Jump to content
Tuts 4 You

DNGuard HVM v3.953


Mohd
Go to solution Solved by BlackHat,

Recommended Posts

Since the challenge description allows it, I'm going for the quick serial fish for now :)

Spoiler

Secret Key: AWX610881RFFJSDJSZV
URL: http://localhost:52735/
Vendor: Fadi Sami Khalid
Address: Jordan - Amman - Khalda

Approach:

Spoiler

Obfuscation does not really matter if your methods are just simple string comparisons. The x86 generated by the JIT compiler still reveals everything ;)

  • Run app, enter random stuff in textboxes, press Validate to trigger the JIT compiler to compile the validation method. Notice text of the label changes to Not Correct.
  • Attach WinDbg, set breakpoint on Control.set_Text (use !name2ee System.Windows.Forms.dll System.Windows.Control.set_Text to get the address to breakpoint). Continue execution and press Validate again.
  • Type !clrstack to notice the click handler is in Form1._01.01.  Copy the address of the handler and dump the x86 code using !U <address>. (dump here https://pastebin.com/br3s09Gv)
  • Notice in x86 code its just a bunch of string.Equals calls. Set a breakpoint on all string.Equals(string, string) calls in the method. Continue execution and press Validate one more time again.
  • Use !dumpstackobjects to read out the correct values for every one of these calls.

 

Edited by Washi
  • Like 2
  • Thanks 2
Link to comment
  • 3 months later...
5 hours ago, GautamGreat said:

I would love to have some information about hooking Jit

just dm me sir 

  • Like 1
  • Confused 1
Link to comment
  • 7 months later...
  • Solution
BlackHat

How to Unpack ?

Spoiler
  1. You need to Hook the JIT Code at Runtime by executing the file.
  2. Now Detect the Method Bodies in JIT and Read it with .Net Libraries, Your main work is to restore the value of Instructions but Here is a catch that Method Tokens are encrypted/locked in HVM Version.
  3. You need to Analyze and understand the Runtime.dll to Restore the value.
  4. You can Restore the Original and Remove proxy by analyzing the methods after devirting.
  5. Strings are also encrypted but just Invoke static string methods in "ZYXDNGuarder" and restore those with Original Value.

Decrypt HVM Token and the Offset Value of HVM Table --> Parse their Structure Schema and Read HVM Table

At Last Read Methods after detecting those and append in your Main Assembly.

 

Solution -

Spoiler

2021-08-28_21-00-45.png.13e4bef0f9a50383707af98f5ce25525.png

 

3.9.5.3.zip

  • Like 2
Link to comment
  • 4 weeks later...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...