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(char *table, struct request_info *request); 91 static int list_match(char *list, struct request_info *request, 92 int (*match_fn)(char *, struct request_info *)); 93 static int server_match(char *tok, struct request_info *request); 94 static int client_match(char *tok, struct request_info *request); 95 static int host_match(char *tok, struct host_info *host); 96 static int string_match(char *tok, char *string); 97 static int masked_match(char *net_tok, char *mask_tok, char *string); 98 #ifdef INET6 99 static int masked_match4(char *net_tok, char *mask_tok, char *string); 100 static int masked_match6(char *net_tok, char *mask_tok, char *string); 101 #endif 102 103 /* Size of logical line buffer. */ 104 105 #define BUFLEN 2048 106 107 /* definition to be used from workarounds.c */ 108 #ifdef NETGROUP 109 int yp_get_default_domain(char **); 110 #endif 111 112 /* hosts_access - host access control facility */ 113 114 int hosts_access(request) 115 struct request_info *request; 116 { 117 int verdict; 118 119 /* 120 * If the (daemon, client) pair is matched by an entry in the file 121 * /etc/hosts.allow, access is granted. Otherwise, if the (daemon, 122 * client) pair is matched by an entry in the file /etc/hosts.deny, 123 * access is denied. Otherwise, access is granted. A non-existent 124 * access-control file is treated as an empty file. 125 * 126 * After a rule has been matched, the optional language extensions may 127 * decide to grant or refuse service anyway. Or, while a rule is being 128 * processed, a serious error is found, and it seems better to play safe 129 * and deny service. All this is done by jumping back into the 130 * hosts_access() routine, bypassing the regular return from the 131 * table_match() function calls below. 132 */ 133 134 if (resident <= 0) 135 resident++; 136 verdict = setjmp(tcpd_buf); 137 if (verdict != 0) 138 return (verdict == AC_PERMIT); 139 if (table_match(hosts_allow_table, request)) 140 return (YES); 141 if (table_match(hosts_deny_table, request)) 142 return (NO); 143 return (YES); 144 } 145 146 /* table_match - match table entries with (daemon, client) pair */ 147 148 static int table_match(table, request) 149 char *table; 150 struct request_info *request; 151 { 152 FILE *fp; 153 char sv_list[BUFLEN]; /* becomes list of daemons */ 154 char *cl_list; /* becomes list of clients */ 155 char *sh_cmd; /* becomes optional shell command */ 156 int match = NO; 157 struct tcpd_context saved_context; 158 char *cp; 159 160 saved_context = tcpd_context; /* stupid compilers */ 161 162 /* 163 * Between the fopen() and fclose() calls, avoid jumps that may cause 164 * file descriptor leaks. 165 */ 166 167 if ((fp = fopen(table, "r")) != 0) { 168 tcpd_context.file = table; 169 tcpd_context.line = 0; 170 while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) { 171 if (sv_list[strlen(sv_list) - 1] != '\n') { 172 tcpd_warn("missing newline or line too long"); 173 continue; 174 } 175 /* Ignore anything after unescaped # character */ 176 for (cp = strchr(sv_list, '#'); cp != NULL;) { 177 if (cp > sv_list && cp[-1] == '\\') { 178 cp = strchr(cp + 1, '#'); 179 continue; 180 } 181 *cp = '\0'; 182 break; 183 } 184 if (sv_list[strspn(sv_list, " \t\r\n")] == 0) 185 continue; 186 if ((cl_list = split_at(sv_list, ':')) == 0) { 187 tcpd_warn("missing \":\" separator"); 188 continue; 189 } 190 sh_cmd = split_at(cl_list, ':'); 191 match = list_match(sv_list, request, server_match) 192 && list_match(cl_list, request, client_match); 193 } 194 (void) fclose(fp); 195 } else if (errno != ENOENT) { 196 tcpd_warn("cannot open %s: %m", table); 197 } 198 if (match) { 199 if (hosts_access_verbose > 1) 200 syslog(LOG_DEBUG, "matched: %s line %d", 201 tcpd_context.file, tcpd_context.line); 202 if (sh_cmd) { 203 #ifdef PROCESS_OPTIONS 204 process_options(sh_cmd, request); 205 #else 206 char cmd[BUFSIZ]; 207 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request)); 208 #endif 209 } 210 } 211 tcpd_context = saved_context; 212 return (match); 213 } 214 215 /* list_match - match a request against a list of patterns with exceptions */ 216 217 static int list_match(char *list, struct request_info *request, 218 int (*match_fn)(char *, struct request_info *)) 219 { 220 char *tok; 221 222 /* 223 * Process tokens one at a time. We have exhausted all possible matches 224 * when we reach an "EXCEPT" token or the end of the list. If we do find 225 * a match, look for an "EXCEPT" list and recurse to determine whether 226 * the match is affected by any exceptions. 227 */ 228 229 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) { 230 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */ 231 return (NO); 232 if (match_fn(tok, request)) { /* YES: look for exceptions */ 233 while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT")) 234 /* VOID */ ; 235 return (tok == 0 || list_match((char *) 0, request, match_fn) == 0); 236 } 237 } 238 return (NO); 239 } 240 241 /* server_match - match server information */ 242 243 static int server_match(tok, request) 244 char *tok; 245 struct request_info *request; 246 { 247 char *host; 248 249 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */ 250 return (string_match(tok, eval_daemon(request))); 251 } else { /* daemon@host */ 252 return (string_match(tok, eval_daemon(request)) 253 && host_match(host, request->server)); 254 } 255 } 256 257 /* client_match - match client information */ 258 259 static int client_match(tok, request) 260 char *tok; 261 struct request_info *request; 262 { 263 char *host; 264 265 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */ 266 return (host_match(tok, request->client)); 267 } else { /* user@host */ 268 return (host_match(host, request->client) 269 && string_match(tok, eval_user(request))); 270 } 271 } 272 273 /* hostfile_match - look up host patterns from file */ 274 275 static int hostfile_match(path, host) 276 char *path; 277 struct host_info *host; 278 { 279 char tok[BUFSIZ]; 280 int match = NO; 281 FILE *fp; 282 283 if ((fp = fopen(path, "r")) != 0) { 284 while (fscanf(fp, "%s", tok) == 1 && !(match = host_match(tok, host))) 285 /* void */ ; 286 fclose(fp); 287 } else if (errno != ENOENT) { 288 tcpd_warn("open %s: %m", path); 289 } 290 return (match); 291 } 292 293 /* host_match - match host name and/or address against pattern */ 294 295 static int host_match(tok, host) 296 char *tok; 297 struct host_info *host; 298 { 299 char *mask; 300 301 /* 302 * This code looks a little hairy because we want to avoid unnecessary 303 * hostname lookups. 304 * 305 * The KNOWN pattern requires that both address AND name be known; some 306 * patterns are specific to host names or to host addresses; all other 307 * patterns are satisfied when either the address OR the name match. 308 */ 309 310 if (tok[0] == '@') { /* netgroup: look it up */ 311 #ifdef NETGROUP 312 static char *mydomain = 0; 313 if (mydomain == 0) 314 yp_get_default_domain(&mydomain); 315 return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain)); 316 #else 317 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */ 318 return (NO); 319 #endif 320 } else if (tok[0] == '/') { /* /file hack */ 321 return (hostfile_match(tok, host)); 322 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */ 323 char *name = eval_hostname(host); 324 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name)); 325 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */ 326 char *name = eval_hostname(host); 327 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name)); 328 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */ 329 return (masked_match(tok, mask, eval_hostaddr(host))); 330 } else { /* anything else */ 331 return (string_match(tok, eval_hostaddr(host)) 332 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host)))); 333 } 334 } 335 336 /* string_match - match string against pattern */ 337 338 static int string_match(tok, string) 339 char *tok; 340 char *string; 341 { 342 int n; 343 344 #ifdef INET6 345 /* convert IPv4 mapped IPv6 address to IPv4 address */ 346 if (STRN_EQ(string, "::ffff:", 7) 347 && dot_quad_addr(string + 7) != INADDR_NONE) { 348 string += 7; 349 } 350 #endif 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 #ifdef INET6 362 struct addrinfo hints, *res; 363 struct sockaddr_in6 pat, addr; 364 int len, ret; 365 char ch; 366 367 len = strlen(tok); 368 if (*tok == '[' && tok[len - 1] == ']') { 369 ch = tok[len - 1]; 370 tok[len - 1] = '\0'; 371 memset(&hints, 0, sizeof(hints)); 372 hints.ai_family = AF_INET6; 373 hints.ai_socktype = SOCK_STREAM; 374 hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST; 375 if ((ret = getaddrinfo(tok + 1, NULL, &hints, &res)) == 0) { 376 memcpy(&pat, res->ai_addr, sizeof(pat)); 377 freeaddrinfo(res); 378 } 379 tok[len - 1] = ch; 380 if (ret != 0 || getaddrinfo(string, NULL, &hints, &res) != 0) 381 return NO; 382 memcpy(&addr, res->ai_addr, sizeof(addr)); 383 freeaddrinfo(res); 384 if (pat.sin6_scope_id != 0 && 385 addr.sin6_scope_id != pat.sin6_scope_id) 386 return NO; 387 return (!memcmp(&pat.sin6_addr, &addr.sin6_addr, 388 sizeof(struct in6_addr))); 389 return (ret); 390 } 391 #endif 392 return (STR_EQ(tok, string)); 393 } 394 } 395 396 /* masked_match - match address against netnumber/netmask */ 397 398 #ifdef INET6 399 static int masked_match(net_tok, mask_tok, string) 400 char *net_tok; 401 char *mask_tok; 402 char *string; 403 { 404 return (masked_match4(net_tok, mask_tok, string) || 405 masked_match6(net_tok, mask_tok, string)); 406 } 407 408 static int masked_match4(net_tok, mask_tok, string) 409 #else 410 static int masked_match(net_tok, mask_tok, string) 411 #endif 412 char *net_tok; 413 char *mask_tok; 414 char *string; 415 { 416 #ifdef INET6 417 u_int32_t net; 418 u_int32_t mask; 419 u_int32_t addr; 420 #else 421 unsigned long net; 422 unsigned long mask; 423 unsigned long addr; 424 #endif 425 426 /* 427 * Disallow forms other than dotted quad: the treatment that inet_addr() 428 * gives to forms with less than four components is inconsistent with the 429 * access control language. John P. Rouillard <rouilj@cs.umb.edu>. 430 */ 431 432 if ((addr = dot_quad_addr(string)) == INADDR_NONE) 433 return (NO); 434 if ((net = dot_quad_addr(net_tok)) == INADDR_NONE 435 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) { 436 #ifndef INET6 437 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok); 438 #endif 439 return (NO); /* not tcpd_jump() */ 440 } 441 return ((addr & mask) == net); 442 } 443 444 #ifdef INET6 445 static int masked_match6(net_tok, mask_tok, string) 446 char *net_tok; 447 char *mask_tok; 448 char *string; 449 { 450 struct addrinfo hints, *res; 451 struct sockaddr_in6 net, addr; 452 u_int32_t mask; 453 int len, mask_len, i = 0; 454 char ch; 455 456 memset(&hints, 0, sizeof(hints)); 457 hints.ai_family = AF_INET6; 458 hints.ai_socktype = SOCK_STREAM; 459 hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST; 460 if (getaddrinfo(string, NULL, &hints, &res) != 0) 461 return NO; 462 memcpy(&addr, res->ai_addr, sizeof(addr)); 463 freeaddrinfo(res); 464 465 if (IN6_IS_ADDR_V4MAPPED(&addr.sin6_addr)) { 466 if ((*(u_int32_t *)&net.sin6_addr.s6_addr[12] = dot_quad_addr(net_tok)) == INADDR_NONE 467 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) 468 return (NO); 469 return ((*(u_int32_t *)&addr.sin6_addr.s6_addr[12] & mask) == *(u_int32_t *)&net.sin6_addr.s6_addr[12]); 470 } 471 472 /* match IPv6 address against netnumber/prefixlen */ 473 len = strlen(net_tok); 474 if (*net_tok != '[' || net_tok[len - 1] != ']') 475 return NO; 476 ch = net_tok[len - 1]; 477 net_tok[len - 1] = '\0'; 478 if (getaddrinfo(net_tok + 1, NULL, &hints, &res) != 0) { 479 net_tok[len - 1] = ch; 480 return NO; 481 } 482 memcpy(&net, res->ai_addr, sizeof(net)); 483 freeaddrinfo(res); 484 net_tok[len - 1] = ch; 485 if ((mask_len = atoi(mask_tok)) < 0 || mask_len > 128) 486 return NO; 487 488 if (net.sin6_scope_id != 0 && addr.sin6_scope_id != net.sin6_scope_id) 489 return NO; 490 while (mask_len > 0) { 491 if (mask_len < 32) { 492 mask = htonl(~(0xffffffff >> mask_len)); 493 if ((*(u_int32_t *)&addr.sin6_addr.s6_addr[i] & mask) != (*(u_int32_t *)&net.sin6_addr.s6_addr[i] & mask)) 494 return NO; 495 break; 496 } 497 if (*(u_int32_t *)&addr.sin6_addr.s6_addr[i] != *(u_int32_t *)&net.sin6_addr.s6_addr[i]) 498 return NO; 499 i += 4; 500 mask_len -= 32; 501 } 502 return YES; 503 } 504 #endif /* INET6 */ 505