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