1 /* $NetBSD: hosts_access.c,v 1.18 2006/01/08 17:20:28 jdc 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 1.18 2006/01/08 17:20:28 jdc 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 rbl_match __P((char *, char *)); 94 static int string_match __P((char *, char *)); 95 static int masked_match __P((char *, char *, char *)); 96 static int masked_match4 __P((char *, char *, char *)); 97 #ifdef INET6 98 static int masked_match6 __P((char *, char *, char *)); 99 #endif 100 101 /* Size of logical line buffer. */ 102 103 #define BUFLEN 2048 104 105 /* hosts_access - host access control facility */ 106 107 int hosts_access(request) 108 struct request_info *request; 109 { 110 int verdict; 111 112 /* 113 * If the (daemon, client) pair is matched by an entry in the file 114 * /etc/hosts.allow, access is granted. Otherwise, if the (daemon, 115 * client) pair is matched by an entry in the file /etc/hosts.deny, 116 * access is denied. Otherwise, access is granted. A non-existent 117 * access-control file is treated as an empty file. 118 * 119 * After a rule has been matched, the optional language extensions may 120 * decide to grant or refuse service anyway. Or, while a rule is being 121 * processed, a serious error is found, and it seems better to play safe 122 * and deny service. All this is done by jumping back into the 123 * hosts_access() routine, bypassing the regular return from the 124 * table_match() function calls below. 125 */ 126 127 if (resident <= 0) 128 resident++; 129 verdict = setjmp(tcpd_buf); 130 if (verdict != 0) 131 return (verdict == AC_PERMIT); 132 if (table_match(hosts_allow_table, request)) 133 return (YES); 134 if (table_match(hosts_deny_table, request)) 135 return (NO); 136 return (YES); 137 } 138 139 /* table_match - match table entries with (daemon, client) pair */ 140 141 static int table_match(table, request) 142 char *table; 143 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 list_match(list, request, match_fn) 201 char *list; 202 struct request_info *request; 203 int (*match_fn) __P((char *, struct request_info *)); 204 { 205 char *tok; 206 static char *last; 207 int l; 208 209 /* 210 * Process tokens one at a time. We have exhausted all possible matches 211 * when we reach an "EXCEPT" token or the end of the list. If we do find 212 * a match, look for an "EXCEPT" list and recurse to determine whether 213 * the match is affected by any exceptions. 214 */ 215 216 for (tok = strtok_r(list, sep, &last); tok != 0; 217 tok = strtok_r(NULL, sep, &last)) { 218 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */ 219 return (NO); 220 l = strlen(tok); 221 if (*tok == '[' && tok[l - 1] == ']') { 222 tok[l - 1] = '\0'; 223 tok++; 224 } 225 if (match_fn(tok, request)) { /* YES: look for exceptions */ 226 while ((tok = strtok_r(NULL, sep, &last)) && STR_NE(tok, "EXCEPT")) 227 /* VOID */ ; 228 return (tok == 0 || list_match(NULL, request, match_fn) == 0); 229 } 230 } 231 return (NO); 232 } 233 234 /* server_match - match server information */ 235 236 static int server_match(tok, request) 237 char *tok; 238 struct request_info *request; 239 { 240 char *host; 241 242 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */ 243 return (string_match(tok, eval_daemon(request))); 244 } else { /* daemon@host */ 245 return (string_match(tok, eval_daemon(request)) 246 && host_match(host, request->server)); 247 } 248 } 249 250 /* client_match - match client information */ 251 252 static int client_match(tok, request) 253 char *tok; 254 struct request_info *request; 255 { 256 char *host; 257 258 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */ 259 return (host_match(tok, request->client)); 260 } else { /* user@host */ 261 return (host_match(host, request->client) 262 && string_match(tok, eval_user(request))); 263 } 264 } 265 266 /* host_match - match host name and/or address against pattern */ 267 268 static int host_match(tok, host) 269 char *tok; 270 struct host_info *host; 271 { 272 char *mask; 273 274 /* 275 * This code looks a little hairy because we want to avoid unnecessary 276 * hostname lookups. 277 * 278 * The KNOWN pattern requires that both address AND name be known; some 279 * patterns are specific to host names or to host addresses; all other 280 * patterns are satisfied when either the address OR the name match. 281 */ 282 283 if (tok[0] == '@') { /* netgroup: look it up */ 284 #ifdef NETGROUP 285 static char *mydomain = 0; 286 if (mydomain == 0) 287 yp_get_default_domain(&mydomain); 288 return (innetgr(tok + 1, eval_hostname(host), NULL, mydomain)); 289 #else 290 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */ 291 return (NO); 292 #endif 293 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */ 294 char *name = eval_hostname(host); 295 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name)); 296 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */ 297 char *name = eval_hostname(host); 298 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name)); 299 } else if (strncmp(tok, "{RBL}.", 6) == 0) { /* RBL lookup in domain */ 300 return rbl_match(tok+6, eval_hostaddr(host)); 301 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */ 302 return (masked_match(tok, mask, eval_hostaddr(host))); 303 } else { /* anything else */ 304 return (string_match(tok, eval_hostaddr(host)) 305 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host)))); 306 } 307 } 308 309 /* rbl_match() - match host by looking up in RBL domain */ 310 311 static int rbl_match(rbl_domain, rbl_hostaddr) 312 char *rbl_domain; /* RBL domain */ 313 char *rbl_hostaddr; /* hostaddr */ 314 { 315 char *rbl_name; 316 unsigned long host_address; 317 int ret = NO; 318 size_t len = strlen(rbl_domain) + (4 * 4) + 2; 319 320 if (dot_quad_addr(rbl_hostaddr, &host_address) != 0) { 321 tcpd_warn("unable to convert %s to address", rbl_hostaddr); 322 return (NO); 323 } 324 host_address = ntohl(host_address); 325 /* construct the rbl name to look up */ 326 if ((rbl_name = malloc(len)) == NULL) { 327 tcpd_jump("not enough memory to build RBL name for %s in %s", rbl_hostaddr, rbl_domain); 328 /* NOTREACHED */ 329 } 330 snprintf(rbl_name, len, "%u.%u.%u.%u.%s", 331 (unsigned int) ((host_address) & 0xff), 332 (unsigned int) ((host_address >> 8) & 0xff), 333 (unsigned int) ((host_address >> 16) & 0xff), 334 (unsigned int) ((host_address >> 24) & 0xff), 335 rbl_domain); 336 /* look it up */ 337 if (gethostbyname(rbl_name) != NULL) { 338 /* successful lookup - they're on the RBL list */ 339 ret = YES; 340 } 341 free(rbl_name); 342 343 return ret; 344 } 345 346 /* string_match - match string against pattern */ 347 348 static int string_match(tok, string) 349 char *tok; 350 char *string; 351 { 352 int n; 353 354 if (tok[0] == '.') { /* suffix */ 355 n = strlen(string) - strlen(tok); 356 return (n > 0 && STR_EQ(tok, string + n)); 357 } else if (STR_EQ(tok, "ALL")) { /* all: match any */ 358 return (YES); 359 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */ 360 return (STR_NE(string, unknown)); 361 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */ 362 return (STRN_EQ(tok, string, n)); 363 } else { /* exact match */ 364 return (STR_EQ(tok, string)); 365 } 366 } 367 368 /* masked_match - match address against netnumber/netmask */ 369 370 static int masked_match(net_tok, mask_tok, string) 371 char *net_tok; 372 char *mask_tok; 373 char *string; 374 { 375 #ifndef INET6 376 return masked_match4(net_tok, mask_tok, string); 377 #else 378 /* 379 * masked_match4() is kept just for supporting shortened IPv4 address form. 380 * If we could get rid of shortened IPv4 form, we could just always use 381 * masked_match6(). 382 */ 383 if (dot_quad_addr(net_tok, NULL) != INADDR_NONE && 384 dot_quad_addr(mask_tok, NULL) != INADDR_NONE && 385 dot_quad_addr(string, NULL) != INADDR_NONE) { 386 return masked_match4(net_tok, mask_tok, string); 387 } else 388 return masked_match6(net_tok, mask_tok, string); 389 #endif 390 } 391 392 static int masked_match4(net_tok, mask_tok, string) 393 char *net_tok; 394 char *mask_tok; 395 char *string; 396 { 397 unsigned long net; 398 unsigned long mask; 399 unsigned long addr; 400 401 /* 402 * Disallow forms other than dotted quad: the treatment that inet_addr() 403 * gives to forms with less than four components is inconsistent with the 404 * access control language. John P. Rouillard <rouilj@cs.umb.edu>. 405 */ 406 407 if (dot_quad_addr(string, &addr) != 0) 408 return (NO); 409 if (dot_quad_addr(net_tok, &net) != 0 || 410 dot_quad_addr(mask_tok, &mask) != 0) { 411 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok); 412 return (NO); /* not tcpd_jump() */ 413 } 414 415 if ((net & ~mask) != 0) 416 tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok); 417 418 return ((addr & mask) == net); 419 } 420 421 #ifdef INET6 422 static int masked_match6(net_tok, mask_tok, string) 423 char *net_tok; 424 char *mask_tok; 425 char *string; 426 { 427 union { 428 struct sockaddr sa; 429 struct sockaddr_in sin; 430 struct sockaddr_in6 sin6; 431 } net, mask, addr; 432 struct addrinfo hints, *res; 433 unsigned long masklen; 434 char *ep; 435 int i; 436 char *np, *mp, *ap; 437 int alen; 438 439 memset(&hints, 0, sizeof(hints)); 440 hints.ai_family = PF_UNSPEC; 441 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 442 hints.ai_flags = AI_NUMERICHOST; 443 if (getaddrinfo(net_tok, "0", &hints, &res) == 0) { 444 if (res->ai_addrlen > sizeof(net) || res->ai_next) { 445 freeaddrinfo(res); 446 return NO; 447 } 448 memcpy(&net, res->ai_addr, res->ai_addrlen); 449 freeaddrinfo(res); 450 } else 451 return NO; 452 453 memset(&hints, 0, sizeof(hints)); 454 hints.ai_family = net.sa.sa_family; 455 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 456 hints.ai_flags = AI_NUMERICHOST; 457 ep = NULL; 458 if (getaddrinfo(mask_tok, "0", &hints, &res) == 0) { 459 if (res->ai_family == AF_INET6 && 460 ((struct sockaddr_in6 *)res->ai_addr)->sin6_scope_id) { 461 freeaddrinfo(res); 462 return NO; 463 } 464 if (res->ai_addrlen > sizeof(mask) || res->ai_next) { 465 freeaddrinfo(res); 466 return NO; 467 } 468 memcpy(&mask, res->ai_addr, res->ai_addrlen); 469 freeaddrinfo(res); 470 } else { 471 ep = NULL; 472 masklen = strtoul(mask_tok, &ep, 10); 473 if (ep && !*ep) { 474 memset(&mask, 0, sizeof(mask)); 475 mask.sa.sa_family = net.sa.sa_family; 476 mask.sa.sa_len = net.sa.sa_len; 477 switch (mask.sa.sa_family) { 478 case AF_INET: 479 mp = (char *)&mask.sin.sin_addr; 480 alen = sizeof(mask.sin.sin_addr); 481 break; 482 case AF_INET6: 483 mp = (char *)&mask.sin6.sin6_addr; 484 alen = sizeof(mask.sin6.sin6_addr); 485 break; 486 default: 487 return NO; 488 } 489 if (masklen / 8 > alen) 490 return NO; 491 memset(mp, 0xff, masklen / 8); 492 if (masklen % 8) 493 mp[masklen / 8] = 0xff00 >> (masklen % 8); 494 } else 495 return NO; 496 } 497 498 memset(&hints, 0, sizeof(hints)); 499 hints.ai_family = PF_UNSPEC; 500 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 501 hints.ai_flags = AI_NUMERICHOST; 502 if (getaddrinfo(string, "0", &hints, &res) == 0) { 503 if (res->ai_addrlen > sizeof(addr) || res->ai_next) { 504 freeaddrinfo(res); 505 return NO; 506 } 507 /* special case - IPv4 mapped address */ 508 if (net.sa.sa_family == AF_INET && res->ai_family == AF_INET6 && 509 IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)res->ai_addr)->sin6_addr)) { 510 memset(&addr, 0, sizeof(addr)); 511 addr.sa.sa_family = net.sa.sa_family; 512 addr.sa.sa_len = net.sa.sa_len; 513 memcpy(&addr.sin.sin_addr, 514 &((struct sockaddr_in6 *)res->ai_addr)->sin6_addr.s6_addr[12], 515 sizeof(addr.sin.sin_addr)); 516 } else 517 memcpy(&addr, res->ai_addr, res->ai_addrlen); 518 freeaddrinfo(res); 519 } else 520 return NO; 521 522 if (net.sa.sa_family != mask.sa.sa_family || 523 net.sa.sa_family != addr.sa.sa_family) { 524 return NO; 525 } 526 527 switch (net.sa.sa_family) { 528 case AF_INET: 529 np = (char *)&net.sin.sin_addr; 530 mp = (char *)&mask.sin.sin_addr; 531 ap = (char *)&addr.sin.sin_addr; 532 alen = sizeof(net.sin.sin_addr); 533 break; 534 case AF_INET6: 535 np = (char *)&net.sin6.sin6_addr; 536 mp = (char *)&mask.sin6.sin6_addr; 537 ap = (char *)&addr.sin6.sin6_addr; 538 alen = sizeof(net.sin6.sin6_addr); 539 break; 540 default: 541 return NO; 542 } 543 544 for (i = 0; i < alen; i++) 545 if (np[i] & ~mp[i]) { 546 tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok); 547 break; 548 } 549 550 for (i = 0; i < alen; i++) 551 ap[i] &= mp[i]; 552 553 if (addr.sa.sa_family == AF_INET6 && addr.sin6.sin6_scope_id && 554 addr.sin6.sin6_scope_id != net.sin6.sin6_scope_id) 555 return NO; 556 return (memcmp(ap, np, alen) == 0); 557 } 558 #endif 559