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(char *, struct request_info *); /* user name.group */ 80 static void group_option(char *, struct request_info *); /* group name */ 81 static void umask_option(char *, struct request_info *); /* umask mask */ 82 static void linger_option(char *, struct request_info *); /* linger time */ 83 static void keepalive_option(char *, struct request_info *); /* keepalive */ 84 static void spawn_option(char *, struct request_info *); /* spawn command */ 85 static void twist_option(char *, struct request_info *); /* twist command */ 86 static void rfc931_option(char *, struct request_info *); /* rfc931 */ 87 static void setenv_option(char *, struct request_info *); /* setenv name value */ 88 static void nice_option(char *, struct request_info *); /* nice */ 89 static void severity_option(char *, struct request_info *); /* severity value */ 90 static void allow_option(char *, struct request_info *); /* allow */ 91 static void deny_option(char *, struct request_info *); /* deny */ 92 static void banners_option(char *, struct request_info *); /* banners path */ 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(char *value, 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(char *value, struct request_info *request) 210 { 211 longjmp(tcpd_buf, AC_DENY); 212 } 213 214 /* banners_option - expand %<char>, terminate each line with CRLF */ 215 216 static void banners_option(char *value, struct request_info *request) 217 { 218 char path[MAXPATHNAMELEN]; 219 char ibuf[BUFSIZ]; 220 char obuf[2 * BUFSIZ]; 221 struct stat st; 222 int ch; 223 FILE *fp; 224 225 sprintf(path, "%s/%s", value, eval_daemon(request)); 226 if ((fp = fopen(path, "r")) != 0) { 227 while ((ch = fgetc(fp)) == 0) 228 write(request->fd, "", 1); 229 ungetc(ch, fp); 230 while (fgets(ibuf, sizeof(ibuf) - 1, fp)) { 231 if (split_at(ibuf, '\n')) 232 strcat(ibuf, "\r\n"); 233 percent_x(obuf, sizeof(obuf), ibuf, request); 234 write(request->fd, obuf, strlen(obuf)); 235 } 236 fclose(fp); 237 } else if (stat(value, &st) < 0) { 238 tcpd_warn("%s: %m", value); 239 } 240 } 241 242 /* group_option - switch group id */ 243 244 /* ARGSUSED */ 245 246 static void group_option(char *value, struct request_info *request) 247 { 248 struct group *grp; 249 250 if ((grp = getgrnam(value)) == 0) 251 tcpd_jump("unknown group: \"%s\"", value); 252 endgrent(); 253 254 if (dry_run == 0 && setgid(grp->gr_gid)) 255 tcpd_jump("setgid(%s): %m", value); 256 } 257 258 /* user_option - switch user id */ 259 260 /* ARGSUSED */ 261 262 static void user_option(char *value, struct request_info *request) 263 { 264 struct passwd *pwd; 265 char *group; 266 267 if ((group = split_at(value, '.')) != 0) 268 group_option(group, request); 269 if ((pwd = getpwnam(value)) == 0) 270 tcpd_jump("unknown user: \"%s\"", value); 271 endpwent(); 272 273 if (dry_run == 0 && setuid(pwd->pw_uid)) 274 tcpd_jump("setuid(%s): %m", value); 275 } 276 277 /* umask_option - set file creation mask */ 278 279 /* ARGSUSED */ 280 281 static void umask_option(char *value, struct request_info *request) 282 { 283 unsigned mask; 284 char junk; 285 286 if (sscanf(value, "%o%c", &mask, &junk) != 1 || (mask & 0777) != mask) 287 tcpd_jump("bad umask value: \"%s\"", value); 288 (void) umask(mask); 289 } 290 291 /* spawn_option - spawn a shell command and wait */ 292 293 /* ARGSUSED */ 294 295 static void spawn_option(char *value, struct request_info *request) 296 { 297 if (dry_run == 0) 298 shell_cmd(value); 299 } 300 301 /* linger_option - set the socket linger time (Marc Boucher <marc@cam.org>) */ 302 303 /* ARGSUSED */ 304 305 static void linger_option(char *value, struct request_info *request) 306 { 307 struct linger linger; 308 char junk; 309 310 if (sscanf(value, "%d%c", &linger.l_linger, &junk) != 1 311 || linger.l_linger < 0) 312 tcpd_jump("bad linger value: \"%s\"", value); 313 if (dry_run == 0) { 314 linger.l_onoff = (linger.l_linger != 0); 315 if (setsockopt(request->fd, SOL_SOCKET, SO_LINGER, (char *) &linger, 316 sizeof(linger)) < 0) 317 tcpd_warn("setsockopt SO_LINGER %d: %m", linger.l_linger); 318 } 319 } 320 321 /* keepalive_option - set the socket keepalive option */ 322 323 /* ARGSUSED */ 324 325 static void keepalive_option(char *value, struct request_info *request) 326 { 327 static int on = 1; 328 329 if (dry_run == 0 && setsockopt(request->fd, SOL_SOCKET, SO_KEEPALIVE, 330 (char *) &on, sizeof(on)) < 0) 331 tcpd_warn("setsockopt SO_KEEPALIVE: %m"); 332 } 333 334 /* nice_option - set nice value */ 335 336 /* ARGSUSED */ 337 338 static void nice_option(char *value, struct request_info *request) 339 { 340 int niceval = 10; 341 char junk; 342 343 if (value != 0 && sscanf(value, "%d%c", &niceval, &junk) != 1) 344 tcpd_jump("bad nice value: \"%s\"", value); 345 if (dry_run == 0 && nice(niceval) < 0) 346 tcpd_warn("nice(%d): %m", niceval); 347 } 348 349 /* twist_option - replace process by shell command */ 350 351 static void twist_option(char *value, struct request_info *request) 352 { 353 char *error; 354 355 if (dry_run != 0) { 356 dry_run = 0; 357 } else { 358 if (resident > 0) 359 tcpd_jump("twist option in resident process"); 360 361 syslog(deny_severity, "twist %s to %s", eval_client(request), value); 362 363 /* Before switching to the shell, set up stdin, stdout and stderr. */ 364 365 #define maybe_dup2(from, to) ((from == to) ? to : (close(to), dup(from))) 366 367 if (maybe_dup2(request->fd, 0) != 0 || 368 maybe_dup2(request->fd, 1) != 1 || 369 maybe_dup2(request->fd, 2) != 2) { 370 error = "twist_option: dup: %m"; 371 } else { 372 if (request->fd > 2) 373 close(request->fd); 374 (void) execl("/bin/sh", "sh", "-c", value, (char *) 0); 375 error = "twist_option: /bin/sh: %m"; 376 } 377 378 /* Something went wrong: we MUST terminate the process. */ 379 380 tcpd_warn(error); 381 clean_exit(request); 382 } 383 } 384 385 /* rfc931_option - look up remote user name */ 386 387 static void rfc931_option(char *value, struct request_info *request) 388 { 389 int timeout; 390 char junk; 391 392 if (value != 0) { 393 if (sscanf(value, "%d%c", &timeout, &junk) != 1 || timeout <= 0) 394 tcpd_jump("bad rfc931 timeout: \"%s\"", value); 395 rfc931_timeout = timeout; 396 } 397 (void) eval_user(request); 398 } 399 400 /* setenv_option - set environment variable */ 401 402 /* ARGSUSED */ 403 404 static void setenv_option(char *value, struct request_info *request) 405 { 406 char *var_value; 407 408 if (*(var_value = value + strcspn(value, whitespace))) 409 *var_value++ = 0; 410 if (setenv(chop_string(value), chop_string(var_value), 1)) 411 tcpd_jump("memory allocation failure"); 412 } 413 414 /* severity_map - lookup facility or severity value */ 415 416 static int severity_map(const CODE *table, char *name) 417 { 418 const CODE *t; 419 int ret = -1; 420 421 for (t = table; t->c_name; t++) 422 if (STR_EQ(t->c_name, name)) { 423 ret = t->c_val; 424 break; 425 } 426 if (ret == -1) 427 tcpd_jump("bad syslog facility or severity: \"%s\"", name); 428 429 return (ret); 430 } 431 432 /* severity_option - change logging severity for this event (Dave Mitchell) */ 433 434 /* ARGSUSED */ 435 436 static void severity_option(char *value, struct request_info *request) 437 { 438 char *level = split_at(value, '.'); 439 440 allow_severity = deny_severity = level ? 441 severity_map(facilitynames, value) | severity_map(prioritynames, level) 442 : severity_map(prioritynames, value); 443 } 444 445 /* get_field - return pointer to next field in string */ 446 447 static char *get_field(char *string) 448 { 449 static char *last = ""; 450 char *src; 451 char *dst; 452 char *ret; 453 int ch; 454 455 /* 456 * This function returns pointers to successive fields within a given 457 * string. ":" is the field separator; warn if the rule ends in one. It 458 * replaces a "\:" sequence by ":", without treating the result of 459 * substitution as field terminator. A null argument means resume search 460 * where the previous call terminated. This function destroys its 461 * argument. 462 * 463 * Work from explicit source or from memory. While processing \: we 464 * overwrite the input. This way we do not have to maintain buffers for 465 * copies of input fields. 466 */ 467 468 src = dst = ret = (string ? string : last); 469 if (src[0] == 0) 470 return (0); 471 472 while (ch = *src) { 473 if (ch == ':') { 474 if (*++src == 0) 475 tcpd_warn("rule ends in \":\""); 476 break; 477 } 478 if (ch == '\\' && src[1] == ':') 479 src++; 480 *dst++ = *src++; 481 } 482 last = src; 483 *dst = 0; 484 return (ret); 485 } 486 487 /* chop_string - strip leading and trailing blanks from string */ 488 489 static char *chop_string(register char *string) 490 { 491 char *start = 0; 492 char *end; 493 char *cp; 494 495 for (cp = string; *cp; cp++) { 496 if (!isspace(*cp)) { 497 if (start == 0) 498 start = cp; 499 end = cp; 500 } 501 } 502 return (start ? (end[1] = 0, start) : cp); 503 } 504