C / C++ / MFC

Re: How to access application's extern variable inside a dll

15-Dec-11 19:57

I have an application which has several extern variables, I need to access them inside dll. Is that possible?

modified 16-Dec-11 2:58am.

CPallini15-Dec-11 21:32

CPallini

15-Dec-11 21:32

You may, for instance, pass them (their pointers or references) as parameters of a DLL function.

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-- Alfonso the Wise, 13th Century King of Castile.

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Re: How to access application's extern variable inside a dll

rahul.kulshreshtha16-Dec-11 3:51

Re: How to access application's extern variable inside a dll

16-Dec-11 3:51

Thanks,

I agree the way you are saying is right and genuine. But unfortunately I don't have exe's source code Smile | :)

I have injected a dll into exe's process space and now want to get the data from exe's memory space. I tried with hooking the system level functions like LoadLibrary and TextOut etc but I could not hook GetProfileInt, CString's sprintf, format etc functions.

Any way to do so ?

I wonder who downvoted my question Big Grin | :-D

CPallini16-Dec-11 5:27

CPallini

16-Dec-11 5:27

So you're an hacker?! Big Grin | :-D

I upvoted your question for balancing.

Re: How to access application's extern variable inside a dll

rahul.kulshreshtha16-Dec-11 5:46

Re: How to access application's extern variable inside a dll

16-Dec-11 5:46

Nopes! I am not; but I like to explore the things at extreme level $Shucks | :-\$

Erudite_Eric16-Dec-11 0:40

Erudite_Eric

16-Dec-11 0:40

Use a shared header externing the variable in the dll. Include this in the exe, and then the linker will do the rest for you.

==============================

Nothing to say.

Re: How to access application's extern variable inside a dll

rahul.kulshreshtha16-Dec-11 3:53

Re: How to access application's extern variable inside a dll

16-Dec-11 3:53

Thanks Eric,

But I don't have exe's code. See my above reply for more details.

C^hris L^osinger16-Dec-11 4:16

C^hris L^osinger

16-Dec-11 4:16

you can access extern (and exported) variables in a DLL from an EXE.
you cannot access variables in an EXE from a DLL.

you could, in theory, decompile the EXE, find the references to the data you want, figure out if the data is statically or dynamically allocated, then create some mechanism to probe the EXE's memory at the right locations and times, etc.. a huge task.

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Re: How to access application's extern variable inside a dll

rahul.kulshreshtha16-Dec-11 5:22

Re: How to access application's extern variable inside a dll

16-Dec-11 5:22

Thanks Chris for verifying that I cannot access variables in an EXE from a DLL directly.
So I am doing the Huge task. Still I think hooking should work as it is working for few of the functions; I will try a little more before leaving hooks.

Richard MacCutchan16-Dec-11 7:04

Re: How to access application's extern variable inside a dll

16-Dec-11 7:04

This is largely a waste of time as there is nothing in the executable file that would get you a reference to the location of the variables. The use of extern on a variable declaration merely tells the compiler that it exists in a different source module. Such references are then resolved by the linker but no more information about them is held in the EXE file.

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

C^hris L^osinger16-Dec-11 8:03

C^hris L^osinger

16-Dec-11 8:03

that's true.

i suppose i left out the "...in a debugger..." part.

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Re: How to access application's extern variable inside a dll

Richard MacCutchan16-Dec-11 22:42

Which function can I use instead of ShowControlBar

16-Dec-11 22:42

What you wrote looked fine to me; I just think the OP read more into it than you intended.

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

adityarao3115-Dec-11 19:42

adityarao31

15-Dec-11 19:42

I am getting error at following line of code

ShowControlBar(&m_wndColorBar, !m_wndColorBar.IsVisible(), FALSE);

the error is
error C2664: 'CFrameWnd::ShowControlBar' : cannot convert parameter 1 from 'CMFCToolBar *' to 'CControlBar *'

I understand the error is due to m_wndColorBar is a variable of
CToolBar ,but of CMFCToolbar. Please guide me which function can I use instead of ShowControlBar

Be Happy

Re: Which function can I use instead of ShowControlBar

Resmi Anna15-Dec-11 21:45

Resmi Anna

15-Dec-11 21:45

It seems m_wndColorBar is a variable of type CMFCToolBar not CToolBar. Can you check what is the base class of CMFCToolbar??. It is supposed to be a child of CToolBar. But seems it is not Unsure | :~

DES Encryption

jkirkerx15-Dec-11 19:12

15-Dec-11 19:12

I don't understand why I can do CryptCreateHash with CALG_MD5 no problem, but when I use CALG_DES, It fails.

I want just the Basic DES Encryption, using a pair of keys. I suspect that I have the wrong CryptAcquireContext Statement, in which I may be calling the wrong service, but I can't find any reference other than PROV_RS_FULL. I did some research and I'll swear that the DES is a member of the MS_STRONG_PROV.

My Goal is to replicate a function in asp.net to c++

bResult = CryptAcquireContextW( &hProv, 0, MS_STRONG_PROV, PROV_RSA_FULL, 0);
    if(!bResult){
        bResult=CryptAcquireContext(&hProv, NULL, MS_STRONG_PROV, PROV_RSA_FULL, CRYPT_NEWKEYSET);
        return 0;
    }
    bResult = CryptCreateHash(hProv, CALG_DES, 0, 0, &hHash);

asp.net function:

Dim cryptoProvider As DESCryptoServiceProvider = New DESCryptoServiceProvider()
            Dim ms As MemoryStream = New MemoryStream()
            Dim cs As CryptoStream = New CryptoStream(ms, cryptoProvider.CreateEncryptor(KEY_64, IV_64), _
            CryptoStreamMode.Write)
            Dim sw As StreamWriter = New StreamWriter(cs)

Code-o-mat15-Dec-11 22:20

Code-o-mat

15-Dec-11 22:20

Call GetLastError after using CryptCreateHash and see what the error is (and tell us). See this[^] or this[^] for error codes.

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> If it doesn't matter, it's antimatter.<

jkirkerx16-Dec-11 6:40

16-Dec-11 6:40

I should of done that last night, was really tired, this is my 4th time though the program.

The code is 2148073480
2148073480 NTE_BAD_ALGID: Invalid algorithm specified.

Code-o-mat16-Dec-11 7:01

Code-o-mat

16-Dec-11 7:01

Yeah, it happens... Smile | :)

anyways, i think Richard got the right answer.

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> If it doesn't matter, it's antimatter.<

Richard MacCutchan15-Dec-11 23:40

15-Dec-11 23:40

I just tried this and received error code 0x80090008 which means "Invalid algorithm specified", so I guess the implementation does not match the documentation.

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Richard MacCutchan16-Dec-11 1:16

16-Dec-11 1:16

My brain finally caught up ...
CALG_DES is an encryption algorithm, not a hash algorithm so cannot be used in a call to CryptCreateHash().

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

jkirkerx16-Dec-11 7:19

16-Dec-11 7:19

These 3 are qualified to support DES
Microsoft Base Cryptographic Provider v1.0 - DES
Microsoft Strong Cryptographic Provider v2.0 - 3DES
Microsoft Enhanced Cryptographic Provider v1.0 - 3DES

The page below list DES as a member of Microsoft Enhanced Cryptographic Provider

http://msdn.microsoft.com/en-us/library/windows/desktop/aa386986%28v=vs.85%29.aspx[^]

But on running MS_ENHANCED_PROV and calling CALG_DES to CreateHash
error 3435973836
NTE_BAD_UID

I'll do some more reading and get something to match.

Richard MacCutchan16-Dec-11 7:40

16-Dec-11 7:40

You missed something; read my comments again - carefully.

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Randor 16-Dec-11 7:59

Randor

16-Dec-11 7:59

Hi there,

What Richard is saying is that DES[^] is a block cipher encryption algorithm. The CryptCreateHash function[^] does not encrypt anything... it creates a hash of the data passed into the function.

Some wiki information about hash functions:
Cryptographic hash function[^].

If you want to use the DES algorithm then you will need to use the CryptEncrypt function[^] but there is a small learning curve when working with the Microsoft Cryptography Functions... providers, contexts, keys, key stores...

Acquiring a Cryptographic Context and Generating Keys[^]

If you are looking for a quick copy-and-paste code snippit then you might want to take a look at one of my ancient posts from the Mesozoic era: Re: decrypting question[^]

CPallini still had hair back then. $Shucks | :-\$

Best Wishes,
-David Delaune

jkirkerx16-Dec-11 8:12

16-Dec-11 8:12

I wrote the hash function first, and tried to reuse the parts of code to write the encryption function.

I never did understand why I still had hash stuff, but most of the documentation I could find for symmetrical ???, using key IV pair values pointed me in that direction.

So I need to start all over again with a stronger understanding of how it works.

I will read your links.

Thanks, will let you know what I cook up here on round 5.

jkirkerx16-Dec-11 9:00