5 * Author: Tatu Ylonen <ylo@cs.hut.fi>
7 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
10 * Created: Sun Jul 2 17:52:22 1995 ylo
12 * Functions for returning the canonical host name of the remote site.
24 * Return the canonical name of the host at the other end of the socket. The
25 * caller should free the returned string with xfree.
29 get_remote_hostname(int socket)
31 struct sockaddr_in from;
34 char name[MAXHOSTNAMELEN];
36 /* Get IP address of client. */
37 fromlen = sizeof(from);
38 memset(&from, 0, sizeof(from));
39 if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) {
40 debug("getpeername failed: %.100s", strerror(errno));
43 /* Map the IP address to a host name. */
44 hp = gethostbyaddr((char *) &from.sin_addr, sizeof(struct in_addr),
47 /* Got host name, find canonic host name. */
48 if (strchr(hp->h_name, '.') != 0)
49 strlcpy(name, hp->h_name, sizeof(name));
50 else if (hp->h_aliases != 0
51 && hp->h_aliases[0] != 0
52 && strchr(hp->h_aliases[0], '.') != 0)
53 strlcpy(name, hp->h_aliases[0], sizeof(name));
55 strlcpy(name, hp->h_name, sizeof(name));
58 * Convert it to all lowercase (which is expected by the rest
61 for (i = 0; name[i]; i++)
63 name[i] = tolower(name[i]);
66 * Map it back to an IP address and check that the given
67 * address actually is an address of this host. This is
68 * necessary because anyone with access to a name server can
69 * define arbitrary names for an IP address. Mapping from
70 * name to IP address can be trusted better (but can still be
71 * fooled if the intruder has access to the name server of
74 hp = gethostbyname(name);
76 log("reverse mapping checking gethostbyname for %.700s failed - POSSIBLE BREAKIN ATTEMPT!", name);
77 strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
78 goto check_ip_options;
80 /* Look for the address from the list of addresses. */
81 for (i = 0; hp->h_addr_list[i]; i++)
82 if (memcmp(hp->h_addr_list[i], &from.sin_addr, sizeof(from.sin_addr))
86 * If we reached the end of the list, the address was not
89 if (!hp->h_addr_list[i]) {
90 /* Address not found for the host name. */
91 log("Address %.100s maps to %.600s, but this does not map back to the address - POSSIBLE BREAKIN ATTEMPT!",
92 inet_ntoa(from.sin_addr), name);
93 strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
94 goto check_ip_options;
96 /* Address was found for the host name. We accept the host name. */
98 /* Host name not found. Use ascii representation of the address. */
99 strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
100 log("Could not reverse map address %.100s.", name);
106 * If IP options are supported, make sure there are none (log and
107 * disconnect them if any are found). Basically we are worried about
108 * source routing; it can be used to pretend you are somebody
109 * (ip-address) you are not. That itself may be "almost acceptable"
110 * under certain circumstances, but rhosts autentication is useless
111 * if source routing is accepted. Notice also that if we just dropped
112 * source routing here, the other side could use IP spoofing to do
113 * rest of the interaction and could still bypass security. So we
114 * exit here if we detect any IP options.
117 unsigned char options[200], *ucp;
118 char text[1024], *cp;
119 int option_size, ipproto;
122 if ((ip = getprotobyname("ip")) != NULL)
123 ipproto = ip->p_proto;
125 ipproto = IPPROTO_IP;
126 option_size = sizeof(options);
127 if (getsockopt(0, ipproto, IP_OPTIONS, (char *) options,
128 &option_size) >= 0 && option_size != 0) {
130 /* Note: "text" buffer must be at least 3x as big as options. */
131 for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3)
132 sprintf(cp, " %2.2x", *ucp);
133 log("Connection from %.100s with IP options:%.800s",
134 inet_ntoa(from.sin_addr), text);
135 packet_disconnect("Connection from %.100s with IP options:%.800s",
136 inet_ntoa(from.sin_addr), text);
140 return xstrdup(name);
143 static char *canonical_host_name = NULL;
144 static char *canonical_host_ip = NULL;
146 /* Returns 1 if remote host is connected via socket, 0 if not. */
149 peer_connection_is_on_socket()
151 struct sockaddr_in from;
153 int in = packet_get_connection_in();
154 int out = packet_get_connection_out();
156 /* filedescriptors in and out are the same, so it's a socket */
159 fromlen = sizeof(from);
160 memset(&from, 0, sizeof(from));
161 if (getpeername(in, (struct sockaddr *) & from, &fromlen) < 0)
163 if (from.sin_family != AF_INET)
170 * Return the canonical name of the host in the other side of the current
171 * connection. The host name is cached, so it is efficient to call this
176 get_canonical_hostname()
178 /* Check if we have previously retrieved this same name. */
179 if (canonical_host_name != NULL)
180 return canonical_host_name;
182 /* Get the real hostname if socket; otherwise return UNKNOWN. */
183 if (peer_connection_is_on_socket())
184 canonical_host_name = get_remote_hostname(packet_get_connection_in());
186 canonical_host_name = xstrdup("UNKNOWN");
188 return canonical_host_name;
192 * Returns the IP-address of the remote host as a string. The returned
193 * string need not be freed.
199 struct sockaddr_in from;
202 /* Check whether we have chached the name. */
203 if (canonical_host_ip != NULL)
204 return canonical_host_ip;
206 /* If not a socket, return UNKNOWN. */
207 if (!peer_connection_is_on_socket()) {
208 canonical_host_ip = xstrdup("UNKNOWN");
209 return canonical_host_ip;
211 /* Get client socket. */
212 socket = packet_get_connection_in();
214 /* Get IP address of client. */
215 fromlen = sizeof(from);
216 memset(&from, 0, sizeof(from));
217 if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) {
218 debug("getpeername failed: %.100s", strerror(errno));
221 /* Get the IP address in ascii. */
222 canonical_host_ip = xstrdup(inet_ntoa(from.sin_addr));
224 /* Return ip address string. */
225 return canonical_host_ip;
228 /* Returns the port of the peer of the socket. */
231 get_peer_port(int sock)
233 struct sockaddr_in from;
236 /* Get IP address of client. */
237 fromlen = sizeof(from);
238 memset(&from, 0, sizeof(from));
239 if (getpeername(sock, (struct sockaddr *) & from, &fromlen) < 0) {
240 debug("getpeername failed: %.100s", strerror(errno));
243 /* Return port number. */
244 return ntohs(from.sin_port);
247 /* Returns the port number of the remote host. */
255 * If the connection is not a socket, return 65535. This is
256 * intentionally chosen to be an unprivileged port number.
258 if (!peer_connection_is_on_socket())
261 /* Get client socket. */
262 socket = packet_get_connection_in();
264 /* Get and return the peer port number. */
265 return get_peer_port(socket);