1 /* $NetBSD: hosts_access.c,v 1.19 2008/12/18 20:16:52 christos Exp $ */ 2 3 /* 4 * This module implements a simple access control language that is based on 5 * host (or domain) names, NIS (host) netgroup names, IP addresses (or 6 * network numbers) and daemon process names. When a match is found the 7 * search is terminated, and depending on whether PROCESS_OPTIONS is defined, 8 * a list of options is executed or an optional shell command is executed. 9 * 10 * Host and user names are looked up on demand, provided that suitable endpoint 11 * information is available as sockaddr_in structures or TLI netbufs. As a 12 * side effect, the pattern matching process may change the contents of 13 * request structure fields. 14 * 15 * Diagnostics are reported through syslog(3). 16 * 17 * Compile with -DNETGROUP if your library provides support for netgroups. 18 * 19 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands. 20 */ 21 22 #include <sys/cdefs.h> 23 #ifndef lint 24 #if 0 25 static char sccsid[] = "@(#) hosts_access.c 1.21 97/02/12 02:13:22"; 26 #else 27 __RCSID("$NetBSD: hosts_access.c,v 1.19 2008/12/18 20:16:52 christos Exp $"); 28 #endif 29 #endif 30 31 /* System libraries. */ 32 33 #include <sys/types.h> 34 #include <sys/param.h> 35 #ifdef INET6 36 #include <sys/socket.h> 37 #endif 38 #include <netinet/in.h> 39 #include <arpa/inet.h> 40 #include <stdio.h> 41 #include <stdlib.h> 42 #include <syslog.h> 43 #include <ctype.h> 44 #include <errno.h> 45 #include <setjmp.h> 46 #include <string.h> 47 #include <netdb.h> 48 #ifdef NETGROUP 49 #include <netgroup.h> 50 #include <rpcsvc/ypclnt.h> 51 #endif 52 53 /* Local stuff. */ 54 55 #include "tcpd.h" 56 57 /* Error handling. */ 58 59 extern jmp_buf tcpd_buf; 60 61 /* Delimiters for lists of daemons or clients. */ 62 63 static char sep[] = ", \t\r\n"; 64 65 /* Constants to be used in assignments only, not in comparisons... */ 66 67 #define YES 1 68 #define NO 0 69 70 /* 71 * These variables are globally visible so that they can be redirected in 72 * verification mode. 73 */ 74 75 char *hosts_allow_table = HOSTS_ALLOW; 76 char *hosts_deny_table = HOSTS_DENY; 77 int hosts_access_verbose = 0; 78 79 /* 80 * In a long-running process, we are not at liberty to just go away. 81 */ 82 83 int resident = (-1); /* -1, 0: unknown; +1: yes */ 84 85 /* Forward declarations. */ 86 87 static int table_match __P((char *, struct request_info *)); 88 static int list_match __P((char *, struct request_info *, 89 int (*)(char *, struct request_info *))); 90 static int server_match __P((char *, struct request_info *)); 91 static int client_match __P((char *, struct request_info *)); 92 static int host_match __P((char *, struct host_info *)); 93 static int hostfile_match __P((char *, struct host_info *)); 94 static int rbl_match __P((char *, char *)); 95 static int string_match __P((char *, char *)); 96 static int masked_match __P((char *, char *, char *)); 97 static int masked_match4 __P((char *, char *, char *)); 98 #ifdef INET6 99 static int masked_match6 __P((char *, char *, char *)); 100 #endif 101 102 /* Size of logical line buffer. */ 103 104 #define BUFLEN 2048 105 106 /* hosts_access - host access control facility */ 107 108 int hosts_access(request) 109 struct request_info *request; 110 { 111 int verdict; 112 113 /* 114 * If the (daemon, client) pair is matched by an entry in the file 115 * /etc/hosts.allow, access is granted. Otherwise, if the (daemon, 116 * client) pair is matched by an entry in the file /etc/hosts.deny, 117 * access is denied. Otherwise, access is granted. A non-existent 118 * access-control file is treated as an empty file. 119 * 120 * After a rule has been matched, the optional language extensions may 121 * decide to grant or refuse service anyway. Or, while a rule is being 122 * processed, a serious error is found, and it seems better to play safe 123 * and deny service. All this is done by jumping back into the 124 * hosts_access() routine, bypassing the regular return from the 125 * table_match() function calls below. 126 */ 127 128 if (resident <= 0) 129 resident++; 130 verdict = setjmp(tcpd_buf); 131 if (verdict != 0) 132 return (verdict == AC_PERMIT); 133 if (table_match(hosts_allow_table, request)) 134 return (YES); 135 if (table_match(hosts_deny_table, request)) 136 return (NO); 137 return (YES); 138 } 139 140 /* table_match - match table entries with (daemon, client) pair */ 141 142 static int table_match(table, request) 143 char *table; 144 struct request_info *request; 145 { 146 FILE *fp; 147 char sv_list[BUFLEN]; /* becomes list of daemons */ 148 char *cl_list; /* becomes list of clients */ 149 char *sh_cmd = NULL; /* becomes optional shell command */ 150 int match = NO; 151 struct tcpd_context saved_context; 152 153 saved_context = tcpd_context; /* stupid compilers */ 154 155 /* 156 * Between the fopen() and fclose() calls, avoid jumps that may cause 157 * file descriptor leaks. 158 */ 159 160 if ((fp = fopen(table, "r")) != 0) { 161 tcpd_context.file = table; 162 tcpd_context.line = 0; 163 while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) { 164 if (sv_list[strlen(sv_list) - 1] != '\n') { 165 tcpd_warn("missing newline or line too long"); 166 continue; 167 } 168 if (sv_list[0] == '#' || sv_list[strspn(sv_list, " \t\r\n")] == 0) 169 continue; 170 if ((cl_list = split_at(sv_list, ':')) == 0) { 171 tcpd_warn("missing \":\" separator"); 172 continue; 173 } 174 sh_cmd = split_at(cl_list, ':'); 175 match = list_match(sv_list, request, server_match) 176 && list_match(cl_list, request, client_match); 177 } 178 (void) fclose(fp); 179 } else if (errno != ENOENT) { 180 tcpd_warn("cannot open %s: %m", table); 181 } 182 if (match) { 183 if (hosts_access_verbose > 1) 184 syslog(LOG_DEBUG, "matched: %s line %d", 185 tcpd_context.file, tcpd_context.line); 186 if (sh_cmd) { 187 #ifdef PROCESS_OPTIONS 188 process_options(sh_cmd, request); 189 #else 190 char cmd[BUFSIZ]; 191 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request)); 192 #endif 193 } 194 } 195 tcpd_context = saved_context; 196 return (match); 197 } 198 199 /* list_match - match a request against a list of patterns with exceptions */ 200 201 static int list_match(list, request, match_fn) 202 char *list; 203 struct request_info *request; 204 int (*match_fn) __P((char *, struct request_info *)); 205 { 206 char *tok; 207 static char *last; 208 int l; 209 210 /* 211 * Process tokens one at a time. We have exhausted all possible matches 212 * when we reach an "EXCEPT" token or the end of the list. If we do find 213 * a match, look for an "EXCEPT" list and recurse to determine whether 214 * the match is affected by any exceptions. 215 */ 216 217 for (tok = strtok_r(list, sep, &last); tok != 0; 218 tok = strtok_r(NULL, sep, &last)) { 219 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */ 220 return (NO); 221 l = strlen(tok); 222 if (*tok == '[' && tok[l - 1] == ']') { 223 tok[l - 1] = '\0'; 224 tok++; 225 } 226 if (match_fn(tok, request)) { /* YES: look for exceptions */ 227 while ((tok = strtok_r(NULL, sep, &last)) && STR_NE(tok, "EXCEPT")) 228 /* VOID */ ; 229 return (tok == 0 || list_match(NULL, request, match_fn) == 0); 230 } 231 } 232 return (NO); 233 } 234 235 /* server_match - match server information */ 236 237 static int server_match(tok, request) 238 char *tok; 239 struct request_info *request; 240 { 241 char *host; 242 243 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */ 244 return (string_match(tok, eval_daemon(request))); 245 } else { /* daemon@host */ 246 return (string_match(tok, eval_daemon(request)) 247 && host_match(host, request->server)); 248 } 249 } 250 251 /* client_match - match client information */ 252 253 static int client_match(tok, request) 254 char *tok; 255 struct request_info *request; 256 { 257 char *host; 258 259 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */ 260 return (host_match(tok, request->client)); 261 } else { /* user@host */ 262 return (host_match(host, request->client) 263 && string_match(tok, eval_user(request))); 264 } 265 } 266 267 /* host_match - match host name and/or address against pattern */ 268 269 static int host_match(tok, host) 270 char *tok; 271 struct host_info *host; 272 { 273 char *mask; 274 275 /* 276 * This code looks a little hairy because we want to avoid unnecessary 277 * hostname lookups. 278 * 279 * The KNOWN pattern requires that both address AND name be known; some 280 * patterns are specific to host names or to host addresses; all other 281 * patterns are satisfied when either the address OR the name match. 282 */ 283 284 if (tok[0] == '@') { /* netgroup: look it up */ 285 #ifdef NETGROUP 286 static char *mydomain = 0; 287 if (mydomain == 0) 288 yp_get_default_domain(&mydomain); 289 return (innetgr(tok + 1, eval_hostname(host), NULL, mydomain)); 290 #else 291 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */ 292 return (NO); 293 #endif 294 } else if (tok[0] == '/') { /* /file hack */ 295 return (hostfile_match(tok, host)); 296 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */ 297 char *name = eval_hostname(host); 298 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name)); 299 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */ 300 char *name = eval_hostname(host); 301 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name)); 302 } else if (strncmp(tok, "{RBL}.", 6) == 0) { /* RBL lookup in domain */ 303 return rbl_match(tok+6, eval_hostaddr(host)); 304 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */ 305 return (masked_match(tok, mask, eval_hostaddr(host))); 306 } else { /* anything else */ 307 return (string_match(tok, eval_hostaddr(host)) 308 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host)))); 309 } 310 } 311 312 /* hostfile_match - look up host patterns from file */ 313 314 static int hostfile_match(path, host) 315 char *path; 316 struct host_info *host; 317 { 318 char tok[BUFSIZ]; 319 int match = NO; 320 FILE *fp; 321 322 if ((fp = fopen(path, "r")) != 0) { 323 while (fscanf(fp, "%s", tok) == 1 && !(match = host_match(tok, host))) 324 /* void */ ; 325 fclose(fp); 326 } else if (errno != ENOENT) { 327 tcpd_warn("open %s: %m", path); 328 } 329 return (match); 330 } 331 332 /* rbl_match() - match host by looking up in RBL domain */ 333 334 static int rbl_match(rbl_domain, rbl_hostaddr) 335 char *rbl_domain; /* RBL domain */ 336 char *rbl_hostaddr; /* hostaddr */ 337 { 338 char *rbl_name; 339 unsigned long host_address; 340 int ret = NO; 341 size_t len = strlen(rbl_domain) + (4 * 4) + 2; 342 343 if (dot_quad_addr(rbl_hostaddr, &host_address) != 0) { 344 tcpd_warn("unable to convert %s to address", rbl_hostaddr); 345 return (NO); 346 } 347 host_address = ntohl(host_address); 348 /* construct the rbl name to look up */ 349 if ((rbl_name = malloc(len)) == NULL) { 350 tcpd_jump("not enough memory to build RBL name for %s in %s", rbl_hostaddr, rbl_domain); 351 /* NOTREACHED */ 352 } 353 snprintf(rbl_name, len, "%u.%u.%u.%u.%s", 354 (unsigned int) ((host_address) & 0xff), 355 (unsigned int) ((host_address >> 8) & 0xff), 356 (unsigned int) ((host_address >> 16) & 0xff), 357 (unsigned int) ((host_address >> 24) & 0xff), 358 rbl_domain); 359 /* look it up */ 360 if (gethostbyname(rbl_name) != NULL) { 361 /* successful lookup - they're on the RBL list */ 362 ret = YES; 363 } 364 free(rbl_name); 365 366 return ret; 367 } 368 369 /* string_match - match string against pattern */ 370 371 static int string_match(tok, string) 372 char *tok; 373 char *string; 374 { 375 int n; 376 377 if (tok[0] == '.') { /* suffix */ 378 n = strlen(string) - strlen(tok); 379 return (n > 0 && STR_EQ(tok, string + n)); 380 } else if (STR_EQ(tok, "ALL")) { /* all: match any */ 381 return (YES); 382 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */ 383 return (STR_NE(string, unknown)); 384 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */ 385 return (STRN_EQ(tok, string, n)); 386 } else { /* exact match */ 387 return (STR_EQ(tok, string)); 388 } 389 } 390 391 /* masked_match - match address against netnumber/netmask */ 392 393 static int masked_match(net_tok, mask_tok, string) 394 char *net_tok; 395 char *mask_tok; 396 char *string; 397 { 398 #ifndef INET6 399 return masked_match4(net_tok, mask_tok, string); 400 #else 401 /* 402 * masked_match4() is kept just for supporting shortened IPv4 address form. 403 * If we could get rid of shortened IPv4 form, we could just always use 404 * masked_match6(). 405 */ 406 if (dot_quad_addr(net_tok, NULL) != INADDR_NONE && 407 dot_quad_addr(mask_tok, NULL) != INADDR_NONE && 408 dot_quad_addr(string, NULL) != INADDR_NONE) { 409 return masked_match4(net_tok, mask_tok, string); 410 } else 411 return masked_match6(net_tok, mask_tok, string); 412 #endif 413 } 414 415 static int masked_match4(net_tok, mask_tok, string) 416 char *net_tok; 417 char *mask_tok; 418 char *string; 419 { 420 unsigned long net; 421 unsigned long mask; 422 unsigned long addr; 423 424 /* 425 * Disallow forms other than dotted quad: the treatment that inet_addr() 426 * gives to forms with less than four components is inconsistent with the 427 * access control language. John P. Rouillard <rouilj@cs.umb.edu>. 428 */ 429 430 if (dot_quad_addr(string, &addr) != 0) 431 return (NO); 432 if (dot_quad_addr(net_tok, &net) != 0 || 433 dot_quad_addr(mask_tok, &mask) != 0) { 434 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok); 435 return (NO); /* not tcpd_jump() */ 436 } 437 438 if ((net & ~mask) != 0) 439 tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok); 440 441 return ((addr & mask) == net); 442 } 443 444 #ifdef INET6 445 static int masked_match6(net_tok, mask_tok, string) 446 char *net_tok; 447 char *mask_tok; 448 char *string; 449 { 450 union { 451 struct sockaddr sa; 452 struct sockaddr_in sin; 453 struct sockaddr_in6 sin6; 454 } net, mask, addr; 455 struct addrinfo hints, *res; 456 unsigned long masklen; 457 char *ep; 458 int i; 459 char *np, *mp, *ap; 460 int alen; 461 462 memset(&hints, 0, sizeof(hints)); 463 hints.ai_family = PF_UNSPEC; 464 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 465 hints.ai_flags = AI_NUMERICHOST; 466 if (getaddrinfo(net_tok, "0", &hints, &res) == 0) { 467 if (res->ai_addrlen > sizeof(net) || res->ai_next) { 468 freeaddrinfo(res); 469 return NO; 470 } 471 memcpy(&net, res->ai_addr, res->ai_addrlen); 472 freeaddrinfo(res); 473 } else 474 return NO; 475 476 memset(&hints, 0, sizeof(hints)); 477 hints.ai_family = net.sa.sa_family; 478 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 479 hints.ai_flags = AI_NUMERICHOST; 480 ep = NULL; 481 if (getaddrinfo(mask_tok, "0", &hints, &res) == 0) { 482 if (res->ai_family == AF_INET6 && 483 ((struct sockaddr_in6 *)res->ai_addr)->sin6_scope_id) { 484 freeaddrinfo(res); 485 return NO; 486 } 487 if (res->ai_addrlen > sizeof(mask) || res->ai_next) { 488 freeaddrinfo(res); 489 return NO; 490 } 491 memcpy(&mask, res->ai_addr, res->ai_addrlen); 492 freeaddrinfo(res); 493 } else { 494 ep = NULL; 495 masklen = strtoul(mask_tok, &ep, 10); 496 if (ep && !*ep) { 497 memset(&mask, 0, sizeof(mask)); 498 mask.sa.sa_family = net.sa.sa_family; 499 mask.sa.sa_len = net.sa.sa_len; 500 switch (mask.sa.sa_family) { 501 case AF_INET: 502 mp = (char *)&mask.sin.sin_addr; 503 alen = sizeof(mask.sin.sin_addr); 504 break; 505 case AF_INET6: 506 mp = (char *)&mask.sin6.sin6_addr; 507 alen = sizeof(mask.sin6.sin6_addr); 508 break; 509 default: 510 return NO; 511 } 512 if (masklen / 8 > alen) 513 return NO; 514 memset(mp, 0xff, masklen / 8); 515 if (masklen % 8) 516 mp[masklen / 8] = 0xff00 >> (masklen % 8); 517 } else 518 return NO; 519 } 520 521 memset(&hints, 0, sizeof(hints)); 522 hints.ai_family = PF_UNSPEC; 523 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 524 hints.ai_flags = AI_NUMERICHOST; 525 if (getaddrinfo(string, "0", &hints, &res) == 0) { 526 if (res->ai_addrlen > sizeof(addr) || res->ai_next) { 527 freeaddrinfo(res); 528 return NO; 529 } 530 /* special case - IPv4 mapped address */ 531 if (net.sa.sa_family == AF_INET && res->ai_family == AF_INET6 && 532 IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)res->ai_addr)->sin6_addr)) { 533 memset(&addr, 0, sizeof(addr)); 534 addr.sa.sa_family = net.sa.sa_family; 535 addr.sa.sa_len = net.sa.sa_len; 536 memcpy(&addr.sin.sin_addr, 537 &((struct sockaddr_in6 *)res->ai_addr)->sin6_addr.s6_addr[12], 538 sizeof(addr.sin.sin_addr)); 539 } else 540 memcpy(&addr, res->ai_addr, res->ai_addrlen); 541 freeaddrinfo(res); 542 } else 543 return NO; 544 545 if (net.sa.sa_family != mask.sa.sa_family || 546 net.sa.sa_family != addr.sa.sa_family) { 547 return NO; 548 } 549 550 switch (net.sa.sa_family) { 551 case AF_INET: 552 np = (char *)&net.sin.sin_addr; 553 mp = (char *)&mask.sin.sin_addr; 554 ap = (char *)&addr.sin.sin_addr; 555 alen = sizeof(net.sin.sin_addr); 556 break; 557 case AF_INET6: 558 np = (char *)&net.sin6.sin6_addr; 559 mp = (char *)&mask.sin6.sin6_addr; 560 ap = (char *)&addr.sin6.sin6_addr; 561 alen = sizeof(net.sin6.sin6_addr); 562 break; 563 default: 564 return NO; 565 } 566 567 for (i = 0; i < alen; i++) 568 if (np[i] & ~mp[i]) { 569 tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok); 570 break; 571 } 572 573 for (i = 0; i < alen; i++) 574 ap[i] &= mp[i]; 575 576 if (addr.sa.sa_family == AF_INET6 && addr.sin6.sin6_scope_id && 577 addr.sin6.sin6_scope_id != net.sin6.sin6_scope_id) 578 return NO; 579 return (memcmp(ap, np, alen) == 0); 580 } 581 #endif 582