DNGuard HVM v3.953

[Mohd 1]

View File

DNGuard HVM

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Try to unpack or alternatively provide the secret key, URL, Name and Address 

Protections used:

DNGuard Enterprice HVM 3.953

 

Good luck.

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• Submitter
  Mohd
• Submitted
  09/08/2020
• Category
  UnPackMe (.NET)

 

[Washi 89]

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 September 9 by Washi (see edit history)

[AzoresRCE 2]

I would just like to point out that this is DNGuard Enterprise HVM 3.9.5.1 not 3.9.5.3

Edited September 10 by AzoresRCE (see edit history)