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 } 531