tftpd.c revision 6750
1/* 2 * Copyright (c) 1983, 1993 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 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34#ifndef lint 35static char copyright[] = 36"@(#) Copyright (c) 1983, 1993\n\ 37 The Regents of the University of California. All rights reserved.\n"; 38#endif /* not lint */ 39 40#ifndef lint 41static char sccsid[] = "@(#)tftpd.c 8.1 (Berkeley) 6/4/93"; 42#endif /* not lint */ 43 44/* 45 * Trivial file transfer protocol server. 46 * 47 * This version includes many modifications by Jim Guyton 48 * <guyton@rand-unix>. 49 */ 50 51#include <sys/param.h> 52#include <sys/ioctl.h> 53#include <sys/stat.h> 54#include <sys/socket.h> 55 56#include <netinet/in.h> 57#include <arpa/tftp.h> 58#include <arpa/inet.h> 59 60#include <ctype.h> 61#include <errno.h> 62#include <fcntl.h> 63#include <netdb.h> 64#include <setjmp.h> 65#include <signal.h> 66#include <stdio.h> 67#include <stdlib.h> 68#include <string.h> 69#include <syslog.h> 70#include <unistd.h> 71 72#include "tftpsubs.h" 73 74#define TIMEOUT 5 75 76int peer; 77int rexmtval = TIMEOUT; 78int maxtimeout = 5*TIMEOUT; 79 80#define PKTSIZE SEGSIZE+4 81char buf[PKTSIZE]; 82char ackbuf[PKTSIZE]; 83struct sockaddr_in from; 84int fromlen; 85 86void tftp __P((struct tftphdr *, int)); 87 88/* 89 * Null-terminated directory prefix list for absolute pathname requests and 90 * search list for relative pathname requests. 91 * 92 * MAXDIRS should be at least as large as the number of arguments that 93 * inetd allows (currently 20). 94 */ 95#define MAXDIRS 20 96static struct dirlist { 97 char *name; 98 int len; 99} dirs[MAXDIRS+1]; 100static int suppress_naks; 101static int logging; 102 103static char *errtomsg __P((int)); 104static void nak __P((int)); 105static char *verifyhost __P((struct sockaddr_in *)); 106 107int 108main(argc, argv) 109 int argc; 110 char *argv[]; 111{ 112 register struct tftphdr *tp; 113 register int n; 114 int ch, on; 115 struct sockaddr_in sin; 116 117 openlog("tftpd", LOG_PID, LOG_FTP); 118 while ((ch = getopt(argc, argv, "ln")) != EOF) { 119 switch (ch) { 120 case 'l': 121 logging = 1; 122 break; 123 case 'n': 124 suppress_naks = 1; 125 break; 126 default: 127 syslog(LOG_WARNING, "ignoring unknown option -%c", ch); 128 } 129 } 130 if (optind < argc) { 131 struct dirlist *dirp; 132 133 /* Get list of directory prefixes. Skip relative pathnames. */ 134 for (dirp = dirs; optind < argc && dirp < &dirs[MAXDIRS]; 135 optind++) { 136 if (argv[optind][0] == '/') { 137 dirp->name = argv[optind]; 138 dirp->len = strlen(dirp->name); 139 dirp++; 140 } 141 } 142 } 143 144 on = 1; 145 if (ioctl(0, FIONBIO, &on) < 0) { 146 syslog(LOG_ERR, "ioctl(FIONBIO): %m\n"); 147 exit(1); 148 } 149 fromlen = sizeof (from); 150 n = recvfrom(0, buf, sizeof (buf), 0, 151 (struct sockaddr *)&from, &fromlen); 152 if (n < 0) { 153 syslog(LOG_ERR, "recvfrom: %m\n"); 154 exit(1); 155 } 156 /* 157 * Now that we have read the message out of the UDP 158 * socket, we fork and exit. Thus, inetd will go back 159 * to listening to the tftp port, and the next request 160 * to come in will start up a new instance of tftpd. 161 * 162 * We do this so that inetd can run tftpd in "wait" mode. 163 * The problem with tftpd running in "nowait" mode is that 164 * inetd may get one or more successful "selects" on the 165 * tftp port before we do our receive, so more than one 166 * instance of tftpd may be started up. Worse, if tftpd 167 * break before doing the above "recvfrom", inetd would 168 * spawn endless instances, clogging the system. 169 */ 170 { 171 int pid; 172 int i, j; 173 174 for (i = 1; i < 20; i++) { 175 pid = fork(); 176 if (pid < 0) { 177 sleep(i); 178 /* 179 * flush out to most recently sent request. 180 * 181 * This may drop some request, but those 182 * will be resent by the clients when 183 * they timeout. The positive effect of 184 * this flush is to (try to) prevent more 185 * than one tftpd being started up to service 186 * a single request from a single client. 187 */ 188 j = sizeof from; 189 i = recvfrom(0, buf, sizeof (buf), 0, 190 (struct sockaddr *)&from, &j); 191 if (i > 0) { 192 n = i; 193 fromlen = j; 194 } 195 } else { 196 break; 197 } 198 } 199 if (pid < 0) { 200 syslog(LOG_ERR, "fork: %m\n"); 201 exit(1); 202 } else if (pid != 0) { 203 exit(0); 204 } 205 } 206 from.sin_family = AF_INET; 207 alarm(0); 208 close(0); 209 close(1); 210 peer = socket(AF_INET, SOCK_DGRAM, 0); 211 if (peer < 0) { 212 syslog(LOG_ERR, "socket: %m\n"); 213 exit(1); 214 } 215 memset(&sin, 0, sizeof(sin)); 216 sin.sin_family = AF_INET; 217 if (bind(peer, (struct sockaddr *)&sin, sizeof (sin)) < 0) { 218 syslog(LOG_ERR, "bind: %m\n"); 219 exit(1); 220 } 221 if (connect(peer, (struct sockaddr *)&from, sizeof(from)) < 0) { 222 syslog(LOG_ERR, "connect: %m\n"); 223 exit(1); 224 } 225 tp = (struct tftphdr *)buf; 226 tp->th_opcode = ntohs(tp->th_opcode); 227 if (tp->th_opcode == RRQ || tp->th_opcode == WRQ) 228 tftp(tp, n); 229 exit(1); 230} 231 232struct formats; 233int validate_access __P((char **, int)); 234void sendfile __P((struct formats *)); 235void recvfile __P((struct formats *)); 236 237struct formats { 238 char *f_mode; 239 int (*f_validate) __P((char **, int)); 240 void (*f_send) __P((struct formats *)); 241 void (*f_recv) __P((struct formats *)); 242 int f_convert; 243} formats[] = { 244 { "netascii", validate_access, sendfile, recvfile, 1 }, 245 { "octet", validate_access, sendfile, recvfile, 0 }, 246#ifdef notdef 247 { "mail", validate_user, sendmail, recvmail, 1 }, 248#endif 249 { 0 } 250}; 251 252/* 253 * Handle initial connection protocol. 254 */ 255void 256tftp(tp, size) 257 struct tftphdr *tp; 258 int size; 259{ 260 register char *cp; 261 int first = 1, ecode; 262 register struct formats *pf; 263 char *filename, *mode; 264 265 filename = cp = tp->th_stuff; 266again: 267 while (cp < buf + size) { 268 if (*cp == '\0') 269 break; 270 cp++; 271 } 272 if (*cp != '\0') { 273 nak(EBADOP); 274 exit(1); 275 } 276 if (first) { 277 mode = ++cp; 278 first = 0; 279 goto again; 280 } 281 for (cp = mode; *cp; cp++) 282 if (isupper(*cp)) 283 *cp = tolower(*cp); 284 for (pf = formats; pf->f_mode; pf++) 285 if (strcmp(pf->f_mode, mode) == 0) 286 break; 287 if (pf->f_mode == 0) { 288 nak(EBADOP); 289 exit(1); 290 } 291 ecode = (*pf->f_validate)(&filename, tp->th_opcode); 292 if (logging) { 293 syslog(LOG_INFO, "%s: %s request for %s: %s", 294 verifyhost(&from), 295 tp->th_opcode == WRQ ? "write" : "read", 296 filename, errtomsg(ecode)); 297 } 298 if (ecode) { 299 /* 300 * Avoid storms of naks to a RRQ broadcast for a relative 301 * bootfile pathname from a diskless Sun. 302 */ 303 if (suppress_naks && *filename != '/' && ecode == ENOTFOUND) 304 exit(0); 305 nak(ecode); 306 exit(1); 307 } 308 if (tp->th_opcode == WRQ) 309 (*pf->f_recv)(pf); 310 else 311 (*pf->f_send)(pf); 312 exit(0); 313} 314 315 316FILE *file; 317 318/* 319 * Validate file access. Since we 320 * have no uid or gid, for now require 321 * file to exist and be publicly 322 * readable/writable. 323 * If we were invoked with arguments 324 * from inetd then the file must also be 325 * in one of the given directory prefixes. 326 * Note also, full path name must be 327 * given as we have no login directory. 328 */ 329int 330validate_access(filep, mode) 331 char **filep; 332 int mode; 333{ 334 struct stat stbuf; 335 int fd; 336 struct dirlist *dirp; 337 static char pathname[MAXPATHLEN]; 338 char *filename = *filep; 339 340 /* 341 * Prevent tricksters from getting around the directory restrictions 342 */ 343 if (strstr(filename, "/../")) 344 return (EACCESS); 345 346 if (*filename == '/') { 347 /* 348 * Allow the request if it's in one of the approved locations. 349 * Special case: check the null prefix ("/") by looking 350 * for length = 1 and relying on the arg. processing that 351 * it's a /. 352 */ 353 for (dirp = dirs; dirp->name != NULL; dirp++) { 354 if (dirp->len == 1 || 355 (!strncmp(filename, dirp->name, dirp->len) && 356 filename[dirp->len] == '/')) 357 break; 358 } 359 /* If directory list is empty, allow access to any file */ 360 if (dirp->name == NULL && dirp != dirs) 361 return (EACCESS); 362 if (stat(filename, &stbuf) < 0) 363 return (errno == ENOENT ? ENOTFOUND : EACCESS); 364 if ((stbuf.st_mode & S_IFMT) != S_IFREG) 365 return (ENOTFOUND); 366 if (mode == RRQ) { 367 if ((stbuf.st_mode & S_IROTH) == 0) 368 return (EACCESS); 369 } else { 370 if ((stbuf.st_mode & S_IWOTH) == 0) 371 return (EACCESS); 372 } 373 } else { 374 int err; 375 376 /* 377 * Relative file name: search the approved locations for it. 378 * Don't allow write requests that avoid directory 379 * restrictions. 380 */ 381 382 if (!strncmp(filename, "../", 3)) 383 return (EACCESS); 384 385 /* 386 * If the file exists in one of the directories and isn't 387 * readable, continue looking. However, change the error code 388 * to give an indication that the file exists. 389 */ 390 err = ENOTFOUND; 391 for (dirp = dirs; dirp->name != NULL; dirp++) { 392 sprintf(pathname, "%s/%s", dirp->name, filename); 393 if (stat(pathname, &stbuf) == 0 && 394 (stbuf.st_mode & S_IFMT) == S_IFREG) { 395 if ((stbuf.st_mode & S_IROTH) != 0) { 396 break; 397 } 398 err = EACCESS; 399 } 400 } 401 if (dirp->name == NULL) 402 return (err); 403 *filep = filename = pathname; 404 } 405 fd = open(filename, mode == RRQ ? 0 : 1); 406 if (fd < 0) 407 return (errno + 100); 408 file = fdopen(fd, (mode == RRQ)? "r":"w"); 409 if (file == NULL) { 410 return errno+100; 411 } 412 return (0); 413} 414 415int timeout; 416jmp_buf timeoutbuf; 417 418void 419timer() 420{ 421 422 timeout += rexmtval; 423 if (timeout >= maxtimeout) 424 exit(1); 425 longjmp(timeoutbuf, 1); 426} 427 428/* 429 * Send the requested file. 430 */ 431void 432sendfile(pf) 433 struct formats *pf; 434{ 435 struct tftphdr *dp, *r_init(); 436 register struct tftphdr *ap; /* ack packet */ 437 register int size, n; 438 volatile int block; 439 440 signal(SIGALRM, timer); 441 dp = r_init(); 442 ap = (struct tftphdr *)ackbuf; 443 block = 1; 444 do { 445 size = readit(file, &dp, pf->f_convert); 446 if (size < 0) { 447 nak(errno + 100); 448 goto abort; 449 } 450 dp->th_opcode = htons((u_short)DATA); 451 dp->th_block = htons((u_short)block); 452 timeout = 0; 453 (void)setjmp(timeoutbuf); 454 455send_data: 456 if (send(peer, dp, size + 4, 0) != size + 4) { 457 syslog(LOG_ERR, "tftpd: write: %m\n"); 458 goto abort; 459 } 460 read_ahead(file, pf->f_convert); 461 for ( ; ; ) { 462 alarm(rexmtval); /* read the ack */ 463 n = recv(peer, ackbuf, sizeof (ackbuf), 0); 464 alarm(0); 465 if (n < 0) { 466 syslog(LOG_ERR, "tftpd: read: %m\n"); 467 goto abort; 468 } 469 ap->th_opcode = ntohs((u_short)ap->th_opcode); 470 ap->th_block = ntohs((u_short)ap->th_block); 471 472 if (ap->th_opcode == ERROR) 473 goto abort; 474 475 if (ap->th_opcode == ACK) { 476 if (ap->th_block == block) 477 break; 478 /* Re-synchronize with the other side */ 479 (void) synchnet(peer); 480 if (ap->th_block == (block -1)) 481 goto send_data; 482 } 483 484 } 485 block++; 486 } while (size == SEGSIZE); 487abort: 488 (void) fclose(file); 489} 490 491void 492justquit() 493{ 494 exit(0); 495} 496 497 498/* 499 * Receive a file. 500 */ 501void 502recvfile(pf) 503 struct formats *pf; 504{ 505 struct tftphdr *dp, *w_init(); 506 register struct tftphdr *ap; /* ack buffer */ 507 register int n, size; 508 volatile int block; 509 510 signal(SIGALRM, timer); 511 dp = w_init(); 512 ap = (struct tftphdr *)ackbuf; 513 block = 0; 514 do { 515 timeout = 0; 516 ap->th_opcode = htons((u_short)ACK); 517 ap->th_block = htons((u_short)block); 518 block++; 519 (void) setjmp(timeoutbuf); 520send_ack: 521 if (send(peer, ackbuf, 4, 0) != 4) { 522 syslog(LOG_ERR, "tftpd: write: %m\n"); 523 goto abort; 524 } 525 write_behind(file, pf->f_convert); 526 for ( ; ; ) { 527 alarm(rexmtval); 528 n = recv(peer, dp, PKTSIZE, 0); 529 alarm(0); 530 if (n < 0) { /* really? */ 531 syslog(LOG_ERR, "tftpd: read: %m\n"); 532 goto abort; 533 } 534 dp->th_opcode = ntohs((u_short)dp->th_opcode); 535 dp->th_block = ntohs((u_short)dp->th_block); 536 if (dp->th_opcode == ERROR) 537 goto abort; 538 if (dp->th_opcode == DATA) { 539 if (dp->th_block == block) { 540 break; /* normal */ 541 } 542 /* Re-synchronize with the other side */ 543 (void) synchnet(peer); 544 if (dp->th_block == (block-1)) 545 goto send_ack; /* rexmit */ 546 } 547 } 548 /* size = write(file, dp->th_data, n - 4); */ 549 size = writeit(file, &dp, n - 4, pf->f_convert); 550 if (size != (n-4)) { /* ahem */ 551 if (size < 0) nak(errno + 100); 552 else nak(ENOSPACE); 553 goto abort; 554 } 555 } while (size == SEGSIZE); 556 write_behind(file, pf->f_convert); 557 (void) fclose(file); /* close data file */ 558 559 ap->th_opcode = htons((u_short)ACK); /* send the "final" ack */ 560 ap->th_block = htons((u_short)(block)); 561 (void) send(peer, ackbuf, 4, 0); 562 563 signal(SIGALRM, justquit); /* just quit on timeout */ 564 alarm(rexmtval); 565 n = recv(peer, buf, sizeof (buf), 0); /* normally times out and quits */ 566 alarm(0); 567 if (n >= 4 && /* if read some data */ 568 dp->th_opcode == DATA && /* and got a data block */ 569 block == dp->th_block) { /* then my last ack was lost */ 570 (void) send(peer, ackbuf, 4, 0); /* resend final ack */ 571 } 572abort: 573 return; 574} 575 576struct errmsg { 577 int e_code; 578 char *e_msg; 579} errmsgs[] = { 580 { EUNDEF, "Undefined error code" }, 581 { ENOTFOUND, "File not found" }, 582 { EACCESS, "Access violation" }, 583 { ENOSPACE, "Disk full or allocation exceeded" }, 584 { EBADOP, "Illegal TFTP operation" }, 585 { EBADID, "Unknown transfer ID" }, 586 { EEXISTS, "File already exists" }, 587 { ENOUSER, "No such user" }, 588 { -1, 0 } 589}; 590 591static char * 592errtomsg(error) 593 int error; 594{ 595 static char buf[20]; 596 register struct errmsg *pe; 597 if (error == 0) 598 return "success"; 599 for (pe = errmsgs; pe->e_code >= 0; pe++) 600 if (pe->e_code == error) 601 return pe->e_msg; 602 sprintf(buf, "error %d", error); 603 return buf; 604} 605 606/* 607 * Send a nak packet (error message). 608 * Error code passed in is one of the 609 * standard TFTP codes, or a UNIX errno 610 * offset by 100. 611 */ 612static void 613nak(error) 614 int error; 615{ 616 register struct tftphdr *tp; 617 int length; 618 register struct errmsg *pe; 619 620 tp = (struct tftphdr *)buf; 621 tp->th_opcode = htons((u_short)ERROR); 622 tp->th_code = htons((u_short)error); 623 for (pe = errmsgs; pe->e_code >= 0; pe++) 624 if (pe->e_code == error) 625 break; 626 if (pe->e_code < 0) { 627 pe->e_msg = strerror(error - 100); 628 tp->th_code = EUNDEF; /* set 'undef' errorcode */ 629 } 630 strcpy(tp->th_msg, pe->e_msg); 631 length = strlen(pe->e_msg); 632 tp->th_msg[length] = '\0'; 633 length += 5; 634 if (send(peer, buf, length, 0) != length) 635 syslog(LOG_ERR, "nak: %m\n"); 636} 637 638static char * 639verifyhost(fromp) 640 struct sockaddr_in *fromp; 641{ 642 struct hostent *hp; 643 644 hp = gethostbyaddr((char *)&fromp->sin_addr, sizeof (fromp->sin_addr), 645 fromp->sin_family); 646 if (hp) 647 return hp->h_name; 648 else 649 return inet_ntoa(fromp->sin_addr); 650} 651