1 /* 2 * Copyright (c) 1983 Regents of the University of California. 3 * All rights reserved. The Berkeley software License Agreement 4 * specifies the terms and conditions for redistribution. 5 */ 6 7 #ifndef lint 8 char copyright[] = 9 "@(#) Copyright (c) 1983 Regents of the University of California.\n\ 10 All rights reserved.\n"; 11 #endif not lint 12 13 #ifndef lint 14 static char sccsid[] = "@(#)tftpd.c 5.6 (Berkeley) 05/13/86"; 15 #endif not lint 16 17 18 /* 19 * Trivial file transfer protocol server. 20 * 21 * This version includes many modifications by Jim Guyton <guyton@rand-unix> 22 */ 23 24 #include <sys/types.h> 25 #include <sys/socket.h> 26 #include <sys/ioctl.h> 27 #include <sys/wait.h> 28 #include <sys/stat.h> 29 30 #include <netinet/in.h> 31 32 #include <arpa/tftp.h> 33 34 #include <signal.h> 35 #include <stdio.h> 36 #include <errno.h> 37 #include <ctype.h> 38 #include <netdb.h> 39 #include <setjmp.h> 40 #include <syslog.h> 41 42 #define TIMEOUT 5 43 44 extern int errno; 45 struct sockaddr_in sin = { AF_INET }; 46 int peer; 47 int rexmtval = TIMEOUT; 48 int maxtimeout = 5*TIMEOUT; 49 50 #define PKTSIZE SEGSIZE+4 51 char buf[PKTSIZE]; 52 char ackbuf[PKTSIZE]; 53 struct sockaddr_in from; 54 int fromlen; 55 56 main() 57 { 58 register struct tftphdr *tp; 59 register int n; 60 int on = 1; 61 62 openlog("tftpd", LOG_PID, LOG_DAEMON); 63 if (ioctl(0, FIONBIO, &on) < 0) { 64 syslog(LOG_ERR, "ioctl(FIONBIO): %m\n"); 65 exit(1); 66 } 67 fromlen = sizeof (from); 68 n = recvfrom(0, buf, sizeof (buf), 0, 69 (caddr_t)&from, &fromlen); 70 if (n < 0) { 71 syslog(LOG_ERR, "recvfrom: %m\n"); 72 exit(1); 73 } 74 /* 75 * Now that we have read the message out of the UDP 76 * socket, we fork and exit. Thus, inetd will go back 77 * to listening to the tftp port, and the next request 78 * to come in will start up a new instance of tftpd. 79 * 80 * We do this so that inetd can run tftpd in "wait" mode. 81 * The problem with tftpd running in "nowait" mode is that 82 * inetd may get one or more successful "selects" on the 83 * tftp port before we do our receive, so more than one 84 * instance of tftpd may be started up. Worse, if tftpd 85 * break before doing the above "recvfrom", inetd would 86 * spawn endless instances, clogging the system. 87 */ 88 { 89 int pid; 90 int i, j; 91 92 for (i = 1; i < 20; i++) { 93 pid = fork(); 94 if (pid < 0) { 95 sleep(i); 96 /* 97 * flush out to most recently sent request. 98 * 99 * This may drop some request, but those 100 * will be resent by the clients when 101 * they timeout. The positive effect of 102 * this flush is to (try to) prevent more 103 * than one tftpd being started up to service 104 * a single request from a single client. 105 */ 106 j = sizeof from; 107 i = recvfrom(0, buf, sizeof (buf), 0, 108 (caddr_t)&from, &j); 109 if (i > 0) { 110 n = i; 111 fromlen = j; 112 } 113 } else { 114 break; 115 } 116 } 117 if (pid < 0) { 118 syslog(LOG_ERR, "fork: %m\n"); 119 exit(1); 120 } else if (pid != 0) { 121 exit(0); 122 } 123 } 124 from.sin_family = AF_INET; 125 alarm(0); 126 close(0); 127 close(1); 128 peer = socket(AF_INET, SOCK_DGRAM, 0); 129 if (peer < 0) { 130 syslog(LOG_ERR, "socket: %m\n"); 131 exit(1); 132 } 133 if (bind(peer, (caddr_t)&sin, sizeof (sin)) < 0) { 134 syslog(LOG_ERR, "bind: %m\n"); 135 exit(1); 136 } 137 if (connect(peer, (caddr_t)&from, sizeof(from)) < 0) { 138 syslog(LOG_ERR, "connect: %m\n"); 139 exit(1); 140 } 141 tp = (struct tftphdr *)buf; 142 tp->th_opcode = ntohs(tp->th_opcode); 143 if (tp->th_opcode == RRQ || tp->th_opcode == WRQ) 144 tftp(tp, n); 145 exit(1); 146 } 147 148 int validate_access(); 149 int sendfile(), recvfile(); 150 151 struct formats { 152 char *f_mode; 153 int (*f_validate)(); 154 int (*f_send)(); 155 int (*f_recv)(); 156 int f_convert; 157 } formats[] = { 158 { "netascii", validate_access, sendfile, recvfile, 1 }, 159 { "octet", validate_access, sendfile, recvfile, 0 }, 160 #ifdef notdef 161 { "mail", validate_user, sendmail, recvmail, 1 }, 162 #endif 163 { 0 } 164 }; 165 166 /* 167 * Handle initial connection protocol. 168 */ 169 tftp(tp, size) 170 struct tftphdr *tp; 171 int size; 172 { 173 register char *cp; 174 int first = 1, ecode; 175 register struct formats *pf; 176 char *filename, *mode; 177 178 filename = cp = tp->th_stuff; 179 again: 180 while (cp < buf + size) { 181 if (*cp == '\0') 182 break; 183 cp++; 184 } 185 if (*cp != '\0') { 186 nak(EBADOP); 187 exit(1); 188 } 189 if (first) { 190 mode = ++cp; 191 first = 0; 192 goto again; 193 } 194 for (cp = mode; *cp; cp++) 195 if (isupper(*cp)) 196 *cp = tolower(*cp); 197 for (pf = formats; pf->f_mode; pf++) 198 if (strcmp(pf->f_mode, mode) == 0) 199 break; 200 if (pf->f_mode == 0) { 201 nak(EBADOP); 202 exit(1); 203 } 204 ecode = (*pf->f_validate)(filename, tp->th_opcode); 205 if (ecode) { 206 nak(ecode); 207 exit(1); 208 } 209 if (tp->th_opcode == WRQ) 210 (*pf->f_recv)(pf); 211 else 212 (*pf->f_send)(pf); 213 exit(0); 214 } 215 216 217 FILE *file; 218 219 /* 220 * Validate file access. Since we 221 * have no uid or gid, for now require 222 * file to exist and be publicly 223 * readable/writable. 224 * Note also, full path name must be 225 * given as we have no login directory. 226 */ 227 validate_access(filename, mode) 228 char *filename; 229 int mode; 230 { 231 struct stat stbuf; 232 int fd; 233 234 if (*filename != '/') 235 return (EACCESS); 236 if (stat(filename, &stbuf) < 0) 237 return (errno == ENOENT ? ENOTFOUND : EACCESS); 238 if (mode == RRQ) { 239 if ((stbuf.st_mode&(S_IREAD >> 6)) == 0) 240 return (EACCESS); 241 } else { 242 if ((stbuf.st_mode&(S_IWRITE >> 6)) == 0) 243 return (EACCESS); 244 } 245 fd = open(filename, mode == RRQ ? 0 : 1); 246 if (fd < 0) 247 return (errno + 100); 248 file = fdopen(fd, (mode == RRQ)? "r":"w"); 249 if (file == NULL) { 250 return errno+100; 251 } 252 return (0); 253 } 254 255 int timeout; 256 jmp_buf timeoutbuf; 257 258 timer() 259 { 260 261 timeout += rexmtval; 262 if (timeout >= maxtimeout) 263 exit(1); 264 longjmp(timeoutbuf, 1); 265 } 266 267 /* 268 * Send the requested file. 269 */ 270 sendfile(pf) 271 struct formats *pf; 272 { 273 struct tftphdr *dp, *r_init(); 274 register struct tftphdr *ap; /* ack packet */ 275 register int block = 1, size, n; 276 277 signal(SIGALRM, timer); 278 dp = r_init(); 279 ap = (struct tftphdr *)ackbuf; 280 do { 281 size = readit(file, &dp, pf->f_convert); 282 if (size < 0) { 283 nak(errno + 100); 284 goto abort; 285 } 286 dp->th_opcode = htons((u_short)DATA); 287 dp->th_block = htons((u_short)block); 288 timeout = 0; 289 (void) setjmp(timeoutbuf); 290 291 send_data: 292 if (send(peer, dp, size + 4, 0) != size + 4) { 293 syslog(LOG_ERR, "tftpd: write: %m\n"); 294 goto abort; 295 } 296 read_ahead(file, pf->f_convert); 297 for ( ; ; ) { 298 alarm(rexmtval); /* read the ack */ 299 n = recv(peer, ackbuf, sizeof (ackbuf), 0); 300 alarm(0); 301 if (n < 0) { 302 syslog(LOG_ERR, "tftpd: read: %m\n"); 303 goto abort; 304 } 305 ap->th_opcode = ntohs((u_short)ap->th_opcode); 306 ap->th_block = ntohs((u_short)ap->th_block); 307 308 if (ap->th_opcode == ERROR) 309 goto abort; 310 311 if (ap->th_opcode == ACK) { 312 if (ap->th_block == block) { 313 break; 314 } 315 /* Re-synchronize with the other side */ 316 (void) synchnet(peer); 317 if (ap->th_block == (block -1)) { 318 goto send_data; 319 } 320 } 321 322 } 323 block++; 324 } while (size == SEGSIZE); 325 abort: 326 (void) fclose(file); 327 } 328 329 justquit() 330 { 331 exit(0); 332 } 333 334 335 /* 336 * Receive a file. 337 */ 338 recvfile(pf) 339 struct formats *pf; 340 { 341 struct tftphdr *dp, *w_init(); 342 register struct tftphdr *ap; /* ack buffer */ 343 register int block = 0, n, size; 344 345 signal(SIGALRM, timer); 346 dp = w_init(); 347 ap = (struct tftphdr *)ackbuf; 348 do { 349 timeout = 0; 350 ap->th_opcode = htons((u_short)ACK); 351 ap->th_block = htons((u_short)block); 352 block++; 353 (void) setjmp(timeoutbuf); 354 send_ack: 355 if (send(peer, ackbuf, 4, 0) != 4) { 356 syslog(LOG_ERR, "tftpd: write: %m\n"); 357 goto abort; 358 } 359 write_behind(file, pf->f_convert); 360 for ( ; ; ) { 361 alarm(rexmtval); 362 n = recv(peer, dp, PKTSIZE, 0); 363 alarm(0); 364 if (n < 0) { /* really? */ 365 syslog(LOG_ERR, "tftpd: read: %m\n"); 366 goto abort; 367 } 368 dp->th_opcode = ntohs((u_short)dp->th_opcode); 369 dp->th_block = ntohs((u_short)dp->th_block); 370 if (dp->th_opcode == ERROR) 371 goto abort; 372 if (dp->th_opcode == DATA) { 373 if (dp->th_block == block) { 374 break; /* normal */ 375 } 376 /* Re-synchronize with the other side */ 377 (void) synchnet(peer); 378 if (dp->th_block == (block-1)) 379 goto send_ack; /* rexmit */ 380 } 381 } 382 /* size = write(file, dp->th_data, n - 4); */ 383 size = writeit(file, &dp, n - 4, pf->f_convert); 384 if (size != (n-4)) { /* ahem */ 385 if (size < 0) nak(errno + 100); 386 else nak(ENOSPACE); 387 goto abort; 388 } 389 } while (size == SEGSIZE); 390 write_behind(file, pf->f_convert); 391 (void) fclose(file); /* close data file */ 392 393 ap->th_opcode = htons((u_short)ACK); /* send the "final" ack */ 394 ap->th_block = htons((u_short)(block)); 395 (void) send(peer, ackbuf, 4, 0); 396 397 signal(SIGALRM, justquit); /* just quit on timeout */ 398 alarm(rexmtval); 399 n = recv(peer, buf, sizeof (buf), 0); /* normally times out and quits */ 400 alarm(0); 401 if (n >= 4 && /* if read some data */ 402 dp->th_opcode == DATA && /* and got a data block */ 403 block == dp->th_block) { /* then my last ack was lost */ 404 (void) send(peer, ackbuf, 4, 0); /* resend final ack */ 405 } 406 abort: 407 return; 408 } 409 410 struct errmsg { 411 int e_code; 412 char *e_msg; 413 } errmsgs[] = { 414 { EUNDEF, "Undefined error code" }, 415 { ENOTFOUND, "File not found" }, 416 { EACCESS, "Access violation" }, 417 { ENOSPACE, "Disk full or allocation exceeded" }, 418 { EBADOP, "Illegal TFTP operation" }, 419 { EBADID, "Unknown transfer ID" }, 420 { EEXISTS, "File already exists" }, 421 { ENOUSER, "No such user" }, 422 { -1, 0 } 423 }; 424 425 /* 426 * Send a nak packet (error message). 427 * Error code passed in is one of the 428 * standard TFTP codes, or a UNIX errno 429 * offset by 100. 430 */ 431 nak(error) 432 int error; 433 { 434 register struct tftphdr *tp; 435 int length; 436 register struct errmsg *pe; 437 extern char *sys_errlist[]; 438 439 tp = (struct tftphdr *)buf; 440 tp->th_opcode = htons((u_short)ERROR); 441 tp->th_code = htons((u_short)error); 442 for (pe = errmsgs; pe->e_code >= 0; pe++) 443 if (pe->e_code == error) 444 break; 445 if (pe->e_code < 0) { 446 pe->e_msg = sys_errlist[error - 100]; 447 tp->th_code = EUNDEF; /* set 'undef' errorcode */ 448 } 449 strcpy(tp->th_msg, pe->e_msg); 450 length = strlen(pe->e_msg); 451 tp->th_msg[length] = '\0'; 452 length += 5; 453 if (send(peer, buf, length, 0) != length) 454 syslog(LOG_ERR, "nak: %m\n"); 455 } 456