contrib/tcp_wrappers/hosts_access.c

   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: src/contrib/tcp_wrappers/hosts_access.c,v 1.3.2.1 2000/07/18 08:34:54 ume Exp $
  20   * $DragonFly: src/contrib/tcp_wrappers/hosts_access.c,v 1.3 2005/04/29 00:37:08 joerg Exp $
  21   */
  22
  23 #ifndef lint
  24 static char sccsid[] = "@(#) hosts_access.c 1.21 97/02/12 02:13:22";
  25 #endif
  26
  27 /* System libraries. */
  28
  29 #include <sys/types.h>
  30 #ifdef INT32_T
  31     typedef uint32_t u_int32_t;
  32 #endif
  33 #include <sys/param.h>
  34 #ifdef INET6
  35 #include <sys/socket.h>
  36 #endif
  37 #include <netinet/in.h>
  38 #include <arpa/inet.h>
  39 #include <stdio.h>
  40 #include <syslog.h>
  41 #include <ctype.h>
  42 #include <errno.h>
  43 #include <setjmp.h>
  44 #include <string.h>
  45 #ifdef INET6
  46 #include <netdb.h>
  47 #endif
  48
  49 extern char *fgets();
  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 #ifdef NI_WITHSCOPEID
 370             if (pat.sin6_scope_id != 0 &&
 371                 addr.sin6_scope_id != pat.sin6_scope_id)
 372                 return NO;
 373 #endif
 374             return (!memcmp(&pat.sin6_addr, &addr.sin6_addr,
 375                             sizeof(struct in6_addr)));
 376             return (ret);
 377         }
 378 #endif
 379         return (STR_EQ(tok, string));
 380     }
 381 }
 382
 383 /* masked_match - match address against netnumber/netmask */
 384
 385 #ifdef INET6
 386 static int masked_match(net_tok, mask_tok, string)
 387 char   *net_tok;
 388 char   *mask_tok;
 389 char   *string;
 390 {
 391     return (masked_match4(net_tok, mask_tok, string) ||
 392             masked_match6(net_tok, mask_tok, string));
 393 }
 394
 395 static int masked_match4(net_tok, mask_tok, string)
 396 #else
 397 static int masked_match(net_tok, mask_tok, string)
 398 #endif
 399 char   *net_tok;
 400 char   *mask_tok;
 401 char   *string;
 402 {
 403 #ifdef INET6
 404     u_int32_t net;
 405     u_int32_t mask;
 406     u_int32_t addr;
 407 #else
 408     unsigned long net;
 409     unsigned long mask;
 410     unsigned long addr;
 411 #endif
 412
 413     /*
 414      * Disallow forms other than dotted quad: the treatment that inet_addr()
 415      * gives to forms with less than four components is inconsistent with the
 416      * access control language. John P. Rouillard <rouilj@cs.umb.edu>.
 417      */
 418
 419     if ((addr = dot_quad_addr(string)) == INADDR_NONE)
 420         return (NO);
 421     if ((net = dot_quad_addr(net_tok)) == INADDR_NONE
 422         || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) {
 423 #ifndef INET6
 424         tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok);
 425 #endif
 426         return (NO);                            /* not tcpd_jump() */
 427     }
 428     return ((addr & mask) == net);
 429 }
 430
 431 #ifdef INET6
 432 static int masked_match6(net_tok, mask_tok, string)
 433 char   *net_tok;
 434 char   *mask_tok;
 435 char   *string;
 436 {
 437     struct addrinfo hints, *res;
 438     struct sockaddr_in6 net, addr;
 439     u_int32_t mask;
 440     int len, mask_len, i = 0;
 441     char ch;
 442
 443     memset(&hints, 0, sizeof(hints));
 444     hints.ai_family = AF_INET6;
 445     hints.ai_socktype = SOCK_STREAM;
 446     hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST;
 447     if (getaddrinfo(string, NULL, &hints, &res) != 0)
 448         return NO;
 449     memcpy(&addr, res->ai_addr, sizeof(addr));
 450     freeaddrinfo(res);
 451
 452     if (IN6_IS_ADDR_V4MAPPED(&addr.sin6_addr)) {
 453         if ((*(u_int32_t *)&net.sin6_addr.s6_addr[12] = dot_quad_addr(net_tok)) == INADDR_NONE
 454          || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE)
 455             return (NO);
 456         return ((*(u_int32_t *)&addr.sin6_addr.s6_addr[12] & mask) == *(u_int32_t *)&net.sin6_addr.s6_addr[12]);
 457     }
 458
 459     /* match IPv6 address against netnumber/prefixlen */
 460     len = strlen(net_tok);
 461     if (*net_tok != '[' || net_tok[len - 1] != ']')
 462         return NO;
 463     ch = net_tok[len - 1];
 464     net_tok[len - 1] = '\0';
 465     if (getaddrinfo(net_tok + 1, NULL, &hints, &res) != 0) {
 466         net_tok[len - 1] = ch;
 467         return NO;
 468     }
 469     memcpy(&net, res->ai_addr, sizeof(net));
 470     freeaddrinfo(res);
 471     net_tok[len - 1] = ch;
 472     if ((mask_len = atoi(mask_tok)) < 0 || mask_len > 128)
 473         return NO;
 474
 475 #ifdef NI_WITHSCOPEID
 476     if (net.sin6_scope_id != 0 && addr.sin6_scope_id != net.sin6_scope_id)
 477         return NO;
 478 #endif
 479     while (mask_len > 0) {
 480         if (mask_len < 32) {
 481             mask = htonl(~(0xffffffff >> mask_len));
 482             if ((*(u_int32_t *)&addr.sin6_addr.s6_addr[i] & mask) != (*(u_int32_t *)&net.sin6_addr.s6_addr[i] & mask))
 483                 return NO;
 484             break;
 485         }
 486         if (*(u_int32_t *)&addr.sin6_addr.s6_addr[i] != *(u_int32_t *)&net.sin6_addr.s6_addr[i])
 487             return NO;
 488         i += 4;
 489         mask_len -= 32;
 490     }
 491     return YES;
 492 }
 493 #endif /* INET6 */