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 #ifndef lint
  39 static char sccsid[] = "@(#) options.c 1.17 96/02/11 17:01:31";
  40 #endif
  41
  42 /* System libraries. */
  43
  44 #include <sys/types.h>
  45 #include <sys/param.h>
  46 #include <sys/socket.h>
  47 #include <sys/stat.h>
  48 #include <netinet/in.h>
  49 #include <netdb.h>
  50 #include <stdio.h>
  51 #include <stdlib.h>
  52 #include <unistd.h>
  53 #include <syslog.h>
  54 #include <pwd.h>
  55 #include <grp.h>
  56 #include <ctype.h>
  57 #include <setjmp.h>
  58 #include <string.h>
  59
  60 #ifndef MAXPATHNAMELEN
  61 #define MAXPATHNAMELEN  BUFSIZ
  62 #endif
  63
  64 /* Local stuff. */
  65
  66 #include "tcpd.h"
  67
  68 /* Options runtime support. */
  69
  70 int     dry_run = 0;                    /* flag set in verification mode */
  71 extern jmp_buf tcpd_buf;                /* tcpd_jump() support */
  72
  73 /* Options parser support. */
  74
  75 static char whitespace_eq[] = "= \t\r\n";
  76 #define whitespace (whitespace_eq + 1)
  77
  78 static char *get_field();               /* chew :-delimited field off string */
  79 static char *chop_string();             /* strip leading and trailing blanks */
  80
  81 /* List of functions that implement the options. Add yours here. */
  82
  83 static void user_option();              /* execute "user name.group" option */
  84 static void group_option();             /* execute "group name" option */
  85 static void umask_option();             /* execute "umask mask" option */
  86 static void linger_option();            /* execute "linger time" option */
  87 static void keepalive_option();         /* execute "keepalive" option */
  88 static void spawn_option();             /* execute "spawn command" option */
  89 static void twist_option();             /* execute "twist command" option */
  90 static void rfc931_option();            /* execute "rfc931" option */
  91 static void setenv_option();            /* execute "setenv name value" */
  92 static void nice_option();              /* execute "nice" option */
  93 static void severity_option();          /* execute "severity value" */
  94 static void allow_option();             /* execute "allow" option */
  95 static void deny_option();              /* execute "deny" option */
  96 static void banners_option();           /* execute "banners path" option */
  97
  98 /* Structure of the options table. */
  99
 100 struct option {
 101     char   *name;                       /* keyword name, case is ignored */
 102     void  (*func) ();                   /* function that does the real work */
 103     int     flags;                      /* see below... */
 104 };
 105
 106 #define NEED_ARG        (1<<1)          /* option requires argument */
 107 #define USE_LAST        (1<<2)          /* option must be last */
 108 #define OPT_ARG         (1<<3)          /* option has optional argument */
 109 #define EXPAND_ARG      (1<<4)          /* do %x expansion on argument */
 110
 111 #define need_arg(o)     ((o)->flags & NEED_ARG)
 112 #define opt_arg(o)      ((o)->flags & OPT_ARG)
 113 #define permit_arg(o)   ((o)->flags & (NEED_ARG | OPT_ARG))
 114 #define use_last(o)     ((o)->flags & USE_LAST)
 115 #define expand_arg(o)   ((o)->flags & EXPAND_ARG)
 116
 117 /* List of known keywords. Add yours here. */
 118
 119 static struct option option_table[] = {
 120     "user", user_option, NEED_ARG,
 121     "group", group_option, NEED_ARG,
 122     "umask", umask_option, NEED_ARG,
 123     "linger", linger_option, NEED_ARG,
 124     "keepalive", keepalive_option, 0,
 125     "spawn", spawn_option, NEED_ARG | EXPAND_ARG,
 126     "twist", twist_option, NEED_ARG | EXPAND_ARG | USE_LAST,
 127     "rfc931", rfc931_option, OPT_ARG,
 128     "setenv", setenv_option, NEED_ARG | EXPAND_ARG,
 129     "nice", nice_option, OPT_ARG,
 130     "severity", severity_option, NEED_ARG,
 131     "allow", allow_option, USE_LAST,
 132     "deny", deny_option, USE_LAST,
 133     "banners", banners_option, NEED_ARG,
 134     0,
 135 };
 136
 137 /* process_options - process access control options */
 138
 139 void    process_options(options, request)
 140 char   *options;
 141 struct request_info *request;
 142 {
 143     char   *key;
 144     char   *value;
 145     char   *curr_opt;
 146     char   *next_opt;
 147     struct option *op;
 148     char    bf[BUFSIZ];
 149
 150     for (curr_opt = get_field(options); curr_opt; curr_opt = next_opt) {
 151         next_opt = get_field((char *) 0);
 152
 153         /*
 154          * Separate the option into name and value parts. For backwards
 155          * compatibility we ignore exactly one '=' between name and value.
 156          */
 157         curr_opt = chop_string(curr_opt);
 158         if (*(value = curr_opt + strcspn(curr_opt, whitespace_eq))) {
 159             if (*value != '=') {
 160                 *value++ = 0;
 161                 value += strspn(value, whitespace);
 162             }
 163             if (*value == '=') {
 164                 *value++ = 0;
 165                 value += strspn(value, whitespace);
 166             }
 167         }
 168         if (*value == 0)
 169             value = 0;
 170         key = curr_opt;
 171
 172         /*
 173          * Disallow missing option names (and empty option fields).
 174          */
 175         if (*key == 0)
 176             tcpd_jump("missing option name");
 177
 178         /*
 179          * Lookup the option-specific info and do some common error checks.
 180          * Delegate option-specific processing to the specific functions.
 181          */
 182
 183         for (op = option_table; op->name && STR_NE(op->name, key); op++)
 184              /* VOID */ ;
 185         if (op->name == 0)
 186             tcpd_jump("bad option name: \"%s\"", key);
 187         if (!value && need_arg(op))
 188             tcpd_jump("option \"%s\" requires value", key);
 189         if (value && !permit_arg(op))
 190             tcpd_jump("option \"%s\" requires no value", key);
 191         if (next_opt && use_last(op))
 192             tcpd_jump("option \"%s\" must be at end", key);
 193         if (value && expand_arg(op))
 194             value = chop_string(percent_x(bf, sizeof(bf), value, request));
 195         if (hosts_access_verbose)
 196             syslog(LOG_DEBUG, "option:   %s %s", key, value ? value : "");
 197         (*(op->func)) (value, request);
 198     }
 199 }
 200
 201 /* allow_option - grant access */
 202
 203 /* ARGSUSED */
 204
 205 static void allow_option(value, request)
 206 char   *value;
 207 struct request_info *request;
 208 {
 209     longjmp(tcpd_buf, AC_PERMIT);
 210 }
 211
 212 /* deny_option - deny access */
 213
 214 /* ARGSUSED */
 215
 216 static void deny_option(value, request)
 217 char   *value;
 218 struct request_info *request;
 219 {
 220     longjmp(tcpd_buf, AC_DENY);
 221 }
 222
 223 /* banners_option - expand %<char>, terminate each line with CRLF */
 224
 225 static void banners_option(value, request)
 226 char   *value;
 227 struct request_info *request;
 228 {
 229     char    path[MAXPATHNAMELEN];
 230     char    ibuf[BUFSIZ];
 231     char    obuf[2 * BUFSIZ];
 232     struct stat st;
 233     int     ch;
 234     FILE   *fp;
 235
 236     sprintf(path, "%s/%s", value, eval_daemon(request));
 237     if ((fp = fopen(path, "r")) != 0) {
 238         while ((ch = fgetc(fp)) == 0)
 239             write(request->fd, "", 1);
 240         ungetc(ch, fp);
 241         while (fgets(ibuf, sizeof(ibuf) - 1, fp)) {
 242             if (split_at(ibuf, '\n'))
 243                 strcat(ibuf, "\r\n");
 244             percent_x(obuf, sizeof(obuf), ibuf, request);
 245             write(request->fd, obuf, strlen(obuf));
 246         }
 247         fclose(fp);
 248     } else if (stat(value, &st) < 0) {
 249         tcpd_warn("%s: %m", value);
 250     }
 251 }
 252
 253 /* group_option - switch group id */
 254
 255 /* ARGSUSED */
 256
 257 static void group_option(value, request)
 258 char   *value;
 259 struct request_info *request;
 260 {
 261     struct group *grp;
 262     struct group *getgrnam();
 263
 264     if ((grp = getgrnam(value)) == 0)
 265         tcpd_jump("unknown group: \"%s\"", value);
 266     endgrent();
 267
 268     if (dry_run == 0 && setgid(grp->gr_gid))
 269         tcpd_jump("setgid(%s): %m", value);
 270 }
 271
 272 /* user_option - switch user id */
 273
 274 /* ARGSUSED */
 275
 276 static void user_option(value, request)
 277 char   *value;
 278 struct request_info *request;
 279 {
 280     struct passwd *pwd;
 281     struct passwd *getpwnam();
 282     char   *group;
 283
 284     if ((group = split_at(value, '.')) != 0)
 285         group_option(group, request);
 286     if ((pwd = getpwnam(value)) == 0)
 287         tcpd_jump("unknown user: \"%s\"", value);
 288     endpwent();
 289
 290     if (dry_run == 0 && setuid(pwd->pw_uid))
 291         tcpd_jump("setuid(%s): %m", value);
 292 }
 293
 294 /* umask_option - set file creation mask */
 295
 296 /* ARGSUSED */
 297
 298 static void umask_option(value, request)
 299 char   *value;
 300 struct request_info *request;
 301 {
 302     unsigned mask;
 303     char    junk;
 304
 305     if (sscanf(value, "%o%c", &mask, &junk) != 1 || (mask & 0777) != mask)
 306         tcpd_jump("bad umask value: \"%s\"", value);
 307     (void) umask(mask);
 308 }
 309
 310 /* spawn_option - spawn a shell command and wait */
 311
 312 /* ARGSUSED */
 313
 314 static void spawn_option(value, request)
 315 char   *value;
 316 struct request_info *request;
 317 {
 318     if (dry_run == 0)
 319         shell_cmd(value);
 320 }
 321
 322 /* linger_option - set the socket linger time (Marc Boucher <marc@cam.org>) */
 323
 324 /* ARGSUSED */
 325
 326 static void linger_option(value, request)
 327 char   *value;
 328 struct request_info *request;
 329 {
 330     struct linger linger;
 331     char    junk;
 332
 333     if (sscanf(value, "%d%c", &linger.l_linger, &junk) != 1
 334         || linger.l_linger < 0)
 335         tcpd_jump("bad linger value: \"%s\"", value);
 336     if (dry_run == 0) {
 337         linger.l_onoff = (linger.l_linger != 0);
 338         if (setsockopt(request->fd, SOL_SOCKET, SO_LINGER, (char *) &linger,
 339                        sizeof(linger)) < 0)
 340             tcpd_warn("setsockopt SO_LINGER %d: %m", linger.l_linger);
 341     }
 342 }
 343
 344 /* keepalive_option - set the socket keepalive option */
 345
 346 /* ARGSUSED */
 347
 348 static void keepalive_option(value, request)
 349 char   *value;
 350 struct request_info *request;
 351 {
 352     static int on = 1;
 353
 354     if (dry_run == 0 && setsockopt(request->fd, SOL_SOCKET, SO_KEEPALIVE,
 355                                    (char *) &on, sizeof(on)) < 0)
 356         tcpd_warn("setsockopt SO_KEEPALIVE: %m");
 357 }
 358
 359 /* nice_option - set nice value */
 360
 361 /* ARGSUSED */
 362
 363 static void nice_option(value, request)
 364 char   *value;
 365 struct request_info *request;
 366 {
 367     int     niceval = 10;
 368     char    junk;
 369
 370     if (value != 0 && sscanf(value, "%d%c", &niceval, &junk) != 1)
 371         tcpd_jump("bad nice value: \"%s\"", value);
 372     if (dry_run == 0 && nice(niceval) < 0)
 373         tcpd_warn("nice(%d): %m", niceval);
 374 }
 375
 376 /* twist_option - replace process by shell command */
 377
 378 static void twist_option(value, request)
 379 char   *value;
 380 struct request_info *request;
 381 {
 382     char   *error;
 383
 384     if (dry_run != 0) {
 385         dry_run = 0;
 386     } else {
 387         if (resident > 0)
 388             tcpd_jump("twist option in resident process");
 389
 390         syslog(deny_severity, "twist %s to %s", eval_client(request), value);
 391
 392         /* Before switching to the shell, set up stdin, stdout and stderr. */
 393
 394 #define maybe_dup2(from, to) ((from == to) ? to : (close(to), dup(from)))
 395
 396         if (maybe_dup2(request->fd, 0) != 0 ||
 397             maybe_dup2(request->fd, 1) != 1 ||
 398             maybe_dup2(request->fd, 2) != 2) {
 399             error = "twist_option: dup: %m";
 400         } else {
 401             if (request->fd > 2)
 402                 close(request->fd);
 403             (void) execl("/bin/sh", "sh", "-c", value, (char *) 0);
 404             error = "twist_option: /bin/sh: %m";
 405         }
 406
 407         /* Something went wrong: we MUST terminate the process. */
 408
 409         tcpd_warn(error);
 410         clean_exit(request);
 411     }
 412 }
 413
 414 /* rfc931_option - look up remote user name */
 415
 416 static void rfc931_option(value, request)
 417 char   *value;
 418 struct request_info *request;
 419 {
 420     int     timeout;
 421     char    junk;
 422
 423     if (value != 0) {
 424         if (sscanf(value, "%d%c", &timeout, &junk) != 1 || timeout <= 0)
 425             tcpd_jump("bad rfc931 timeout: \"%s\"", value);
 426         rfc931_timeout = timeout;
 427     }
 428     (void) eval_user(request);
 429 }
 430
 431 /* setenv_option - set environment variable */
 432
 433 /* ARGSUSED */
 434
 435 static void setenv_option(value, request)
 436 char   *value;
 437 struct request_info *request;
 438 {
 439     extern int setenv(const char *, const char *, int);
 440     char   *var_value;
 441
 442     if (*(var_value = value + strcspn(value, whitespace)))
 443         *var_value++ = 0;
 444     if (setenv(chop_string(value), chop_string(var_value), 1))
 445         tcpd_jump("memory allocation failure");
 446 }
 447
 448  /*
 449   * The severity option goes last because it comes with a huge amount of ugly
 450   * #ifdefs and tables.
 451   */
 452
 453 struct syslog_names {
 454     char   *name;
 455     int     value;
 456 };
 457
 458 static struct syslog_names log_fac[] = {
 459 #ifdef LOG_KERN
 460     "kern", LOG_KERN,
 461 #endif
 462 #ifdef LOG_USER
 463     "user", LOG_USER,
 464 #endif
 465 #ifdef LOG_MAIL
 466     "mail", LOG_MAIL,
 467 #endif
 468 #ifdef LOG_DAEMON
 469     "daemon", LOG_DAEMON,
 470 #endif
 471 #ifdef LOG_AUTH
 472     "auth", LOG_AUTH,
 473 #endif
 474 #ifdef LOG_LPR
 475     "lpr", LOG_LPR,
 476 #endif
 477 #ifdef LOG_NEWS
 478     "news", LOG_NEWS,
 479 #endif
 480 #ifdef LOG_UUCP
 481     "uucp", LOG_UUCP,
 482 #endif
 483 #ifdef LOG_CRON
 484     "cron", LOG_CRON,
 485 #endif
 486 #ifdef LOG_LOCAL0
 487     "local0", LOG_LOCAL0,
 488 #endif
 489 #ifdef LOG_LOCAL1
 490     "local1", LOG_LOCAL1,
 491 #endif
 492 #ifdef LOG_LOCAL2
 493     "local2", LOG_LOCAL2,
 494 #endif
 495 #ifdef LOG_LOCAL3
 496     "local3", LOG_LOCAL3,
 497 #endif
 498 #ifdef LOG_LOCAL4
 499     "local4", LOG_LOCAL4,
 500 #endif
 501 #ifdef LOG_LOCAL5
 502     "local5", LOG_LOCAL5,
 503 #endif
 504 #ifdef LOG_LOCAL6
 505     "local6", LOG_LOCAL6,
 506 #endif
 507 #ifdef LOG_LOCAL7
 508     "local7", LOG_LOCAL7,
 509 #endif
 510     0,
 511 };
 512
 513 static struct syslog_names log_sev[] = {
 514 #ifdef LOG_EMERG
 515     "emerg", LOG_EMERG,
 516 #endif
 517 #ifdef LOG_ALERT
 518     "alert", LOG_ALERT,
 519 #endif
 520 #ifdef LOG_CRIT
 521     "crit", LOG_CRIT,
 522 #endif
 523 #ifdef LOG_ERR
 524     "err", LOG_ERR,
 525 #endif
 526 #ifdef LOG_WARNING
 527     "warning", LOG_WARNING,
 528 #endif
 529 #ifdef LOG_NOTICE
 530     "notice", LOG_NOTICE,
 531 #endif
 532 #ifdef LOG_INFO
 533     "info", LOG_INFO,
 534 #endif
 535 #ifdef LOG_DEBUG
 536     "debug", LOG_DEBUG,
 537 #endif
 538     0,
 539 };
 540
 541 /* severity_map - lookup facility or severity value */
 542
 543 static int severity_map(table, name)
 544 struct syslog_names *table;
 545 char   *name;
 546 {
 547     struct syslog_names *t;
 548
 549     for (t = table; t->name; t++)
 550         if (STR_EQ(t->name, name))
 551             return (t->value);
 552     tcpd_jump("bad syslog facility or severity: \"%s\"", name);
 553     /* NOTREACHED */
 554 }
 555
 556 /* severity_option - change logging severity for this event (Dave Mitchell) */
 557
 558 /* ARGSUSED */
 559
 560 static void severity_option(value, request)
 561 char   *value;
 562 struct request_info *request;
 563 {
 564     char   *level = split_at(value, '.');
 565
 566     allow_severity = deny_severity = level ?
 567         severity_map(log_fac, value) | severity_map(log_sev, level) :
 568         severity_map(log_sev, value);
 569 }
 570
 571 /* get_field - return pointer to next field in string */
 572
 573 static char *get_field(string)
 574 char   *string;
 575 {
 576     static char *last = "";
 577     char   *src;
 578     char   *dst;
 579     char   *ret;
 580     int     ch;
 581
 582     /*
 583      * This function returns pointers to successive fields within a given
 584      * string. ":" is the field separator; warn if the rule ends in one. It
 585      * replaces a "\:" sequence by ":", without treating the result of
 586      * substitution as field terminator. A null argument means resume search
 587      * where the previous call terminated. This function destroys its
 588      * argument.
 589      *
 590      * Work from explicit source or from memory. While processing \: we
 591      * overwrite the input. This way we do not have to maintain buffers for
 592      * copies of input fields.
 593      */
 594
 595     src = dst = ret = (string ? string : last);
 596     if (src[0] == 0)
 597         return (0);
 598
 599     while (ch = *src) {
 600         if (ch == ':') {
 601             if (*++src == 0)
 602                 tcpd_warn("rule ends in \":\"");
 603             break;
 604         }
 605         if (ch == '\\' && src[1] == ':')
 606             src++;
 607         *dst++ = *src++;
 608     }
 609     last = src;
 610     *dst = 0;
 611     return (ret);
 612 }
 613
 614 /* chop_string - strip leading and trailing blanks from string */
 615
 616 static char *chop_string(string)
 617 register char *string;
 618 {
 619     char   *start = 0;
 620     char   *end;
 621     char   *cp;
 622
 623     for (cp = string; *cp; cp++) {
 624         if (!isspace(*cp)) {
 625             if (start == 0)
 626                 start = cp;
 627             end = cp;
 628         }
 629     }
 630     return (start ? (end[1] = 0, start) : cp);
 631 }