usr/src/lib/libwrap/options.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   * General skeleton for adding options to the access control language. The
  10   * features offered by this module are documented in the hosts_options(5)
  11   * manual page (source file: hosts_options.5, "nroff -man" format).
  12   *
  13   * Notes and warnings for those who want to add features:
  14   *
  15   * In case of errors, abort options processing and deny access. There are too
  16   * many irreversible side effects to make error recovery feasible. For
  17   * example, it makes no sense to continue after we have already changed the
  18   * userid.
  19   *
  20   * In case of errors, do not terminate the process: the routines might be
  21   * called from a long-running daemon that should run forever. Instead, call
  22   * tcpd_jump() which does a non-local goto back into the hosts_access()
  23   * routine.
  24   *
  25   * In case of severe errors, use clean_exit() instead of directly calling
  26   * exit(), or the inetd may loop on an UDP request.
  27   *
  28   * In verification mode (for example, with the "tcpdmatch" command) the
  29   * "dry_run" flag is set. In this mode, an option function should just "say"
  30   * what it is going to do instead of really doing it.
  31   *
  32   * Some option functions do not return (for example, the twist option passes
  33   * control to another program). In verification mode (dry_run flag is set)
  34   * such options should clear the "dry_run" flag to inform the caller of this
  35   * course of action.
  36   */
  37
  38 static char sccsid[] = "@(#) options.c 1.17 96/02/11 17:01:31";
  39
  40 /* System libraries. */
  41
  42 #include <sys/types.h>
  43 #include <sys/param.h>
  44 #include <sys/socket.h>
  45 #include <sys/stat.h>
  46 #include <netinet/in.h>
  47 #include <netdb.h>
  48 #include <stdio.h>
  49 #include <stdlib.h>
  50 #include <unistd.h>
  51 #include <syslog.h>
  52 #include <pwd.h>
  53 #include <grp.h>
  54 #include <ctype.h>
  55 #include <setjmp.h>
  56 #include <string.h>
  57
  58 #ifndef MAXPATHNAMELEN
  59 #define MAXPATHNAMELEN  BUFSIZ
  60 #endif
  61
  62 /* Local stuff. */
  63
  64 #include "tcpd.h"
  65
  66 /* Options runtime support. */
  67
  68 int     dry_run = 0;                    /* flag set in verification mode */
  69 extern jmp_buf tcpd_buf;                /* tcpd_jump() support */
  70
  71 /* Options parser support. */
  72
  73 static char whitespace_eq[] = "= \t\r\n";
  74 #define whitespace (whitespace_eq + 1)
  75
  76 static char *get_field();               /* chew :-delimited field off string */
  77 static char *chop_string();             /* strip leading and trailing blanks */
  78
  79 /* List of functions that implement the options. Add yours here. */
  80
  81 static void user_option();              /* execute "user name.group" option */
  82 static void group_option();             /* execute "group name" option */
  83 static void umask_option();             /* execute "umask mask" option */
  84 static void linger_option();            /* execute "linger time" option */
  85 static void keepalive_option();         /* execute "keepalive" option */
  86 static void spawn_option();             /* execute "spawn command" option */
  87 static void twist_option();             /* execute "twist command" option */
  88 static void rfc931_option();            /* execute "rfc931" option */
  89 static void setenv_option();            /* execute "setenv name value" */
  90 static void nice_option();              /* execute "nice" option */
  91 static void severity_option();          /* execute "severity value" */
  92 static void allow_option();             /* execute "allow" option */
  93 static void deny_option();              /* execute "deny" option */
  94 static void banners_option();           /* execute "banners path" option */
  95
  96 /* Structure of the options table. */
  97
  98 struct option {
  99     char   *name;                       /* keyword name, case is ignored */
 100     void  (*func) ();                   /* function that does the real work */
 101     int     flags;                      /* see below... */
 102 };
 103
 104 #define NEED_ARG        (1<<1)          /* option requires argument */
 105 #define USE_LAST        (1<<2)          /* option must be last */
 106 #define OPT_ARG         (1<<3)          /* option has optional argument */
 107 #define EXPAND_ARG      (1<<4)          /* do %x expansion on argument */
 108
 109 #define need_arg(o)     ((o)->flags & NEED_ARG)
 110 #define opt_arg(o)      ((o)->flags & OPT_ARG)
 111 #define permit_arg(o)   ((o)->flags & (NEED_ARG | OPT_ARG))
 112 #define use_last(o)     ((o)->flags & USE_LAST)
 113 #define expand_arg(o)   ((o)->flags & EXPAND_ARG)
 114
 115 /* List of known keywords. Add yours here. */
 116
 117 static struct option option_table[] = {
 118     "user", user_option, NEED_ARG,
 119     "group", group_option, NEED_ARG,
 120     "umask", umask_option, NEED_ARG,
 121     "linger", linger_option, NEED_ARG,
 122     "keepalive", keepalive_option, 0,
 123     "spawn", spawn_option, NEED_ARG | EXPAND_ARG,
 124     "twist", twist_option, NEED_ARG | EXPAND_ARG | USE_LAST,
 125     "rfc931", rfc931_option, OPT_ARG,
 126     "setenv", setenv_option, NEED_ARG | EXPAND_ARG,
 127     "nice", nice_option, OPT_ARG,
 128     "severity", severity_option, NEED_ARG,
 129     "allow", allow_option, USE_LAST,
 130     "deny", deny_option, USE_LAST,
 131     "banners", banners_option, NEED_ARG,
 132     0,
 133 };
 134
 135 /* process_options - process access control options */
 136
 137 void    process_options(options, request)
 138 char   *options;
 139 struct request_info *request;
 140 {
 141     char   *key;
 142     char   *value;
 143     char   *curr_opt;
 144     char   *next_opt;
 145     struct option *op;
 146     char    bf[BUFSIZ];
 147
 148     for (curr_opt = get_field(options); curr_opt; curr_opt = next_opt) {
 149         next_opt = get_field((char *) 0);
 150
 151         /*
 152          * Separate the option into name and value parts. For backwards
 153          * compatibility we ignore exactly one '=' between name and value.
 154          */
 155         curr_opt = chop_string(curr_opt);
 156         if (*(value = curr_opt + strcspn(curr_opt, whitespace_eq))) {
 157             if (*value != '=') {
 158                 *value++ = 0;
 159                 value += strspn(value, whitespace);
 160             }
 161             if (*value == '=') {
 162                 *value++ = 0;
 163                 value += strspn(value, whitespace);
 164             }
 165         }
 166         if (*value == 0)
 167             value = 0;
 168         key = curr_opt;
 169
 170         /*
 171          * Disallow missing option names (and empty option fields).
 172          */
 173         if (*key == 0)
 174             tcpd_jump("missing option name");
 175
 176         /*
 177          * Lookup the option-specific info and do some common error checks.
 178          * Delegate option-specific processing to the specific functions.
 179          */
 180
 181         for (op = option_table; op->name && STR_NE(op->name, key); op++)
 182              /* VOID */ ;
 183         if (op->name == 0)
 184             tcpd_jump("bad option name: \"%s\"", key);
 185         if (!value && need_arg(op))
 186             tcpd_jump("option \"%s\" requires value", key);
 187         if (value && !permit_arg(op))
 188             tcpd_jump("option \"%s\" requires no value", key);
 189         if (next_opt && use_last(op))
 190             tcpd_jump("option \"%s\" must be at end", key);
 191         if (value && expand_arg(op))
 192             value = chop_string(percent_x(bf, sizeof(bf), value, request));
 193         if (hosts_access_verbose)
 194             syslog(LOG_DEBUG, "option:   %s %s", key, value ? value : "");
 195         (*(op->func)) (value, request);
 196     }
 197 }
 198
 199 /* allow_option - grant access */
 200
 201 /* ARGSUSED */
 202
 203 static void allow_option(value, request)
 204 char   *value;
 205 struct request_info *request;
 206 {
 207     longjmp(tcpd_buf, AC_PERMIT);
 208 }
 209
 210 /* deny_option - deny access */
 211
 212 /* ARGSUSED */
 213
 214 static void deny_option(value, request)
 215 char   *value;
 216 struct request_info *request;
 217 {
 218     longjmp(tcpd_buf, AC_DENY);
 219 }
 220
 221 /* banners_option - expand %<char>, terminate each line with CRLF */
 222
 223 static void banners_option(value, request)
 224 char   *value;
 225 struct request_info *request;
 226 {
 227     char    path[MAXPATHNAMELEN];
 228     char    ibuf[BUFSIZ];
 229     char    obuf[2 * BUFSIZ];
 230     struct stat st;
 231     int     ch;
 232     FILE   *fp;
 233
 234     sprintf(path, "%s/%s", value, eval_daemon(request));
 235     if ((fp = fopen(path, "r")) != 0) {
 236         while ((ch = fgetc(fp)) == 0)
 237             write(request->fd, "", 1);
 238         ungetc(ch, fp);
 239         while (fgets(ibuf, sizeof(ibuf) - 1, fp)) {
 240             if (split_at(ibuf, '\n'))
 241                 strcat(ibuf, "\r\n");
 242             percent_x(obuf, sizeof(obuf), ibuf, request);
 243             write(request->fd, obuf, strlen(obuf));
 244         }
 245         fclose(fp);
 246     } else if (stat(value, &st) < 0) {
 247         tcpd_warn("%s: %m", value);
 248     }
 249 }
 250
 251 /* group_option - switch group id */
 252
 253 /* ARGSUSED */
 254
 255 static void group_option(value, request)
 256 char   *value;
 257 struct request_info *request;
 258 {
 259     struct group *grp;
 260     struct group *getgrnam();
 261
 262     if ((grp = getgrnam(value)) == 0)
 263         tcpd_jump("unknown group: \"%s\"", value);
 264     endgrent();
 265
 266     if (dry_run == 0 && setgid(grp->gr_gid))
 267         tcpd_jump("setgid(%s): %m", value);
 268 }
 269
 270 /* user_option - switch user id */
 271
 272 /* ARGSUSED */
 273
 274 static void user_option(value, request)
 275 char   *value;
 276 struct request_info *request;
 277 {
 278     struct passwd *pwd;
 279     struct passwd *getpwnam();
 280     char   *group;
 281
 282     if ((group = split_at(value, '.')) != 0)
 283         group_option(group, request);
 284     if ((pwd = getpwnam(value)) == 0)
 285         tcpd_jump("unknown user: \"%s\"", value);
 286     endpwent();
 287
 288     if (dry_run == 0 && setuid(pwd->pw_uid))
 289         tcpd_jump("setuid(%s): %m", value);
 290 }
 291
 292 /* umask_option - set file creation mask */
 293
 294 /* ARGSUSED */
 295
 296 static void umask_option(value, request)
 297 char   *value;
 298 struct request_info *request;
 299 {
 300     unsigned mask;
 301     char    junk;
 302
 303     if (sscanf(value, "%o%c", &mask, &junk) != 1 || (mask & 0777) != mask)
 304         tcpd_jump("bad umask value: \"%s\"", value);
 305     (void) umask(mask);
 306 }
 307
 308 /* spawn_option - spawn a shell command and wait */
 309
 310 /* ARGSUSED */
 311
 312 static void spawn_option(value, request)
 313 char   *value;
 314 struct request_info *request;
 315 {
 316     if (dry_run == 0)
 317         shell_cmd(value);
 318 }
 319
 320 /* linger_option - set the socket linger time (Marc Boucher <marc@cam.org>) */
 321
 322 /* ARGSUSED */
 323
 324 static void linger_option(value, request)
 325 char   *value;
 326 struct request_info *request;
 327 {
 328     struct linger linger;
 329     char    junk;
 330
 331     if (sscanf(value, "%d%c", &linger.l_linger, &junk) != 1
 332         || linger.l_linger < 0)
 333         tcpd_jump("bad linger value: \"%s\"", value);
 334     if (dry_run == 0) {
 335         linger.l_onoff = (linger.l_linger != 0);
 336         if (setsockopt(request->fd, SOL_SOCKET, SO_LINGER, (char *) &linger,
 337                        sizeof(linger)) < 0)
 338             tcpd_warn("setsockopt SO_LINGER %d: %m", linger.l_linger);
 339     }
 340 }
 341
 342 /* keepalive_option - set the socket keepalive option */
 343
 344 /* ARGSUSED */
 345
 346 static void keepalive_option(value, request)
 347 char   *value;
 348 struct request_info *request;
 349 {
 350     static int on = 1;
 351
 352     if (dry_run == 0 && setsockopt(request->fd, SOL_SOCKET, SO_KEEPALIVE,
 353                                    (char *) &on, sizeof(on)) < 0)
 354         tcpd_warn("setsockopt SO_KEEPALIVE: %m");
 355 }
 356
 357 /* nice_option - set nice value */
 358
 359 /* ARGSUSED */
 360
 361 static void nice_option(value, request)
 362 char   *value;
 363 struct request_info *request;
 364 {
 365     int     niceval = 10;
 366     char    junk;
 367
 368     if (value != 0 && sscanf(value, "%d%c", &niceval, &junk) != 1)
 369         tcpd_jump("bad nice value: \"%s\"", value);
 370     if (dry_run == 0 && nice(niceval) < 0)
 371         tcpd_warn("nice(%d): %m", niceval);
 372 }
 373
 374 /* twist_option - replace process by shell command */
 375
 376 static void twist_option(value, request)
 377 char   *value;
 378 struct request_info *request;
 379 {
 380     char   *error;
 381
 382     if (dry_run != 0) {
 383         dry_run = 0;
 384     } else {
 385         if (resident > 0)
 386             tcpd_jump("twist option in resident process");
 387
 388         syslog(deny_severity, "twist %s to %s", eval_client(request), value);
 389
 390         /* Before switching to the shell, set up stdin, stdout and stderr. */
 391
 392 #define maybe_dup2(from, to) ((from == to) ? to : (close(to), dup(from)))
 393
 394         if (maybe_dup2(request->fd, 0) != 0 ||
 395             maybe_dup2(request->fd, 1) != 1 ||
 396             maybe_dup2(request->fd, 2) != 2) {
 397             error = "twist_option: dup: %m";
 398         } else {
 399             if (request->fd > 2)
 400                 close(request->fd);
 401             (void) execl("/bin/sh", "sh", "-c", value, (char *) 0);
 402             error = "twist_option: /bin/sh: %m";
 403         }
 404
 405         /* Something went wrong: we MUST terminate the process. */
 406
 407         tcpd_warn(error);
 408         clean_exit(request);
 409     }
 410 }
 411
 412 /* rfc931_option - look up remote user name */
 413
 414 static void rfc931_option(value, request)
 415 char   *value;
 416 struct request_info *request;
 417 {
 418     int     timeout;
 419     char    junk;
 420
 421     if (value != 0) {
 422         if (sscanf(value, "%d%c", &timeout, &junk) != 1 || timeout <= 0)
 423             tcpd_jump("bad rfc931 timeout: \"%s\"", value);
 424         rfc931_timeout = timeout;
 425     }
 426     (void) eval_user(request);
 427 }
 428
 429 /* setenv_option - set environment variable */
 430
 431 /* ARGSUSED */
 432
 433 static void setenv_option(value, request)
 434 char   *value;
 435 struct request_info *request;
 436 {
 437     extern int setenv(const char *, const char *, int);
 438     char   *var_value;
 439
 440     if (*(var_value = value + strcspn(value, whitespace)))
 441         *var_value++ = 0;
 442     if (setenv(chop_string(value), chop_string(var_value), 1))
 443         tcpd_jump("memory allocation failure");
 444 }
 445
 446  /*
 447   * The severity option goes last because it comes with a huge amount of ugly
 448   * #ifdefs and tables.
 449   */
 450
 451 struct syslog_names {
 452     char   *name;
 453     int     value;
 454 };
 455
 456 static struct syslog_names log_fac[] = {
 457 #ifdef LOG_KERN
 458     "kern", LOG_KERN,
 459 #endif
 460 #ifdef LOG_USER
 461     "user", LOG_USER,
 462 #endif
 463 #ifdef LOG_MAIL
 464     "mail", LOG_MAIL,
 465 #endif
 466 #ifdef LOG_DAEMON
 467     "daemon", LOG_DAEMON,
 468 #endif
 469 #ifdef LOG_AUTH
 470     "auth", LOG_AUTH,
 471 #endif
 472 #ifdef LOG_LPR
 473     "lpr", LOG_LPR,
 474 #endif
 475 #ifdef LOG_NEWS
 476     "news", LOG_NEWS,
 477 #endif
 478 #ifdef LOG_UUCP
 479     "uucp", LOG_UUCP,
 480 #endif
 481 #ifdef LOG_CRON
 482     "cron", LOG_CRON,
 483 #endif
 484 #ifdef LOG_LOCAL0
 485     "local0", LOG_LOCAL0,
 486 #endif
 487 #ifdef LOG_LOCAL1
 488     "local1", LOG_LOCAL1,
 489 #endif
 490 #ifdef LOG_LOCAL2
 491     "local2", LOG_LOCAL2,
 492 #endif
 493 #ifdef LOG_LOCAL3
 494     "local3", LOG_LOCAL3,
 495 #endif
 496 #ifdef LOG_LOCAL4
 497     "local4", LOG_LOCAL4,
 498 #endif
 499 #ifdef LOG_LOCAL5
 500     "local5", LOG_LOCAL5,
 501 #endif
 502 #ifdef LOG_LOCAL6
 503     "local6", LOG_LOCAL6,
 504 #endif
 505 #ifdef LOG_LOCAL7
 506     "local7", LOG_LOCAL7,
 507 #endif
 508     0,
 509 };
 510
 511 static struct syslog_names log_sev[] = {
 512 #ifdef LOG_EMERG
 513     "emerg", LOG_EMERG,
 514 #endif
 515 #ifdef LOG_ALERT
 516     "alert", LOG_ALERT,
 517 #endif
 518 #ifdef LOG_CRIT
 519     "crit", LOG_CRIT,
 520 #endif
 521 #ifdef LOG_ERR
 522     "err", LOG_ERR,
 523 #endif
 524 #ifdef LOG_WARNING
 525     "warning", LOG_WARNING,
 526 #endif
 527 #ifdef LOG_NOTICE
 528     "notice", LOG_NOTICE,
 529 #endif
 530 #ifdef LOG_INFO
 531     "info", LOG_INFO,
 532 #endif
 533 #ifdef LOG_DEBUG
 534     "debug", LOG_DEBUG,
 535 #endif
 536     0,
 537 };
 538
 539 /* severity_map - lookup facility or severity value */
 540
 541 static int severity_map(table, name)
 542 struct syslog_names *table;
 543 char   *name;
 544 {
 545     struct syslog_names *t;
 546
 547     for (t = table; t->name; t++)
 548         if (STR_EQ(t->name, name))
 549             return (t->value);
 550     tcpd_jump("bad syslog facility or severity: \"%s\"", name);
 551     /* NOTREACHED */
 552 }
 553
 554 /* severity_option - change logging severity for this event (Dave Mitchell) */
 555
 556 /* ARGSUSED */
 557
 558 static void severity_option(value, request)
 559 char   *value;
 560 struct request_info *request;
 561 {
 562     char   *level = split_at(value, '.');
 563
 564     allow_severity = deny_severity = level ?
 565         severity_map(log_fac, value) | severity_map(log_sev, level) :
 566         severity_map(log_sev, value);
 567 }
 568
 569 /* get_field - return pointer to next field in string */
 570
 571 static char *get_field(string)
 572 char   *string;
 573 {
 574     static char *last = "";
 575     char   *src;
 576     char   *dst;
 577     char   *ret;
 578     int     ch;
 579
 580     /*
 581      * This function returns pointers to successive fields within a given
 582      * string. ":" is the field separator; warn if the rule ends in one. It
 583      * replaces a "\:" sequence by ":", without treating the result of
 584      * substitution as field terminator. A null argument means resume search
 585      * where the previous call terminated. This function destroys its
 586      * argument.
 587      *
 588      * Work from explicit source or from memory. While processing \: we
 589      * overwrite the input. This way we do not have to maintain buffers for
 590      * copies of input fields.
 591      */
 592
 593     src = dst = ret = (string ? string : last);
 594     if (src[0] == 0)
 595         return (0);
 596
 597     while (ch = *src) {
 598         if (ch == ':') {
 599             if (*++src == 0)
 600                 tcpd_warn("rule ends in \":\"");
 601             break;
 602         }
 603         if (ch == '\\' && src[1] == ':')
 604             src++;
 605         *dst++ = *src++;
 606     }
 607     last = src;
 608     *dst = 0;
 609     return (ret);
 610 }
 611
 612 /* chop_string - strip leading and trailing blanks from string */
 613
 614 static char *chop_string(string)
 615 register char *string;
 616 {
 617     char   *start = 0;
 618     char   *end;
 619     char   *cp;
 620
 621     for (cp = string; *cp; cp++) {
 622         if (!isspace(*cp)) {
 623             if (start == 0)
 624                 start = cp;
 625             end = cp;
 626         }
 627     }
 628     return (start ? (end[1] = 0, start) : cp);
 629 }