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 1.20 2001/02/03 10:08:37 markus Exp $");
21 void check_ip_options(int socket, char *ipaddr);
24 * Return the canonical name of the host at the other end of the socket. The
25 * caller should free the returned string with xfree.
29 get_remote_hostname(int socket, int reverse_mapping_check)
31 struct sockaddr_storage from;
34 struct addrinfo hints, *ai, *aitop;
35 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
37 /* Get IP address of client. */
38 fromlen = sizeof(from);
39 memset(&from, 0, sizeof(from));
40 if (getpeername(socket, (struct sockaddr *) &from, &fromlen) < 0) {
41 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;
66 if (from.ss_family == AF_INET)
67 check_ip_options(socket, ntop);
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 /* Map the IP address to a host name. */
74 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
75 NULL, 0, NI_NAMEREQD) != 0) {
76 /* Host name not found. Use ip address. */
77 log("Could not reverse map address %.100s.", ntop);
82 name[sizeof(name) - 1] = '\0';
84 * Convert it to all lowercase (which is expected by the rest
87 for (i = 0; name[i]; i++)
89 name[i] = tolower(name[i]);
91 if (!reverse_mapping_check)
94 * Map it back to an IP address and check that the given
95 * address actually is an address of this host. This is
96 * necessary because anyone with access to a name server can
97 * define arbitrary names for an IP address. Mapping from
98 * name to IP address can be trusted better (but can still be
99 * fooled if the intruder has access to the name server of
102 memset(&hints, 0, sizeof(hints));
103 hints.ai_family = from.ss_family;
104 hints.ai_socktype = SOCK_STREAM;
105 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
106 log("reverse mapping checking getaddrinfo for %.700s "
107 "failed - POSSIBLE BREAKIN ATTEMPT!", name);
108 return xstrdup(ntop);
110 /* Look for the address from the list of addresses. */
111 for (ai = aitop; ai; ai = ai->ai_next) {
112 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
113 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
114 (strcmp(ntop, ntop2) == 0))
118 /* If we reached the end of the list, the address was not there. */
120 /* Address not found for the host name. */
121 log("Address %.100s maps to %.600s, but this does not "
122 "map back to the address - POSSIBLE BREAKIN ATTEMPT!",
124 return xstrdup(ntop);
126 return xstrdup(name);
130 * If IP options are supported, make sure there are none (log and
131 * disconnect them if any are found). Basically we are worried about
132 * source routing; it can be used to pretend you are somebody
133 * (ip-address) you are not. That itself may be "almost acceptable"
134 * under certain circumstances, but rhosts autentication is useless
135 * if source routing is accepted. Notice also that if we just dropped
136 * source routing here, the other side could use IP spoofing to do
137 * rest of the interaction and could still bypass security. So we
138 * exit here if we detect any IP options.
142 check_ip_options(int socket, char *ipaddr)
144 u_char options[200], *ucp;
145 char text[1024], *cp;
146 socklen_t option_size;
150 if ((ip = getprotobyname("ip")) != NULL)
151 ipproto = ip->p_proto;
153 ipproto = IPPROTO_IP;
154 option_size = sizeof(options);
155 if (getsockopt(socket, ipproto, IP_OPTIONS, (void *)options,
156 &option_size) >= 0 && option_size != 0) {
158 /* Note: "text" buffer must be at least 3x as big as options. */
159 for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3)
160 sprintf(cp, " %2.2x", *ucp);
161 log("Connection from %.100s with IP options:%.800s",
163 packet_disconnect("Connection from %.100s with IP options:%.800s",
169 * Return the canonical name of the host in the other side of the current
170 * connection. The host name is cached, so it is efficient to call this
175 get_canonical_hostname(int reverse_mapping_check)
177 static char *canonical_host_name = NULL;
178 static int reverse_mapping_checked = 0;
180 /* Check if we have previously retrieved name with same option. */
181 if (canonical_host_name != NULL) {
182 if (reverse_mapping_checked != reverse_mapping_check)
183 xfree(canonical_host_name);
185 return canonical_host_name;
188 /* Get the real hostname if socket; otherwise return UNKNOWN. */
189 if (packet_connection_is_on_socket())
190 canonical_host_name = get_remote_hostname(
191 packet_get_connection_in(), reverse_mapping_check);
193 canonical_host_name = xstrdup("UNKNOWN");
195 reverse_mapping_checked = reverse_mapping_check;
196 return canonical_host_name;
200 * Returns the remote IP-address of socket as a string. The returned
201 * string must be freed.
205 get_peer_ipaddr(int socket)
207 struct sockaddr_storage from;
209 char ntop[NI_MAXHOST];
211 /* Get IP address of client. */
212 fromlen = sizeof(from);
213 memset(&from, 0, sizeof(from));
214 if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) {
215 debug("get_peer_ipaddr: getpeername failed: %.100s", strerror(errno));
218 /* Get the IP address in ascii. */
219 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
220 NULL, 0, NI_NUMERICHOST) != 0) {
221 error("get_peer_ipaddr: getnameinfo NI_NUMERICHOST failed");
224 return xstrdup(ntop);
228 * Returns the IP-address of the remote host as a string. The returned
229 * string must not be freed.
235 static char *canonical_host_ip = NULL;
237 /* Check whether we have cached the ipaddr. */
238 if (canonical_host_ip == NULL) {
239 if (packet_connection_is_on_socket()) {
241 get_peer_ipaddr(packet_get_connection_in());
242 if (canonical_host_ip == NULL)
245 /* If not on socket, return UNKNOWN. */
246 canonical_host_ip = xstrdup("UNKNOWN");
249 return canonical_host_ip;
252 /* Returns the local/remote port for the socket. */
255 get_sock_port(int sock, int local)
257 struct sockaddr_storage from;
259 char strport[NI_MAXSERV];
261 /* Get IP address of client. */
262 fromlen = sizeof(from);
263 memset(&from, 0, sizeof(from));
265 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
266 error("getsockname failed: %.100s", strerror(errno));
270 if (getpeername(sock, (struct sockaddr *) & from, &fromlen) < 0) {
271 debug("getpeername failed: %.100s", strerror(errno));
275 /* Return port number. */
276 if (getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
277 strport, sizeof(strport), NI_NUMERICSERV) != 0)
278 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed");
279 return atoi(strport);
282 /* Returns remote/local port number for the current connection. */
288 * If the connection is not a socket, return 65535. This is
289 * intentionally chosen to be an unprivileged port number.
291 if (!packet_connection_is_on_socket())
294 /* Get socket and return the port number. */
295 return get_sock_port(packet_get_connection_in(), local);
299 get_peer_port(int sock)
301 return get_sock_port(sock, 0);