hosts_access.c revision 1.2
1 /* $NetBSD: hosts_access.c,v 1.2 1997/10/09 21:20:30 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 1.2 1997/10/09 21:20:30 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 44 extern int errno; 45 46 #ifndef INADDR_NONE 47 #define INADDR_NONE (-1) /* XXX should be 0xffffffff */ 48 #endif 49 50 /* Local stuff. */ 51 52 #include "tcpd.h" 53 54 /* Error handling. */ 55 56 extern jmp_buf tcpd_buf; 57 58 /* Delimiters for lists of daemons or clients. */ 59 60 static char sep[] = ", \t\r\n"; 61 62 /* Constants to be used in assignments only, not in comparisons... */ 63 64 #define YES 1 65 #define NO 0 66 67 /* 68 * These variables are globally visible so that they can be redirected in 69 * verification mode. 70 */ 71 72 char *hosts_allow_table = HOSTS_ALLOW; 73 char *hosts_deny_table = HOSTS_DENY; 74 int hosts_access_verbose = 0; 75 76 /* 77 * In a long-running process, we are not at liberty to just go away. 78 */ 79 80 int resident = (-1); /* -1, 0: unknown; +1: yes */ 81 82 /* Forward declarations. */ 83 84 static int table_match __P((char *, struct request_info *)); 85 static int list_match __P((char *, struct request_info *, 86 int (*)(char *, struct request_info *))); 87 static int server_match __P((char *, struct request_info *)); 88 static int client_match __P((char *, struct request_info *)); 89 static int host_match __P((char *, struct host_info *)); 90 static int string_match __P((char *, char *)); 91 static int masked_match __P((char *, char *, char *)); 92 93 /* Size of logical line buffer. */ 94 95 #define BUFLEN 2048 96 97 /* hosts_access - host access control facility */ 98 99 int hosts_access(request) 100 struct request_info *request; 101 { 102 int verdict; 103 104 /* 105 * If the (daemon, client) pair is matched by an entry in the file 106 * /etc/hosts.allow, access is granted. Otherwise, if the (daemon, 107 * client) pair is matched by an entry in the file /etc/hosts.deny, 108 * access is denied. Otherwise, access is granted. A non-existent 109 * access-control file is treated as an empty file. 110 * 111 * After a rule has been matched, the optional language extensions may 112 * decide to grant or refuse service anyway. Or, while a rule is being 113 * processed, a serious error is found, and it seems better to play safe 114 * and deny service. All this is done by jumping back into the 115 * hosts_access() routine, bypassing the regular return from the 116 * table_match() function calls below. 117 */ 118 119 if (resident <= 0) 120 resident++; 121 if ((verdict = setjmp(tcpd_buf)) != 0) 122 return (verdict == AC_PERMIT); 123 if (table_match(hosts_allow_table, request)) 124 return (YES); 125 if (table_match(hosts_deny_table, request)) 126 return (NO); 127 return (YES); 128 } 129 130 /* table_match - match table entries with (daemon, client) pair */ 131 132 static int table_match(table, request) 133 char *table; 134 struct request_info *request; 135 { 136 FILE *fp; 137 char sv_list[BUFLEN]; /* becomes list of daemons */ 138 char *cl_list; /* becomes list of clients */ 139 char *sh_cmd = NULL; /* becomes optional shell command */ 140 int match = NO; 141 struct tcpd_context saved_context; 142 143 saved_context = tcpd_context; /* stupid compilers */ 144 145 /* 146 * Between the fopen() and fclose() calls, avoid jumps that may cause 147 * file descriptor leaks. 148 */ 149 150 if ((fp = fopen(table, "r")) != 0) { 151 tcpd_context.file = table; 152 tcpd_context.line = 0; 153 while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) { 154 if (sv_list[strlen(sv_list) - 1] != '\n') { 155 tcpd_warn("missing newline or line too long"); 156 continue; 157 } 158 if (sv_list[0] == '#' || sv_list[strspn(sv_list, " \t\r\n")] == 0) 159 continue; 160 if ((cl_list = split_at(sv_list, ':')) == 0) { 161 tcpd_warn("missing \":\" separator"); 162 continue; 163 } 164 sh_cmd = split_at(cl_list, ':'); 165 match = list_match(sv_list, request, server_match) 166 && list_match(cl_list, request, client_match); 167 } 168 (void) fclose(fp); 169 } else if (errno != ENOENT) { 170 tcpd_warn("cannot open %s: %m", table); 171 } 172 if (match) { 173 if (hosts_access_verbose > 1) 174 syslog(LOG_DEBUG, "matched: %s line %d", 175 tcpd_context.file, tcpd_context.line); 176 if (sh_cmd) { 177 #ifdef PROCESS_OPTIONS 178 process_options(sh_cmd, request); 179 #else 180 char cmd[BUFSIZ]; 181 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request)); 182 #endif 183 } 184 } 185 tcpd_context = saved_context; 186 return (match); 187 } 188 189 /* list_match - match a request against a list of patterns with exceptions */ 190 191 static int list_match(list, request, match_fn) 192 char *list; 193 struct request_info *request; 194 int (*match_fn) __P((char *, struct request_info *)); 195 { 196 char *tok; 197 198 /* 199 * Process tokens one at a time. We have exhausted all possible matches 200 * when we reach an "EXCEPT" token or the end of the list. If we do find 201 * a match, look for an "EXCEPT" list and recurse to determine whether 202 * the match is affected by any exceptions. 203 */ 204 205 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) { 206 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */ 207 return (NO); 208 if (match_fn(tok, request)) { /* YES: look for exceptions */ 209 while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT")) 210 /* VOID */ ; 211 return (tok == 0 || list_match((char *) 0, request, match_fn) == 0); 212 } 213 } 214 return (NO); 215 } 216 217 /* server_match - match server information */ 218 219 static int server_match(tok, request) 220 char *tok; 221 struct request_info *request; 222 { 223 char *host; 224 225 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */ 226 return (string_match(tok, eval_daemon(request))); 227 } else { /* daemon@host */ 228 return (string_match(tok, eval_daemon(request)) 229 && host_match(host, request->server)); 230 } 231 } 232 233 /* client_match - match client information */ 234 235 static int client_match(tok, request) 236 char *tok; 237 struct request_info *request; 238 { 239 char *host; 240 241 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */ 242 return (host_match(tok, request->client)); 243 } else { /* user@host */ 244 return (host_match(host, request->client) 245 && string_match(tok, eval_user(request))); 246 } 247 } 248 249 /* host_match - match host name and/or address against pattern */ 250 251 static int host_match(tok, host) 252 char *tok; 253 struct host_info *host; 254 { 255 char *mask; 256 257 /* 258 * This code looks a little hairy because we want to avoid unnecessary 259 * hostname lookups. 260 * 261 * The KNOWN pattern requires that both address AND name be known; some 262 * patterns are specific to host names or to host addresses; all other 263 * patterns are satisfied when either the address OR the name match. 264 */ 265 266 if (tok[0] == '@') { /* netgroup: look it up */ 267 #ifdef NETGROUP 268 static char *mydomain = 0; 269 if (mydomain == 0) 270 yp_get_default_domain(&mydomain); 271 return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain)); 272 #else 273 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */ 274 return (NO); 275 #endif 276 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */ 277 char *name = eval_hostname(host); 278 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name)); 279 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */ 280 char *name = eval_hostname(host); 281 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name)); 282 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */ 283 return (masked_match(tok, mask, eval_hostaddr(host))); 284 } else { /* anything else */ 285 return (string_match(tok, eval_hostaddr(host)) 286 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host)))); 287 } 288 } 289 290 /* string_match - match string against pattern */ 291 292 static int string_match(tok, string) 293 char *tok; 294 char *string; 295 { 296 int n; 297 298 if (tok[0] == '.') { /* suffix */ 299 n = strlen(string) - strlen(tok); 300 return (n > 0 && STR_EQ(tok, string + n)); 301 } else if (STR_EQ(tok, "ALL")) { /* all: match any */ 302 return (YES); 303 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */ 304 return (STR_NE(string, unknown)); 305 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */ 306 return (STRN_EQ(tok, string, n)); 307 } else { /* exact match */ 308 return (STR_EQ(tok, string)); 309 } 310 } 311 312 /* masked_match - match address against netnumber/netmask */ 313 314 static int masked_match(net_tok, mask_tok, string) 315 char *net_tok; 316 char *mask_tok; 317 char *string; 318 { 319 unsigned long net; 320 unsigned long mask; 321 unsigned long addr; 322 323 /* 324 * Disallow forms other than dotted quad: the treatment that inet_addr() 325 * gives to forms with less than four components is inconsistent with the 326 * access control language. John P. Rouillard <rouilj (at) cs.umb.edu>. 327 */ 328 329 if ((addr = dot_quad_addr(string)) == INADDR_NONE) 330 return (NO); 331 if ((net = dot_quad_addr(net_tok)) == INADDR_NONE 332 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) { 333 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok); 334 return (NO); /* not tcpd_jump() */ 335 } 336 return ((addr & mask) == net); 337 } 338
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