1 /* $NetBSD: hosts_access.c,v 1.20 2012/03/21 10:10:37 matt 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 1.20 2012/03/21 10:10:37 matt 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 const char *hosts_allow_table = HOSTS_ALLOW; 76 const 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(const char *, struct request_info *); 88 static int list_match(char *, struct request_info *, 89 int (*)(char *, struct request_info *)); 90 static int server_match(char *, struct request_info *); 91 static int client_match(char *, struct request_info *); 92 static int host_match(char *, struct host_info *); 93 static int hostfile_match(char *, struct host_info *); 94 static int rbl_match(char *, char *); 95 static int string_match(char *, char *); 96 static int masked_match(char *, char *, char *); 97 static int masked_match4(char *, char *, char *); 98 #ifdef INET6 99 static int masked_match6(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 109 hosts_access(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 143 table_match(const char *table, struct request_info *request) 144 { 145 FILE *fp; 146 char sv_list[BUFLEN]; /* becomes list of daemons */ 147 char *cl_list; /* becomes list of clients */ 148 char *sh_cmd = NULL; /* becomes optional shell command */ 149 int match = NO; 150 struct tcpd_context saved_context; 151 152 saved_context = tcpd_context; /* stupid compilers */ 153 154 /* 155 * Between the fopen() and fclose() calls, avoid jumps that may cause 156 * file descriptor leaks. 157 */ 158 159 if ((fp = fopen(table, "r")) != 0) { 160 tcpd_context.file = table; 161 tcpd_context.line = 0; 162 while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) { 163 if (sv_list[strlen(sv_list) - 1] != '\n') { 164 tcpd_warn("missing newline or line too long"); 165 continue; 166 } 167 if (sv_list[0] == '#' || sv_list[strspn(sv_list, " \t\r\n")] == 0) 168 continue; 169 if ((cl_list = split_at(sv_list, ':')) == 0) { 170 tcpd_warn("missing \":\" separator"); 171 continue; 172 } 173 sh_cmd = split_at(cl_list, ':'); 174 match = list_match(sv_list, request, server_match) 175 && list_match(cl_list, request, client_match); 176 } 177 (void) fclose(fp); 178 } else if (errno != ENOENT) { 179 tcpd_warn("cannot open %s: %m", table); 180 } 181 if (match) { 182 if (hosts_access_verbose > 1) 183 syslog(LOG_DEBUG, "matched: %s line %d", 184 tcpd_context.file, tcpd_context.line); 185 if (sh_cmd) { 186 #ifdef PROCESS_OPTIONS 187 process_options(sh_cmd, request); 188 #else 189 char cmd[BUFSIZ]; 190 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request)); 191 #endif 192 } 193 } 194 tcpd_context = saved_context; 195 return (match); 196 } 197 198 /* list_match - match a request against a list of patterns with exceptions */ 199 200 static int 201 list_match(char *list, struct request_info *request, 202 int (*match_fn)(char *, struct request_info *)) 203 { 204 char *tok; 205 static char *last; 206 int l; 207 208 /* 209 * Process tokens one at a time. We have exhausted all possible matches 210 * when we reach an "EXCEPT" token or the end of the list. If we do find 211 * a match, look for an "EXCEPT" list and recurse to determine whether 212 * the match is affected by any exceptions. 213 */ 214 215 for (tok = strtok_r(list, sep, &last); tok != 0; 216 tok = strtok_r(NULL, sep, &last)) { 217 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */ 218 return (NO); 219 l = strlen(tok); 220 if (*tok == '[' && tok[l - 1] == ']') { 221 tok[l - 1] = '\0'; 222 tok++; 223 } 224 if (match_fn(tok, request)) { /* YES: look for exceptions */ 225 while ((tok = strtok_r(NULL, sep, &last)) && STR_NE(tok, "EXCEPT")) 226 /* VOID */ ; 227 return (tok == 0 || list_match(NULL, request, match_fn) == 0); 228 } 229 } 230 return (NO); 231 } 232 233 /* server_match - match server information */ 234 235 static int 236 server_match(char *tok, struct request_info *request) 237 { 238 char *host; 239 240 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */ 241 return (string_match(tok, eval_daemon(request))); 242 } else { /* daemon@host */ 243 return (string_match(tok, eval_daemon(request)) 244 && host_match(host, request->server)); 245 } 246 } 247 248 /* client_match - match client information */ 249 250 static int 251 client_match(char *tok, struct request_info *request) 252 { 253 char *host; 254 255 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */ 256 return (host_match(tok, request->client)); 257 } else { /* user@host */ 258 return (host_match(host, request->client) 259 && string_match(tok, eval_user(request))); 260 } 261 } 262 263 /* host_match - match host name and/or address against pattern */ 264 265 static int 266 host_match(char *tok, struct host_info *host) 267 { 268 char *mask; 269 270 /* 271 * This code looks a little hairy because we want to avoid unnecessary 272 * hostname lookups. 273 * 274 * The KNOWN pattern requires that both address AND name be known; some 275 * patterns are specific to host names or to host addresses; all other 276 * patterns are satisfied when either the address OR the name match. 277 */ 278 279 if (tok[0] == '@') { /* netgroup: look it up */ 280 #ifdef NETGROUP 281 static char *mydomain = 0; 282 if (mydomain == 0) 283 yp_get_default_domain(&mydomain); 284 return (innetgr(tok + 1, eval_hostname(host), NULL, mydomain)); 285 #else 286 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */ 287 return (NO); 288 #endif 289 } else if (tok[0] == '/') { /* /file hack */ 290 return (hostfile_match(tok, host)); 291 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */ 292 char *name = eval_hostname(host); 293 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name)); 294 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */ 295 char *name = eval_hostname(host); 296 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name)); 297 } else if (strncmp(tok, "{RBL}.", 6) == 0) { /* RBL lookup in domain */ 298 return rbl_match(tok+6, eval_hostaddr(host)); 299 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */ 300 return (masked_match(tok, mask, eval_hostaddr(host))); 301 } else { /* anything else */ 302 return (string_match(tok, eval_hostaddr(host)) 303 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host)))); 304 } 305 } 306 307 /* hostfile_match - look up host patterns from file */ 308 309 static int 310 hostfile_match(char *path, struct host_info *host) 311 { 312 char tok[BUFSIZ]; 313 int match = NO; 314 FILE *fp; 315 316 if ((fp = fopen(path, "r")) != 0) { 317 while (fscanf(fp, "%s", tok) == 1 && !(match = host_match(tok, host))) 318 /* void */ ; 319 fclose(fp); 320 } else if (errno != ENOENT) { 321 tcpd_warn("open %s: %m", path); 322 } 323 return (match); 324 } 325 326 /* rbl_match() - match host by looking up in RBL domain */ 327 328 static int 329 rbl_match( 330 char *rbl_domain, /* RBL domain */ 331 char *rbl_hostaddr) /* hostaddr */ 332 { 333 char *rbl_name; 334 unsigned long host_address; 335 int ret = NO; 336 size_t len = strlen(rbl_domain) + (4 * 4) + 2; 337 338 if (dot_quad_addr(rbl_hostaddr, &host_address) != 0) { 339 tcpd_warn("unable to convert %s to address", rbl_hostaddr); 340 return (NO); 341 } 342 host_address = ntohl(host_address); 343 /* construct the rbl name to look up */ 344 if ((rbl_name = malloc(len)) == NULL) { 345 tcpd_jump("not enough memory to build RBL name for %s in %s", rbl_hostaddr, rbl_domain); 346 /* NOTREACHED */ 347 } 348 snprintf(rbl_name, len, "%u.%u.%u.%u.%s", 349 (unsigned int) ((host_address) & 0xff), 350 (unsigned int) ((host_address >> 8) & 0xff), 351 (unsigned int) ((host_address >> 16) & 0xff), 352 (unsigned int) ((host_address >> 24) & 0xff), 353 rbl_domain); 354 /* look it up */ 355 if (gethostbyname(rbl_name) != NULL) { 356 /* successful lookup - they're on the RBL list */ 357 ret = YES; 358 } 359 free(rbl_name); 360 361 return ret; 362 } 363 364 /* string_match - match string against pattern */ 365 366 static int 367 string_match(char *tok, char *string) 368 { 369 int n; 370 371 if (tok[0] == '.') { /* suffix */ 372 n = strlen(string) - strlen(tok); 373 return (n > 0 && STR_EQ(tok, string + n)); 374 } else if (STR_EQ(tok, "ALL")) { /* all: match any */ 375 return (YES); 376 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */ 377 return (STR_NE(string, unknown)); 378 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */ 379 return (STRN_EQ(tok, string, n)); 380 } else { /* exact match */ 381 return (STR_EQ(tok, string)); 382 } 383 } 384 385 /* masked_match - match address against netnumber/netmask */ 386 387 static int 388 masked_match(char *net_tok, char *mask_tok, char *string) 389 { 390 #ifndef INET6 391 return masked_match4(net_tok, mask_tok, string); 392 #else 393 /* 394 * masked_match4() is kept just for supporting shortened IPv4 address form. 395 * If we could get rid of shortened IPv4 form, we could just always use 396 * masked_match6(). 397 */ 398 if (dot_quad_addr(net_tok, NULL) != -1 && 399 dot_quad_addr(mask_tok, NULL) != -1 && 400 dot_quad_addr(string, NULL) != -1) { 401 return masked_match4(net_tok, mask_tok, string); 402 } else 403 return masked_match6(net_tok, mask_tok, string); 404 #endif 405 } 406 407 static int 408 masked_match4(char *net_tok, char *mask_tok, char *string) 409 { 410 unsigned long net; 411 unsigned long mask; 412 unsigned long addr; 413 414 /* 415 * Disallow forms other than dotted quad: the treatment that inet_addr() 416 * gives to forms with less than four components is inconsistent with the 417 * access control language. John P. Rouillard <rouilj@cs.umb.edu>. 418 */ 419 420 if (dot_quad_addr(string, &addr) != 0) 421 return (NO); 422 if (dot_quad_addr(net_tok, &net) != 0 || 423 dot_quad_addr(mask_tok, &mask) != 0) { 424 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok); 425 return (NO); /* not tcpd_jump() */ 426 } 427 428 if ((net & ~mask) != 0) 429 tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok); 430 431 return ((addr & mask) == net); 432 } 433 434 #ifdef INET6 435 static int 436 masked_match6(char *net_tok, char *mask_tok, char *string) 437 { 438 union { 439 struct sockaddr sa; 440 struct sockaddr_in sin; 441 struct sockaddr_in6 sin6; 442 } net, mask, addr; 443 struct addrinfo hints, *res; 444 unsigned long masklen; 445 char *ep; 446 size_t i; 447 char *np, *mp, *ap; 448 size_t alen; 449 450 memset(&hints, 0, sizeof(hints)); 451 hints.ai_family = PF_UNSPEC; 452 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 453 hints.ai_flags = AI_NUMERICHOST; 454 if (getaddrinfo(net_tok, "0", &hints, &res) == 0) { 455 if (res->ai_addrlen > sizeof(net) || res->ai_next) { 456 freeaddrinfo(res); 457 return NO; 458 } 459 memcpy(&net, res->ai_addr, res->ai_addrlen); 460 freeaddrinfo(res); 461 } else 462 return NO; 463 464 memset(&hints, 0, sizeof(hints)); 465 hints.ai_family = net.sa.sa_family; 466 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 467 hints.ai_flags = AI_NUMERICHOST; 468 ep = NULL; 469 if (getaddrinfo(mask_tok, "0", &hints, &res) == 0) { 470 if (res->ai_family == AF_INET6 && 471 ((struct sockaddr_in6 *)res->ai_addr)->sin6_scope_id) { 472 freeaddrinfo(res); 473 return NO; 474 } 475 if (res->ai_addrlen > sizeof(mask) || res->ai_next) { 476 freeaddrinfo(res); 477 return NO; 478 } 479 memcpy(&mask, res->ai_addr, res->ai_addrlen); 480 freeaddrinfo(res); 481 } else { 482 ep = NULL; 483 masklen = strtoul(mask_tok, &ep, 10); 484 if (ep && !*ep) { 485 memset(&mask, 0, sizeof(mask)); 486 mask.sa.sa_family = net.sa.sa_family; 487 mask.sa.sa_len = net.sa.sa_len; 488 switch (mask.sa.sa_family) { 489 case AF_INET: 490 mp = (char *)&mask.sin.sin_addr; 491 alen = sizeof(mask.sin.sin_addr); 492 break; 493 case AF_INET6: 494 mp = (char *)&mask.sin6.sin6_addr; 495 alen = sizeof(mask.sin6.sin6_addr); 496 break; 497 default: 498 return NO; 499 } 500 if (masklen / 8 > alen) 501 return NO; 502 memset(mp, 0xff, masklen / 8); 503 if (masklen % 8) 504 mp[masklen / 8] = 0xff00 >> (masklen % 8); 505 } else 506 return NO; 507 } 508 509 memset(&hints, 0, sizeof(hints)); 510 hints.ai_family = PF_UNSPEC; 511 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 512 hints.ai_flags = AI_NUMERICHOST; 513 if (getaddrinfo(string, "0", &hints, &res) == 0) { 514 if (res->ai_addrlen > sizeof(addr) || res->ai_next) { 515 freeaddrinfo(res); 516 return NO; 517 } 518 /* special case - IPv4 mapped address */ 519 if (net.sa.sa_family == AF_INET && res->ai_family == AF_INET6 && 520 IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)res->ai_addr)->sin6_addr)) { 521 memset(&addr, 0, sizeof(addr)); 522 addr.sa.sa_family = net.sa.sa_family; 523 addr.sa.sa_len = net.sa.sa_len; 524 memcpy(&addr.sin.sin_addr, 525 &((struct sockaddr_in6 *)res->ai_addr)->sin6_addr.s6_addr[12], 526 sizeof(addr.sin.sin_addr)); 527 } else 528 memcpy(&addr, res->ai_addr, res->ai_addrlen); 529 freeaddrinfo(res); 530 } else 531 return NO; 532 533 if (net.sa.sa_family != mask.sa.sa_family || 534 net.sa.sa_family != addr.sa.sa_family) { 535 return NO; 536 } 537 538 switch (net.sa.sa_family) { 539 case AF_INET: 540 np = (char *)&net.sin.sin_addr; 541 mp = (char *)&mask.sin.sin_addr; 542 ap = (char *)&addr.sin.sin_addr; 543 alen = sizeof(net.sin.sin_addr); 544 break; 545 case AF_INET6: 546 np = (char *)&net.sin6.sin6_addr; 547 mp = (char *)&mask.sin6.sin6_addr; 548 ap = (char *)&addr.sin6.sin6_addr; 549 alen = sizeof(net.sin6.sin6_addr); 550 break; 551 default: 552 return NO; 553 } 554 555 for (i = 0; i < alen; i++) 556 if (np[i] & ~mp[i]) { 557 tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok); 558 break; 559 } 560 561 for (i = 0; i < alen; i++) 562 ap[i] &= mp[i]; 563 564 if (addr.sa.sa_family == AF_INET6 && addr.sin6.sin6_scope_id && 565 addr.sin6.sin6_scope_id != net.sin6.sin6_scope_id) 566 return NO; 567 return (memcmp(ap, np, alen) == 0); 568 } 569 #endif 570