Re: Integration of qemu-img

Re: Integration of qemu-img

[Markus Armbruster]

Cc: qemu-block

<janine.schneider@fau.de> writes:

> Dear Sir or Madam,
>
>  
>
> I am a PhD student at the Friedrich-Alexander-University Erlangen-Nürnberg
> in Bavaria Germany and I am currently working on an open-source forensic
> analysis tool. I would like to use qemu-img for converting virtual discs to
> raw files and to get virtual disc information. By now I tried to create a
> qemu-img DLL with the qemu source code you provide on your website, but I am
> unable to compile it properly. Therefore, I would like to ask you if there
> is a simple solution to integrate qemu-img to other C++ projects? Or is
> there a precompiled qemu-img DLL which I could use? Thank you very much for
> your support.
>
>  
>
> Best,
>
> Janine Schneider
>
>  

Re: Integration of qemu-img

[Stefan Hajnoczi]

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On Thu, Apr 16, 2020 at 09:50:48AM +0200, Markus Armbruster wrote:
> Cc: qemu-block
> 
> <janine.schneider@fau.de> writes:
> 
> > Dear Sir or Madam,
> >
> >  
> >
> > I am a PhD student at the Friedrich-Alexander-University Erlangen-Nürnberg
> > in Bavaria Germany and I am currently working on an open-source forensic
> > analysis tool. I would like to use qemu-img for converting virtual discs to
> > raw files and to get virtual disc information. By now I tried to create a
> > qemu-img DLL with the qemu source code you provide on your website, but I am
> > unable to compile it properly. Therefore, I would like to ask you if there
> > is a simple solution to integrate qemu-img to other C++ projects? Or is
> > there a precompiled qemu-img DLL which I could use? Thank you very much for
> > your support.

Can you simply spawn a qemu-img process from your application?  That
would be much easier than trying to build it as a library and link it
into your application.

qemu-img has --output=json exactly for this case.  It will let you parse
the output as JSON.

Stefan

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Re: Integration of qemu-img

[Stefan Hajnoczi]

On Thu, Apr 23, 2020 at 11:20 AM <janine.schneider@fau.de> wrote:
> this requires the user of the application to install qemu first right?
> If this is the case then this is unfortunately not an option. The user shall
> not be bothered with installing anything else then the tool.

Hi Janine,
Please use Reply-All to keep the email CC list in tact.  That way
qemu-devel@nongnu.org will receive our replies and the discussion will
stay on the mailing list.  Thanks!

It's common for applications to consist of more than a single
executable file.  They could have shared libraries, data files, or
other executables like qemu-img.exe.  You can distribute qemu-img.exe
together with your application as part of a zip file or installer.

Regardless of whether you ship qemu-img.exe or build a library, please
check QEMU's software license so that you can follow the terms of the
GPL open source license.

Stefan

AW: Integration of qemu-img

[janine.schneider]

Hy again,

okay so now we have an easy way out just in case.
But I still want to build an DLL and/or a shared library for integration into the tool. I want the tool to be platform independent and I was already able to build qemu-img as cross build with mingw64. Does anybody have experience in building a qemu library or tried it already?
The tool I want to integrate qemu in is published under GPL itself. And if I am able to build qemu as library I will share it with the community and everybody interested in having it.

Best,
Janine

-----Ursprüngliche Nachricht-----
Von: Stefan Hajnoczi <stefanha@gmail.com> 
Gesendet: Donnerstag, 23. April 2020 12:41
An: janine.schneider@fau.de
Cc: qemu-devel <qemu-devel@nongnu.org>; qemu block <qemu-block@nongnu.org>
Betreff: Re: Integration of qemu-img

On Thu, Apr 23, 2020 at 11:20 AM <janine.schneider@fau.de> wrote:
> this requires the user of the application to install qemu first right?
> If this is the case then this is unfortunately not an option. The user 
> shall not be bothered with installing anything else then the tool.

Hi Janine,
Please use Reply-All to keep the email CC list in tact.  That way qemu-devel@nongnu.org will receive our replies and the discussion will stay on the mailing list.  Thanks!

It's common for applications to consist of more than a single executable file.  They could have shared libraries, data files, or other executables like qemu-img.exe.  You can distribute qemu-img.exe together with your application as part of a zip file or installer.

Regardless of whether you ship qemu-img.exe or build a library, please check QEMU's software license so that you can follow the terms of the GPL open source license.

Stefan

Re: Integration of qemu-img

[Daniel P. Berrangé]

On Thu, Apr 23, 2020 at 12:53:48PM +0200, janine.schneider@fau.de wrote:
> Hy again,
> 
> okay so now we have an easy way out just in case.
> But I still want to build an DLL and/or a shared library for integration
> into the tool. I want the tool to be platform independent and I was
> already able to build qemu-img as cross build with mingw64. Does anybody
> have experience in building a qemu library or tried it already?

It has been discussed in the past, but general wasn't considered a
viable, because any apps using it would have to be strictly licensed
as GPLv2-only. This would prevent the library being used by anything
that includes GPLv3 code, or obviously from closed source apps. This
would seriously restrict how useful any library was.

I would also note that QEMU disk code is not robust against malicously
created disk images. It is possible to create images that inflict
a denial of service in terms of memory and CPU usage. Thus if an
application is handling disk images obtained from untrusted users,
it is desirable for qemu-img to be a separate process, such that
you can put strict resource limits on it as protection against DoS.

> The tool I want to integrate qemu in is published under GPL itself. And
> if I am able to build qemu as library I will share it with the community
> and everybody interested in having it.


Regards,
Daniel
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