hosts_access.c revision 1.5.2.1
1 /* $NetBSD: hosts_access.c,v 1.5.2.1 2000/01/23 12:01:27 he Exp $ */ 2 3 /* 4 * This module implements a simple access control language that is based on 5 * host (or domain) names, NIS (host) netgroup names, IP addresses (or 6 * network numbers) and daemon process names. When a match is found the 7 * search is terminated, and depending on whether PROCESS_OPTIONS is defined, 8 * a list of options is executed or an optional shell command is executed. 9 * 10 * Host and user names are looked up on demand, provided that suitable endpoint 11 * information is available as sockaddr_in structures or TLI netbufs. As a 12 * side effect, the pattern matching process may change the contents of 13 * request structure fields. 14 * 15 * Diagnostics are reported through syslog(3). 16 * 17 * Compile with -DNETGROUP if your library provides support for netgroups. 18 * 19 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands. 20 */ 21 22 #include <sys/cdefs.h> 23 #ifndef lint 24 #if 0 25 static char sccsid[] = "@(#) hosts_access.c 1.20 96/02/11 17:01:27"; 26 #else 27 __RCSID("$NetBSD: hosts_access.c,v 1.5.2.1 2000/01/23 12:01:27 he Exp $"); 28 #endif 29 #endif 30 31 /* System libraries. */ 32 33 #include <sys/types.h> 34 #include <sys/param.h> 35 #include <netinet/in.h> 36 #include <arpa/inet.h> 37 #include <stdio.h> 38 #include <stdlib.h> 39 #include <syslog.h> 40 #include <ctype.h> 41 #include <errno.h> 42 #include <setjmp.h> 43 #include <string.h> 44 #include <netdb.h> 45 #ifdef NETGROUP 46 #include <netgroup.h> 47 #include <rpcsvc/ypclnt.h> 48 #endif 49 50 #ifndef INADDR_NONE 51 #define INADDR_NONE (-1) /* XXX should be 0xffffffff */ 52 #endif 53 54 /* Local stuff. */ 55 56 #include "tcpd.h" 57 58 /* Error handling. */ 59 60 extern jmp_buf tcpd_buf; 61 62 /* Delimiters for lists of daemons or clients. */ 63 64 static char sep[] = ", \t\r\n"; 65 66 /* Constants to be used in assignments only, not in comparisons... */ 67 68 #define YES 1 69 #define NO 0 70 71 /* 72 * These variables are globally visible so that they can be redirected in 73 * verification mode. 74 */ 75 76 char *hosts_allow_table = HOSTS_ALLOW; 77 char *hosts_deny_table = HOSTS_DENY; 78 int hosts_access_verbose = 0; 79 80 /* 81 * In a long-running process, we are not at liberty to just go away. 82 */ 83 84 int resident = (-1); /* -1, 0: unknown; +1: yes */ 85 86 /* Forward declarations. */ 87 88 static int table_match __P((char *, struct request_info *)); 89 static int list_match __P((char *, struct request_info *, 90 int (*)(char *, struct request_info *))); 91 static int server_match __P((char *, struct request_info *)); 92 static int client_match __P((char *, struct request_info *)); 93 static int host_match __P((char *, struct host_info *)); 94 static int rbl_match __P((char *, char *)); 95 static int string_match __P((char *, char *)); 96 static int masked_match __P((char *, char *, char *)); 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 if ((verdict = setjmp(tcpd_buf)) != 0) 127 return (verdict == AC_PERMIT); 128 if (table_match(hosts_allow_table, request)) 129 return (YES); 130 if (table_match(hosts_deny_table, request)) 131 return (NO); 132 return (YES); 133 } 134 135 /* table_match - match table entries with (daemon, client) pair */ 136 137 static int table_match(table, request) 138 char *table; 139 struct request_info *request; 140 { 141 FILE *fp; 142 char sv_list[BUFLEN]; /* becomes list of daemons */ 143 char *cl_list; /* becomes list of clients */ 144 char *sh_cmd = NULL; /* becomes optional shell command */ 145 int match = NO; 146 struct tcpd_context saved_context; 147 148 saved_context = tcpd_context; /* stupid compilers */ 149 150 /* 151 * Between the fopen() and fclose() calls, avoid jumps that may cause 152 * file descriptor leaks. 153 */ 154 155 if ((fp = fopen(table, "r")) != 0) { 156 tcpd_context.file = table; 157 tcpd_context.line = 0; 158 while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) { 159 if (sv_list[strlen(sv_list) - 1] != '\n') { 160 tcpd_warn("missing newline or line too long"); 161 continue; 162 } 163 if (sv_list[0] == '#' || sv_list[strspn(sv_list, " \t\r\n")] == 0) 164 continue; 165 if ((cl_list = split_at(sv_list, ':')) == 0) { 166 tcpd_warn("missing \":\" separator"); 167 continue; 168 } 169 sh_cmd = split_at(cl_list, ':'); 170 match = list_match(sv_list, request, server_match) 171 && list_match(cl_list, request, client_match); 172 } 173 (void) fclose(fp); 174 } else if (errno != ENOENT) { 175 tcpd_warn("cannot open %s: %m", table); 176 } 177 if (match) { 178 if (hosts_access_verbose > 1) 179 syslog(LOG_DEBUG, "matched: %s line %d", 180 tcpd_context.file, tcpd_context.line); 181 if (sh_cmd) { 182 #ifdef PROCESS_OPTIONS 183 process_options(sh_cmd, request); 184 #else 185 char cmd[BUFSIZ]; 186 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request)); 187 #endif 188 } 189 } 190 tcpd_context = saved_context; 191 return (match); 192 } 193 194 /* list_match - match a request against a list of patterns with exceptions */ 195 196 static int list_match(list, request, match_fn) 197 char *list; 198 struct request_info *request; 199 int (*match_fn) __P((char *, struct request_info *)); 200 { 201 char *tok; 202 203 /* 204 * Process tokens one at a time. We have exhausted all possible matches 205 * when we reach an "EXCEPT" token or the end of the list. If we do find 206 * a match, look for an "EXCEPT" list and recurse to determine whether 207 * the match is affected by any exceptions. 208 */ 209 210 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) { 211 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */ 212 return (NO); 213 if (match_fn(tok, request)) { /* YES: look for exceptions */ 214 while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT")) 215 /* VOID */ ; 216 return (tok == 0 || list_match((char *) 0, request, match_fn) == 0); 217 } 218 } 219 return (NO); 220 } 221 222 /* server_match - match server information */ 223 224 static int server_match(tok, request) 225 char *tok; 226 struct request_info *request; 227 { 228 char *host; 229 230 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */ 231 return (string_match(tok, eval_daemon(request))); 232 } else { /* daemon@host */ 233 return (string_match(tok, eval_daemon(request)) 234 && host_match(host, request->server)); 235 } 236 } 237 238 /* client_match - match client information */ 239 240 static int client_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 host */ 247 return (host_match(tok, request->client)); 248 } else { /* user@host */ 249 return (host_match(host, request->client) 250 && string_match(tok, eval_user(request))); 251 } 252 } 253 254 /* host_match - match host name and/or address against pattern */ 255 256 static int host_match(tok, host) 257 char *tok; 258 struct host_info *host; 259 { 260 char *mask; 261 262 /* 263 * This code looks a little hairy because we want to avoid unnecessary 264 * hostname lookups. 265 * 266 * The KNOWN pattern requires that both address AND name be known; some 267 * patterns are specific to host names or to host addresses; all other 268 * patterns are satisfied when either the address OR the name match. 269 */ 270 271 if (tok[0] == '@') { /* netgroup: look it up */ 272 #ifdef NETGROUP 273 static char *mydomain = 0; 274 if (mydomain == 0) 275 yp_get_default_domain(&mydomain); 276 return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain)); 277 #else 278 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */ 279 return (NO); 280 #endif 281 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */ 282 char *name = eval_hostname(host); 283 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name)); 284 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */ 285 char *name = eval_hostname(host); 286 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name)); 287 } else if (strncmp(tok, "{RBL}.", 6) == 0) { /* RBL lookup in domain */ 288 return rbl_match(tok+6, eval_hostaddr(host)); 289 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */ 290 return (masked_match(tok, mask, eval_hostaddr(host))); 291 } else { /* anything else */ 292 return (string_match(tok, eval_hostaddr(host)) 293 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host)))); 294 } 295 } 296 297 /* rbl_match() - match host by looking up in RBL domain */ 298 299 static int rbl_match(rbl_domain, rbl_hostaddr) 300 char *rbl_domain; /* RBL domain */ 301 char *rbl_hostaddr; /* hostaddr */ 302 { 303 char *rbl_name; 304 unsigned long host_address; 305 int ret = NO; 306 size_t len = strlen(rbl_domain) + (4 * 4) + 2; 307 308 if ((host_address = dot_quad_addr(rbl_hostaddr)) == INADDR_NONE) { 309 tcpd_warn("unable to convert %s to address", rbl_hostaddr); 310 return (NO); 311 } 312 /* construct the rbl name to look up */ 313 if ((rbl_name = malloc(len)) == NULL) { 314 tcpd_jump("not enough memory to build RBL name for %s in %s", rbl_hostaddr, rbl_domain); 315 /* NOTREACHED */ 316 } 317 snprintf(rbl_name, len, "%u.%u.%u.%u.%s", 318 (unsigned int) ((host_address) & 0xff), 319 (unsigned int) ((host_address >> 8) & 0xff), 320 (unsigned int) ((host_address >> 16) & 0xff), 321 (unsigned int) ((host_address >> 24) & 0xff), 322 rbl_domain); 323 /* look it up */ 324 if (gethostbyname(rbl_name) != NULL) { 325 /* successful lookup - they're on the RBL list */ 326 ret = YES; 327 } 328 free(rbl_name); 329 330 return ret; 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 if (tok[0] == '.') { /* suffix */ 342 n = strlen(string) - strlen(tok); 343 return (n > 0 && STR_EQ(tok, string + n)); 344 } else if (STR_EQ(tok, "ALL")) { /* all: match any */ 345 return (YES); 346 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */ 347 return (STR_NE(string, unknown)); 348 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */ 349 return (STRN_EQ(tok, string, n)); 350 } else { /* exact match */ 351 return (STR_EQ(tok, string)); 352 } 353 } 354 355 /* masked_match - match address against netnumber/netmask */ 356 357 static int masked_match(net_tok, mask_tok, string) 358 char *net_tok; 359 char *mask_tok; 360 char *string; 361 { 362 unsigned long net; 363 unsigned long mask; 364 unsigned long addr; 365 366 /* 367 * Disallow forms other than dotted quad: the treatment that inet_addr() 368 * gives to forms with less than four components is inconsistent with the 369 * access control language. John P. Rouillard <rouilj (at) cs.umb.edu>. 370 */ 371 372 if ((addr = dot_quad_addr(string)) == INADDR_NONE) 373 return (NO); 374 if ((net = dot_quad_addr(net_tok)) == INADDR_NONE 375 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) { 376 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok); 377 return (NO); /* not tcpd_jump() */ 378 } 379 return ((addr & mask) == net); 380 } 381
Indexes created Thu Oct 02 10:09:58 GMT 2025