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1 | /* | |
2 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
3 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
4 | * All rights reserved | |
5 | * Functions for returning the canonical host name of the remote site. | |
6 | * | |
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". | |
12 | */ | |
13 | ||
14 | #include "includes.h" | |
15 | RCSID("$OpenBSD: canohost.c,v 1.23 2001/02/10 01:33:32 markus Exp $"); | |
16 | ||
17 | #include "packet.h" | |
18 | #include "xmalloc.h" | |
19 | #include "log.h" | |
20 | #include "canohost.h" | |
21 | ||
22 | void check_ip_options(int socket, char *ipaddr); | |
23 | ||
24 | /* | |
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. | |
27 | */ | |
28 | ||
29 | char * | |
30 | get_remote_hostname(int socket, int reverse_mapping_check) | |
31 | { | |
32 | struct sockaddr_storage from; | |
33 | int i; | |
34 | socklen_t fromlen; | |
35 | struct addrinfo hints, *ai, *aitop; | |
36 | char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST]; | |
37 | ||
38 | /* Get IP address of client. */ | |
39 | fromlen = sizeof(from); | |
40 | memset(&from, 0, sizeof(from)); | |
41 | if (getpeername(socket, (struct sockaddr *) &from, &fromlen) < 0) { | |
42 | debug("getpeername failed: %.100s", strerror(errno)); | |
43 | fatal_cleanup(); | |
44 | } | |
45 | #ifdef IPV4_IN_IPV6 | |
46 | if (from.ss_family == AF_INET6) { | |
47 | struct sockaddr_in6 *from6 = (struct sockaddr_in6 *)&from; | |
48 | ||
49 | /* Detect IPv4 in IPv6 mapped address and convert it to */ | |
50 | /* plain (AF_INET) IPv4 address */ | |
51 | if (IN6_IS_ADDR_V4MAPPED(&from6->sin6_addr)) { | |
52 | struct sockaddr_in *from4 = (struct sockaddr_in *)&from; | |
53 | struct in_addr addr; | |
54 | u_int16_t port; | |
55 | ||
56 | memcpy(&addr, ((char *)&from6->sin6_addr) + 12, sizeof(addr)); | |
57 | port = from6->sin6_port; | |
58 | ||
59 | memset(&from, 0, sizeof(from)); | |
60 | ||
61 | from4->sin_family = AF_INET; | |
62 | memcpy(&from4->sin_addr, &addr, sizeof(addr)); | |
63 | from4->sin_port = port; | |
64 | } | |
65 | } | |
66 | #endif | |
67 | if (from.ss_family == AF_INET) | |
68 | check_ip_options(socket, ntop); | |
69 | ||
70 | if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop), | |
71 | NULL, 0, NI_NUMERICHOST) != 0) | |
72 | fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed"); | |
73 | ||
74 | debug("Trying to reverse map address %.100s.", ntop); | |
75 | /* Map the IP address to a host name. */ | |
76 | if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), | |
77 | NULL, 0, NI_NAMEREQD) != 0) { | |
78 | /* Host name not found. Use ip address. */ | |
79 | log("Could not reverse map address %.100s.", ntop); | |
80 | return xstrdup(ntop); | |
81 | } | |
82 | ||
83 | /* Got host name. */ | |
84 | name[sizeof(name) - 1] = '\0'; | |
85 | /* | |
86 | * Convert it to all lowercase (which is expected by the rest | |
87 | * of this software). | |
88 | */ | |
89 | for (i = 0; name[i]; i++) | |
90 | if (isupper(name[i])) | |
91 | name[i] = tolower(name[i]); | |
92 | ||
93 | if (!reverse_mapping_check) | |
94 | return xstrdup(name); | |
95 | /* | |
96 | * Map it back to an IP address and check that the given | |
97 | * address actually is an address of this host. This is | |
98 | * necessary because anyone with access to a name server can | |
99 | * define arbitrary names for an IP address. Mapping from | |
100 | * name to IP address can be trusted better (but can still be | |
101 | * fooled if the intruder has access to the name server of | |
102 | * the domain). | |
103 | */ | |
104 | memset(&hints, 0, sizeof(hints)); | |
105 | hints.ai_family = from.ss_family; | |
106 | hints.ai_socktype = SOCK_STREAM; | |
107 | if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { | |
108 | log("reverse mapping checking getaddrinfo for %.700s " | |
109 | "failed - POSSIBLE BREAKIN ATTEMPT!", name); | |
110 | return xstrdup(ntop); | |
111 | } | |
112 | /* Look for the address from the list of addresses. */ | |
113 | for (ai = aitop; ai; ai = ai->ai_next) { | |
114 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, | |
115 | sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && | |
116 | (strcmp(ntop, ntop2) == 0)) | |
117 | break; | |
118 | } | |
119 | freeaddrinfo(aitop); | |
120 | /* If we reached the end of the list, the address was not there. */ | |
121 | if (!ai) { | |
122 | /* Address not found for the host name. */ | |
123 | log("Address %.100s maps to %.600s, but this does not " | |
124 | "map back to the address - POSSIBLE BREAKIN ATTEMPT!", | |
125 | ntop, name); | |
126 | return xstrdup(ntop); | |
127 | } | |
128 | return xstrdup(name); | |
129 | } | |
130 | ||
131 | /* | |
132 | * If IP options are supported, make sure there are none (log and | |
133 | * disconnect them if any are found). Basically we are worried about | |
134 | * source routing; it can be used to pretend you are somebody | |
135 | * (ip-address) you are not. That itself may be "almost acceptable" | |
136 | * under certain circumstances, but rhosts autentication is useless | |
137 | * if source routing is accepted. Notice also that if we just dropped | |
138 | * source routing here, the other side could use IP spoofing to do | |
139 | * rest of the interaction and could still bypass security. So we | |
140 | * exit here if we detect any IP options. | |
141 | */ | |
142 | /* IPv4 only */ | |
143 | void | |
144 | check_ip_options(int socket, char *ipaddr) | |
145 | { | |
146 | u_char options[200]; | |
147 | char text[sizeof(options) * 3 + 1]; | |
148 | socklen_t option_size; | |
149 | int i, ipproto; | |
150 | struct protoent *ip; | |
151 | ||
152 | if ((ip = getprotobyname("ip")) != NULL) | |
153 | ipproto = ip->p_proto; | |
154 | else | |
155 | ipproto = IPPROTO_IP; | |
156 | option_size = sizeof(options); | |
157 | if (getsockopt(socket, ipproto, IP_OPTIONS, (void *)options, | |
158 | &option_size) >= 0 && option_size != 0) { | |
159 | text[0] = '\0'; | |
160 | for (i = 0; i < option_size; i++) | |
161 | snprintf(text + i*3, sizeof(text) - i*3, | |
162 | " %2.2x", options[i]); | |
163 | log("Connection from %.100s with IP options:%.800s", | |
164 | ipaddr, text); | |
165 | packet_disconnect("Connection from %.100s with IP options:%.800s", | |
166 | ipaddr, text); | |
167 | } | |
168 | } | |
169 | ||
170 | /* | |
171 | * Return the canonical name of the host in the other side of the current | |
172 | * connection. The host name is cached, so it is efficient to call this | |
173 | * several times. | |
174 | */ | |
175 | ||
176 | const char * | |
177 | get_canonical_hostname(int reverse_mapping_check) | |
178 | { | |
179 | static char *canonical_host_name = NULL; | |
180 | static int reverse_mapping_checked = 0; | |
181 | ||
182 | /* Check if we have previously retrieved name with same option. */ | |
183 | if (canonical_host_name != NULL) { | |
184 | if (reverse_mapping_checked != reverse_mapping_check) | |
185 | xfree(canonical_host_name); | |
186 | else | |
187 | return canonical_host_name; | |
188 | } | |
189 | ||
190 | /* Get the real hostname if socket; otherwise return UNKNOWN. */ | |
191 | if (packet_connection_is_on_socket()) | |
192 | canonical_host_name = get_remote_hostname( | |
193 | packet_get_connection_in(), reverse_mapping_check); | |
194 | else | |
195 | canonical_host_name = xstrdup("UNKNOWN"); | |
196 | ||
197 | reverse_mapping_checked = reverse_mapping_check; | |
198 | return canonical_host_name; | |
199 | } | |
200 | ||
201 | /* | |
202 | * Returns the remote IP-address of socket as a string. The returned | |
203 | * string must be freed. | |
204 | */ | |
205 | ||
206 | char * | |
207 | get_peer_ipaddr(int socket) | |
208 | { | |
209 | struct sockaddr_storage from; | |
210 | socklen_t fromlen; | |
211 | char ntop[NI_MAXHOST]; | |
212 | ||
213 | /* Get IP address of client. */ | |
214 | fromlen = sizeof(from); | |
215 | memset(&from, 0, sizeof(from)); | |
216 | if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) { | |
217 | debug("get_peer_ipaddr: getpeername failed: %.100s", strerror(errno)); | |
218 | return NULL; | |
219 | } | |
220 | /* Get the IP address in ascii. */ | |
221 | if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop), | |
222 | NULL, 0, NI_NUMERICHOST) != 0) { | |
223 | error("get_peer_ipaddr: getnameinfo NI_NUMERICHOST failed"); | |
224 | return NULL; | |
225 | } | |
226 | return xstrdup(ntop); | |
227 | } | |
228 | ||
229 | /* | |
230 | * Returns the IP-address of the remote host as a string. The returned | |
231 | * string must not be freed. | |
232 | */ | |
233 | ||
234 | const char * | |
235 | get_remote_ipaddr() | |
236 | { | |
237 | static char *canonical_host_ip = NULL; | |
238 | ||
239 | /* Check whether we have cached the ipaddr. */ | |
240 | if (canonical_host_ip == NULL) { | |
241 | if (packet_connection_is_on_socket()) { | |
242 | canonical_host_ip = | |
243 | get_peer_ipaddr(packet_get_connection_in()); | |
244 | if (canonical_host_ip == NULL) | |
245 | fatal_cleanup(); | |
246 | } else { | |
247 | /* If not on socket, return UNKNOWN. */ | |
248 | canonical_host_ip = xstrdup("UNKNOWN"); | |
249 | } | |
250 | } | |
251 | return canonical_host_ip; | |
252 | } | |
253 | ||
254 | /* Returns the local/remote port for the socket. */ | |
255 | ||
256 | int | |
257 | get_sock_port(int sock, int local) | |
258 | { | |
259 | struct sockaddr_storage from; | |
260 | socklen_t fromlen; | |
261 | char strport[NI_MAXSERV]; | |
262 | ||
263 | /* Get IP address of client. */ | |
264 | fromlen = sizeof(from); | |
265 | memset(&from, 0, sizeof(from)); | |
266 | if (local) { | |
267 | if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) { | |
268 | error("getsockname failed: %.100s", strerror(errno)); | |
269 | return 0; | |
270 | } | |
271 | } else { | |
272 | if (getpeername(sock, (struct sockaddr *) & from, &fromlen) < 0) { | |
273 | debug("getpeername failed: %.100s", strerror(errno)); | |
274 | fatal_cleanup(); | |
275 | } | |
276 | } | |
277 | /* Return port number. */ | |
278 | if (getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0, | |
279 | strport, sizeof(strport), NI_NUMERICSERV) != 0) | |
280 | fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed"); | |
281 | return atoi(strport); | |
282 | } | |
283 | ||
284 | /* Returns remote/local port number for the current connection. */ | |
285 | ||
286 | int | |
287 | get_port(int local) | |
288 | { | |
289 | /* | |
290 | * If the connection is not a socket, return 65535. This is | |
291 | * intentionally chosen to be an unprivileged port number. | |
292 | */ | |
293 | if (!packet_connection_is_on_socket()) | |
294 | return 65535; | |
295 | ||
296 | /* Get socket and return the port number. */ | |
297 | return get_sock_port(packet_get_connection_in(), local); | |
298 | } | |
299 | ||
300 | int | |
301 | get_peer_port(int sock) | |
302 | { | |
303 | return get_sock_port(sock, 0); | |
304 | } | |
305 | ||
306 | int | |
307 | get_remote_port() | |
308 | { | |
309 | return get_port(0); | |
310 | } | |
311 | ||
312 | int | |
313 | get_local_port() | |
314 | { | |
315 | return get_port(1); | |
316 | } |