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