Re: DPAPI implemented in Crypt32.dll
From: Alan Croston (anonymous_at_discussions.microsoft.com)
Date: 02/27/04
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Date: Fri, 27 Feb 2004 01:43:10 -0800
I just re-read that and yes, it's amusing. I downloaded
it off a code site as a VB class and compiled it as an
active x dll. This all works fine on XP, but not on 2000.
I even combined the class into my VB app so there was no
activex dll and I could debug easier. DPAPI fails when I
call CryptProtectData or CryptUnprotectData passing in
Blobs (binary large objects) greater than 300k in size
into those functions and so the problem canNOT be at the
ActiveX dll level. I am very certain it is because DPAPI
is breaking and not my code.
Can you enlighten me as to what might be going on?
Thanks and Regards
Alan Croston
>-----Original Message-----
>"via a COM object I obtained"
>Aha! I had to re-read that post a couple of times until
I saw that.
>
>The DPAPI API for encrypting data is CryptProtectData.
For decrypting, it's
>CryptUnprotectData. The COM object must be calling
those if it's using
>DPAPI.
>
>If you call a COM object and fail with an RPC error,
wouldn't you suspect
>that the COM object has a bug? COM implies RPC . . .
>
>
>Also: You probably don't want to copy binaries from an
XP install to a Win2k
>one. While an app might work ok, it's really unlikely
that a system dll
>will work on a downlevel platform.
>--
>Drew Cooper [MSFT]
>This posting is provided "AS IS" with no warranties, and
confers no rights.
>
>
>"Alan Croston" <anonymous@discussions.microsoft.com>
wrote in message
>news:270c01c3fc7e$d0c2ebe0$a301280a@phx.gbl...
>> Greetings all,
>>
>> This is fun (I had hair when I discovered this
yesterday,
>> none today!)
>>
>> I have implemented a file encryption solution using
>> windows XP. this uses DPAPI and calls it via a COM
object
>> I obtained. I then make calls to this COM object like
>> Encrypt(blob, filepath) and Decrypt(filepath,
filename).
>>
>> This works great on windows xp. I have tested
encryption
>> on files up to 120 MB. I can also decrypt these files
>> (Very useful lol!)
>>
>> However, i moved the code onto windows 2000 server and
>> the call to the Crypt32.dll fails with "Automation
Error:
>> Remote Procedure Call Failed". It only does this when I
>> try to encrypt files over about 300 kbytes. Anything
less
>> than 300 kbytes works great! Why does it fail when it
>> works fine on xp?
>>
>> I have checked the versions of the dlls and XP has a
>> later (larger in size) version of the Crypt32.dll, so
>> obviously there were changes between 2000 and XP
possibly
>> impacting the implementation of the DP API.
>>
>> 2000 version 5.131.2195.6661 (Supplied with 2000 SP4)
>> XP version 5.131.2600.1106 (Supplied with XP SP1)
>>
>> I have checked my code and produced versions that allow
>> me to debug right up to the point where the DPAPI
method
>> Encrypt / Decrypt is called from my Visual Basic 6
code.
>> The method is called... there is a pause... and the
when
>> I get the err.getLastDLLError I get the RPC failed
>> message. So I am 99.999% sure that the version of
Crypt32
>> is to blame.
>>
>> Can anyone tell me what is happening? Is there any way
>> that I can get around this problem e.g. coping the
>> Crypt32.dll over from XP to 2000? Will that work? Can I
>> upgrade the 2000 Crypt32 dll?
>>
>> The really frustrating thing is that there is hardly
any
>> info on DPAPI on the internet at all and even less of
>> Crypt32.dll problems. Surely I cannot be the only
person
>> on the planet using DPAPI to encrypt / decrypt files!!!
>> (Knowing my current luck I am! lol)
>>
>> Anyway, something for you guys to ponder over if you
get
>> the chance. I would appreciate anyones info that may
help
>> me to resolve this!
>>
>> Thanks in anticipation
>>
>> Regards
>>
>> Alan Croston
>>
>>
>>
>>
>
>
>.
>
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