1 /* 2 * Copyright (c) 1983, 1993 Regents of the University of California. 3 * All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 */ 7 8 #ifndef lint 9 char copyright[] = 10 "@(#) Copyright (c) 1983, 1993 Regents of the University of California.\n\ 11 All rights reserved.\n"; 12 #endif /* not lint */ 13 14 #ifndef lint 15 static char sccsid[] = "@(#)tftpd.c 5.15 (Berkeley) 05/16/93"; 16 #endif /* not lint */ 17 18 /* 19 * Trivial file transfer protocol server. 20 * 21 * This version includes many modifications by Jim Guyton 22 * <guyton@rand-unix>. 23 */ 24 25 #include <sys/param.h> 26 #include <sys/ioctl.h> 27 #include <sys/stat.h> 28 #include <sys/socket.h> 29 30 #include <netinet/in.h> 31 #include <arpa/tftp.h> 32 #include <arpa/inet.h> 33 34 #include <ctype.h> 35 #include <errno.h> 36 #include <fcntl.h> 37 #include <netdb.h> 38 #include <setjmp.h> 39 #include <signal.h> 40 #include <stdio.h> 41 #include <stdlib.h> 42 #include <string.h> 43 #include <syslog.h> 44 #include <unistd.h> 45 46 #include "tftpsubs.h" 47 #include "pathnames.h" 48 49 #define TIMEOUT 5 50 51 int peer; 52 int rexmtval = TIMEOUT; 53 int maxtimeout = 5*TIMEOUT; 54 55 #define PKTSIZE SEGSIZE+4 56 char buf[PKTSIZE]; 57 char ackbuf[PKTSIZE]; 58 struct sockaddr_in from; 59 int fromlen; 60 61 void tftp __P((struct tftphdr *, int)); 62 63 /* 64 * Null-terminated directory prefix list for absolute pathname requests and 65 * search list for relative pathname requests. 66 * 67 * MAXDIRS should be at least as large as the number of arguments that 68 * inetd allows (currently 20). 69 */ 70 #define MAXDIRS 20 71 static struct dirlist { 72 char *name; 73 int len; 74 } dirs[MAXDIRS+1]; 75 static int suppress_naks; 76 static int logging; 77 78 static char *errtomsg __P((int)); 79 static void nak __P((int)); 80 static char *verifyhost __P((struct sockaddr_in *)); 81 82 int 83 main(argc, argv) 84 int argc; 85 char *argv[]; 86 { 87 register struct tftphdr *tp; 88 register int n; 89 int ch, on; 90 struct sockaddr_in sin; 91 92 openlog("tftpd", LOG_PID, LOG_FTP); 93 while ((ch = getopt(argc, argv, "ln")) != EOF) { 94 switch (ch) { 95 case 'l': 96 logging = 1; 97 break; 98 case 'n': 99 suppress_naks = 1; 100 break; 101 default: 102 syslog(LOG_WARNING, "ignoring unknown option -%c", ch); 103 } 104 } 105 if (optind < argc) { 106 struct dirlist *dirp; 107 108 /* Get list of directory prefixes. Skip relative pathnames. */ 109 for (dirp = dirs; optind < argc && dirp < &dirs[MAXDIRS]; 110 optind++) { 111 if (argv[optind][0] == '/') { 112 dirp->name = argv[optind]; 113 dirp->len = strlen(dirp->name); 114 dirp++; 115 } 116 } 117 } 118 119 on = 1; 120 if (ioctl(0, FIONBIO, &on) < 0) { 121 syslog(LOG_ERR, "ioctl(FIONBIO): %m\n"); 122 exit(1); 123 } 124 fromlen = sizeof (from); 125 n = recvfrom(0, buf, sizeof (buf), 0, 126 (struct sockaddr *)&from, &fromlen); 127 if (n < 0) { 128 syslog(LOG_ERR, "recvfrom: %m\n"); 129 exit(1); 130 } 131 /* 132 * Now that we have read the message out of the UDP 133 * socket, we fork and exit. Thus, inetd will go back 134 * to listening to the tftp port, and the next request 135 * to come in will start up a new instance of tftpd. 136 * 137 * We do this so that inetd can run tftpd in "wait" mode. 138 * The problem with tftpd running in "nowait" mode is that 139 * inetd may get one or more successful "selects" on the 140 * tftp port before we do our receive, so more than one 141 * instance of tftpd may be started up. Worse, if tftpd 142 * break before doing the above "recvfrom", inetd would 143 * spawn endless instances, clogging the system. 144 */ 145 { 146 int pid; 147 int i, j; 148 149 for (i = 1; i < 20; i++) { 150 pid = fork(); 151 if (pid < 0) { 152 sleep(i); 153 /* 154 * flush out to most recently sent request. 155 * 156 * This may drop some request, but those 157 * will be resent by the clients when 158 * they timeout. The positive effect of 159 * this flush is to (try to) prevent more 160 * than one tftpd being started up to service 161 * a single request from a single client. 162 */ 163 j = sizeof from; 164 i = recvfrom(0, buf, sizeof (buf), 0, 165 (struct sockaddr *)&from, &j); 166 if (i > 0) { 167 n = i; 168 fromlen = j; 169 } 170 } else { 171 break; 172 } 173 } 174 if (pid < 0) { 175 syslog(LOG_ERR, "fork: %m\n"); 176 exit(1); 177 } else if (pid != 0) { 178 exit(0); 179 } 180 } 181 from.sin_family = AF_INET; 182 alarm(0); 183 close(0); 184 close(1); 185 peer = socket(AF_INET, SOCK_DGRAM, 0); 186 if (peer < 0) { 187 syslog(LOG_ERR, "socket: %m\n"); 188 exit(1); 189 } 190 memset(&sin, 0, sizeof(sin)); 191 sin.sin_family = AF_INET; 192 if (bind(peer, (struct sockaddr *)&sin, sizeof (sin)) < 0) { 193 syslog(LOG_ERR, "bind: %m\n"); 194 exit(1); 195 } 196 if (connect(peer, (struct sockaddr *)&from, sizeof(from)) < 0) { 197 syslog(LOG_ERR, "connect: %m\n"); 198 exit(1); 199 } 200 tp = (struct tftphdr *)buf; 201 tp->th_opcode = ntohs(tp->th_opcode); 202 if (tp->th_opcode == RRQ || tp->th_opcode == WRQ) 203 tftp(tp, n); 204 exit(1); 205 } 206 207 struct formats; 208 int validate_access __P((char **, int)); 209 void sendfile __P((struct formats *)); 210 void recvfile __P((struct formats *)); 211 212 struct formats { 213 char *f_mode; 214 int (*f_validate) __P((char **, int)); 215 void (*f_send) __P((struct formats *)); 216 void (*f_recv) __P((struct formats *)); 217 int f_convert; 218 } formats[] = { 219 { "netascii", validate_access, sendfile, recvfile, 1 }, 220 { "octet", validate_access, sendfile, recvfile, 0 }, 221 #ifdef notdef 222 { "mail", validate_user, sendmail, recvmail, 1 }, 223 #endif 224 { 0 } 225 }; 226 227 /* 228 * Handle initial connection protocol. 229 */ 230 void 231 tftp(tp, size) 232 struct tftphdr *tp; 233 int size; 234 { 235 register char *cp; 236 int first = 1, ecode; 237 register struct formats *pf; 238 char *filename, *mode; 239 240 filename = cp = tp->th_stuff; 241 again: 242 while (cp < buf + size) { 243 if (*cp == '\0') 244 break; 245 cp++; 246 } 247 if (*cp != '\0') { 248 nak(EBADOP); 249 exit(1); 250 } 251 if (first) { 252 mode = ++cp; 253 first = 0; 254 goto again; 255 } 256 for (cp = mode; *cp; cp++) 257 if (isupper(*cp)) 258 *cp = tolower(*cp); 259 for (pf = formats; pf->f_mode; pf++) 260 if (strcmp(pf->f_mode, mode) == 0) 261 break; 262 if (pf->f_mode == 0) { 263 nak(EBADOP); 264 exit(1); 265 } 266 ecode = (*pf->f_validate)(&filename, tp->th_opcode); 267 if (logging) { 268 syslog(LOG_INFO, "%s: %s request for %s: %s", 269 verifyhost(&from), 270 tp->th_opcode == WRQ ? "write" : "read", 271 filename, errtomsg(ecode)); 272 } 273 if (ecode) { 274 /* 275 * Avoid storms of naks to a RRQ broadcast for a relative 276 * bootfile pathname from a diskless Sun. 277 */ 278 if (suppress_naks && *filename != '/' && ecode == ENOTFOUND) 279 exit(0); 280 nak(ecode); 281 exit(1); 282 } 283 if (tp->th_opcode == WRQ) 284 (*pf->f_recv)(pf); 285 else 286 (*pf->f_send)(pf); 287 exit(0); 288 } 289 290 291 FILE *file; 292 293 /* 294 * Validate file access. Since we 295 * have no uid or gid, for now require 296 * file to exist and be publicly 297 * readable/writable. 298 * If we were invoked with arguments 299 * from inetd then the file must also be 300 * in one of the given directory prefixes. 301 * Note also, full path name must be 302 * given as we have no login directory. 303 */ 304 int 305 validate_access(filep, mode) 306 char **filep; 307 int mode; 308 { 309 struct stat stbuf; 310 int fd; 311 struct dirlist *dirp; 312 static char pathname[MAXPATHLEN]; 313 char *filename = *filep; 314 315 /* 316 * Prevent tricksters from getting around the directory restrictions 317 */ 318 if (strstr(filename, "/../")) 319 return (EACCESS); 320 321 if (*filename == '/') { 322 /* 323 * Allow the request if it's in one of the approved locations. 324 * Special case: check the null prefix ("/") by looking 325 * for length = 1 and relying on the arg. processing that 326 * it's a /. 327 */ 328 for (dirp = dirs; dirp->name != NULL; dirp++) { 329 if (dirp->len == 1 || 330 (!strncmp(filename, dirp->name, dirp->len) && 331 filename[dirp->len] == '/')) 332 break; 333 } 334 /* If directory list is empty, allow access to any file */ 335 if (dirp->name == NULL && dirp != dirs) 336 return (EACCESS); 337 if (stat(filename, &stbuf) < 0) 338 return (errno == ENOENT ? ENOTFOUND : EACCESS); 339 if ((stbuf.st_mode & S_IFMT) != S_IFREG) 340 return (ENOTFOUND); 341 if (mode == RRQ) { 342 if ((stbuf.st_mode & S_IROTH) == 0) 343 return (EACCESS); 344 } else { 345 if ((stbuf.st_mode & S_IWOTH) == 0) 346 return (EACCESS); 347 } 348 } else { 349 int err; 350 351 /* 352 * Relative file name: search the approved locations for it. 353 * Don't allow write requests or ones that avoid directory 354 * restrictions. 355 */ 356 357 if (mode != RRQ || !strncmp(filename, "../", 3)) 358 return (EACCESS); 359 360 /* 361 * If the file exists in one of the directories and isn't 362 * readable, continue looking. However, change the error code 363 * to give an indication that the file exists. 364 */ 365 err = ENOTFOUND; 366 for (dirp = dirs; dirp->name != NULL; dirp++) { 367 sprintf(pathname, "%s/%s", dirp->name, filename); 368 if (stat(pathname, &stbuf) == 0 && 369 (stbuf.st_mode & S_IFMT) == S_IFREG) { 370 if ((stbuf.st_mode & S_IROTH) != 0) { 371 break; 372 } 373 err = EACCESS; 374 } 375 } 376 if (dirp->name == NULL) 377 return (err); 378 *filep = filename = pathname; 379 } 380 fd = open(filename, mode == RRQ ? 0 : 1); 381 if (fd < 0) 382 return (errno + 100); 383 file = fdopen(fd, (mode == RRQ)? "r":"w"); 384 if (file == NULL) { 385 return errno+100; 386 } 387 return (0); 388 } 389 390 int timeout; 391 jmp_buf timeoutbuf; 392 393 void 394 timer() 395 { 396 397 timeout += rexmtval; 398 if (timeout >= maxtimeout) 399 exit(1); 400 longjmp(timeoutbuf, 1); 401 } 402 403 /* 404 * Send the requested file. 405 */ 406 void 407 sendfile(pf) 408 struct formats *pf; 409 { 410 struct tftphdr *dp, *r_init(); 411 register struct tftphdr *ap; /* ack packet */ 412 register int size, n; 413 volatile int block; 414 415 signal(SIGALRM, timer); 416 dp = r_init(); 417 ap = (struct tftphdr *)ackbuf; 418 block = 1; 419 do { 420 size = readit(file, &dp, pf->f_convert); 421 if (size < 0) { 422 nak(errno + 100); 423 goto abort; 424 } 425 dp->th_opcode = htons((u_short)DATA); 426 dp->th_block = htons((u_short)block); 427 timeout = 0; 428 (void)setjmp(timeoutbuf); 429 430 send_data: 431 if (send(peer, dp, size + 4, 0) != size + 4) { 432 syslog(LOG_ERR, "tftpd: write: %m\n"); 433 goto abort; 434 } 435 read_ahead(file, pf->f_convert); 436 for ( ; ; ) { 437 alarm(rexmtval); /* read the ack */ 438 n = recv(peer, ackbuf, sizeof (ackbuf), 0); 439 alarm(0); 440 if (n < 0) { 441 syslog(LOG_ERR, "tftpd: read: %m\n"); 442 goto abort; 443 } 444 ap->th_opcode = ntohs((u_short)ap->th_opcode); 445 ap->th_block = ntohs((u_short)ap->th_block); 446 447 if (ap->th_opcode == ERROR) 448 goto abort; 449 450 if (ap->th_opcode == ACK) { 451 if (ap->th_block == block) 452 break; 453 /* Re-synchronize with the other side */ 454 (void) synchnet(peer); 455 if (ap->th_block == (block -1)) 456 goto send_data; 457 } 458 459 } 460 block++; 461 } while (size == SEGSIZE); 462 abort: 463 (void) fclose(file); 464 } 465 466 void 467 justquit() 468 { 469 exit(0); 470 } 471 472 473 /* 474 * Receive a file. 475 */ 476 void 477 recvfile(pf) 478 struct formats *pf; 479 { 480 struct tftphdr *dp, *w_init(); 481 register struct tftphdr *ap; /* ack buffer */ 482 register int n, size; 483 volatile int block; 484 485 signal(SIGALRM, timer); 486 dp = w_init(); 487 ap = (struct tftphdr *)ackbuf; 488 block = 0; 489 do { 490 timeout = 0; 491 ap->th_opcode = htons((u_short)ACK); 492 ap->th_block = htons((u_short)block); 493 block++; 494 (void) setjmp(timeoutbuf); 495 send_ack: 496 if (send(peer, ackbuf, 4, 0) != 4) { 497 syslog(LOG_ERR, "tftpd: write: %m\n"); 498 goto abort; 499 } 500 write_behind(file, pf->f_convert); 501 for ( ; ; ) { 502 alarm(rexmtval); 503 n = recv(peer, dp, PKTSIZE, 0); 504 alarm(0); 505 if (n < 0) { /* really? */ 506 syslog(LOG_ERR, "tftpd: read: %m\n"); 507 goto abort; 508 } 509 dp->th_opcode = ntohs((u_short)dp->th_opcode); 510 dp->th_block = ntohs((u_short)dp->th_block); 511 if (dp->th_opcode == ERROR) 512 goto abort; 513 if (dp->th_opcode == DATA) { 514 if (dp->th_block == block) { 515 break; /* normal */ 516 } 517 /* Re-synchronize with the other side */ 518 (void) synchnet(peer); 519 if (dp->th_block == (block-1)) 520 goto send_ack; /* rexmit */ 521 } 522 } 523 /* size = write(file, dp->th_data, n - 4); */ 524 size = writeit(file, &dp, n - 4, pf->f_convert); 525 if (size != (n-4)) { /* ahem */ 526 if (size < 0) nak(errno + 100); 527 else nak(ENOSPACE); 528 goto abort; 529 } 530 } while (size == SEGSIZE); 531 write_behind(file, pf->f_convert); 532 (void) fclose(file); /* close data file */ 533 534 ap->th_opcode = htons((u_short)ACK); /* send the "final" ack */ 535 ap->th_block = htons((u_short)(block)); 536 (void) send(peer, ackbuf, 4, 0); 537 538 signal(SIGALRM, justquit); /* just quit on timeout */ 539 alarm(rexmtval); 540 n = recv(peer, buf, sizeof (buf), 0); /* normally times out and quits */ 541 alarm(0); 542 if (n >= 4 && /* if read some data */ 543 dp->th_opcode == DATA && /* and got a data block */ 544 block == dp->th_block) { /* then my last ack was lost */ 545 (void) send(peer, ackbuf, 4, 0); /* resend final ack */ 546 } 547 abort: 548 return; 549 } 550 551 struct errmsg { 552 int e_code; 553 char *e_msg; 554 } errmsgs[] = { 555 { EUNDEF, "Undefined error code" }, 556 { ENOTFOUND, "File not found" }, 557 { EACCESS, "Access violation" }, 558 { ENOSPACE, "Disk full or allocation exceeded" }, 559 { EBADOP, "Illegal TFTP operation" }, 560 { EBADID, "Unknown transfer ID" }, 561 { EEXISTS, "File already exists" }, 562 { ENOUSER, "No such user" }, 563 { -1, 0 } 564 }; 565 566 static char * 567 errtomsg(error) 568 int error; 569 { 570 static char buf[20]; 571 register struct errmsg *pe; 572 if (error == 0) 573 return "success"; 574 for (pe = errmsgs; pe->e_code >= 0; pe++) 575 if (pe->e_code == error) 576 return pe->e_msg; 577 sprintf(buf, "error %d", error); 578 return buf; 579 } 580 581 /* 582 * Send a nak packet (error message). 583 * Error code passed in is one of the 584 * standard TFTP codes, or a UNIX errno 585 * offset by 100. 586 */ 587 static void 588 nak(error) 589 int error; 590 { 591 register struct tftphdr *tp; 592 int length; 593 register struct errmsg *pe; 594 595 tp = (struct tftphdr *)buf; 596 tp->th_opcode = htons((u_short)ERROR); 597 tp->th_code = htons((u_short)error); 598 for (pe = errmsgs; pe->e_code >= 0; pe++) 599 if (pe->e_code == error) 600 break; 601 if (pe->e_code < 0) { 602 pe->e_msg = strerror(error - 100); 603 tp->th_code = EUNDEF; /* set 'undef' errorcode */ 604 } 605 strcpy(tp->th_msg, pe->e_msg); 606 length = strlen(pe->e_msg); 607 tp->th_msg[length] = '\0'; 608 length += 5; 609 if (send(peer, buf, length, 0) != length) 610 syslog(LOG_ERR, "nak: %m\n"); 611 } 612 613 static char * 614 verifyhost(fromp) 615 struct sockaddr_in *fromp; 616 { 617 struct hostent *hp; 618 619 hp = gethostbyaddr((char *)&fromp->sin_addr, sizeof (fromp->sin_addr), 620 fromp->sin_family); 621 if (hp) 622 return hp->h_name; 623 else 624 return inet_ntoa(fromp->sin_addr); 625 } 626