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flat assembler > Windows > CryptProtectData Problem

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jochenvnltn



Joined: 15 Jul 2011
Posts: 68

CryptProtectData Problem

Hello Everyone Smile

Im trying out the CryptProtectData API to encrypt a password.
The problem is that nothing is encrypted while the function itself returns ERROR_SUCCESS.

Here's my code:


Code:

include 'win32ax.inc'
entry main

szData db $43,$00,$68,$00,$61,$00,$6e,$00,$67,$00,$65,$00,$00,$00,$00,$00

DataSize = $ - szData



main:

     mov [datain.pbData], szData
     mov [datain.cbData], DataSize

     invoke CryptProtectDatadatain00000dataout
     ;//invoke CryptUnprotectData , datain, 0, 0, 0, 0, 0, dataout

     call CheckError

     cinvoke wsprintfW,buf,PASS,dataout;[dataout.pbData]
     invoke MessageBoxW,0,buf,cap,MB_OK

exitinvoke ExitProcess,0


proc CheckError
     mov eax, [fs:18h]
     mov eax, [eax+34h;GetLastError alternative
     invoke FormatMessage,FORMAT_MESSAGE_FROM_SYSTEM+FORMAT_MESSAGE_ALLOCATE_BUFFER,0,eax,0,error_buffer,0,0
     invoke MessageBox,0,[error_buffer],'error',MB_OK
     ret
endp

 error_buffer dd ?

section '.data' data readable writeable

 struct DATA_BLOB
    cbData   dd ?
    pbData   dd ?
   ends
     
 datain      DATA_BLOB
 dataout     DATA_BLOB

 cap      du 'Result',0
 PASS     du 'Pass:  %s',10,13,0
 buf      du  64  dup (?)

section '.idata' import data readable writeable

  library kernel32,'KERNEL32.DLL',\
          user32,'USER32.DLL',\
          Crypt32'Crypt32.dll'

  import Crypt32,\
                   CryptUnprotectData'CryptUnprotectData',\
                   CryptProtectData,'CryptProtectData'

  include 'api\kernel32.inc'
  include 'api\user32.inc' 


Post 09 Jun 2018, 19:40
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DimonSoft



Joined: 03 Mar 2010
Posts: 242
Location: Belarus

Re: CryptProtectData Problem

What do you expect to see and what makes you think nothing is encrypted? Seeing that you try to output the result by wsprintfW with %s placeholder I feel you don’t really understand what you get as the result of the encryption.
Post 09 Jun 2018, 21:42
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jochenvnltn



Joined: 15 Jul 2011
Posts: 68

Re: CryptProtectData Problem


DimonSoft wrote:
What do you expect to see and what makes you think nothing is encrypted? Seeing that you try to output the result by wsprintfW with %s placeholder I feel you don’t really understand what you get as the result of the encryption.



%s outputs it as a string. You can read about it here --> https://msdn.microsoft.com/en-us/library/windows/desktop/ms647550(v=vs.85).aspx
Post 09 Jun 2018, 22:04
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Walter



Joined: 26 Jan 2013
Posts: 127

This seems to work ok.


Code:
include 'win32ax.inc' 
entry main 

szData db 'paSS94wordGoesHere!',0
DataSize = $ - szData

main

     mov [datain.pbData], szData
     mov [datain.cbData], DataSize

     invoke CryptProtectDatadatain00000dataout 
     cinvoke wsprintf,buf,PASS,[dataout.pbData]
     invoke MessageBox,0,buf,cap,MB_OK

     invoke CryptUnprotectDatadataout00000datain
     cinvoke wsprintf,buf,PASS,[datain.pbData]
     invoke MessageBox,0,buf,cap,MB_OK

     invoke ExitProcess,0

section '.data' data readable writeable

 struct DATA_BLOB 
    cbData   dd ? 
    pbData   dd ? 
   ends 
      
 datain      DATA_BLOB 
 dataout     DATA_BLOB 

 cap      db 'Result',0
 PASS     db 'Pass:  %s',10,13,0
 buf      db  64  dup (?)

section '.idata' import data readable writeable 

  library kernel32,'KERNEL32.DLL',\ 
          user32,'USER32.DLL',\ 
          Crypt32'Crypt32.dll' 

  import Crypt32,\ 
                   CryptUnprotectData'CryptUnprotectData',\ 
                   CryptProtectData,'CryptProtectData' 

  include 'api\kernel32.inc' 
  include 'api\user32.inc'  

Post 09 Jun 2018, 23:01
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 15814
Location: Misner space

I'm not sure that passwords should ever be encrypted unless you are storing them in a password vault. For most other uses they should be hashed with a salt.
Post 10 Jun 2018, 02:01
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DimonSoft



Joined: 03 Mar 2010
Posts: 242
Location: Belarus

Re: CryptProtectData Problem


jochenvnltn wrote:

DimonSoft wrote:
What do you expect to see and what makes you think nothing is encrypted? Seeing that you try to output the result by wsprintfW with %s placeholder I feel you don’t really understand what you get as the result of the encryption.



%s outputs it as a string. You can read about it here --> https://msdn.microsoft.com/en-us/library/windows/desktop/ms647550(v=vs.85).aspx


I do know what %s does. Everyone knows. There’s absolutely no sense in using it with arrays of bytes (which is what you get after encryption).

Your code works as expected and encrypts original message. And if you want to talk about reading documentation, you’d better follow this link and then (1) add LocalFree to your code and (2) stop calling GetLastError unless the function returns FALSE. Both are not necessary to get the encrypted string but should be kept in mind if you’re going to transform your code into something larger.
Post 10 Jun 2018, 07:06
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jochenvnltn



Joined: 15 Jul 2011
Posts: 68


Walter wrote:
This seems to work ok.


Code:
include 'win32ax.inc' 
entry main 

szData db 'paSS94wordGoesHere!',0
DataSize = $ - szData

main

     mov [datain.pbData], szData
     mov [datain.cbData], DataSize

     invoke CryptProtectDatadatain00000dataout 
     cinvoke wsprintf,buf,PASS,[dataout.pbData]
     invoke MessageBox,0,buf,cap,MB_OK

     invoke CryptUnprotectDatadataout00000datain
     cinvoke wsprintf,buf,PASS,[datain.pbData]
     invoke MessageBox,0,buf,cap,MB_OK

     invoke ExitProcess,0

section '.data' data readable writeable

 struct DATA_BLOB 
    cbData   dd ? 
    pbData   dd ? 
   ends 
      
 datain      DATA_BLOB 
 dataout     DATA_BLOB 

 cap      db 'Result',0
 PASS     db 'Pass:  %s',10,13,0
 buf      db  64  dup (?)

section '.idata' import data readable writeable 

  library kernel32,'KERNEL32.DLL',\ 
          user32,'USER32.DLL',\ 
          Crypt32'Crypt32.dll' 

  import Crypt32,\ 
                   CryptUnprotectData'CryptUnprotectData',\ 
                   CryptProtectData,'CryptProtectData' 

  include 'api\kernel32.inc' 
  include 'api\user32.inc'  




Thank you Walter ! You helped me out allot! thx Wink
Post 10 Jun 2018, 12:05
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