1 /* $NetBSD: canohost.c,v 1.4 2010/11/21 18:29:48 adam Exp $ */ 2 /* $OpenBSD: canohost.c,v 1.66 2010/01/13 01:20:20 dtucker Exp $ */ 3 /* 4 * Author: Tatu Ylonen <ylo@cs.hut.fi> 5 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 6 * All rights reserved 7 * Functions for returning the canonical host name of the remote site. 8 * 9 * As far as I am concerned, the code I have written for this software 10 * can be used freely for any purpose. Any derived versions of this 11 * software must be clearly marked as such, and if the derived work is 12 * incompatible with the protocol description in the RFC file, it must be 13 * called by a name other than "ssh" or "Secure Shell". 14 */ 15 16 #include "includes.h" 17 __RCSID("$NetBSD: canohost.c,v 1.4 2010/11/21 18:29:48 adam Exp $"); 18 #include <sys/types.h> 19 #include <sys/socket.h> 20 21 #include <netinet/in.h> 22 23 #include <ctype.h> 24 #include <errno.h> 25 #include <netdb.h> 26 #include <stdio.h> 27 #include <stdlib.h> 28 #include <string.h> 29 #include <stdarg.h> 30 #include <time.h> 31 #include <unistd.h> 32 33 #include "xmalloc.h" 34 #include "packet.h" 35 #include "log.h" 36 #include "canohost.h" 37 #include "misc.h" 38 39 static void check_ip_options(int, char *); 40 static char *canonical_host_ip = NULL; 41 static int cached_port = -1; 42 43 /* 44 * Return the canonical name of the host at the other end of the socket. The 45 * caller should free the returned string with xfree. 46 */ 47 48 static char * 49 get_remote_hostname(int sock, int use_dns) 50 { 51 struct sockaddr_storage from; 52 int i; 53 socklen_t fromlen; 54 struct addrinfo hints, *ai, *aitop; 55 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST]; 56 57 /* Get IP address of client. */ 58 fromlen = sizeof(from); 59 memset(&from, 0, sizeof(from)); 60 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { 61 debug("getpeername failed: %.100s", strerror(errno)); 62 cleanup_exit(255); 63 } 64 65 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop), 66 NULL, 0, NI_NUMERICHOST) != 0) 67 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed"); 68 69 if (from.ss_family == AF_INET) 70 check_ip_options(sock, ntop); 71 72 if (!use_dns) 73 return xstrdup(ntop); 74 75 debug3("Trying to reverse map address %.100s.", ntop); 76 /* Map the IP address to a host name. */ 77 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 78 NULL, 0, NI_NAMEREQD) != 0) { 79 /* Host name not found. Use ip address. */ 80 return xstrdup(ntop); 81 } 82 83 /* 84 * if reverse lookup result looks like a numeric hostname, 85 * someone is trying to trick us by PTR record like following: 86 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 87 */ 88 memset(&hints, 0, sizeof(hints)); 89 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 90 hints.ai_flags = AI_NUMERICHOST; 91 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 92 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 93 name, ntop); 94 freeaddrinfo(ai); 95 return xstrdup(ntop); 96 } 97 98 /* 99 * Convert it to all lowercase (which is expected by the rest 100 * of this software). 101 */ 102 for (i = 0; name[i]; i++) 103 if (isupper((unsigned char)name[i])) 104 name[i] = (char)tolower((unsigned char)name[i]); 105 /* 106 * Map it back to an IP address and check that the given 107 * address actually is an address of this host. This is 108 * necessary because anyone with access to a name server can 109 * define arbitrary names for an IP address. Mapping from 110 * name to IP address can be trusted better (but can still be 111 * fooled if the intruder has access to the name server of 112 * the domain). 113 */ 114 memset(&hints, 0, sizeof(hints)); 115 hints.ai_family = from.ss_family; 116 hints.ai_socktype = SOCK_STREAM; 117 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 118 logit("reverse mapping checking getaddrinfo for %.700s " 119 "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop); 120 return xstrdup(ntop); 121 } 122 /* Look for the address from the list of addresses. */ 123 for (ai = aitop; ai; ai = ai->ai_next) { 124 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 125 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 126 (strcmp(ntop, ntop2) == 0)) 127 break; 128 } 129 freeaddrinfo(aitop); 130 /* If we reached the end of the list, the address was not there. */ 131 if (!ai) { 132 /* Address not found for the host name. */ 133 logit("Address %.100s maps to %.600s, but this does not " 134 "map back to the address - POSSIBLE BREAK-IN ATTEMPT!", 135 ntop, name); 136 return xstrdup(ntop); 137 } 138 return xstrdup(name); 139 } 140 141 /* 142 * If IP options are supported, make sure there are none (log and 143 * disconnect them if any are found). Basically we are worried about 144 * source routing; it can be used to pretend you are somebody 145 * (ip-address) you are not. That itself may be "almost acceptable" 146 * under certain circumstances, but rhosts autentication is useless 147 * if source routing is accepted. Notice also that if we just dropped 148 * source routing here, the other side could use IP spoofing to do 149 * rest of the interaction and could still bypass security. So we 150 * exit here if we detect any IP options. 151 */ 152 /* IPv4 only */ 153 static void 154 check_ip_options(int sock, char *ipaddr) 155 { 156 u_char options[200]; 157 char text[sizeof(options) * 3 + 1]; 158 socklen_t option_size; 159 u_int i; 160 int ipproto; 161 struct protoent *ip; 162 163 if ((ip = getprotobyname("ip")) != NULL) 164 ipproto = ip->p_proto; 165 else 166 ipproto = IPPROTO_IP; 167 option_size = sizeof(options); 168 if (getsockopt(sock, ipproto, IP_OPTIONS, options, 169 &option_size) >= 0 && option_size != 0) { 170 text[0] = '\0'; 171 for (i = 0; i < option_size; i++) 172 snprintf(text + i*3, sizeof(text) - i*3, 173 " %2.2x", options[i]); 174 fatal("Connection from %.100s with IP options:%.800s", 175 ipaddr, text); 176 } 177 } 178 179 /* 180 * Return the canonical name of the host in the other side of the current 181 * connection. The host name is cached, so it is efficient to call this 182 * several times. 183 */ 184 185 const char * 186 get_canonical_hostname(int use_dns) 187 { 188 char *host; 189 static char *canonical_host_name = NULL; 190 static char *remote_ip = NULL; 191 192 /* Check if we have previously retrieved name with same option. */ 193 if (use_dns && canonical_host_name != NULL) 194 return canonical_host_name; 195 if (!use_dns && remote_ip != NULL) 196 return remote_ip; 197 198 /* Get the real hostname if socket; otherwise return UNKNOWN. */ 199 if (packet_connection_is_on_socket()) 200 host = get_remote_hostname(packet_get_connection_in(), use_dns); 201 else 202 host = "UNKNOWN"; 203 204 if (use_dns) 205 canonical_host_name = host; 206 else 207 remote_ip = host; 208 return host; 209 } 210 211 /* 212 * Returns the local/remote IP-address/hostname of socket as a string. 213 * The returned string must be freed. 214 */ 215 static char * 216 get_socket_address(int sock, int remote, int flags) 217 { 218 struct sockaddr_storage addr; 219 socklen_t addrlen; 220 char ntop[NI_MAXHOST]; 221 int r; 222 223 /* Get IP address of client. */ 224 addrlen = sizeof(addr); 225 memset(&addr, 0, sizeof(addr)); 226 227 if (remote) { 228 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen) 229 < 0) 230 return NULL; 231 } else { 232 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen) 233 < 0) 234 return NULL; 235 } 236 /* Get the address in ascii. */ 237 if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop, 238 sizeof(ntop), NULL, 0, flags)) != 0) { 239 error("get_socket_address: getnameinfo %d failed: %s", flags, 240 ssh_gai_strerror(r)); 241 return NULL; 242 } 243 return xstrdup(ntop); 244 } 245 246 char * 247 get_peer_ipaddr(int sock) 248 { 249 char *p; 250 251 if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL) 252 return p; 253 return xstrdup("UNKNOWN"); 254 } 255 256 char * 257 get_local_ipaddr(int sock) 258 { 259 char *p; 260 261 if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL) 262 return p; 263 return xstrdup("UNKNOWN"); 264 } 265 266 char * 267 get_local_name(int fd) 268 { 269 char *host, myname[NI_MAXHOST]; 270 271 /* Assume we were passed a socket */ 272 if ((host = get_socket_address(fd, 0, NI_NAMEREQD)) != NULL) 273 return host; 274 275 /* Handle the case where we were passed a pipe */ 276 if (gethostname(myname, sizeof(myname)) == -1) { 277 verbose("get_local_name: gethostname: %s", strerror(errno)); 278 } else { 279 host = xstrdup(myname); 280 } 281 282 return host; 283 } 284 285 void 286 clear_cached_addr(void) 287 { 288 if (canonical_host_ip != NULL) { 289 xfree(canonical_host_ip); 290 canonical_host_ip = NULL; 291 } 292 cached_port = -1; 293 } 294 295 /* 296 * Returns the IP-address of the remote host as a string. The returned 297 * string must not be freed. 298 */ 299 300 const char * 301 get_remote_ipaddr(void) 302 { 303 /* Check whether we have cached the ipaddr. */ 304 if (canonical_host_ip == NULL) { 305 if (packet_connection_is_on_socket()) { 306 canonical_host_ip = 307 get_peer_ipaddr(packet_get_connection_in()); 308 if (canonical_host_ip == NULL) 309 cleanup_exit(255); 310 } else { 311 /* If not on socket, return UNKNOWN. */ 312 canonical_host_ip = xstrdup("UNKNOWN"); 313 } 314 } 315 return canonical_host_ip; 316 } 317 318 const char * 319 get_remote_name_or_ip(u_int utmp_len, int use_dns) 320 { 321 static const char *remote = ""; 322 if (utmp_len > 0) 323 remote = get_canonical_hostname(use_dns); 324 if (utmp_len == 0 || strlen(remote) > utmp_len) 325 remote = get_remote_ipaddr(); 326 return remote; 327 } 328 329 /* Returns the local/remote port for the socket. */ 330 331 int 332 get_sock_port(int sock, int local) 333 { 334 struct sockaddr_storage from; 335 socklen_t fromlen; 336 char strport[NI_MAXSERV]; 337 int r; 338 339 /* Get IP address of client. */ 340 fromlen = sizeof(from); 341 memset(&from, 0, sizeof(from)); 342 if (local) { 343 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) { 344 error("getsockname failed: %.100s", strerror(errno)); 345 return 0; 346 } 347 } else { 348 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { 349 debug("getpeername failed: %.100s", strerror(errno)); 350 return -1; 351 } 352 } 353 /* Return port number. */ 354 if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0, 355 strport, sizeof(strport), NI_NUMERICSERV)) != 0) 356 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s", 357 ssh_gai_strerror(r)); 358 return atoi(strport); 359 } 360 361 /* Returns remote/local port number for the current connection. */ 362 363 static int 364 get_port(int local) 365 { 366 /* 367 * If the connection is not a socket, return 65535. This is 368 * intentionally chosen to be an unprivileged port number. 369 */ 370 if (!packet_connection_is_on_socket()) 371 return 65535; 372 373 /* Get socket and return the port number. */ 374 return get_sock_port(packet_get_connection_in(), local); 375 } 376 377 int 378 get_peer_port(int sock) 379 { 380 return get_sock_port(sock, 0); 381 } 382 383 int 384 get_remote_port(void) 385 { 386 /* Cache to avoid getpeername() on a dead connection */ 387 if (cached_port == -1) 388 cached_port = get_port(0); 389 390 return cached_port; 391 } 392 393 int 394 get_local_port(void) 395 { 396 return get_port(1); 397 } 398