1 /* 2 * Author: Tatu Ylonen <ylo@cs.hut.fi> 3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 4 * All rights reserved 5 * Functions for returning the canonical host name of the remote site. 6 * 7 * As far as I am concerned, the code I have written for this software 8 * can be used freely for any purpose. Any derived versions of this 9 * software must be clearly marked as such, and if the derived work is 10 * incompatible with the protocol description in the RFC file, it must be 11 * called by a name other than "ssh" or "Secure Shell". 12 */ 13 14 #include "includes.h" 15 RCSID("$OpenBSD: canohost.c,v 1.35 2002/11/26 02:38:54 stevesk Exp $"); 16 17 #include "packet.h" 18 #include "xmalloc.h" 19 #include "log.h" 20 #include "canohost.h" 21 22 static void check_ip_options(int, char *); 23 24 /* 25 * Return the canonical name of the host at the other end of the socket. The 26 * caller should free the returned string with xfree. 27 */ 28 29 static char * 30 get_remote_hostname(int socket, int verify_reverse_mapping) 31 { 32 struct sockaddr_storage from; 33 int i; 34 socklen_t fromlen; 35 struct addrinfo hints, *ai, *aitop; 36 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST]; 37 38 /* Get IP address of client. */ 39 fromlen = sizeof(from); 40 memset(&from, 0, sizeof(from)); 41 if (getpeername(socket, (struct sockaddr *)&from, &fromlen) < 0) { 42 debug("getpeername failed: %.100s", strerror(errno)); 43 fatal_cleanup(); 44 } 45 #ifdef IPV4_IN_IPV6 46 if (from.ss_family == AF_INET6) { 47 struct sockaddr_in6 *from6 = (struct sockaddr_in6 *)&from; 48 49 /* Detect IPv4 in IPv6 mapped address and convert it to */ 50 /* plain (AF_INET) IPv4 address */ 51 if (IN6_IS_ADDR_V4MAPPED(&from6->sin6_addr)) { 52 struct sockaddr_in *from4 = (struct sockaddr_in *)&from; 53 struct in_addr addr; 54 u_int16_t port; 55 56 memcpy(&addr, ((char *)&from6->sin6_addr) + 12, sizeof(addr)); 57 port = from6->sin6_port; 58 59 memset(&from, 0, sizeof(from)); 60 61 from4->sin_family = AF_INET; 62 fromlen = sizeof(*from4); 63 memcpy(&from4->sin_addr, &addr, sizeof(addr)); 64 from4->sin_port = port; 65 } 66 } 67 #endif 68 if (from.ss_family == AF_INET6) 69 fromlen = sizeof(struct sockaddr_in6); 70 71 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop), 72 NULL, 0, NI_NUMERICHOST) != 0) 73 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed"); 74 75 if (from.ss_family == AF_INET) 76 check_ip_options(socket, ntop); 77 78 debug3("Trying to reverse map address %.100s.", ntop); 79 /* Map the IP address to a host name. */ 80 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 81 NULL, 0, NI_NAMEREQD) != 0) { 82 /* Host name not found. Use ip address. */ 83 #if 0 84 log("Could not reverse map address %.100s.", ntop); 85 #endif 86 return xstrdup(ntop); 87 } 88 89 /* Got host name. */ 90 name[sizeof(name) - 1] = '\0'; 91 /* 92 * Convert it to all lowercase (which is expected by the rest 93 * of this software). 94 */ 95 for (i = 0; name[i]; i++) 96 if (isupper(name[i])) 97 name[i] = tolower(name[i]); 98 99 if (!verify_reverse_mapping) 100 return xstrdup(name); 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 log("reverse mapping checking getaddrinfo for %.700s " 115 "failed - POSSIBLE BREAKIN ATTEMPT!", name); 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 log("Address %.100s maps to %.600s, but this does not " 130 "map back to the address - POSSIBLE BREAKIN 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 socket, char *ipaddr) 151 { 152 u_char options[200]; 153 char text[sizeof(options) * 3 + 1]; 154 socklen_t option_size; 155 int i, 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(socket, 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 log("Connection from %.100s with IP options:%.800s", 170 ipaddr, text); 171 packet_disconnect("Connection from %.100s with IP options:%.800s", 172 ipaddr, text); 173 } 174 } 175 176 /* 177 * Return the canonical name of the host in the other side of the current 178 * connection. The host name is cached, so it is efficient to call this 179 * several times. 180 */ 181 182 const char * 183 get_canonical_hostname(int verify_reverse_mapping) 184 { 185 static char *canonical_host_name = NULL; 186 static int verify_reverse_mapping_done = 0; 187 188 /* Check if we have previously retrieved name with same option. */ 189 if (canonical_host_name != NULL) { 190 if (verify_reverse_mapping_done != verify_reverse_mapping) 191 xfree(canonical_host_name); 192 else 193 return canonical_host_name; 194 } 195 196 /* Get the real hostname if socket; otherwise return UNKNOWN. */ 197 if (packet_connection_is_on_socket()) 198 canonical_host_name = get_remote_hostname( 199 packet_get_connection_in(), verify_reverse_mapping); 200 else 201 canonical_host_name = xstrdup("UNKNOWN"); 202 203 verify_reverse_mapping_done = verify_reverse_mapping; 204 return canonical_host_name; 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 socket, int remote, int flags) 213 { 214 struct sockaddr_storage addr; 215 socklen_t addrlen; 216 char ntop[NI_MAXHOST]; 217 218 /* Get IP address of client. */ 219 addrlen = sizeof(addr); 220 memset(&addr, 0, sizeof(addr)); 221 222 if (remote) { 223 if (getpeername(socket, (struct sockaddr *)&addr, &addrlen) 224 < 0) 225 return NULL; 226 } else { 227 if (getsockname(socket, (struct sockaddr *)&addr, &addrlen) 228 < 0) 229 return NULL; 230 } 231 232 /* Work around Linux IPv6 weirdness */ 233 if (addr.ss_family == AF_INET6) 234 addrlen = sizeof(struct sockaddr_in6); 235 236 /* Get the address in ascii. */ 237 if (getnameinfo((struct sockaddr *)&addr, addrlen, ntop, sizeof(ntop), 238 NULL, 0, flags) != 0) { 239 error("get_socket_address: getnameinfo %d failed", flags); 240 return NULL; 241 } 242 return xstrdup(ntop); 243 } 244 245 char * 246 get_peer_ipaddr(int socket) 247 { 248 char *p; 249 250 if ((p = get_socket_address(socket, 1, NI_NUMERICHOST)) != NULL) 251 return p; 252 return xstrdup("UNKNOWN"); 253 } 254 255 char * 256 get_local_ipaddr(int socket) 257 { 258 char *p; 259 260 if ((p = get_socket_address(socket, 0, NI_NUMERICHOST)) != NULL) 261 return p; 262 return xstrdup("UNKNOWN"); 263 } 264 265 char * 266 get_local_name(int socket) 267 { 268 return get_socket_address(socket, 0, NI_NAMEREQD); 269 } 270 271 /* 272 * Returns the IP-address of the remote host as a string. The returned 273 * string must not be freed. 274 */ 275 276 const char * 277 get_remote_ipaddr(void) 278 { 279 static char *canonical_host_ip = NULL; 280 281 /* Check whether we have cached the ipaddr. */ 282 if (canonical_host_ip == NULL) { 283 if (packet_connection_is_on_socket()) { 284 canonical_host_ip = 285 get_peer_ipaddr(packet_get_connection_in()); 286 if (canonical_host_ip == NULL) 287 fatal_cleanup(); 288 } else { 289 /* If not on socket, return UNKNOWN. */ 290 canonical_host_ip = xstrdup("UNKNOWN"); 291 } 292 } 293 return canonical_host_ip; 294 } 295 296 const char * 297 get_remote_name_or_ip(u_int utmp_len, int verify_reverse_mapping) 298 { 299 static const char *remote = ""; 300 if (utmp_len > 0) 301 remote = get_canonical_hostname(verify_reverse_mapping); 302 if (utmp_len == 0 || strlen(remote) > utmp_len) 303 remote = get_remote_ipaddr(); 304 return remote; 305 } 306 307 /* Returns the local/remote port for the socket. */ 308 309 static int 310 get_sock_port(int sock, int local) 311 { 312 struct sockaddr_storage from; 313 socklen_t fromlen; 314 char strport[NI_MAXSERV]; 315 316 /* Get IP address of client. */ 317 fromlen = sizeof(from); 318 memset(&from, 0, sizeof(from)); 319 if (local) { 320 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) { 321 error("getsockname failed: %.100s", strerror(errno)); 322 return 0; 323 } 324 } else { 325 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { 326 debug("getpeername failed: %.100s", strerror(errno)); 327 fatal_cleanup(); 328 } 329 } 330 331 /* Work around Linux IPv6 weirdness */ 332 if (from.ss_family == AF_INET6) 333 fromlen = sizeof(struct sockaddr_in6); 334 335 /* Return port number. */ 336 if (getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0, 337 strport, sizeof(strport), NI_NUMERICSERV) != 0) 338 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed"); 339 return atoi(strport); 340 } 341 342 /* Returns remote/local port number for the current connection. */ 343 344 static int 345 get_port(int local) 346 { 347 /* 348 * If the connection is not a socket, return 65535. This is 349 * intentionally chosen to be an unprivileged port number. 350 */ 351 if (!packet_connection_is_on_socket()) 352 return 65535; 353 354 /* Get socket and return the port number. */ 355 return get_sock_port(packet_get_connection_in(), local); 356 } 357 358 int 359 get_peer_port(int sock) 360 { 361 return get_sock_port(sock, 0); 362 } 363 364 int 365 get_remote_port(void) 366 { 367 return get_port(0); 368 } 369 370 int 371 get_local_port(void) 372 { 373 return get_port(1); 374 } 375