If you are writing some Ring0 (or privileged mode code), say something like device drivers in Windows you’d probably be better served with a separate development machine and a deployment machine. This helps you to write poor code and still not lose hair because your development machine blue screens! 🙂

My setup was using a Windows 8.1 development machine and a Hyper-V based Windows 7 machine for debugging. You will need to execute different tasks on the “guest” (Hyper-V based Windows 7 virtual machine) and some other tasks on the development machine.  I followed many of the things from the MSDN blog post here

On your guest machine you would want to setup a named pipe and setup debug settings. To do that this is what you need to do:

Setup a virtual com port in the Hyper-V Settings (File -> Settings) , this port will be used to communicate from the host machine to the guest to communicate the Kernel debugging commands.

Now make sure that your target guest machine is configured to “listen” those commands.  Inside the guest VM, start a command shell (cmd.exe -> Run as Administrator).

Configure the bcdedit commands so that the machine can now be debugged.  Right after the 2nd command, reboot your Virtual Machine.

With the VM now configured to listen the debug commands via the COM1 port, and the debug mode on in the bootup settings, now start the WinDbg x64 on the host (using “Run as administrator”; you need administrative privileges for communication via Serial port).  In your kernel debugger on the host or the development machine (I’m assuming that these are both on the same physical hardware here).  Click on File -> Kernel Debug and you should see the following screen in the WinDbg window:

Hit Ctrl+Break or Debug -> Break and you will see something like this:

Just remember that when you break in the debugger, your guest in Hyper-V should become “unresponsive”.  The only thing is that it is not really unresponsive, its just being debugged.  Just to make sure, that you have the symbols package that is quite useful for debugging run the following command:

!process 0 0

If you see something like the following screen show up:

The following error means that the symbols are not defined.  Symbols help the debugger give more information about the commands that you are going to execute in the debugger.

**** NT ACTIVE PROCESS DUMP ****
NT symbols are incorrect, please fix symbols

To fix this, use the following commands:

kd> .sympath SRV*c:\symcache*http://msdl.microsoft.com/download/symbols
kd> .symfix
kd> .symfix c:\symcache
kd> !sym noisy
kd> .reload /o

Then again try the command: !process 0 0 and see if you get a good response.  A good response looks like the following:

With this you should be good to go! Happy debugging and writing cool Ring0 code.

I recently purchased a Proxmark3 from GeZhi Electronics. The proxmark3 client wouldn’t work. In fact the `dmesg` output did not even show the /dev/ttyACM0 device as was said all across the forum. i tried flashing the firmware but kept getting this error:

~/proxmark3/client# ./flasher -b ../bootrom/obj/bootrom.elf 
Loading ELF file '../bootrom/obj/bootrom.elf'...
Loading usable ELF segments:
0: V 0x00100000 P 0x00100000 (0x00000200->0x00000200) [R X] @0x94
1: V 0x00200000 P 0x00100200 (0x00000b38->0x00000b38) [RWX] @0x298
Attempted to write bootloader but bootloader writes are not enabled
Error while loading ../bootrom/obj/bootrom.elf

Also this is what showed up in the dmesg:

[ 7953.991935] usb 2-1.4: new full-speed USB device number 40 using ehci_hcd
[ 7959.078302] usb 2-1.4: New USB device found, idVendor=9ac4, idProduct=4b8f
[ 7959.078314] usb 2-1.4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 7959.078321] usb 2-1.4: Product: ProxMark-3 RFID Instrument
[ 7959.078326] usb 2-1.4: Manufacturer: J. Westhues
[ 7959.078331] usb 2-1.4: SerialNumber: ChangeMe
[ 7959.080485] hid-generic 0003:9AC4:4B8F.0014: hiddev0,hidraw0: USB HID v1.00 Device [J. Westhues ProxMark-3 RFID Instrument] on usb-0000:00:1d.0-1.4/input0

Note that in the above the device doesn’t show up as a /dev/ttyACM0 device which is what we need for the proxmark3 client application to work.
So it seemed like there was an issue with the Proxmark3 not being recognized as a CDC device. So I went through the googlecode repository and went to a version of firmware where CDC was not being used. It also seemed that the flasher was the issue. So I used an old flasher to flash with the latest firmware and boom it worked! Remember to keep the button on the Proxmark3 pressed when you plug it in, and keep holding it down until the firmware update has finished.
Here are the commands:

# svn checkout http://proxmark3.googlecode.com/svn/trunk/ proxmark3
# export DEVKITPRO=$HOME/proxmark3/
# export DEVKITARM=$DEVKITPRO/devkitARM
# export PATH=${PATH}:${DEVKITARM}/bin
# cd proxmark3
# make all
# cd ..
# svn checkout -r 629 http://proxmark3.googlecode.com/svn/trunk/ ~/proxmark3-old-3
# cd proxmark3-old-3/
# make all
# cd client
# ./flasher -b ../../proxmark3/bootrom/obj/bootrom.elf ../../proxmark3/armsrc/obj/osimage.elf ../../proxmark3/armsrc/obj/fpgaimage.elf

And boom! There you … all flashed and now the device is recognized as a /dev/ttyACM0 device.

hey, we need to check that your connection works, torrent this file and md5 it

http://services.2014.shallweplayaga.me/hackertool.torrent_fe3b8b75e9639d35e8ac1d9809726ee2

The torrent file when loaded into Vuze showed that the file name was every_ip_address.txt. So I downloaded some of the file and observed the format. The format of the file was “0.0.0.1\n0.0.0.2\n…. “.

So I wrote a quick python script to calculate the md5:

#!/bin/python
import hashlib
m = hashlib.md5()
fsize = 0
a = ''
for i in xrange(256):
    for j in xrange(256):
        for k in xrange(256):
            for l in xrange(256):
                a = str(i)+'.'+str(j)+'.'+str(k)+'.'+str(l)+'\n'
                fsize += len(a)
                m.update( a )
print m.hexdigest()

The flag was “1a97f624cc74e4944350c04f5ae1fe8d”.

If you use Windows 8 x64 and when you launch the Cisco VPN Client adapter and you see the following error:
Reason 442: Failed To Enable Virtual Adapter Here’s how to fix it.
Open your command prompt in Administrator mode by right clicking at the left lower corner of the screen and going to “Command Prompt (Administrator)”. You will have to log in as an administrator. Launch registry editor by typing “regedit.exe”. Browse to “HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\CVirtA“. In the DisplayName key, you will see something like @oem8.inf,%CVirtA_Desc%;Cisco Systems VPN Adapter. Edit that to just say Cisco Systems VPN Adapter. Try to connect again by launching the VPN Client. It should work!

On the recently concluded PlaidCTF (which was an awesome competition) by PPP there was a problem.  Here it goes:

Question: We managed to get the source code for an encryption service running at 54.234.224.216:4433.

I have listed the python source provided below:

#!/usr/bin/python
import os
import struct
import SocketServer
import zlib
from Crypto.Cipher import AES
from Crypto.Util import Counter

# Not the real keys!
ENCRYPT_KEY = '0000000000000000000000000000000000000000000000000000000000000000'.decode('hex')
# Determine this key.
# Character set: lowercase letters and underscore
PROBLEM_KEY = 'XXXXXXXXXXXXXXXXXXXX'

def encrypt(data, ctr):
    aes = AES.new(ENCRYPT_KEY, AES.MODE_CTR, counter=ctr)
    return aes.encrypt(zlib.compress(data))

class ProblemHandler(SocketServer.StreamRequestHandler):
    def handle(self):
        nonce = os.urandom(8)
        self.wfile.write(nonce)
        ctr = Counter.new(64, prefix=nonce)
        while True:
            data = self.rfile.read(4)
            if not data:
                break

            try:
                length = struct.unpack('I', data)[0]
                if length > (1<<20):
                    break
                data = self.rfile.read(length)
                data += PROBLEM_KEY
                ciphertext = encrypt(data, ctr)
                self.wfile.write(struct.pack('I', len(ciphertext)))
                self.wfile.write(ciphertext)
            except:
                break

class ReusableTCPServer(SocketServer.ForkingMixIn, SocketServer.TCPServer):
    allow_reuse_address = True

if __name__ == '__main__':
    HOST = '0.0.0.0'
    PORT = 4433
    SocketServer.TCPServer.allow_reuse_address = True
    server = ReusableTCPServer((HOST, PORT), ProblemHandler)
    server.serve_forever()

The key on this challenge is to see that the stream encryption is being done on the compressed input. In the source provided, if the user input is similar to the secret value in the PROBLEM_DATA variable then the zlib.compress() function would show a reduced length ciphertext. This is somewhat (and I use the term loosely) similar to the CRIME vulnerability. The AES Counter mode RFC has the implementation details of the cipher. So I wrote the following script.

import socket
import sys
from itertools import *
import struct
def display(msg,numbytes):
	#print >>sys.stderr, 'received "%s"' % msg
	#print >>sys.stderr, 'bytes "%d"' % numbytes
	print >>sys.stderr, 'bytes %d ' % numbytes + msg.encode('hex')
# Create a TCP/IP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# Connect the socket to the port where the server is listening
server_address = ('54.234.224.216', 4433)
print >>sys.stderr, 'connecting to %s port %s' % server_address
sock.connect(server_address)
#mesage len = 20 lowercase and underscore letters
try:
	amount_received = 0
	nonce = sock.recv(8)
	amount_received += len(nonce)
	# Send data
	#strng = 'crime_some'
	#minciphlen = 1000
	#strng = 'crimes_pays'
	#strng = 'so_'
	#strng = 'crime_some_times_pays'
	#strng = 'somet_'
	strng = 'cr'
	minchar = ''
	ciphlen = 1000
	sampleset = 'hijklmnopqrstuvwxyz_abdefgc'
	#while True:
	strng = strng + minchar	
	minciphlen = ciphlen
	minchar = ''
	for s in map("".join,permutations(sampleset,1)):
		#message = nonce +  (strng + s)*10  #'\x00'*11 + s
		message = strng + s
		datalen = struct.pack('I',len(message))  # datalen = '\xe4\x00\x00\x00'
		sock.sendall(datalen)
		#print >>sys.stderr, 'sending '+ message
		sock.sendall(message)
		#print >>sys.stderr, 'message sent'
		amount_received = 0
		# Look for the response
		data = sock.recv(4)
		amount_received += len(data)
		ciphlen = struct.unpack('I', data)[0]
		#print >>sys.stderr, message + ' ' 
		amount_received = 0
		if ciphlen <= minciphlen:
			minciphlen = ciphlen
			minchar = s
			print str(ciphlen) + ' It is ' + strng + minchar
		data = sock.recv(ciphlen)
		#display(data,ciphlen)		
finally:
    print >>sys.stderr, 'closing socket'
    sock.close()

When you connect to the service it provides you the nonce, so I prepended the nonce to the plaintext. The above script shows the plaintext and the length of the cipher text. To start off with this, you start with a string of length 1, and see which is the smallest length response, that gives your first character. Then in the

strng

variable above, you add that character and run again, and the lowest length ciphertext tells you the next character and so on. I noticed that sometimes the output had a few characters with the lowest length. So I tried each of them and ended up with the following flag:

crime_sometimes_pays