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 1.19 2001/01/29 19:42:33 markus Exp $");
22 * Return the canonical name of the host at the other end of the socket. The
23 * caller should free the returned string with xfree.
27 get_remote_hostname(int socket)
29 struct sockaddr_storage from;
32 struct addrinfo hints, *ai, *aitop;
33 char name[MAXHOSTNAMELEN];
34 char ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
36 /* Get IP address of client. */
37 fromlen = sizeof(from);
38 memset(&from, 0, sizeof(from));
39 if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) {
40 debug("getpeername failed: %.100s", strerror(errno));
45 if (from.ss_family == AF_INET6) {
46 struct sockaddr_in6 *from6 = (struct sockaddr_in6 *)&from;
48 /* Detect IPv4 in IPv6 mapped address and convert it to */
49 /* plain (AF_INET) IPv4 address */
50 if (IN6_IS_ADDR_V4MAPPED(&from6->sin6_addr)) {
51 struct sockaddr_in *from4 = (struct sockaddr_in *)&from;
55 memcpy(&addr, ((char *)&from6->sin6_addr) + 12, sizeof(addr));
56 port = from6->sin6_port;
58 memset(&from, 0, sizeof(from));
60 from4->sin_family = AF_INET;
61 memcpy(&from4->sin_addr, &addr, sizeof(addr));
62 from4->sin_port = port;
67 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
68 NULL, 0, NI_NUMERICHOST) != 0)
69 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
71 /* Map the IP address to a host name. */
72 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
73 NULL, 0, NI_NAMEREQD) == 0) {
75 name[sizeof(name) - 1] = '\0';
77 * Convert it to all lowercase (which is expected by the rest
80 for (i = 0; name[i]; i++)
82 name[i] = tolower(name[i]);
85 * Map it back to an IP address and check that the given
86 * address actually is an address of this host. This is
87 * necessary because anyone with access to a name server can
88 * define arbitrary names for an IP address. Mapping from
89 * name to IP address can be trusted better (but can still be
90 * fooled if the intruder has access to the name server of
93 memset(&hints, 0, sizeof(hints));
94 hints.ai_family = from.ss_family;
95 hints.ai_socktype = SOCK_STREAM;
96 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
97 log("reverse mapping checking getaddrinfo for %.700s failed - POSSIBLE BREAKIN ATTEMPT!", name);
98 strlcpy(name, ntop, sizeof name);
99 goto check_ip_options;
101 /* Look for the address from the list of addresses. */
102 for (ai = aitop; ai; ai = ai->ai_next) {
103 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
104 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
105 (strcmp(ntop, ntop2) == 0))
109 /* If we reached the end of the list, the address was not there. */
111 /* Address not found for the host name. */
112 log("Address %.100s maps to %.600s, but this does not map back to the address - POSSIBLE BREAKIN ATTEMPT!",
114 strlcpy(name, ntop, sizeof name);
115 goto check_ip_options;
117 /* Address was found for the host name. We accept the host name. */
119 /* Host name not found. Use ascii representation of the address. */
120 strlcpy(name, ntop, sizeof name);
121 log("Could not reverse map address %.100s.", name);
127 * If IP options are supported, make sure there are none (log and
128 * disconnect them if any are found). Basically we are worried about
129 * source routing; it can be used to pretend you are somebody
130 * (ip-address) you are not. That itself may be "almost acceptable"
131 * under certain circumstances, but rhosts autentication is useless
132 * if source routing is accepted. Notice also that if we just dropped
133 * source routing here, the other side could use IP spoofing to do
134 * rest of the interaction and could still bypass security. So we
135 * exit here if we detect any IP options.
137 /* IP options -- IPv4 only */
138 if (from.ss_family == AF_INET) {
139 u_char options[200], *ucp;
140 char text[1024], *cp;
141 socklen_t option_size;
145 if ((ip = getprotobyname("ip")) != NULL)
146 ipproto = ip->p_proto;
148 ipproto = IPPROTO_IP;
149 option_size = sizeof(options);
150 if (getsockopt(socket, ipproto, IP_OPTIONS, (char *) options,
151 &option_size) >= 0 && option_size != 0) {
153 /* Note: "text" buffer must be at least 3x as big as options. */
154 for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3)
155 sprintf(cp, " %2.2x", *ucp);
156 log("Connection from %.100s with IP options:%.800s",
158 packet_disconnect("Connection from %.100s with IP options:%.800s",
163 return xstrdup(name);
167 * Return the canonical name of the host in the other side of the current
168 * connection. The host name is cached, so it is efficient to call this
173 get_canonical_hostname()
175 static char *canonical_host_name = NULL;
177 /* Check if we have previously retrieved this same name. */
178 if (canonical_host_name != NULL)
179 return canonical_host_name;
181 /* Get the real hostname if socket; otherwise return UNKNOWN. */
182 if (packet_connection_is_on_socket())
183 canonical_host_name = get_remote_hostname(packet_get_connection_in());
185 canonical_host_name = xstrdup("UNKNOWN");
187 return canonical_host_name;
191 * Returns the remote IP-address of socket as a string. The returned
192 * string must be freed.
196 get_peer_ipaddr(int socket)
198 struct sockaddr_storage from;
200 char ntop[NI_MAXHOST];
202 /* Get IP address of client. */
203 fromlen = sizeof(from);
204 memset(&from, 0, sizeof(from));
205 if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) {
206 debug("get_peer_ipaddr: getpeername failed: %.100s", strerror(errno));
209 /* Get the IP address in ascii. */
210 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
211 NULL, 0, NI_NUMERICHOST) != 0) {
212 error("get_peer_ipaddr: getnameinfo NI_NUMERICHOST failed");
215 return xstrdup(ntop);
219 * Returns the IP-address of the remote host as a string. The returned
220 * string must not be freed.
226 static char *canonical_host_ip = NULL;
228 /* Check whether we have cached the ipaddr. */
229 if (canonical_host_ip == NULL) {
230 if (packet_connection_is_on_socket()) {
232 get_peer_ipaddr(packet_get_connection_in());
233 if (canonical_host_ip == NULL)
236 /* If not on socket, return UNKNOWN. */
237 canonical_host_ip = xstrdup("UNKNOWN");
240 return canonical_host_ip;
243 /* Returns the local/remote port for the socket. */
246 get_sock_port(int sock, int local)
248 struct sockaddr_storage from;
250 char strport[NI_MAXSERV];
252 /* Get IP address of client. */
253 fromlen = sizeof(from);
254 memset(&from, 0, sizeof(from));
256 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
257 error("getsockname failed: %.100s", strerror(errno));
261 if (getpeername(sock, (struct sockaddr *) & from, &fromlen) < 0) {
262 debug("getpeername failed: %.100s", strerror(errno));
266 /* Return port number. */
267 if (getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
268 strport, sizeof(strport), NI_NUMERICSERV) != 0)
269 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed");
270 return atoi(strport);
273 /* Returns remote/local port number for the current connection. */
279 * If the connection is not a socket, return 65535. This is
280 * intentionally chosen to be an unprivileged port number.
282 if (!packet_connection_is_on_socket())
285 /* Get socket and return the port number. */
286 return get_sock_port(packet_get_connection_in(), local);
290 get_peer_port(int sock)
292 return get_sock_port(sock, 0);