Date: 24 May 2006 20:55:35 -0000
From: thesinoda@...mail.com
To: bugtraq@...urityfocus.com
Subject: A Nasty Security Bug that affect PGP Virtual Disks & PGP SDA ,
 PGP 8.x & 9.x and Truecrypt.


A Nasty Security Bug that affect PGP Virtual Disks & PGP SDA , PGP 8.x & 9.x and Truecrypt. 

Affected Products:

    * PGP 8.x PGP 9.x maybe older version too

    * Truecrypt 4.2 maybe older version too

// Full detail can be found here //
<> http://www.safehack.com/Advisory/pgp/PGPcrack.html
<> http://www.safehack.com/Advisory/truecrypt/truecrypt.html

If you would like to watch the flash video check the following links.
<> pgpdiskvideo.html Tested on version 8.1 and the latest 9.02
   http://www.safehack.com/Advisory/pgp/pgpdiskvideo.html

<> truecrypt.html Tested on the latest version truecrypt-4.2.zip
   http://www.safehack.com/Advisory/truecrypt/truecrypt.html
   Note If you put stuff inside your test file you need to use a 
   debugger to extract the data. If you just follow the video you 
   will see how it is done without a debugger and an empty file.

The How?
========
I Was able to ACCESS PGP encrypted disks if the disk was encrypted with a passphrase or a public Key. This method will work on both scary huh :-)

You need the followings tools:
------------------------------
   1. A Brain
   2. A Hex Editor.
   3. PGP 8.1 Entreprise or Personal. You can use 9.x too. My feeling is this method will work on older versions too, because it is a design flaw in PGP application not in PGP algorithm.
   4. A Debugger. Not needed if you wana backdoor pgp (olldbg)
   
During my tests I have found that PGP virtual DISK and PGP Self Extractable file SDA have a SERIOUS security bug. I would rather say a design bug.

PGP disk or SDA can be cracked in 3 major steps:
------------------------------------------------
   1. Editing PGP protected file using a hex editor. (Patching the passphrase).
   2. Tracing PGP protected file using a debugger. (You need a lot of time and coding/cracking experience)
   3. Patching the responsible bytes.

I have spend only couples of days debugging but surely a lot more time is needed. But once the process is understood it is question of finding the right bytes and patching them.

 
Conclusions for 6 days debugging and testing:
=============================================
    * PGP Virtual Disk and PGP and PGP SDA has a serious bug. I have tested PGP 8.1 Entreprise. Other version many be vulnerable too.

    * PGP corporation made the same error in PGP 9.x you can bypass the passphrase Dialog box same way.

    * PGP corporation could avoid this type of issue by calculation the HASH for the encrypted file. They should make it harder to locate the passphrase.

    * PGP Virtual Disk First Level protection bypass. Passphrase bypass. (Working 100%)

    * PGP Virtual Disk Backdooring (Working 100%).

    * PGP Virtual Disk Mounting / Adding Users / Deleting Users / Re-Encrypting Disk (Working 100%).

    * PGP Virtual Disk Mounting and Data Access (Working 40%. Need more time to debug).

    * PGP SDA Passphrase bypass. (Working 100%)

    * PGP SDA Extraction is possible IF the input file is the same (Working 100% Patching using a Debugger)

    * PGP SDA Extraction is possible of any file (Working 80%. Need more time to debug)

    * OTHER AFFECT PRODUCTS:
          o iOPUS Secure Email Attachments (SEA) V1.0
          o Truecrypt Free open-source disk encryption software 4.2

    * WINZIP was not affected. 1- In winzip you do not know where is the password location 2- If you change one bit your file wont work

    * I DO NOT HAVE more time to test, but I am sure many smart dudes out their would love to play some more.

    * To do: Build an application to mount PGP Virtual disk using this bug.

    * To do: Build an application to extract PGP SDA files using this bug.

After spending 6 days on this I had decided to stop. But I will be doing more testing when I have some free time. You are free to do your own tests. If you wish to share your own test or finding with me please feel free to contact me at thesinoda@...mail.com


 
PGP SDA authentication method
=============================
Let's say you created a text file and wrote inside it "aa", then created an SDA.
IF you hex edit the output exe, you will notice at the very buttom of the file some bytes seperated by 803E.
Ex:

E7 93 A0 90 E9 62 D1 21
803E
A1 50 AF 5F 6F 9E FE D6

Analysing the bytes carefully, you will notice that 803E is the value used for a loop. The loop starts at 0040590D. Further analysis showed that the bytes right before 803E, are used for extraction and authentication. Authentication is done in the following way:

When some enters a passphrase a series of instructions is executed against the bytes right before 803E, to be exact in the function at address 00404E8F. This function generates a series of bytes which are compared later on to the bytes AFTER 803E. If they match you are granted auth.

The auth. byte comarison is done in the following instruction:
00409797 |. F3:A7 REPE CMPS DWORD PTR ES:[EDI],DWORD PTR DS:[ESI]
Anyone can easily bypass this by modifying the values provided by the memory addresses, to make them match.


Steps to access PGP Encrypted Disk (Passphrase) using a Backdoor type attack
============================================================================
    * Create a PGP disk 100K (to make stuff simpler)
    * Use a as username and 1 as passphrase for simplicity
    * Call your file pgpdisk.pgd
    * Now your disk will be created and mounted. Put a inside it (secret.txt) then Unmount the disk (pgpdisk.pgd)
    * Make a Back-up copy call it pgpdisk_backup.pgd (You need this when you want to access back the disk)
    * Now say you give that disk to someone and they changed the passphrase on it. You can still access it if you follow these steps
    * To put a new passphrase on your disk Right click pgpdisk.pgd you see PGP select Edit PGPdisk
    * You see a username, right click it and select change passphrase. Use WHATEVER PASSPHRASE YOU WANT
    * After changing the passphrase the OLD passphrase SHOULD NOT work.
    * Open pgpdisk.pgd and pgpdisk_backup.pgd in HEX editor e.g Ultraedit ONLY CHANGE WHERE YOU SEE A RED RECTANGULAR.
    * We start editing from the BOTTOM of the file at 80 3E.
    * Do some copy and past from the back-up file into pgpdisk.pgd
    * Follow the screen shots and replace indicated bits.
    * After your done save the file pgpdisk.pgd and double click on it. It will ask for the passphrase. Type 1 yes your old pass
    * The disk will mount and you see the files in it.

 
// Full detail can be found here //
<> http://www.safehack.com/Advisory/pgp/PGPcrack.html
<> http://www.safehack.com/advisory/truecrypt/truecrypt.html



LESSON LEARNED, this advisory should be a wakeup call for other products. Again as you see both commercial an OpenProject applications are affected by this. This should be more then enough to kill the Open<>close project myth and concentrate on secure coding and GOOD AUDIT.


Author: Adonis a.K.a NtWaK0, Abed
Date: 2006-05-08
© 2006 All rights reserved

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