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Overflowz



Joined: 03 Sep 2010
Posts: 1046
Overflowz
Hello everyone! I'm interested how can I lock files to deny acces on it from users ? For example I have file called "file.doc" and user tries to open it, but it says "Error access denied" or something like that..
I need to deny access on read, write and copy.. So, people can't even touch it.. Thank you and sorry for my poor English..
Post 27 Jun 2011, 12:45
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
You really should start doing something proper, working on malware isn't very respectable.
Post 27 Jun 2011, 12:56
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Overflowz



Joined: 03 Sep 2010
Posts: 1046
Overflowz
Why you're saying that ? Smile I'm working how to lock opera's "wand.dat" so, malwares can't grab it.. I'm working for anti-malware things.. I don't understand what I'm saying wrong..
Post 27 Jun 2011, 19:26
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bitshifter



Joined: 04 Dec 2007
Posts: 764
Location: Massachusetts, USA
bitshifter
http://msdn.microsoft.com/en-us/library/aa364399(v=VS.85).aspx

How i get the link to display properly?
Post 27 Jun 2011, 20:14
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Overflowz



Joined: 03 Sep 2010
Posts: 1046
Overflowz
bitshifter
I tried that already, CreateFile with dwShare value of NULL. but I was still able to read,write and copy.. I don't know what's problem, it works with another files but not with EXACT that file..
Post 27 Jun 2011, 20:26
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
Quote:
How i get the link to display properly?

Use some link shortener, eg. goo.gl
Post 27 Jun 2011, 20:36
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typedef



Joined: 25 Jul 2010
Posts: 2913
Location: 0x77760000
typedef
Overflowz wrote:
Hello everyone! I'm interested how can I lock files to deny acces on it from users ? For example I have file called "file.doc" and user tries to open it, but it says "Error access denied" or something like that..
I need to deny access on read, write and copy.. So, people can't even touch it.. Thank you and sorry for my poor English..


Encrypt the file.... Wink Wink

From 0 to it's end.

If you use MS file security stuff, they can be changed again.

The drawback is, if the file is a system file, then you are f**d.
Post 27 Jun 2011, 21:36
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garystampa



Joined: 25 May 2011
Posts: 52
Location: Central FLorida
garystampa
You're not going to be able to do that exactly like you're wanting.

Typedef's reply is the only sure way to protect a file from viewing. But there's no way to keep it from being edited - even if they don't know what they're editing.
Post 27 Jun 2011, 21:45
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Overflowz



Joined: 03 Sep 2010
Posts: 1046
Overflowz
If I'll encrypt it, than opera won't perceive it as valid file.. How about SAM file which is located at C:\Windows\System32\config ? It says always access denied when I'm copying, moving or editing it.. It's driver file job ?
Post 27 Jun 2011, 22:14
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typedef



Joined: 25 Jul 2010
Posts: 2913
Location: 0x77760000
typedef
Overflowz wrote:
If I'll encrypt it, than opera won't perceive it as valid file.. How about SAM file which is located at C:\Windows\System32\config ? It says always access denied when I'm copying, moving or editing it.. It's driver file job ?


Only the system can view that file. It uses Windows File Security to stop you from messing with it.

If you want the file encrypted by you and that you also want the system to be able to read it, then I suggest you go with hooking. Inject your code before the system loads the file then decrypt it and jump to the code where the system reads it.

But that's another story.
Post 28 Jun 2011, 00:12
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typedef



Joined: 25 Jul 2010
Posts: 2913
Location: 0x77760000
typedef
Here's a simple start.
Make sure you have a file named file.txt

Code:
format pe gui 4.0

include 'win32ax.inc'

entry main

section '.txt' code executable readable writeable
w dd 0
db 'Read a file for encrypting',0
db  11111111b dup(0),0
db  'file.txt',0
proc main
     pushad
     push 0
     push $-100001100b;Not used for now
     push $-100101100b;
     push 0
     call [MessageBox]
     push 0
     push FILE_ATTRIBUTE_NORMAL
     push OPEN_EXISTING
     push 0
     push FILE_SHARE_READ
     push GENERIC_READ
     push $-110000b
     call [CreateFile]
     push eax
     push 0
     push w
     push 11111111b
     push $-101001000b
     push eax
     call [ReadFile]
     pop  eax
     push eax
     call [CloseHandle]
     ;
     ; Encrypt data here, ie using XOR,etc
     ;
     push MB_OK+MB_ICONINFORMATION
     push $+10100b
     push $-101100011b
     push 0
     call [MessageBox]
     popad
     ret
endp
     db 'Text read from file',0
section '.idata' import data readable

library user32,'user32.dll',kernel32,'kernel32.dll'
include 'api/user32.inc'
include 'api/kernel32.inc'
    
Post 28 Jun 2011, 00:53
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Overflowz



Joined: 03 Sep 2010
Posts: 1046
Overflowz
Dude... I know how to encrypt file but I told already, It won't work if I'll crypt it.. If there is no other ways then I'll try to think myself. Thank you all.
Post 28 Jun 2011, 07:22
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s0rg



Joined: 05 Aug 2008
Posts: 1
s0rg
Post 28 Jun 2011, 12:13
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Overflowz



Joined: 03 Sep 2010
Posts: 1046
Overflowz
s0rg
Wow! I don't knew that! I'll try, thank you very much! Smile
Post 28 Jun 2011, 12:46
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garystampa



Joined: 25 May 2011
Posts: 52
Location: Central FLorida
garystampa
Locking the file is temporary. What you want to do is take complete ownership of the file so no one but your app can read it, right?

The problem is that if a program can set restrictions there is always going to be another program that can undo them. Knowledgeable programmers or power users know how to lift any restriction on a file.

Therefore, encryption is the only way. As typedef describes you need to set up a registry entry to take association of the file extension and have Windows consult you whenever someone clicks the file. You can then decrypt it on-the-fly on request. If it's not one of your files, pass it thru untouched.
Post 28 Jun 2011, 14:50
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Overflowz



Joined: 03 Sep 2010
Posts: 1046
Overflowz
Thanks, I'll try that if there's no way ))
Post 28 Jun 2011, 19:33
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