libvirt users - May 2015 - Re: virDomainCoreDumpWithFormat files created as root

Greetings,

I am dumping a guest VM memory for inspection using the command
"virDomainCoreDumpWithFormat" and the created files appear to belong
to
root (both user and group).

I have searched around but didn't find any answer. Is there a way to
instruct QEMU to create those files under a different user?

Thank you.

On Thu, May 28, 2015 at 10:29:22AM +0300, NoxDaFox
wrote:
> Greetings,
> 
> I am dumping a guest VM memory for inspection using the command
> "virDomainCoreDumpWithFormat" and the created files appear to
belong to
> root (both user and group).
> 
> I have searched around but didn't find any answer. Is there a way to
> instruct QEMU to create those files under a different user?
No, this is a limitation of the current API & impl

Regards,
Daniel
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On 28.05.2015 09:29, NoxDaFox wrote:
> Greetings,
> 
> I am dumping a guest VM memory for inspection using the command
> "virDomainCoreDumpWithFormat" and the created files appear to
belong to
> root (both user and group).
> 
> I have searched around but didn't find any answer. Is there a way to
> instruct QEMU to create those files under a different user?
> 
The coredump should belong to the user:group that the domain in question
is running under. If (by default) your qemu processes run under
root:root so will the coredump.

Although, I'm wondering if we should not disregard this and make
coredump be always owned by root:root since a coredump may contain
sensitive info, e.g. all kinds of cipher keys. We do that with disk
images, so maybe we should reconsider our politics with coredumps.

Michal

2015-05-28 12:04 GMT+03:00 Michal Privoznik <mprivozn@redhat.com>:
> On 28.05.2015 09:29, NoxDaFox wrote:
> > Greetings,
> >
> > I am dumping a guest VM memory for inspection using the command
> > "virDomainCoreDumpWithFormat" and the created files appear
to belong to
> > root (both user and group).
> >
> > I have searched around but didn't find any answer. Is there a way
to
> > instruct QEMU to create those files under a different user?
> >
>
> The coredump should belong to the user:group that the domain in question
> is running under. If (by default) your qemu processes run under
> root:root so will the coredump.
>
I changed default settings but it didn't work. I can see the qemu processes
now belonging to my user but yet the core dump is root:root. I used to
generate such file with plain QMP 'pmemsave' command and it was creating
it
under libvirt-qemu group which was a bit better. This new command is way
more handy but if I can't sort this issue out I'll need to fallback to
the
previous one.

I set in /etc/libvirt/qemu.conf the keys

user = "myuser"
group = "mygroup"
dynamic_ownership = 1

And restarted libvirtd.

>
> Although, I'm wondering if we should not disregard this and make
> coredump be always owned by root:root since a coredump may contain
> sensitive info, e.g. all kinds of cipher keys. We do that with disk
> images, so maybe we should reconsider our politics with coredumps.
>
> Michal
>
This would limit the API quite much. There are use cases in which the need
is to dump the memory for inspection and forcing it to be root would
cripple the design quite a lot. A policy and an expert SysAdmin is all you
need in these cases.

In my specific case I'm building a test automation system and I was forced
to run everything as admin or spawn a separate process, with admin rights,
which would reset the correct user:group at every core dump taken. Quite
clumsy!