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 1.48 2005/12/28 22:46:06 stevesk 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 sock, int use_dns)
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(sock, (struct sockaddr *)&from, &fromlen) < 0) {
42 debug("getpeername failed: %.100s", strerror(errno));
46 ipv64_normalise_mapped(&from, &fromlen);
48 if (from.ss_family == AF_INET6)
49 fromlen = sizeof(struct sockaddr_in6);
51 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
52 NULL, 0, NI_NUMERICHOST) != 0)
53 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
55 if (from.ss_family == AF_INET)
56 check_ip_options(sock, ntop);
61 debug3("Trying to reverse map address %.100s.", ntop);
62 /* Map the IP address to a host name. */
63 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
64 NULL, 0, NI_NAMEREQD) != 0) {
65 /* Host name not found. Use ip address. */
70 * if reverse lookup result looks like a numeric hostname,
71 * someone is trying to trick us by PTR record like following:
72 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
74 memset(&hints, 0, sizeof(hints));
75 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
76 hints.ai_flags = AI_NUMERICHOST;
77 if (getaddrinfo(name, "0", &hints, &ai) == 0) {
78 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
85 * Convert it to all lowercase (which is expected by the rest
88 for (i = 0; name[i]; i++)
90 name[i] = tolower(name[i]);
92 * Map it back to an IP address and check that the given
93 * address actually is an address of this host. This is
94 * necessary because anyone with access to a name server can
95 * define arbitrary names for an IP address. Mapping from
96 * name to IP address can be trusted better (but can still be
97 * fooled if the intruder has access to the name server of
100 memset(&hints, 0, sizeof(hints));
101 hints.ai_family = from.ss_family;
102 hints.ai_socktype = SOCK_STREAM;
103 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
104 logit("reverse mapping checking getaddrinfo for %.700s "
105 "failed - POSSIBLE BREAK-IN ATTEMPT!", name);
106 return xstrdup(ntop);
108 /* Look for the address from the list of addresses. */
109 for (ai = aitop; ai; ai = ai->ai_next) {
110 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
111 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
112 (strcmp(ntop, ntop2) == 0))
116 /* If we reached the end of the list, the address was not there. */
118 /* Address not found for the host name. */
119 logit("Address %.100s maps to %.600s, but this does not "
120 "map back to the address - POSSIBLE BREAK-IN ATTEMPT!",
122 return xstrdup(ntop);
124 return xstrdup(name);
128 * If IP options are supported, make sure there are none (log and
129 * disconnect them if any are found). Basically we are worried about
130 * source routing; it can be used to pretend you are somebody
131 * (ip-address) you are not. That itself may be "almost acceptable"
132 * under certain circumstances, but rhosts autentication is useless
133 * if source routing is accepted. Notice also that if we just dropped
134 * source routing here, the other side could use IP spoofing to do
135 * rest of the interaction and could still bypass security. So we
136 * exit here if we detect any IP options.
140 check_ip_options(int sock, char *ipaddr)
144 char text[sizeof(options) * 3 + 1];
145 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(sock, ipproto, IP_OPTIONS, options,
156 &option_size) >= 0 && option_size != 0) {
158 for (i = 0; i < option_size; i++)
159 snprintf(text + i*3, sizeof(text) - i*3,
160 " %2.2x", options[i]);
161 fatal("Connection from %.100s with IP options:%.800s",
164 #endif /* IP_OPTIONS */
168 ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
170 struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr;
171 struct sockaddr_in *a4 = (struct sockaddr_in *)addr;
172 struct in_addr inaddr;
175 if (addr->ss_family != AF_INET6 ||
176 !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr))
179 debug3("Normalising mapped IPv4 in IPv6 address");
181 memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr));
182 port = a6->sin6_port;
184 memset(addr, 0, sizeof(*a4));
186 a4->sin_family = AF_INET;
188 memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr));
193 * Return the canonical name of the host in the other side of the current
194 * connection. The host name is cached, so it is efficient to call this
199 get_canonical_hostname(int use_dns)
202 static char *canonical_host_name = NULL;
203 static char *remote_ip = NULL;
205 /* Check if we have previously retrieved name with same option. */
206 if (use_dns && canonical_host_name != NULL)
207 return canonical_host_name;
208 if (!use_dns && remote_ip != NULL)
211 /* Get the real hostname if socket; otherwise return UNKNOWN. */
212 if (packet_connection_is_on_socket())
213 host = get_remote_hostname(packet_get_connection_in(), use_dns);
218 canonical_host_name = host;
225 * Returns the local/remote IP-address/hostname of socket as a string.
226 * The returned string must be freed.
229 get_socket_address(int sock, int remote, int flags)
231 struct sockaddr_storage addr;
233 char ntop[NI_MAXHOST];
236 /* Get IP address of client. */
237 addrlen = sizeof(addr);
238 memset(&addr, 0, sizeof(addr));
241 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen)
245 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen)
250 /* Work around Linux IPv6 weirdness */
251 if (addr.ss_family == AF_INET6)
252 addrlen = sizeof(struct sockaddr_in6);
254 ipv64_normalise_mapped(&addr, &addrlen);
256 /* Get the address in ascii. */
257 if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
258 sizeof(ntop), NULL, 0, flags)) != 0) {
259 error("get_socket_address: getnameinfo %d failed: %s", flags,
260 r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r));
263 return xstrdup(ntop);
267 get_peer_ipaddr(int sock)
271 if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL)
273 return xstrdup("UNKNOWN");
277 get_local_ipaddr(int sock)
281 if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL)
283 return xstrdup("UNKNOWN");
287 get_local_name(int sock)
289 return get_socket_address(sock, 0, NI_NAMEREQD);
293 * Returns the IP-address of the remote host as a string. The returned
294 * string must not be freed.
298 get_remote_ipaddr(void)
300 static char *canonical_host_ip = NULL;
302 /* Check whether we have cached the ipaddr. */
303 if (canonical_host_ip == NULL) {
304 if (packet_connection_is_on_socket()) {
306 get_peer_ipaddr(packet_get_connection_in());
307 if (canonical_host_ip == NULL)
310 /* If not on socket, return UNKNOWN. */
311 canonical_host_ip = xstrdup("UNKNOWN");
314 return canonical_host_ip;
318 get_remote_name_or_ip(u_int utmp_len, int use_dns)
320 static const char *remote = "";
322 remote = get_canonical_hostname(use_dns);
323 if (utmp_len == 0 || strlen(remote) > utmp_len)
324 remote = get_remote_ipaddr();
328 /* Returns the local/remote port for the socket. */
331 get_sock_port(int sock, int local)
333 struct sockaddr_storage from;
335 char strport[NI_MAXSERV];
338 /* Get IP address of client. */
339 fromlen = sizeof(from);
340 memset(&from, 0, sizeof(from));
342 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
343 error("getsockname failed: %.100s", strerror(errno));
347 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
348 debug("getpeername failed: %.100s", strerror(errno));
353 /* Work around Linux IPv6 weirdness */
354 if (from.ss_family == AF_INET6)
355 fromlen = sizeof(struct sockaddr_in6);
357 /* Return port number. */
358 if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
359 strport, sizeof(strport), NI_NUMERICSERV)) != 0)
360 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s",
361 r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r));
362 return atoi(strport);
365 /* Returns remote/local port number for the current connection. */
371 * If the connection is not a socket, return 65535. This is
372 * intentionally chosen to be an unprivileged port number.
374 if (!packet_connection_is_on_socket())
377 /* Get socket and return the port number. */
378 return get_sock_port(packet_get_connection_in(), local);
382 get_peer_port(int sock)
384 return get_sock_port(sock, 0);
388 get_remote_port(void)
390 static int port = -1;
392 /* Cache to avoid getpeername() on a dead connection */