1 /* $NetBSD: hosts_access.c,v 1.3 1997/10/26 20:49:32 christos 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 1.3 1997/10/26 20:49:32 christos 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 <syslog.h> 39 #include <ctype.h> 40 #include <errno.h> 41 #include <setjmp.h> 42 #include <string.h> 43 #ifdef NETGROUP 44 #include <netgroup.h> 45 #include <rpcsvc/ypclnt.h> 46 #endif 47 48 extern int errno; 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 string_match __P((char *, char *)); 95 static int masked_match __P((char *, char *, char *)); 96 97 /* Size of logical line buffer. */ 98 99 #define BUFLEN 2048 100 101 /* hosts_access - host access control facility */ 102 103 int hosts_access(request) 104 struct request_info *request; 105 { 106 int verdict; 107 108 /* 109 * If the (daemon, client) pair is matched by an entry in the file 110 * /etc/hosts.allow, access is granted. Otherwise, if the (daemon, 111 * client) pair is matched by an entry in the file /etc/hosts.deny, 112 * access is denied. Otherwise, access is granted. A non-existent 113 * access-control file is treated as an empty file. 114 * 115 * After a rule has been matched, the optional language extensions may 116 * decide to grant or refuse service anyway. Or, while a rule is being 117 * processed, a serious error is found, and it seems better to play safe 118 * and deny service. All this is done by jumping back into the 119 * hosts_access() routine, bypassing the regular return from the 120 * table_match() function calls below. 121 */ 122 123 if (resident <= 0) 124 resident++; 125 if ((verdict = setjmp(tcpd_buf)) != 0) 126 return (verdict == AC_PERMIT); 127 if (table_match(hosts_allow_table, request)) 128 return (YES); 129 if (table_match(hosts_deny_table, request)) 130 return (NO); 131 return (YES); 132 } 133 134 /* table_match - match table entries with (daemon, client) pair */ 135 136 static int table_match(table, request) 137 char *table; 138 struct request_info *request; 139 { 140 FILE *fp; 141 char sv_list[BUFLEN]; /* becomes list of daemons */ 142 char *cl_list; /* becomes list of clients */ 143 char *sh_cmd = NULL; /* becomes optional shell command */ 144 int match = NO; 145 struct tcpd_context saved_context; 146 147 saved_context = tcpd_context; /* stupid compilers */ 148 149 /* 150 * Between the fopen() and fclose() calls, avoid jumps that may cause 151 * file descriptor leaks. 152 */ 153 154 if ((fp = fopen(table, "r")) != 0) { 155 tcpd_context.file = table; 156 tcpd_context.line = 0; 157 while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) { 158 if (sv_list[strlen(sv_list) - 1] != '\n') { 159 tcpd_warn("missing newline or line too long"); 160 continue; 161 } 162 if (sv_list[0] == '#' || sv_list[strspn(sv_list, " \t\r\n")] == 0) 163 continue; 164 if ((cl_list = split_at(sv_list, ':')) == 0) { 165 tcpd_warn("missing \":\" separator"); 166 continue; 167 } 168 sh_cmd = split_at(cl_list, ':'); 169 match = list_match(sv_list, request, server_match) 170 && list_match(cl_list, request, client_match); 171 } 172 (void) fclose(fp); 173 } else if (errno != ENOENT) { 174 tcpd_warn("cannot open %s: %m", table); 175 } 176 if (match) { 177 if (hosts_access_verbose > 1) 178 syslog(LOG_DEBUG, "matched: %s line %d", 179 tcpd_context.file, tcpd_context.line); 180 if (sh_cmd) { 181 #ifdef PROCESS_OPTIONS 182 process_options(sh_cmd, request); 183 #else 184 char cmd[BUFSIZ]; 185 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request)); 186 #endif 187 } 188 } 189 tcpd_context = saved_context; 190 return (match); 191 } 192 193 /* list_match - match a request against a list of patterns with exceptions */ 194 195 static int list_match(list, request, match_fn) 196 char *list; 197 struct request_info *request; 198 int (*match_fn) __P((char *, struct request_info *)); 199 { 200 char *tok; 201 202 /* 203 * Process tokens one at a time. We have exhausted all possible matches 204 * when we reach an "EXCEPT" token or the end of the list. If we do find 205 * a match, look for an "EXCEPT" list and recurse to determine whether 206 * the match is affected by any exceptions. 207 */ 208 209 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) { 210 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */ 211 return (NO); 212 if (match_fn(tok, request)) { /* YES: look for exceptions */ 213 while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT")) 214 /* VOID */ ; 215 return (tok == 0 || list_match((char *) 0, request, match_fn) == 0); 216 } 217 } 218 return (NO); 219 } 220 221 /* server_match - match server information */ 222 223 static int server_match(tok, request) 224 char *tok; 225 struct request_info *request; 226 { 227 char *host; 228 229 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */ 230 return (string_match(tok, eval_daemon(request))); 231 } else { /* daemon@host */ 232 return (string_match(tok, eval_daemon(request)) 233 && host_match(host, request->server)); 234 } 235 } 236 237 /* client_match - match client information */ 238 239 static int client_match(tok, request) 240 char *tok; 241 struct request_info *request; 242 { 243 char *host; 244 245 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */ 246 return (host_match(tok, request->client)); 247 } else { /* user@host */ 248 return (host_match(host, request->client) 249 && string_match(tok, eval_user(request))); 250 } 251 } 252 253 /* host_match - match host name and/or address against pattern */ 254 255 static int host_match(tok, host) 256 char *tok; 257 struct host_info *host; 258 { 259 char *mask; 260 261 /* 262 * This code looks a little hairy because we want to avoid unnecessary 263 * hostname lookups. 264 * 265 * The KNOWN pattern requires that both address AND name be known; some 266 * patterns are specific to host names or to host addresses; all other 267 * patterns are satisfied when either the address OR the name match. 268 */ 269 270 if (tok[0] == '@') { /* netgroup: look it up */ 271 #ifdef NETGROUP 272 static char *mydomain = 0; 273 if (mydomain == 0) 274 yp_get_default_domain(&mydomain); 275 return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain)); 276 #else 277 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */ 278 return (NO); 279 #endif 280 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */ 281 char *name = eval_hostname(host); 282 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name)); 283 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */ 284 char *name = eval_hostname(host); 285 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name)); 286 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */ 287 return (masked_match(tok, mask, eval_hostaddr(host))); 288 } else { /* anything else */ 289 return (string_match(tok, eval_hostaddr(host)) 290 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host)))); 291 } 292 } 293 294 /* string_match - match string against pattern */ 295 296 static int string_match(tok, string) 297 char *tok; 298 char *string; 299 { 300 int n; 301 302 if (tok[0] == '.') { /* suffix */ 303 n = strlen(string) - strlen(tok); 304 return (n > 0 && STR_EQ(tok, string + n)); 305 } else if (STR_EQ(tok, "ALL")) { /* all: match any */ 306 return (YES); 307 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */ 308 return (STR_NE(string, unknown)); 309 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */ 310 return (STRN_EQ(tok, string, n)); 311 } else { /* exact match */ 312 return (STR_EQ(tok, string)); 313 } 314 } 315 316 /* masked_match - match address against netnumber/netmask */ 317 318 static int masked_match(net_tok, mask_tok, string) 319 char *net_tok; 320 char *mask_tok; 321 char *string; 322 { 323 unsigned long net; 324 unsigned long mask; 325 unsigned long addr; 326 327 /* 328 * Disallow forms other than dotted quad: the treatment that inet_addr() 329 * gives to forms with less than four components is inconsistent with the 330 * access control language. John P. Rouillard <rouilj@cs.umb.edu>. 331 */ 332 333 if ((addr = dot_quad_addr(string)) == INADDR_NONE) 334 return (NO); 335 if ((net = dot_quad_addr(net_tok)) == INADDR_NONE 336 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) { 337 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok); 338 return (NO); /* not tcpd_jump() */ 339 } 340 return ((addr & mask) == net); 341 } 342