1 /* 2 * This module determines the type of socket (datagram, stream), the client 3 * socket address and port, the server socket address and port. In addition, 4 * it provides methods to map a transport address to a printable host name 5 * or address. Socket address information results are in static memory. 6 * 7 * The result from the hostname lookup method is STRING_PARANOID when a host 8 * pretends to have someone elses name, or when a host name is available but 9 * could not be verified. 10 * 11 * When lookup or conversion fails the result is set to STRING_UNKNOWN. 12 * 13 * Diagnostics are reported through syslog(3). 14 * 15 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands. 16 * 17 * $FreeBSD$ 18 */ 19 20 #ifndef lint 21 static char sccsid[] = "@(#) socket.c 1.15 97/03/21 19:27:24"; 22 #endif 23 24 /* System libraries. */ 25 26 #include <sys/types.h> 27 #include <sys/param.h> 28 #include <sys/socket.h> 29 #include <netinet/in.h> 30 #include <netdb.h> 31 #include <stdio.h> 32 #include <syslog.h> 33 #include <string.h> 34 35 #ifndef INET6 36 extern char *inet_ntoa(); 37 #endif 38 39 /* Local stuff. */ 40 41 #include "tcpd.h" 42 43 /* Forward declarations. */ 44 45 static void sock_sink(); 46 47 #ifdef APPEND_DOT 48 49 /* 50 * Speed up DNS lookups by terminating the host name with a dot. Should be 51 * done with care. The speedup can give problems with lookups from sources 52 * that lack DNS-style trailing dot magic, such as local files or NIS maps. 53 */ 54 55 static struct hostent *gethostbyname_dot(name) 56 char *name; 57 { 58 char dot_name[MAXHOSTNAMELEN + 1]; 59 60 /* 61 * Don't append dots to unqualified names. Such names are likely to come 62 * from local hosts files or from NIS. 63 */ 64 65 if (strchr(name, '.') == 0 || strlen(name) >= MAXHOSTNAMELEN - 1) { 66 return (gethostbyname(name)); 67 } else { 68 sprintf(dot_name, "%s.", name); 69 return (gethostbyname(dot_name)); 70 } 71 } 72 73 #define gethostbyname gethostbyname_dot 74 #endif 75 76 /* sock_host - look up endpoint addresses and install conversion methods */ 77 78 void sock_host(request) 79 struct request_info *request; 80 { 81 #ifdef INET6 82 static struct sockaddr_storage client; 83 static struct sockaddr_storage server; 84 #else 85 static struct sockaddr_in client; 86 static struct sockaddr_in server; 87 #endif 88 int len; 89 char buf[BUFSIZ]; 90 int fd = request->fd; 91 92 sock_methods(request); 93 94 /* 95 * Look up the client host address. Hal R. Brand <BRAND@addvax.llnl.gov> 96 * suggested how to get the client host info in case of UDP connections: 97 * peek at the first message without actually looking at its contents. We 98 * really should verify that client.sin_family gets the value AF_INET, 99 * but this program has already caused too much grief on systems with 100 * broken library code. 101 */ 102 103 len = sizeof(client); 104 if (getpeername(fd, (struct sockaddr *) & client, &len) < 0) { 105 request->sink = sock_sink; 106 len = sizeof(client); 107 if (recvfrom(fd, buf, sizeof(buf), MSG_PEEK, 108 (struct sockaddr *) & client, &len) < 0) { 109 tcpd_warn("can't get client address: %m"); 110 return; /* give up */ 111 } 112 #ifdef really_paranoid 113 memset(buf, 0, sizeof(buf)); 114 #endif 115 } 116 #ifdef INET6 117 request->client->sin = (struct sockaddr *)&client; 118 #else 119 request->client->sin = &client; 120 #endif 121 122 /* 123 * Determine the server binding. This is used for client username 124 * lookups, and for access control rules that trigger on the server 125 * address or name. 126 */ 127 128 len = sizeof(server); 129 if (getsockname(fd, (struct sockaddr *) & server, &len) < 0) { 130 tcpd_warn("getsockname: %m"); 131 return; 132 } 133 #ifdef INET6 134 request->server->sin = (struct sockaddr *)&server; 135 #else 136 request->server->sin = &server; 137 #endif 138 } 139 140 /* sock_hostaddr - map endpoint address to printable form */ 141 142 void sock_hostaddr(host) 143 struct host_info *host; 144 { 145 #ifdef INET6 146 struct sockaddr *sin = host->sin; 147 int salen; 148 149 if (!sin) 150 return; 151 #ifdef SIN6_LEN 152 salen = sin->sa_len; 153 #else 154 salen = (sin->sa_family == AF_INET) ? sizeof(struct sockaddr_in) 155 : sizeof(struct sockaddr_in6); 156 #endif 157 getnameinfo(sin, salen, host->addr, sizeof(host->addr), 158 NULL, 0, NI_NUMERICHOST); 159 #else 160 struct sockaddr_in *sin = host->sin; 161 162 if (sin != 0) 163 STRN_CPY(host->addr, inet_ntoa(sin->sin_addr), sizeof(host->addr)); 164 #endif 165 } 166 167 /* sock_hostname - map endpoint address to host name */ 168 169 void sock_hostname(host) 170 struct host_info *host; 171 { 172 #ifdef INET6 173 struct sockaddr *sin = host->sin; 174 struct sockaddr_in sin4; 175 struct addrinfo hints, *res, *res0 = NULL; 176 int salen, alen, err = 1; 177 char *ap = NULL, *rap, hname[NI_MAXHOST]; 178 179 if (sin != NULL) { 180 if (sin->sa_family == AF_INET6) { 181 struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sin; 182 183 if (IN6_IS_ADDR_V4MAPPED(&sin6->sin6_addr)) { 184 memset(&sin4, 0, sizeof(sin4)); 185 #ifdef SIN6_LEN 186 sin4.sin_len = sizeof(sin4); 187 #endif 188 sin4.sin_family = AF_INET; 189 sin4.sin_port = sin6->sin6_port; 190 sin4.sin_addr.s_addr = *(u_int32_t *)&sin6->sin6_addr.s6_addr[12]; 191 sin = (struct sockaddr *)&sin4; 192 } 193 } 194 switch (sin->sa_family) { 195 case AF_INET: 196 ap = (char *)&((struct sockaddr_in *)sin)->sin_addr; 197 alen = sizeof(struct in_addr); 198 salen = sizeof(struct sockaddr_in); 199 break; 200 case AF_INET6: 201 ap = (char *)&((struct sockaddr_in6 *)sin)->sin6_addr; 202 alen = sizeof(struct in6_addr); 203 salen = sizeof(struct sockaddr_in6); 204 break; 205 default: 206 break; 207 } 208 if (ap) 209 err = getnameinfo(sin, salen, hname, sizeof(hname), 210 NULL, 0, NI_NAMEREQD); 211 } 212 if (!err) { 213 214 STRN_CPY(host->name, hname, sizeof(host->name)); 215 216 /* reject numeric addresses */ 217 memset(&hints, 0, sizeof(hints)); 218 hints.ai_family = sin->sa_family; 219 hints.ai_socktype = SOCK_STREAM; 220 hints.ai_flags = AI_PASSIVE | AI_CANONNAME | AI_NUMERICHOST; 221 if ((err = getaddrinfo(host->name, NULL, &hints, &res0)) == 0) { 222 freeaddrinfo(res0); 223 tcpd_warn("host name/name mismatch: " 224 "reverse lookup results in non-FQDN %s", 225 host->name); 226 strcpy(host->name, paranoid); /* name is bad, clobber it */ 227 } 228 err = !err; 229 } 230 if (!err) { 231 /* we are now sure that this is non-numeric */ 232 233 /* 234 * Verify that the address is a member of the address list returned 235 * by gethostbyname(hostname). 236 * 237 * Verify also that gethostbyaddr() and gethostbyname() return the same 238 * hostname, or rshd and rlogind may still end up being spoofed. 239 * 240 * On some sites, gethostbyname("localhost") returns "localhost.domain". 241 * This is a DNS artefact. We treat it as a special case. When we 242 * can't believe the address list from gethostbyname("localhost") 243 * we're in big trouble anyway. 244 */ 245 246 memset(&hints, 0, sizeof(hints)); 247 hints.ai_family = sin->sa_family; 248 hints.ai_socktype = SOCK_STREAM; 249 hints.ai_flags = AI_PASSIVE | AI_CANONNAME; 250 if (getaddrinfo(host->name, NULL, &hints, &res0) != 0) { 251 252 /* 253 * Unable to verify that the host name matches the address. This 254 * may be a transient problem or a botched name server setup. 255 */ 256 257 tcpd_warn("can't verify hostname: getaddrinfo(%s, %s) failed", 258 host->name, 259 (sin->sa_family == AF_INET) ? "AF_INET" : "AF_INET6"); 260 261 } else if ((res0->ai_canonname == NULL 262 || STR_NE(host->name, res0->ai_canonname)) 263 && STR_NE(host->name, "localhost")) { 264 265 /* 266 * The gethostbyaddr() and gethostbyname() calls did not return 267 * the same hostname. This could be a nameserver configuration 268 * problem. It could also be that someone is trying to spoof us. 269 */ 270 271 tcpd_warn("host name/name mismatch: %s != %.*s", 272 host->name, STRING_LENGTH, 273 (res0->ai_canonname == NULL) ? "" : res0->ai_canonname); 274 275 } else { 276 277 /* 278 * The address should be a member of the address list returned by 279 * gethostbyname(). We should first verify that the h_addrtype 280 * field is AF_INET, but this program has already caused too much 281 * grief on systems with broken library code. 282 */ 283 284 for (res = res0; res; res = res->ai_next) { 285 if (res->ai_family != sin->sa_family) 286 continue; 287 switch (res->ai_family) { 288 case AF_INET: 289 rap = (char *)&((struct sockaddr_in *)res->ai_addr)->sin_addr; 290 break; 291 case AF_INET6: 292 /* need to check scope_id */ 293 if (((struct sockaddr_in6 *)sin)->sin6_scope_id != 294 ((struct sockaddr_in6 *)res->ai_addr)->sin6_scope_id) { 295 continue; 296 } 297 rap = (char *)&((struct sockaddr_in6 *)res->ai_addr)->sin6_addr; 298 break; 299 default: 300 continue; 301 } 302 if (memcmp(rap, ap, alen) == 0) { 303 freeaddrinfo(res0); 304 return; /* name is good, keep it */ 305 } 306 } 307 308 /* 309 * The host name does not map to the initial address. Perhaps 310 * someone has messed up. Perhaps someone compromised a name 311 * server. 312 */ 313 314 getnameinfo(sin, salen, hname, sizeof(hname), 315 NULL, 0, NI_NUMERICHOST); 316 tcpd_warn("host name/address mismatch: %s != %.*s", 317 hname, STRING_LENGTH, 318 (res0->ai_canonname == NULL) ? "" : res0->ai_canonname); 319 } 320 strcpy(host->name, paranoid); /* name is bad, clobber it */ 321 if (res0) 322 freeaddrinfo(res0); 323 } 324 #else /* INET6 */ 325 struct sockaddr_in *sin = host->sin; 326 struct hostent *hp; 327 int i; 328 329 /* 330 * On some systems, for example Solaris 2.3, gethostbyaddr(0.0.0.0) does 331 * not fail. Instead it returns "INADDR_ANY". Unfortunately, this does 332 * not work the other way around: gethostbyname("INADDR_ANY") fails. We 333 * have to special-case 0.0.0.0, in order to avoid false alerts from the 334 * host name/address checking code below. 335 */ 336 if (sin != 0 && sin->sin_addr.s_addr != 0 337 && (hp = gethostbyaddr((char *) &(sin->sin_addr), 338 sizeof(sin->sin_addr), AF_INET)) != 0) { 339 340 STRN_CPY(host->name, hp->h_name, sizeof(host->name)); 341 342 /* 343 * Verify that the address is a member of the address list returned 344 * by gethostbyname(hostname). 345 * 346 * Verify also that gethostbyaddr() and gethostbyname() return the same 347 * hostname, or rshd and rlogind may still end up being spoofed. 348 * 349 * On some sites, gethostbyname("localhost") returns "localhost.domain". 350 * This is a DNS artefact. We treat it as a special case. When we 351 * can't believe the address list from gethostbyname("localhost") 352 * we're in big trouble anyway. 353 */ 354 355 if ((hp = gethostbyname(host->name)) == 0) { 356 357 /* 358 * Unable to verify that the host name matches the address. This 359 * may be a transient problem or a botched name server setup. 360 */ 361 362 tcpd_warn("can't verify hostname: gethostbyname(%s) failed", 363 host->name); 364 365 } else if (STR_NE(host->name, hp->h_name) 366 && STR_NE(host->name, "localhost")) { 367 368 /* 369 * The gethostbyaddr() and gethostbyname() calls did not return 370 * the same hostname. This could be a nameserver configuration 371 * problem. It could also be that someone is trying to spoof us. 372 */ 373 374 tcpd_warn("host name/name mismatch: %s != %.*s", 375 host->name, STRING_LENGTH, hp->h_name); 376 377 } else { 378 379 /* 380 * The address should be a member of the address list returned by 381 * gethostbyname(). We should first verify that the h_addrtype 382 * field is AF_INET, but this program has already caused too much 383 * grief on systems with broken library code. 384 */ 385 386 for (i = 0; hp->h_addr_list[i]; i++) { 387 if (memcmp(hp->h_addr_list[i], 388 (char *) &sin->sin_addr, 389 sizeof(sin->sin_addr)) == 0) 390 return; /* name is good, keep it */ 391 } 392 393 /* 394 * The host name does not map to the initial address. Perhaps 395 * someone has messed up. Perhaps someone compromised a name 396 * server. 397 */ 398 399 tcpd_warn("host name/address mismatch: %s != %.*s", 400 inet_ntoa(sin->sin_addr), STRING_LENGTH, hp->h_name); 401 } 402 strcpy(host->name, paranoid); /* name is bad, clobber it */ 403 } 404 #endif /* INET6 */ 405 } 406 407 /* sock_sink - absorb unreceived IP datagram */ 408 409 static void sock_sink(fd) 410 int fd; 411 { 412 char buf[BUFSIZ]; 413 #ifdef INET6 414 struct sockaddr_storage sin; 415 #else 416 struct sockaddr_in sin; 417 #endif 418 int size = sizeof(sin); 419 420 /* 421 * Eat up the not-yet received datagram. Some systems insist on a 422 * non-zero source address argument in the recvfrom() call below. 423 */ 424 425 (void) recvfrom(fd, buf, sizeof(buf), 0, (struct sockaddr *) & sin, &size); 426 } 427