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