identd.c revision 1.20
1 /* $NetBSD: identd.c,v 1.20 2004/01/31 21:47:17 christos Exp $ */ 2 3 /* 4 * identd.c - TCP/IP Ident protocol server. 5 * 6 * This software is in the public domain. 7 * Written by Peter Postma <peter (at) pointless.nl> 8 */ 9 10 #include <sys/types.h> 11 #include <sys/socket.h> 12 #include <sys/stat.h> 13 #include <sys/param.h> 14 #include <sys/sysctl.h> 15 #include <sys/wait.h> 16 17 #include <netinet/in.h> 18 #include <netinet/ip_var.h> 19 #include <netinet/tcp.h> 20 #include <netinet/tcp_timer.h> 21 #include <netinet/tcp_var.h> 22 23 #include <arpa/inet.h> 24 25 #include <ctype.h> 26 #include <err.h> 27 #include <errno.h> 28 #include <fcntl.h> 29 #include <grp.h> 30 #include <netdb.h> 31 #include <poll.h> 32 #include <pwd.h> 33 #include <signal.h> 34 #include <stdio.h> 35 #include <stdlib.h> 36 #include <string.h> 37 #include <syslog.h> 38 #include <unistd.h> 39 40 #define OPSYS_NAME "UNIX" 41 #define IDENT_SERVICE "auth" 42 #define TIMEOUT 30 /* seconds */ 43 44 static int idhandle(int, const char *, const char *, const char *, 45 const char *, int); 46 static void idparse(int, int, int, const char *, const char *, const char *); 47 static void iderror(int, int, int, const char *); 48 static const char *gethost(struct sockaddr_storage *); 49 static int *socketsetup(const char *, const char *, int); 50 static int sysctl_getuid(struct sockaddr_storage *, socklen_t, uid_t *); 51 static int check_noident(const char *); 52 static int check_userident(const char *, char *, size_t); 53 static void random_string(char *, size_t); 54 static void change_format(const char *, struct passwd *, char *, size_t); 55 static void timeout_handler(int); 56 static void waitchild(int); 57 static void fatal(const char *); 58 59 static int bflag, eflag, fflag, Fflag, iflag, Iflag; 60 static int lflag, Lflag, nflag, Nflag, rflag; 61 62 int 63 main(int argc, char *argv[]) 64 { 65 int IPv4or6, ch, *socks, timeout; 66 char *address, *charset, *fmt; 67 const char *osname, *portno; 68 char *p; 69 char user[LOGIN_NAME_MAX]; 70 struct group *grp; 71 struct passwd *pw; 72 gid_t gid; 73 uid_t uid; 74 75 IPv4or6 = AF_UNSPEC; 76 osname = OPSYS_NAME; 77 portno = IDENT_SERVICE; 78 timeout = TIMEOUT; 79 address = NULL; 80 charset = NULL; 81 fmt = NULL; 82 socks = NULL; 83 gid = uid = 0; 84 bflag = eflag = fflag = Fflag = iflag = Iflag = 0; 85 lflag = Lflag = nflag = Nflag = rflag = 0; 86 87 /* Started from a tty? then run as daemon */ 88 if (isatty(0)) 89 bflag = 1; 90 91 /* Parse arguments */ 92 while ((ch = getopt(argc, argv, "46a:bceF:f:g:IiL:lNno:p:rt:u:")) != -1) 93 switch (ch) { 94 case '4': 95 IPv4or6 = AF_INET; 96 break; 97 case '6': 98 IPv4or6 = AF_INET6; 99 break; 100 case 'a': 101 address = optarg; 102 break; 103 case 'b': 104 bflag = 1; 105 break; 106 case 'c': 107 charset = optarg; 108 break; 109 case 'e': 110 eflag = 1; 111 break; 112 case 'F': 113 Fflag = 1; 114 fmt = optarg; 115 break; 116 case 'f': 117 fflag = 1; 118 (void)strlcpy(user, optarg, sizeof(user)); 119 break; 120 case 'g': 121 gid = (gid_t)strtol(optarg, &p, 0); 122 if (*p != '\0') { 123 if ((grp = getgrnam(optarg)) != NULL) 124 gid = grp->gr_gid; 125 else 126 errx(1, "No such group '%s'", optarg); 127 } 128 break; 129 case 'I': 130 Iflag = 1; 131 /* FALLTHROUGH */ 132 case 'i': 133 iflag = 1; 134 break; 135 case 'L': 136 Lflag = 1; 137 (void)strlcpy(user, optarg, sizeof(user)); 138 break; 139 case 'l': 140 lflag = 1; 141 break; 142 case 'N': 143 Nflag = 1; 144 break; 145 case 'n': 146 nflag = 1; 147 break; 148 case 'o': 149 osname = optarg; 150 break; 151 case 'p': 152 portno = optarg; 153 break; 154 case 'r': 155 rflag = 1; 156 break; 157 case 't': 158 timeout = (int)strtol(optarg, &p, 0); 159 if (*p != '\0') 160 errx(1, "Invalid timeout value '%s'", optarg); 161 break; 162 case 'u': 163 uid = (uid_t)strtol(optarg, &p, 0); 164 if (*p != '\0') { 165 if ((pw = getpwnam(optarg)) != NULL) { 166 uid = pw->pw_uid; 167 gid = pw->pw_gid; 168 } else 169 errx(1, "No such user '%s'", optarg); 170 } 171 break; 172 default: 173 exit(1); 174 } 175 176 if (lflag) 177 openlog("identd", LOG_PID, LOG_DAEMON); 178 179 /* Setup sockets if -b flag */ 180 if (bflag) { 181 socks = socketsetup(address, portno, IPv4or6); 182 if (socks == NULL) 183 return 1; 184 } 185 186 /* Switch to another uid/gid ? */ 187 if (gid && setgid(gid) == -1) { 188 if (lflag) 189 syslog(LOG_ERR, "setgid: %m"); 190 if (bflag) 191 warn("setgid"); 192 exit(1); 193 } 194 if (uid && setuid(uid) == -1) { 195 if (lflag) 196 syslog(LOG_ERR, "setuid: %m"); 197 if (bflag) 198 warn("setuid"); 199 exit(1); 200 } 201 202 /* Daemonize, setup pollfds and start mainloop if -b flag */ 203 if (bflag) { 204 int fd, i, nfds, rv; 205 struct pollfd *rfds; 206 207 (void)signal(SIGCHLD, waitchild); 208 (void)daemon(0, 0); 209 210 rfds = malloc(*socks * sizeof(struct pollfd)); 211 if (rfds == NULL) 212 fatal("malloc"); 213 nfds = *socks; 214 for (i = 0; i < nfds; i++) { 215 rfds[i].fd = socks[i+1]; 216 rfds[i].events = POLLIN; 217 rfds[i].revents = 0; 218 } 219 /* Mainloop for daemon */ 220 for (;;) { 221 rv = poll(rfds, nfds, INFTIM); 222 if (rv < 0 && errno == EINTR) 223 continue; 224 if (rv < 0) 225 fatal("poll"); 226 for (i = 0; i < nfds; i++) { 227 if (rfds[i].revents & POLLIN) { 228 fd = accept(rfds[i].fd, NULL, NULL); 229 if (fd < 0) { 230 if (lflag) 231 syslog(LOG_ERR, 232 "accept: %m"); 233 continue; 234 } 235 switch (fork()) { 236 case -1: /* error */ 237 if (lflag) 238 syslog(LOG_ERR, 239 "fork: %m"); 240 (void)sleep(1); 241 break; 242 case 0: /* child */ 243 (void)idhandle(fd, charset, 244 fmt, osname, user, timeout); 245 _exit(0); 246 default: /* parent */ 247 (void)close(fd); 248 } 249 } 250 } 251 } 252 } else 253 (void)idhandle(STDIN_FILENO, charset, fmt, osname, user, 254 timeout); 255 256 return 0; 257 } 258 259 static int 260 idhandle(int fd, const char *charset, const char *fmt, const char *osname, 261 const char *user, int timeout) 262 { 263 struct sockaddr_storage ss[2]; 264 char userbuf[LOGIN_NAME_MAX]; 265 char idbuf[LOGIN_NAME_MAX]; 266 char buf[BUFSIZ], *p; 267 int n, lport, fport; 268 struct passwd *pw; 269 socklen_t len; 270 uid_t uid; 271 272 lport = fport = 0; 273 274 (void)strlcpy(idbuf, user, sizeof(idbuf)); 275 (void)signal(SIGALRM, timeout_handler); 276 (void)alarm(timeout); 277 278 /* Get foreign internet address */ 279 len = sizeof(ss[0]); 280 if (getpeername(fd, (struct sockaddr *)&ss[0], &len) < 0) 281 fatal("getpeername"); 282 283 if (lflag) 284 syslog(LOG_INFO, "Connection from %s", gethost(&ss[0])); 285 286 /* Get local internet address */ 287 len = sizeof(ss[1]); 288 if (getsockname(fd, (struct sockaddr *)&ss[1], &len) < 0) 289 fatal("getsockname"); 290 291 /* Be sure to have the same address family's */ 292 if (ss[0].ss_family != ss[1].ss_family) { 293 if (lflag) 294 syslog(LOG_ERR, "Foreign/local AF are different!"); 295 return 1; 296 } 297 298 /* Receive data from the client */ 299 if ((n = recv(fd, buf, sizeof(buf) - 1, 0)) < 0) { 300 fatal("recv"); 301 } else if (n == 0) { 302 if (lflag) 303 syslog(LOG_NOTICE, "recv: EOF"); 304 iderror(fd, 0, 0, "UNKNOWN-ERROR"); 305 return 1; 306 } 307 buf[n] = '\0'; 308 309 /* Get local and remote ports from the received data */ 310 p = buf; 311 while (*p != '\0' && isspace(*p)) 312 p++; 313 if ((p = strtok(p, " \t,")) != NULL) { 314 lport = atoi(p); 315 if ((p = strtok(NULL, " \t,")) != NULL) 316 fport = atoi(p); 317 } 318 319 /* Are the ports valid? */ 320 if (lport < 1 || lport > 65535 || fport < 1 || fport > 65535) { 321 if (lflag) 322 syslog(LOG_NOTICE, "Invalid port(s): %d, %d from %s", 323 lport, fport, gethost(&ss[0])); 324 iderror(fd, 0, 0, eflag ? "UNKNOWN-ERROR" : "INVALID-PORT"); 325 return 1; 326 } 327 328 /* If there is a 'lie' user enabled, then handle it now and quit */ 329 if (Lflag) { 330 if (lflag) 331 syslog(LOG_NOTICE, "Lying with name %s to %s", 332 idbuf, gethost(&ss[0])); 333 idparse(fd, lport, fport, charset, osname, idbuf); 334 return 0; 335 } 336 337 /* Protocol dependent stuff */ 338 switch (ss[0].ss_family) { 339 case AF_INET: 340 ((struct sockaddr_in *)&ss[0])->sin_port = htons(fport); 341 ((struct sockaddr_in *)&ss[1])->sin_port = htons(lport); 342 break; 343 case AF_INET6: 344 ((struct sockaddr_in6 *)&ss[0])->sin6_port = htons(fport); 345 ((struct sockaddr_in6 *)&ss[1])->sin6_port = htons(lport); 346 break; 347 default: 348 if (lflag) 349 syslog(LOG_ERR, "Unsupported protocol, proto no. %d", 350 ss[0].ss_family); 351 return 1; 352 } 353 354 /* Do sysctl call */ 355 if (sysctl_getuid(ss, sizeof(ss), &uid) == -1) { 356 if (lflag) 357 syslog(LOG_ERR, "sysctl: %m"); 358 if (fflag) { 359 if (lflag) 360 syslog(LOG_NOTICE, "Using fallback name %s " 361 "to %s", idbuf, gethost(&ss[0])); 362 idparse(fd, lport, fport, charset, osname, idbuf); 363 return 0; 364 } 365 iderror(fd, lport, fport, eflag ? "UNKNOWN-ERROR" : "NO-USER"); 366 return 1; 367 } 368 369 /* Get username with the uid */ 370 if ((pw = getpwuid(uid)) == NULL) { 371 if (lflag) 372 syslog(LOG_ERR, "Couldn't map uid (%u) to name", uid); 373 (void)snprintf(idbuf, sizeof(idbuf), "%u", uid); 374 idparse(fd, lport, fport, charset, osname, idbuf); 375 return 0; 376 } 377 378 if (lflag) 379 syslog(LOG_INFO, "Successfull lookup: %d, %d: %s for %s", 380 lport, fport, pw->pw_name, gethost(&ss[0])); 381 382 /* No ident enabled? */ 383 if (Nflag && check_noident(pw->pw_dir)) { 384 if (lflag) 385 syslog(LOG_NOTICE, "Returning HIDDEN-USER for user %s" 386 " to %s", pw->pw_name, gethost(&ss[0])); 387 iderror(fd, lport, fport, "HIDDEN-USER"); 388 return 1; 389 } 390 391 /* User ident enabled ? */ 392 if (iflag && check_userident(pw->pw_dir, idbuf, sizeof(idbuf))) { 393 (void)strlcpy(userbuf, pw->pw_name, sizeof(userbuf)); 394 if (!Iflag) { 395 if (strspn(idbuf, "0123456789") && 396 getpwuid(atoi(idbuf)) != NULL) 397 (void)strlcpy(idbuf, userbuf, sizeof(idbuf)); 398 else if (getpwnam(idbuf) != NULL) 399 (void)strlcpy(idbuf, userbuf, sizeof(idbuf)); 400 } 401 if (lflag) 402 syslog(LOG_NOTICE, "Returning user specified '%s' for " 403 "user %s to %s", idbuf, userbuf, gethost(&ss[0])); 404 idparse(fd, lport, fport, charset, osname, idbuf); 405 return 0; 406 } 407 408 /* Send random crap? */ 409 if (rflag) { 410 /* Random number or string? */ 411 if (nflag) 412 (void)snprintf(idbuf, sizeof(idbuf), "%u", 413 (unsigned int)(arc4random() % 65535)); 414 else 415 random_string(idbuf, sizeof(idbuf)); 416 417 if (lflag) 418 syslog(LOG_NOTICE, "Returning random '%s' for user %s" 419 " to %s", idbuf, pw->pw_name, gethost(&ss[0])); 420 idparse(fd, lport, fport, charset, osname, idbuf); 421 return 0; 422 } 423 424 /* Return number? */ 425 if (nflag) 426 (void)snprintf(idbuf, sizeof(idbuf), "%u", uid); 427 else 428 (void)strlcpy(idbuf, pw->pw_name, sizeof(idbuf)); 429 430 if (Fflag) { 431 /* RFC 1413 says that 512 is the limit */ 432 change_format(fmt, pw, buf, 512); 433 idparse(fd, lport, fport, charset, osname, buf); 434 } else 435 idparse(fd, lport, fport, charset, osname, idbuf); 436 437 return 0; 438 } 439 440 /* Send/parse the ident result */ 441 static void 442 idparse(int fd, int lport, int fport, const char *charset, const char *osname, 443 const char *user) 444 { 445 char *p; 446 447 if (asprintf(&p, "%d , %d : USERID : %s%s%s : %s\r\n", lport, fport, 448 osname, charset ? " , " : "", charset ? charset : "", user) < 0) 449 fatal("asprintf"); 450 if (send(fd, p, strlen(p), 0) < 0) { 451 free(p); 452 fatal("send"); 453 } 454 free(p); 455 } 456 457 /* Return a specified ident error */ 458 static void 459 iderror(int fd, int lport, int fport, const char *error) 460 { 461 char *p; 462 463 if (asprintf(&p, "%d , %d : ERROR : %s\r\n", lport, fport, error) < 0) 464 fatal("asprintf"); 465 if (send(fd, p, strlen(p), 0) < 0) { 466 free(p); 467 fatal("send"); 468 } 469 free(p); 470 } 471 472 /* Return the IP address of the connecting host */ 473 static const char * 474 gethost(struct sockaddr_storage *ss) 475 { 476 static char host[NI_MAXHOST]; 477 478 if (getnameinfo((struct sockaddr *)ss, ss->ss_len, host, 479 sizeof(host), NULL, 0, NI_NUMERICHOST) == 0) 480 return host; 481 482 return "UNKNOWN"; 483 } 484 485 /* Setup sockets, for daemon mode */ 486 static int * 487 socketsetup(const char *address, const char *port, int af) 488 { 489 struct addrinfo hints, *res, *res0; 490 int error, maxs, *s, *socks, y = 1; 491 const char *cause = NULL; 492 493 (void)memset(&hints, 0, sizeof(hints)); 494 hints.ai_flags = AI_PASSIVE; 495 hints.ai_family = af; 496 hints.ai_socktype = SOCK_STREAM; 497 error = getaddrinfo(address, port, &hints, &res0); 498 if (error) { 499 if (lflag) 500 syslog(LOG_ERR, "getaddrinfo: %s", gai_strerror(error)); 501 errx(1, "%s", gai_strerror(error)); 502 /*NOTREACHED*/ 503 } 504 505 /* Count max number of sockets we may open */ 506 for (maxs = 0, res = res0; res != NULL; res = res->ai_next) 507 maxs++; 508 509 socks = malloc((maxs + 1) * sizeof(int)); 510 if (socks == NULL) { 511 if (lflag) 512 syslog(LOG_ERR, "malloc: %m"); 513 err(1, "malloc"); 514 /* NOTREACHED */ 515 } 516 517 *socks = 0; 518 s = socks + 1; 519 for (res = res0; res != NULL; res = res->ai_next) { 520 *s = socket(res->ai_family, res->ai_socktype, res->ai_protocol); 521 if (*s < 0) { 522 cause = "socket"; 523 continue; 524 } 525 (void)setsockopt(*s, SOL_SOCKET, SO_REUSEADDR, &y, sizeof(y)); 526 if (bind(*s, res->ai_addr, res->ai_addrlen) < 0) { 527 cause = "bind"; 528 (void)close(*s); 529 continue; 530 } 531 if (listen(*s, 5) < 0) { 532 cause = "listen"; 533 (void)close(*s); 534 continue; 535 } 536 *socks = *socks + 1; 537 s++; 538 } 539 540 if (*socks == 0) { 541 free(socks); 542 if (lflag) 543 syslog(LOG_ERR, "%s: %m", cause); 544 err(1, "%s", cause); 545 /* NOTREACHED */ 546 } 547 if (res0) 548 freeaddrinfo(res0); 549 550 return socks; 551 } 552 553 /* Return the UID for the connection owner */ 554 static int 555 sysctl_getuid(struct sockaddr_storage *ss, socklen_t len, uid_t *uid) 556 { 557 int mib[4]; 558 uid_t myuid; 559 size_t uidlen; 560 561 uidlen = sizeof(myuid); 562 563 mib[0] = CTL_NET; 564 mib[1] = ss->ss_family; 565 mib[2] = IPPROTO_TCP; 566 mib[3] = TCPCTL_IDENT; 567 568 if (sysctl(mib, sizeof(mib)/ sizeof(int), &myuid, &uidlen, ss, len) < 0) 569 return -1; 570 *uid = myuid; 571 572 return 0; 573 } 574 575 /* Check if a .noident file exists in the user home directory */ 576 static int 577 check_noident(const char *homedir) 578 { 579 struct stat sb; 580 char *path; 581 int ret; 582 583 if (homedir == NULL) 584 return 0; 585 if (asprintf(&path, "%s/.noident", homedir) < 0) 586 return 0; 587 ret = stat(path, &sb); 588 589 free(path); 590 return (ret == 0); 591 } 592 593 /* 594 * Check if a .ident file exists in the user home directory and 595 * return the contents of that file. 596 */ 597 static int 598 check_userident(const char *homedir, char *username, size_t len) 599 { 600 struct stat sb; 601 char *path, *p; 602 int fd, n; 603 604 if (len == 0 || homedir == NULL) 605 return 0; 606 if (asprintf(&path, "%s/.ident", homedir) < 0) 607 return 0; 608 if ((fd = open(path, O_RDONLY|O_NONBLOCK|O_NOFOLLOW, 0)) < 0) { 609 free(path); 610 return 0; 611 } 612 if (fstat(fd, &sb) < 0 || !S_ISREG(sb.st_mode)) { 613 (void)close(fd); 614 free(path); 615 return 0; 616 } 617 if ((n = read(fd, username, len - 1)) < 1) { 618 (void)close(fd); 619 free(path); 620 return 0; 621 } 622 username[n] = '\0'; 623 624 if ((p = strpbrk(username, "\r\n"))) 625 *p = '\0'; 626 627 (void)close(fd); 628 free(path); 629 return 1; 630 } 631 632 /* Generate a random string */ 633 static void 634 random_string(char *str, size_t len) 635 { 636 static const char chars[] = "abcdefghijklmnopqrstuvwxyz1234567890"; 637 char *p; 638 639 if (len == 0) 640 return; 641 for (p = str; len > 1; len--) 642 *p++ = chars[arc4random() % (sizeof(chars) - 1)]; 643 *p = '\0'; 644 } 645 646 /* Change the output format */ 647 static void 648 change_format(const char *format, struct passwd *pw, char *dest, size_t len) 649 { 650 struct group *gr; 651 const char *cp; 652 char **gmp; 653 int bp; 654 655 if (len == 0) 656 return; 657 if ((gr = getgrgid(pw->pw_gid)) == NULL) 658 return; 659 660 for (bp = 0, cp = format; *cp != '\0' && bp < 490; cp++) { 661 if (*cp != '%') { 662 dest[bp++] = *cp; 663 continue; 664 } 665 if (*++cp == '\0') 666 break; 667 switch (*cp) { 668 case 'u': 669 (void)snprintf(&dest[bp], len - bp, "%.*s", 490 - bp, 670 pw->pw_name); 671 break; 672 case 'U': 673 (void)snprintf(&dest[bp], len - bp, "%d", pw->pw_uid); 674 break; 675 case 'g': 676 (void)snprintf(&dest[bp], len - bp, "%.*s", 490 - bp, 677 gr->gr_name); 678 break; 679 case 'G': 680 (void)snprintf(&dest[bp], len - bp, "%d", gr->gr_gid); 681 break; 682 case 'l': 683 (void)snprintf(&dest[bp], len - bp, "%.*s", 490 - bp, 684 gr->gr_name); 685 bp += strlen(&dest[bp]); 686 if (bp >= 490) 687 break; 688 setgrent(); 689 while ((gr = getgrent()) != NULL) { 690 if (gr->gr_gid == pw->pw_gid) 691 continue; 692 for (gmp = gr->gr_mem; *gmp && **gmp; gmp++) { 693 if (strcmp(*gmp, pw->pw_name) == 0) { 694 (void)snprintf(&dest[bp], 695 len - bp, ",%.*s", 696 490 - bp, gr->gr_name); 697 bp += strlen(&dest[bp]); 698 break; 699 } 700 } 701 if (bp >= 490) 702 break; 703 } 704 endgrent(); 705 break; 706 case 'L': 707 (void)snprintf(&dest[bp], len - bp, "%u", gr->gr_gid); 708 bp += strlen(&dest[bp]); 709 if (bp >= 490) 710 break; 711 setgrent(); 712 while ((gr = getgrent()) != NULL) { 713 if (gr->gr_gid == pw->pw_gid) 714 continue; 715 for (gmp = gr->gr_mem; *gmp && **gmp; gmp++) { 716 if (strcmp(*gmp, pw->pw_name) == 0) { 717 (void)snprintf(&dest[bp], 718 len - bp, ",%u", 719 gr->gr_gid); 720 bp += strlen(&dest[bp]); 721 break; 722 } 723 } 724 if (bp >= 490) 725 break; 726 } 727 endgrent(); 728 break; 729 default: 730 dest[bp] = *cp; 731 dest[bp+1] = '\0'; 732 break; 733 } 734 bp += strlen(&dest[bp]); 735 } 736 if (bp >= 490) { 737 (void)snprintf(&dest[490], len - 490, "..."); 738 bp = 493; 739 } 740 dest[bp] = '\0'; 741 } 742 743 /* Just exit when we caught SIGALRM */ 744 static void 745 timeout_handler(int s) 746 { 747 if (lflag) 748 syslog(LOG_DEBUG, "SIGALRM triggered, exiting..."); 749 exit(1); 750 } 751 752 /* This is to clean up zombie processes when in daemon mode */ 753 static void 754 waitchild(int s) 755 { 756 while (waitpid(-1, NULL, WNOHANG) > 0) 757 continue; 758 } 759 760 /* Report errno through syslog and quit */ 761 static void 762 fatal(const char *func) 763 { 764 if (lflag) 765 syslog(LOG_ERR, "%s: %m", func); 766 exit(1); 767 } 768
Indexes created Tue Sep 23 02:09:52 GMT 2025