1 /* $OpenBSD: canohost.c,v 1.70 2014/01/19 04:17:29 dtucker 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 "includes.h" 16 17 #include <sys/types.h> 18 #include <sys/socket.h> 19 20 #include <netinet/in.h> 21 #include <arpa/inet.h> 22 23 #include <errno.h> 24 #include <netdb.h> 25 #include <stdio.h> 26 #include <stdlib.h> 27 #include <string.h> 28 #include <stdarg.h> 29 #include <unistd.h> 30 31 #include "xmalloc.h" 32 #include "packet.h" 33 #include "log.h" 34 #include "canohost.h" 35 #include "misc.h" 36 37 static void check_ip_options(int, char *); 38 static char *canonical_host_ip = NULL; 39 static int cached_port = -1; 40 41 /* 42 * Return the canonical name of the host at the other end of the socket. The 43 * caller should free the returned string. 44 */ 45 46 static char * 47 get_remote_hostname(int sock, int use_dns) 48 { 49 struct sockaddr_storage from; 50 socklen_t fromlen; 51 struct addrinfo hints, *ai, *aitop; 52 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST]; 53 54 /* Get IP address of client. */ 55 fromlen = sizeof(from); 56 memset(&from, 0, sizeof(from)); 57 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { 58 debug("getpeername failed: %.100s", strerror(errno)); 59 cleanup_exit(255); 60 } 61 62 if (from.ss_family == AF_INET) 63 check_ip_options(sock, ntop); 64 65 ipv64_normalise_mapped(&from, &fromlen); 66 67 if (from.ss_family == AF_INET6) 68 fromlen = sizeof(struct sockaddr_in6); 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 if (!use_dns) 75 return xstrdup(ntop); 76 77 debug3("Trying to reverse map address %.100s.", ntop); 78 /* Map the IP address to a host name. */ 79 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 80 NULL, 0, NI_NAMEREQD) != 0) { 81 /* Host name not found. Use ip address. */ 82 return xstrdup(ntop); 83 } 84 85 /* 86 * if reverse lookup result looks like a numeric hostname, 87 * someone is trying to trick us by PTR record like following: 88 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 89 */ 90 memset(&hints, 0, sizeof(hints)); 91 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 92 hints.ai_flags = AI_NUMERICHOST; 93 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 94 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 95 name, ntop); 96 freeaddrinfo(ai); 97 return xstrdup(ntop); 98 } 99 100 /* Names are stores in lowercase. */ 101 lowercase(name); 102 103 /* 104 * Map it back to an IP address and check that the given 105 * address actually is an address of this host. This is 106 * necessary because anyone with access to a name server can 107 * define arbitrary names for an IP address. Mapping from 108 * name to IP address can be trusted better (but can still be 109 * fooled if the intruder has access to the name server of 110 * the domain). 111 */ 112 memset(&hints, 0, sizeof(hints)); 113 hints.ai_family = from.ss_family; 114 hints.ai_socktype = SOCK_STREAM; 115 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 116 logit("reverse mapping checking getaddrinfo for %.700s " 117 "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop); 118 return xstrdup(ntop); 119 } 120 /* Look for the address from the list of addresses. */ 121 for (ai = aitop; ai; ai = ai->ai_next) { 122 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 123 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 124 (strcmp(ntop, ntop2) == 0)) 125 break; 126 } 127 freeaddrinfo(aitop); 128 /* If we reached the end of the list, the address was not there. */ 129 if (!ai) { 130 /* Address not found for the host name. */ 131 logit("Address %.100s maps to %.600s, but this does not " 132 "map back to the address - POSSIBLE BREAK-IN ATTEMPT!", 133 ntop, name); 134 return xstrdup(ntop); 135 } 136 return xstrdup(name); 137 } 138 139 /* 140 * If IP options are supported, make sure there are none (log and 141 * disconnect them if any are found). Basically we are worried about 142 * source routing; it can be used to pretend you are somebody 143 * (ip-address) you are not. That itself may be "almost acceptable" 144 * under certain circumstances, but rhosts autentication is useless 145 * if source routing is accepted. Notice also that if we just dropped 146 * source routing here, the other side could use IP spoofing to do 147 * rest of the interaction and could still bypass security. So we 148 * exit here if we detect any IP options. 149 */ 150 /* IPv4 only */ 151 static void 152 check_ip_options(int sock, char *ipaddr) 153 { 154 #ifdef IP_OPTIONS 155 u_char options[200]; 156 char text[sizeof(options) * 3 + 1]; 157 socklen_t option_size, i; 158 int ipproto; 159 struct protoent *ip; 160 161 if ((ip = getprotobyname("ip")) != NULL) 162 ipproto = ip->p_proto; 163 else 164 ipproto = IPPROTO_IP; 165 option_size = sizeof(options); 166 if (getsockopt(sock, ipproto, IP_OPTIONS, options, 167 &option_size) >= 0 && option_size != 0) { 168 text[0] = '\0'; 169 for (i = 0; i < option_size; i++) 170 snprintf(text + i*3, sizeof(text) - i*3, 171 " %2.2x", options[i]); 172 fatal("Connection from %.100s with IP options:%.800s", 173 ipaddr, text); 174 } 175 #endif /* IP_OPTIONS */ 176 } 177 178 void 179 ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len) 180 { 181 struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr; 182 struct sockaddr_in *a4 = (struct sockaddr_in *)addr; 183 struct in_addr inaddr; 184 u_int16_t port; 185 186 if (addr->ss_family != AF_INET6 || 187 !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr)) 188 return; 189 190 debug3("Normalising mapped IPv4 in IPv6 address"); 191 192 memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr)); 193 port = a6->sin6_port; 194 195 memset(a4, 0, sizeof(*a4)); 196 197 a4->sin_family = AF_INET; 198 *len = sizeof(*a4); 199 memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr)); 200 a4->sin_port = port; 201 } 202 203 /* 204 * Return the canonical name of the host in the other side of the current 205 * connection. The host name is cached, so it is efficient to call this 206 * several times. 207 */ 208 209 const char * 210 get_canonical_hostname(int use_dns) 211 { 212 char *host; 213 static char *canonical_host_name = NULL; 214 static char *remote_ip = NULL; 215 216 /* Check if we have previously retrieved name with same option. */ 217 if (use_dns && canonical_host_name != NULL) 218 return canonical_host_name; 219 if (!use_dns && remote_ip != NULL) 220 return remote_ip; 221 222 /* Get the real hostname if socket; otherwise return UNKNOWN. */ 223 if (packet_connection_is_on_socket()) 224 host = get_remote_hostname(packet_get_connection_in(), use_dns); 225 else 226 host = "UNKNOWN"; 227 228 if (use_dns) 229 canonical_host_name = host; 230 else 231 remote_ip = host; 232 return host; 233 } 234 235 /* 236 * Returns the local/remote IP-address/hostname of socket as a string. 237 * The returned string must be freed. 238 */ 239 static char * 240 get_socket_address(int sock, int remote, int flags) 241 { 242 struct sockaddr_storage addr; 243 socklen_t addrlen; 244 char ntop[NI_MAXHOST]; 245 int r; 246 247 /* Get IP address of client. */ 248 addrlen = sizeof(addr); 249 memset(&addr, 0, sizeof(addr)); 250 251 if (remote) { 252 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen) 253 < 0) 254 return NULL; 255 } else { 256 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen) 257 < 0) 258 return NULL; 259 } 260 261 /* Work around Linux IPv6 weirdness */ 262 if (addr.ss_family == AF_INET6) 263 addrlen = sizeof(struct sockaddr_in6); 264 265 ipv64_normalise_mapped(&addr, &addrlen); 266 267 /* Get the address in ascii. */ 268 if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop, 269 sizeof(ntop), NULL, 0, flags)) != 0) { 270 error("get_socket_address: getnameinfo %d failed: %s", flags, 271 ssh_gai_strerror(r)); 272 return NULL; 273 } 274 return xstrdup(ntop); 275 } 276 277 char * 278 get_peer_ipaddr(int sock) 279 { 280 char *p; 281 282 if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL) 283 return p; 284 return xstrdup("UNKNOWN"); 285 } 286 287 char * 288 get_local_ipaddr(int sock) 289 { 290 char *p; 291 292 if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL) 293 return p; 294 return xstrdup("UNKNOWN"); 295 } 296 297 char * 298 get_local_name(int fd) 299 { 300 char *host, myname[NI_MAXHOST]; 301 302 /* Assume we were passed a socket */ 303 if ((host = get_socket_address(fd, 0, NI_NAMEREQD)) != NULL) 304 return host; 305 306 /* Handle the case where we were passed a pipe */ 307 if (gethostname(myname, sizeof(myname)) == -1) { 308 verbose("get_local_name: gethostname: %s", strerror(errno)); 309 } else { 310 host = xstrdup(myname); 311 } 312 313 return host; 314 } 315 316 void 317 clear_cached_addr(void) 318 { 319 free(canonical_host_ip); 320 canonical_host_ip = NULL; 321 cached_port = -1; 322 } 323 324 /* 325 * Returns the IP-address of the remote host as a string. The returned 326 * string must not be freed. 327 */ 328 329 const char * 330 get_remote_ipaddr(void) 331 { 332 /* Check whether we have cached the ipaddr. */ 333 if (canonical_host_ip == NULL) { 334 if (packet_connection_is_on_socket()) { 335 canonical_host_ip = 336 get_peer_ipaddr(packet_get_connection_in()); 337 if (canonical_host_ip == NULL) 338 cleanup_exit(255); 339 } else { 340 /* If not on socket, return UNKNOWN. */ 341 canonical_host_ip = xstrdup("UNKNOWN"); 342 } 343 } 344 return canonical_host_ip; 345 } 346 347 const char * 348 get_remote_name_or_ip(u_int utmp_len, int use_dns) 349 { 350 static const char *remote = ""; 351 if (utmp_len > 0) 352 remote = get_canonical_hostname(use_dns); 353 if (utmp_len == 0 || strlen(remote) > utmp_len) 354 remote = get_remote_ipaddr(); 355 return remote; 356 } 357 358 /* Returns the local/remote port for the socket. */ 359 360 int 361 get_sock_port(int sock, int local) 362 { 363 struct sockaddr_storage from; 364 socklen_t fromlen; 365 char strport[NI_MAXSERV]; 366 int r; 367 368 /* Get IP address of client. */ 369 fromlen = sizeof(from); 370 memset(&from, 0, sizeof(from)); 371 if (local) { 372 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) { 373 error("getsockname failed: %.100s", strerror(errno)); 374 return 0; 375 } 376 } else { 377 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { 378 debug("getpeername failed: %.100s", strerror(errno)); 379 return -1; 380 } 381 } 382 383 /* Work around Linux IPv6 weirdness */ 384 if (from.ss_family == AF_INET6) 385 fromlen = sizeof(struct sockaddr_in6); 386 387 /* Return port number. */ 388 if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0, 389 strport, sizeof(strport), NI_NUMERICSERV)) != 0) 390 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s", 391 ssh_gai_strerror(r)); 392 return atoi(strport); 393 } 394 395 /* Returns remote/local port number for the current connection. */ 396 397 static int 398 get_port(int local) 399 { 400 /* 401 * If the connection is not a socket, return 65535. This is 402 * intentionally chosen to be an unprivileged port number. 403 */ 404 if (!packet_connection_is_on_socket()) 405 return 65535; 406 407 /* Get socket and return the port number. */ 408 return get_sock_port(packet_get_connection_in(), local); 409 } 410 411 int 412 get_peer_port(int sock) 413 { 414 return get_sock_port(sock, 0); 415 } 416 417 int 418 get_remote_port(void) 419 { 420 /* Cache to avoid getpeername() on a dead connection */ 421 if (cached_port == -1) 422 cached_port = get_port(0); 423 424 return cached_port; 425 } 426 427 int 428 get_local_port(void) 429 { 430 return get_port(1); 431 } 432