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RE: [Dazuko-devel] dazuko and External AV

From: Tikka, Sami
Subject: RE: [Dazuko-devel] dazuko and External AV
Date: Mon, 25 Feb 2008 14:53:24 +0200

> -----Original Message-----
> From: address@hidden 
> [mailto:address@hidden
g] On Behalf Of Saurabh Suman

> I am trying to configure my anti-virus with dazuko-2.3.4 for 
> real time scanning. The problem is, I am using external 
> anti-virus engine.
> I have to get access to file from dazuko using GetAccess then 
> I send the filename to my av engine's Socket to scan.
> As dazuko has already locked the access to file and scanner 
> tries to scan before returning access, my av scanner hangs as 
> it can not open file to scan.
> Can anyone suggest me the better way to approach the solution?

Dazuko does not lock the file in any way.

You problem probably is that your dazuko application is single-threaded and
the sequence of events is like this:

Application A opens file F -> dazuko intercepts and sends message to Dazuko
application -> Dazuko application sends scan request to external anti-virus
application -> external anti-virus application opens the file F -> dazuko
intercepts and tries to send message to Dazuko application, but it is busy
waiting for reply from external anti-virus application -> dazuko puts
external anti-virus application to sleep waiting for Dazuko application to
call dazukoGetAccess (but that never happens because it waiting for the
external anti-virus application)

=> the system is deadlocked. ("Been there, done that, got the lowsy t-shirt"

There are two ways around this:

1) You can make dazuko application have more than 1 thread or processes. When
dazuko application sees a file is being opened by the external anti-virus
application, it should immediately allow the access. You should have many
threads/processes just in case there are many simultaneous file accesses in
your system. If ever there is a situation when there are no idle dazuko
application threads/processes when the external anti-virus application opens
a file, a deadlock will happen.

2) Better way is to have your external anti-virus application register to
dazuko as a trusted application. This way dazuko will never intercept file
accesses from the external anti-virus application. See "README.trusted" in
dazuko sources.

Basically, this can all be summarized: You should make sure your dazuko
application is always reponsive.

-- Sami

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