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 48 extern char *fgets(); 49 extern int errno; 50 51 #ifndef INADDR_NONE 52 #define INADDR_NONE (-1) /* XXX should be 0xffffffff */ 53 #endif 54 55 /* Local stuff. */ 56 57 #include "tcpd.h" 58 59 /* Error handling. */ 60 61 extern jmp_buf tcpd_buf; 62 63 /* Delimiters for lists of daemons or clients. */ 64 65 static char sep[] = ", \t\r\n"; 66 67 /* Constants to be used in assignments only, not in comparisons... */ 68 69 #define YES 1 70 #define NO 0 71 72 /* 73 * These variables are globally visible so that they can be redirected in 74 * verification mode. 75 */ 76 77 char *hosts_allow_table = HOSTS_ALLOW; 78 char *hosts_deny_table = HOSTS_DENY; 79 int hosts_access_verbose = 0; 80 81 /* 82 * In a long-running process, we are not at liberty to just go away. 83 */ 84 85 int resident = (-1); /* -1, 0: unknown; +1: yes */ 86 87 /* Forward declarations. */ 88 89 static int table_match(); 90 static int list_match(); 91 static int server_match(); 92 static int client_match(); 93 static int host_match(); 94 static int string_match(); 95 static int masked_match(); 96 #ifdef INET6 97 static int masked_match4(); 98 static int masked_match6(); 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; /* becomes optional shell command */ 149 int match = NO; 150 struct tcpd_context saved_context; 151 char *cp; 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 /* Ignore anything after unescaped # character */ 169 for (cp = strchr(sv_list, '#'); cp != NULL;) { 170 if (cp > sv_list && cp[-1] == '\\') { 171 cp = strchr(cp + 1, '#'); 172 continue; 173 } 174 *cp = '\0'; 175 break; 176 } 177 if (sv_list[strspn(sv_list, " \t\r\n")] == 0) 178 continue; 179 if ((cl_list = split_at(sv_list, ':')) == 0) { 180 tcpd_warn("missing \":\" separator"); 181 continue; 182 } 183 sh_cmd = split_at(cl_list, ':'); 184 match = list_match(sv_list, request, server_match) 185 && list_match(cl_list, request, client_match); 186 } 187 (void) fclose(fp); 188 } else if (errno != ENOENT) { 189 tcpd_warn("cannot open %s: %m", table); 190 } 191 if (match) { 192 if (hosts_access_verbose > 1) 193 syslog(LOG_DEBUG, "matched: %s line %d", 194 tcpd_context.file, tcpd_context.line); 195 if (sh_cmd) { 196 #ifdef PROCESS_OPTIONS 197 process_options(sh_cmd, request); 198 #else 199 char cmd[BUFSIZ]; 200 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request)); 201 #endif 202 } 203 } 204 tcpd_context = saved_context; 205 return (match); 206 } 207 208 /* list_match - match a request against a list of patterns with exceptions */ 209 210 static int list_match(list, request, match_fn) 211 char *list; 212 struct request_info *request; 213 int (*match_fn) (); 214 { 215 char *tok; 216 217 /* 218 * Process tokens one at a time. We have exhausted all possible matches 219 * when we reach an "EXCEPT" token or the end of the list. If we do find 220 * a match, look for an "EXCEPT" list and recurse to determine whether 221 * the match is affected by any exceptions. 222 */ 223 224 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) { 225 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */ 226 return (NO); 227 if (match_fn(tok, request)) { /* YES: look for exceptions */ 228 while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT")) 229 /* VOID */ ; 230 return (tok == 0 || list_match((char *) 0, request, match_fn) == 0); 231 } 232 } 233 return (NO); 234 } 235 236 /* server_match - match server information */ 237 238 static int server_match(tok, request) 239 char *tok; 240 struct request_info *request; 241 { 242 char *host; 243 244 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */ 245 return (string_match(tok, eval_daemon(request))); 246 } else { /* daemon@host */ 247 return (string_match(tok, eval_daemon(request)) 248 && host_match(host, request->server)); 249 } 250 } 251 252 /* client_match - match client information */ 253 254 static int client_match(tok, request) 255 char *tok; 256 struct request_info *request; 257 { 258 char *host; 259 260 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */ 261 return (host_match(tok, request->client)); 262 } else { /* user@host */ 263 return (host_match(host, request->client) 264 && string_match(tok, eval_user(request))); 265 } 266 } 267 268 /* hostfile_match - look up host patterns from file */ 269 270 static int hostfile_match(path, host) 271 char *path; 272 struct hosts_info *host; 273 { 274 char tok[BUFSIZ]; 275 int match = NO; 276 FILE *fp; 277 278 if ((fp = fopen(path, "r")) != 0) { 279 while (fscanf(fp, "%s", tok) == 1 && !(match = host_match(tok, host))) 280 /* void */ ; 281 fclose(fp); 282 } else if (errno != ENOENT) { 283 tcpd_warn("open %s: %m", path); 284 } 285 return (match); 286 } 287 288 /* host_match - match host name and/or address against pattern */ 289 290 static int host_match(tok, host) 291 char *tok; 292 struct host_info *host; 293 { 294 char *mask; 295 296 /* 297 * This code looks a little hairy because we want to avoid unnecessary 298 * hostname lookups. 299 * 300 * The KNOWN pattern requires that both address AND name be known; some 301 * patterns are specific to host names or to host addresses; all other 302 * patterns are satisfied when either the address OR the name match. 303 */ 304 305 if (tok[0] == '@') { /* netgroup: look it up */ 306 #ifdef NETGROUP 307 static char *mydomain = 0; 308 if (mydomain == 0) 309 yp_get_default_domain(&mydomain); 310 return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain)); 311 #else 312 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */ 313 return (NO); 314 #endif 315 } else if (tok[0] == '/') { /* /file hack */ 316 return (hostfile_match(tok, host)); 317 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */ 318 char *name = eval_hostname(host); 319 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name)); 320 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */ 321 char *name = eval_hostname(host); 322 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name)); 323 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */ 324 return (masked_match(tok, mask, eval_hostaddr(host))); 325 } else { /* anything else */ 326 return (string_match(tok, eval_hostaddr(host)) 327 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host)))); 328 } 329 } 330 331 /* string_match - match string against pattern */ 332 333 static int string_match(tok, string) 334 char *tok; 335 char *string; 336 { 337 int n; 338 339 #ifdef INET6 340 /* convert IPv4 mapped IPv6 address to IPv4 address */ 341 if (STRN_EQ(string, "::ffff:", 7) 342 && dot_quad_addr(string + 7) != INADDR_NONE) { 343 string += 7; 344 } 345 #endif 346 if (tok[0] == '.') { /* suffix */ 347 n = strlen(string) - strlen(tok); 348 return (n > 0 && STR_EQ(tok, string + n)); 349 } else if (STR_EQ(tok, "ALL")) { /* all: match any */ 350 return (YES); 351 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */ 352 return (STR_NE(string, unknown)); 353 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */ 354 return (STRN_EQ(tok, string, n)); 355 } else { /* exact match */ 356 #ifdef INET6 357 struct addrinfo hints, *res; 358 struct sockaddr_in6 pat, addr; 359 int len, ret; 360 char ch; 361 362 len = strlen(tok); 363 if (*tok == '[' && tok[len - 1] == ']') { 364 ch = tok[len - 1]; 365 tok[len - 1] = '\0'; 366 memset(&hints, 0, sizeof(hints)); 367 hints.ai_family = AF_INET6; 368 hints.ai_socktype = SOCK_STREAM; 369 hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST; 370 if ((ret = getaddrinfo(tok + 1, NULL, &hints, &res)) == 0) { 371 memcpy(&pat, res->ai_addr, sizeof(pat)); 372 freeaddrinfo(res); 373 } 374 tok[len - 1] = ch; 375 if (ret != 0 || getaddrinfo(string, NULL, &hints, &res) != 0) 376 return NO; 377 memcpy(&addr, res->ai_addr, sizeof(addr)); 378 freeaddrinfo(res); 379 if (pat.sin6_scope_id != 0 && 380 addr.sin6_scope_id != pat.sin6_scope_id) 381 return NO; 382 return (!memcmp(&pat.sin6_addr, &addr.sin6_addr, 383 sizeof(struct in6_addr))); 384 return (ret); 385 } 386 #endif 387 return (STR_EQ(tok, string)); 388 } 389 } 390 391 /* masked_match - match address against netnumber/netmask */ 392 393 #ifdef INET6 394 static int masked_match(net_tok, mask_tok, string) 395 char *net_tok; 396 char *mask_tok; 397 char *string; 398 { 399 return (masked_match4(net_tok, mask_tok, string) || 400 masked_match6(net_tok, mask_tok, string)); 401 } 402 403 static int masked_match4(net_tok, mask_tok, string) 404 #else 405 static int masked_match(net_tok, mask_tok, string) 406 #endif 407 char *net_tok; 408 char *mask_tok; 409 char *string; 410 { 411 #ifdef INET6 412 u_int32_t net; 413 u_int32_t mask; 414 u_int32_t addr; 415 #else 416 unsigned long net; 417 unsigned long mask; 418 unsigned long addr; 419 #endif 420 421 /* 422 * Disallow forms other than dotted quad: the treatment that inet_addr() 423 * gives to forms with less than four components is inconsistent with the 424 * access control language. John P. Rouillard <rouilj@cs.umb.edu>. 425 */ 426 427 if ((addr = dot_quad_addr(string)) == INADDR_NONE) 428 return (NO); 429 if ((net = dot_quad_addr(net_tok)) == INADDR_NONE 430 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) { 431 #ifndef INET6 432 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok); 433 #endif 434 return (NO); /* not tcpd_jump() */ 435 } 436 return ((addr & mask) == net); 437 } 438 439 #ifdef INET6 440 static int masked_match6(net_tok, mask_tok, string) 441 char *net_tok; 442 char *mask_tok; 443 char *string; 444 { 445 struct addrinfo hints, *res; 446 struct sockaddr_in6 net, addr; 447 u_int32_t mask; 448 int len, mask_len, i = 0; 449 char ch; 450 451 memset(&hints, 0, sizeof(hints)); 452 hints.ai_family = AF_INET6; 453 hints.ai_socktype = SOCK_STREAM; 454 hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST; 455 if (getaddrinfo(string, NULL, &hints, &res) != 0) 456 return NO; 457 memcpy(&addr, res->ai_addr, sizeof(addr)); 458 freeaddrinfo(res); 459 460 if (IN6_IS_ADDR_V4MAPPED(&addr.sin6_addr)) { 461 if ((*(u_int32_t *)&net.sin6_addr.s6_addr[12] = dot_quad_addr(net_tok)) == INADDR_NONE 462 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) 463 return (NO); 464 return ((*(u_int32_t *)&addr.sin6_addr.s6_addr[12] & mask) == *(u_int32_t *)&net.sin6_addr.s6_addr[12]); 465 } 466 467 /* match IPv6 address against netnumber/prefixlen */ 468 len = strlen(net_tok); 469 if (*net_tok != '[' || net_tok[len - 1] != ']') 470 return NO; 471 ch = net_tok[len - 1]; 472 net_tok[len - 1] = '\0'; 473 if (getaddrinfo(net_tok + 1, NULL, &hints, &res) != 0) { 474 net_tok[len - 1] = ch; 475 return NO; 476 } 477 memcpy(&net, res->ai_addr, sizeof(net)); 478 freeaddrinfo(res); 479 net_tok[len - 1] = ch; 480 if ((mask_len = atoi(mask_tok)) < 0 || mask_len > 128) 481 return NO; 482 483 if (net.sin6_scope_id != 0 && addr.sin6_scope_id != net.sin6_scope_id) 484 return NO; 485 while (mask_len > 0) { 486 if (mask_len < 32) { 487 mask = htonl(~(0xffffffff >> mask_len)); 488 if ((*(u_int32_t *)&addr.sin6_addr.s6_addr[i] & mask) != (*(u_int32_t *)&net.sin6_addr.s6_addr[i] & mask)) 489 return NO; 490 break; 491 } 492 if (*(u_int32_t *)&addr.sin6_addr.s6_addr[i] != *(u_int32_t *)&net.sin6_addr.s6_addr[i]) 493 return NO; 494 i += 4; 495 mask_len -= 32; 496 } 497 return YES; 498 } 499 #endif /* INET6 */ 500