contrib/tcp_wrappers/options.c

   1  /*
   2   * General skeleton for adding options to the access control language. The
   3   * features offered by this module are documented in the hosts_options(5)
   4   * manual page (source file: hosts_options.5, "nroff -man" format).
   5   *
   6   * Notes and warnings for those who want to add features:
   7   *
   8   * In case of errors, abort options processing and deny access. There are too
   9   * many irreversible side effects to make error recovery feasible. For
  10   * example, it makes no sense to continue after we have already changed the
  11   * userid.
  12   *
  13   * In case of errors, do not terminate the process: the routines might be
  14   * called from a long-running daemon that should run forever. Instead, call
  15   * tcpd_jump() which does a non-local goto back into the hosts_access()
  16   * routine.
  17   *
  18   * In case of severe errors, use clean_exit() instead of directly calling
  19   * exit(), or the inetd may loop on an UDP request.
  20   *
  21   * In verification mode (for example, with the "tcpdmatch" command) the
  22   * "dry_run" flag is set. In this mode, an option function should just "say"
  23   * what it is going to do instead of really doing it.
  24   *
  25   * Some option functions do not return (for example, the twist option passes
  26   * control to another program). In verification mode (dry_run flag is set)
  27   * such options should clear the "dry_run" flag to inform the caller of this
  28   * course of action.
  29   */
  30
  31 #ifndef lint
  32 static char sccsid[] = "@(#) options.c 1.17 96/02/11 17:01:31";
  33 #endif
  34
  35 /* System libraries. */
  36
  37 #include <sys/types.h>
  38 #include <sys/param.h>
  39 #include <sys/socket.h>
  40 #include <sys/stat.h>
  41 #include <netinet/in.h>
  42 #include <netdb.h>
  43 #include <stdio.h>
  44 #define SYSLOG_NAMES
  45 #include <syslog.h>
  46 #include <pwd.h>
  47 #include <grp.h>
  48 #include <ctype.h>
  49 #include <setjmp.h>
  50 #include <string.h>
  51
  52 #ifndef MAXPATHNAMELEN
  53 #define MAXPATHNAMELEN  BUFSIZ
  54 #endif
  55
  56 /* Local stuff. */
  57
  58 #include "tcpd.h"
  59
  60 /* Options runtime support. */
  61
  62 int     dry_run = 0;                    /* flag set in verification mode */
  63 extern jmp_buf tcpd_buf;                /* tcpd_jump() support */
  64
  65 /* Options parser support. */
  66
  67 static char whitespace_eq[] = "= \t\r\n";
  68 #define whitespace (whitespace_eq + 1)
  69
  70 static char *get_field();               /* chew :-delimited field off string */
  71 static char *chop_string();             /* strip leading and trailing blanks */
  72
  73 /* List of functions that implement the options. Add yours here. */
  74
  75 static void user_option();              /* execute "user name.group" option */
  76 static void group_option();             /* execute "group name" option */
  77 static void umask_option();             /* execute "umask mask" option */
  78 static void linger_option();            /* execute "linger time" option */
  79 static void keepalive_option();         /* execute "keepalive" option */
  80 static void spawn_option();             /* execute "spawn command" option */
  81 static void twist_option();             /* execute "twist command" option */
  82 static void rfc931_option();            /* execute "rfc931" option */
  83 static void setenv_option();            /* execute "setenv name value" */
  84 static void nice_option();              /* execute "nice" option */
  85 static void severity_option();          /* execute "severity value" */
  86 static void allow_option();             /* execute "allow" option */
  87 static void deny_option();              /* execute "deny" option */
  88 static void banners_option();           /* execute "banners path" option */
  89
  90 /* Structure of the options table. */
  91
  92 struct option {
  93     char   *name;                       /* keyword name, case is ignored */
  94     void  (*func) ();                   /* function that does the real work */
  95     int     flags;                      /* see below... */
  96 };
  97
  98 #define NEED_ARG        (1<<1)          /* option requires argument */
  99 #define USE_LAST        (1<<2)          /* option must be last */
 100 #define OPT_ARG         (1<<3)          /* option has optional argument */
 101 #define EXPAND_ARG      (1<<4)          /* do %x expansion on argument */
 102
 103 #define need_arg(o)     ((o)->flags & NEED_ARG)
 104 #define opt_arg(o)      ((o)->flags & OPT_ARG)
 105 #define permit_arg(o)   ((o)->flags & (NEED_ARG | OPT_ARG))
 106 #define use_last(o)     ((o)->flags & USE_LAST)
 107 #define expand_arg(o)   ((o)->flags & EXPAND_ARG)
 108
 109 /* List of known keywords. Add yours here. */
 110
 111 static struct option option_table[] = {
 112     "user", user_option, NEED_ARG,
 113     "group", group_option, NEED_ARG,
 114     "umask", umask_option, NEED_ARG,
 115     "linger", linger_option, NEED_ARG,
 116     "keepalive", keepalive_option, 0,
 117     "spawn", spawn_option, NEED_ARG | EXPAND_ARG,
 118     "twist", twist_option, NEED_ARG | EXPAND_ARG | USE_LAST,
 119     "rfc931", rfc931_option, OPT_ARG,
 120     "setenv", setenv_option, NEED_ARG | EXPAND_ARG,
 121     "nice", nice_option, OPT_ARG,
 122     "severity", severity_option, NEED_ARG,
 123     "allow", allow_option, USE_LAST,
 124     "deny", deny_option, USE_LAST,
 125     "banners", banners_option, NEED_ARG,
 126     0,
 127 };
 128
 129 /* process_options - process access control options */
 130
 131 void    process_options(options, request)
 132 char   *options;
 133 struct request_info *request;
 134 {
 135     char   *key;
 136     char   *value;
 137     char   *curr_opt;
 138     char   *next_opt;
 139     struct option *op;
 140     char    bf[BUFSIZ];
 141
 142     for (curr_opt = get_field(options); curr_opt; curr_opt = next_opt) {
 143         next_opt = get_field((char *) 0);
 144
 145         /*
 146          * Separate the option into name and value parts. For backwards
 147          * compatibility we ignore exactly one '=' between name and value.
 148          */
 149         curr_opt = chop_string(curr_opt);
 150         if (*(value = curr_opt + strcspn(curr_opt, whitespace_eq))) {
 151             if (*value != '=') {
 152                 *value++ = 0;
 153                 value += strspn(value, whitespace);
 154             }
 155             if (*value == '=') {
 156                 *value++ = 0;
 157                 value += strspn(value, whitespace);
 158             }
 159         }
 160         if (*value == 0)
 161             value = 0;
 162         key = curr_opt;
 163
 164         /*
 165          * Disallow missing option names (and empty option fields).
 166          */
 167         if (*key == 0)
 168             tcpd_jump("missing option name");
 169
 170         /*
 171          * Lookup the option-specific info and do some common error checks.
 172          * Delegate option-specific processing to the specific functions.
 173          */
 174
 175         for (op = option_table; op->name && STR_NE(op->name, key); op++)
 176              /* VOID */ ;
 177         if (op->name == 0)
 178             tcpd_jump("bad option name: \"%s\"", key);
 179         if (!value && need_arg(op))
 180             tcpd_jump("option \"%s\" requires value", key);
 181         if (value && !permit_arg(op))
 182             tcpd_jump("option \"%s\" requires no value", key);
 183         if (next_opt && use_last(op))
 184             tcpd_jump("option \"%s\" must be at end", key);
 185         if (value && expand_arg(op))
 186             value = chop_string(percent_x(bf, sizeof(bf), value, request));
 187         if (hosts_access_verbose)
 188             syslog(LOG_DEBUG, "option:   %s %s", key, value ? value : "");
 189         (*(op->func)) (value, request);
 190     }
 191 }
 192
 193 /* allow_option - grant access */
 194
 195 /* ARGSUSED */
 196
 197 static void allow_option(value, request)
 198 char   *value;
 199 struct request_info *request;
 200 {
 201     longjmp(tcpd_buf, AC_PERMIT);
 202 }
 203
 204 /* deny_option - deny access */
 205
 206 /* ARGSUSED */
 207
 208 static void deny_option(value, request)
 209 char   *value;
 210 struct request_info *request;
 211 {
 212     longjmp(tcpd_buf, AC_DENY);
 213 }
 214
 215 /* banners_option - expand %<char>, terminate each line with CRLF */
 216
 217 static void banners_option(value, request)
 218 char   *value;
 219 struct request_info *request;
 220 {
 221     char    path[MAXPATHNAMELEN];
 222     char    ibuf[BUFSIZ];
 223     char    obuf[2 * BUFSIZ];
 224     struct stat st;
 225     int     ch;
 226     FILE   *fp;
 227
 228     sprintf(path, "%s/%s", value, eval_daemon(request));
 229     if ((fp = fopen(path, "r")) != 0) {
 230         while ((ch = fgetc(fp)) == 0)
 231             write(request->fd, "", 1);
 232         ungetc(ch, fp);
 233         while (fgets(ibuf, sizeof(ibuf) - 1, fp)) {
 234             if (split_at(ibuf, '\n'))
 235                 strcat(ibuf, "\r\n");
 236             percent_x(obuf, sizeof(obuf), ibuf, request);
 237             write(request->fd, obuf, strlen(obuf));
 238         }
 239         fclose(fp);
 240     } else if (stat(value, &st) < 0) {
 241         tcpd_warn("%s: %m", value);
 242     }
 243 }
 244
 245 /* group_option - switch group id */
 246
 247 /* ARGSUSED */
 248
 249 static void group_option(value, request)
 250 char   *value;
 251 struct request_info *request;
 252 {
 253     struct group *grp;
 254     struct group *getgrnam();
 255
 256     if ((grp = getgrnam(value)) == 0)
 257         tcpd_jump("unknown group: \"%s\"", value);
 258     endgrent();
 259
 260     if (dry_run == 0 && setgid(grp->gr_gid))
 261         tcpd_jump("setgid(%s): %m", value);
 262 }
 263
 264 /* user_option - switch user id */
 265
 266 /* ARGSUSED */
 267
 268 static void user_option(value, request)
 269 char   *value;
 270 struct request_info *request;
 271 {
 272     struct passwd *pwd;
 273     struct passwd *getpwnam();
 274     char   *group;
 275
 276     if ((group = split_at(value, '.')) != 0)
 277         group_option(group, request);
 278     if ((pwd = getpwnam(value)) == 0)
 279         tcpd_jump("unknown user: \"%s\"", value);
 280     endpwent();
 281
 282     if (dry_run == 0 && setuid(pwd->pw_uid))
 283         tcpd_jump("setuid(%s): %m", value);
 284 }
 285
 286 /* umask_option - set file creation mask */
 287
 288 /* ARGSUSED */
 289
 290 static void umask_option(value, request)
 291 char   *value;
 292 struct request_info *request;
 293 {
 294     unsigned mask;
 295     char    junk;
 296
 297     if (sscanf(value, "%o%c", &mask, &junk) != 1 || (mask & 0777) != mask)
 298         tcpd_jump("bad umask value: \"%s\"", value);
 299     (void) umask(mask);
 300 }
 301
 302 /* spawn_option - spawn a shell command and wait */
 303
 304 /* ARGSUSED */
 305
 306 static void spawn_option(value, request)
 307 char   *value;
 308 struct request_info *request;
 309 {
 310     if (dry_run == 0)
 311         shell_cmd(value);
 312 }
 313
 314 /* linger_option - set the socket linger time (Marc Boucher <marc@cam.org>) */
 315
 316 /* ARGSUSED */
 317
 318 static void linger_option(value, request)
 319 char   *value;
 320 struct request_info *request;
 321 {
 322     struct linger linger;
 323     char    junk;
 324
 325     if (sscanf(value, "%d%c", &linger.l_linger, &junk) != 1
 326         || linger.l_linger < 0)
 327         tcpd_jump("bad linger value: \"%s\"", value);
 328     if (dry_run == 0) {
 329         linger.l_onoff = (linger.l_linger != 0);
 330         if (setsockopt(request->fd, SOL_SOCKET, SO_LINGER, (char *) &linger,
 331                        sizeof(linger)) < 0)
 332             tcpd_warn("setsockopt SO_LINGER %d: %m", linger.l_linger);
 333     }
 334 }
 335
 336 /* keepalive_option - set the socket keepalive option */
 337
 338 /* ARGSUSED */
 339
 340 static void keepalive_option(value, request)
 341 char   *value;
 342 struct request_info *request;
 343 {
 344     static int on = 1;
 345
 346     if (dry_run == 0 && setsockopt(request->fd, SOL_SOCKET, SO_KEEPALIVE,
 347                                    (char *) &on, sizeof(on)) < 0)
 348         tcpd_warn("setsockopt SO_KEEPALIVE: %m");
 349 }
 350
 351 /* nice_option - set nice value */
 352
 353 /* ARGSUSED */
 354
 355 static void nice_option(value, request)
 356 char   *value;
 357 struct request_info *request;
 358 {
 359     int     niceval = 10;
 360     char    junk;
 361
 362     if (value != 0 && sscanf(value, "%d%c", &niceval, &junk) != 1)
 363         tcpd_jump("bad nice value: \"%s\"", value);
 364     if (dry_run == 0 && nice(niceval) < 0)
 365         tcpd_warn("nice(%d): %m", niceval);
 366 }
 367
 368 /* twist_option - replace process by shell command */
 369
 370 static void twist_option(value, request)
 371 char   *value;
 372 struct request_info *request;
 373 {
 374     char   *error;
 375
 376     if (dry_run != 0) {
 377         dry_run = 0;
 378     } else {
 379         if (resident > 0)
 380             tcpd_jump("twist option in resident process");
 381
 382         syslog(deny_severity, "twist %s to %s", eval_client(request), value);
 383
 384         /* Before switching to the shell, set up stdin, stdout and stderr. */
 385
 386 #define maybe_dup2(from, to) ((from == to) ? to : (close(to), dup(from)))
 387
 388         if (maybe_dup2(request->fd, 0) != 0 ||
 389             maybe_dup2(request->fd, 1) != 1 ||
 390             maybe_dup2(request->fd, 2) != 2) {
 391             error = "twist_option: dup: %m";
 392         } else {
 393             if (request->fd > 2)
 394                 close(request->fd);
 395             (void) execl("/bin/sh", "sh", "-c", value, (char *) 0);
 396             error = "twist_option: /bin/sh: %m";
 397         }
 398
 399         /* Something went wrong: we MUST terminate the process. */
 400
 401         tcpd_warn(error);
 402         clean_exit(request);
 403     }
 404 }
 405
 406 /* rfc931_option - look up remote user name */
 407
 408 static void rfc931_option(value, request)
 409 char   *value;
 410 struct request_info *request;
 411 {
 412     int     timeout;
 413     char    junk;
 414
 415     if (value != 0) {
 416         if (sscanf(value, "%d%c", &timeout, &junk) != 1 || timeout <= 0)
 417             tcpd_jump("bad rfc931 timeout: \"%s\"", value);
 418         rfc931_timeout = timeout;
 419     }
 420     (void) eval_user(request);
 421 }
 422
 423 /* setenv_option - set environment variable */
 424
 425 /* ARGSUSED */
 426
 427 static void setenv_option(value, request)
 428 char   *value;
 429 struct request_info *request;
 430 {
 431     char   *var_value;
 432
 433     if (*(var_value = value + strcspn(value, whitespace)))
 434         *var_value++ = 0;
 435     if (setenv(chop_string(value), chop_string(var_value), 1))
 436         tcpd_jump("memory allocation failure");
 437 }
 438
 439 /* severity_map - lookup facility or severity value */
 440
 441 static int severity_map(table, name)
 442 CODE   *table;
 443 char   *name;
 444 {
 445     CODE *t;
 446
 447     for (t = table; t->c_name; t++)
 448         if (STR_EQ(t->c_name, name))
 449             return (t->c_val);
 450     tcpd_jump("bad syslog facility or severity: \"%s\"", name);
 451     /* NOTREACHED */
 452 }
 453
 454 /* severity_option - change logging severity for this event (Dave Mitchell) */
 455
 456 /* ARGSUSED */
 457
 458 static void severity_option(value, request)
 459 char   *value;
 460 struct request_info *request;
 461 {
 462     char   *level = split_at(value, '.');
 463
 464     allow_severity = deny_severity = level ?
 465         severity_map(facilitynames, value) | severity_map(prioritynames, level)
 466         : severity_map(prioritynames, value);
 467 }
 468
 469 /* get_field - return pointer to next field in string */
 470
 471 static char *get_field(string)
 472 char   *string;
 473 {
 474     static char *last = "";
 475     char   *src;
 476     char   *dst;
 477     char   *ret;
 478     int     ch;
 479
 480     /*
 481      * This function returns pointers to successive fields within a given
 482      * string. ":" is the field separator; warn if the rule ends in one. It
 483      * replaces a "\:" sequence by ":", without treating the result of
 484      * substitution as field terminator. A null argument means resume search
 485      * where the previous call terminated. This function destroys its
 486      * argument.
 487      *
 488      * Work from explicit source or from memory. While processing \: we
 489      * overwrite the input. This way we do not have to maintain buffers for
 490      * copies of input fields.
 491      */
 492
 493     src = dst = ret = (string ? string : last);
 494     if (src[0] == 0)
 495         return (0);
 496
 497     while (ch = *src) {
 498         if (ch == ':') {
 499             if (*++src == 0)
 500                 tcpd_warn("rule ends in \":\"");
 501             break;
 502         }
 503         if (ch == '\\' && src[1] == ':')
 504             src++;
 505         *dst++ = *src++;
 506     }
 507     last = src;
 508     *dst = 0;
 509     return (ret);
 510 }
 511
 512 /* chop_string - strip leading and trailing blanks from string */
 513
 514 static char *chop_string(string)
 515 register char *string;
 516 {
 517     char   *start = 0;
 518     char   *end;
 519     char   *cp;
 520
 521     for (cp = string; *cp; cp++) {
 522         if (!isspace(*cp)) {
 523             if (start == 0)
 524                 start = cp;
 525             end = cp;
 526         }
 527     }
 528     return (start ? (end[1] = 0, start) : cp);
 529 }