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