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 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(char *table, struct request_info *request); 90 static int list_match(char *list, struct request_info *request, 91 int (*match_fn)(char *, struct request_info *)); 92 static int server_match(char *tok, struct request_info *request); 93 static int client_match(char *tok, struct request_info *request); 94 static int host_match(char *tok, struct host_info *host); 95 static int string_match(char *tok, char *string); 96 static int masked_match(char *net_tok, char *mask_tok, char *string); 97 #ifdef INET6 98 static int masked_match4(char *net_tok, char *mask_tok, char *string); 99 static int masked_match6(char *net_tok, char *mask_tok, char *string); 100 #endif 101 102 /* Size of logical line buffer. */ 103 104 #define BUFLEN 2048 105 106 /* definition to be used from workarounds.c */ 107 #ifdef NETGROUP 108 int yp_get_default_domain(char **); 109 #endif 110 111 /* hosts_access - host access control facility */ 112 113 int hosts_access(request) 114 struct request_info *request; 115 { 116 int verdict; 117 118 /* 119 * If the (daemon, client) pair is matched by an entry in the file 120 * /etc/hosts.allow, access is granted. Otherwise, if the (daemon, 121 * client) pair is matched by an entry in the file /etc/hosts.deny, 122 * access is denied. Otherwise, access is granted. A non-existent 123 * access-control file is treated as an empty file. 124 * 125 * After a rule has been matched, the optional language extensions may 126 * decide to grant or refuse service anyway. Or, while a rule is being 127 * processed, a serious error is found, and it seems better to play safe 128 * and deny service. All this is done by jumping back into the 129 * hosts_access() routine, bypassing the regular return from the 130 * table_match() function calls below. 131 */ 132 133 if (resident <= 0) 134 resident++; 135 verdict = setjmp(tcpd_buf); 136 if (verdict != 0) 137 return (verdict == AC_PERMIT); 138 if (table_match(hosts_allow_table, request)) 139 return (YES); 140 if (table_match(hosts_deny_table, request)) 141 return (NO); 142 return (YES); 143 } 144 145 /* table_match - match table entries with (daemon, client) pair */ 146 147 static int table_match(table, request) 148 char *table; 149 struct request_info *request; 150 { 151 FILE *fp; 152 char sv_list[BUFLEN]; /* becomes list of daemons */ 153 char *cl_list; /* becomes list of clients */ 154 char *sh_cmd; /* becomes optional shell command */ 155 int match = NO; 156 struct tcpd_context saved_context; 157 char *cp; 158 159 saved_context = tcpd_context; /* stupid compilers */ 160 161 /* 162 * Between the fopen() and fclose() calls, avoid jumps that may cause 163 * file descriptor leaks. 164 */ 165 166 if ((fp = fopen(table, "r")) != 0) { 167 tcpd_context.file = table; 168 tcpd_context.line = 0; 169 while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) { 170 if (sv_list[strlen(sv_list) - 1] != '\n') { 171 tcpd_warn("missing newline or line too long"); 172 continue; 173 } 174 /* Ignore anything after unescaped # character */ 175 for (cp = strchr(sv_list, '#'); cp != NULL;) { 176 if (cp > sv_list && cp[-1] == '\\') { 177 cp = strchr(cp + 1, '#'); 178 continue; 179 } 180 *cp = '\0'; 181 break; 182 } 183 if (sv_list[strspn(sv_list, " \t\r\n")] == 0) 184 continue; 185 if ((cl_list = split_at(sv_list, ':')) == 0) { 186 tcpd_warn("missing \":\" separator"); 187 continue; 188 } 189 sh_cmd = split_at(cl_list, ':'); 190 match = list_match(sv_list, request, server_match) 191 && list_match(cl_list, request, client_match); 192 } 193 (void) fclose(fp); 194 } else if (errno != ENOENT) { 195 tcpd_warn("cannot open %s: %m", table); 196 } 197 if (match) { 198 if (hosts_access_verbose > 1) 199 syslog(LOG_DEBUG, "matched: %s line %d", 200 tcpd_context.file, tcpd_context.line); 201 if (sh_cmd) { 202 #ifdef PROCESS_OPTIONS 203 process_options(sh_cmd, request); 204 #else 205 char cmd[BUFSIZ]; 206 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request)); 207 #endif 208 } 209 } 210 tcpd_context = saved_context; 211 return (match); 212 } 213 214 /* list_match - match a request against a list of patterns with exceptions */ 215 216 static int list_match(char *list, struct request_info *request, 217 int (*match_fn)(char *, struct request_info *)) 218 { 219 char *tok; 220 221 /* 222 * Process tokens one at a time. We have exhausted all possible matches 223 * when we reach an "EXCEPT" token or the end of the list. If we do find 224 * a match, look for an "EXCEPT" list and recurse to determine whether 225 * the match is affected by any exceptions. 226 */ 227 228 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) { 229 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */ 230 return (NO); 231 if (match_fn(tok, request)) { /* YES: look for exceptions */ 232 while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT")) 233 /* VOID */ ; 234 return (tok == 0 || list_match((char *) 0, request, match_fn) == 0); 235 } 236 } 237 return (NO); 238 } 239 240 /* server_match - match server information */ 241 242 static int server_match(tok, request) 243 char *tok; 244 struct request_info *request; 245 { 246 char *host; 247 248 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */ 249 return (string_match(tok, eval_daemon(request))); 250 } else { /* daemon@host */ 251 return (string_match(tok, eval_daemon(request)) 252 && host_match(host, request->server)); 253 } 254 } 255 256 /* client_match - match client information */ 257 258 static int client_match(tok, request) 259 char *tok; 260 struct request_info *request; 261 { 262 char *host; 263 264 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */ 265 return (host_match(tok, request->client)); 266 } else { /* user@host */ 267 return (host_match(host, request->client) 268 && string_match(tok, eval_user(request))); 269 } 270 } 271 272 /* hostfile_match - look up host patterns from file */ 273 274 static int hostfile_match(path, host) 275 char *path; 276 struct host_info *host; 277 { 278 char tok[BUFSIZ]; 279 int match = NO; 280 FILE *fp; 281 282 if ((fp = fopen(path, "r")) != 0) { 283 while (fscanf(fp, "%s", tok) == 1 && !(match = host_match(tok, host))) 284 /* void */ ; 285 fclose(fp); 286 } else if (errno != ENOENT) { 287 tcpd_warn("open %s: %m", path); 288 } 289 return (match); 290 } 291 292 /* host_match - match host name and/or address against pattern */ 293 294 static int host_match(tok, host) 295 char *tok; 296 struct host_info *host; 297 { 298 char *mask; 299 300 /* 301 * This code looks a little hairy because we want to avoid unnecessary 302 * hostname lookups. 303 * 304 * The KNOWN pattern requires that both address AND name be known; some 305 * patterns are specific to host names or to host addresses; all other 306 * patterns are satisfied when either the address OR the name match. 307 */ 308 309 if (tok[0] == '@') { /* netgroup: look it up */ 310 #ifdef NETGROUP 311 static char *mydomain = 0; 312 if (mydomain == 0) 313 yp_get_default_domain(&mydomain); 314 return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain)); 315 #else 316 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */ 317 return (NO); 318 #endif 319 } else if (tok[0] == '/') { /* /file hack */ 320 return (hostfile_match(tok, host)); 321 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */ 322 char *name = eval_hostname(host); 323 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name)); 324 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */ 325 char *name = eval_hostname(host); 326 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name)); 327 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */ 328 return (masked_match(tok, mask, eval_hostaddr(host))); 329 } else { /* anything else */ 330 return (string_match(tok, eval_hostaddr(host)) 331 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host)))); 332 } 333 } 334 335 /* string_match - match string against pattern */ 336 337 static int string_match(tok, string) 338 char *tok; 339 char *string; 340 { 341 int n; 342 343 #ifdef INET6 344 /* convert IPv4 mapped IPv6 address to IPv4 address */ 345 if (STRN_EQ(string, "::ffff:", 7) 346 && dot_quad_addr(string + 7) != INADDR_NONE) { 347 string += 7; 348 } 349 #endif 350 if (tok[0] == '.') { /* suffix */ 351 n = strlen(string) - strlen(tok); 352 return (n > 0 && STR_EQ(tok, string + n)); 353 } else if (STR_EQ(tok, "ALL")) { /* all: match any */ 354 return (YES); 355 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */ 356 return (STR_NE(string, unknown)); 357 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */ 358 return (STRN_EQ(tok, string, n)); 359 } else { /* exact match */ 360 #ifdef INET6 361 struct addrinfo hints, *res; 362 struct sockaddr_in6 pat, addr; 363 int len, ret; 364 char ch; 365 366 len = strlen(tok); 367 if (*tok == '[' && tok[len - 1] == ']') { 368 ch = tok[len - 1]; 369 tok[len - 1] = '\0'; 370 memset(&hints, 0, sizeof(hints)); 371 hints.ai_family = AF_INET6; 372 hints.ai_socktype = SOCK_STREAM; 373 hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST; 374 if ((ret = getaddrinfo(tok + 1, NULL, &hints, &res)) == 0) { 375 memcpy(&pat, res->ai_addr, sizeof(pat)); 376 freeaddrinfo(res); 377 } 378 tok[len - 1] = ch; 379 if (ret != 0 || getaddrinfo(string, NULL, &hints, &res) != 0) 380 return NO; 381 memcpy(&addr, res->ai_addr, sizeof(addr)); 382 freeaddrinfo(res); 383 if (pat.sin6_scope_id != 0 && 384 addr.sin6_scope_id != pat.sin6_scope_id) 385 return NO; 386 return (!memcmp(&pat.sin6_addr, &addr.sin6_addr, 387 sizeof(struct in6_addr))); 388 return (ret); 389 } 390 #endif 391 return (STR_EQ(tok, string)); 392 } 393 } 394 395 /* masked_match - match address against netnumber/netmask */ 396 397 #ifdef INET6 398 static int masked_match(net_tok, mask_tok, string) 399 char *net_tok; 400 char *mask_tok; 401 char *string; 402 { 403 return (masked_match4(net_tok, mask_tok, string) || 404 masked_match6(net_tok, mask_tok, string)); 405 } 406 407 static int masked_match4(net_tok, mask_tok, string) 408 #else 409 static int masked_match(net_tok, mask_tok, string) 410 #endif 411 char *net_tok; 412 char *mask_tok; 413 char *string; 414 { 415 #ifdef INET6 416 u_int32_t net; 417 u_int32_t mask; 418 u_int32_t addr; 419 #else 420 unsigned long net; 421 unsigned long mask; 422 unsigned long addr; 423 #endif 424 425 /* 426 * Disallow forms other than dotted quad: the treatment that inet_addr() 427 * gives to forms with less than four components is inconsistent with the 428 * access control language. John P. Rouillard <rouilj@cs.umb.edu>. 429 */ 430 431 if ((addr = dot_quad_addr(string)) == INADDR_NONE) 432 return (NO); 433 if ((net = dot_quad_addr(net_tok)) == INADDR_NONE 434 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) { 435 #ifndef INET6 436 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok); 437 #endif 438 return (NO); /* not tcpd_jump() */ 439 } 440 return ((addr & mask) == net); 441 } 442 443 #ifdef INET6 444 static int masked_match6(net_tok, mask_tok, string) 445 char *net_tok; 446 char *mask_tok; 447 char *string; 448 { 449 struct addrinfo hints, *res; 450 struct sockaddr_in6 net, addr; 451 u_int32_t mask; 452 int len, mask_len, i = 0; 453 char ch; 454 455 memset(&hints, 0, sizeof(hints)); 456 hints.ai_family = AF_INET6; 457 hints.ai_socktype = SOCK_STREAM; 458 hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST; 459 if (getaddrinfo(string, NULL, &hints, &res) != 0) 460 return NO; 461 memcpy(&addr, res->ai_addr, sizeof(addr)); 462 freeaddrinfo(res); 463 464 if (IN6_IS_ADDR_V4MAPPED(&addr.sin6_addr)) { 465 if ((*(u_int32_t *)&net.sin6_addr.s6_addr[12] = dot_quad_addr(net_tok)) == INADDR_NONE 466 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) 467 return (NO); 468 return ((*(u_int32_t *)&addr.sin6_addr.s6_addr[12] & mask) == *(u_int32_t *)&net.sin6_addr.s6_addr[12]); 469 } 470 471 /* match IPv6 address against netnumber/prefixlen */ 472 len = strlen(net_tok); 473 if (*net_tok != '[' || net_tok[len - 1] != ']') 474 return NO; 475 ch = net_tok[len - 1]; 476 net_tok[len - 1] = '\0'; 477 if (getaddrinfo(net_tok + 1, NULL, &hints, &res) != 0) { 478 net_tok[len - 1] = ch; 479 return NO; 480 } 481 memcpy(&net, res->ai_addr, sizeof(net)); 482 freeaddrinfo(res); 483 net_tok[len - 1] = ch; 484 if ((mask_len = atoi(mask_tok)) < 0 || mask_len > 128) 485 return NO; 486 487 if (net.sin6_scope_id != 0 && addr.sin6_scope_id != net.sin6_scope_id) 488 return NO; 489 while (mask_len > 0) { 490 if (mask_len < 32) { 491 mask = htonl(~(0xffffffff >> mask_len)); 492 if ((*(u_int32_t *)&addr.sin6_addr.s6_addr[i] & mask) != (*(u_int32_t *)&net.sin6_addr.s6_addr[i] & mask)) 493 return NO; 494 break; 495 } 496 if (*(u_int32_t *)&addr.sin6_addr.s6_addr[i] != *(u_int32_t *)&net.sin6_addr.s6_addr[i]) 497 return NO; 498 i += 4; 499 mask_len -= 32; 500 } 501 return YES; 502 } 503 #endif /* INET6 */ 504