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 1.32 2002/06/11 08:11:45 itojun 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 memcpy(&from4->sin_addr, &addr, sizeof(addr));
63 from4->sin_port = port;
68 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
69 NULL, 0, NI_NUMERICHOST) != 0)
70 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
72 if (from.ss_family == AF_INET)
73 check_ip_options(socket, ntop);
75 debug3("Trying to reverse map address %.100s.", ntop);
76 /* Map the IP address to a host name. */
77 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
78 NULL, 0, NI_NAMEREQD) != 0) {
79 /* Host name not found. Use ip address. */
80 log("Could not reverse map address %.100s.", ntop);
85 name[sizeof(name) - 1] = '\0';
87 * Convert it to all lowercase (which is expected by the rest
90 for (i = 0; name[i]; i++)
92 name[i] = tolower(name[i]);
94 if (!verify_reverse_mapping)
97 * Map it back to an IP address and check that the given
98 * address actually is an address of this host. This is
99 * necessary because anyone with access to a name server can
100 * define arbitrary names for an IP address. Mapping from
101 * name to IP address can be trusted better (but can still be
102 * fooled if the intruder has access to the name server of
105 memset(&hints, 0, sizeof(hints));
106 hints.ai_family = from.ss_family;
107 hints.ai_socktype = SOCK_STREAM;
108 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
109 log("reverse mapping checking getaddrinfo for %.700s "
110 "failed - POSSIBLE BREAKIN ATTEMPT!", name);
111 return xstrdup(ntop);
113 /* Look for the address from the list of addresses. */
114 for (ai = aitop; ai; ai = ai->ai_next) {
115 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
116 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
117 (strcmp(ntop, ntop2) == 0))
121 /* If we reached the end of the list, the address was not there. */
123 /* Address not found for the host name. */
124 log("Address %.100s maps to %.600s, but this does not "
125 "map back to the address - POSSIBLE BREAKIN ATTEMPT!",
127 return xstrdup(ntop);
129 return xstrdup(name);
133 * If IP options are supported, make sure there are none (log and
134 * disconnect them if any are found). Basically we are worried about
135 * source routing; it can be used to pretend you are somebody
136 * (ip-address) you are not. That itself may be "almost acceptable"
137 * under certain circumstances, but rhosts autentication is useless
138 * if source routing is accepted. Notice also that if we just dropped
139 * source routing here, the other side could use IP spoofing to do
140 * rest of the interaction and could still bypass security. So we
141 * exit here if we detect any IP options.
145 check_ip_options(int socket, char *ipaddr)
148 char text[sizeof(options) * 3 + 1];
149 socklen_t option_size;
153 if ((ip = getprotobyname("ip")) != NULL)
154 ipproto = ip->p_proto;
156 ipproto = IPPROTO_IP;
157 option_size = sizeof(options);
158 if (getsockopt(socket, ipproto, IP_OPTIONS, options,
159 &option_size) >= 0 && option_size != 0) {
161 for (i = 0; i < option_size; i++)
162 snprintf(text + i*3, sizeof(text) - i*3,
163 " %2.2x", options[i]);
164 log("Connection from %.100s with IP options:%.800s",
166 packet_disconnect("Connection from %.100s with IP options:%.800s",
172 * Return the canonical name of the host in the other side of the current
173 * connection. The host name is cached, so it is efficient to call this
178 get_canonical_hostname(int verify_reverse_mapping)
180 static char *canonical_host_name = NULL;
181 static int verify_reverse_mapping_done = 0;
183 /* Check if we have previously retrieved name with same option. */
184 if (canonical_host_name != NULL) {
185 if (verify_reverse_mapping_done != verify_reverse_mapping)
186 xfree(canonical_host_name);
188 return canonical_host_name;
191 /* Get the real hostname if socket; otherwise return UNKNOWN. */
192 if (packet_connection_is_on_socket())
193 canonical_host_name = get_remote_hostname(
194 packet_get_connection_in(), verify_reverse_mapping);
196 canonical_host_name = xstrdup("UNKNOWN");
198 verify_reverse_mapping_done = verify_reverse_mapping;
199 return canonical_host_name;
203 * Returns the remote IP-address of socket as a string. The returned
204 * string must be freed.
207 get_socket_address(int socket, int remote, int flags)
209 struct sockaddr_storage addr;
211 char ntop[NI_MAXHOST];
213 /* Get IP address of client. */
214 addrlen = sizeof(addr);
215 memset(&addr, 0, sizeof(addr));
218 if (getpeername(socket, (struct sockaddr *)&addr, &addrlen)
220 debug("get_socket_ipaddr: getpeername failed: %.100s",
225 if (getsockname(socket, (struct sockaddr *)&addr, &addrlen)
227 debug("get_socket_ipaddr: getsockname failed: %.100s",
232 /* Get the address in ascii. */
233 if (getnameinfo((struct sockaddr *)&addr, addrlen, ntop, sizeof(ntop),
234 NULL, 0, flags) != 0) {
235 error("get_socket_ipaddr: getnameinfo %d failed", flags);
238 return xstrdup(ntop);
242 get_peer_ipaddr(int socket)
244 return get_socket_address(socket, 1, NI_NUMERICHOST);
248 get_local_ipaddr(int socket)
250 return get_socket_address(socket, 0, NI_NUMERICHOST);
254 get_local_name(int socket)
256 return get_socket_address(socket, 0, NI_NAMEREQD);
260 * Returns the IP-address of the remote host as a string. The returned
261 * string must not be freed.
265 get_remote_ipaddr(void)
267 static char *canonical_host_ip = NULL;
269 /* Check whether we have cached the ipaddr. */
270 if (canonical_host_ip == NULL) {
271 if (packet_connection_is_on_socket()) {
273 get_peer_ipaddr(packet_get_connection_in());
274 if (canonical_host_ip == NULL)
277 /* If not on socket, return UNKNOWN. */
278 canonical_host_ip = xstrdup("UNKNOWN");
281 return canonical_host_ip;
285 get_remote_name_or_ip(u_int utmp_len, int verify_reverse_mapping)
287 static const char *remote = "";
289 remote = get_canonical_hostname(verify_reverse_mapping);
290 if (utmp_len == 0 || strlen(remote) > utmp_len)
291 remote = get_remote_ipaddr();
295 /* Returns the local/remote port for the socket. */
298 get_sock_port(int sock, int local)
300 struct sockaddr_storage from;
302 char strport[NI_MAXSERV];
304 /* Get IP address of client. */
305 fromlen = sizeof(from);
306 memset(&from, 0, sizeof(from));
308 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
309 error("getsockname failed: %.100s", strerror(errno));
313 if (getpeername(sock, (struct sockaddr *) & from, &fromlen) < 0) {
314 debug("getpeername failed: %.100s", strerror(errno));
318 /* Return port number. */
319 if (getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
320 strport, sizeof(strport), NI_NUMERICSERV) != 0)
321 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed");
322 return atoi(strport);
325 /* Returns remote/local port number for the current connection. */
331 * If the connection is not a socket, return 65535. This is
332 * intentionally chosen to be an unprivileged port number.
334 if (!packet_connection_is_on_socket())
337 /* Get socket and return the port number. */
338 return get_sock_port(packet_get_connection_in(), local);
342 get_peer_port(int sock)
344 return get_sock_port(sock, 0);
348 get_remote_port(void)