1 /* $OpenBSD: canohost.c,v 1.64 2009/02/12 03:00:56 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".
17 #include <sys/types.h>
18 #include <sys/socket.h>
19 #include <sys/param.h> /* for MAXHOSTNAMELEN */
21 #include <netinet/in.h>
22 #include <arpa/inet.h>
39 static void check_ip_options(int, char *);
42 * Return the canonical name of the host at the other end of the socket. The
43 * caller should free the returned string with xfree.
47 get_remote_hostname(int sock, int use_dns)
49 struct sockaddr_storage from;
52 struct addrinfo hints, *ai, *aitop;
53 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
55 /* Get IP address of client. */
56 fromlen = sizeof(from);
57 memset(&from, 0, sizeof(from));
58 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
59 debug("getpeername failed: %.100s", strerror(errno));
63 if (from.ss_family == AF_INET)
64 check_ip_options(sock, ntop);
66 ipv64_normalise_mapped(&from, &fromlen);
68 if (from.ss_family == AF_INET6)
69 fromlen = sizeof(struct sockaddr_in6);
71 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
72 NULL, 0, NI_NUMERICHOST) != 0)
73 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
78 debug3("Trying to reverse map address %.100s.", ntop);
79 /* Map the IP address to a host name. */
80 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
81 NULL, 0, NI_NAMEREQD) != 0) {
82 /* Host name not found. Use ip address. */
87 * if reverse lookup result looks like a numeric hostname,
88 * someone is trying to trick us by PTR record like following:
89 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
91 memset(&hints, 0, sizeof(hints));
92 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
93 hints.ai_flags = AI_NUMERICHOST;
94 if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
95 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
102 * Convert it to all lowercase (which is expected by the rest
105 for (i = 0; name[i]; i++)
106 if (isupper(name[i]))
107 name[i] = (char)tolower(name[i]);
109 * Map it back to an IP address and check that the given
110 * address actually is an address of this host. This is
111 * necessary because anyone with access to a name server can
112 * define arbitrary names for an IP address. Mapping from
113 * name to IP address can be trusted better (but can still be
114 * fooled if the intruder has access to the name server of
117 memset(&hints, 0, sizeof(hints));
118 hints.ai_family = from.ss_family;
119 hints.ai_socktype = SOCK_STREAM;
120 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
121 logit("reverse mapping checking getaddrinfo for %.700s "
122 "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop);
123 return xstrdup(ntop);
125 /* Look for the address from the list of addresses. */
126 for (ai = aitop; ai; ai = ai->ai_next) {
127 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
128 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
129 (strcmp(ntop, ntop2) == 0))
133 /* If we reached the end of the list, the address was not there. */
135 /* Address not found for the host name. */
136 logit("Address %.100s maps to %.600s, but this does not "
137 "map back to the address - POSSIBLE BREAK-IN ATTEMPT!",
139 return xstrdup(ntop);
141 return xstrdup(name);
145 * If IP options are supported, make sure there are none (log and
146 * disconnect them if any are found). Basically we are worried about
147 * source routing; it can be used to pretend you are somebody
148 * (ip-address) you are not. That itself may be "almost acceptable"
149 * under certain circumstances, but rhosts autentication is useless
150 * if source routing is accepted. Notice also that if we just dropped
151 * source routing here, the other side could use IP spoofing to do
152 * rest of the interaction and could still bypass security. So we
153 * exit here if we detect any IP options.
157 check_ip_options(int sock, char *ipaddr)
161 char text[sizeof(options) * 3 + 1];
162 socklen_t option_size;
167 if ((ip = getprotobyname("ip")) != NULL)
168 ipproto = ip->p_proto;
170 ipproto = IPPROTO_IP;
171 option_size = sizeof(options);
172 if (getsockopt(sock, ipproto, IP_OPTIONS, options,
173 &option_size) >= 0 && option_size != 0) {
175 for (i = 0; i < option_size; i++)
176 snprintf(text + i*3, sizeof(text) - i*3,
177 " %2.2x", options[i]);
178 fatal("Connection from %.100s with IP options:%.800s",
181 #endif /* IP_OPTIONS */
185 ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
187 struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr;
188 struct sockaddr_in *a4 = (struct sockaddr_in *)addr;
189 struct in_addr inaddr;
192 if (addr->ss_family != AF_INET6 ||
193 !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr))
196 debug3("Normalising mapped IPv4 in IPv6 address");
198 memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr));
199 port = a6->sin6_port;
201 memset(addr, 0, sizeof(*a4));
203 a4->sin_family = AF_INET;
205 memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr));
210 * Return the canonical name of the host in the other side of the current
211 * connection. The host name is cached, so it is efficient to call this
216 get_canonical_hostname(int use_dns)
219 static char *canonical_host_name = NULL;
220 static char *remote_ip = NULL;
222 /* Check if we have previously retrieved name with same option. */
223 if (use_dns && canonical_host_name != NULL)
224 return canonical_host_name;
225 if (!use_dns && remote_ip != NULL)
228 /* Get the real hostname if socket; otherwise return UNKNOWN. */
229 if (packet_connection_is_on_socket())
230 host = get_remote_hostname(packet_get_connection_in(), use_dns);
235 canonical_host_name = host;
242 * Returns the local/remote IP-address/hostname of socket as a string.
243 * The returned string must be freed.
246 get_socket_address(int sock, int remote, int flags)
248 struct sockaddr_storage addr;
250 char ntop[NI_MAXHOST];
253 /* Get IP address of client. */
254 addrlen = sizeof(addr);
255 memset(&addr, 0, sizeof(addr));
258 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen)
262 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen)
267 /* Work around Linux IPv6 weirdness */
268 if (addr.ss_family == AF_INET6)
269 addrlen = sizeof(struct sockaddr_in6);
271 ipv64_normalise_mapped(&addr, &addrlen);
273 /* Get the address in ascii. */
274 if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
275 sizeof(ntop), NULL, 0, flags)) != 0) {
276 error("get_socket_address: getnameinfo %d failed: %s", flags,
277 ssh_gai_strerror(r));
280 return xstrdup(ntop);
284 get_peer_ipaddr(int sock)
288 if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL)
290 return xstrdup("UNKNOWN");
294 get_local_ipaddr(int sock)
298 if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL)
300 return xstrdup("UNKNOWN");
304 get_local_name(int sock)
306 return get_socket_address(sock, 0, NI_NAMEREQD);
310 * Returns the IP-address of the remote host as a string. The returned
311 * string must not be freed.
315 get_remote_ipaddr(void)
317 static char *canonical_host_ip = NULL;
319 /* Check whether we have cached the ipaddr. */
320 if (canonical_host_ip == NULL) {
321 if (packet_connection_is_on_socket()) {
323 get_peer_ipaddr(packet_get_connection_in());
324 if (canonical_host_ip == NULL)
327 /* If not on socket, return UNKNOWN. */
328 canonical_host_ip = xstrdup("UNKNOWN");
331 return canonical_host_ip;
335 get_remote_name_or_ip(u_int utmp_len, int use_dns)
337 static const char *remote = "";
339 remote = get_canonical_hostname(use_dns);
340 if (utmp_len == 0 || strlen(remote) > utmp_len)
341 remote = get_remote_ipaddr();
345 /* Returns the local/remote port for the socket. */
348 get_sock_port(int sock, int local)
350 struct sockaddr_storage from;
352 char strport[NI_MAXSERV];
355 /* Get IP address of client. */
356 fromlen = sizeof(from);
357 memset(&from, 0, sizeof(from));
359 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
360 error("getsockname failed: %.100s", strerror(errno));
364 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
365 debug("getpeername failed: %.100s", strerror(errno));
370 /* Work around Linux IPv6 weirdness */
371 if (from.ss_family == AF_INET6)
372 fromlen = sizeof(struct sockaddr_in6);
374 /* Return port number. */
375 if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
376 strport, sizeof(strport), NI_NUMERICSERV)) != 0)
377 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s",
378 ssh_gai_strerror(r));
379 return atoi(strport);
382 /* Returns remote/local port number for the current connection. */
388 * If the connection is not a socket, return 65535. This is
389 * intentionally chosen to be an unprivileged port number.
391 if (!packet_connection_is_on_socket())
394 /* Get socket and return the port number. */
395 return get_sock_port(packet_get_connection_in(), local);
399 get_peer_port(int sock)
401 return get_sock_port(sock, 0);
405 get_remote_port(void)
407 static int port = -1;
409 /* Cache to avoid getpeername() on a dead connection */
423 resolve_localhost(char **host)
425 struct hostent *hostinfo;
427 hostinfo = gethostbyname(*host);
428 if (hostinfo == NULL || hostinfo->h_name == NULL) {
429 debug("gethostbyname(%s) failed", *host);
432 if (hostinfo->h_addrtype == AF_INET) {
434 addr = *(struct in_addr *)(hostinfo->h_addr);
435 if (ntohl(addr.s_addr) == INADDR_LOOPBACK) {
436 char buf[MAXHOSTNAMELEN];
437 if (gethostname(buf, sizeof(buf)) < 0) {
438 debug("gethostname() failed");
441 hostinfo = gethostbyname(buf);
443 if (hostinfo == NULL || hostinfo->h_name == NULL) {
444 *host = xstrdup(buf);
446 *host = xstrdup(hostinfo->h_name);