1 /* 2 * This module implements a simple access control language that is based on 3 * host (or domain) names, NIS (host) netgroup names, IP addresses (or 4 * network numbers) and daemon process names. When a match is found the 5 * search is terminated, and depending on whether PROCESS_OPTIONS is defined, 6 * a list of options is executed or an optional shell command is executed. 7 * 8 * Host and user names are looked up on demand, provided that suitable endpoint 9 * information is available as sockaddr_in structures or TLI netbufs. As a 10 * side effect, the pattern matching process may change the contents of 11 * request structure fields. 12 * 13 * Diagnostics are reported through syslog(3). 14 * 15 * Compile with -DNETGROUP if your library provides support for netgroups. 16 * 17 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands. 18 * 19 * $FreeBSD$ 20 */ 21 22 #ifndef lint 23 static char sccsid[] = "@(#) hosts_access.c 1.21 97/02/12 02:13:22"; 24 #endif 25 26 /* System libraries. */ 27 28 #include <sys/types.h> 29 #ifdef INT32_T 30 typedef uint32_t u_int32_t; 31 #endif 32 #include <sys/param.h> 33 #ifdef INET6 34 #include <sys/socket.h> 35 #endif 36 #include <netinet/in.h> 37 #include <arpa/inet.h> 38 #include <stdio.h> 39 #include <syslog.h> 40 #include <ctype.h> 41 #include <errno.h> 42 #include <setjmp.h> 43 #include <string.h> 44 #ifdef INET6 45 #include <netdb.h> 46 #endif 47 #include <stdlib.h> 48 49 extern char *fgets(); 50 extern int errno; 51 52 #ifndef INADDR_NONE 53 #define INADDR_NONE (-1) /* XXX should be 0xffffffff */ 54 #endif 55 56 /* Local stuff. */ 57 58 #include "tcpd.h" 59 60 /* Error handling. */ 61 62 extern jmp_buf tcpd_buf; 63 64 /* Delimiters for lists of daemons or clients. */ 65 66 static char sep[] = ", \t\r\n"; 67 68 /* Constants to be used in assignments only, not in comparisons... */ 69 70 #define YES 1 71 #define NO 0 72 73 /* 74 * These variables are globally visible so that they can be redirected in 75 * verification mode. 76 */ 77 78 char *hosts_allow_table = HOSTS_ALLOW; 79 char *hosts_deny_table = HOSTS_DENY; 80 int hosts_access_verbose = 0; 81 82 /* 83 * In a long-running process, we are not at liberty to just go away. 84 */ 85 86 int resident = (-1); /* -1, 0: unknown; +1: yes */ 87 88 /* Forward declarations. */ 89 90 static int table_match(); 91 static int list_match(); 92 static int server_match(); 93 static int client_match(); 94 static int host_match(); 95 static int string_match(); 96 static int masked_match(); 97 #ifdef INET6 98 static int masked_match4(); 99 static int masked_match6(); 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; /* becomes optional shell command */ 150 int match = NO; 151 struct tcpd_context saved_context; 152 char *cp; 153 154 saved_context = tcpd_context; /* stupid compilers */ 155 156 /* 157 * Between the fopen() and fclose() calls, avoid jumps that may cause 158 * file descriptor leaks. 159 */ 160 161 if ((fp = fopen(table, "r")) != 0) { 162 tcpd_context.file = table; 163 tcpd_context.line = 0; 164 while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) { 165 if (sv_list[strlen(sv_list) - 1] != '\n') { 166 tcpd_warn("missing newline or line too long"); 167 continue; 168 } 169 /* Ignore anything after unescaped # character */ 170 for (cp = strchr(sv_list, '#'); cp != NULL;) { 171 if (cp > sv_list && cp[-1] == '\\') { 172 cp = strchr(cp + 1, '#'); 173 continue; 174 } 175 *cp = '\0'; 176 break; 177 } 178 if (sv_list[strspn(sv_list, " \t\r\n")] == 0) 179 continue; 180 if ((cl_list = split_at(sv_list, ':')) == 0) { 181 tcpd_warn("missing \":\" separator"); 182 continue; 183 } 184 sh_cmd = split_at(cl_list, ':'); 185 match = list_match(sv_list, request, server_match) 186 && list_match(cl_list, request, client_match); 187 } 188 (void) fclose(fp); 189 } else if (errno != ENOENT) { 190 tcpd_warn("cannot open %s: %m", table); 191 } 192 if (match) { 193 if (hosts_access_verbose > 1) 194 syslog(LOG_DEBUG, "matched: %s line %d", 195 tcpd_context.file, tcpd_context.line); 196 if (sh_cmd) { 197 #ifdef PROCESS_OPTIONS 198 process_options(sh_cmd, request); 199 #else 200 char cmd[BUFSIZ]; 201 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request)); 202 #endif 203 } 204 } 205 tcpd_context = saved_context; 206 return (match); 207 } 208 209 /* list_match - match a request against a list of patterns with exceptions */ 210 211 static int list_match(list, request, match_fn) 212 char *list; 213 struct request_info *request; 214 int (*match_fn) (); 215 { 216 char *tok; 217 218 /* 219 * Process tokens one at a time. We have exhausted all possible matches 220 * when we reach an "EXCEPT" token or the end of the list. If we do find 221 * a match, look for an "EXCEPT" list and recurse to determine whether 222 * the match is affected by any exceptions. 223 */ 224 225 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) { 226 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */ 227 return (NO); 228 if (match_fn(tok, request)) { /* YES: look for exceptions */ 229 while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT")) 230 /* VOID */ ; 231 return (tok == 0 || list_match((char *) 0, request, match_fn) == 0); 232 } 233 } 234 return (NO); 235 } 236 237 /* server_match - match server information */ 238 239 static int server_match(tok, request) 240 char *tok; 241 struct request_info *request; 242 { 243 char *host; 244 245 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */ 246 return (string_match(tok, eval_daemon(request))); 247 } else { /* daemon@host */ 248 return (string_match(tok, eval_daemon(request)) 249 && host_match(host, request->server)); 250 } 251 } 252 253 /* client_match - match client information */ 254 255 static int client_match(tok, request) 256 char *tok; 257 struct request_info *request; 258 { 259 char *host; 260 261 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */ 262 return (host_match(tok, request->client)); 263 } else { /* user@host */ 264 return (host_match(host, request->client) 265 && string_match(tok, eval_user(request))); 266 } 267 } 268 269 /* hostfile_match - look up host patterns from file */ 270 271 static int hostfile_match(path, host) 272 char *path; 273 struct hosts_info *host; 274 { 275 char tok[BUFSIZ]; 276 int match = NO; 277 FILE *fp; 278 279 if ((fp = fopen(path, "r")) != 0) { 280 while (fscanf(fp, "%s", tok) == 1 && !(match = host_match(tok, host))) 281 /* void */ ; 282 fclose(fp); 283 } else if (errno != ENOENT) { 284 tcpd_warn("open %s: %m", path); 285 } 286 return (match); 287 } 288 289 /* host_match - match host name and/or address against pattern */ 290 291 static int host_match(tok, host) 292 char *tok; 293 struct host_info *host; 294 { 295 char *mask; 296 297 /* 298 * This code looks a little hairy because we want to avoid unnecessary 299 * hostname lookups. 300 * 301 * The KNOWN pattern requires that both address AND name be known; some 302 * patterns are specific to host names or to host addresses; all other 303 * patterns are satisfied when either the address OR the name match. 304 */ 305 306 if (tok[0] == '@') { /* netgroup: look it up */ 307 #ifdef NETGROUP 308 static char *mydomain = 0; 309 if (mydomain == 0) 310 yp_get_default_domain(&mydomain); 311 return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain)); 312 #else 313 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */ 314 return (NO); 315 #endif 316 } else if (tok[0] == '/') { /* /file hack */ 317 return (hostfile_match(tok, host)); 318 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */ 319 char *name = eval_hostname(host); 320 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name)); 321 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */ 322 char *name = eval_hostname(host); 323 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name)); 324 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */ 325 return (masked_match(tok, mask, eval_hostaddr(host))); 326 } else { /* anything else */ 327 return (string_match(tok, eval_hostaddr(host)) 328 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host)))); 329 } 330 } 331 332 /* string_match - match string against pattern */ 333 334 static int string_match(tok, string) 335 char *tok; 336 char *string; 337 { 338 int n; 339 340 #ifdef INET6 341 /* convert IPv4 mapped IPv6 address to IPv4 address */ 342 if (STRN_EQ(string, "::ffff:", 7) 343 && dot_quad_addr(string + 7) != INADDR_NONE) { 344 string += 7; 345 } 346 #endif 347 if (tok[0] == '.') { /* suffix */ 348 n = strlen(string) - strlen(tok); 349 return (n > 0 && STR_EQ(tok, string + n)); 350 } else if (STR_EQ(tok, "ALL")) { /* all: match any */ 351 return (YES); 352 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */ 353 return (STR_NE(string, unknown)); 354 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */ 355 return (STRN_EQ(tok, string, n)); 356 } else { /* exact match */ 357 #ifdef INET6 358 struct addrinfo hints, *res; 359 struct sockaddr_in6 pat, addr; 360 int len, ret; 361 char ch; 362 363 len = strlen(tok); 364 if (*tok == '[' && tok[len - 1] == ']') { 365 ch = tok[len - 1]; 366 tok[len - 1] = '\0'; 367 memset(&hints, 0, sizeof(hints)); 368 hints.ai_family = AF_INET6; 369 hints.ai_socktype = SOCK_STREAM; 370 hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST; 371 if ((ret = getaddrinfo(tok + 1, NULL, &hints, &res)) == 0) { 372 memcpy(&pat, res->ai_addr, sizeof(pat)); 373 freeaddrinfo(res); 374 } 375 tok[len - 1] = ch; 376 if (ret != 0 || getaddrinfo(string, NULL, &hints, &res) != 0) 377 return NO; 378 memcpy(&addr, res->ai_addr, sizeof(addr)); 379 freeaddrinfo(res); 380 if (pat.sin6_scope_id != 0 && 381 addr.sin6_scope_id != pat.sin6_scope_id) 382 return NO; 383 return (!memcmp(&pat.sin6_addr, &addr.sin6_addr, 384 sizeof(struct in6_addr))); 385 return (ret); 386 } 387 #endif 388 return (STR_EQ(tok, string)); 389 } 390 } 391 392 /* masked_match - match address against netnumber/netmask */ 393 394 #ifdef INET6 395 static int masked_match(net_tok, mask_tok, string) 396 char *net_tok; 397 char *mask_tok; 398 char *string; 399 { 400 return (masked_match4(net_tok, mask_tok, string) || 401 masked_match6(net_tok, mask_tok, string)); 402 } 403 404 static int masked_match4(net_tok, mask_tok, string) 405 #else 406 static int masked_match(net_tok, mask_tok, string) 407 #endif 408 char *net_tok; 409 char *mask_tok; 410 char *string; 411 { 412 #ifdef INET6 413 u_int32_t net; 414 u_int32_t mask; 415 u_int32_t addr; 416 #else 417 unsigned long net; 418 unsigned long mask; 419 unsigned long addr; 420 #endif 421 422 /* 423 * Disallow forms other than dotted quad: the treatment that inet_addr() 424 * gives to forms with less than four components is inconsistent with the 425 * access control language. John P. Rouillard <rouilj@cs.umb.edu>. 426 */ 427 428 if ((addr = dot_quad_addr(string)) == INADDR_NONE) 429 return (NO); 430 if ((net = dot_quad_addr(net_tok)) == INADDR_NONE 431 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) { 432 #ifndef INET6 433 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok); 434 #endif 435 return (NO); /* not tcpd_jump() */ 436 } 437 return ((addr & mask) == net); 438 } 439 440 #ifdef INET6 441 static int masked_match6(net_tok, mask_tok, string) 442 char *net_tok; 443 char *mask_tok; 444 char *string; 445 { 446 struct addrinfo hints, *res; 447 struct sockaddr_in6 net, addr; 448 u_int32_t mask; 449 int len, mask_len, i = 0; 450 char ch; 451 452 memset(&hints, 0, sizeof(hints)); 453 hints.ai_family = AF_INET6; 454 hints.ai_socktype = SOCK_STREAM; 455 hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST; 456 if (getaddrinfo(string, NULL, &hints, &res) != 0) 457 return NO; 458 memcpy(&addr, res->ai_addr, sizeof(addr)); 459 freeaddrinfo(res); 460 461 if (IN6_IS_ADDR_V4MAPPED(&addr.sin6_addr)) { 462 if ((*(u_int32_t *)&net.sin6_addr.s6_addr[12] = dot_quad_addr(net_tok)) == INADDR_NONE 463 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) 464 return (NO); 465 return ((*(u_int32_t *)&addr.sin6_addr.s6_addr[12] & mask) == *(u_int32_t *)&net.sin6_addr.s6_addr[12]); 466 } 467 468 /* match IPv6 address against netnumber/prefixlen */ 469 len = strlen(net_tok); 470 if (*net_tok != '[' || net_tok[len - 1] != ']') 471 return NO; 472 ch = net_tok[len - 1]; 473 net_tok[len - 1] = '\0'; 474 if (getaddrinfo(net_tok + 1, NULL, &hints, &res) != 0) { 475 net_tok[len - 1] = ch; 476 return NO; 477 } 478 memcpy(&net, res->ai_addr, sizeof(net)); 479 freeaddrinfo(res); 480 net_tok[len - 1] = ch; 481 if ((mask_len = atoi(mask_tok)) < 0 || mask_len > 128) 482 return NO; 483 484 if (net.sin6_scope_id != 0 && addr.sin6_scope_id != net.sin6_scope_id) 485 return NO; 486 while (mask_len > 0) { 487 if (mask_len < 32) { 488 mask = htonl(~(0xffffffff >> mask_len)); 489 if ((*(u_int32_t *)&addr.sin6_addr.s6_addr[i] & mask) != (*(u_int32_t *)&net.sin6_addr.s6_addr[i] & mask)) 490 return NO; 491 break; 492 } 493 if (*(u_int32_t *)&addr.sin6_addr.s6_addr[i] != *(u_int32_t *)&net.sin6_addr.s6_addr[i]) 494 return NO; 495 i += 4; 496 mask_len -= 32; 497 } 498 return YES; 499 } 500 #endif /* INET6 */ 501