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#!/usr/bin/perl -w
#
# tftp to http proxy
# Copyright 2003 Ken Yap
# Released under GPL2
#
require 5.8.0; # needs constant and the pack Z format behaviour
use bytes; # to forestall Unicode interpretation of strings
use strict;
use Getopt::Long;
use Socket;
use Sys::Hostname;
use Sys::Syslog;
use LWP;
use POSIX 'setsid';
use constant PROGNAME => 't2hproxy';
use constant VERSION => '0.1';
use constant ETH_DATA_LEN => 1500;
use constant {
TFTP_RRQ => 1, TFTP_WRQ => 2, TFTP_DATA => 3, TFTP_ACK => 4,
TFTP_ERROR => 5, TFTP_OACK => 6
};
use constant {
E_UNDEF => 0, E_FNF => 1, E_ACC => 2, E_DISK => 3, E_ILLOP => 4,
E_UTID => 5, E_FEXIST => 6, E_NOUSER => 7
};
use vars qw($prefix $proxy $sockh $timeout %options $tsize $bsize);
# We can't use die because xinetd will think something's wrong
sub log_and_exit ($) {
syslog('info', $_[0]);
exit;
}
sub what_source ($) {
my ($port, $saddr) = sockaddr_in($_[0]);
my $host = gethostbyaddr($saddr, AF_INET);
return ($host, $port);
}
sub send_error ($$$) {
my ($iaddr, $error, $message) = @_;
# error packets don't get acked
send(STDOUT, pack('nna*', TFTP_ERROR, $error, $message), 0, $iaddr);
}
sub send_ack_retry ($$$$$) {
my ($iaddr, $udptimeout, $maxretries, $blockno, $sendfunc) = @_;
RETRY:
while ($maxretries-- > 0) {
&$sendfunc;
my $rin = '';
my $rout = '';
vec($rin, fileno($sockh), 1) = 1;
do {
my ($fds, $timeleft) = select($rout = $rin, undef, undef, $udptimeout);
last if ($fds <= 0);
my $ack;
my $theiripaddr = recv($sockh, $ack, 256, 0);
# check it's for us
if ($theiripaddr eq $iaddr) {
my ($opcode, $ackblock) = unpack('nn', $ack);
return (0) if ($opcode == TFTP_ERROR);
# check that the right block was acked
if ($ackblock == $blockno) {
return (1);
} else {
syslog('info', "Resending block $blockno");
next RETRY;
}
}
# stray packet for some other server instance
send_error($theiripaddr, E_UTID, 'Wrong TID');
} while (1);
}
return (0);
}
sub handle_options ($$) {
my ($iaddr, $operand) = @_;
while ($operand ne '') {
my ($key, $value) = unpack('Z*Z*', $operand);
$options{$key} = $value;
syslog('info', "$key=$value");
$operand = substr($operand, length($key) + length($value) + 2);
}
my $optstr = '';
if (exists($options{blksize})) {
$bsize = $options{blksize};
$bsize = 512 if ($bsize < 512);
$bsize = 1432 if ($bsize > 1432);
$optstr .= pack('Z*Z*', 'blksize', $bsize . '');
}
# OACK expects an ack for block 0
log_and_exit('Abort received or retransmit limit reached, exiting')
unless send_ack_retry($iaddr, 2, 5, 0,
sub { send($sockh, pack('na*', TFTP_OACK, $optstr), 0, $iaddr); });
}
sub http_get ($) {
my ($url) = @_;
syslog('info', "GET $url");
my $ua = LWP::UserAgent->new;
$ua->timeout($timeout);
$ua->proxy(['http', 'ftp'], $proxy) if (defined($proxy) and $proxy);
my $req = HTTP::Request->new(GET => $url);
my $res = $ua->request($req);
return ($res->is_success, $res->status_line, $res->content_ref);
}
sub send_file ($$) {
my ($iaddr, $contentref) = @_;
my $blockno = 1;
my $data;
do {
$blockno &= 0xffff;
$data = substr($$contentref, ($blockno - 1) * $bsize, $bsize);
# syslog('info', "Block $blockno length " . length($data));
log_and_exit('Abort received or retransmit limit reached, exiting')
unless send_ack_retry($iaddr, 2, 5, $blockno,
sub { send($sockh, pack('nna*', TFTP_DATA, $blockno, $data), 0, $iaddr); });
$blockno++;
} while (length($data) >= $bsize);
}
sub do_rrq ($$) {
my ($iaddr, $packetref) = @_;
# fork and handle request in child so that *inetd can continue
# to serve incoming requests
defined(my $pid = fork) or log_and_exit("Can't fork: $!");
exit if $pid; # parent exits
setsid or log_and_exit("Can't start a new session: $!");
socket(SOCK, PF_INET, SOCK_DGRAM, getprotobyname('udp')) or log_and_exit('Cannot create UDP socket');
$sockh = *SOCK{IO};
my ($opcode, $operand) = unpack('na*', $$packetref);
my ($filename, $mode) = unpack('Z*Z*', $operand);
syslog('info', "RRQ $filename $mode");
my $length = length($filename) + length($mode) + 2;
$operand = substr($operand, $length);
handle_options($iaddr, $operand) if ($operand ne '');
my ($success, $status_line, $result) = http_get($prefix . $filename);
syslog('info', $status_line);
if ($success) {
send_file($iaddr, $result);
} else {
send_error($iaddr, E_FNF, $status_line);
}
}
$prefix = 'http://localhost/';
$timeout = 60;
GetOptions('prefix=s' => \$prefix,
'proxy=s' => \$proxy,
'timeout=i' => \$timeout);
$bsize = 512;
openlog(PROGNAME, 'cons,pid', 'user');
syslog('info', PROGNAME . ' version ' . VERSION);
my $packet;
my $theiriaddr = recv(STDIN, $packet, ETH_DATA_LEN, 0);
my ($host, $port) = what_source($theiriaddr);
syslog('info', "Connection from $host:$port");
my $opcode = unpack('n', $packet);
if ($opcode == TFTP_RRQ) {
do_rrq($theiriaddr, \$packet);
} else { # anything else is an error
send_error($theiriaddr, E_ILLOP, 'Illegal operation');
}
exit 0;
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