_peer_ipaddr(int socket)
243 if ((p = get_socket_address(socket, 1, NI_NUMERICHOST)) != NULL)
245 return xstrdup("UNKNOWN");
249 get_local_ipaddr(int socket)
253 if ((p = get_socket_address(socket, 0, NI_NUMERICHOST)) != NULL)
255 return xstrdup("UNKNOWN");
259 get_local_name(int socket)
261 return get_socket_address(socket, 0, NI_NAMEREQD);
265 * Returns the IP-address of the remote host as a string. The returned
266 * string must not be freed.
270 get_remote_ipaddr(void)
272 static char *canonical_host_ip = NULL;
274 /* Check whether we have cached the ipaddr. */
275 if (canonical_host_ip == NULL) {
276 if (packet_connection_is_on_socket()) {
278 get_peer_ipaddr(packet_get_connection_in());
279 if (canonical_host_ip == NULL)
282 /* If not on socket, return UNKNOWN. */
283 canonical_host_ip = xstrdup("UNKNOWN");
286 return canonical_host_ip;
290 get_remote_name_or_ip(u_int utmp_len, int verify_reverse_mapping)
292 static const char *remote = "";
294 remote = get_canonical_hostname(verify_reverse_mapping);
295 if (utmp_len == 0 || strlen(remote) > utmp_len)
296 remote = get_remote_ipaddr();
300 /* Returns the local/remote port for the socket. */
303 get_sock_port(int sock, int local)
305 struct sockaddr_storage from;
307 char strport[NI_MAXSERV];
309 /* Get IP address of client. */
310 fromlen = sizeof(from);
311 memset(&from, 0, sizeof(from));
313 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
314 error("getsockname failed: %.100s", strerror(errno));
318 if (getpeername(sock, (struct sockaddr *) & from, &fromlen) < 0) {
319 debug("getpeername failed: %.100s", strerror(errno));
323 /* Return port number. */
324 if (getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
325 strport, sizeof(strport), NI_NUMERICSERV) != 0)
326 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed");
327 return atoi(strport);
330 /* Returns remote/local port number for the current connection. */
336 * If the connection is not a socket, return 65535. This is
337 * intentionally chosen to be an unprivileged port number.
339 if (!packet_connection_is_on_socket())
342 /* Get socket and return the port number. */
343 return get_sock_port(packet_get_connection_in(), local);
347 get_peer_port(int sock)
349 return get_sock_port(sock, 0);
353 get_remote_port(void)