/* vi: set sw=4 ts=4: */
/* -------------------------------------------------------------------------
* tftp.c
*
* A simple tftp client/server for busybox.
* Tries to follow RFC1350.
* Only "octet" mode supported.
* Optional blocksize negotiation (RFC2347 + RFC2348)
*
* Copyright (C) 2001 Magnus Damm <damm@opensource.se>
*
* Parts of the code based on:
*
* atftp: Copyright (C) 2000 Jean-Pierre Lefebvre <helix@step.polymtl.ca>
* and Remi Lefebvre <remi@debian.org>
*
* utftp: Copyright (C) 1999 Uwe Ohse <uwe@ohse.de>
*
* tftpd added by Denys Vlasenko
*
* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
* ------------------------------------------------------------------------- */
#include "libbb.h"
#if ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT
#define TFTP_BLOCKSIZE_DEFAULT 512 /* according to RFC 1350, don't change */
#define TFTP_TIMEOUT_MS 50
#define TFTP_MAXTIMEOUT_MS 2000
#define TFTP_NUM_RETRIES 12 /* number of backed-off retries */
/* opcodes we support */
#define TFTP_RRQ 1
#define TFTP_WRQ 2
#define TFTP_DATA 3
#define TFTP_ACK 4
#define TFTP_ERROR 5
#define TFTP_OACK 6
#if ENABLE_FEATURE_TFTP_GET && !ENABLE_FEATURE_TFTP_PUT
#define USE_GETPUT(...)
#define CMD_GET(cmd) 1
#define CMD_PUT(cmd) 0
#elif !ENABLE_FEATURE_TFTP_GET && ENABLE_FEATURE_TFTP_PUT
#define USE_GETPUT(...)
#define CMD_GET(cmd) 0
#define CMD_PUT(cmd) 1
#else
#define USE_GETPUT(...) __VA_ARGS__
/* masks coming from getopt32 */
#define CMD_GET(cmd) ((cmd) & 1)
#define CMD_PUT(cmd) ((cmd) & 2)
#endif
/* NB: in the code below
* CMD_GET(cmd) and CMD_PUT(cmd) are mutually exclusive
*/
#if ENABLE_FEATURE_TFTP_BLOCKSIZE
static int tftp_blocksize_check(int blocksize, int bufsize)
{
/* Check if the blocksize is valid:
* RFC2348 says between 8 and 65464,
* but our implementation makes it impossible
* to use blocksizes smaller than 22 octets.
*/
if ((bufsize && (blocksize > bufsize))
|| (blocksize < 24) || (blocksize > 65564)
) {
bb_error_msg("bad blocksize");
return 0;
}
return blocksize;
}
static char *tftp_option_get(char *buf, int len, const char *option)
{
int opt_val = 0;
int opt_found = 0;
int k;
/* buf points to:
* "opt_name<NUL>opt_val<NUL>opt_name2<NUL>opt_val2<NUL>..." */
while (len > 0) {
/* Make sure options are terminated correctly */
for (k = 0; k < len; k++) {
if (buf[k] == '\0') {
goto nul_found;
}
}
return NULL;
nul_found:
if (opt_val == 0) { /* it's "name" part */
if (strcasecmp(buf, option) == 0) {
opt_found = 1;
}
} else if (opt_found) {
return buf;
}
k++;
buf += k;
len -= k;
opt_val ^= 1;
}
return NULL;
}
#endif
static int tftp_protocol(
USE_GETPUT(int cmd,)
len_and_sockaddr *our_lsa,
len_and_sockaddr *peer_lsa,
USE_TFTP(const char *remote_file,)
int local_fd,
int blocksize)
{
#if !ENABLE_TFTP
#define remote_file NULL
#endif
struct pollfd pfd[1];
#define socket_fd (pfd[0].fd)
int len;
int send_len;
USE_FEATURE_TFTP_BLOCKSIZE(smallint want_option_ack = 0;)
smallint finished = 0;
uint16_t opcode;
uint16_t block_nr;
uint16_t recv_blk;
int retries, waittime_ms;
int tftp_bufsize = blocksize + 4;
char *cp;
/* Can't use RESERVE_CONFIG_BUFFER here since the allocation
* size varies meaning BUFFERS_GO_ON_STACK would fail */
/* We must keep the transmit and receive buffers seperate */
/* In case we rcv a garbage pkt and we need to rexmit the last pkt */
char *xbuf = xmalloc(tftp_bufsize);
char *rbuf = xmalloc(tftp_bufsize);
socket_fd = xsocket(peer_lsa->u.sa.sa_family, SOCK_DGRAM, 0);
setsockopt_reuseaddr(socket_fd);
if (!ENABLE_TFTP || our_lsa) {
/* tftpd */
block_nr = 0;
/* Create a socket which is:
* 1. bound to IP:port peer sent 1st datagram to,
* 2. connected to peer's IP:port
* This way we will answer from the IP:port peer
* expects, will not get any other packets on
* the socket, and also plain read/write will work. */
xbind(socket_fd, &our_lsa->u.sa, our_lsa->len);
xconnect(socket_fd, &peer_lsa->u.sa, peer_lsa->len);
#if ENABLE_FEATURE_TFTP_BLOCKSIZE
if (blocksize != TFTP_BLOCKSIZE_DEFAULT) {
/* Create and send OACK packet */
opcode = TFTP_OACK;
cp = xbuf + 2;
goto add_blksize_opt;
}
/* else: just fall into while (1) loop below */
#endif
} else {
/* tftp */
block_nr = 1;
/* We can't (and don't really need to) bind the socket:
* we don't know from which local IP datagrams will be sent,
* but kernel will pick the same IP every time (unless routing
* table is changed), thus peer will see dgrams consistently
* coming from the same IP.
* We would like to connect the socket, but since peer's
* UDP code can be less perfect than ours, _peer's_ IP:port
* in replies may differ from IP:port we used to send
* our first packet. We can connect() only when we get
* first reply. */
/* build opcode */
opcode = TFTP_WRQ;
if (CMD_GET(cmd)) {
opcode = TFTP_RRQ;
}
cp = xbuf + 2;
/* add filename and mode */
/* fill in packet if the filename fits into xbuf */
len = strlen(remote_file) + 1;
if (2 + len + sizeof("octet") >= tftp_bufsize) {
bb_error_msg("remote filename is too long");
goto ret;
}
strcpy(cp, remote_file);
cp += len;
/* add "mode" part of the package */
strcpy(cp, "octet");
cp += sizeof("octet");
#if ENABLE_FEATURE_TFTP_BLOCKSIZE
if (blocksize != TFTP_BLOCKSIZE_DEFAULT) {
/* rfc2348 says that 65464 is a max allowed value */
if ((&xbuf[tftp_bufsize - 1] - cp) < sizeof("blksize NNNNN")) {
bb_error_msg("remote filename is too long");
goto ret;
}
want_option_ack = 1;
add_blksize_opt:
/* add "blksize", <nul>, blocksize, <nul> */
strcpy(cp, "blksize");
cp += sizeof("blksize");
cp += snprintf(cp, 6, "%d", blocksize) + 1;
}
#endif
/* First packet is built, so skip packet generation */
goto send_pkt;
}
/* Using mostly goto's - continue/break will be less clear
* in where we actually jump to */
while (1) {
/* Build ACK or DATA */
cp = xbuf + 2;
*((uint16_t*)cp) = htons(block_nr);
cp += 2;
block_nr++;
opcode = TFTP_ACK;
if (CMD_PUT(cmd)) {
opcode = TFTP_DATA;
len = full_read(local_fd, cp, tftp_bufsize - 4);
if (len < 0) {
bb_perror_msg(bb_msg_read_error);
goto ret;
}
if (len != (tftp_bufsize - 4)) {
finished = 1;
}
cp += len;
}
send_pkt:
/* Send packet */
*((uint16_t*)xbuf) = htons(opcode); /* fill in opcode part */
send_len = cp - xbuf;
/* NB: send_len value is preserved in code below
* for potential resend */
retries = TFTP_NUM_RETRIES; /* re-initialize */
waittime_ms = TFTP_TIMEOUT_MS;
send_again:
#if ENABLE_DEBUG_TFTP
fprintf(stderr, "sending %u bytes\n", send_len);
for (cp = xbuf; cp < &xbuf[send_len]; cp++)
fprintf(stderr, "%02x ", (unsigned char) *cp);
fprintf(stderr, "\n");
#endif
xsendto(socket_fd, xbuf, send_len, &peer_lsa->u.sa, peer_lsa->len);
/* Was it final ACK? then exit */
if (finished && (opcode == TFTP_ACK))
goto ret;
recv_again:
/* Receive packet */
/*pfd[0].fd = socket_fd;*/
pfd[0].events = POLLIN;
switch (safe_poll(pfd, 1, waittime_ms)) {
case 1:
if (!our_lsa) {
/* tftp (not tftpd!) receiving 1st packet */
our_lsa = ((void*)(ptrdiff_t)-1); /* not NULL */
len = recvfrom(socket_fd, rbuf, tftp_bufsize, 0,
&peer_lsa->u.sa, &peer_lsa->len);
/* Our first dgram went to port 69
* but reply may come from different one.
* Remember and use this new port (and IP) */
if (len >= 0)
xconnect(socket_fd, &peer_lsa->u.sa, peer_lsa->len);
} else {
/* tftpd, or not the very first packet:
* socket is connect()ed, can just read from it. */
len = safe_read(socket_fd, rbuf, tftp_bufsize);
}
if (len < 0) {
bb_perror_msg("read");
goto ret;
}
goto process_pkt;
case 0:
retries--;
if (retries == 0) {
bb_error_msg("timeout");
goto ret;
}
/* exponential backoff with limit */
waittime_ms += waittime_ms/2;
if (waittime_ms > TFTP_MAXTIMEOUT_MS) {
waittime_ms = TFTP_MAXTIMEOUT_MS;
}
goto send_again; /* resend last sent pkt */
default:
/*bb_perror_msg("poll"); - done in safe_poll */
goto ret;
}
process_pkt:
/* Process recv'ed packet */
opcode = ntohs( ((uint16_t*)rbuf)[0] );
recv_blk = ntohs( ((uint16_t*)rbuf)[1] );
#if ENABLE_DEBUG_TFTP
fprintf(stderr, "received %d bytes: %04x %04x\n", len, opcode, recv_blk);
#endif
if (opcode == TFTP_ERROR) {
static const char *const errcode_str[] = {
"",
"file not found",
"access violation",
"disk full",
"illegal TFTP operation",
"unknown transfer id",
"file already exists",
"no such user",
"bad option"
};
const char *msg = "";
if (rbuf[4] != '\0') {
msg = &rbuf[4];
rbuf[tftp_bufsize - 1] = '\0';
} else if (recv_blk < ARRAY_SIZE(errcode_str)) {
msg = errcode_str[recv_blk];
}
bb_error_msg("server error: (%u) %s", recv_blk, msg);
goto ret;
}
#if ENABLE_FEATURE_TFTP_BLOCKSIZE
if (want_option_ack) {
want_option_ack = 0;
if (opcode == TFTP_OACK) {
/* server seems to support options */
char *res;
res = tftp_option_get(&rbuf[2], len - 2, "blksize");
if (res) {
int blksize = xatoi_u(res);
if (!tftp_blocksize_check(blksize, tftp_bufsize - 4)) {
/* send ERROR 8 to server... */
/* htons can be impossible to use in const initializer: */
/*static const uint16_t error_8[2] = { htons(TFTP_ERROR), htons(8) };*/
/* thus we open-code big-endian layout */
static const uint8_t error_8[4] = { 0,TFTP_ERROR, 0,8 };
xsendto(socket_fd, error_8, 4, &peer_lsa->u.sa, peer_lsa->len);
bb_error_msg("server proposes bad blksize %d, exiting", blksize);
goto ret;
}
#if ENABLE_DEBUG_TFTP
fprintf(stderr, "using blksize %u\n",
blksize);
#endif
tftp_bufsize = blksize + 4;
/* Send ACK for OACK ("block" no: 0) */
block_nr = 0;
continue;
}
/* rfc2347:
* "An option not acknowledged by the server
* must be ignored by the client and server
* as if it were never requested." */
}
bb_error_msg("blksize is not supported by server"
" - reverting to 512");
tftp_bufsize = TFTP_BLOCKSIZE_DEFAULT + 4;
}
#endif
/* block_nr is already advanced to next block# we expect
* to get / block# we are about to send next time */
if (CMD_GET(cmd) && (opcode == TFTP_DATA)) {
if (recv_blk == block_nr) {
len = full_write(local_fd, &rbuf[4], len - 4);
if (len < 0) {
bb_perror_msg(bb_msg_write_error);
goto ret;
}
if (len != (tftp_bufsize - 4)) {
finished = 1;
}
continue; /* send ACK */
}
if (recv_blk == (block_nr - 1)) {
/* Server lost our TFTP_ACK. Resend it */
block_nr = recv_blk;
continue;
}
}
if (CMD_PUT(cmd) && (opcode == TFTP_ACK)) {
/* did peer ACK our last DATA pkt? */
if (recv_blk == (uint16_t) (block_nr - 1)) {
if (finished)
goto ret;
continue; /* send next block */
}
}
/* Awww... recv'd packet is not recognized! */
goto recv_again;
/* why recv_again? - rfc1123 says:
* "The sender (i.e., the side originating the DATA packets)
* must never resend the current DATA packet on receipt
* of a duplicate ACK".
* DATA pkts are resent ONLY on timeout.
* Thus "goto send_again" will ba a bad mistake above.
* See:
* http://en.wikipedia.org/wiki/Sorcerer's_Apprentice_Syndrome
*/
} /* end of "while (1)" */
ret:
if (ENABLE_FEATURE_CLEAN_UP) {
close(socket_fd);
free(xbuf);
free(rbuf);
}
return finished == 0; /* returns 1 on failure */
}
#if ENABLE_TFTP
int tftp_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int tftp_main(int argc ATTRIBUTE_UNUSED, char **argv)
{
len_and_sockaddr *peer_lsa;
const char *local_file = NULL;
const char *remote_file = NULL;
int port;
USE_GETPUT(int cmd;)
int local_fd;
int flags = 0;
int result;
int blocksize = TFTP_BLOCKSIZE_DEFAULT;
/* -p or -g is mandatory, and they are mutually exclusive */
opt_complementary = "" USE_FEATURE_TFTP_GET("g:") USE_FEATURE_TFTP_PUT("p:")
USE_GETPUT("g--p:p--g:")
USE_FEATURE_TFTP_BLOCKSIZE("b+");
USE_GETPUT(cmd =) getopt32(argv,
USE_FEATURE_TFTP_GET("g") USE_FEATURE_TFTP_PUT("p")
"l:r:" USE_FEATURE_TFTP_BLOCKSIZE("b:"),
&local_file, &remote_file
USE_FEATURE_TFTP_BLOCKSIZE(, &blocksize));
argv += optind;
flags = O_RDONLY;
if (CMD_GET(cmd))
flags = O_WRONLY | O_CREAT | O_TRUNC;
#if ENABLE_FEATURE_TFTP_BLOCKSIZE
if (!tftp_blocksize_check(blocksize, 0))
return EXIT_FAILURE;
#endif
if (!local_file)
local_file = remote_file;
if (!remote_file)
remote_file = local_file;
/* Error if filename or host is not known */
if (!remote_file || !argv[0])
bb_show_usage();
local_fd = CMD_GET(cmd) ? STDOUT_FILENO : STDIN_FILENO;
if (!LONE_DASH(local_file)) {
local_fd = xopen(local_file, flags);
}
port = bb_lookup_port(argv[1], "udp", 69);
peer_lsa = xhost2sockaddr(argv[0], port);
#if ENABLE_DEBUG_TFTP
fprintf(stderr, "using server '%s', remote_file '%s', local_file '%s'\n",
xmalloc_sockaddr2dotted(&peer_lsa->u.sa),
remote_file, local_file);
#endif
result = tftp_protocol(
USE_GETPUT(cmd,)
NULL /* our_lsa*/,
peer_lsa,
remote_file, local_fd, blocksize);
if (ENABLE_FEATURE_CLEAN_UP)
close(local_fd);
if (result != EXIT_SUCCESS && !LONE_DASH(local_file) && CMD_GET(cmd)) {
unlink(local_file);
}
return result;
}
#endif /* ENABLE_TFTP */
#if ENABLE_TFTPD
/* TODO: libbb candidate? */
static len_and_sockaddr *get_sock_lsa(int s)
{
len_and_sockaddr *lsa;
socklen_t len = 0;
if (getsockname(s, NULL, &len) != 0)
return NULL;
lsa = xzalloc(LSA_LEN_SIZE + len);
lsa->len = len;
getsockname(s, &lsa->u.sa, &lsa->len);
return lsa;
}
int tftpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int tftpd_main(int argc ATTRIBUTE_UNUSED, char **argv ATTRIBUTE_UNUSED)
{
struct stat statbuf;
char block_buf[TFTP_BLOCKSIZE_DEFAULT];
len_and_sockaddr *our_lsa;
len_and_sockaddr *peer_lsa;
char *filename, *mode, *opt_str;
int result, opcode, cmd, req_modebits, open_mode, local_fd, blksize;
our_lsa = get_sock_lsa(STDIN_FILENO);
if (!our_lsa)
bb_perror_msg_and_die("stdin is not a socket");
peer_lsa = xzalloc(LSA_LEN_SIZE + our_lsa->len);
peer_lsa->len = our_lsa->len;
if (argv[1])
xchdir(argv[1]);
result = recv_from_to(STDIN_FILENO, block_buf, sizeof(block_buf),
0 /* flags */,
&peer_lsa->u.sa, &our_lsa->u.sa, our_lsa->len);
opcode = ntohs(*(uint16_t*)block_buf);
if (result < 4 || result >= sizeof(block_buf)
|| block_buf[result-1] != '\0'
|| (opcode != TFTP_RRQ && opcode != TFTP_WRQ)
) {
bb_error_msg_and_die("malformed packet");
}
filename = block_buf + 2;
if (filename[0] == '.' || strstr(filename, "/.")) {
bb_error_msg_and_die("dot in filename");
}
mode = filename + strlen(filename) + 1;
if (mode >= block_buf + sizeof(block_buf)
|| strcmp(mode, "octet") != 0
) {
bb_error_msg_and_die("malformed packet");
}
blksize = TFTP_BLOCKSIZE_DEFAULT;
#if ENABLE_FEATURE_TFTP_BLOCKSIZE
opt_str = mode + 6;
if (opt_str < block_buf + sizeof(block_buf)) {
char *res = tftp_option_get(opt_str, block_buf + sizeof(block_buf) - opt_str, "blksize");
if (res) {
int sz = xatoi_u(res);
if (tftp_blocksize_check(sz, 0))
blksize = sz;
}
}
#endif
xstat(filename, &statbuf);
/* if opcode == TFTP_WRQ: */
cmd = 1; /* CMD_GET: we will receive file's data */
req_modebits = 0222; /* writable by anyone */
open_mode = O_WRONLY | O_TRUNC;
if (opcode == TFTP_RRQ) {
cmd = 2; /* CMD_PUT */
req_modebits = 0444; /* readable by anyone */
open_mode = O_RDONLY;
}
if (!S_ISREG(statbuf.st_mode)
|| (statbuf.st_mode & req_modebits) != req_modebits
) {
bb_error_msg_and_die("access to '%s' is denied", filename);
}
local_fd = xopen(filename, open_mode);
close(STDIN_FILENO); /* close old, possibly wildcard socket */
/* tftp_protocol() will create new one, bound to particular local IP */
result = tftp_protocol(
USE_GETPUT(cmd,)
our_lsa, peer_lsa,
USE_TFTP(NULL /*remote_file*/,)
local_fd,
blksize
);
return result;
}
#endif /* ENABLE_TFTPD */
#endif /* ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT */