lib/libwrap/hosts_access.c

   1 /*      $NetBSD: hosts_access.c,v 1.18 2006/01/08 17:20:28 jdc 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 1.21 97/02/12 02:13:22";
  26 #else
  27 __RCSID("$NetBSD: hosts_access.c,v 1.18 2006/01/08 17:20:28 jdc Exp $");
  28 #endif
  29 #endif
  30
  31 /* System libraries. */
  32
  33 #include <sys/types.h>
  34 #include <sys/param.h>
  35 #ifdef INET6
  36 #include <sys/socket.h>
  37 #endif
  38 #include <netinet/in.h>
  39 #include <arpa/inet.h>
  40 #include <stdio.h>
  41 #include <stdlib.h>
  42 #include <syslog.h>
  43 #include <ctype.h>
  44 #include <errno.h>
  45 #include <setjmp.h>
  46 #include <string.h>
  47 #include <netdb.h>
  48 #ifdef  NETGROUP
  49 #include <netgroup.h>
  50 #include <rpcsvc/ypclnt.h>
  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 __P((char *, struct request_info *));
  88 static int list_match __P((char *, struct request_info *,
  89     int (*)(char *, struct request_info *)));
  90 static int server_match __P((char *, struct request_info *));
  91 static int client_match __P((char *, struct request_info *));
  92 static int host_match __P((char *, struct host_info *));
  93 static int hostfile_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 static int masked_match4 __P((char *, char *, char *));
  98 #ifdef INET6
  99 static int masked_match6 __P((char *, char *, char *));
 100 #endif
 101
 102 /* Size of logical line buffer. */
 103
 104 #define BUFLEN 2048
 105
 106 /* hosts_access - host access control facility */
 107
 108 int     hosts_access(request)
 109 struct request_info *request;
 110 {
 111     int     verdict;
 112
 113     /*
 114      * If the (daemon, client) pair is matched by an entry in the file
 115      * /etc/hosts.allow, access is granted. Otherwise, if the (daemon,
 116      * client) pair is matched by an entry in the file /etc/hosts.deny,
 117      * access is denied. Otherwise, access is granted. A non-existent
 118      * access-control file is treated as an empty file.
 119      *
 120      * After a rule has been matched, the optional language extensions may
 121      * decide to grant or refuse service anyway. Or, while a rule is being
 122      * processed, a serious error is found, and it seems better to play safe
 123      * and deny service. All this is done by jumping back into the
 124      * hosts_access() routine, bypassing the regular return from the
 125      * table_match() function calls below.
 126      */
 127
 128     if (resident <= 0)
 129         resident++;
 130     verdict = setjmp(tcpd_buf);
 131     if (verdict != 0)
 132         return (verdict == AC_PERMIT);
 133     if (table_match(hosts_allow_table, request))
 134         return (YES);
 135     if (table_match(hosts_deny_table, request))
 136         return (NO);
 137     return (YES);
 138 }
 139
 140 /* table_match - match table entries with (daemon, client) pair */
 141
 142 static int table_match(table, request)
 143 char   *table;
 144 struct request_info *request;
 145 {
 146     FILE   *fp;
 147     char    sv_list[BUFLEN];            /* becomes list of daemons */
 148     char   *cl_list;                    /* becomes list of clients */
 149     char   *sh_cmd = NULL;              /* becomes optional shell command */
 150     int     match = NO;
 151     struct tcpd_context saved_context;
 152
 153     saved_context = tcpd_context;               /* stupid compilers */
 154
 155     /*
 156      * Between the fopen() and fclose() calls, avoid jumps that may cause
 157      * file descriptor leaks.
 158      */
 159
 160     if ((fp = fopen(table, "r")) != 0) {
 161         tcpd_context.file = table;
 162         tcpd_context.line = 0;
 163         while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) {
 164             if (sv_list[strlen(sv_list) - 1] != '\n') {
 165                 tcpd_warn("missing newline or line too long");
 166                 continue;
 167             }
 168             if (sv_list[0] == '#' || sv_list[strspn(sv_list, " \t\r\n")] == 0)
 169                 continue;
 170             if ((cl_list = split_at(sv_list, ':')) == 0) {
 171                 tcpd_warn("missing \":\" separator");
 172                 continue;
 173             }
 174             sh_cmd = split_at(cl_list, ':');
 175             match = list_match(sv_list, request, server_match)
 176                 && list_match(cl_list, request, client_match);
 177         }
 178         (void) fclose(fp);
 179     } else if (errno != ENOENT) {
 180         tcpd_warn("cannot open %s: %m", table);
 181     }
 182     if (match) {
 183         if (hosts_access_verbose > 1)
 184             syslog(LOG_DEBUG, "matched:  %s line %d",
 185                    tcpd_context.file, tcpd_context.line);
 186         if (sh_cmd) {
 187 #ifdef PROCESS_OPTIONS
 188             process_options(sh_cmd, request);
 189 #else
 190             char    cmd[BUFSIZ];
 191             shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request));
 192 #endif
 193         }
 194     }
 195     tcpd_context = saved_context;
 196     return (match);
 197 }
 198
 199 /* list_match - match a request against a list of patterns with exceptions */
 200
 201 static int list_match(list, request, match_fn)
 202 char   *list;
 203 struct request_info *request;
 204 int   (*match_fn) __P((char *, struct request_info *));
 205 {
 206     char   *tok;
 207     static char *last;
 208     int l;
 209
 210     /*
 211      * Process tokens one at a time. We have exhausted all possible matches
 212      * when we reach an "EXCEPT" token or the end of the list. If we do find
 213      * a match, look for an "EXCEPT" list and recurse to determine whether
 214      * the match is affected by any exceptions.
 215      */
 216
 217     for (tok = strtok_r(list, sep, &last); tok != 0;
 218       tok = strtok_r(NULL, sep, &last)) {
 219         if (STR_EQ(tok, "EXCEPT"))              /* EXCEPT: give up */
 220             return (NO);
 221         l = strlen(tok);
 222         if (*tok == '[' && tok[l - 1] == ']') {
 223             tok[l - 1] = '\0';
 224             tok++;
 225         }
 226         if (match_fn(tok, request)) {           /* YES: look for exceptions */
 227             while ((tok = strtok_r(NULL, sep, &last)) && STR_NE(tok, "EXCEPT"))
 228                  /* VOID */ ;
 229             return (tok == 0 || list_match(NULL, request, match_fn) == 0);
 230         }
 231     }
 232     return (NO);
 233 }
 234
 235 /* server_match - match server information */
 236
 237 static int server_match(tok, request)
 238 char   *tok;
 239 struct request_info *request;
 240 {
 241     char   *host;
 242
 243     if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */
 244         return (string_match(tok, eval_daemon(request)));
 245     } else {                                    /* daemon@host */
 246         return (string_match(tok, eval_daemon(request))
 247                 && host_match(host, request->server));
 248     }
 249 }
 250
 251 /* client_match - match client information */
 252
 253 static int client_match(tok, request)
 254 char   *tok;
 255 struct request_info *request;
 256 {
 257     char   *host;
 258
 259     if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */
 260         return (host_match(tok, request->client));
 261     } else {                                    /* user@host */
 262         return (host_match(host, request->client)
 263                 && string_match(tok, eval_user(request)));
 264     }
 265 }
 266
 267 /* host_match - match host name and/or address against pattern */
 268
 269 static int host_match(tok, host)
 270 char   *tok;
 271 struct host_info *host;
 272 {
 273     char   *mask;
 274
 275     /*
 276      * This code looks a little hairy because we want to avoid unnecessary
 277      * hostname lookups.
 278      *
 279      * The KNOWN pattern requires that both address AND name be known; some
 280      * patterns are specific to host names or to host addresses; all other
 281      * patterns are satisfied when either the address OR the name match.
 282      */
 283
 284     if (tok[0] == '@') {                        /* netgroup: look it up */
 285 #ifdef  NETGROUP
 286         static char *mydomain = 0;
 287         if (mydomain == 0)
 288             yp_get_default_domain(&mydomain);
 289         return (innetgr(tok + 1, eval_hostname(host), NULL, mydomain));
 290 #else
 291         tcpd_warn("netgroup support is disabled");      /* not tcpd_jump() */
 292         return (NO);
 293 #endif
 294     } else if (tok[0] == '/') {                 /* /file hack */
 295         return (hostfile_match(tok, host));
 296     } else if (STR_EQ(tok, "KNOWN")) {          /* check address and name */
 297         char   *name = eval_hostname(host);
 298         return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name));
 299     } else if (STR_EQ(tok, "LOCAL")) {          /* local: no dots in name */
 300         char   *name = eval_hostname(host);
 301         return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name));
 302     } else if (strncmp(tok, "{RBL}.", 6) == 0) { /* RBL lookup in domain */
 303         return rbl_match(tok+6, eval_hostaddr(host));
 304     } else if ((mask = split_at(tok, '/')) != 0) {      /* net/mask */
 305         return (masked_match(tok, mask, eval_hostaddr(host)));
 306     } else {                                    /* anything else */
 307         return (string_match(tok, eval_hostaddr(host))
 308             || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host))));
 309     }
 310 }
 311
 312 /* hostfile_match - look up host patterns from file */
 313
 314 static int hostfile_match(path, host)
 315 char   *path;
 316 struct host_info *host;
 317 {
 318     char    tok[BUFSIZ];
 319     int     match = NO;
 320     FILE   *fp;
 321
 322     if ((fp = fopen(path, "r")) != 0) {
 323         while (fscanf(fp, "%s", tok) == 1 && !(match = host_match(tok, host)))
 324              /* void */ ;
 325         fclose(fp);
 326     } else if (errno != ENOENT) {
 327         tcpd_warn("open %s: %m", path);
 328     }
 329     return (match);
 330 }
 331
 332 /* rbl_match() - match host by looking up in RBL domain */
 333
 334 static int rbl_match(rbl_domain, rbl_hostaddr)
 335 char   *rbl_domain;                             /* RBL domain */
 336 char   *rbl_hostaddr;                           /* hostaddr */
 337 {
 338     char *rbl_name;
 339     unsigned long host_address;
 340     int ret = NO;
 341     size_t len = strlen(rbl_domain) + (4 * 4) + 2;
 342
 343     if (dot_quad_addr(rbl_hostaddr, &host_address) != 0) {
 344         tcpd_warn("unable to convert %s to address", rbl_hostaddr);
 345         return (NO);
 346     }
 347     host_address = ntohl(host_address);
 348     /*  construct the rbl name to look up */
 349     if ((rbl_name = malloc(len)) == NULL) {
 350         tcpd_jump("not enough memory to build RBL name for %s in %s", rbl_hostaddr, rbl_domain);
 351         /* NOTREACHED */
 352     }
 353     snprintf(rbl_name, len, "%u.%u.%u.%u.%s",
 354             (unsigned int) ((host_address) & 0xff),
 355             (unsigned int) ((host_address >> 8) & 0xff),
 356             (unsigned int) ((host_address >> 16) & 0xff),
 357             (unsigned int) ((host_address >> 24) & 0xff),
 358             rbl_domain);
 359     /* look it up */
 360     if (gethostbyname(rbl_name) != NULL) {
 361         /* successful lookup - they're on the RBL list */
 362         ret = YES;
 363     }
 364     free(rbl_name);
 365
 366     return ret;
 367 }
 368
 369 /* string_match - match string against pattern */
 370
 371 static int string_match(tok, string)
 372 char   *tok;
 373 char   *string;
 374 {
 375     int     n;
 376
 377     if (tok[0] == '.') {                        /* suffix */
 378         n = strlen(string) - strlen(tok);
 379         return (n > 0 && STR_EQ(tok, string + n));
 380     } else if (STR_EQ(tok, "ALL")) {            /* all: match any */
 381         return (YES);
 382     } else if (STR_EQ(tok, "KNOWN")) {          /* not unknown */
 383         return (STR_NE(string, unknown));
 384     } else if (tok[(n = strlen(tok)) - 1] == '.') {     /* prefix */
 385         return (STRN_EQ(tok, string, n));
 386     } else {                                    /* exact match */
 387         return (STR_EQ(tok, string));
 388     }
 389 }
 390
 391 /* masked_match - match address against netnumber/netmask */
 392
 393 static int masked_match(net_tok, mask_tok, string)
 394 char   *net_tok;
 395 char   *mask_tok;
 396 char   *string;
 397 {
 398 #ifndef INET6
 399     return masked_match4(net_tok, mask_tok, string);
 400 #else
 401     /*
 402      * masked_match4() is kept just for supporting shortened IPv4 address form.
 403      * If we could get rid of shortened IPv4 form, we could just always use
 404      * masked_match6().
 405      */
 406     if (dot_quad_addr(net_tok, NULL) != INADDR_NONE &&
 407         dot_quad_addr(mask_tok, NULL) != INADDR_NONE &&
 408         dot_quad_addr(string, NULL) != INADDR_NONE) {
 409         return masked_match4(net_tok, mask_tok, string);
 410     } else
 411         return masked_match6(net_tok, mask_tok, string);
 412 #endif
 413 }
 414
 415 static int masked_match4(net_tok, mask_tok, string)
 416 char   *net_tok;
 417 char   *mask_tok;
 418 char   *string;
 419 {
 420     unsigned long net;
 421     unsigned long mask;
 422     unsigned long addr;
 423
 424     /*
 425      * Disallow forms other than dotted quad: the treatment that inet_addr()
 426      * gives to forms with less than four components is inconsistent with the
 427      * access control language. John P. Rouillard <rouilj@cs.umb.edu>.
 428      */
 429
 430     if (dot_quad_addr(string, &addr) != 0)
 431         return (NO);
 432     if (dot_quad_addr(net_tok, &net) != 0 ||
 433         dot_quad_addr(mask_tok, &mask) != 0) {
 434         tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok);
 435         return (NO);                            /* not tcpd_jump() */
 436     }
 437
 438     if ((net & ~mask) != 0)
 439         tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok);
 440
 441     return ((addr & mask) == net);
 442 }
 443
 444 #ifdef INET6
 445 static int masked_match6(net_tok, mask_tok, string)
 446 char   *net_tok;
 447 char   *mask_tok;
 448 char   *string;
 449 {
 450     union {
 451         struct sockaddr sa;
 452         struct sockaddr_in sin;
 453         struct sockaddr_in6 sin6;
 454     } net, mask, addr;
 455     struct addrinfo hints, *res;
 456     unsigned long masklen;
 457     char *ep;
 458     int i;
 459     char *np, *mp, *ap;
 460     int alen;
 461
 462     memset(&hints, 0, sizeof(hints));
 463     hints.ai_family = PF_UNSPEC;
 464     hints.ai_socktype = SOCK_DGRAM;     /*dummy*/
 465     hints.ai_flags = AI_NUMERICHOST;
 466     if (getaddrinfo(net_tok, "0", &hints, &res) == 0) {
 467         if (res->ai_addrlen > sizeof(net) || res->ai_next) {
 468             freeaddrinfo(res);
 469             return NO;
 470         }
 471         memcpy(&net, res->ai_addr, res->ai_addrlen);
 472         freeaddrinfo(res);
 473     } else
 474         return NO;
 475
 476     memset(&hints, 0, sizeof(hints));
 477     hints.ai_family = net.sa.sa_family;
 478     hints.ai_socktype = SOCK_DGRAM;     /*dummy*/
 479     hints.ai_flags = AI_NUMERICHOST;
 480     ep = NULL;
 481     if (getaddrinfo(mask_tok, "0", &hints, &res) == 0) {
 482         if (res->ai_family == AF_INET6 &&
 483             ((struct sockaddr_in6 *)res->ai_addr)->sin6_scope_id) {
 484             freeaddrinfo(res);
 485             return NO;
 486         }
 487         if (res->ai_addrlen > sizeof(mask) || res->ai_next) {
 488             freeaddrinfo(res);
 489             return NO;
 490         }
 491         memcpy(&mask, res->ai_addr, res->ai_addrlen);
 492         freeaddrinfo(res);
 493     } else {
 494         ep = NULL;
 495         masklen = strtoul(mask_tok, &ep, 10);
 496         if (ep && !*ep) {
 497             memset(&mask, 0, sizeof(mask));
 498             mask.sa.sa_family = net.sa.sa_family;
 499             mask.sa.sa_len = net.sa.sa_len;
 500             switch (mask.sa.sa_family) {
 501             case AF_INET:
 502                 mp = (char *)&mask.sin.sin_addr;
 503                 alen = sizeof(mask.sin.sin_addr);
 504                 break;
 505             case AF_INET6:
 506                 mp = (char *)&mask.sin6.sin6_addr;
 507                 alen = sizeof(mask.sin6.sin6_addr);
 508                 break;
 509             default:
 510                 return NO;
 511             }
 512             if (masklen / 8 > alen)
 513                 return NO;
 514             memset(mp, 0xff, masklen / 8);
 515             if (masklen % 8)
 516                 mp[masklen / 8] = 0xff00 >> (masklen % 8);
 517         } else
 518             return NO;
 519     }
 520
 521     memset(&hints, 0, sizeof(hints));
 522     hints.ai_family = PF_UNSPEC;
 523     hints.ai_socktype = SOCK_DGRAM;     /*dummy*/
 524     hints.ai_flags = AI_NUMERICHOST;
 525     if (getaddrinfo(string, "0", &hints, &res) == 0) {
 526         if (res->ai_addrlen > sizeof(addr) || res->ai_next) {
 527             freeaddrinfo(res);
 528             return NO;
 529         }
 530         /* special case - IPv4 mapped address */
 531         if (net.sa.sa_family == AF_INET && res->ai_family == AF_INET6 &&
 532             IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)res->ai_addr)->sin6_addr)) {
 533             memset(&addr, 0, sizeof(addr));
 534             addr.sa.sa_family = net.sa.sa_family;
 535             addr.sa.sa_len = net.sa.sa_len;
 536             memcpy(&addr.sin.sin_addr,
 537                 &((struct sockaddr_in6 *)res->ai_addr)->sin6_addr.s6_addr[12],
 538                 sizeof(addr.sin.sin_addr));
 539         } else
 540             memcpy(&addr, res->ai_addr, res->ai_addrlen);
 541         freeaddrinfo(res);
 542     } else
 543         return NO;
 544
 545     if (net.sa.sa_family != mask.sa.sa_family ||
 546         net.sa.sa_family != addr.sa.sa_family) {
 547         return NO;
 548     }
 549
 550     switch (net.sa.sa_family) {
 551     case AF_INET:
 552         np = (char *)&net.sin.sin_addr;
 553         mp = (char *)&mask.sin.sin_addr;
 554         ap = (char *)&addr.sin.sin_addr;
 555         alen = sizeof(net.sin.sin_addr);
 556         break;
 557     case AF_INET6:
 558         np = (char *)&net.sin6.sin6_addr;
 559         mp = (char *)&mask.sin6.sin6_addr;
 560         ap = (char *)&addr.sin6.sin6_addr;
 561         alen = sizeof(net.sin6.sin6_addr);
 562         break;
 563     default:
 564         return NO;
 565     }
 566
 567     for (i = 0; i < alen; i++)
 568         if (np[i] & ~mp[i]) {
 569             tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok);
 570             break;
 571         }
 572
 573     for (i = 0; i < alen; i++)
 574         ap[i] &= mp[i];
 575
 576     if (addr.sa.sa_family == AF_INET6 && addr.sin6.sin6_scope_id &&
 577         addr.sin6.sin6_scope_id != net.sin6.sin6_scope_id)
 578         return NO;
 579     return (memcmp(ap, np, alen) == 0);
 580 }
 581 #endif