1 /* $OpenBSD: canohost.c,v 1.66 2010/01/13 01:20:20 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 <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 #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 with xfree. 42 */ 43 44 static char * 45 get_remote_hostname(int sock, int use_dns) 46 { 47 struct sockaddr_storage from; 48 int i; 49 socklen_t fromlen; 50 struct addrinfo hints, *ai, *aitop; 51 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST]; 52 53 /* Get IP address of client. */ 54 fromlen = sizeof(from); 55 memset(&from, 0, sizeof(from)); 56 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { 57 debug("getpeername failed: %.100s", strerror(errno)); 58 cleanup_exit(255); 59 } 60 61 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop), 62 NULL, 0, NI_NUMERICHOST) != 0) 63 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed"); 64 65 if (from.ss_family == AF_INET) 66 check_ip_options(sock, ntop); 67 68 if (!use_dns) 69 return xstrdup(ntop); 70 71 debug3("Trying to reverse map address %.100s.", ntop); 72 /* Map the IP address to a host name. */ 73 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 74 NULL, 0, NI_NAMEREQD) != 0) { 75 /* Host name not found. Use ip address. */ 76 return xstrdup(ntop); 77 } 78 79 /* 80 * if reverse lookup result looks like a numeric hostname, 81 * someone is trying to trick us by PTR record like following: 82 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 83 */ 84 memset(&hints, 0, sizeof(hints)); 85 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 86 hints.ai_flags = AI_NUMERICHOST; 87 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 88 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 89 name, ntop); 90 freeaddrinfo(ai); 91 return xstrdup(ntop); 92 } 93 94 /* 95 * Convert it to all lowercase (which is expected by the rest 96 * of this software). 97 */ 98 for (i = 0; name[i]; i++) 99 if (isupper(name[i])) 100 name[i] = (char)tolower(name[i]); 101 /* 102 * Map it back to an IP address and check that the given 103 * address actually is an address of this host. This is 104 * necessary because anyone with access to a name server can 105 * define arbitrary names for an IP address. Mapping from 106 * name to IP address can be trusted better (but can still be 107 * fooled if the intruder has access to the name server of 108 * the domain). 109 */ 110 memset(&hints, 0, sizeof(hints)); 111 hints.ai_family = from.ss_family; 112 hints.ai_socktype = SOCK_STREAM; 113 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 114 logit("reverse mapping checking getaddrinfo for %.700s " 115 "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop); 116 return xstrdup(ntop); 117 } 118 /* Look for the address from the list of addresses. */ 119 for (ai = aitop; ai; ai = ai->ai_next) { 120 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 121 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 122 (strcmp(ntop, ntop2) == 0)) 123 break; 124 } 125 freeaddrinfo(aitop); 126 /* If we reached the end of the list, the address was not there. */ 127 if (!ai) { 128 /* Address not found for the host name. */ 129 logit("Address %.100s maps to %.600s, but this does not " 130 "map back to the address - POSSIBLE BREAK-IN ATTEMPT!", 131 ntop, name); 132 return xstrdup(ntop); 133 } 134 return xstrdup(name); 135 } 136 137 /* 138 * If IP options are supported, make sure there are none (log and 139 * disconnect them if any are found). Basically we are worried about 140 * source routing; it can be used to pretend you are somebody 141 * (ip-address) you are not. That itself may be "almost acceptable" 142 * under certain circumstances, but rhosts autentication is useless 143 * if source routing is accepted. Notice also that if we just dropped 144 * source routing here, the other side could use IP spoofing to do 145 * rest of the interaction and could still bypass security. So we 146 * exit here if we detect any IP options. 147 */ 148 /* IPv4 only */ 149 static void 150 check_ip_options(int sock, char *ipaddr) 151 { 152 u_char options[200]; 153 char text[sizeof(options) * 3 + 1]; 154 socklen_t option_size; 155 u_int i; 156 int ipproto; 157 struct protoent *ip; 158 159 if ((ip = getprotobyname("ip")) != NULL) 160 ipproto = ip->p_proto; 161 else 162 ipproto = IPPROTO_IP; 163 option_size = sizeof(options); 164 if (getsockopt(sock, ipproto, IP_OPTIONS, options, 165 &option_size) >= 0 && option_size != 0) { 166 text[0] = '\0'; 167 for (i = 0; i < option_size; i++) 168 snprintf(text + i*3, sizeof(text) - i*3, 169 " %2.2x", options[i]); 170 fatal("Connection from %.100s with IP options:%.800s", 171 ipaddr, text); 172 } 173 } 174 175 /* 176 * Return the canonical name of the host in the other side of the current 177 * connection. The host name is cached, so it is efficient to call this 178 * several times. 179 */ 180 181 const char * 182 get_canonical_hostname(int use_dns) 183 { 184 char *host; 185 static char *canonical_host_name = NULL; 186 static char *remote_ip = NULL; 187 188 /* Check if we have previously retrieved name with same option. */ 189 if (use_dns && canonical_host_name != NULL) 190 return canonical_host_name; 191 if (!use_dns && remote_ip != NULL) 192 return remote_ip; 193 194 /* Get the real hostname if socket; otherwise return UNKNOWN. */ 195 if (packet_connection_is_on_socket()) 196 host = get_remote_hostname(packet_get_connection_in(), use_dns); 197 else 198 host = "UNKNOWN"; 199 200 if (use_dns) 201 canonical_host_name = host; 202 else 203 remote_ip = host; 204 return host; 205 } 206 207 /* 208 * Returns the local/remote IP-address/hostname of socket as a string. 209 * The returned string must be freed. 210 */ 211 static char * 212 get_socket_address(int sock, int remote, int flags) 213 { 214 struct sockaddr_storage addr; 215 socklen_t addrlen; 216 char ntop[NI_MAXHOST]; 217 int r; 218 219 /* Get IP address of client. */ 220 addrlen = sizeof(addr); 221 memset(&addr, 0, sizeof(addr)); 222 223 if (remote) { 224 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen) 225 < 0) 226 return NULL; 227 } else { 228 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen) 229 < 0) 230 return NULL; 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 if (canonical_host_ip != NULL) { 285 xfree(canonical_host_ip); 286 canonical_host_ip = NULL; 287 } 288 cached_port = -1; 289 } 290 291 /* 292 * Returns the IP-address of the remote host as a string. The returned 293 * string must not be freed. 294 */ 295 296 const char * 297 get_remote_ipaddr(void) 298 { 299 /* Check whether we have cached the ipaddr. */ 300 if (canonical_host_ip == NULL) { 301 if (packet_connection_is_on_socket()) { 302 canonical_host_ip = 303 get_peer_ipaddr(packet_get_connection_in()); 304 if (canonical_host_ip == NULL) 305 cleanup_exit(255); 306 } else { 307 /* If not on socket, return UNKNOWN. */ 308 canonical_host_ip = xstrdup("UNKNOWN"); 309 } 310 } 311 return canonical_host_ip; 312 } 313 314 const char * 315 get_remote_name_or_ip(u_int utmp_len, int use_dns) 316 { 317 static const char *remote = ""; 318 if (utmp_len > 0) 319 remote = get_canonical_hostname(use_dns); 320 if (utmp_len == 0 || strlen(remote) > utmp_len) 321 remote = get_remote_ipaddr(); 322 return remote; 323 } 324 325 /* Returns the local/remote port for the socket. */ 326 327 int 328 get_sock_port(int sock, int local) 329 { 330 struct sockaddr_storage from; 331 socklen_t fromlen; 332 char strport[NI_MAXSERV]; 333 int r; 334 335 /* Get IP address of client. */ 336 fromlen = sizeof(from); 337 memset(&from, 0, sizeof(from)); 338 if (local) { 339 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) { 340 error("getsockname failed: %.100s", strerror(errno)); 341 return 0; 342 } 343 } else { 344 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { 345 debug("getpeername failed: %.100s", strerror(errno)); 346 return -1; 347 } 348 } 349 /* Return port number. */ 350 if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0, 351 strport, sizeof(strport), NI_NUMERICSERV)) != 0) 352 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s", 353 ssh_gai_strerror(r)); 354 return atoi(strport); 355 } 356 357 /* Returns remote/local port number for the current connection. */ 358 359 static int 360 get_port(int local) 361 { 362 /* 363 * If the connection is not a socket, return 65535. This is 364 * intentionally chosen to be an unprivileged port number. 365 */ 366 if (!packet_connection_is_on_socket()) 367 return 65535; 368 369 /* Get socket and return the port number. */ 370 return get_sock_port(packet_get_connection_in(), local); 371 } 372 373 int 374 get_peer_port(int sock) 375 { 376 return get_sock_port(sock, 0); 377 } 378 379 int 380 get_remote_port(void) 381 { 382 /* Cache to avoid getpeername() on a dead connection */ 383 if (cached_port == -1) 384 cached_port = get_port(0); 385 386 return cached_port; 387 } 388 389 int 390 get_local_port(void) 391 { 392 return get_port(1); 393 } 394