1 /* $OpenBSD: canohost.c,v 1.53 2006/03/25 13:17:01 djm Exp $ */
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * Functions for returning the canonical host name of the remote site.
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose. Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
24 static void check_ip_options(int, char *);
27 * Return the canonical name of the host at the other end of the socket. The
28 * caller should free the returned string with xfree.
32 get_remote_hostname(int sock, int use_dns)
34 struct sockaddr_storage from;
37 struct addrinfo hints, *ai, *aitop;
38 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
40 /* Get IP address of client. */
41 fromlen = sizeof(from);
42 memset(&from, 0, sizeof(from));
43 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
44 debug("getpeername failed: %.100s", strerror(errno));
48 if (from.ss_family == AF_INET)
49 check_ip_options(sock, ntop);
51 ipv64_normalise_mapped(&from, &fromlen);
53 if (from.ss_family == AF_INET6)
54 fromlen = sizeof(struct sockaddr_in6);
56 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
57 NULL, 0, NI_NUMERICHOST) != 0)
58 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
63 debug3("Trying to reverse map address %.100s.", ntop);
64 /* Map the IP address to a host name. */
65 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
66 NULL, 0, NI_NAMEREQD) != 0) {
67 /* Host name not found. Use ip address. */
72 * if reverse lookup result looks like a numeric hostname,
73 * someone is trying to trick us by PTR record like following:
74 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
76 memset(&hints, 0, sizeof(hints));
77 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
78 hints.ai_flags = AI_NUMERICHOST;
79 if (getaddrinfo(name, "0", &hints, &ai) == 0) {
80 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
87 * Convert it to all lowercase (which is expected by the rest
90 for (i = 0; name[i]; i++)
92 name[i] = (char)tolower(name[i]);
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 logit("reverse mapping checking getaddrinfo for %.700s "
107 "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop);
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 logit("Address %.100s maps to %.600s, but this does not "
122 "map back to the address - POSSIBLE BREAK-IN 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 sock, char *ipaddr)
146 char text[sizeof(options) * 3 + 1];
147 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(sock, ipproto, IP_OPTIONS, 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 fatal("Connection from %.100s with IP options:%.800s",
166 #endif /* IP_OPTIONS */
170 ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
172 struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr;
173 struct sockaddr_in *a4 = (struct sockaddr_in *)addr;
174 struct in_addr inaddr;
177 if (addr->ss_family != AF_INET6 ||
178 !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr))
181 debug3("Normalising mapped IPv4 in IPv6 address");
183 memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr));
184 port = a6->sin6_port;
186 memset(addr, 0, sizeof(*a4));
188 a4->sin_family = AF_INET;
190 memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr));
195 * Return the canonical name of the host in the other side of the current
196 * connection. The host name is cached, so it is efficient to call this
201 get_canonical_hostname(int use_dns)
204 static char *canonical_host_name = NULL;
205 static char *remote_ip = NULL;
207 /* Check if we have previously retrieved name with same option. */
208 if (use_dns && canonical_host_name != NULL)
209 return canonical_host_name;
210 if (!use_dns && remote_ip != NULL)
213 /* Get the real hostname if socket; otherwise return UNKNOWN. */
214 if (packet_connection_is_on_socket())
215 host = get_remote_hostname(packet_get_connection_in(), use_dns);
220 canonical_host_name = host;
227 * Returns the local/remote IP-address/hostname of socket as a string.
228 * The returned string must be freed.
231 get_socket_address(int sock, int remote, int flags)
233 struct sockaddr_storage addr;
235 char ntop[NI_MAXHOST];
238 /* Get IP address of client. */
239 addrlen = sizeof(addr);
240 memset(&addr, 0, sizeof(addr));
243 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen)
247 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen)
252 /* Work around Linux IPv6 weirdness */
253 if (addr.ss_family == AF_INET6)
254 addrlen = sizeof(struct sockaddr_in6);
256 ipv64_normalise_mapped(&addr, &addrlen);
258 /* Get the address in ascii. */
259 if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
260 sizeof(ntop), NULL, 0, flags)) != 0) {
261 error("get_socket_address: getnameinfo %d failed: %s", flags,
262 r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r));
265 return xstrdup(ntop);
269 get_peer_ipaddr(int sock)
273 if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL)
275 return xstrdup("UNKNOWN");
279 get_local_ipaddr(int sock)
283 if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL)
285 return xstrdup("UNKNOWN");
289 get_local_name(int sock)
291 return get_socket_address(sock, 0, NI_NAMEREQD);
295 * Returns the IP-address of the remote host as a string. The returned
296 * string must not be freed.
300 get_remote_ipaddr(void)
302 static char *canonical_host_ip = NULL;
304 /* Check whether we have cached the ipaddr. */
305 if (canonical_host_ip == NULL) {
306 if (packet_connection_is_on_socket()) {
308 get_peer_ipaddr(packet_get_connection_in());
309 if (canonical_host_ip == NULL)
312 /* If not on socket, return UNKNOWN. */
313 canonical_host_ip = xstrdup("UNKNOWN");
316 return canonical_host_ip;
320 get_remote_name_or_ip(u_int utmp_len, int use_dns)
322 static const char *remote = "";
324 remote = get_canonical_hostname(use_dns);
325 if (utmp_len == 0 || strlen(remote) > utmp_len)
326 remote = get_remote_ipaddr();
330 /* Returns the local/remote port for the socket. */
333 get_sock_port(int sock, int local)
335 struct sockaddr_storage from;
337 char strport[NI_MAXSERV];
340 /* Get IP address of client. */
341 fromlen = sizeof(from);
342 memset(&from, 0, sizeof(from));
344 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
345 error("getsockname failed: %.100s", strerror(errno));
349 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
350 debug("getpeername failed: %.100s", strerror(errno));
355 /* Work around Linux IPv6 weirdness */
356 if (from.ss_family == AF_INET6)
357 fromlen = sizeof(struct sockaddr_in6);
359 /* Return port number. */
360 if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
361 strport, sizeof(strport), NI_NUMERICSERV)) != 0)
362 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s",
363 r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r));
364 return atoi(strport);
367 /* Returns remote/local port number for the current connection. */
373 * If the connection is not a socket, return 65535. This is
374 * intentionally chosen to be an unprivileged port number.
376 if (!packet_connection_is_on_socket())
379 /* Get socket and return the port number. */
380 return get_sock_port(packet_get_connection_in(), local);
384 get_peer_port(int sock)
386 return get_sock_port(sock, 0);
390 get_remote_port(void)
392 static int port = -1;
394 /* Cache to avoid getpeername() on a dead connection */