builtins.c revision 56590
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 56590 2000-01-25 14:52:10Z shin $ 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 *, 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_storage ss; 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(ss); 125 if (recvfrom(s, text, sizeof(text), 0, 126 (struct sockaddr *)&ss, &size) < 0) 127 return; 128 129 if (check_loop((struct sockaddr *)&ss, 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 *)&ss, sizeof(ss)); 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_storage ss; 193 int size; 194 195 clock = time((time_t *) 0); 196 197 size = sizeof(ss); 198 if (recvfrom(s, buffer, sizeof(buffer), 0, 199 (struct sockaddr *)&ss, &size) < 0) 200 return; 201 202 if (check_loop((struct sockaddr *)&ss, sep)) 203 return; 204 205 (void) sprintf(buffer, "%.24s\r\n", ctime(&clock)); 206 (void) sendto(s, buffer, strlen(buffer), 0, 207 (struct sockaddr *)&ss, sizeof(ss)); 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_storage ss; 274 275 size = sizeof(ss); 276 if ((i = recvfrom(s, buffer, sizeof(buffer), 0, 277 (struct sockaddr *)&ss, &size)) < 0) 278 return; 279 280 if (check_loop((struct sockaddr *)&ss, sep)) 281 return; 282 283 (void) sendto(s, buffer, i, 0, (struct sockaddr *)&ss, 284 sizeof(ss)); 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 sockaddr_in6 sin6[2]; 339 struct sockaddr_storage ss[2]; 340 struct ucred uc; 341 struct timeval tv = { 342 10, 343 0 344 }; 345 struct passwd *pw = NULL; 346 fd_set fdset; 347 char buf[BUFSIZE], *cp = NULL, *p, **av, *osname = NULL, garbage[7]; 348 char *fallback = NULL; 349 int len, c, fflag = 0, nflag = 0, rflag = 0, argc = 0, usedfallback = 0; 350 int gflag = 0, Rflag = 0, getcredfail = 0; 351 u_short lport, fport; 352 353 inetd_setproctitle(sep->se_service, s); 354 /* 355 * Reset getopt() since we are a fork() but not an exec() from 356 * a parent which used getopt() already. 357 */ 358 optind = 1; 359 optreset = 1; 360 /* 361 * Take the internal argument vector and count it out to make an 362 * argument count for getopt. This can be used for any internal 363 * service to read arguments and use getopt() easily. 364 */ 365 for (av = sep->se_argv; *av; av++) 366 argc++; 367 if (argc) { 368 int sec, usec; 369 size_t i; 370 u_int32_t random; 371 372 while ((c = getopt(argc, sep->se_argv, "d:fgno:rt:")) != -1) 373 switch (c) { 374 case 'd': 375 fallback = optarg; 376 break; 377 case 'f': 378 fflag = 1; 379 break; 380 case 'g': 381 gflag = 1; 382 random = 0; /* Shush, compiler. */ 383 /* 384 * The number of bits in "random" divided 385 * by the number of bits needed per iteration 386 * gives a more optimal way to reload the 387 * random number only when necessary. 388 * 389 * I'm using base-36, so I need at least 6 390 * bits; round it up to 8 bits to make it 391 * easier. 392 */ 393 for (i = 0; i < sizeof(garbage) - 1; i++) { 394 const char *const base36 = 395 "0123456789" 396 "abcdefghijklmnopqrstuvwxyz"; 397 if (i % (sizeof(random) * 8 / 8) == 0) 398 random = arc4random(); 399 garbage[i] = 400 base36[(random & 0xff) % 36]; 401 random >>= 8; 402 } 403 garbage[i] = '\0'; 404 break; 405 case 'n': 406 nflag = 1; 407 break; 408 case 'o': 409 osname = optarg; 410 break; 411 case 'R': 412 Rflag = 2; 413 break; 414 case 'r': 415 rflag = 1; 416 break; 417 case 't': 418 switch (sscanf(optarg, "%d.%d", &sec, &usec)) { 419 case 2: 420 tv.tv_usec = usec; 421 case 1: 422 tv.tv_sec = sec; 423 break; 424 default: 425 if (debug) 426 warnx("bad -t argument"); 427 break; 428 } 429 break; 430 default: 431 break; 432 } 433 } 434 if (osname == NULL) { 435 if (uname(&un) == -1) 436 iderror(0, 0, s, errno); 437 osname = un.sysname; 438 } 439 len = sizeof(ss[0]); 440 if (getsockname(s, (struct sockaddr *)&ss[0], &len) == -1) 441 iderror(0, 0, s, errno); 442 len = sizeof(ss[1]); 443 if (getpeername(s, (struct sockaddr *)&ss[1], &len) == -1) 444 iderror(0, 0, s, errno); 445 /* 446 * We're going to prepare for and execute reception of a 447 * packet of data from the user. The data is in the format 448 * "local_port , foreign_port\r\n" (with local being the 449 * server's port and foreign being the client's.) 450 */ 451 FD_ZERO(&fdset); 452 FD_SET(s, &fdset); 453 if (select(s + 1, &fdset, NULL, NULL, &tv) == -1) 454 iderror(0, 0, s, errno); 455 if (ioctl(s, FIONREAD, &len) == -1) 456 iderror(0, 0, s, errno); 457 if (len >= sizeof(buf)) 458 len = sizeof(buf) - 1; 459 len = read(s, buf, len); 460 if (len == -1) 461 iderror(0, 0, s, errno); 462 buf[len] = '\0'; 463 if (sscanf(buf, "%hu , %hu", &lport, &fport) != 2) 464 iderror(0, 0, s, 0); 465 if (gflag) { 466 cp = garbage; 467 goto printit; 468 } 469 470 if (!rflag) /* Send HIDDEN-USER immediately if not "real" */ 471 iderror(lport, fport, s, -1); 472 /* 473 * We take the input and construct an array of two sockaddr_ins 474 * which contain the local address information and foreign 475 * address information, respectively, used to look up the 476 * credentials for the socket (which are returned by the 477 * sysctl "net.inet.tcp.getcred" when we call it.) The 478 * arrays have been filled in above via get{peer,sock}name(), 479 * so right here we are only setting the ports. 480 */ 481 if (ss[0].ss_family != ss[1].ss_family) 482 iderror(lport, fport, s, errno); 483 len = sizeof(uc); 484 switch (ss[0].ss_family) { 485 case AF_INET: 486 sin[0] = *(struct sockaddr_in *)&ss[0]; 487 sin[0].sin_port = htons(lport); 488 sin[1] = *(struct sockaddr_in *)&ss[1]; 489 sin[1].sin_port = htons(fport); 490 if (sysctlbyname("net.inet.tcp.getcred", &uc, &len, sin, 491 sizeof(sin)) == -1) 492 getcredfail = 1; 493 break; 494#ifdef INET6 495 case AF_INET6: 496 sin6[0] = *(struct sockaddr_in6 *)&ss[0]; 497 sin6[0].sin6_port = htons(lport); 498 sin6[1] = *(struct sockaddr_in6 *)&ss[1]; 499 sin6[1].sin6_port = htons(fport); 500 if (sysctlbyname("net.inet6.tcp6.getcred", &uc, &len, sin6, 501 sizeof(sin6)) == -1) 502 getcredfail = 1; 503 break; 504#endif 505 default: /* should not reach here */ 506 getcredfail = 1; 507 break; 508 } 509 if (getcredfail != 0) { 510 if (fallback == NULL) /* Use a default, if asked to */ 511 iderror(lport, fport, s, errno); 512 usedfallback = 1; 513 } else { 514 /* Look up the pw to get the username */ 515 pw = getpwuid(uc.cr_uid); 516 } 517 if (pw == NULL && !usedfallback) /* No such user... */ 518 iderror(lport, fport, s, errno); 519 /* 520 * If enabled, we check for a file named ".noident" in the user's 521 * home directory. If found, we return HIDDEN-USER. 522 */ 523 if (nflag && !usedfallback) { 524 if (asprintf(&p, "%s/.noident", pw->pw_dir) == -1) 525 iderror(lport, fport, s, errno); 526 if (lstat(p, &sb) == 0) { 527 free(p); 528 iderror(lport, fport, s, -1); 529 } 530 free(p); 531 } 532 /* 533 * Here, if enabled, we read a user's ".fakeid" file in their 534 * home directory. It consists of a line containing the name 535 * they want. 536 */ 537 if (fflag && !usedfallback) { 538 FILE *fakeid = NULL; 539 540 if (asprintf(&p, "%s/.fakeid", pw->pw_dir) == -1) 541 iderror(lport, fport, s, errno); 542 /* 543 * Here we set ourself to effectively be the user, so we don't 544 * open any files we have no permission to open, especially 545 * symbolic links to sensitive root-owned files or devices. 546 */ 547 seteuid(pw->pw_uid); 548 setegid(pw->pw_gid); 549 /* 550 * If we were to lstat() here, it would do no good, since it 551 * would introduce a race condition and could be defeated. 552 * Therefore, we open the file we have permissions to open 553 * and if it's not a regular file, we close it and end up 554 * returning the user's real username. 555 */ 556 fakeid = fopen(p, "r"); 557 free(p); 558 if (fakeid != NULL && 559 fstat(fileno(fakeid), &sb) != -1 && S_ISREG(sb.st_mode)) { 560 buf[sizeof(buf) - 1] = '\0'; 561 if (fgets(buf, sizeof(buf), fakeid) == NULL) { 562 cp = pw->pw_name; 563 fclose(fakeid); 564 goto printit; 565 } 566 fclose(fakeid); 567 /* 568 * Usually, the file will have the desired identity 569 * in the form "identity\n", so we use strtok() to 570 * end the string (which fgets() doesn't do.) 571 */ 572 strtok(buf, "\r\n"); 573 /* User names of >16 characters are invalid */ 574 if (strlen(buf) > 16) 575 buf[16] = '\0'; 576 cp = buf; 577 /* Allow for beginning white space... */ 578 while (isspace(*cp)) 579 cp++; 580 /* ...and ending white space. */ 581 strtok(cp, " \t"); 582 /* 583 * If the name is a zero-length string or matches 584 * the name of another user, it's invalid, so 585 * we will return their real identity instead. 586 */ 587 588 if (!*cp || getpwnam(cp)) 589 cp = getpwuid(uc.cr_uid)->pw_name; 590 } else 591 cp = pw->pw_name; 592 } else if (!usedfallback) 593 cp = pw->pw_name; 594 else 595 cp = fallback; 596printit: 597 /* Finally, we make and send the reply. */ 598 if (asprintf(&p, "%d , %d : USERID : %s : %s\r\n", lport, fport, osname, 599 cp) == -1) { 600 syslog(LOG_ERR, "asprintf: %m"); 601 exit(EX_OSERR); 602 } 603 write(s, p, strlen(p)); 604 free(p); 605 606 exit(0); 607} 608 609/* 610 * RFC738 Time Server. 611 * Return a machine readable date and time, in the form of the 612 * number of seconds since midnight, Jan 1, 1900. Since gettimeofday 613 * returns the number of seconds since midnight, Jan 1, 1970, 614 * we must add 2208988800 seconds to this figure to make up for 615 * some seventy years Bell Labs was asleep. 616 */ 617 618unsigned long 619machtime() 620{ 621 struct timeval tv; 622 623 if (gettimeofday(&tv, (struct timezone *)NULL) < 0) { 624 if (debug) 625 warnx("unable to get time of day"); 626 return (0L); 627 } 628#define OFFSET ((u_long)25567 * 24*60*60) 629 return (htonl((long)(tv.tv_sec + OFFSET))); 630#undef OFFSET 631} 632 633/* ARGSUSED */ 634void 635machtime_dg(s, sep) 636 int s; 637 struct servtab *sep; 638{ 639 unsigned long result; 640 struct sockaddr_storage ss; 641 int size; 642 643 size = sizeof(ss); 644 if (recvfrom(s, (char *)&result, sizeof(result), 0, 645 (struct sockaddr *)&ss, &size) < 0) 646 return; 647 648 if (check_loop((struct sockaddr *)&ss, sep)) 649 return; 650 651 result = machtime(); 652 (void) sendto(s, (char *) &result, sizeof(result), 0, 653 (struct sockaddr *)&ss, sizeof(ss)); 654} 655 656/* ARGSUSED */ 657void 658machtime_stream(s, sep) 659 int s; 660 struct servtab *sep; 661{ 662 unsigned long result; 663 664 result = machtime(); 665 (void) write(s, (char *) &result, sizeof(result)); 666} 667 668/* 669 * RFC1078 TCP Port Service Multiplexer (TCPMUX). Service connections to 670 * services based on the service name sent. 671 * 672 * Based on TCPMUX.C by Mark K. Lottor November 1988 673 * sri-nic::ps:<mkl>tcpmux.c 674 */ 675 676#define MAX_SERV_LEN (256+2) /* 2 bytes for \r\n */ 677#define strwrite(fd, buf) (void) write(fd, buf, sizeof(buf)-1) 678 679static int /* # of characters upto \r,\n or \0 */ 680getline(fd, buf, len) 681 int fd; 682 char *buf; 683 int len; 684{ 685 int count = 0, n; 686 struct sigaction sa; 687 688 sa.sa_flags = 0; 689 sigemptyset(&sa.sa_mask); 690 sa.sa_handler = SIG_DFL; 691 sigaction(SIGALRM, &sa, (struct sigaction *)0); 692 do { 693 alarm(10); 694 n = read(fd, buf, len-count); 695 alarm(0); 696 if (n == 0) 697 return (count); 698 if (n < 0) 699 return (-1); 700 while (--n >= 0) { 701 if (*buf == '\r' || *buf == '\n' || *buf == '\0') 702 return (count); 703 count++; 704 buf++; 705 } 706 } while (count < len); 707 return (count); 708} 709 710struct servtab * 711tcpmux(s) 712 int s; 713{ 714 struct servtab *sep; 715 char service[MAX_SERV_LEN+1]; 716 int len; 717 718 /* Get requested service name */ 719 if ((len = getline(s, service, MAX_SERV_LEN)) < 0) { 720 strwrite(s, "-Error reading service name\r\n"); 721 return (NULL); 722 } 723 service[len] = '\0'; 724 725 if (debug) 726 warnx("tcpmux: someone wants %s", service); 727 728 /* 729 * Help is a required command, and lists available services, 730 * one per line. 731 */ 732 if (!strcasecmp(service, "help")) { 733 for (sep = servtab; sep; sep = sep->se_next) { 734 if (!ISMUX(sep)) 735 continue; 736 (void)write(s,sep->se_service,strlen(sep->se_service)); 737 strwrite(s, "\r\n"); 738 } 739 return (NULL); 740 } 741 742 /* Try matching a service in inetd.conf with the request */ 743 for (sep = servtab; sep; sep = sep->se_next) { 744 if (!ISMUX(sep)) 745 continue; 746 if (!strcasecmp(service, sep->se_service)) { 747 if (ISMUXPLUS(sep)) { 748 strwrite(s, "+Go\r\n"); 749 } 750 return (sep); 751 } 752 } 753 strwrite(s, "-Service not available\r\n"); 754 return (NULL); 755} 756