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