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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 1.20 2001/02/03 10:08:37 markus Exp $"); | |
16 | ||
17 | #include "packet.h" | |
18 | #include "xmalloc.h" | |
19 | #include "log.h" | |
20 | ||
21 | void check_ip_options(int socket, char *ipaddr); | |
22 | ||
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 | */ | |
27 | ||
28 | char * | |
29 | get_remote_hostname(int socket, int reverse_mapping_check) | |
30 | { | |
31 | struct sockaddr_storage from; | |
32 | int i; | |
33 | socklen_t fromlen; | |
34 | struct addrinfo hints, *ai, *aitop; | |
35 | char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST]; | |
36 | ||
37 | /* Get IP address of client. */ | |
38 | fromlen = sizeof(from); | |
39 | memset(&from, 0, sizeof(from)); | |
40 | if (getpeername(socket, (struct sockaddr *) &from, &fromlen) < 0) { | |
41 | debug("getpeername failed: %.100s", strerror(errno)); | |
42 | fatal_cleanup(); | |
43 | } | |
44 | #ifdef IPV4_IN_IPV6 | |
45 | if (from.ss_family == AF_INET6) { | |
46 | struct sockaddr_in6 *from6 = (struct sockaddr_in6 *)&from; | |
47 | ||
48 | /* Detect IPv4 in IPv6 mapped address and convert it to */ | |
49 | /* plain (AF_INET) IPv4 address */ | |
50 | if (IN6_IS_ADDR_V4MAPPED(&from6->sin6_addr)) { | |
51 | struct sockaddr_in *from4 = (struct sockaddr_in *)&from; | |
52 | struct in_addr addr; | |
53 | u_int16_t port; | |
54 | ||
55 | memcpy(&addr, ((char *)&from6->sin6_addr) + 12, sizeof(addr)); | |
56 | port = from6->sin6_port; | |
57 | ||
58 | memset(&from, 0, sizeof(from)); | |
59 | ||
60 | from4->sin_family = AF_INET; | |
61 | memcpy(&from4->sin_addr, &addr, sizeof(addr)); | |
62 | from4->sin_port = port; | |
63 | } | |
64 | } | |
65 | #endif | |
66 | if (from.ss_family == AF_INET) | |
67 | check_ip_options(socket, ntop); | |
68 | ||
69 | if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop), | |
70 | NULL, 0, NI_NUMERICHOST) != 0) | |
71 | fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed"); | |
72 | ||
73 | /* Map the IP address to a host name. */ | |
74 | if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), | |
75 | NULL, 0, NI_NAMEREQD) != 0) { | |
76 | /* Host name not found. Use ip address. */ | |
77 | log("Could not reverse map address %.100s.", ntop); | |
78 | return xstrdup(ntop); | |
79 | } | |
80 | ||
81 | /* Got host name. */ | |
82 | name[sizeof(name) - 1] = '\0'; | |
83 | /* | |
84 | * Convert it to all lowercase (which is expected by the rest | |
85 | * of this software). | |
86 | */ | |
87 | for (i = 0; name[i]; i++) | |
88 | if (isupper(name[i])) | |
89 | name[i] = tolower(name[i]); | |
90 | ||
91 | if (!reverse_mapping_check) | |
92 | return xstrdup(name); | |
93 | /* | |
94 | * Map it back to an IP address and check that the given | |
95 | * address actually is an address of this host. This is | |
96 | * necessary because anyone with access to a name server can | |
97 | * define arbitrary names for an IP address. Mapping from | |
98 | * name to IP address can be trusted better (but can still be | |
99 | * fooled if the intruder has access to the name server of | |
100 | * the domain). | |
101 | */ | |
102 | memset(&hints, 0, sizeof(hints)); | |
103 | hints.ai_family = from.ss_family; | |
104 | hints.ai_socktype = SOCK_STREAM; | |
105 | if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { | |
106 | log("reverse mapping checking getaddrinfo for %.700s " | |
107 | "failed - POSSIBLE BREAKIN ATTEMPT!", name); | |
108 | return xstrdup(ntop); | |
109 | } | |
110 | /* Look for the address from the list of addresses. */ | |
111 | for (ai = aitop; ai; ai = ai->ai_next) { | |
112 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, | |
113 | sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && | |
114 | (strcmp(ntop, ntop2) == 0)) | |
115 | break; | |
116 | } | |
117 | freeaddrinfo(aitop); | |
118 | /* If we reached the end of the list, the address was not there. */ | |
119 | if (!ai) { | |
120 | /* Address not found for the host name. */ | |
121 | log("Address %.100s maps to %.600s, but this does not " | |
122 | "map back to the address - POSSIBLE BREAKIN ATTEMPT!", | |
123 | ntop, name); | |
124 | return xstrdup(ntop); | |
125 | } | |
126 | return xstrdup(name); | |
127 | } | |
128 | ||
129 | /* | |
130 | * If IP options are supported, make sure there are none (log and | |
131 | * disconnect them if any are found). Basically we are worried about | |
132 | * source routing; it can be used to pretend you are somebody | |
133 | * (ip-address) you are not. That itself may be "almost acceptable" | |
134 | * under certain circumstances, but rhosts autentication is useless | |
135 | * if source routing is accepted. Notice also that if we just dropped | |
136 | * source routing here, the other side could use IP spoofing to do | |
137 | * rest of the interaction and could still bypass security. So we | |
138 | * exit here if we detect any IP options. | |
139 | */ | |
140 | /* IPv4 only */ | |
141 | void | |
142 | check_ip_options(int socket, char *ipaddr) | |
143 | { | |
144 | u_char options[200], *ucp; | |
145 | char text[1024], *cp; | |
146 | socklen_t option_size; | |
147 | int ipproto; | |
148 | struct protoent *ip; | |
149 | ||
150 | if ((ip = getprotobyname("ip")) != NULL) | |
151 | ipproto = ip->p_proto; | |
152 | else | |
153 | ipproto = IPPROTO_IP; | |
154 | option_size = sizeof(options); | |
155 | if (getsockopt(socket, ipproto, IP_OPTIONS, (void *)options, | |
156 | &option_size) >= 0 && option_size != 0) { | |
157 | cp = text; | |
158 | /* Note: "text" buffer must be at least 3x as big as options. */ | |
159 | for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3) | |
160 | sprintf(cp, " %2.2x", *ucp); | |
161 | log("Connection from %.100s with IP options:%.800s", | |
162 | ipaddr, text); | |
163 | packet_disconnect("Connection from %.100s with IP options:%.800s", | |
164 | ipaddr, text); | |
165 | } | |
166 | } | |
167 | ||
168 | /* | |
169 | * Return the canonical name of the host in the other side of the current | |
170 | * connection. The host name is cached, so it is efficient to call this | |
171 | * several times. | |
172 | */ | |
173 | ||
174 | const char * | |
175 | get_canonical_hostname(int reverse_mapping_check) | |
176 | { | |
177 | static char *canonical_host_name = NULL; | |
178 | static int reverse_mapping_checked = 0; | |
179 | ||
180 | /* Check if we have previously retrieved name with same option. */ | |
181 | if (canonical_host_name != NULL) { | |
182 | if (reverse_mapping_checked != reverse_mapping_check) | |
183 | xfree(canonical_host_name); | |
184 | else | |
185 | return canonical_host_name; | |
186 | } | |
187 | ||
188 | /* Get the real hostname if socket; otherwise return UNKNOWN. */ | |
189 | if (packet_connection_is_on_socket()) | |
190 | canonical_host_name = get_remote_hostname( | |
191 | packet_get_connection_in(), reverse_mapping_check); | |
192 | else | |
193 | canonical_host_name = xstrdup("UNKNOWN"); | |
194 | ||
195 | reverse_mapping_checked = reverse_mapping_check; | |
196 | return canonical_host_name; | |
197 | } | |
198 | ||
199 | /* | |
200 | * Returns the remote IP-address of socket as a string. The returned | |
201 | * string must be freed. | |
202 | */ | |
203 | ||
204 | char * | |
205 | get_peer_ipaddr(int socket) | |
206 | { | |
207 | struct sockaddr_storage from; | |
208 | socklen_t fromlen; | |
209 | char ntop[NI_MAXHOST]; | |
210 | ||
211 | /* Get IP address of client. */ | |
212 | fromlen = sizeof(from); | |
213 | memset(&from, 0, sizeof(from)); | |
214 | if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) { | |
215 | debug("get_peer_ipaddr: getpeername failed: %.100s", strerror(errno)); | |
216 | return NULL; | |
217 | } | |
218 | /* Get the IP address in ascii. */ | |
219 | if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop), | |
220 | NULL, 0, NI_NUMERICHOST) != 0) { | |
221 | error("get_peer_ipaddr: getnameinfo NI_NUMERICHOST failed"); | |
222 | return NULL; | |
223 | } | |
224 | return xstrdup(ntop); | |
225 | } | |
226 | ||
227 | /* | |
228 | * Returns the IP-address of the remote host as a string. The returned | |
229 | * string must not be freed. | |
230 | */ | |
231 | ||
232 | const char * | |
233 | get_remote_ipaddr() | |
234 | { | |
235 | static char *canonical_host_ip = NULL; | |
236 | ||
237 | /* Check whether we have cached the ipaddr. */ | |
238 | if (canonical_host_ip == NULL) { | |
239 | if (packet_connection_is_on_socket()) { | |
240 | canonical_host_ip = | |
241 | get_peer_ipaddr(packet_get_connection_in()); | |
242 | if (canonical_host_ip == NULL) | |
243 | fatal_cleanup(); | |
244 | } else { | |
245 | /* If not on socket, return UNKNOWN. */ | |
246 | canonical_host_ip = xstrdup("UNKNOWN"); | |
247 | } | |
248 | } | |
249 | return canonical_host_ip; | |
250 | } | |
251 | ||
252 | /* Returns the local/remote port for the socket. */ | |
253 | ||
254 | int | |
255 | get_sock_port(int sock, int local) | |
256 | { | |
257 | struct sockaddr_storage from; | |
258 | socklen_t fromlen; | |
259 | char strport[NI_MAXSERV]; | |
260 | ||
261 | /* Get IP address of client. */ | |
262 | fromlen = sizeof(from); | |
263 | memset(&from, 0, sizeof(from)); | |
264 | if (local) { | |
265 | if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) { | |
266 | error("getsockname failed: %.100s", strerror(errno)); | |
267 | return 0; | |
268 | } | |
269 | } else { | |
270 | if (getpeername(sock, (struct sockaddr *) & from, &fromlen) < 0) { | |
271 | debug("getpeername failed: %.100s", strerror(errno)); | |
272 | fatal_cleanup(); | |
273 | } | |
274 | } | |
275 | /* Return port number. */ | |
276 | if (getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0, | |
277 | strport, sizeof(strport), NI_NUMERICSERV) != 0) | |
278 | fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed"); | |
279 | return atoi(strport); | |
280 | } | |
281 | ||
282 | /* Returns remote/local port number for the current connection. */ | |
283 | ||
284 | int | |
285 | get_port(int local) | |
286 | { | |
287 | /* | |
288 | * If the connection is not a socket, return 65535. This is | |
289 | * intentionally chosen to be an unprivileged port number. | |
290 | */ | |
291 | if (!packet_connection_is_on_socket()) | |
292 | return 65535; | |
293 | ||
294 | /* Get socket and return the port number. */ | |
295 | return get_sock_port(packet_get_connection_in(), local); | |
296 | } | |
297 | ||
298 | int | |
299 | get_peer_port(int sock) | |
300 | { | |
301 | return get_sock_port(sock, 0); | |
302 | } | |
303 | ||
304 | int | |
305 | get_remote_port() | |
306 | { | |
307 | return get_port(0); | |
308 | } | |
309 | ||
310 | int | |
311 | get_local_port() | |
312 | { | |
313 | return get_port(1); | |
314 | } |