lib/libwrap/hosts_access.c

   1 /*      $NetBSD: hosts_access.c,v 1.20 2012/03/21 10:10:37 matt 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 1.20 2012/03/21 10:10:37 matt 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 const char   *hosts_allow_table = HOSTS_ALLOW;
  76 const 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(const char *, struct request_info *);
  88 static int list_match(char *, struct request_info *,
  89     int (*)(char *, struct request_info *));
  90 static int server_match(char *, struct request_info *);
  91 static int client_match(char *, struct request_info *);
  92 static int host_match(char *, struct host_info *);
  93 static int hostfile_match(char *, struct host_info *);
  94 static int rbl_match(char *, char *);
  95 static int string_match(char *, char *);
  96 static int masked_match(char *, char *, char *);
  97 static int masked_match4(char *, char *, char *);
  98 #ifdef INET6
  99 static int masked_match6(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
 109 hosts_access(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
 143 table_match(const char *table, 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 = NULL;              /* 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
 201 list_match(char *list, struct request_info *request,
 202     int (*match_fn)(char *, struct request_info *))
 203 {
 204     char   *tok;
 205     static char *last;
 206     int l;
 207
 208     /*
 209      * Process tokens one at a time. We have exhausted all possible matches
 210      * when we reach an "EXCEPT" token or the end of the list. If we do find
 211      * a match, look for an "EXCEPT" list and recurse to determine whether
 212      * the match is affected by any exceptions.
 213      */
 214
 215     for (tok = strtok_r(list, sep, &last); tok != 0;
 216       tok = strtok_r(NULL, sep, &last)) {
 217         if (STR_EQ(tok, "EXCEPT"))              /* EXCEPT: give up */
 218             return (NO);
 219         l = strlen(tok);
 220         if (*tok == '[' && tok[l - 1] == ']') {
 221             tok[l - 1] = '\0';
 222             tok++;
 223         }
 224         if (match_fn(tok, request)) {           /* YES: look for exceptions */
 225             while ((tok = strtok_r(NULL, sep, &last)) && STR_NE(tok, "EXCEPT"))
 226                  /* VOID */ ;
 227             return (tok == 0 || list_match(NULL, request, match_fn) == 0);
 228         }
 229     }
 230     return (NO);
 231 }
 232
 233 /* server_match - match server information */
 234
 235 static int
 236 server_match(char *tok, struct request_info *request)
 237 {
 238     char   *host;
 239
 240     if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */
 241         return (string_match(tok, eval_daemon(request)));
 242     } else {                                    /* daemon@host */
 243         return (string_match(tok, eval_daemon(request))
 244                 && host_match(host, request->server));
 245     }
 246 }
 247
 248 /* client_match - match client information */
 249
 250 static int
 251 client_match(char *tok, struct request_info *request)
 252 {
 253     char   *host;
 254
 255     if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */
 256         return (host_match(tok, request->client));
 257     } else {                                    /* user@host */
 258         return (host_match(host, request->client)
 259                 && string_match(tok, eval_user(request)));
 260     }
 261 }
 262
 263 /* host_match - match host name and/or address against pattern */
 264
 265 static int
 266 host_match(char *tok, struct host_info *host)
 267 {
 268     char   *mask;
 269
 270     /*
 271      * This code looks a little hairy because we want to avoid unnecessary
 272      * hostname lookups.
 273      *
 274      * The KNOWN pattern requires that both address AND name be known; some
 275      * patterns are specific to host names or to host addresses; all other
 276      * patterns are satisfied when either the address OR the name match.
 277      */
 278
 279     if (tok[0] == '@') {                        /* netgroup: look it up */
 280 #ifdef  NETGROUP
 281         static char *mydomain = 0;
 282         if (mydomain == 0)
 283             yp_get_default_domain(&mydomain);
 284         return (innetgr(tok + 1, eval_hostname(host), NULL, mydomain));
 285 #else
 286         tcpd_warn("netgroup support is disabled");      /* not tcpd_jump() */
 287         return (NO);
 288 #endif
 289     } else if (tok[0] == '/') {                 /* /file hack */
 290         return (hostfile_match(tok, host));
 291     } else if (STR_EQ(tok, "KNOWN")) {          /* check address and name */
 292         char   *name = eval_hostname(host);
 293         return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name));
 294     } else if (STR_EQ(tok, "LOCAL")) {          /* local: no dots in name */
 295         char   *name = eval_hostname(host);
 296         return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name));
 297     } else if (strncmp(tok, "{RBL}.", 6) == 0) { /* RBL lookup in domain */
 298         return rbl_match(tok+6, eval_hostaddr(host));
 299     } else if ((mask = split_at(tok, '/')) != 0) {      /* net/mask */
 300         return (masked_match(tok, mask, eval_hostaddr(host)));
 301     } else {                                    /* anything else */
 302         return (string_match(tok, eval_hostaddr(host))
 303             || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host))));
 304     }
 305 }
 306
 307 /* hostfile_match - look up host patterns from file */
 308
 309 static int
 310 hostfile_match(char *path, struct host_info *host)
 311 {
 312     char    tok[BUFSIZ];
 313     int     match = NO;
 314     FILE   *fp;
 315
 316     if ((fp = fopen(path, "r")) != 0) {
 317         while (fscanf(fp, "%s", tok) == 1 && !(match = host_match(tok, host)))
 318              /* void */ ;
 319         fclose(fp);
 320     } else if (errno != ENOENT) {
 321         tcpd_warn("open %s: %m", path);
 322     }
 323     return (match);
 324 }
 325
 326 /* rbl_match() - match host by looking up in RBL domain */
 327
 328 static int
 329 rbl_match(
 330     char   *rbl_domain,                 /* RBL domain */
 331     char   *rbl_hostaddr)               /* hostaddr */
 332 {
 333     char *rbl_name;
 334     unsigned long host_address;
 335     int ret = NO;
 336     size_t len = strlen(rbl_domain) + (4 * 4) + 2;
 337
 338     if (dot_quad_addr(rbl_hostaddr, &host_address) != 0) {
 339         tcpd_warn("unable to convert %s to address", rbl_hostaddr);
 340         return (NO);
 341     }
 342     host_address = ntohl(host_address);
 343     /*  construct the rbl name to look up */
 344     if ((rbl_name = malloc(len)) == NULL) {
 345         tcpd_jump("not enough memory to build RBL name for %s in %s", rbl_hostaddr, rbl_domain);
 346         /* NOTREACHED */
 347     }
 348     snprintf(rbl_name, len, "%u.%u.%u.%u.%s",
 349             (unsigned int) ((host_address) & 0xff),
 350             (unsigned int) ((host_address >> 8) & 0xff),
 351             (unsigned int) ((host_address >> 16) & 0xff),
 352             (unsigned int) ((host_address >> 24) & 0xff),
 353             rbl_domain);
 354     /* look it up */
 355     if (gethostbyname(rbl_name) != NULL) {
 356         /* successful lookup - they're on the RBL list */
 357         ret = YES;
 358     }
 359     free(rbl_name);
 360
 361     return ret;
 362 }
 363
 364 /* string_match - match string against pattern */
 365
 366 static int
 367 string_match(char *tok, char *string)
 368 {
 369     int     n;
 370
 371     if (tok[0] == '.') {                        /* suffix */
 372         n = strlen(string) - strlen(tok);
 373         return (n > 0 && STR_EQ(tok, string + n));
 374     } else if (STR_EQ(tok, "ALL")) {            /* all: match any */
 375         return (YES);
 376     } else if (STR_EQ(tok, "KNOWN")) {          /* not unknown */
 377         return (STR_NE(string, unknown));
 378     } else if (tok[(n = strlen(tok)) - 1] == '.') {     /* prefix */
 379         return (STRN_EQ(tok, string, n));
 380     } else {                                    /* exact match */
 381         return (STR_EQ(tok, string));
 382     }
 383 }
 384
 385 /* masked_match - match address against netnumber/netmask */
 386
 387 static int
 388 masked_match(char *net_tok, char *mask_tok, char *string)
 389 {
 390 #ifndef INET6
 391     return masked_match4(net_tok, mask_tok, string);
 392 #else
 393     /*
 394      * masked_match4() is kept just for supporting shortened IPv4 address form.
 395      * If we could get rid of shortened IPv4 form, we could just always use
 396      * masked_match6().
 397      */
 398     if (dot_quad_addr(net_tok, NULL) != -1 &&
 399         dot_quad_addr(mask_tok, NULL) != -1 &&
 400         dot_quad_addr(string, NULL) != -1) {
 401         return masked_match4(net_tok, mask_tok, string);
 402     } else
 403         return masked_match6(net_tok, mask_tok, string);
 404 #endif
 405 }
 406
 407 static int
 408 masked_match4(char *net_tok, char *mask_tok, char *string)
 409 {
 410     unsigned long net;
 411     unsigned long mask;
 412     unsigned long addr;
 413
 414     /*
 415      * Disallow forms other than dotted quad: the treatment that inet_addr()
 416      * gives to forms with less than four components is inconsistent with the
 417      * access control language. John P. Rouillard <rouilj@cs.umb.edu>.
 418      */
 419
 420     if (dot_quad_addr(string, &addr) != 0)
 421         return (NO);
 422     if (dot_quad_addr(net_tok, &net) != 0 ||
 423         dot_quad_addr(mask_tok, &mask) != 0) {
 424         tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok);
 425         return (NO);                            /* not tcpd_jump() */
 426     }
 427
 428     if ((net & ~mask) != 0)
 429         tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok);
 430
 431     return ((addr & mask) == net);
 432 }
 433
 434 #ifdef INET6
 435 static int
 436 masked_match6(char *net_tok, char *mask_tok, char *string)
 437 {
 438     union {
 439         struct sockaddr sa;
 440         struct sockaddr_in sin;
 441         struct sockaddr_in6 sin6;
 442     } net, mask, addr;
 443     struct addrinfo hints, *res;
 444     unsigned long masklen;
 445     char *ep;
 446     size_t i;
 447     char *np, *mp, *ap;
 448     size_t alen;
 449
 450     memset(&hints, 0, sizeof(hints));
 451     hints.ai_family = PF_UNSPEC;
 452     hints.ai_socktype = SOCK_DGRAM;     /*dummy*/
 453     hints.ai_flags = AI_NUMERICHOST;
 454     if (getaddrinfo(net_tok, "0", &hints, &res) == 0) {
 455         if (res->ai_addrlen > sizeof(net) || res->ai_next) {
 456             freeaddrinfo(res);
 457             return NO;
 458         }
 459         memcpy(&net, res->ai_addr, res->ai_addrlen);
 460         freeaddrinfo(res);
 461     } else
 462         return NO;
 463
 464     memset(&hints, 0, sizeof(hints));
 465     hints.ai_family = net.sa.sa_family;
 466     hints.ai_socktype = SOCK_DGRAM;     /*dummy*/
 467     hints.ai_flags = AI_NUMERICHOST;
 468     ep = NULL;
 469     if (getaddrinfo(mask_tok, "0", &hints, &res) == 0) {
 470         if (res->ai_family == AF_INET6 &&
 471             ((struct sockaddr_in6 *)res->ai_addr)->sin6_scope_id) {
 472             freeaddrinfo(res);
 473             return NO;
 474         }
 475         if (res->ai_addrlen > sizeof(mask) || res->ai_next) {
 476             freeaddrinfo(res);
 477             return NO;
 478         }
 479         memcpy(&mask, res->ai_addr, res->ai_addrlen);
 480         freeaddrinfo(res);
 481     } else {
 482         ep = NULL;
 483         masklen = strtoul(mask_tok, &ep, 10);
 484         if (ep && !*ep) {
 485             memset(&mask, 0, sizeof(mask));
 486             mask.sa.sa_family = net.sa.sa_family;
 487             mask.sa.sa_len = net.sa.sa_len;
 488             switch (mask.sa.sa_family) {
 489             case AF_INET:
 490                 mp = (char *)&mask.sin.sin_addr;
 491                 alen = sizeof(mask.sin.sin_addr);
 492                 break;
 493             case AF_INET6:
 494                 mp = (char *)&mask.sin6.sin6_addr;
 495                 alen = sizeof(mask.sin6.sin6_addr);
 496                 break;
 497             default:
 498                 return NO;
 499             }
 500             if (masklen / 8 > alen)
 501                 return NO;
 502             memset(mp, 0xff, masklen / 8);
 503             if (masklen % 8)
 504                 mp[masklen / 8] = 0xff00 >> (masklen % 8);
 505         } else
 506             return NO;
 507     }
 508
 509     memset(&hints, 0, sizeof(hints));
 510     hints.ai_family = PF_UNSPEC;
 511     hints.ai_socktype = SOCK_DGRAM;     /*dummy*/
 512     hints.ai_flags = AI_NUMERICHOST;
 513     if (getaddrinfo(string, "0", &hints, &res) == 0) {
 514         if (res->ai_addrlen > sizeof(addr) || res->ai_next) {
 515             freeaddrinfo(res);
 516             return NO;
 517         }
 518         /* special case - IPv4 mapped address */
 519         if (net.sa.sa_family == AF_INET && res->ai_family == AF_INET6 &&
 520             IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)res->ai_addr)->sin6_addr)) {
 521             memset(&addr, 0, sizeof(addr));
 522             addr.sa.sa_family = net.sa.sa_family;
 523             addr.sa.sa_len = net.sa.sa_len;
 524             memcpy(&addr.sin.sin_addr,
 525                 &((struct sockaddr_in6 *)res->ai_addr)->sin6_addr.s6_addr[12],
 526                 sizeof(addr.sin.sin_addr));
 527         } else
 528             memcpy(&addr, res->ai_addr, res->ai_addrlen);
 529         freeaddrinfo(res);
 530     } else
 531         return NO;
 532
 533     if (net.sa.sa_family != mask.sa.sa_family ||
 534         net.sa.sa_family != addr.sa.sa_family) {
 535         return NO;
 536     }
 537
 538     switch (net.sa.sa_family) {
 539     case AF_INET:
 540         np = (char *)&net.sin.sin_addr;
 541         mp = (char *)&mask.sin.sin_addr;
 542         ap = (char *)&addr.sin.sin_addr;
 543         alen = sizeof(net.sin.sin_addr);
 544         break;
 545     case AF_INET6:
 546         np = (char *)&net.sin6.sin6_addr;
 547         mp = (char *)&mask.sin6.sin6_addr;
 548         ap = (char *)&addr.sin6.sin6_addr;
 549         alen = sizeof(net.sin6.sin6_addr);
 550         break;
 551     default:
 552         return NO;
 553     }
 554
 555     for (i = 0; i < alen; i++)
 556         if (np[i] & ~mp[i]) {
 557             tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok);
 558             break;
 559         }
 560
 561     for (i = 0; i < alen; i++)
 562         ap[i] &= mp[i];
 563
 564     if (addr.sa.sa_family == AF_INET6 && addr.sin6.sin6_scope_id &&
 565         addr.sin6.sin6_scope_id != net.sin6.sin6_scope_id)
 566         return NO;
 567     return (memcmp(ap, np, alen) == 0);
 568 }
 569 #endif