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 $");
17 RCSID("$DragonFly: src/crypto/openssh/Attic/canohost.c,v 1.2 2003/06/17 04:24:36 dillon Exp $");
24 static void check_ip_options(int, char *);
27 * Return the canonical name of the host at the other end of the socket. The
28 * caller should free the returned string with xfree.
32 get_remote_hostname(int socket, int verify_reverse_mapping)
34 struct sockaddr_storage from;
37 struct addrinfo hints, *ai, *aitop;
38 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
40 /* Get IP address of client. */
41 fromlen = sizeof(from);
42 memset(&from, 0, sizeof(from));
43 if (getpeername(socket, (struct sockaddr *) &from, &fromlen) < 0) {
44 debug("getpeername failed: %.100s", strerror(errno));
48 if (from.ss_family == AF_INET6) {
49 struct sockaddr_in6 *from6 = (struct sockaddr_in6 *)&from;
51 /* Detect IPv4 in IPv6 mapped address and convert it to */
52 /* plain (AF_INET) IPv4 address */
53 if (IN6_IS_ADDR_V4MAPPED(&from6->sin6_addr)) {
54 struct sockaddr_in *from4 = (struct sockaddr_in *)&from;
58 memcpy(&addr, ((char *)&from6->sin6_addr) + 12, sizeof(addr));
59 port = from6->sin6_port;
61 memset(&from, 0, sizeof(from));
63 from4->sin_family = AF_INET;
64 memcpy(&from4->sin_addr, &addr, sizeof(addr));
65 from4->sin_port = port;
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");
74 if (from.ss_family == AF_INET)
75 check_ip_options(socket, ntop);
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. */
83 log("Could not reverse map address %.100s.", ntop);
89 name[sizeof(name) - 1] = '\0';
91 * Convert it to all lowercase (which is expected by the rest
94 for (i = 0; name[i]; i++)
96 name[i] = tolower(name[i]);
98 if (!verify_reverse_mapping)
101 * Map it back to an IP address and check that the given
102 * address actually is an address of this host. This is
103 * necessary because anyone with access to a name server can
104 * define arbitrary names for an IP address. Mapping from
105 * name to IP address can be trusted better (but can still be
106 * fooled if the intruder has access to the name server of
109 memset(&hints, 0, sizeof(hints));
110 hints.ai_family = from.ss_family;
111 hints.ai_socktype = SOCK_STREAM;
112 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
113 log("reverse mapping checking getaddrinfo for %.700s "
114 "failed - POSSIBLE BREAKIN ATTEMPT!", name);
115 return xstrdup(ntop);
117 /* Look for the address from the list of addresses. */
118 for (ai = aitop; ai; ai = ai->ai_next) {
119 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
120 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
121 (strcmp(ntop, ntop2) == 0))
125 /* If we reached the end of the list, the address was not there. */
127 /* Address not found for the host name. */
128 log("Address %.100s maps to %.600s, but this does not "
129 "map back to the address - POSSIBLE BREAKIN ATTEMPT!",
131 return xstrdup(ntop);
133 return xstrdup(name);
137 * If IP options are supported, make sure there are none (log and
138 * disconnect them if any are found). Basically we are worried about
139 * source routing; it can be used to pretend you are somebody
140 * (ip-address) you are not. That itself may be "almost acceptable"
141 * under certain circumstances, but rhosts autentication is useless
142 * if source routing is accepted. Notice also that if we just dropped
143 * source routing here, the other side could use IP spoofing to do
144 * rest of the interaction and could still bypass security. So we
145 * exit here if we detect any IP options.
149 check_ip_options(int socket, char *ipaddr)
152 char text[sizeof(options) * 3 + 1];
153 socklen_t option_size;
157 if ((ip = getprotobyname("ip")) != NULL)
158 ipproto = ip->p_proto;
160 ipproto = IPPROTO_IP;
161 option_size = sizeof(options);
162 if (getsockopt(socket, ipproto, IP_OPTIONS, options,
163 &option_size) >= 0 && option_size != 0) {
165 for (i = 0; i < option_size; i++)
166 snprintf(text + i*3, sizeof(text) - i*3,
167 " %2.2x", options[i]);
168 log("Connection from %.100s with IP options:%.800s",
170 packet_disconnect("Connection from %.100s with IP options:%.800s",
176 * Return the canonical name of the host in the other side of the current
177 * connection. The host name is cached, so it is efficient to call this
182 get_canonical_hostname(int verify_reverse_mapping)
184 static char *canonical_host_name = NULL;
185 static int verify_reverse_mapping_done = 0;
187 /* Check if we have previously retrieved name with same option. */
188 if (canonical_host_name != NULL) {
189 if (verify_reverse_mapping_done != verify_reverse_mapping)
190 xfree(canonical_host_name);
192 return canonical_host_name;
195 /* Get the real hostname if socket; otherwise return UNKNOWN. */
196 if (packet_connection_is_on_socket())
197 canonical_host_name = get_remote_hostname(
198 packet_get_connection_in(), verify_reverse_mapping);
200 canonical_host_name = xstrdup("UNKNOWN");
202 verify_reverse_mapping_done = verify_reverse_mapping;
203 return canonical_host_name;
207 * Returns the remote IP-address of socket as a string. The returned
208 * string must be freed.
211 get_socket_address(int socket, int remote, int flags)
213 struct sockaddr_storage addr;
215 char ntop[NI_MAXHOST];
217 /* Get IP address of client. */
218 addrlen = sizeof(addr);
219 memset(&addr, 0, sizeof(addr));
222 if (getpeername(socket, (struct sockaddr *)&addr, &addrlen)
226 if (getsockname(socket, (struct sockaddr *)&addr, &addrlen)
230 /* Get the address in ascii. */
231 if (getnameinfo((struct sockaddr *)&addr, addrlen, ntop, sizeof(ntop),
232 NULL, 0, flags) != 0) {
233 error("get_socket_ipaddr: getnameinfo %d failed", flags);
236 return xstrdup(ntop);
240 get_peer_ipaddr(int socket)
244 if ((p = get_socket_address(socket, 1, NI_NUMERICHOST)) != NULL)
246 return xstrdup("UNKNOWN");
250 get_local_ipaddr(int socket)
254 if ((p = get_socket_address(socket, 0, NI_NUMERICHOST)) != NULL)
256 return xstrdup("UNKNOWN");
260 get_local_name(int socket)
262 return get_socket_address(socket, 0, NI_NAMEREQD);
266 * Returns the IP-address of the remote host as a string. The returned
267 * string must not be freed.
271 get_remote_ipaddr(void)
273 static char *canonical_host_ip = NULL;
275 /* Check whether we have cached the ipaddr. */
276 if (canonical_host_ip == NULL) {
277 if (packet_connection_is_on_socket()) {
279 get_peer_ipaddr(packet_get_connection_in());
280 if (canonical_host_ip == NULL)
283 /* If not on socket, return UNKNOWN. */
284 canonical_host_ip = xstrdup("UNKNOWN");
287 return canonical_host_ip;
291 get_remote_name_or_ip(u_int utmp_len, int verify_reverse_mapping)
293 static const char *remote = "";
295 remote = get_canonical_hostname(verify_reverse_mapping);
296 if (utmp_len == 0 || strlen(remote) > utmp_len)
297 remote = get_remote_ipaddr();
301 /* Returns the local/remote port for the socket. */
304 get_sock_port(int sock, int local)
306 struct sockaddr_storage from;
308 char strport[NI_MAXSERV];
310 /* Get IP address of client. */
311 fromlen = sizeof(from);
312 memset(&from, 0, sizeof(from));
314 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
315 error("getsockname failed: %.100s", strerror(errno));
319 if (getpeername(sock, (struct sockaddr *) & from, &fromlen) < 0) {
320 debug("getpeername failed: %.100s", strerror(errno));
324 /* Return port number. */
325 if (getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
326 strport, sizeof(strport), NI_NUMERICSERV) != 0)
327 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed");
328 return atoi(strport);
331 /* Returns remote/local port number for the current connection. */
337 * If the connection is not a socket, return 65535. This is
338 * intentionally chosen to be an unprivileged port number.
340 if (!packet_connection_is_on_socket())
343 /* Get socket and return the port number. */
344 return get_sock_port(packet_get_connection_in(), local);
348 get_peer_port(int sock)
350 return get_sock_port(sock, 0);
354 get_remote_port(void)