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Re: [libvirt] security: the qemu agent command "guest-exec" may cause Insider Access



On Fri, Aug 25, 2017 at 08:59:54AM +0000, Zhangbo (Oscar) wrote:
On Fri, Aug 25, 2017 at 06:45:18AM +0000, Zhangbo (Oscar) wrote:
Hi all:
    The Host Administrator is capable of running any exec in guests via the
qemu-ga command "guest-exec", eg:

       virsh qemu-agent-command test_guest '{"execute": "guest-exec",
"arguments": {"path": "ifconfig", "arg": [ "eth1", "192.168.0.99" ],"capture-output":
true } }'
{"return":{"pid":12425}}
      virsh qemu-agent-command test_guest '{"execute": "guest-exec-status",
"arguments": { "pid": 12425 } }'
{"return":{"exitcode":0,"exited":true}}

     The example above just change the guests' ip address, the Administrator
may also change guests' user password, get sensitive information, etc. which
causes Insider Access.
     The Administrator also can use other commands such as "
guest-file-open" that also cause Insider Access.

     So, how to avoid this security problem, what's your suggestion?
     Thanks!


What's your setup that this, in particular, is your concern?  Do you
have everything encrypted by keys that are not reachable for the host
administrator?  How are those saved?  For example, how do you guard
against the host administrator killing the domain?  Or mounting the disk

Killing the domain is acceptable somehow at some degree, but leaking sensitive
information, for example, trade secret, is horrible. We most concern is to protect
that information by (maybe)disabling "guest-exec" guest commands etc.


Host can read all of the guest's memory or mount the image and modify
the guest agent.  Or even add their own communication program that can
do anything.

Another concern, as mentioned in another mail, is that, if the cloud tenant himself
installed the guest agent, and doesn't know the "adding --blacklist" issue, that guest is in danger.

of the domain, doing whatever they want to with it and starting it back?
Or million other things that come to mind.  Not trusting the host
administrator is kinda (well, precisely) like not trusting root on *NIX
machine.

Martin

P.S.: Maybe more aluminium could help, but I haven't tried yet.

Best Regrads
Oscar

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