1 /* $OpenBSD: canohost.c,v 1.61 2006/08/03 03:34:41 deraadt 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".
17 #include <sys/types.h>
18 #include <sys/socket.h>
20 #include <netinet/in.h>
35 static void check_ip_options(int, char *);
38 * Return the canonical name of the host at the other end of the socket. The
39 * caller should free the returned string with xfree.
43 get_remote_hostname(int sock, int use_dns)
45 struct sockaddr_storage from;
48 struct addrinfo hints, *ai, *aitop;
49 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
51 /* Get IP address of client. */
52 fromlen = sizeof(from);
53 memset(&from, 0, sizeof(from));
54 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
55 debug("getpeername failed: %.100s", strerror(errno));
59 if (from.ss_family == AF_INET)
60 check_ip_options(sock, ntop);
62 ipv64_normalise_mapped(&from, &fromlen);
64 if (from.ss_family == AF_INET6)
65 fromlen = sizeof(struct sockaddr_in6);
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");
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. */
83 * if reverse lookup result looks like a numeric hostname,
84 * someone is trying to trick us by PTR record like following:
85 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
87 memset(&hints, 0, sizeof(hints));
88 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
89 hints.ai_flags = AI_NUMERICHOST;
90 if (getaddrinfo(name, "0", &hints, &ai) == 0) {
91 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
98 * Convert it to all lowercase (which is expected by the rest
101 for (i = 0; name[i]; i++)
102 if (isupper(name[i]))
103 name[i] = (char)tolower(name[i]);
105 * Map it back to an IP address and check that the given
106 * address actually is an address of this host. This is
107 * necessary because anyone with access to a name server can
108 * define arbitrary names for an IP address. Mapping from
109 * name to IP address can be trusted better (but can still be
110 * fooled if the intruder has access to the name server of
113 memset(&hints, 0, sizeof(hints));
114 hints.ai_family = from.ss_family;
115 hints.ai_socktype = SOCK_STREAM;
116 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
117 logit("reverse mapping checking getaddrinfo for %.700s "
118 "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop);
119 return xstrdup(ntop);
121 /* Look for the address from the list of addresses. */
122 for (ai = aitop; ai; ai = ai->ai_next) {
123 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
124 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
125 (strcmp(ntop, ntop2) == 0))
129 /* If we reached the end of the list, the address was not there. */
131 /* Address not found for the host name. */
132 logit("Address %.100s maps to %.600s, but this does not "
133 "map back to the address - POSSIBLE BREAK-IN ATTEMPT!",
135 return xstrdup(ntop);
137 return xstrdup(name);
141 * If IP options are supported, make sure there are none (log and
142 * disconnect them if any are found). Basically we are worried about
143 * source routing; it can be used to pretend you are somebody
144 * (ip-address) you are not. That itself may be "almost acceptable"
145 * under certain circumstances, but rhosts autentication is useless
146 * if source routing is accepted. Notice also that if we just dropped
147 * source routing here, the other side could use IP spoofing to do
148 * rest of the interaction and could still bypass security. So we
149 * exit here if we detect any IP options.
153 check_ip_options(int sock, char *ipaddr)
157 char text[sizeof(options) * 3 + 1];
158 socklen_t option_size;
163 if ((ip = getprotobyname("ip")) != NULL)
164 ipproto = ip->p_proto;
166 ipproto = IPPROTO_IP;
167 option_size = sizeof(options);
168 if (getsockopt(sock, ipproto, IP_OPTIONS, options,
169 &option_size) >= 0 && option_size != 0) {
171 for (i = 0; i < option_size; i++)
172 snprintf(text + i*3, sizeof(text) - i*3,
173 " %2.2x", options[i]);
174 fatal("Connection from %.100s with IP options:%.800s",
177 #endif /* IP_OPTIONS */
181 ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
183 struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr;
184 struct sockaddr_in *a4 = (struct sockaddr_in *)addr;
185 struct in_addr inaddr;
188 if (addr->ss_family != AF_INET6 ||
189 !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr))
192 debug3("Normalising mapped IPv4 in IPv6 address");
194 memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr));
195 port = a6->sin6_port;
197 memset(addr, 0, sizeof(*a4));
199 a4->sin_family = AF_INET;
201 memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr));
206 * Return the canonical name of the host in the other side of the current
207 * connection. The host name is cached, so it is efficient to call this
212 get_canonical_hostname(int use_dns)
215 static char *canonical_host_name = NULL;
216 static char *remote_ip = NULL;
218 /* Check if we have previously retrieved name with same option. */
219 if (use_dns && canonical_host_name != NULL)
220 return canonical_host_name;
221 if (!use_dns && remote_ip != NULL)
224 /* Get the real hostname if socket; otherwise return UNKNOWN. */
225 if (packet_connection_is_on_socket())
226 host = get_remote_hostname(packet_get_connection_in(), use_dns);
231 canonical_host_name = host;
238 * Returns the local/remote IP-address/hostname of socket as a string.
239 * The returned string must be freed.
242 get_socket_address(int sock, int remote, int flags)
244 struct sockaddr_storage addr;
246 char ntop[NI_MAXHOST];
249 /* Get IP address of client. */
250 addrlen = sizeof(addr);
251 memset(&addr, 0, sizeof(addr));
254 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen)
258 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen)
263 /* Work around Linux IPv6 weirdness */
264 if (addr.ss_family == AF_INET6)
265 addrlen = sizeof(struct sockaddr_in6);
267 ipv64_normalise_mapped(&addr, &addrlen);
269 /* Get the address in ascii. */
270 if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
271 sizeof(ntop), NULL, 0, flags)) != 0) {
272 error("get_socket_address: getnameinfo %d failed: %s", flags,
273 r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r));
276 return xstrdup(ntop);
280 get_peer_ipaddr(int sock)
284 if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL)
286 return xstrdup("UNKNOWN");
290 get_local_ipaddr(int sock)
294 if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL)
296 return xstrdup("UNKNOWN");
300 get_local_name(int sock)
302 return get_socket_address(sock, 0, NI_NAMEREQD);
306 * Returns the IP-address of the remote host as a string. The returned
307 * string must not be freed.
311 get_remote_ipaddr(void)
313 static char *canonical_host_ip = NULL;
315 /* Check whether we have cached the ipaddr. */
316 if (canonical_host_ip == NULL) {
317 if (packet_connection_is_on_socket()) {
319 get_peer_ipaddr(packet_get_connection_in());
320 if (canonical_host_ip == NULL)
323 /* If not on socket, return UNKNOWN. */
324 canonical_host_ip = xstrdup("UNKNOWN");
327 return canonical_host_ip;
331 get_remote_name_or_ip(u_int utmp_len, int use_dns)
333 static const char *remote = "";
335 remote = get_canonical_hostname(use_dns);
336 if (utmp_len == 0 || strlen(remote) > utmp_len)
337 remote = get_remote_ipaddr();
341 /* Returns the local/remote port for the socket. */
344 get_sock_port(int sock, int local)
346 struct sockaddr_storage from;
348 char strport[NI_MAXSERV];
351 /* Get IP address of client. */
352 fromlen = sizeof(from);
353 memset(&from, 0, sizeof(from));
355 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
356 error("getsockname failed: %.100s", strerror(errno));
360 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
361 debug("getpeername failed: %.100s", strerror(errno));
366 /* Work around Linux IPv6 weirdness */
367 if (from.ss_family == AF_INET6)
368 fromlen = sizeof(struct sockaddr_in6);
370 /* Return port number. */
371 if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
372 strport, sizeof(strport), NI_NUMERICSERV)) != 0)
373 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s",
374 r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r));
375 return atoi(strport);
378 /* Returns remote/local port number for the current connection. */
384 * If the connection is not a socket, return 65535. This is
385 * intentionally chosen to be an unprivileged port number.
387 if (!packet_connection_is_on_socket())
390 /* Get socket and return the port number. */
391 return get_sock_port(packet_get_connection_in(), local);
395 get_peer_port(int sock)
397 return get_sock_port(sock, 0);
401 get_remote_port(void)
403 static int port = -1;
405 /* Cache to avoid getpeername() on a dead connection */