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Damien Millerd4a8b7e1999-10-27 13:42:43 +10001/*
Damien Miller95def091999-11-25 00:26:21 +11002 *
3 * canohost.c
4 *
5 * Author: Tatu Ylonen <ylo@cs.hut.fi>
6 *
7 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
8 * All rights reserved
9 *
10 * Created: Sun Jul 2 17:52:22 1995 ylo
11 *
12 * Functions for returning the canonical host name of the remote site.
13 *
14 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100015
16#include "includes.h"
Damien Miller5428f641999-11-25 11:54:57 +110017RCSID("$Id: canohost.c,v 1.4 1999/11/25 00:54:58 damien Exp $");
Damien Millerd4a8b7e1999-10-27 13:42:43 +100018
19#include "packet.h"
20#include "xmalloc.h"
21#include "ssh.h"
22
Damien Miller5428f641999-11-25 11:54:57 +110023/*
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.
26 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100027
Damien Miller95def091999-11-25 00:26:21 +110028char *
29get_remote_hostname(int socket)
Damien Millerd4a8b7e1999-10-27 13:42:43 +100030{
Damien Miller95def091999-11-25 00:26:21 +110031 struct sockaddr_in from;
32 int fromlen, i;
33 struct hostent *hp;
34 char name[MAXHOSTNAMELEN];
Damien Millerd4a8b7e1999-10-27 13:42:43 +100035
Damien Miller95def091999-11-25 00:26:21 +110036 /* 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));
41 fatal_cleanup();
Damien Millerd4a8b7e1999-10-27 13:42:43 +100042 }
Damien Miller95def091999-11-25 00:26:21 +110043 /* Map the IP address to a host name. */
44 hp = gethostbyaddr((char *) &from.sin_addr, sizeof(struct in_addr),
45 from.sin_family);
46 if (hp) {
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));
54 else
55 strlcpy(name, hp->h_name, sizeof(name));
56
Damien Miller5428f641999-11-25 11:54:57 +110057 /*
58 * Convert it to all lowercase (which is expected by the rest
59 * of this software).
60 */
Damien Miller95def091999-11-25 00:26:21 +110061 for (i = 0; name[i]; i++)
62 if (isupper(name[i]))
63 name[i] = tolower(name[i]);
64
Damien Miller5428f641999-11-25 11:54:57 +110065 /*
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
72 * the domain).
73 */
Damien Miller95def091999-11-25 00:26:21 +110074 hp = gethostbyname(name);
75 if (!hp) {
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;
79 }
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))
83 == 0)
84 break;
Damien Miller5428f641999-11-25 11:54:57 +110085 /*
86 * If we reached the end of the list, the address was not
87 * there.
88 */
Damien Miller95def091999-11-25 00:26:21 +110089 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;
95 }
96 /* Address was found for the host name. We accept the host name. */
97 } else {
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);
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000101 }
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000102
Damien Miller95def091999-11-25 00:26:21 +1100103check_ip_options:
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000104
Damien Miller5428f641999-11-25 11:54:57 +1100105 /*
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.
115 */
Damien Miller95def091999-11-25 00:26:21 +1100116 {
117 unsigned char options[200], *ucp;
118 char text[1024], *cp;
119 int option_size, ipproto;
120 struct protoent *ip;
121
122 if ((ip = getprotobyname("ip")) != NULL)
123 ipproto = ip->p_proto;
124 else
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) {
129 cp = text;
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);
137 }
138 }
139
140 return xstrdup(name);
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000141}
142
143static char *canonical_host_name = NULL;
144static char *canonical_host_ip = NULL;
145
Damien Miller5428f641999-11-25 11:54:57 +1100146/*
147 * Return the canonical name of the host in the other side of the current
148 * connection. The host name is cached, so it is efficient to call this
149 * several times.
150 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000151
Damien Miller95def091999-11-25 00:26:21 +1100152const char *
153get_canonical_hostname()
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000154{
Damien Miller95def091999-11-25 00:26:21 +1100155 /* Check if we have previously retrieved this same name. */
156 if (canonical_host_name != NULL)
157 return canonical_host_name;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000158
Damien Miller95def091999-11-25 00:26:21 +1100159 /* Get the real hostname if socket; otherwise return UNKNOWN. */
160 if (packet_get_connection_in() == packet_get_connection_out())
161 canonical_host_name = get_remote_hostname(packet_get_connection_in());
162 else
163 canonical_host_name = xstrdup("UNKNOWN");
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000164
Damien Miller95def091999-11-25 00:26:21 +1100165 return canonical_host_name;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000166}
167
Damien Miller5428f641999-11-25 11:54:57 +1100168/*
169 * Returns the IP-address of the remote host as a string. The returned
170 * string need not be freed.
171 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000172
Damien Miller95def091999-11-25 00:26:21 +1100173const char *
174get_remote_ipaddr()
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000175{
Damien Miller95def091999-11-25 00:26:21 +1100176 struct sockaddr_in from;
177 int fromlen, socket;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000178
Damien Miller5428f641999-11-25 11:54:57 +1100179 /* Check whether we have chached the name. */
Damien Miller95def091999-11-25 00:26:21 +1100180 if (canonical_host_ip != NULL)
181 return canonical_host_ip;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000182
Damien Miller95def091999-11-25 00:26:21 +1100183 /* If not a socket, return UNKNOWN. */
184 if (packet_get_connection_in() != packet_get_connection_out()) {
185 canonical_host_ip = xstrdup("UNKNOWN");
186 return canonical_host_ip;
187 }
188 /* Get client socket. */
189 socket = packet_get_connection_in();
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000190
Damien Miller95def091999-11-25 00:26:21 +1100191 /* Get IP address of client. */
192 fromlen = sizeof(from);
193 memset(&from, 0, sizeof(from));
194 if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) {
195 debug("getpeername failed: %.100s", strerror(errno));
196 fatal_cleanup();
197 }
198 /* Get the IP address in ascii. */
199 canonical_host_ip = xstrdup(inet_ntoa(from.sin_addr));
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000200
Damien Miller95def091999-11-25 00:26:21 +1100201 /* Return ip address string. */
202 return canonical_host_ip;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000203}
204
205/* Returns the port of the peer of the socket. */
206
Damien Miller95def091999-11-25 00:26:21 +1100207int
208get_peer_port(int sock)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000209{
Damien Miller95def091999-11-25 00:26:21 +1100210 struct sockaddr_in from;
211 int fromlen;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000212
Damien Miller95def091999-11-25 00:26:21 +1100213 /* Get IP address of client. */
214 fromlen = sizeof(from);
215 memset(&from, 0, sizeof(from));
216 if (getpeername(sock, (struct sockaddr *) & from, &fromlen) < 0) {
217 debug("getpeername failed: %.100s", strerror(errno));
218 fatal_cleanup();
219 }
220 /* Return port number. */
221 return ntohs(from.sin_port);
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000222}
223
224/* Returns the port number of the remote host. */
225
Damien Miller95def091999-11-25 00:26:21 +1100226int
227get_remote_port()
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000228{
Damien Miller95def091999-11-25 00:26:21 +1100229 int socket;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000230
Damien Miller5428f641999-11-25 11:54:57 +1100231 /*
232 * If the connection is not a socket, return 65535. This is
233 * intentionally chosen to be an unprivileged port number.
234 */
Damien Miller95def091999-11-25 00:26:21 +1100235 if (packet_get_connection_in() != packet_get_connection_out())
236 return 65535;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000237
Damien Miller95def091999-11-25 00:26:21 +1100238 /* Get client socket. */
239 socket = packet_get_connection_in();
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000240
Damien Miller95def091999-11-25 00:26:21 +1100241 /* Get and return the peer port number. */
242 return get_peer_port(socket);
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000243}