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Commit | Line | Data |
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8efc0c15 | 1 | /* |
5260325f | 2 | * |
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 | */ | |
8efc0c15 | 15 | |
16 | #include "includes.h" | |
17 | RCSID("$Id$"); | |
18 | ||
19 | #include "packet.h" | |
20 | #include "xmalloc.h" | |
21 | #include "ssh.h" | |
22 | ||
aa3378df | 23 | /* |
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 | */ | |
8efc0c15 | 27 | |
5260325f | 28 | char * |
29 | get_remote_hostname(int socket) | |
8efc0c15 | 30 | { |
5260325f | 31 | struct sockaddr_in from; |
32 | int fromlen, i; | |
33 | struct hostent *hp; | |
34 | char name[MAXHOSTNAMELEN]; | |
35 | ||
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)); | |
41 | fatal_cleanup(); | |
42 | } | |
43 | /* 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 | ||
aa3378df | 57 | /* |
58 | * Convert it to all lowercase (which is expected by the rest | |
59 | * of this software). | |
60 | */ | |
5260325f | 61 | for (i = 0; name[i]; i++) |
62 | if (isupper(name[i])) | |
63 | name[i] = tolower(name[i]); | |
64 | ||
aa3378df | 65 | /* |
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 | */ | |
5260325f | 74 | 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; | |
aa3378df | 85 | /* |
86 | * If we reached the end of the list, the address was not | |
87 | * there. | |
88 | */ | |
5260325f | 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; | |
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); | |
8efc0c15 | 101 | } |
5260325f | 102 | |
103 | check_ip_options: | |
104 | ||
aa3378df | 105 | /* |
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 | */ | |
8efc0c15 | 116 | { |
5260325f | 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 | } | |
8efc0c15 | 138 | } |
5260325f | 139 | |
140 | return xstrdup(name); | |
8efc0c15 | 141 | } |
142 | ||
143 | static char *canonical_host_name = NULL; | |
144 | static char *canonical_host_ip = NULL; | |
145 | ||
aa3378df | 146 | /* |
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 | */ | |
8efc0c15 | 151 | |
5260325f | 152 | const char * |
153 | get_canonical_hostname() | |
8efc0c15 | 154 | { |
5260325f | 155 | /* Check if we have previously retrieved this same name. */ |
156 | if (canonical_host_name != NULL) | |
157 | return canonical_host_name; | |
8efc0c15 | 158 | |
5260325f | 159 | /* 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"); | |
8efc0c15 | 164 | |
5260325f | 165 | return canonical_host_name; |
8efc0c15 | 166 | } |
167 | ||
aa3378df | 168 | /* |
169 | * Returns the IP-address of the remote host as a string. The returned | |
170 | * string need not be freed. | |
171 | */ | |
8efc0c15 | 172 | |
5260325f | 173 | const char * |
174 | get_remote_ipaddr() | |
8efc0c15 | 175 | { |
5260325f | 176 | struct sockaddr_in from; |
177 | int fromlen, socket; | |
178 | ||
aa3378df | 179 | /* Check whether we have chached the name. */ |
5260325f | 180 | if (canonical_host_ip != NULL) |
181 | return canonical_host_ip; | |
182 | ||
183 | /* 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(); | |
190 | ||
191 | /* 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)); | |
200 | ||
201 | /* Return ip address string. */ | |
202 | return canonical_host_ip; | |
8efc0c15 | 203 | } |
204 | ||
205 | /* Returns the port of the peer of the socket. */ | |
206 | ||
5260325f | 207 | int |
208 | get_peer_port(int sock) | |
8efc0c15 | 209 | { |
5260325f | 210 | struct sockaddr_in from; |
211 | int fromlen; | |
212 | ||
213 | /* 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); | |
8efc0c15 | 222 | } |
223 | ||
224 | /* Returns the port number of the remote host. */ | |
225 | ||
5260325f | 226 | int |
227 | get_remote_port() | |
8efc0c15 | 228 | { |
5260325f | 229 | int socket; |
8efc0c15 | 230 | |
aa3378df | 231 | /* |
232 | * If the connection is not a socket, return 65535. This is | |
233 | * intentionally chosen to be an unprivileged port number. | |
234 | */ | |
5260325f | 235 | if (packet_get_connection_in() != packet_get_connection_out()) |
236 | return 65535; | |
8efc0c15 | 237 | |
5260325f | 238 | /* Get client socket. */ |
239 | socket = packet_get_connection_in(); | |
8efc0c15 | 240 | |
5260325f | 241 | /* Get and return the peer port number. */ |
242 | return get_peer_port(socket); | |
8efc0c15 | 243 | } |