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 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. */
81 log("Could not reverse map address %.100s.", ntop);
87 name[sizeof(name) - 1] = '\0';
89 * Convert it to all lowercase (which is expected by the rest
92 for (i = 0; name[i]; i++)
94 name[i] = tolower(name[i]);
96 if (!verify_reverse_mapping)
99 * Map it back to an IP address and check that the given
100 * address actually is an address of this host. This is
101 * necessary because anyone with access to a name server can
102 * define arbitrary names for an IP address. Mapping from
103 * name to IP address can be trusted better (but can still be
104 * fooled if the intruder has access to the name server of
107 memset(&hints, 0, sizeof(hints));
108 hints.ai_family = from.ss_family;
109 hints.ai_socktype = SOCK_STREAM;
110 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
111 log("reverse mapping checking getaddrinfo for %.700s "
112 "failed - POSSIBLE BREAKIN ATTEMPT!", name);
113 return xstrdup(ntop);
115 /* Look for the address from the list of addresses. */
116 for (ai = aitop; ai; ai = ai->ai_next) {
117 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
118 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
119 (strcmp(ntop, ntop2) == 0))
123 /* If we reached the end of the list, the address was not there. */
125 /* Address not found for the host name. */
126 log("Address %.100s maps to %.600s, but this does not "
127 "map back to the address - POSSIBLE BREAKIN ATTEMPT!",
129 return xstrdup(ntop);
131 return xstrdup(name);
135 * If IP options are supported, make sure there are none (log and
136 * disconnect them if any are found). Basically we are worried about
137 * source routing; it can be used to pretend you are somebody
138 * (ip-address) you are not. That itself may be "almost acceptable"
139 * under certain circumstances, but rhosts autentication is useless
140 * if source routing is accepted. Notice also that if we just dropped
141 * source routing here, the other side could use IP spoofing to do
142 * rest of the interaction and could still bypass security. So we
143 * exit here if we detect any IP options.
147 check_ip_options(int socket, char *ipaddr)
150 char text[sizeof(options) * 3 + 1];
151 socklen_t option_size;
155 if ((ip = getprotobyname("ip")) != NULL)
156 ipproto = ip->p_proto;
158 ipproto = IPPROTO_IP;
159 option_size = sizeof(options);
160 if (getsockopt(socket, ipproto, IP_OPTIONS, options,
161 &option_size) >= 0 && option_size != 0) {
163 for (i = 0; i < option_size; i++)
164 snprintf(text + i*3, sizeof(text) - i*3,
165 " %2.2x", options[i]);
166 log("Connection from %.100s with IP options:%.800s",
168 packet_disconnect("Connection from %.100s with IP options:%.800s",
174 * Return the canonical name of the host in the other side of the current
175 * connection. The host name is cached, so it is efficient to call this
180 get_canonical_hostname(int verify_reverse_mapping)
182 static char *canonical_host_name = NULL;
183 static int verify_reverse_mapping_done = 0;
185 /* Check if we have previously retrieved name with same option. */
186 if (canonical_host_name != NULL) {
187 if (verify_reverse_mapping_done != verify_reverse_mapping)
188 xfree(canonical_host_name);
190 return canonical_host_name;
193 /* Get the real hostname if socket; otherwise return UNKNOWN. */
194 if (packet_connection_is_on_socket())
195 canonical_host_name = get_remote_hostname(
196 packet_get_connection_in(), verify_reverse_mapping);
198 canonical_host_name = xstrdup("UNKNOWN");
200 verify_reverse_mapping_done = verify_reverse_mapping;
201 return canonical_host_name;
205 * Returns the local/remote IP-address/hostname of socket as a string.
206 * The returned string must be freed.
209 get_socket_address(int socket, int remote, int flags)
211 struct sockaddr_storage addr;
213 char ntop[NI_MAXHOST];
215 /* Get IP address of client. */
216 addrlen = sizeof(addr);
217 memset(&addr, 0, sizeof(addr));
220 if (getpeername(socket, (struct sockaddr *)&addr, &addrlen)
224 if (getsockname(socket, (struct sockaddr *)&addr, &addrlen)
228 /* Get the address in ascii. */
229 if (getnameinfo((struct sockaddr *)&addr, addrlen, ntop, sizeof(ntop),
230 NULL, 0, flags) != 0) {
231 error("get_socket_address: getnameinfo %d failed", flags);
234 return xstrdup(ntop);
238 get_peer_ipaddr(int socket)
242 if ((p = get_socket_address(socket, 1, NI_NUMERICHOST)) != NULL)
244 return xstrdup("UNKNOWN");
248 get_local_ipaddr(int socket)
252 if ((p = get_socket_address(socket, 0, NI_NUMERICHOST)) != NULL)
254 return xstrdup("UNKNOWN");
258 get_local_name(int socket)
260 return get_socket_address(socket, 0, NI_NAMEREQD);
264 * Returns the IP-address of the remote host as a string. The returned
265 * string must not be freed.
269 get_remote_ipaddr(void)
271 static char *canonical_host_ip = NULL;
273 /* Check whether we have cached the ipaddr. */
274 if (canonical_host_ip == NULL) {
275 if (packet_connection_is_on_socket()) {
277 get_peer_ipaddr(packet_get_connection_in());
278 if (canonical_host_ip == NULL)
281 /* If not on socket, return UNKNOWN. */
282 canonical_host_ip = xstrdup("UNKNOWN");
285 return canonical_host_ip;
289 get_remote_name_or_ip(u_int utmp_len, int verify_reverse_mapping)
291 static const char *remote = "";
293 remote = get_canonical_hostname(verify_reverse_mapping);
294 if (utmp_len == 0 || strlen(remote) > utmp_len)
295 remote = get_remote_ipaddr();
299 /* Returns the local/remote port for the socket. */
302 get_sock_port(int sock, int local)
304 struct sockaddr_storage from;
306 char strport[NI_MAXSERV];
308 /* Get IP address of client. */
309 fromlen = sizeof(from);
310 memset(&from, 0, sizeof(from));
312 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
313 error("getsockname failed: %.100s", strerror(errno));
317 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
318 debug("getpeername failed: %.100s", strerror(errno));
322 /* Return port number. */
323 if (getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
324 strport, sizeof(strport), NI_NUMERICSERV) != 0)
325 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed");
326 return atoi(strport);
329 /* Returns remote/local port number for the current connection. */
335 * If the connection is not a socket, return 65535. This is
336 * intentionally chosen to be an unprivileged port number.
338 if (!packet_connection_is_on_socket())
341 /* Get socket and return the port number. */
342 return get_sock_port(packet_get_connection_in(), local);
346 get_peer_port(int sock)
348 return get_sock_port(sock, 0);
352 get_remote_port(void)