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 #ifndef INADDR_NONE 50 #define INADDR_NONE (-1) /* XXX should be 0xffffffff */ 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(char *table, struct request_info *request); 88 static int list_match(char *list, struct request_info *request, 89 int (*match_fn)(char *, struct request_info *)); 90 static int server_match(char *tok, struct request_info *request); 91 static int client_match(char *tok, struct request_info *request); 92 static int host_match(char *tok, struct host_info *host); 93 static int string_match(char *tok, char *string); 94 static int masked_match(char *net_tok, char *mask_tok, char *string); 95 #ifdef INET6 96 static int masked_match4(char *net_tok, char *mask_tok, char *string); 97 static int masked_match6(char *net_tok, char *mask_tok, char *string); 98 #endif 99 100 /* Size of logical line buffer. */ 101 102 #define BUFLEN 2048 103 104 /* definition to be used from workarounds.c */ 105 #ifdef NETGROUP 106 int yp_get_default_domain(char **); 107 #endif 108 109 /* hosts_access - host access control facility */ 110 111 int hosts_access(request) 112 struct request_info *request; 113 { 114 int verdict; 115 116 /* 117 * If the (daemon, client) pair is matched by an entry in the file 118 * /etc/hosts.allow, access is granted. Otherwise, if the (daemon, 119 * client) pair is matched by an entry in the file /etc/hosts.deny, 120 * access is denied. Otherwise, access is granted. A non-existent 121 * access-control file is treated as an empty file. 122 * 123 * After a rule has been matched, the optional language extensions may 124 * decide to grant or refuse service anyway. Or, while a rule is being 125 * processed, a serious error is found, and it seems better to play safe 126 * and deny service. All this is done by jumping back into the 127 * hosts_access() routine, bypassing the regular return from the 128 * table_match() function calls below. 129 */ 130 131 if (resident <= 0) 132 resident++; 133 verdict = setjmp(tcpd_buf); 134 if (verdict != 0) 135 return (verdict == AC_PERMIT); 136 if (table_match(hosts_allow_table, request)) 137 return (YES); 138 if (table_match(hosts_deny_table, request)) 139 return (NO); 140 return (YES); 141 } 142 143 /* table_match - match table entries with (daemon, client) pair */ 144 145 static int table_match(table, request) 146 char *table; 147 struct request_info *request; 148 { 149 FILE *fp; 150 char sv_list[BUFLEN]; /* becomes list of daemons */ 151 char *cl_list; /* becomes list of clients */ 152 char *sh_cmd; /* becomes optional shell command */ 153 int match = NO; 154 struct tcpd_context saved_context; 155 char *cp; 156 157 saved_context = tcpd_context; /* stupid compilers */ 158 159 /* 160 * Between the fopen() and fclose() calls, avoid jumps that may cause 161 * file descriptor leaks. 162 */ 163 164 if ((fp = fopen(table, "r")) != 0) { 165 tcpd_context.file = table; 166 tcpd_context.line = 0; 167 while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) { 168 if (sv_list[strlen(sv_list) - 1] != '\n') { 169 tcpd_warn("missing newline or line too long"); 170 continue; 171 } 172 /* Ignore anything after unescaped # character */ 173 for (cp = strchr(sv_list, '#'); cp != NULL;) { 174 if (cp > sv_list && cp[-1] == '\\') { 175 cp = strchr(cp + 1, '#'); 176 continue; 177 } 178 *cp = '\0'; 179 break; 180 } 181 if (sv_list[strspn(sv_list, " \t\r\n")] == 0) 182 continue; 183 if ((cl_list = split_at(sv_list, ':')) == 0) { 184 tcpd_warn("missing \":\" separator"); 185 continue; 186 } 187 sh_cmd = split_at(cl_list, ':'); 188 match = list_match(sv_list, request, server_match) 189 && list_match(cl_list, request, client_match); 190 } 191 (void) fclose(fp); 192 } else if (errno != ENOENT) { 193 tcpd_warn("cannot open %s: %m", table); 194 } 195 if (match) { 196 if (hosts_access_verbose > 1) 197 syslog(LOG_DEBUG, "matched: %s line %d", 198 tcpd_context.file, tcpd_context.line); 199 if (sh_cmd) { 200 #ifdef PROCESS_OPTIONS 201 process_options(sh_cmd, request); 202 #else 203 char cmd[BUFSIZ]; 204 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request)); 205 #endif 206 } 207 } 208 tcpd_context = saved_context; 209 return (match); 210 } 211 212 /* list_match - match a request against a list of patterns with exceptions */ 213 214 static int list_match(char *list, struct request_info *request, 215 int (*match_fn)(char *, struct request_info *)) 216 { 217 char *tok; 218 219 /* 220 * Process tokens one at a time. We have exhausted all possible matches 221 * when we reach an "EXCEPT" token or the end of the list. If we do find 222 * a match, look for an "EXCEPT" list and recurse to determine whether 223 * the match is affected by any exceptions. 224 */ 225 226 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) { 227 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */ 228 return (NO); 229 if (match_fn(tok, request)) { /* YES: look for exceptions */ 230 while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT")) 231 /* VOID */ ; 232 return (tok == 0 || list_match((char *) 0, request, match_fn) == 0); 233 } 234 } 235 return (NO); 236 } 237 238 /* server_match - match server information */ 239 240 static int server_match(tok, request) 241 char *tok; 242 struct request_info *request; 243 { 244 char *host; 245 246 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */ 247 return (string_match(tok, eval_daemon(request))); 248 } else { /* daemon@host */ 249 return (string_match(tok, eval_daemon(request)) 250 && host_match(host, request->server)); 251 } 252 } 253 254 /* client_match - match client information */ 255 256 static int client_match(tok, request) 257 char *tok; 258 struct request_info *request; 259 { 260 char *host; 261 262 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */ 263 return (host_match(tok, request->client)); 264 } else { /* user@host */ 265 return (host_match(host, request->client) 266 && string_match(tok, eval_user(request))); 267 } 268 } 269 270 /* hostfile_match - look up host patterns from file */ 271 272 static int hostfile_match(path, host) 273 char *path; 274 struct host_info *host; 275 { 276 char tok[BUFSIZ]; 277 int match = NO; 278 FILE *fp; 279 280 if ((fp = fopen(path, "r")) != 0) { 281 while (fscanf(fp, "%s", tok) == 1 && !(match = host_match(tok, host))) 282 /* void */ ; 283 fclose(fp); 284 } else if (errno != ENOENT) { 285 tcpd_warn("open %s: %m", path); 286 } 287 return (match); 288 } 289 290 /* host_match - match host name and/or address against pattern */ 291 292 static int host_match(tok, host) 293 char *tok; 294 struct host_info *host; 295 { 296 char *mask; 297 298 /* 299 * This code looks a little hairy because we want to avoid unnecessary 300 * hostname lookups. 301 * 302 * The KNOWN pattern requires that both address AND name be known; some 303 * patterns are specific to host names or to host addresses; all other 304 * patterns are satisfied when either the address OR the name match. 305 */ 306 307 if (tok[0] == '@') { /* netgroup: look it up */ 308 #ifdef NETGROUP 309 static char *mydomain = 0; 310 if (mydomain == 0) 311 yp_get_default_domain(&mydomain); 312 return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain)); 313 #else 314 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */ 315 return (NO); 316 #endif 317 } else if (tok[0] == '/') { /* /file hack */ 318 return (hostfile_match(tok, host)); 319 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */ 320 char *name = eval_hostname(host); 321 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name)); 322 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */ 323 char *name = eval_hostname(host); 324 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name)); 325 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */ 326 return (masked_match(tok, mask, eval_hostaddr(host))); 327 } else { /* anything else */ 328 return (string_match(tok, eval_hostaddr(host)) 329 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host)))); 330 } 331 } 332 333 /* string_match - match string against pattern */ 334 335 static int string_match(tok, string) 336 char *tok; 337 char *string; 338 { 339 int n; 340 341 #ifdef INET6 342 /* convert IPv4 mapped IPv6 address to IPv4 address */ 343 if (STRN_EQ(string, "::ffff:", 7) 344 && dot_quad_addr(string + 7) != INADDR_NONE) { 345 string += 7; 346 } 347 #endif 348 if (tok[0] == '.') { /* suffix */ 349 n = strlen(string) - strlen(tok); 350 return (n > 0 && STR_EQ(tok, string + n)); 351 } else if (STR_EQ(tok, "ALL")) { /* all: match any */ 352 return (YES); 353 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */ 354 return (STR_NE(string, unknown)); 355 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */ 356 return (STRN_EQ(tok, string, n)); 357 } else { /* exact match */ 358 #ifdef INET6 359 struct addrinfo hints, *res; 360 struct sockaddr_in6 pat, addr; 361 int len, ret; 362 char ch; 363 364 len = strlen(tok); 365 if (*tok == '[' && tok[len - 1] == ']') { 366 ch = tok[len - 1]; 367 tok[len - 1] = '\0'; 368 memset(&hints, 0, sizeof(hints)); 369 hints.ai_family = AF_INET6; 370 hints.ai_socktype = SOCK_STREAM; 371 hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST; 372 if ((ret = getaddrinfo(tok + 1, NULL, &hints, &res)) == 0) { 373 memcpy(&pat, res->ai_addr, sizeof(pat)); 374 freeaddrinfo(res); 375 } 376 tok[len - 1] = ch; 377 if (ret != 0 || getaddrinfo(string, NULL, &hints, &res) != 0) 378 return NO; 379 memcpy(&addr, res->ai_addr, sizeof(addr)); 380 freeaddrinfo(res); 381 if (pat.sin6_scope_id != 0 && 382 addr.sin6_scope_id != pat.sin6_scope_id) 383 return NO; 384 return (!memcmp(&pat.sin6_addr, &addr.sin6_addr, 385 sizeof(struct in6_addr))); 386 return (ret); 387 } 388 #endif 389 return (STR_EQ(tok, string)); 390 } 391 } 392 393 /* masked_match - match address against netnumber/netmask */ 394 395 #ifdef INET6 396 static int masked_match(net_tok, mask_tok, string) 397 char *net_tok; 398 char *mask_tok; 399 char *string; 400 { 401 return (masked_match4(net_tok, mask_tok, string) || 402 masked_match6(net_tok, mask_tok, string)); 403 } 404 405 static int masked_match4(net_tok, mask_tok, string) 406 #else 407 static int masked_match(net_tok, mask_tok, string) 408 #endif 409 char *net_tok; 410 char *mask_tok; 411 char *string; 412 { 413 #ifdef INET6 414 u_int32_t net; 415 u_int32_t mask; 416 u_int32_t addr; 417 #else 418 unsigned long net; 419 unsigned long mask; 420 unsigned long addr; 421 #endif 422 423 /* 424 * Disallow forms other than dotted quad: the treatment that inet_addr() 425 * gives to forms with less than four components is inconsistent with the 426 * access control language. John P. Rouillard <rouilj@cs.umb.edu>. 427 */ 428 429 if ((addr = dot_quad_addr(string)) == INADDR_NONE) 430 return (NO); 431 if ((net = dot_quad_addr(net_tok)) == INADDR_NONE 432 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) { 433 #ifndef INET6 434 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok); 435 #endif 436 return (NO); /* not tcpd_jump() */ 437 } 438 return ((addr & mask) == net); 439 } 440 441 #ifdef INET6 442 static int masked_match6(net_tok, mask_tok, string) 443 char *net_tok; 444 char *mask_tok; 445 char *string; 446 { 447 struct addrinfo hints, *res; 448 struct sockaddr_in6 net, addr; 449 u_int32_t mask; 450 int len, mask_len, i = 0; 451 char ch; 452 453 memset(&hints, 0, sizeof(hints)); 454 hints.ai_family = AF_INET6; 455 hints.ai_socktype = SOCK_STREAM; 456 hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST; 457 if (getaddrinfo(string, NULL, &hints, &res) != 0) 458 return NO; 459 memcpy(&addr, res->ai_addr, sizeof(addr)); 460 freeaddrinfo(res); 461 462 if (IN6_IS_ADDR_V4MAPPED(&addr.sin6_addr)) { 463 if ((*(u_int32_t *)&net.sin6_addr.s6_addr[12] = dot_quad_addr(net_tok)) == INADDR_NONE 464 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) 465 return (NO); 466 return ((*(u_int32_t *)&addr.sin6_addr.s6_addr[12] & mask) == *(u_int32_t *)&net.sin6_addr.s6_addr[12]); 467 } 468 469 /* match IPv6 address against netnumber/prefixlen */ 470 len = strlen(net_tok); 471 if (*net_tok != '[' || net_tok[len - 1] != ']') 472 return NO; 473 ch = net_tok[len - 1]; 474 net_tok[len - 1] = '\0'; 475 if (getaddrinfo(net_tok + 1, NULL, &hints, &res) != 0) { 476 net_tok[len - 1] = ch; 477 return NO; 478 } 479 memcpy(&net, res->ai_addr, sizeof(net)); 480 freeaddrinfo(res); 481 net_tok[len - 1] = ch; 482 if ((mask_len = atoi(mask_tok)) < 0 || mask_len > 128) 483 return NO; 484 485 if (net.sin6_scope_id != 0 && addr.sin6_scope_id != net.sin6_scope_id) 486 return NO; 487 while (mask_len > 0) { 488 if (mask_len < 32) { 489 mask = htonl(~(0xffffffff >> mask_len)); 490 if ((*(u_int32_t *)&addr.sin6_addr.s6_addr[i] & mask) != (*(u_int32_t *)&net.sin6_addr.s6_addr[i] & mask)) 491 return NO; 492 break; 493 } 494 if (*(u_int32_t *)&addr.sin6_addr.s6_addr[i] != *(u_int32_t *)&net.sin6_addr.s6_addr[i]) 495 return NO; 496 i += 4; 497 mask_len -= 32; 498 } 499 return YES; 500 } 501 #endif /* INET6 */ 502