1 /* $NetBSD: hosts_access.c,v 1.14 2002/05/24 05:38:20 itojun 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 1.14 2002/05/24 05:38:20 itojun 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 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(list, sep); tok != 0; tok = strtok((char *) 0, sep)) { 216 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */ 217 return (NO); 218 l = strlen(tok); 219 if (*tok == '[' && tok[l - 1] == ']') { 220 tok[l - 1] = '\0'; 221 tok++; 222 } 223 if (match_fn(tok, request)) { /* YES: look for exceptions */ 224 while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT")) 225 /* VOID */ ; 226 return (tok == 0 || list_match((char *) 0, request, match_fn) == 0); 227 } 228 } 229 return (NO); 230 } 231 232 /* server_match - match server information */ 233 234 static int server_match(tok, request) 235 char *tok; 236 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 client_match(tok, request) 251 char *tok; 252 struct request_info *request; 253 { 254 char *host; 255 256 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */ 257 return (host_match(tok, request->client)); 258 } else { /* user@host */ 259 return (host_match(host, request->client) 260 && string_match(tok, eval_user(request))); 261 } 262 } 263 264 /* host_match - match host name and/or address against pattern */ 265 266 static int host_match(tok, host) 267 char *tok; 268 struct host_info *host; 269 { 270 char *mask; 271 272 /* 273 * This code looks a little hairy because we want to avoid unnecessary 274 * hostname lookups. 275 * 276 * The KNOWN pattern requires that both address AND name be known; some 277 * patterns are specific to host names or to host addresses; all other 278 * patterns are satisfied when either the address OR the name match. 279 */ 280 281 if (tok[0] == '@') { /* netgroup: look it up */ 282 #ifdef NETGROUP 283 static char *mydomain = 0; 284 if (mydomain == 0) 285 yp_get_default_domain(&mydomain); 286 return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain)); 287 #else 288 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */ 289 return (NO); 290 #endif 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 /* rbl_match() - match host by looking up in RBL domain */ 308 309 static int rbl_match(rbl_domain, rbl_hostaddr) 310 char *rbl_domain; /* RBL domain */ 311 char *rbl_hostaddr; /* hostaddr */ 312 { 313 char *rbl_name; 314 unsigned long host_address; 315 int ret = NO; 316 size_t len = strlen(rbl_domain) + (4 * 4) + 2; 317 318 if (dot_quad_addr(rbl_hostaddr, &host_address) != 0) { 319 tcpd_warn("unable to convert %s to address", rbl_hostaddr); 320 return (NO); 321 } 322 /* construct the rbl name to look up */ 323 if ((rbl_name = malloc(len)) == NULL) { 324 tcpd_jump("not enough memory to build RBL name for %s in %s", rbl_hostaddr, rbl_domain); 325 /* NOTREACHED */ 326 } 327 snprintf(rbl_name, len, "%u.%u.%u.%u.%s", 328 (unsigned int) ((host_address) & 0xff), 329 (unsigned int) ((host_address >> 8) & 0xff), 330 (unsigned int) ((host_address >> 16) & 0xff), 331 (unsigned int) ((host_address >> 24) & 0xff), 332 rbl_domain); 333 /* look it up */ 334 if (gethostbyname(rbl_name) != NULL) { 335 /* successful lookup - they're on the RBL list */ 336 ret = YES; 337 } 338 free(rbl_name); 339 340 return ret; 341 } 342 343 /* string_match - match string against pattern */ 344 345 static int string_match(tok, string) 346 char *tok; 347 char *string; 348 { 349 int n; 350 351 if (tok[0] == '.') { /* suffix */ 352 n = strlen(string) - strlen(tok); 353 return (n > 0 && STR_EQ(tok, string + n)); 354 } else if (STR_EQ(tok, "ALL")) { /* all: match any */ 355 return (YES); 356 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */ 357 return (STR_NE(string, unknown)); 358 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */ 359 return (STRN_EQ(tok, string, n)); 360 } else { /* exact match */ 361 return (STR_EQ(tok, string)); 362 } 363 } 364 365 /* masked_match - match address against netnumber/netmask */ 366 367 static int masked_match(net_tok, mask_tok, string) 368 char *net_tok; 369 char *mask_tok; 370 char *string; 371 { 372 #ifndef INET6 373 return masked_match4(net_tok, mask_tok, string); 374 #else 375 if (dot_quad_addr(net_tok, NULL) != INADDR_NONE 376 && dot_quad_addr(mask_tok, NULL) != INADDR_NONE 377 && dot_quad_addr(string, NULL) != INADDR_NONE) { 378 return masked_match4(net_tok, mask_tok, string); 379 } else 380 return masked_match6(net_tok, mask_tok, string); 381 #endif 382 } 383 384 static int masked_match4(net_tok, mask_tok, string) 385 char *net_tok; 386 char *mask_tok; 387 char *string; 388 { 389 unsigned long net; 390 unsigned long mask; 391 unsigned long addr; 392 393 /* 394 * Disallow forms other than dotted quad: the treatment that inet_addr() 395 * gives to forms with less than four components is inconsistent with the 396 * access control language. John P. Rouillard <rouilj@cs.umb.edu>. 397 */ 398 399 if (dot_quad_addr(string, &addr) != 0) 400 return (NO); 401 if (dot_quad_addr(net_tok, &net) != 0 402 || dot_quad_addr(mask_tok, &mask) != 0) { 403 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok); 404 return (NO); /* not tcpd_jump() */ 405 } 406 407 if ((net & ~mask) != 0) 408 tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok); 409 410 return ((addr & mask) == net); 411 } 412 413 #ifdef INET6 414 /* Ugly because it covers IPv4 mapped address. I hate mapped addresses. */ 415 static int masked_match6(net_tok, mask_tok, string) 416 char *net_tok; 417 char *mask_tok; 418 char *string; 419 { 420 struct in6_addr net; 421 struct in6_addr mask; 422 struct in6_addr addr; 423 int masklen; 424 int fail; 425 int i; 426 int maskoff; 427 int netaf; 428 int dirty; 429 const int sizoff64 = sizeof(struct in6_addr) - sizeof(struct in_addr); 430 431 memset(&addr, 0, sizeof(addr)); 432 if (inet_pton(AF_INET6, string, &addr) == 1) 433 ; /* okay */ 434 else if (inet_pton(AF_INET, string, &addr.s6_addr[sizoff64]) == 1) 435 addr.s6_addr[10] = addr.s6_addr[11] = 0xff; 436 else 437 return NO; 438 439 memset(&net, 0, sizeof(net)); 440 if (inet_pton(AF_INET6, net_tok, &net) == 1) { 441 netaf = AF_INET6; 442 maskoff = 0; 443 } else if (inet_pton(AF_INET, net_tok, &net.s6_addr[sizoff64]) == 1) { 444 netaf = AF_INET; 445 maskoff = sizoff64; 446 net.s6_addr[10] = net.s6_addr[11] = 0xff; 447 } else 448 return NO; 449 450 fail = 0; 451 if (mask_tok[strspn(mask_tok, "0123456789")] == '\0') { 452 masklen = atoi(mask_tok) + maskoff * 8; 453 if (0 <= masklen && masklen <= 128) { 454 memset(&mask, 0, sizeof(mask)); 455 memset(&mask, 0xff, masklen / 8); 456 if (masklen % 8) { 457 ((u_char *)&mask)[masklen / 8] = 458 (0xff00 >> (masklen % 8)) & 0xff; 459 } 460 } else 461 fail++; 462 } else if (netaf == AF_INET6 && inet_pton(AF_INET6, mask_tok, &mask) == 1) 463 ; /* okay */ 464 else if (netaf == AF_INET 465 && inet_pton(AF_INET, mask_tok, &mask.s6_addr[12]) == 1) { 466 memset(&mask, 0xff, sizoff64); 467 } else 468 fail++; 469 if (fail) { 470 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok); 471 return (NO); /* not tcpd_jump() */ 472 } 473 474 dirty = 0; 475 for (i = 0; i < sizeof(addr); i++) { 476 addr.s6_addr[i] &= mask.s6_addr[i]; 477 dirty |= (net.s6_addr[i] & ~mask.s6_addr[i]); 478 } 479 480 if (dirty) 481 tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok); 482 483 return (memcmp(&addr, &net, sizeof(addr)) == 0); 484 } 485 #endif 486