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 1.27 2001/06/23 15:12:17 itojun 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 reverse_mapping_check) 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 if (from.ss_family == AF_INET) 46 check_ip_options(socket, ntop); 47 48 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop), 49 NULL, 0, NI_NUMERICHOST) != 0) 50 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed"); 51 52 debug3("Trying to reverse map address %.100s.", ntop); 53 /* Map the IP address to a host name. */ 54 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 55 NULL, 0, NI_NAMEREQD) != 0) { 56 /* Host name not found. Use ip address. */ 57 log("Could not reverse map address %.100s.", ntop); 58 return xstrdup(ntop); 59 } 60 61 /* Got host name. */ 62 name[sizeof(name) - 1] = '\0'; 63 /* 64 * Convert it to all lowercase (which is expected by the rest 65 * of this software). 66 */ 67 for (i = 0; name[i]; i++) 68 if (isupper(name[i])) 69 name[i] = tolower(name[i]); 70 71 if (!reverse_mapping_check) 72 return xstrdup(name); 73 /* 74 * Map it back to an IP address and check that the given 75 * address actually is an address of this host. This is 76 * necessary because anyone with access to a name server can 77 * define arbitrary names for an IP address. Mapping from 78 * name to IP address can be trusted better (but can still be 79 * fooled if the intruder has access to the name server of 80 * the domain). 81 */ 82 memset(&hints, 0, sizeof(hints)); 83 hints.ai_family = from.ss_family; 84 hints.ai_socktype = SOCK_STREAM; 85 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 86 log("reverse mapping checking getaddrinfo for %.700s " 87 "failed - POSSIBLE BREAKIN ATTEMPT!", name); 88 return xstrdup(ntop); 89 } 90 /* Look for the address from the list of addresses. */ 91 for (ai = aitop; ai; ai = ai->ai_next) { 92 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 93 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 94 (strcmp(ntop, ntop2) == 0)) 95 break; 96 } 97 freeaddrinfo(aitop); 98 /* If we reached the end of the list, the address was not there. */ 99 if (!ai) { 100 /* Address not found for the host name. */ 101 log("Address %.100s maps to %.600s, but this does not " 102 "map back to the address - POSSIBLE BREAKIN ATTEMPT!", 103 ntop, name); 104 return xstrdup(ntop); 105 } 106 return xstrdup(name); 107 } 108 109 /* 110 * If IP options are supported, make sure there are none (log and 111 * disconnect them if any are found). Basically we are worried about 112 * source routing; it can be used to pretend you are somebody 113 * (ip-address) you are not. That itself may be "almost acceptable" 114 * under certain circumstances, but rhosts autentication is useless 115 * if source routing is accepted. Notice also that if we just dropped 116 * source routing here, the other side could use IP spoofing to do 117 * rest of the interaction and could still bypass security. So we 118 * exit here if we detect any IP options. 119 */ 120 /* IPv4 only */ 121 static void 122 check_ip_options(int socket, char *ipaddr) 123 { 124 u_char options[200]; 125 char text[sizeof(options) * 3 + 1]; 126 socklen_t option_size; 127 int i, ipproto; 128 struct protoent *ip; 129 130 if ((ip = getprotobyname("ip")) != NULL) 131 ipproto = ip->p_proto; 132 else 133 ipproto = IPPROTO_IP; 134 option_size = sizeof(options); 135 if (getsockopt(socket, ipproto, IP_OPTIONS, (void *)options, 136 &option_size) >= 0 && option_size != 0) { 137 text[0] = '\0'; 138 for (i = 0; i < option_size; i++) 139 snprintf(text + i*3, sizeof(text) - i*3, 140 " %2.2x", options[i]); 141 log("Connection from %.100s with IP options:%.800s", 142 ipaddr, text); 143 packet_disconnect("Connection from %.100s with IP options:%.800s", 144 ipaddr, text); 145 } 146 } 147 148 /* 149 * Return the canonical name of the host in the other side of the current 150 * connection. The host name is cached, so it is efficient to call this 151 * several times. 152 */ 153 154 const char * 155 get_canonical_hostname(int reverse_mapping_check) 156 { 157 static char *canonical_host_name = NULL; 158 static int reverse_mapping_checked = 0; 159 160 /* Check if we have previously retrieved name with same option. */ 161 if (canonical_host_name != NULL) { 162 if (reverse_mapping_checked != reverse_mapping_check) 163 xfree(canonical_host_name); 164 else 165 return canonical_host_name; 166 } 167 168 /* Get the real hostname if socket; otherwise return UNKNOWN. */ 169 if (packet_connection_is_on_socket()) 170 canonical_host_name = get_remote_hostname( 171 packet_get_connection_in(), reverse_mapping_check); 172 else 173 canonical_host_name = xstrdup("UNKNOWN"); 174 175 reverse_mapping_checked = reverse_mapping_check; 176 return canonical_host_name; 177 } 178 179 /* 180 * Returns the remote IP-address of socket as a string. The returned 181 * string must be freed. 182 */ 183 static char * 184 get_socket_address(int socket, int remote, int flags) 185 { 186 struct sockaddr_storage addr; 187 socklen_t addrlen; 188 char ntop[NI_MAXHOST]; 189 190 /* Get IP address of client. */ 191 addrlen = sizeof(addr); 192 memset(&addr, 0, sizeof(addr)); 193 194 if (remote) { 195 if (getpeername(socket, (struct sockaddr *)&addr, &addrlen) 196 < 0) { 197 debug("get_socket_ipaddr: getpeername failed: %.100s", 198 strerror(errno)); 199 return NULL; 200 } 201 } else { 202 if (getsockname(socket, (struct sockaddr *)&addr, &addrlen) 203 < 0) { 204 debug("get_socket_ipaddr: getsockname failed: %.100s", 205 strerror(errno)); 206 return NULL; 207 } 208 } 209 /* Get the address in ascii. */ 210 if (getnameinfo((struct sockaddr *)&addr, addrlen, ntop, sizeof(ntop), 211 NULL, 0, flags) != 0) { 212 error("get_socket_ipaddr: getnameinfo %d failed", flags); 213 return NULL; 214 } 215 return xstrdup(ntop); 216 } 217 218 char * 219 get_peer_ipaddr(int socket) 220 { 221 return get_socket_address(socket, 1, NI_NUMERICHOST); 222 } 223 224 char * 225 get_local_ipaddr(int socket) 226 { 227 return get_socket_address(socket, 0, NI_NUMERICHOST); 228 } 229 230 char * 231 get_local_name(int socket) 232 { 233 return get_socket_address(socket, 0, NI_NAMEREQD); 234 } 235 236 /* 237 * Returns the IP-address of the remote host as a string. The returned 238 * string must not be freed. 239 */ 240 241 const char * 242 get_remote_ipaddr() 243 { 244 static char *canonical_host_ip = NULL; 245 246 /* Check whether we have cached the ipaddr. */ 247 if (canonical_host_ip == NULL) { 248 if (packet_connection_is_on_socket()) { 249 canonical_host_ip = 250 get_peer_ipaddr(packet_get_connection_in()); 251 if (canonical_host_ip == NULL) 252 fatal_cleanup(); 253 } else { 254 /* If not on socket, return UNKNOWN. */ 255 canonical_host_ip = xstrdup("UNKNOWN"); 256 } 257 } 258 return canonical_host_ip; 259 } 260 261 const char * 262 get_remote_name_or_ip(u_int utmp_len, int reverse_mapping_check) 263 { 264 static const char *remote = ""; 265 if (utmp_len > 0) 266 remote = get_canonical_hostname(reverse_mapping_check); 267 if (utmp_len == 0 || strlen(remote) > utmp_len) 268 remote = get_remote_ipaddr(); 269 return remote; 270 } 271 272 /* Returns the local/remote port for the socket. */ 273 274 static int 275 get_sock_port(int sock, int local) 276 { 277 struct sockaddr_storage from; 278 socklen_t fromlen; 279 char strport[NI_MAXSERV]; 280 281 /* Get IP address of client. */ 282 fromlen = sizeof(from); 283 memset(&from, 0, sizeof(from)); 284 if (local) { 285 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) { 286 error("getsockname failed: %.100s", strerror(errno)); 287 return 0; 288 } 289 } else { 290 if (getpeername(sock, (struct sockaddr *) & from, &fromlen) < 0) { 291 debug("getpeername failed: %.100s", strerror(errno)); 292 fatal_cleanup(); 293 } 294 } 295 /* Return port number. */ 296 if (getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0, 297 strport, sizeof(strport), NI_NUMERICSERV) != 0) 298 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed"); 299 return atoi(strport); 300 } 301 302 /* Returns remote/local port number for the current connection. */ 303 304 static int 305 get_port(int local) 306 { 307 /* 308 * If the connection is not a socket, return 65535. This is 309 * intentionally chosen to be an unprivileged port number. 310 */ 311 if (!packet_connection_is_on_socket()) 312 return 65535; 313 314 /* Get socket and return the port number. */ 315 return get_sock_port(packet_get_connection_in(), local); 316 } 317 318 int 319 get_peer_port(int sock) 320 { 321 return get_sock_port(sock, 0); 322 } 323 324 int 325 get_remote_port() 326 { 327 return get_port(0); 328 } 329 330 int 331 get_local_port() 332 { 333 return get_port(1); 334 } 335