1 /* 2 * Copyright 2004 Sun Microsystems, Inc. All rights reserved. 3 * Use is subject to license terms. 4 */ 5 6 /* 7 * This module implements a simple access control language that is based on 8 * host (or domain) names, NIS (host) netgroup names, IP addresses (or 9 * network numbers) and daemon process names. When a match is found the 10 * search is terminated, and depending on whether PROCESS_OPTIONS is defined, 11 * a list of options is executed or an optional shell command is executed. 12 * 13 * Host and user names are looked up on demand, provided that suitable endpoint 14 * information is available as sockaddr_in structures or TLI netbufs. As a 15 * side effect, the pattern matching process may change the contents of 16 * request structure fields. 17 * 18 * Diagnostics are reported through syslog(3). 19 * 20 * Compile with -DNETGROUP if your library provides support for netgroups. 21 * 22 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands. 23 */ 24 25 #ifndef lint 26 static char sccsid[] = "@(#) hosts_access.c 1.21 97/02/12 02:13:22"; 27 #endif 28 29 /* System libraries. */ 30 31 #include <sys/types.h> 32 #include <sys/param.h> 33 #include <netinet/in.h> 34 #include <arpa/inet.h> 35 #include <rpcsvc/ypclnt.h> 36 #include <netdb.h> 37 #include <stdio.h> 38 #include <stdlib.h> 39 #include <unistd.h> 40 #include <syslog.h> 41 #include <ctype.h> 42 #include <errno.h> 43 #include <setjmp.h> 44 #include <string.h> 45 46 extern char *fgets(); 47 extern int errno; 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(); 88 static int list_match(); 89 static int server_match(); 90 static int client_match(); 91 static int host_match(); 92 static int string_match(); 93 static int masked_match(); 94 #ifdef HAVE_IPV6 95 static void ipv6_mask(); 96 #endif 97 98 /* Size of logical line buffer. */ 99 100 #define BUFLEN 2048 101 102 /* hosts_access - host access control facility */ 103 104 int hosts_access(request) 105 struct request_info *request; 106 { 107 int verdict; 108 109 /* 110 * If the (daemon, client) pair is matched by an entry in the file 111 * /etc/hosts.allow, access is granted. Otherwise, if the (daemon, 112 * client) pair is matched by an entry in the file /etc/hosts.deny, 113 * access is denied. Otherwise, access is granted. A non-existent 114 * access-control file is treated as an empty file. 115 * 116 * After a rule has been matched, the optional language extensions may 117 * decide to grant or refuse service anyway. Or, while a rule is being 118 * processed, a serious error is found, and it seems better to play safe 119 * and deny service. All this is done by jumping back into the 120 * hosts_access() routine, bypassing the regular return from the 121 * table_match() function calls below. 122 */ 123 124 if (resident <= 0) 125 resident++; 126 verdict = setjmp(tcpd_buf); 127 if (verdict != 0) 128 return (verdict == AC_PERMIT); 129 if (table_match(hosts_allow_table, request)) 130 return (YES); 131 if (table_match(hosts_deny_table, request)) 132 return (NO); 133 return (YES); 134 } 135 136 /* table_match - match table entries with (daemon, client) pair */ 137 138 static int table_match(table, request) 139 char *table; 140 struct request_info *request; 141 { 142 FILE *fp; 143 char sv_list[BUFLEN]; /* becomes list of daemons */ 144 char *cl_list; /* becomes list of clients */ 145 char *sh_cmd; /* becomes optional shell command */ 146 int match = NO; 147 struct tcpd_context saved_context; 148 149 saved_context = tcpd_context; /* stupid compilers */ 150 151 /* 152 * Between the fopen() and fclose() calls, avoid jumps that may cause 153 * file descriptor leaks. 154 */ 155 156 if ((fp = fopen(table, "r")) != 0) { 157 tcpd_context.file = table; 158 tcpd_context.line = 0; 159 while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) { 160 if (sv_list[strlen(sv_list) - 1] != '\n') { 161 tcpd_warn("missing newline or line too long"); 162 continue; 163 } 164 if (sv_list[0] == '#' || sv_list[strspn(sv_list, " \t\r\n")] == 0) 165 continue; 166 if ((cl_list = split_at(skip_ipv6_addrs(sv_list), ':')) == 0) { 167 tcpd_warn("missing \":\" separator"); 168 continue; 169 } 170 sh_cmd = split_at(skip_ipv6_addrs(cl_list), ':'); 171 match = list_match(sv_list, request, server_match) 172 && list_match(cl_list, request, client_match); 173 } 174 (void) fclose(fp); 175 } else if (errno != ENOENT) { 176 tcpd_warn("cannot open %s: %m", table); 177 } 178 if (match) { 179 if (hosts_access_verbose > 1) 180 syslog(LOG_DEBUG, "matched: %s line %d", 181 tcpd_context.file, tcpd_context.line); 182 if (sh_cmd) { 183 #ifdef PROCESS_OPTIONS 184 process_options(sh_cmd, request); 185 #else 186 char cmd[BUFSIZ]; 187 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request)); 188 #endif 189 } 190 } 191 tcpd_context = saved_context; 192 return (match); 193 } 194 195 /* list_match - match a request against a list of patterns with exceptions */ 196 197 static int list_match(list, request, match_fn) 198 char *list; 199 struct request_info *request; 200 int (*match_fn) (); 201 { 202 char *tok; 203 204 /* 205 * Process tokens one at a time. We have exhausted all possible matches 206 * when we reach an "EXCEPT" token or the end of the list. If we do find 207 * a match, look for an "EXCEPT" list and recurse to determine whether 208 * the match is affected by any exceptions. 209 */ 210 211 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) { 212 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */ 213 return (NO); 214 if (match_fn(tok, request)) { /* YES: look for exceptions */ 215 while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT")) 216 /* VOID */ ; 217 return (tok == 0 || list_match((char *) 0, request, match_fn) == 0); 218 } 219 } 220 return (NO); 221 } 222 223 /* server_match - match server information */ 224 225 static int server_match(tok, request) 226 char *tok; 227 struct request_info *request; 228 { 229 char *host; 230 231 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */ 232 return (string_match(tok, eval_daemon(request))); 233 } else { /* daemon@host */ 234 return (string_match(tok, eval_daemon(request)) 235 && host_match(host, request->server)); 236 } 237 } 238 239 /* client_match - match client information */ 240 241 static int client_match(tok, request) 242 char *tok; 243 struct request_info *request; 244 { 245 char *host; 246 247 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */ 248 return (host_match(tok, request->client)); 249 } else { /* user@host */ 250 return (host_match(host, request->client) 251 && string_match(tok, eval_user(request))); 252 } 253 } 254 255 /* host_match - match host name and/or address against pattern */ 256 257 static int host_match(tok, host) 258 char *tok; 259 struct host_info *host; 260 { 261 char *mask; 262 263 /* 264 * This code looks a little hairy because we want to avoid unnecessary 265 * hostname lookups. 266 * 267 * The KNOWN pattern requires that both address AND name be known; some 268 * patterns are specific to host names or to host addresses; all other 269 * patterns are satisfied when either the address OR the name match. 270 */ 271 272 if (tok[0] == '@') { /* netgroup: look it up */ 273 #ifdef NETGROUP 274 static char *mydomain = 0; 275 if (mydomain == 0) 276 yp_get_default_domain(&mydomain); 277 return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain)); 278 #else 279 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */ 280 return (NO); 281 #endif 282 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */ 283 char *name = eval_hostname(host); 284 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name)); 285 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */ 286 char *name = eval_hostname(host); 287 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name)); 288 #ifdef HAVE_IPV6 289 } else if (tok[0] == '[') { /* IPv6 address */ 290 struct in6_addr in6, hostin6, *hip; 291 char *cbr; 292 char *slash; 293 int mask = IPV6_ABITS; 294 295 /* 296 * In some cases we don't get the sockaddr, only the addr. 297 * We use inet_pton to convert it to its binary representation 298 * and match against that. 299 */ 300 if (host->sin == NULL) { 301 if (host->addr == NULL || 302 inet_pton(AF_INET6, host->addr, &hostin6) != 1) { 303 return (NO); 304 } 305 hip = &hostin6; 306 } else { 307 if (SGFAM(host->sin) != AF_INET6) 308 return (NO); 309 hip = &host->sin->sg_sin6.sin6_addr; 310 } 311 312 if (cbr = strchr(tok, ']')) 313 *cbr = '\0'; 314 315 /* 316 * A /nnn prefix specifies how many bits of the address we 317 * need to check. 318 */ 319 if (slash = strchr(tok, '/')) { 320 *slash = '\0'; 321 mask = atoi(slash+1); 322 if (mask < 0 || mask > IPV6_ABITS) { 323 tcpd_warn("bad IP6 prefix specification"); 324 return (NO); 325 } 326 /* Copy, because we need to modify it below */ 327 if (host->sin != NULL) { 328 hostin6 = host->sin->sg_sin6.sin6_addr; 329 hip = &hostin6; 330 } 331 } 332 333 if (cbr == NULL || inet_pton(AF_INET6, tok+1, &in6) != 1) { 334 tcpd_warn("bad IP6 address specification"); 335 return (NO); 336 } 337 /* 338 * Zero the bits we're not interested in in both addresses 339 * then compare. Note that we take a copy of the host info 340 * in that case. 341 */ 342 if (mask != IPV6_ABITS) { 343 ipv6_mask(&in6, mask); 344 ipv6_mask(hip, mask); 345 } 346 if (memcmp(&in6, hip, sizeof(in6)) == 0) 347 return (YES); 348 return (NO); 349 #endif 350 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */ 351 return (masked_match(tok, mask, eval_hostaddr(host))); 352 } else { /* anything else */ 353 return (string_match(tok, eval_hostaddr(host)) 354 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host)))); 355 } 356 } 357 358 /* string_match - match string against pattern */ 359 360 static int string_match(tok, string) 361 char *tok; 362 char *string; 363 { 364 int n; 365 366 if (tok[0] == '.') { /* suffix */ 367 n = strlen(string) - strlen(tok); 368 return (n > 0 && STR_EQ(tok, string + n)); 369 } else if (STR_EQ(tok, "ALL")) { /* all: match any */ 370 return (YES); 371 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */ 372 return (STR_NE(string, unknown)); 373 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */ 374 return (STRN_EQ(tok, string, n)); 375 } else { /* exact match */ 376 return (STR_EQ(tok, string)); 377 } 378 } 379 380 /* masked_match - match address against netnumber/netmask */ 381 382 static int masked_match(net_tok, mask_tok, string) 383 char *net_tok; 384 char *mask_tok; 385 char *string; 386 { 387 unsigned long net; 388 unsigned long mask; 389 unsigned long addr; 390 391 /* 392 * Disallow forms other than dotted quad: the treatment that inet_addr() 393 * gives to forms with less than four components is inconsistent with the 394 * access control language. John P. Rouillard <rouilj@cs.umb.edu>. 395 */ 396 397 if ((addr = dot_quad_addr(string)) == INADDR_NONE) 398 return (NO); 399 if ((net = dot_quad_addr(net_tok)) == INADDR_NONE 400 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) { 401 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok); 402 return (NO); /* not tcpd_jump() */ 403 } 404 return ((addr & mask) == net); 405 } 406 407 #ifdef HAVE_IPV6 408 /* 409 * Function that zeros all but the first "maskbits" bits of the IPV6 address 410 * This function can be made generic by specifying an address length as 411 * extra parameter. (So Wietse can implement 1.2.3.4/16) 412 */ 413 static void ipv6_mask(in6p, maskbits) 414 struct in6_addr *in6p; 415 int maskbits; 416 { 417 uchar_t *p = (uchar_t*) in6p; 418 419 if (maskbits < 0 || maskbits >= IPV6_ABITS) 420 return; 421 422 p += maskbits / 8; 423 maskbits %= 8; 424 425 if (maskbits != 0) 426 *p++ &= 0xff << (8 - maskbits); 427 428 while (p < (((uchar_t*) in6p)) + sizeof(*in6p)) 429 *p++ = 0; 430 } 431 #endif 432