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 1.28 2001/12/05 03:56:39 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 reverse_mapping_check)
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;
67 if (from.ss_family == AF_INET)
68 check_ip_options(socket, ntop);
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 debug3("Trying to reverse map address %.100s.", ntop);
75 /* Map the IP address to a host name. */
76 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
77 NULL, 0, NI_NAMEREQD) != 0) {
78 /* Host name not found. Use ip address. */
79 log("Could not reverse map address %.100s.", ntop);
84 name[sizeof(name) - 1] = '\0';
86 * Convert it to all lowercase (which is expected by the rest
89 for (i = 0; name[i]; i++)
91 name[i] = tolower(name[i]);
93 if (!reverse_mapping_check)
96 * Map it back to an IP address and check that the given
97 * address actually is an address of this host. This is
98 * necessary because anyone with access to a name server can
99 * define arbitrary names for an IP address. Mapping from
100 * name to IP address can be trusted better (but can still be
101 * fooled if the intruder has access to the name server of
104 memset(&hints, 0, sizeof(hints));
105 hints.ai_family = from.ss_family;
106 hints.ai_socktype = SOCK_STREAM;
107 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
108 log("reverse mapping checking getaddrinfo for %.700s "
109 "failed - POSSIBLE BREAKIN ATTEMPT!", name);
110 return xstrdup(ntop);
112 /* Look for the address from the list of addresses. */
113 for (ai = aitop; ai; ai = ai->ai_next) {
114 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
115 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
116 (strcmp(ntop, ntop2) == 0))
120 /* If we reached the end of the list, the address was not there. */
122 /* Address not found for the host name. */
123 log("Address %.100s maps to %.600s, but this does not "
124 "map back to the address - POSSIBLE BREAKIN ATTEMPT!",
126 return xstrdup(ntop);
128 return xstrdup(name);
132 * If IP options are supported, make sure there are none (log and
133 * disconnect them if any are found). Basically we are worried about
134 * source routing; it can be used to pretend you are somebody
135 * (ip-address) you are not. That itself may be "almost acceptable"
136 * under certain circumstances, but rhosts autentication is useless
137 * if source routing is accepted. Notice also that if we just dropped
138 * source routing here, the other side could use IP spoofing to do
139 * rest of the interaction and could still bypass security. So we
140 * exit here if we detect any IP options.
144 check_ip_options(int socket, char *ipaddr)
147 char text[sizeof(options) * 3 + 1];
148 socklen_t option_size;
152 if ((ip = getprotobyname("ip")) != NULL)
153 ipproto = ip->p_proto;
155 ipproto = IPPROTO_IP;
156 option_size = sizeof(options);
157 if (getsockopt(socket, ipproto, IP_OPTIONS, (void *)options,
158 &option_size) >= 0 && option_size != 0) {
160 for (i = 0; i < option_size; i++)
161 snprintf(text + i*3, sizeof(text) - i*3,
162 " %2.2x", options[i]);
163 log("Connection from %.100s with IP options:%.800s",
165 packet_disconnect("Connection from %.100s with IP options:%.800s",
171 * Return the canonical name of the host in the other side of the current
172 * connection. The host name is cached, so it is efficient to call this
177 get_canonical_hostname(int reverse_mapping_check)
179 static char *canonical_host_name = NULL;
180 static int reverse_mapping_checked = 0;
182 /* Check if we have previously retrieved name with same option. */
183 if (canonical_host_name != NULL) {
184 if (reverse_mapping_checked != reverse_mapping_check)
185 xfree(canonical_host_name);
187 return canonical_host_name;
190 /* Get the real hostname if socket; otherwise return UNKNOWN. */
191 if (packet_connection_is_on_socket())
192 canonical_host_name = get_remote_hostname(
193 packet_get_connection_in(), reverse_mapping_check);
195 canonical_host_name = xstrdup("UNKNOWN");
197 reverse_mapping_checked = reverse_mapping_check;
198 return canonical_host_name;
202 * Returns the remote IP-address of socket as a string. The returned
203 * string must be freed.
206 get_socket_address(int socket, int remote, int flags)
208 struct sockaddr_storage addr;
210 char ntop[NI_MAXHOST];
212 /* Get IP address of client. */
213 addrlen = sizeof(addr);
214 memset(&addr, 0, sizeof(addr));
217 if (getpeername(socket, (struct sockaddr *)&addr, &addrlen)
219 debug("get_socket_ipaddr: getpeername failed: %.100s",
224 if (getsockname(socket, (struct sockaddr *)&addr, &addrlen)
226 debug("get_socket_ipaddr: getsockname failed: %.100s",
231 /* Get the address in ascii. */
232 if (getnameinfo((struct sockaddr *)&addr, addrlen, ntop, sizeof(ntop),
233 NULL, 0, flags) != 0) {
234 error("get_socket_ipaddr: getnameinfo %d failed", flags);
237 return xstrdup(ntop);
241 get_peer_ipaddr(int socket)
243 return get_socket_address(socket, 1, NI_NUMERICHOST);
247 get_local_ipaddr(int socket)
249 return get_socket_address(socket, 0, NI_NUMERICHOST);
253 get_local_name(int socket)
255 return get_socket_address(socket, 0, NI_NAMEREQD);
259 * Returns the IP-address of the remote host as a string. The returned
260 * string must not be freed.
264 get_remote_ipaddr(void)
266 static char *canonical_host_ip = NULL;
268 /* Check whether we have cached the ipaddr. */
269 if (canonical_host_ip == NULL) {
270 if (packet_connection_is_on_socket()) {
272 get_peer_ipaddr(packet_get_connection_in());
273 if (canonical_host_ip == NULL)
276 /* If not on socket, return UNKNOWN. */
277 canonical_host_ip = xstrdup("UNKNOWN");
280 return canonical_host_ip;
284 get_remote_name_or_ip(u_int utmp_len, int reverse_mapping_check)
286 static const char *remote = "";
288 remote = get_canonical_hostname(reverse_mapping_check);
289 if (utmp_len == 0 || strlen(remote) > utmp_len)
290 remote = get_remote_ipaddr();
294 /* Returns the local/remote port for the socket. */
297 get_sock_port(int sock, int local)
299 struct sockaddr_storage from;
301 char strport[NI_MAXSERV];
303 /* Get IP address of client. */
304 fromlen = sizeof(from);
305 memset(&from, 0, sizeof(from));
307 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
308 error("getsockname failed: %.100s", strerror(errno));
312 if (getpeername(sock, (struct sockaddr *) & from, &fromlen) < 0) {
313 debug("getpeername failed: %.100s", strerror(errno));
317 /* Return port number. */
318 if (getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
319 strport, sizeof(strport), NI_NUMERICSERV) != 0)
320 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed");
321 return atoi(strport);
324 /* Returns remote/local port number for the current connection. */
330 * If the connection is not a socket, return 65535. This is
331 * intentionally chosen to be an unprivileged port number.
333 if (!packet_connection_is_on_socket())
336 /* Get socket and return the port number. */
337 return get_sock_port(packet_get_connection_in(), local);
341 get_peer_port(int sock)
343 return get_sock_port(sock, 0);
347 get_remote_port(void)