builtins.c revision 56303
1/*- 2 * Copyright (c) 1983, 1991, 1993, 1994 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 * 26 * $FreeBSD: head/usr.sbin/inetd/builtins.c 56303 2000-01-20 01:49:41Z green $ 27 * 28 */ 29 30#include <sys/filio.h> 31#include <sys/ioccom.h> 32#include <sys/param.h> 33#include <sys/stat.h> 34#include <sys/socket.h> 35#include <sys/sysctl.h> 36#include <sys/ucred.h> 37#include <sys/uio.h> 38#include <sys/utsname.h> 39 40#include <ctype.h> 41#include <err.h> 42#include <errno.h> 43#include <limits.h> 44#include <pwd.h> 45#include <signal.h> 46#include <stdlib.h> 47#include <string.h> 48#include <sysexits.h> 49#include <syslog.h> 50#include <unistd.h> 51 52#include "inetd.h" 53 54extern int debug; 55extern struct servtab *servtab; 56 57char ring[128]; 58char *endring; 59 60int check_loop __P((struct sockaddr_in *, struct servtab *sep)); 61void inetd_setproctitle __P((char *, int)); 62 63struct biltin biltins[] = { 64 /* Echo received data */ 65 { "echo", SOCK_STREAM, 1, -1, echo_stream }, 66 { "echo", SOCK_DGRAM, 0, 1, echo_dg }, 67 68 /* Internet /dev/null */ 69 { "discard", SOCK_STREAM, 1, -1, discard_stream }, 70 { "discard", SOCK_DGRAM, 0, 1, discard_dg }, 71 72 /* Return 32 bit time since 1970 */ 73 { "time", SOCK_STREAM, 0, -1, machtime_stream }, 74 { "time", SOCK_DGRAM, 0, 1, machtime_dg }, 75 76 /* Return human-readable time */ 77 { "daytime", SOCK_STREAM, 0, -1, daytime_stream }, 78 { "daytime", SOCK_DGRAM, 0, 1, daytime_dg }, 79 80 /* Familiar character generator */ 81 { "chargen", SOCK_STREAM, 1, -1, chargen_stream }, 82 { "chargen", SOCK_DGRAM, 0, 1, chargen_dg }, 83 84 { "tcpmux", SOCK_STREAM, 1, -1, (void (*)())tcpmux }, 85 86 { "auth", SOCK_STREAM, 1, -1, ident_stream }, 87 88 { NULL } 89}; 90 91/* 92 * RFC864 Character Generator Protocol. Generates character data without 93 * any regard for input. 94 */ 95 96void 97initring() 98{ 99 int i; 100 101 endring = ring; 102 103 for (i = 0; i <= 128; ++i) 104 if (isprint(i)) 105 *endring++ = i; 106} 107 108/* ARGSUSED */ 109void 110chargen_dg(s, sep) /* Character generator */ 111 int s; 112 struct servtab *sep; 113{ 114 struct sockaddr_in sin; 115 static char *rs; 116 int len, size; 117 char text[LINESIZ+2]; 118 119 if (endring == 0) { 120 initring(); 121 rs = ring; 122 } 123 124 size = sizeof(sin); 125 if (recvfrom(s, text, sizeof(text), 0, 126 (struct sockaddr *)&sin, &size) < 0) 127 return; 128 129 if (check_loop(&sin, sep)) 130 return; 131 132 if ((len = endring - rs) >= LINESIZ) 133 memmove(text, rs, LINESIZ); 134 else { 135 memmove(text, rs, len); 136 memmove(text + len, ring, LINESIZ - len); 137 } 138 if (++rs == endring) 139 rs = ring; 140 text[LINESIZ] = '\r'; 141 text[LINESIZ + 1] = '\n'; 142 (void) sendto(s, text, sizeof(text), 0, 143 (struct sockaddr *)&sin, sizeof(sin)); 144} 145 146/* ARGSUSED */ 147void 148chargen_stream(s, sep) /* Character generator */ 149 int s; 150 struct servtab *sep; 151{ 152 int len; 153 char *rs, text[LINESIZ+2]; 154 155 inetd_setproctitle(sep->se_service, s); 156 157 if (!endring) { 158 initring(); 159 rs = ring; 160 } 161 162 text[LINESIZ] = '\r'; 163 text[LINESIZ + 1] = '\n'; 164 for (rs = ring;;) { 165 if ((len = endring - rs) >= LINESIZ) 166 memmove(text, rs, LINESIZ); 167 else { 168 memmove(text, rs, len); 169 memmove(text + len, ring, LINESIZ - len); 170 } 171 if (++rs == endring) 172 rs = ring; 173 if (write(s, text, sizeof(text)) != sizeof(text)) 174 break; 175 } 176 exit(0); 177} 178 179/* 180 * RFC867 Daytime Protocol. Sends the current date and time as an ascii 181 * character string without any regard for input. 182 */ 183 184/* ARGSUSED */ 185void 186daytime_dg(s, sep) /* Return human-readable time of day */ 187 int s; 188 struct servtab *sep; 189{ 190 char buffer[256]; 191 time_t clock; 192 struct sockaddr_in sin; 193 int size; 194 195 clock = time((time_t *) 0); 196 197 size = sizeof(sin); 198 if (recvfrom(s, buffer, sizeof(buffer), 0, 199 (struct sockaddr *)&sin, &size) < 0) 200 return; 201 202 if (check_loop(&sin, sep)) 203 return; 204 205 (void) sprintf(buffer, "%.24s\r\n", ctime(&clock)); 206 (void) sendto(s, buffer, strlen(buffer), 0, 207 (struct sockaddr *)&sin, sizeof(sin)); 208} 209 210/* ARGSUSED */ 211void 212daytime_stream(s, sep) /* Return human-readable time of day */ 213 int s; 214 struct servtab *sep; 215{ 216 char buffer[256]; 217 time_t clock; 218 219 clock = time((time_t *) 0); 220 221 (void) sprintf(buffer, "%.24s\r\n", ctime(&clock)); 222 (void) write(s, buffer, strlen(buffer)); 223} 224 225/* 226 * RFC863 Discard Protocol. Any data received is thrown away and no response 227 * is sent. 228 */ 229 230/* ARGSUSED */ 231void 232discard_dg(s, sep) /* Discard service -- ignore data */ 233 int s; 234 struct servtab *sep; 235{ 236 char buffer[BUFSIZE]; 237 238 (void) read(s, buffer, sizeof(buffer)); 239} 240 241/* ARGSUSED */ 242void 243discard_stream(s, sep) /* Discard service -- ignore data */ 244 int s; 245 struct servtab *sep; 246{ 247 int ret; 248 char buffer[BUFSIZE]; 249 250 inetd_setproctitle(sep->se_service, s); 251 while (1) { 252 while ((ret = read(s, buffer, sizeof(buffer))) > 0) 253 ; 254 if (ret == 0 || errno != EINTR) 255 break; 256 } 257 exit(0); 258} 259 260/* 261 * RFC862 Echo Protocol. Any data received is sent back to the sender as 262 * received. 263 */ 264 265/* ARGSUSED */ 266void 267echo_dg(s, sep) /* Echo service -- echo data back */ 268 int s; 269 struct servtab *sep; 270{ 271 char buffer[BUFSIZE]; 272 int i, size; 273 struct sockaddr_in sin; 274 275 size = sizeof(sin); 276 if ((i = recvfrom(s, buffer, sizeof(buffer), 0, 277 (struct sockaddr *)&sin, &size)) < 0) 278 return; 279 280 if (check_loop(&sin, sep)) 281 return; 282 283 (void) sendto(s, buffer, i, 0, (struct sockaddr *)&sin, 284 sizeof(sin)); 285} 286 287/* ARGSUSED */ 288void 289echo_stream(s, sep) /* Echo service -- echo data back */ 290 int s; 291 struct servtab *sep; 292{ 293 char buffer[BUFSIZE]; 294 int i; 295 296 inetd_setproctitle(sep->se_service, s); 297 while ((i = read(s, buffer, sizeof(buffer))) > 0 && 298 write(s, buffer, i) > 0) 299 ; 300 exit(0); 301} 302 303/* 304 * RFC1413 Identification Protocol. Given a TCP port number pair, return a 305 * character string which identifies the owner of that connection on the 306 * server's system. Extended to allow for ~/.fakeid support and ~/.noident 307 * support. 308 */ 309 310/* ARGSUSED */ 311void 312iderror(lport, fport, s, er) /* Generic ident_stream error-sending func */ 313 int lport, fport, s, er; 314{ 315 char *p; 316 317 asprintf(&p, "%d , %d : ERROR : %s\r\n", lport, fport, 318 er == -1 ? "HIDDEN-USER" : er ? strerror(er) : "UNKNOWN-ERROR"); 319 if (p == NULL) { 320 syslog(LOG_ERR, "asprintf: %m"); 321 exit(EX_OSERR); 322 } 323 write(s, p, strlen(p)); 324 free(p); 325 326 exit(0); 327} 328 329/* ARGSUSED */ 330void 331ident_stream(s, sep) /* Ident service (AKA "auth") */ 332 int s; 333 struct servtab *sep; 334{ 335 struct utsname un; 336 struct stat sb; 337 struct sockaddr_in sin[2]; 338 struct ucred uc; 339 struct timeval tv = { 340 10, 341 0 342 }; 343 struct passwd *pw = NULL; 344 fd_set fdset; 345 char buf[BUFSIZE], *cp = NULL, *p, **av, *osname = NULL, garbage[7]; 346 char *fallback = NULL; 347 int len, c, fflag = 0, nflag = 0, rflag = 0, argc = 0, usedfallback = 0; 348 int gflag = 0, Rflag = 0; 349 u_short lport, fport; 350 351 inetd_setproctitle(sep->se_service, s); 352 /* 353 * Reset getopt() since we are a fork() but not an exec() from 354 * a parent which used getopt() already. 355 */ 356 optind = 1; 357 optreset = 1; 358 /* 359 * Take the internal argument vector and count it out to make an 360 * argument count for getopt. This can be used for any internal 361 * service to read arguments and use getopt() easily. 362 */ 363 for (av = sep->se_argv; *av; av++) 364 argc++; 365 if (argc) { 366 int sec, usec; 367 size_t i; 368 u_int32_t random; 369 370 while ((c = getopt(argc, sep->se_argv, "d:fgno:rt:")) != -1) 371 switch (c) { 372 case 'd': 373 fallback = optarg; 374 break; 375 case 'f': 376 fflag = 1; 377 break; 378 case 'g': 379 gflag = 1; 380 random = 0; /* Shush, compiler. */ 381 /* 382 * The number of bits in "random" divided 383 * by the number of bits needed per iteration 384 * gives a more optimal way to reload the 385 * random number only when necessary. 386 * 387 * I'm using base-36, so I need at least 6 388 * bits; round it up to 8 bits to make it 389 * easier. 390 */ 391 for (i = 0; i < sizeof(garbage) - 1; i++) { 392 const char *const base36 = 393 "0123456789" 394 "abcdefghijklmnopqrstuvwxyz"; 395 if (i % (sizeof(random) * 8 / 8) == 0) 396 random = arc4random(); 397 garbage[i] = 398 base36[(random & 0xff) % 36]; 399 random >>= 8; 400 } 401 garbage[i] = '\0'; 402 break; 403 case 'n': 404 nflag = 1; 405 break; 406 case 'o': 407 osname = optarg; 408 break; 409 case 'R': 410 Rflag = 2; 411 break; 412 case 'r': 413 rflag = 1; 414 break; 415 case 't': 416 switch (sscanf(optarg, "%d.%d", &sec, &usec)) { 417 case 2: 418 tv.tv_usec = usec; 419 case 1: 420 tv.tv_sec = sec; 421 break; 422 default: 423 if (debug) 424 warnx("bad -t argument"); 425 break; 426 } 427 break; 428 default: 429 break; 430 } 431 } 432 if (osname == NULL) { 433 if (uname(&un) == -1) 434 iderror(0, 0, s, errno); 435 osname = un.sysname; 436 } 437 len = sizeof(sin[0]); 438 if (getsockname(s, (struct sockaddr *)&sin[0], &len) == -1) 439 iderror(0, 0, s, errno); 440 len = sizeof(sin[1]); 441 if (getpeername(s, (struct sockaddr *)&sin[1], &len) == -1) 442 iderror(0, 0, s, errno); 443 /* 444 * We're going to prepare for and execute reception of a 445 * packet of data from the user. The data is in the format 446 * "local_port , foreign_port\r\n" (with local being the 447 * server's port and foreign being the client's.) 448 */ 449 FD_ZERO(&fdset); 450 FD_SET(s, &fdset); 451 if (select(s + 1, &fdset, NULL, NULL, &tv) == -1) 452 iderror(0, 0, s, errno); 453 if (ioctl(s, FIONREAD, &len) == -1) 454 iderror(0, 0, s, errno); 455 if (len >= sizeof(buf)) 456 len = sizeof(buf) - 1; 457 len = read(s, buf, len); 458 if (len == -1) 459 iderror(0, 0, s, errno); 460 buf[len] = '\0'; 461 if (sscanf(buf, "%hu , %hu", &lport, &fport) != 2) 462 iderror(0, 0, s, 0); 463 if (gflag) { 464 cp = garbage; 465 goto printit; 466 } 467 468 if (!rflag) /* Send HIDDEN-USER immediately if not "real" */ 469 iderror(lport, fport, s, -1); 470 /* 471 * We take the input and construct an array of two sockaddr_ins 472 * which contain the local address information and foreign 473 * address information, respectively, used to look up the 474 * credentials for the socket (which are returned by the 475 * sysctl "net.inet.tcp.getcred" when we call it.) The 476 * arrays have been filled in above via get{peer,sock}name(), 477 * so right here we are only setting the ports. 478 */ 479 sin[0].sin_port = htons(lport); 480 sin[1].sin_port = htons(fport); 481 len = sizeof(uc); 482 if (sysctlbyname("net.inet.tcp.getcred", &uc, &len, sin, 483 sizeof(sin)) == -1) { 484 if (fallback == NULL) /* Use a default, if asked to */ 485 iderror(lport, fport, s, errno); 486 usedfallback = 1; 487 } else { 488 /* Look up the pw to get the username */ 489 pw = getpwuid(uc.cr_uid); 490 } 491 if (pw == NULL && !usedfallback) /* No such user... */ 492 iderror(lport, fport, s, errno); 493 /* 494 * If enabled, we check for a file named ".noident" in the user's 495 * home directory. If found, we return HIDDEN-USER. 496 */ 497 if (nflag && !usedfallback) { 498 if (asprintf(&p, "%s/.noident", pw->pw_dir) == -1) 499 iderror(lport, fport, s, errno); 500 if (lstat(p, &sb) == 0) { 501 free(p); 502 iderror(lport, fport, s, -1); 503 } 504 free(p); 505 } 506 /* 507 * Here, if enabled, we read a user's ".fakeid" file in their 508 * home directory. It consists of a line containing the name 509 * they want. 510 */ 511 if (fflag && !usedfallback) { 512 FILE *fakeid = NULL; 513 514 if (asprintf(&p, "%s/.fakeid", pw->pw_dir) == -1) 515 iderror(lport, fport, s, errno); 516 /* 517 * Here we set ourself to effectively be the user, so we don't 518 * open any files we have no permission to open, especially 519 * symbolic links to sensitive root-owned files or devices. 520 */ 521 seteuid(pw->pw_uid); 522 setegid(pw->pw_gid); 523 /* 524 * If we were to lstat() here, it would do no good, since it 525 * would introduce a race condition and could be defeated. 526 * Therefore, we open the file we have permissions to open 527 * and if it's not a regular file, we close it and end up 528 * returning the user's real username. 529 */ 530 fakeid = fopen(p, "r"); 531 free(p); 532 if (fakeid != NULL && 533 fstat(fileno(fakeid), &sb) != -1 && S_ISREG(sb.st_mode)) { 534 buf[sizeof(buf) - 1] = '\0'; 535 if (fgets(buf, sizeof(buf), fakeid) == NULL) { 536 cp = pw->pw_name; 537 fclose(fakeid); 538 goto printit; 539 } 540 fclose(fakeid); 541 /* 542 * Usually, the file will have the desired identity 543 * in the form "identity\n", so we use strtok() to 544 * end the string (which fgets() doesn't do.) 545 */ 546 strtok(buf, "\r\n"); 547 /* User names of >16 characters are invalid */ 548 if (strlen(buf) > 16) 549 buf[16] = '\0'; 550 cp = buf; 551 /* Allow for beginning white space... */ 552 while (isspace(*cp)) 553 cp++; 554 /* ...and ending white space. */ 555 strtok(cp, " \t"); 556 /* 557 * If the name is a zero-length string or matches 558 * the name of another user, it's invalid, so 559 * we will return their real identity instead. 560 */ 561 562 if (!*cp || getpwnam(cp)) 563 cp = getpwuid(uc.cr_uid)->pw_name; 564 } else 565 cp = pw->pw_name; 566 } else if (!usedfallback) 567 cp = pw->pw_name; 568 else 569 cp = fallback; 570printit: 571 /* Finally, we make and send the reply. */ 572 if (asprintf(&p, "%d , %d : USERID : %s : %s\r\n", lport, fport, osname, 573 cp) == -1) { 574 syslog(LOG_ERR, "asprintf: %m"); 575 exit(EX_OSERR); 576 } 577 write(s, p, strlen(p)); 578 free(p); 579 580 exit(0); 581} 582 583/* 584 * RFC738 Time Server. 585 * Return a machine readable date and time, in the form of the 586 * number of seconds since midnight, Jan 1, 1900. Since gettimeofday 587 * returns the number of seconds since midnight, Jan 1, 1970, 588 * we must add 2208988800 seconds to this figure to make up for 589 * some seventy years Bell Labs was asleep. 590 */ 591 592unsigned long 593machtime() 594{ 595 struct timeval tv; 596 597 if (gettimeofday(&tv, (struct timezone *)NULL) < 0) { 598 if (debug) 599 warnx("unable to get time of day"); 600 return (0L); 601 } 602#define OFFSET ((u_long)25567 * 24*60*60) 603 return (htonl((long)(tv.tv_sec + OFFSET))); 604#undef OFFSET 605} 606 607/* ARGSUSED */ 608void 609machtime_dg(s, sep) 610 int s; 611 struct servtab *sep; 612{ 613 unsigned long result; 614 struct sockaddr_in sin; 615 int size; 616 617 size = sizeof(sin); 618 if (recvfrom(s, (char *)&result, sizeof(result), 0, 619 (struct sockaddr *)&sin, &size) < 0) 620 return; 621 622 if (check_loop(&sin, sep)) 623 return; 624 625 result = machtime(); 626 (void) sendto(s, (char *) &result, sizeof(result), 0, 627 (struct sockaddr *)&sin, sizeof(sin)); 628} 629 630/* ARGSUSED */ 631void 632machtime_stream(s, sep) 633 int s; 634 struct servtab *sep; 635{ 636 unsigned long result; 637 638 result = machtime(); 639 (void) write(s, (char *) &result, sizeof(result)); 640} 641 642/* 643 * RFC1078 TCP Port Service Multiplexer (TCPMUX). Service connections to 644 * services based on the service name sent. 645 * 646 * Based on TCPMUX.C by Mark K. Lottor November 1988 647 * sri-nic::ps:<mkl>tcpmux.c 648 */ 649 650#define MAX_SERV_LEN (256+2) /* 2 bytes for \r\n */ 651#define strwrite(fd, buf) (void) write(fd, buf, sizeof(buf)-1) 652 653static int /* # of characters upto \r,\n or \0 */ 654getline(fd, buf, len) 655 int fd; 656 char *buf; 657 int len; 658{ 659 int count = 0, n; 660 struct sigaction sa; 661 662 sa.sa_flags = 0; 663 sigemptyset(&sa.sa_mask); 664 sa.sa_handler = SIG_DFL; 665 sigaction(SIGALRM, &sa, (struct sigaction *)0); 666 do { 667 alarm(10); 668 n = read(fd, buf, len-count); 669 alarm(0); 670 if (n == 0) 671 return (count); 672 if (n < 0) 673 return (-1); 674 while (--n >= 0) { 675 if (*buf == '\r' || *buf == '\n' || *buf == '\0') 676 return (count); 677 count++; 678 buf++; 679 } 680 } while (count < len); 681 return (count); 682} 683 684struct servtab * 685tcpmux(s) 686 int s; 687{ 688 struct servtab *sep; 689 char service[MAX_SERV_LEN+1]; 690 int len; 691 692 /* Get requested service name */ 693 if ((len = getline(s, service, MAX_SERV_LEN)) < 0) { 694 strwrite(s, "-Error reading service name\r\n"); 695 return (NULL); 696 } 697 service[len] = '\0'; 698 699 if (debug) 700 warnx("tcpmux: someone wants %s", service); 701 702 /* 703 * Help is a required command, and lists available services, 704 * one per line. 705 */ 706 if (!strcasecmp(service, "help")) { 707 for (sep = servtab; sep; sep = sep->se_next) { 708 if (!ISMUX(sep)) 709 continue; 710 (void)write(s,sep->se_service,strlen(sep->se_service)); 711 strwrite(s, "\r\n"); 712 } 713 return (NULL); 714 } 715 716 /* Try matching a service in inetd.conf with the request */ 717 for (sep = servtab; sep; sep = sep->se_next) { 718 if (!ISMUX(sep)) 719 continue; 720 if (!strcasecmp(service, sep->se_service)) { 721 if (ISMUXPLUS(sep)) { 722 strwrite(s, "+Go\r\n"); 723 } 724 return (sep); 725 } 726 } 727 strwrite(s, "-Service not available\r\n"); 728 return (NULL); 729} 730