1 /* $OpenBSD: canohost.c,v 1.65 2009/05/27 06:31:25 andreas Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * Functions for returning the canonical host name of the remote site. 7 * 8 * As far as I am concerned, the code I have written for this software 9 * can be used freely for any purpose. Any derived versions of this 10 * software must be clearly marked as such, and if the derived work is 11 * incompatible with the protocol description in the RFC file, it must be 12 * called by a name other than "ssh" or "Secure Shell". 13 */ 14 15 #include <sys/types.h> 16 #include <sys/socket.h> 17 18 #include <netinet/in.h> 19 20 #include <ctype.h> 21 #include <errno.h> 22 #include <netdb.h> 23 #include <stdio.h> 24 #include <stdlib.h> 25 #include <string.h> 26 #include <stdarg.h> 27 28 #include "xmalloc.h" 29 #include "packet.h" 30 #include "log.h" 31 #include "canohost.h" 32 #include "misc.h" 33 34 static void check_ip_options(int, char *); 35 static char *canonical_host_ip = NULL; 36 static int cached_port = -1; 37 38 /* 39 * Return the canonical name of the host at the other end of the socket. The 40 * caller should free the returned string with xfree. 41 */ 42 43 static char * 44 get_remote_hostname(int sock, int use_dns) 45 { 46 struct sockaddr_storage from; 47 int i; 48 socklen_t fromlen; 49 struct addrinfo hints, *ai, *aitop; 50 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST]; 51 52 /* Get IP address of client. */ 53 fromlen = sizeof(from); 54 memset(&from, 0, sizeof(from)); 55 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { 56 debug("getpeername failed: %.100s", strerror(errno)); 57 cleanup_exit(255); 58 } 59 60 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop), 61 NULL, 0, NI_NUMERICHOST) != 0) 62 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed"); 63 64 if (from.ss_family == AF_INET) 65 check_ip_options(sock, ntop); 66 67 if (!use_dns) 68 return xstrdup(ntop); 69 70 debug3("Trying to reverse map address %.100s.", ntop); 71 /* Map the IP address to a host name. */ 72 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 73 NULL, 0, NI_NAMEREQD) != 0) { 74 /* Host name not found. Use ip address. */ 75 return xstrdup(ntop); 76 } 77 78 /* 79 * if reverse lookup result looks like a numeric hostname, 80 * someone is trying to trick us by PTR record like following: 81 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 82 */ 83 memset(&hints, 0, sizeof(hints)); 84 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 85 hints.ai_flags = AI_NUMERICHOST; 86 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 87 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 88 name, ntop); 89 freeaddrinfo(ai); 90 return xstrdup(ntop); 91 } 92 93 /* 94 * Convert it to all lowercase (which is expected by the rest 95 * of this software). 96 */ 97 for (i = 0; name[i]; i++) 98 if (isupper(name[i])) 99 name[i] = (char)tolower(name[i]); 100 /* 101 * Map it back to an IP address and check that the given 102 * address actually is an address of this host. This is 103 * necessary because anyone with access to a name server can 104 * define arbitrary names for an IP address. Mapping from 105 * name to IP address can be trusted better (but can still be 106 * fooled if the intruder has access to the name server of 107 * the domain). 108 */ 109 memset(&hints, 0, sizeof(hints)); 110 hints.ai_family = from.ss_family; 111 hints.ai_socktype = SOCK_STREAM; 112 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 113 logit("reverse mapping checking getaddrinfo for %.700s " 114 "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop); 115 return xstrdup(ntop); 116 } 117 /* Look for the address from the list of addresses. */ 118 for (ai = aitop; ai; ai = ai->ai_next) { 119 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 120 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 121 (strcmp(ntop, ntop2) == 0)) 122 break; 123 } 124 freeaddrinfo(aitop); 125 /* If we reached the end of the list, the address was not there. */ 126 if (!ai) { 127 /* Address not found for the host name. */ 128 logit("Address %.100s maps to %.600s, but this does not " 129 "map back to the address - POSSIBLE BREAK-IN ATTEMPT!", 130 ntop, name); 131 return xstrdup(ntop); 132 } 133 return xstrdup(name); 134 } 135 136 /* 137 * If IP options are supported, make sure there are none (log and 138 * disconnect them if any are found). Basically we are worried about 139 * source routing; it can be used to pretend you are somebody 140 * (ip-address) you are not. That itself may be "almost acceptable" 141 * under certain circumstances, but rhosts autentication is useless 142 * if source routing is accepted. Notice also that if we just dropped 143 * source routing here, the other side could use IP spoofing to do 144 * rest of the interaction and could still bypass security. So we 145 * exit here if we detect any IP options. 146 */ 147 /* IPv4 only */ 148 static void 149 check_ip_options(int sock, char *ipaddr) 150 { 151 u_char options[200]; 152 char text[sizeof(options) * 3 + 1]; 153 socklen_t option_size; 154 u_int i; 155 int ipproto; 156 struct protoent *ip; 157 158 if ((ip = getprotobyname("ip")) != NULL) 159 ipproto = ip->p_proto; 160 else 161 ipproto = IPPROTO_IP; 162 option_size = sizeof(options); 163 if (getsockopt(sock, ipproto, IP_OPTIONS, options, 164 &option_size) >= 0 && option_size != 0) { 165 text[0] = '\0'; 166 for (i = 0; i < option_size; i++) 167 snprintf(text + i*3, sizeof(text) - i*3, 168 " %2.2x", options[i]); 169 fatal("Connection from %.100s with IP options:%.800s", 170 ipaddr, text); 171 } 172 } 173 174 /* 175 * Return the canonical name of the host in the other side of the current 176 * connection. The host name is cached, so it is efficient to call this 177 * several times. 178 */ 179 180 const char * 181 get_canonical_hostname(int use_dns) 182 { 183 char *host; 184 static char *canonical_host_name = NULL; 185 static char *remote_ip = NULL; 186 187 /* Check if we have previously retrieved name with same option. */ 188 if (use_dns && canonical_host_name != NULL) 189 return canonical_host_name; 190 if (!use_dns && remote_ip != NULL) 191 return remote_ip; 192 193 /* Get the real hostname if socket; otherwise return UNKNOWN. */ 194 if (packet_connection_is_on_socket()) 195 host = get_remote_hostname(packet_get_connection_in(), use_dns); 196 else 197 host = "UNKNOWN"; 198 199 if (use_dns) 200 canonical_host_name = host; 201 else 202 remote_ip = host; 203 return host; 204 } 205 206 /* 207 * Returns the local/remote IP-address/hostname of socket as a string. 208 * The returned string must be freed. 209 */ 210 static char * 211 get_socket_address(int sock, int remote, int flags) 212 { 213 struct sockaddr_storage addr; 214 socklen_t addrlen; 215 char ntop[NI_MAXHOST]; 216 int r; 217 218 /* Get IP address of client. */ 219 addrlen = sizeof(addr); 220 memset(&addr, 0, sizeof(addr)); 221 222 if (remote) { 223 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen) 224 < 0) 225 return NULL; 226 } else { 227 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen) 228 < 0) 229 return NULL; 230 } 231 /* Get the address in ascii. */ 232 if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop, 233 sizeof(ntop), NULL, 0, flags)) != 0) { 234 error("get_socket_address: getnameinfo %d failed: %s", flags, 235 ssh_gai_strerror(r)); 236 return NULL; 237 } 238 return xstrdup(ntop); 239 } 240 241 char * 242 get_peer_ipaddr(int sock) 243 { 244 char *p; 245 246 if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL) 247 return p; 248 return xstrdup("UNKNOWN"); 249 } 250 251 char * 252 get_local_ipaddr(int sock) 253 { 254 char *p; 255 256 if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL) 257 return p; 258 return xstrdup("UNKNOWN"); 259 } 260 261 char * 262 get_local_name(int sock) 263 { 264 return get_socket_address(sock, 0, NI_NAMEREQD); 265 } 266 267 void 268 clear_cached_addr(void) 269 { 270 if (canonical_host_ip != NULL) { 271 xfree(canonical_host_ip); 272 canonical_host_ip = NULL; 273 } 274 cached_port = -1; 275 } 276 277 /* 278 * Returns the IP-address of the remote host as a string. The returned 279 * string must not be freed. 280 */ 281 282 const char * 283 get_remote_ipaddr(void) 284 { 285 /* Check whether we have cached the ipaddr. */ 286 if (canonical_host_ip == NULL) { 287 if (packet_connection_is_on_socket()) { 288 canonical_host_ip = 289 get_peer_ipaddr(packet_get_connection_in()); 290 if (canonical_host_ip == NULL) 291 cleanup_exit(255); 292 } else { 293 /* If not on socket, return UNKNOWN. */ 294 canonical_host_ip = xstrdup("UNKNOWN"); 295 } 296 } 297 return canonical_host_ip; 298 } 299 300 const char * 301 get_remote_name_or_ip(u_int utmp_len, int use_dns) 302 { 303 static const char *remote = ""; 304 if (utmp_len > 0) 305 remote = get_canonical_hostname(use_dns); 306 if (utmp_len == 0 || strlen(remote) > utmp_len) 307 remote = get_remote_ipaddr(); 308 return remote; 309 } 310 311 /* Returns the local/remote port for the socket. */ 312 313 int 314 get_sock_port(int sock, int local) 315 { 316 struct sockaddr_storage from; 317 socklen_t fromlen; 318 char strport[NI_MAXSERV]; 319 int r; 320 321 /* Get IP address of client. */ 322 fromlen = sizeof(from); 323 memset(&from, 0, sizeof(from)); 324 if (local) { 325 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) { 326 error("getsockname failed: %.100s", strerror(errno)); 327 return 0; 328 } 329 } else { 330 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { 331 debug("getpeername failed: %.100s", strerror(errno)); 332 return -1; 333 } 334 } 335 /* Return port number. */ 336 if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0, 337 strport, sizeof(strport), NI_NUMERICSERV)) != 0) 338 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s", 339 ssh_gai_strerror(r)); 340 return atoi(strport); 341 } 342 343 /* Returns remote/local port number for the current connection. */ 344 345 static int 346 get_port(int local) 347 { 348 /* 349 * If the connection is not a socket, return 65535. This is 350 * intentionally chosen to be an unprivileged port number. 351 */ 352 if (!packet_connection_is_on_socket()) 353 return 65535; 354 355 /* Get socket and return the port number. */ 356 return get_sock_port(packet_get_connection_in(), local); 357 } 358 359 int 360 get_peer_port(int sock) 361 { 362 return get_sock_port(sock, 0); 363 } 364 365 int 366 get_remote_port(void) 367 { 368 /* Cache to avoid getpeername() on a dead connection */ 369 if (cached_port == -1) 370 cached_port = get_port(0); 371 372 return cached_port; 373 } 374 375 int 376 get_local_port(void) 377 { 378 return get_port(1); 379 } 380