1 /* $OpenBSD: canohost.c,v 1.71 2014/07/15 15:54:14 millert 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 #include <sys/un.h> 18 19 #include <netinet/in.h> 20 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 #include <unistd.h> 28 29 #include "xmalloc.h" 30 #include "packet.h" 31 #include "log.h" 32 #include "canohost.h" 33 #include "misc.h" 34 35 static void check_ip_options(int, char *); 36 static char *canonical_host_ip = NULL; 37 static int cached_port = -1; 38 39 /* 40 * Return the canonical name of the host at the other end of the socket. The 41 * caller should free the returned string. 42 */ 43 44 static char * 45 get_remote_hostname(int sock, int use_dns) 46 { 47 struct sockaddr_storage from; 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 /* Names are stores in lowercase. */ 94 lowercase(name); 95 96 /* 97 * Map it back to an IP address and check that the given 98 * address actually is an address of this host. This is 99 * necessary because anyone with access to a name server can 100 * define arbitrary names for an IP address. Mapping from 101 * name to IP address can be trusted better (but can still be 102 * fooled if the intruder has access to the name server of 103 * the domain). 104 */ 105 memset(&hints, 0, sizeof(hints)); 106 hints.ai_family = from.ss_family; 107 hints.ai_socktype = SOCK_STREAM; 108 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 109 logit("reverse mapping checking getaddrinfo for %.700s " 110 "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop); 111 return xstrdup(ntop); 112 } 113 /* Look for the address from the list of addresses. */ 114 for (ai = aitop; ai; ai = ai->ai_next) { 115 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 116 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 117 (strcmp(ntop, ntop2) == 0)) 118 break; 119 } 120 freeaddrinfo(aitop); 121 /* If we reached the end of the list, the address was not there. */ 122 if (!ai) { 123 /* Address not found for the host name. */ 124 logit("Address %.100s maps to %.600s, but this does not " 125 "map back to the address - POSSIBLE BREAK-IN ATTEMPT!", 126 ntop, name); 127 return xstrdup(ntop); 128 } 129 return xstrdup(name); 130 } 131 132 /* 133 * If IP options are supported, make sure there are none (log and 134 * disconnect them if any are found). Basically we are worried about 135 * source routing; it can be used to pretend you are somebody 136 * (ip-address) you are not. That itself may be "almost acceptable" 137 * under certain circumstances, but rhosts autentication is useless 138 * if source routing is accepted. Notice also that if we just dropped 139 * source routing here, the other side could use IP spoofing to do 140 * rest of the interaction and could still bypass security. So we 141 * exit here if we detect any IP options. 142 */ 143 /* IPv4 only */ 144 static void 145 check_ip_options(int sock, char *ipaddr) 146 { 147 u_char options[200]; 148 char text[sizeof(options) * 3 + 1]; 149 socklen_t option_size, i; 150 int ipproto; 151 struct protoent *ip; 152 153 if ((ip = getprotobyname("ip")) != NULL) 154 ipproto = ip->p_proto; 155 else 156 ipproto = IPPROTO_IP; 157 option_size = sizeof(options); 158 if (getsockopt(sock, ipproto, IP_OPTIONS, options, 159 &option_size) >= 0 && option_size != 0) { 160 text[0] = '\0'; 161 for (i = 0; i < option_size; i++) 162 snprintf(text + i*3, sizeof(text) - i*3, 163 " %2.2x", options[i]); 164 fatal("Connection from %.100s with IP options:%.800s", 165 ipaddr, text); 166 } 167 } 168 169 /* 170 * Return the canonical name of the host in the other side of the current 171 * connection. The host name is cached, so it is efficient to call this 172 * several times. 173 */ 174 175 const char * 176 get_canonical_hostname(int use_dns) 177 { 178 char *host; 179 static char *canonical_host_name = NULL; 180 static char *remote_ip = NULL; 181 182 /* Check if we have previously retrieved name with same option. */ 183 if (use_dns && canonical_host_name != NULL) 184 return canonical_host_name; 185 if (!use_dns && remote_ip != NULL) 186 return remote_ip; 187 188 /* Get the real hostname if socket; otherwise return UNKNOWN. */ 189 if (packet_connection_is_on_socket()) 190 host = get_remote_hostname(packet_get_connection_in(), use_dns); 191 else 192 host = "UNKNOWN"; 193 194 if (use_dns) 195 canonical_host_name = host; 196 else 197 remote_ip = host; 198 return host; 199 } 200 201 /* 202 * Returns the local/remote IP-address/hostname of socket as a string. 203 * The returned string must be freed. 204 */ 205 static char * 206 get_socket_address(int sock, int remote, int flags) 207 { 208 struct sockaddr_storage addr; 209 socklen_t addrlen; 210 char ntop[NI_MAXHOST]; 211 int r; 212 213 /* Get IP address of client. */ 214 addrlen = sizeof(addr); 215 memset(&addr, 0, sizeof(addr)); 216 217 if (remote) { 218 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen) 219 < 0) 220 return NULL; 221 } else { 222 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen) 223 < 0) 224 return NULL; 225 } 226 227 if (addr.ss_family == AF_UNIX) { 228 /* Get the Unix domain socket path. */ 229 return xstrdup(((struct sockaddr_un *)&addr)->sun_path); 230 } 231 232 /* Get the address in ascii. */ 233 if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop, 234 sizeof(ntop), NULL, 0, flags)) != 0) { 235 error("get_socket_address: getnameinfo %d failed: %s", flags, 236 ssh_gai_strerror(r)); 237 return NULL; 238 } 239 return xstrdup(ntop); 240 } 241 242 char * 243 get_peer_ipaddr(int sock) 244 { 245 char *p; 246 247 if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL) 248 return p; 249 return xstrdup("UNKNOWN"); 250 } 251 252 char * 253 get_local_ipaddr(int sock) 254 { 255 char *p; 256 257 if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL) 258 return p; 259 return xstrdup("UNKNOWN"); 260 } 261 262 char * 263 get_local_name(int fd) 264 { 265 char *host, myname[NI_MAXHOST]; 266 267 /* Assume we were passed a socket */ 268 if ((host = get_socket_address(fd, 0, NI_NAMEREQD)) != NULL) 269 return host; 270 271 /* Handle the case where we were passed a pipe */ 272 if (gethostname(myname, sizeof(myname)) == -1) { 273 verbose("get_local_name: gethostname: %s", strerror(errno)); 274 } else { 275 host = xstrdup(myname); 276 } 277 278 return host; 279 } 280 281 void 282 clear_cached_addr(void) 283 { 284 free(canonical_host_ip); 285 canonical_host_ip = NULL; 286 cached_port = -1; 287 } 288 289 /* 290 * Returns the IP-address of the remote host as a string. The returned 291 * string must not be freed. 292 */ 293 294 const char * 295 get_remote_ipaddr(void) 296 { 297 /* Check whether we have cached the ipaddr. */ 298 if (canonical_host_ip == NULL) { 299 if (packet_connection_is_on_socket()) { 300 canonical_host_ip = 301 get_peer_ipaddr(packet_get_connection_in()); 302 if (canonical_host_ip == NULL) 303 cleanup_exit(255); 304 } else { 305 /* If not on socket, return UNKNOWN. */ 306 canonical_host_ip = xstrdup("UNKNOWN"); 307 } 308 } 309 return canonical_host_ip; 310 } 311 312 const char * 313 get_remote_name_or_ip(u_int utmp_len, int use_dns) 314 { 315 static const char *remote = ""; 316 if (utmp_len > 0) 317 remote = get_canonical_hostname(use_dns); 318 if (utmp_len == 0 || strlen(remote) > utmp_len) 319 remote = get_remote_ipaddr(); 320 return remote; 321 } 322 323 /* Returns the local/remote port for the socket. */ 324 325 int 326 get_sock_port(int sock, int local) 327 { 328 struct sockaddr_storage from; 329 socklen_t fromlen; 330 char strport[NI_MAXSERV]; 331 int r; 332 333 /* Get IP address of client. */ 334 fromlen = sizeof(from); 335 memset(&from, 0, sizeof(from)); 336 if (local) { 337 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) { 338 error("getsockname failed: %.100s", strerror(errno)); 339 return 0; 340 } 341 } else { 342 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { 343 debug("getpeername failed: %.100s", strerror(errno)); 344 return -1; 345 } 346 } 347 348 /* Unix domain sockets don't have a port number. */ 349 if (from.ss_family == AF_UNIX) 350 return 0; 351 352 /* Return port number. */ 353 if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0, 354 strport, sizeof(strport), NI_NUMERICSERV)) != 0) 355 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s", 356 ssh_gai_strerror(r)); 357 return atoi(strport); 358 } 359 360 /* Returns remote/local port number for the current connection. */ 361 362 static int 363 get_port(int local) 364 { 365 /* 366 * If the connection is not a socket, return 65535. This is 367 * intentionally chosen to be an unprivileged port number. 368 */ 369 if (!packet_connection_is_on_socket()) 370 return 65535; 371 372 /* Get socket and return the port number. */ 373 return get_sock_port(packet_get_connection_in(), local); 374 } 375 376 int 377 get_peer_port(int sock) 378 { 379 return get_sock_port(sock, 0); 380 } 381 382 int 383 get_remote_port(void) 384 { 385 /* Cache to avoid getpeername() on a dead connection */ 386 if (cached_port == -1) 387 cached_port = get_port(0); 388 389 return cached_port; 390 } 391 392 int 393 get_local_port(void) 394 { 395 return get_port(1); 396 } 397