usr/src/lib/libwrap/hosts_access.c

   1 /*
   2  * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
   3  * Use is subject to license terms.
   4  */
   5
   6 #pragma ident   "%Z%%M% %I%     %E% SMI"
   7
   8  /*
   9   * This module implements a simple access control language that is based on
  10   * host (or domain) names, NIS (host) netgroup names, IP addresses (or
  11   * network numbers) and daemon process names. When a match is found the
  12   * search is terminated, and depending on whether PROCESS_OPTIONS is defined,
  13   * a list of options is executed or an optional shell command is executed.
  14   *
  15   * Host and user names are looked up on demand, provided that suitable endpoint
  16   * information is available as sockaddr_in structures or TLI netbufs. As a
  17   * side effect, the pattern matching process may change the contents of
  18   * request structure fields.
  19   *
  20   * Diagnostics are reported through syslog(3).
  21   *
  22   * Compile with -DNETGROUP if your library provides support for netgroups.
  23   *
  24   * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
  25   */
  26
  27 #ifndef lint
  28 static char sccsid[] = "@(#) hosts_access.c 1.21 97/02/12 02:13:22";
  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 <rpcsvc/ypclnt.h>
  38 #include <netdb.h>
  39 #include <stdio.h>
  40 #include <stdlib.h>
  41 #include <unistd.h>
  42 #include <syslog.h>
  43 #include <ctype.h>
  44 #include <errno.h>
  45 #include <setjmp.h>
  46 #include <string.h>
  47
  48 extern char *fgets();
  49 extern int errno;
  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 HAVE_IPV6
  97 static void ipv6_mask();
  98 #endif
  99
 100 /* Size of logical line buffer. */
 101
 102 #define BUFLEN 2048
 103
 104 /* hosts_access - host access control facility */
 105
 106 int     hosts_access(request)
 107 struct request_info *request;
 108 {
 109     int     verdict;
 110
 111     /*
 112      * If the (daemon, client) pair is matched by an entry in the file
 113      * /etc/hosts.allow, access is granted. Otherwise, if the (daemon,
 114      * client) pair is matched by an entry in the file /etc/hosts.deny,
 115      * access is denied. Otherwise, access is granted. A non-existent
 116      * access-control file is treated as an empty file.
 117      *
 118      * After a rule has been matched, the optional language extensions may
 119      * decide to grant or refuse service anyway. Or, while a rule is being
 120      * processed, a serious error is found, and it seems better to play safe
 121      * and deny service. All this is done by jumping back into the
 122      * hosts_access() routine, bypassing the regular return from the
 123      * table_match() function calls below.
 124      */
 125
 126     if (resident <= 0)
 127         resident++;
 128     verdict = setjmp(tcpd_buf);
 129     if (verdict != 0)
 130         return (verdict == AC_PERMIT);
 131     if (table_match(hosts_allow_table, request))
 132         return (YES);
 133     if (table_match(hosts_deny_table, request))
 134         return (NO);
 135     return (YES);
 136 }
 137
 138 /* table_match - match table entries with (daemon, client) pair */
 139
 140 static int table_match(table, request)
 141 char   *table;
 142 struct request_info *request;
 143 {
 144     FILE   *fp;
 145     char    sv_list[BUFLEN];            /* becomes list of daemons */
 146     char   *cl_list;                    /* becomes list of clients */
 147     char   *sh_cmd;                     /* becomes optional shell command */
 148     int     match = NO;
 149     struct tcpd_context saved_context;
 150
 151     saved_context = tcpd_context;               /* stupid compilers */
 152
 153     /*
 154      * Between the fopen() and fclose() calls, avoid jumps that may cause
 155      * file descriptor leaks.
 156      */
 157
 158     if ((fp = fopen(table, "r")) != 0) {
 159         tcpd_context.file = table;
 160         tcpd_context.line = 0;
 161         while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) {
 162             if (sv_list[strlen(sv_list) - 1] != '\n') {
 163                 tcpd_warn("missing newline or line too long");
 164                 continue;
 165             }
 166             if (sv_list[0] == '#' || sv_list[strspn(sv_list, " \t\r\n")] == 0)
 167                 continue;
 168             if ((cl_list = split_at(skip_ipv6_addrs(sv_list), ':')) == 0) {
 169                 tcpd_warn("missing \":\" separator");
 170                 continue;
 171             }
 172             sh_cmd = split_at(skip_ipv6_addrs(cl_list), ':');
 173             match = list_match(sv_list, request, server_match)
 174                 && list_match(cl_list, request, client_match);
 175         }
 176         (void) fclose(fp);
 177     } else if (errno != ENOENT) {
 178         tcpd_warn("cannot open %s: %m", table);
 179     }
 180     if (match) {
 181         if (hosts_access_verbose > 1)
 182             syslog(LOG_DEBUG, "matched:  %s line %d",
 183                    tcpd_context.file, tcpd_context.line);
 184         if (sh_cmd) {
 185 #ifdef PROCESS_OPTIONS
 186             process_options(sh_cmd, request);
 187 #else
 188             char    cmd[BUFSIZ];
 189             shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request));
 190 #endif
 191         }
 192     }
 193     tcpd_context = saved_context;
 194     return (match);
 195 }
 196
 197 /* list_match - match a request against a list of patterns with exceptions */
 198
 199 static int list_match(list, request, match_fn)
 200 char   *list;
 201 struct request_info *request;
 202 int   (*match_fn) ();
 203 {
 204     char   *tok;
 205
 206     /*
 207      * Process tokens one at a time. We have exhausted all possible matches
 208      * when we reach an "EXCEPT" token or the end of the list. If we do find
 209      * a match, look for an "EXCEPT" list and recurse to determine whether
 210      * the match is affected by any exceptions.
 211      */
 212
 213     for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) {
 214         if (STR_EQ(tok, "EXCEPT"))              /* EXCEPT: give up */
 215             return (NO);
 216         if (match_fn(tok, request)) {           /* YES: look for exceptions */
 217             while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT"))
 218                  /* VOID */ ;
 219             return (tok == 0 || list_match((char *) 0, request, match_fn) == 0);
 220         }
 221     }
 222     return (NO);
 223 }
 224
 225 /* server_match - match server information */
 226
 227 static int server_match(tok, request)
 228 char   *tok;
 229 struct request_info *request;
 230 {
 231     char   *host;
 232
 233     if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */
 234         return (string_match(tok, eval_daemon(request)));
 235     } else {                                    /* daemon@host */
 236         return (string_match(tok, eval_daemon(request))
 237                 && host_match(host, request->server));
 238     }
 239 }
 240
 241 /* client_match - match client information */
 242
 243 static int client_match(tok, request)
 244 char   *tok;
 245 struct request_info *request;
 246 {
 247     char   *host;
 248
 249     if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */
 250         return (host_match(tok, request->client));
 251     } else {                                    /* user@host */
 252         return (host_match(host, request->client)
 253                 && string_match(tok, eval_user(request)));
 254     }
 255 }
 256
 257 /* host_match - match host name and/or address against pattern */
 258
 259 static int host_match(tok, host)
 260 char   *tok;
 261 struct host_info *host;
 262 {
 263     char   *mask;
 264
 265     /*
 266      * This code looks a little hairy because we want to avoid unnecessary
 267      * hostname lookups.
 268      *
 269      * The KNOWN pattern requires that both address AND name be known; some
 270      * patterns are specific to host names or to host addresses; all other
 271      * patterns are satisfied when either the address OR the name match.
 272      */
 273
 274     if (tok[0] == '@') {                        /* netgroup: look it up */
 275 #ifdef  NETGROUP
 276         static char *mydomain = 0;
 277         if (mydomain == 0)
 278             yp_get_default_domain(&mydomain);
 279         return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain));
 280 #else
 281         tcpd_warn("netgroup support is disabled");      /* not tcpd_jump() */
 282         return (NO);
 283 #endif
 284     } else if (STR_EQ(tok, "KNOWN")) {          /* check address and name */
 285         char   *name = eval_hostname(host);
 286         return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name));
 287     } else if (STR_EQ(tok, "LOCAL")) {          /* local: no dots in name */
 288         char   *name = eval_hostname(host);
 289         return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name));
 290 #ifdef HAVE_IPV6
 291     } else if (tok[0] == '[') {                 /* IPv6 address */
 292             struct in6_addr in6, hostin6, *hip;
 293             char *cbr;
 294             char *slash;
 295             int mask = IPV6_ABITS;
 296
 297             /*
 298              * In some cases we don't get the sockaddr, only the addr.
 299              * We use inet_pton to convert it to its binary representation
 300              * and match against that.
 301              */
 302             if (host->sin == NULL) {
 303                 if (host->addr == NULL ||
 304                     inet_pton(AF_INET6, host->addr, &hostin6) != 1) {
 305                     return (NO);
 306                 }
 307                 hip = &hostin6;
 308             } else {
 309                 if (SGFAM(host->sin) != AF_INET6)
 310                     return (NO);
 311                 hip = &host->sin->sg_sin6.sin6_addr;
 312             }
 313
 314             if (cbr = strchr(tok, ']'))
 315                 *cbr = '\0';
 316
 317             /*
 318              * A /nnn prefix specifies how many bits of the address we
 319              * need to check.
 320              */
 321             if (slash = strchr(tok, '/')) {
 322                 *slash = '\0';
 323                 mask = atoi(slash+1);
 324                 if (mask < 0 || mask > IPV6_ABITS) {
 325                     tcpd_warn("bad IP6 prefix specification");
 326                     return (NO);
 327                 }
 328                 /* Copy, because we need to modify it below */
 329                 if (host->sin != NULL) {
 330                     hostin6 = host->sin->sg_sin6.sin6_addr;
 331                     hip = &hostin6;
 332                 }
 333             }
 334
 335             if (cbr == NULL || inet_pton(AF_INET6, tok+1, &in6) != 1) {
 336                 tcpd_warn("bad IP6 address specification");
 337                 return (NO);
 338             }
 339             /*
 340              * Zero the bits we're not interested in in both addresses
 341              * then compare.  Note that we take a copy of the host info
 342              * in that case.
 343              */
 344             if (mask != IPV6_ABITS) {
 345                 ipv6_mask(&in6, mask);
 346                 ipv6_mask(hip, mask);
 347             }
 348             if (memcmp(&in6, hip, sizeof(in6)) == 0)
 349                 return (YES);
 350             return (NO);
 351 #endif
 352     } else if ((mask = split_at(tok, '/')) != 0) {      /* net/mask */
 353         return (masked_match(tok, mask, eval_hostaddr(host)));
 354     } else {                                    /* anything else */
 355         return (string_match(tok, eval_hostaddr(host))
 356             || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host))));
 357     }
 358 }
 359
 360 /* string_match - match string against pattern */
 361
 362 static int string_match(tok, string)
 363 char   *tok;
 364 char   *string;
 365 {
 366     int     n;
 367
 368     if (tok[0] == '.') {                        /* suffix */
 369         n = strlen(string) - strlen(tok);
 370         return (n > 0 && STR_EQ(tok, string + n));
 371     } else if (STR_EQ(tok, "ALL")) {            /* all: match any */
 372         return (YES);
 373     } else if (STR_EQ(tok, "KNOWN")) {          /* not unknown */
 374         return (STR_NE(string, unknown));
 375     } else if (tok[(n = strlen(tok)) - 1] == '.') {     /* prefix */
 376         return (STRN_EQ(tok, string, n));
 377     } else {                                    /* exact match */
 378         return (STR_EQ(tok, string));
 379     }
 380 }
 381
 382 /* masked_match - match address against netnumber/netmask */
 383
 384 static int masked_match(net_tok, mask_tok, string)
 385 char   *net_tok;
 386 char   *mask_tok;
 387 char   *string;
 388 {
 389     unsigned long net;
 390     unsigned long mask;
 391     unsigned long addr;
 392
 393     /*
 394      * Disallow forms other than dotted quad: the treatment that inet_addr()
 395      * gives to forms with less than four components is inconsistent with the
 396      * access control language. John P. Rouillard <rouilj@cs.umb.edu>.
 397      */
 398
 399     if ((addr = dot_quad_addr(string)) == INADDR_NONE)
 400         return (NO);
 401     if ((net = dot_quad_addr(net_tok)) == INADDR_NONE
 402         || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) {
 403         tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok);
 404         return (NO);                            /* not tcpd_jump() */
 405     }
 406     return ((addr & mask) == net);
 407 }
 408
 409 #ifdef HAVE_IPV6
 410 /*
 411  * Function that zeros all but the first "maskbits" bits of the IPV6 address
 412  * This function can be made generic by specifying an address length as
 413  * extra parameter. (So Wietse can implement 1.2.3.4/16)
 414  */
 415 static void ipv6_mask(in6p, maskbits)
 416 struct in6_addr *in6p;
 417 int maskbits;
 418 {
 419     uchar_t *p = (uchar_t*) in6p;
 420
 421     if (maskbits < 0 || maskbits >= IPV6_ABITS)
 422         return;
 423
 424     p += maskbits / 8;
 425     maskbits %= 8;
 426
 427     if (maskbits != 0)
 428         *p++ &= 0xff << (8 - maskbits);
 429
 430     while (p < (((uchar_t*) in6p)) + sizeof(*in6p))
 431         *p++ = 0;
 432 }
 433 #endif