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