1 /* 2 * Copyright (c) 1983 Regents of the University of California. 3 * 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 35 char copyright[] = 36 "@(#) Copyright (c) 1983 Regents of the University of California.\n\ 37 All rights reserved.\n"; 38 #endif /* not lint */ 39 40 #ifndef lint 41 /*static char sccsid[] = "from: @(#)tftpd.c 5.13 (Berkeley) 2/26/91";*/ 42 static char rcsid[] = "$Id: tftpd.c,v 1.8 1997/04/22 10:33:07 mrg Exp $"; 43 #endif /* not lint */ 44 45 /* 46 * Trivial file transfer protocol server. 47 * 48 * This version includes many modifications by Jim Guyton <guyton@rand-unix> 49 */ 50 51 #include <sys/types.h> 52 #include <sys/ioctl.h> 53 #include <sys/stat.h> 54 #include <signal.h> 55 #include <fcntl.h> 56 57 #include <sys/socket.h> 58 #include <netinet/in.h> 59 #include <arpa/tftp.h> 60 #include <netdb.h> 61 62 #include <setjmp.h> 63 #include <syslog.h> 64 #include <stdio.h> 65 #include <errno.h> 66 #include <ctype.h> 67 #include <string.h> 68 #include <stdlib.h> 69 70 /* XXX svr4 defines UID_NOBODY and GID_NOBODY constants in <sys/param.h> */ 71 #define UID_NOBODY 32767 72 #define GID_NOBODY 32766 73 74 #define TIMEOUT 5 75 76 extern int errno; 77 extern char *__progname; 78 struct sockaddr_in s_in = { AF_INET }; 79 int peer; 80 int rexmtval = TIMEOUT; 81 int maxtimeout = 5*TIMEOUT; 82 83 #define PKTSIZE SEGSIZE+4 84 char buf[PKTSIZE]; 85 char ackbuf[PKTSIZE]; 86 struct sockaddr_in from; 87 int fromlen; 88 89 #define MAXARG 4 90 char *dirs[MAXARG+1]; 91 92 int secure = 0; 93 94 static void 95 usage() 96 { 97 syslog(LOG_ERR, "Usage: %s [-s] [directory ...]\n", __progname); 98 exit(1); 99 } 100 101 main(argc, argv) 102 int argc; 103 char **argv; 104 { 105 register struct tftphdr *tp; 106 register int n = 0; 107 int on = 1; 108 int fd = 0; 109 int c; 110 111 openlog("tftpd", LOG_PID, LOG_DAEMON); 112 113 while ((c = getopt(argc, argv, "s")) != -1) 114 switch (c) { 115 case 's': 116 secure = 1; 117 break; 118 119 default: 120 usage(); 121 break; 122 } 123 124 for (; optind != argc; optind++) { 125 if (!secure) { 126 if (n >= MAXARG) { 127 syslog(LOG_ERR, "too many directories\n"); 128 exit(1); 129 } else 130 dirs[n++] = argv[optind]; 131 } 132 if (chdir(argv[optind])) { 133 syslog(LOG_ERR, "%s: %m\n", argv[optind]); 134 exit(1); 135 } 136 } 137 138 if (secure && chroot(".")) { 139 syslog(LOG_ERR, "chroot: %m\n"); 140 exit(1); 141 } 142 143 if (setgid(GID_NOBODY)) { 144 syslog(LOG_ERR, "setgid: %m"); 145 exit(1); 146 } 147 148 if (setgroups(0, NULL)) { 149 syslog(LOG_ERR, "setgroups: %m"); 150 exit(1); 151 } 152 153 if (setuid(UID_NOBODY)) { 154 syslog(LOG_ERR, "setuid: %m"); 155 exit(1); 156 } 157 158 if (ioctl(fd, FIONBIO, &on) < 0) { 159 syslog(LOG_ERR, "ioctl(FIONBIO): %m\n"); 160 exit(1); 161 } 162 fromlen = sizeof (from); 163 n = recvfrom(fd, buf, sizeof (buf), 0, 164 (struct sockaddr *)&from, &fromlen); 165 if (n < 0) { 166 syslog(LOG_ERR, "recvfrom: %m\n"); 167 exit(1); 168 } 169 /* 170 * Now that we have read the message out of the UDP 171 * socket, we fork and exit. Thus, inetd will go back 172 * to listening to the tftp port, and the next request 173 * to come in will start up a new instance of tftpd. 174 * 175 * We do this so that inetd can run tftpd in "wait" mode. 176 * The problem with tftpd running in "nowait" mode is that 177 * inetd may get one or more successful "selects" on the 178 * tftp port before we do our receive, so more than one 179 * instance of tftpd may be started up. Worse, if tftpd 180 * break before doing the above "recvfrom", inetd would 181 * spawn endless instances, clogging the system. 182 */ 183 { 184 int pid; 185 int i, j; 186 187 for (i = 1; i < 20; i++) { 188 pid = fork(); 189 if (pid < 0) { 190 sleep(i); 191 /* 192 * flush out to most recently sent request. 193 * 194 * This may drop some request, but those 195 * will be resent by the clients when 196 * they timeout. The positive effect of 197 * this flush is to (try to) prevent more 198 * than one tftpd being started up to service 199 * a single request from a single client. 200 */ 201 j = sizeof from; 202 i = recvfrom(fd, buf, sizeof (buf), 0, 203 (struct sockaddr *)&from, &j); 204 if (i > 0) { 205 n = i; 206 fromlen = j; 207 } 208 } else { 209 break; 210 } 211 } 212 if (pid < 0) { 213 syslog(LOG_ERR, "fork: %m\n"); 214 exit(1); 215 } else if (pid != 0) { 216 exit(0); 217 } 218 } 219 from.sin_len = sizeof(struct sockaddr_in); 220 from.sin_family = AF_INET; 221 alarm(0); 222 close(fd); 223 close(1); 224 peer = socket(AF_INET, SOCK_DGRAM, 0); 225 if (peer < 0) { 226 syslog(LOG_ERR, "socket: %m\n"); 227 exit(1); 228 } 229 if (bind(peer, (struct sockaddr *)&s_in, sizeof (s_in)) < 0) { 230 syslog(LOG_ERR, "bind: %m\n"); 231 exit(1); 232 } 233 if (connect(peer, (struct sockaddr *)&from, sizeof(from)) < 0) { 234 syslog(LOG_ERR, "connect: %m\n"); 235 exit(1); 236 } 237 tp = (struct tftphdr *)buf; 238 tp->th_opcode = ntohs(tp->th_opcode); 239 if (tp->th_opcode == RRQ || tp->th_opcode == WRQ) 240 tftp(tp, n); 241 exit(1); 242 } 243 244 int validate_access(); 245 int sendfile(), recvfile(); 246 247 struct formats { 248 char *f_mode; 249 int (*f_validate)(); 250 int (*f_send)(); 251 int (*f_recv)(); 252 int f_convert; 253 } formats[] = { 254 { "netascii", validate_access, sendfile, recvfile, 1 }, 255 { "octet", validate_access, sendfile, recvfile, 0 }, 256 #ifdef notdef 257 { "mail", validate_user, sendmail, recvmail, 1 }, 258 #endif 259 { 0 } 260 }; 261 262 /* 263 * Handle initial connection protocol. 264 */ 265 tftp(tp, size) 266 struct tftphdr *tp; 267 int size; 268 { 269 register char *cp; 270 int first = 1, ecode; 271 register struct formats *pf; 272 char *filename, *mode; 273 274 filename = cp = tp->th_stuff; 275 again: 276 while (cp < buf + size) { 277 if (*cp == '\0') 278 break; 279 cp++; 280 } 281 if (*cp != '\0') { 282 nak(EBADOP); 283 exit(1); 284 } 285 if (first) { 286 mode = ++cp; 287 first = 0; 288 goto again; 289 } 290 for (cp = mode; *cp; cp++) 291 if (isupper(*cp)) 292 *cp = tolower(*cp); 293 for (pf = formats; pf->f_mode; pf++) 294 if (strcmp(pf->f_mode, mode) == 0) 295 break; 296 if (pf->f_mode == 0) { 297 nak(EBADOP); 298 exit(1); 299 } 300 ecode = (*pf->f_validate)(filename, tp->th_opcode); 301 if (ecode) { 302 nak(ecode); 303 exit(1); 304 } 305 if (tp->th_opcode == WRQ) 306 (*pf->f_recv)(pf); 307 else 308 (*pf->f_send)(pf); 309 exit(0); 310 } 311 312 313 FILE *file; 314 315 /* 316 * Validate file access. Since we 317 * have no uid or gid, for now require 318 * file to exist and be publicly 319 * readable/writable. 320 * If we were invoked with arguments 321 * from inetd then the file must also be 322 * in one of the given directory prefixes. 323 * Note also, full path name must be 324 * given as we have no login directory. 325 */ 326 validate_access(filename, mode) 327 char *filename; 328 int mode; 329 { 330 struct stat stbuf; 331 int fd; 332 char *cp, **dirp; 333 334 if (!secure) { 335 if (*filename != '/') 336 return (EACCESS); 337 /* 338 * prevent tricksters from getting around the directory 339 * restrictions 340 */ 341 for (cp = filename + 1; *cp; cp++) 342 if(*cp == '.' && strncmp(cp-1, "/../", 4) == 0) 343 return(EACCESS); 344 for (dirp = dirs; *dirp; dirp++) 345 if (strncmp(filename, *dirp, strlen(*dirp)) == 0) 346 break; 347 if (*dirp==0 && dirp!=dirs) 348 return (EACCESS); 349 } 350 if (stat(filename, &stbuf) < 0) 351 return (errno == ENOENT ? ENOTFOUND : EACCESS); 352 if (mode == RRQ) { 353 if ((stbuf.st_mode&(S_IREAD >> 6)) == 0) 354 return (EACCESS); 355 } else { 356 if ((stbuf.st_mode&(S_IWRITE >> 6)) == 0) 357 return (EACCESS); 358 } 359 fd = open(filename, mode == RRQ ? 0 : 1); 360 if (fd < 0) 361 return (errno + 100); 362 file = fdopen(fd, (mode == RRQ)? "r":"w"); 363 if (file == NULL) { 364 return errno+100; 365 } 366 return (0); 367 } 368 369 int timeout; 370 jmp_buf timeoutbuf; 371 372 void 373 timer() 374 { 375 376 timeout += rexmtval; 377 if (timeout >= maxtimeout) 378 exit(1); 379 longjmp(timeoutbuf, 1); 380 } 381 382 /* 383 * Send the requested file. 384 */ 385 sendfile(pf) 386 struct formats *pf; 387 { 388 struct tftphdr *dp, *r_init(); 389 register struct tftphdr *ap; /* ack packet */ 390 register int block = 1, size, n; 391 392 signal(SIGALRM, timer); 393 dp = r_init(); 394 ap = (struct tftphdr *)ackbuf; 395 do { 396 size = readit(file, &dp, pf->f_convert); 397 if (size < 0) { 398 nak(errno + 100); 399 goto abort; 400 } 401 dp->th_opcode = htons((u_short)DATA); 402 dp->th_block = htons((u_short)block); 403 timeout = 0; 404 (void) setjmp(timeoutbuf); 405 406 send_data: 407 if (send(peer, dp, size + 4, 0) != size + 4) { 408 syslog(LOG_ERR, "tftpd: write: %m\n"); 409 goto abort; 410 } 411 read_ahead(file, pf->f_convert); 412 for ( ; ; ) { 413 alarm(rexmtval); /* read the ack */ 414 n = recv(peer, ackbuf, sizeof (ackbuf), 0); 415 alarm(0); 416 if (n < 0) { 417 syslog(LOG_ERR, "tftpd: read: %m\n"); 418 goto abort; 419 } 420 ap->th_opcode = ntohs((u_short)ap->th_opcode); 421 ap->th_block = ntohs((u_short)ap->th_block); 422 423 if (ap->th_opcode == ERROR) 424 goto abort; 425 426 if (ap->th_opcode == ACK) { 427 if (ap->th_block == block) { 428 break; 429 } 430 /* Re-synchronize with the other side */ 431 (void) synchnet(peer); 432 if (ap->th_block == (block -1)) { 433 goto send_data; 434 } 435 } 436 437 } 438 block++; 439 } while (size == SEGSIZE); 440 abort: 441 (void) fclose(file); 442 } 443 444 void 445 justquit() 446 { 447 exit(0); 448 } 449 450 451 /* 452 * Receive a file. 453 */ 454 recvfile(pf) 455 struct formats *pf; 456 { 457 struct tftphdr *dp, *w_init(); 458 register struct tftphdr *ap; /* ack buffer */ 459 register int block = 0, n, size; 460 461 signal(SIGALRM, timer); 462 dp = w_init(); 463 ap = (struct tftphdr *)ackbuf; 464 do { 465 timeout = 0; 466 ap->th_opcode = htons((u_short)ACK); 467 ap->th_block = htons((u_short)block); 468 block++; 469 (void) setjmp(timeoutbuf); 470 send_ack: 471 if (send(peer, ackbuf, 4, 0) != 4) { 472 syslog(LOG_ERR, "tftpd: write: %m\n"); 473 goto abort; 474 } 475 write_behind(file, pf->f_convert); 476 for ( ; ; ) { 477 alarm(rexmtval); 478 n = recv(peer, dp, PKTSIZE, 0); 479 alarm(0); 480 if (n < 0) { /* really? */ 481 syslog(LOG_ERR, "tftpd: read: %m\n"); 482 goto abort; 483 } 484 dp->th_opcode = ntohs((u_short)dp->th_opcode); 485 dp->th_block = ntohs((u_short)dp->th_block); 486 if (dp->th_opcode == ERROR) 487 goto abort; 488 if (dp->th_opcode == DATA) { 489 if (dp->th_block == block) { 490 break; /* normal */ 491 } 492 /* Re-synchronize with the other side */ 493 (void) synchnet(peer); 494 if (dp->th_block == (block-1)) 495 goto send_ack; /* rexmit */ 496 } 497 } 498 /* size = write(file, dp->th_data, n - 4); */ 499 size = writeit(file, &dp, n - 4, pf->f_convert); 500 if (size != (n-4)) { /* ahem */ 501 if (size < 0) nak(errno + 100); 502 else nak(ENOSPACE); 503 goto abort; 504 } 505 } while (size == SEGSIZE); 506 write_behind(file, pf->f_convert); 507 (void) fclose(file); /* close data file */ 508 509 ap->th_opcode = htons((u_short)ACK); /* send the "final" ack */ 510 ap->th_block = htons((u_short)(block)); 511 (void) send(peer, ackbuf, 4, 0); 512 513 signal(SIGALRM, justquit); /* just quit on timeout */ 514 alarm(rexmtval); 515 n = recv(peer, buf, sizeof (buf), 0); /* normally times out and quits */ 516 alarm(0); 517 if (n >= 4 && /* if read some data */ 518 dp->th_opcode == DATA && /* and got a data block */ 519 block == dp->th_block) { /* then my last ack was lost */ 520 (void) send(peer, ackbuf, 4, 0); /* resend final ack */ 521 } 522 abort: 523 return; 524 } 525 526 struct errmsg { 527 int e_code; 528 char *e_msg; 529 } errmsgs[] = { 530 { EUNDEF, "Undefined error code" }, 531 { ENOTFOUND, "File not found" }, 532 { EACCESS, "Access violation" }, 533 { ENOSPACE, "Disk full or allocation exceeded" }, 534 { EBADOP, "Illegal TFTP operation" }, 535 { EBADID, "Unknown transfer ID" }, 536 { EEXISTS, "File already exists" }, 537 { ENOUSER, "No such user" }, 538 { -1, 0 } 539 }; 540 541 /* 542 * Send a nak packet (error message). 543 * Error code passed in is one of the 544 * standard TFTP codes, or a UNIX errno 545 * offset by 100. 546 */ 547 nak(error) 548 int error; 549 { 550 register struct tftphdr *tp; 551 int length; 552 register struct errmsg *pe; 553 554 tp = (struct tftphdr *)buf; 555 tp->th_opcode = htons((u_short)ERROR); 556 tp->th_code = htons((u_short)error); 557 for (pe = errmsgs; pe->e_code >= 0; pe++) 558 if (pe->e_code == error) 559 break; 560 if (pe->e_code < 0) { 561 pe->e_msg = strerror(error - 100); 562 tp->th_code = EUNDEF; /* set 'undef' errorcode */ 563 } 564 strcpy(tp->th_msg, pe->e_msg); 565 length = strlen(pe->e_msg); 566 tp->th_msg[length] = '\0'; 567 length += 5; 568 if (send(peer, buf, length, 0) != length) 569 syslog(LOG_ERR, "nak: %m\n"); 570 } 571