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   * $FreeBSD$
  31   */
  32
  33 #ifndef lint
  34 static char sccsid[] = "@(#) options.c 1.17 96/02/11 17:01:31";
  35 #endif
  36
  37 /* System libraries. */
  38
  39 #include <sys/types.h>
  40 #include <sys/param.h>
  41 #include <sys/socket.h>
  42 #include <sys/stat.h>
  43 #include <netinet/in.h>
  44 #include <netdb.h>
  45 #include <stdio.h>
  46 #define SYSLOG_NAMES
  47 #include <syslog.h>
  48 #include <pwd.h>
  49 #include <grp.h>
  50 #include <ctype.h>
  51 #include <setjmp.h>
  52 #include <string.h>
  53
  54 #ifndef MAXPATHNAMELEN
  55 #define MAXPATHNAMELEN  BUFSIZ
  56 #endif
  57
  58 /* Local stuff. */
  59
  60 #include "tcpd.h"
  61
  62 /* Options runtime support. */
  63
  64 int     dry_run = 0;                    /* flag set in verification mode */
  65 extern jmp_buf tcpd_buf;                /* tcpd_jump() support */
  66
  67 /* Options parser support. */
  68
  69 static char whitespace_eq[] = "= \t\r\n";
  70 #define whitespace (whitespace_eq + 1)
  71
  72 static char *get_field();               /* chew :-delimited field off string */
  73 static char *chop_string();             /* strip leading and trailing blanks */
  74
  75 /* List of functions that implement the options. Add yours here. */
  76
  77 static void user_option();              /* execute "user name.group" option */
  78 static void group_option();             /* execute "group name" option */
  79 static void umask_option();             /* execute "umask mask" option */
  80 static void linger_option();            /* execute "linger time" option */
  81 static void keepalive_option();         /* execute "keepalive" option */
  82 static void spawn_option();             /* execute "spawn command" option */
  83 static void twist_option();             /* execute "twist command" option */
  84 static void rfc931_option();            /* execute "rfc931" option */
  85 static void setenv_option();            /* execute "setenv name value" */
  86 static void nice_option();              /* execute "nice" option */
  87 static void severity_option();          /* execute "severity value" */
  88 static void allow_option();             /* execute "allow" option */
  89 static void deny_option();              /* execute "deny" option */
  90 static void banners_option();           /* execute "banners path" option */
  91
  92 /* Structure of the options table. */
  93
  94 struct option {
  95     char   *name;                       /* keyword name, case is ignored */
  96     void  (*func) ();                   /* function that does the real work */
  97     int     flags;                      /* see below... */
  98 };
  99
 100 #define NEED_ARG        (1<<1)          /* option requires argument */
 101 #define USE_LAST        (1<<2)          /* option must be last */
 102 #define OPT_ARG         (1<<3)          /* option has optional argument */
 103 #define EXPAND_ARG      (1<<4)          /* do %x expansion on argument */
 104
 105 #define need_arg(o)     ((o)->flags & NEED_ARG)
 106 #define opt_arg(o)      ((o)->flags & OPT_ARG)
 107 #define permit_arg(o)   ((o)->flags & (NEED_ARG | OPT_ARG))
 108 #define use_last(o)     ((o)->flags & USE_LAST)
 109 #define expand_arg(o)   ((o)->flags & EXPAND_ARG)
 110
 111 /* List of known keywords. Add yours here. */
 112
 113 static struct option option_table[] = {
 114     "user", user_option, NEED_ARG,
 115     "group", group_option, NEED_ARG,
 116     "umask", umask_option, NEED_ARG,
 117     "linger", linger_option, NEED_ARG,
 118     "keepalive", keepalive_option, 0,
 119     "spawn", spawn_option, NEED_ARG | EXPAND_ARG,
 120     "twist", twist_option, NEED_ARG | EXPAND_ARG | USE_LAST,
 121     "rfc931", rfc931_option, OPT_ARG,
 122     "setenv", setenv_option, NEED_ARG | EXPAND_ARG,
 123     "nice", nice_option, OPT_ARG,
 124     "severity", severity_option, NEED_ARG,
 125     "allow", allow_option, USE_LAST,
 126     "deny", deny_option, USE_LAST,
 127     "banners", banners_option, NEED_ARG,
 128     0,
 129 };
 130
 131 /* process_options - process access control options */
 132
 133 void    process_options(options, request)
 134 char   *options;
 135 struct request_info *request;
 136 {
 137     char   *key;
 138     char   *value;
 139     char   *curr_opt;
 140     char   *next_opt;
 141     struct option *op;
 142     char    bf[BUFSIZ];
 143
 144     for (curr_opt = get_field(options); curr_opt; curr_opt = next_opt) {
 145         next_opt = get_field((char *) 0);
 146
 147         /*
 148          * Separate the option into name and value parts. For backwards
 149          * compatibility we ignore exactly one '=' between name and value.
 150          */
 151         curr_opt = chop_string(curr_opt);
 152         if (*(value = curr_opt + strcspn(curr_opt, whitespace_eq))) {
 153             if (*value != '=') {
 154                 *value++ = 0;
 155                 value += strspn(value, whitespace);
 156             }
 157             if (*value == '=') {
 158                 *value++ = 0;
 159                 value += strspn(value, whitespace);
 160             }
 161         }
 162         if (*value == 0)
 163             value = 0;
 164         key = curr_opt;
 165
 166         /*
 167          * Disallow missing option names (and empty option fields).
 168          */
 169         if (*key == 0)
 170             tcpd_jump("missing option name");
 171
 172         /*
 173          * Lookup the option-specific info and do some common error checks.
 174          * Delegate option-specific processing to the specific functions.
 175          */
 176
 177         for (op = option_table; op->name && STR_NE(op->name, key); op++)
 178              /* VOID */ ;
 179         if (op->name == 0)
 180             tcpd_jump("bad option name: \"%s\"", key);
 181         if (!value && need_arg(op))
 182             tcpd_jump("option \"%s\" requires value", key);
 183         if (value && !permit_arg(op))
 184             tcpd_jump("option \"%s\" requires no value", key);
 185         if (next_opt && use_last(op))
 186             tcpd_jump("option \"%s\" must be at end", key);
 187         if (value && expand_arg(op))
 188             value = chop_string(percent_x(bf, sizeof(bf), value, request));
 189         if (hosts_access_verbose)
 190             syslog(LOG_DEBUG, "option:   %s %s", key, value ? value : "");
 191         (*(op->func)) (value, request);
 192     }
 193 }
 194
 195 /* allow_option - grant access */
 196
 197 /* ARGSUSED */
 198
 199 static void allow_option(value, request)
 200 char   *value;
 201 struct request_info *request;
 202 {
 203     longjmp(tcpd_buf, AC_PERMIT);
 204 }
 205
 206 /* deny_option - deny access */
 207
 208 /* ARGSUSED */
 209
 210 static void deny_option(value, request)
 211 char   *value;
 212 struct request_info *request;
 213 {
 214     longjmp(tcpd_buf, AC_DENY);
 215 }
 216
 217 /* banners_option - expand %<char>, terminate each line with CRLF */
 218
 219 static void banners_option(value, request)
 220 char   *value;
 221 struct request_info *request;
 222 {
 223     char    path[MAXPATHNAMELEN];
 224     char    ibuf[BUFSIZ];
 225     char    obuf[2 * BUFSIZ];
 226     struct stat st;
 227     int     ch;
 228     FILE   *fp;
 229
 230     sprintf(path, "%s/%s", value, eval_daemon(request));
 231     if ((fp = fopen(path, "r")) != 0) {
 232         while ((ch = fgetc(fp)) == 0)
 233             write(request->fd, "", 1);
 234         ungetc(ch, fp);
 235         while (fgets(ibuf, sizeof(ibuf) - 1, fp)) {
 236             if (split_at(ibuf, '\n'))
 237                 strcat(ibuf, "\r\n");
 238             percent_x(obuf, sizeof(obuf), ibuf, request);
 239             write(request->fd, obuf, strlen(obuf));
 240         }
 241         fclose(fp);
 242     } else if (stat(value, &st) < 0) {
 243         tcpd_warn("%s: %m", value);
 244     }
 245 }
 246
 247 /* group_option - switch group id */
 248
 249 /* ARGSUSED */
 250
 251 static void group_option(value, request)
 252 char   *value;
 253 struct request_info *request;
 254 {
 255     struct group *grp;
 256     struct group *getgrnam();
 257
 258     if ((grp = getgrnam(value)) == 0)
 259         tcpd_jump("unknown group: \"%s\"", value);
 260     endgrent();
 261
 262     if (dry_run == 0 && setgid(grp->gr_gid))
 263         tcpd_jump("setgid(%s): %m", value);
 264 }
 265
 266 /* user_option - switch user id */
 267
 268 /* ARGSUSED */
 269
 270 static void user_option(value, request)
 271 char   *value;
 272 struct request_info *request;
 273 {
 274     struct passwd *pwd;
 275     struct passwd *getpwnam();
 276     char   *group;
 277
 278     if ((group = split_at(value, '.')) != 0)
 279         group_option(group, request);
 280     if ((pwd = getpwnam(value)) == 0)
 281         tcpd_jump("unknown user: \"%s\"", value);
 282     endpwent();
 283
 284     if (dry_run == 0 && setuid(pwd->pw_uid))
 285         tcpd_jump("setuid(%s): %m", value);
 286 }
 287
 288 /* umask_option - set file creation mask */
 289
 290 /* ARGSUSED */
 291
 292 static void umask_option(value, request)
 293 char   *value;
 294 struct request_info *request;
 295 {
 296     unsigned mask;
 297     char    junk;
 298
 299     if (sscanf(value, "%o%c", &mask, &junk) != 1 || (mask & 0777) != mask)
 300         tcpd_jump("bad umask value: \"%s\"", value);
 301     (void) umask(mask);
 302 }
 303
 304 /* spawn_option - spawn a shell command and wait */
 305
 306 /* ARGSUSED */
 307
 308 static void spawn_option(value, request)
 309 char   *value;
 310 struct request_info *request;
 311 {
 312     if (dry_run == 0)
 313         shell_cmd(value);
 314 }
 315
 316 /* linger_option - set the socket linger time (Marc Boucher <marc@cam.org>) */
 317
 318 /* ARGSUSED */
 319
 320 static void linger_option(value, request)
 321 char   *value;
 322 struct request_info *request;
 323 {
 324     struct linger linger;
 325     char    junk;
 326
 327     if (sscanf(value, "%d%c", &linger.l_linger, &junk) != 1
 328         || linger.l_linger < 0)
 329         tcpd_jump("bad linger value: \"%s\"", value);
 330     if (dry_run == 0) {
 331         linger.l_onoff = (linger.l_linger != 0);
 332         if (setsockopt(request->fd, SOL_SOCKET, SO_LINGER, (char *) &linger,
 333                        sizeof(linger)) < 0)
 334             tcpd_warn("setsockopt SO_LINGER %d: %m", linger.l_linger);
 335     }
 336 }
 337
 338 /* keepalive_option - set the socket keepalive option */
 339
 340 /* ARGSUSED */
 341
 342 static void keepalive_option(value, request)
 343 char   *value;
 344 struct request_info *request;
 345 {
 346     static int on = 1;
 347
 348     if (dry_run == 0 && setsockopt(request->fd, SOL_SOCKET, SO_KEEPALIVE,
 349                                    (char *) &on, sizeof(on)) < 0)
 350         tcpd_warn("setsockopt SO_KEEPALIVE: %m");
 351 }
 352
 353 /* nice_option - set nice value */
 354
 355 /* ARGSUSED */
 356
 357 static void nice_option(value, request)
 358 char   *value;
 359 struct request_info *request;
 360 {
 361     int     niceval = 10;
 362     char    junk;
 363
 364     if (value != 0 && sscanf(value, "%d%c", &niceval, &junk) != 1)
 365         tcpd_jump("bad nice value: \"%s\"", value);
 366     if (dry_run == 0 && nice(niceval) < 0)
 367         tcpd_warn("nice(%d): %m", niceval);
 368 }
 369
 370 /* twist_option - replace process by shell command */
 371
 372 static void twist_option(value, request)
 373 char   *value;
 374 struct request_info *request;
 375 {
 376     char   *error;
 377
 378     if (dry_run != 0) {
 379         dry_run = 0;
 380     } else {
 381         if (resident > 0)
 382             tcpd_jump("twist option in resident process");
 383
 384         syslog(deny_severity, "twist %s to %s", eval_client(request), value);
 385
 386         /* Before switching to the shell, set up stdin, stdout and stderr. */
 387
 388 #define maybe_dup2(from, to) ((from == to) ? to : (close(to), dup(from)))
 389
 390         if (maybe_dup2(request->fd, 0) != 0 ||
 391             maybe_dup2(request->fd, 1) != 1 ||
 392             maybe_dup2(request->fd, 2) != 2) {
 393             error = "twist_option: dup: %m";
 394         } else {
 395             if (request->fd > 2)
 396                 close(request->fd);
 397             (void) execl("/bin/sh", "sh", "-c", value, (char *) 0);
 398             error = "twist_option: /bin/sh: %m";
 399         }
 400
 401         /* Something went wrong: we MUST terminate the process. */
 402
 403         tcpd_warn(error);
 404         clean_exit(request);
 405     }
 406 }
 407
 408 /* rfc931_option - look up remote user name */
 409
 410 static void rfc931_option(value, request)
 411 char   *value;
 412 struct request_info *request;
 413 {
 414     int     timeout;
 415     char    junk;
 416
 417     if (value != 0) {
 418         if (sscanf(value, "%d%c", &timeout, &junk) != 1 || timeout <= 0)
 419             tcpd_jump("bad rfc931 timeout: \"%s\"", value);
 420         rfc931_timeout = timeout;
 421     }
 422     (void) eval_user(request);
 423 }
 424
 425 /* setenv_option - set environment variable */
 426
 427 /* ARGSUSED */
 428
 429 static void setenv_option(value, request)
 430 char   *value;
 431 struct request_info *request;
 432 {
 433     char   *var_value;
 434
 435     if (*(var_value = value + strcspn(value, whitespace)))
 436         *var_value++ = 0;
 437     if (setenv(chop_string(value), chop_string(var_value), 1))
 438         tcpd_jump("memory allocation failure");
 439 }
 440
 441 /* severity_map - lookup facility or severity value */
 442
 443 static int severity_map(table, name)
 444 CODE   *table;
 445 char   *name;
 446 {
 447     CODE *t;
 448
 449     for (t = table; t->c_name; t++)
 450         if (STR_EQ(t->c_name, name))
 451             return (t->c_val);
 452     tcpd_jump("bad syslog facility or severity: \"%s\"", name);
 453     /* NOTREACHED */
 454 }
 455
 456 /* severity_option - change logging severity for this event (Dave Mitchell) */
 457
 458 /* ARGSUSED */
 459
 460 static void severity_option(value, request)
 461 char   *value;
 462 struct request_info *request;
 463 {
 464     char   *level = split_at(value, '.');
 465
 466     allow_severity = deny_severity = level ?
 467         severity_map(facilitynames, value) | severity_map(prioritynames, level)
 468         : severity_map(prioritynames, value);
 469 }
 470
 471 /* get_field - return pointer to next field in string */
 472
 473 static char *get_field(string)
 474 char   *string;
 475 {
 476     static char *last = "";
 477     char   *src;
 478     char   *dst;
 479     char   *ret;
 480     int     ch;
 481
 482     /*
 483      * This function returns pointers to successive fields within a given
 484      * string. ":" is the field separator; warn if the rule ends in one. It
 485      * replaces a "\:" sequence by ":", without treating the result of
 486      * substitution as field terminator. A null argument means resume search
 487      * where the previous call terminated. This function destroys its
 488      * argument.
 489      *
 490      * Work from explicit source or from memory. While processing \: we
 491      * overwrite the input. This way we do not have to maintain buffers for
 492      * copies of input fields.
 493      */
 494
 495     src = dst = ret = (string ? string : last);
 496     if (src[0] == 0)
 497         return (0);
 498
 499     while (ch = *src) {
 500         if (ch == ':') {
 501             if (*++src == 0)
 502                 tcpd_warn("rule ends in \":\"");
 503             break;
 504         }
 505         if (ch == '\\' && src[1] == ':')
 506             src++;
 507         *dst++ = *src++;
 508     }
 509     last = src;
 510     *dst = 0;
 511     return (ret);
 512 }
 513
 514 /* chop_string - strip leading and trailing blanks from string */
 515
 516 static char *chop_string(string)
 517 register char *string;
 518 {
 519     char   *start = 0;
 520     char   *end;
 521     char   *cp;
 522
 523     for (cp = string; *cp; cp++) {
 524         if (!isspace(*cp)) {
 525             if (start == 0)
 526                 start = cp;
 527             end = cp;
 528         }
 529     }
 530     return (start ? (end[1] = 0, start) : cp);
 531 }