[openstack-dev] [nova] Minimal secure identification of a new VM

Fox, Kevin M Kevin.Fox at pnnl.gov
Wed Apr 6 21:41:18 UTC 2016

-1 for man in the middle susceptible solutions. This also doesn't solve all the issues listed in the spec, such as suspended nodes, snapshotted nodes, etc.

Nova has several back channel mechanisms at its disposal. We should use one or more of them to solve the problem properly instead of opening a security hole in our solution to a security problem.

Such as:
 * The nova console is one mechanism that could be utilized as a secure back channel.
 * The vm based instances could add a virutal serial port as a back channel.
 * Some bare metal bmc's support virtual cd's which could be loaded with fresh credentials upon request.
 * The metadata server is reliable in certain situations.

I'm sure there are more options too.

The instance user spec covers a lot of that stuff.

I'm ok if we want to refactor the instance user spec to cover creating phase 1 credentials that are intended to be used for things other then getting a keystone token. It could be used to register/reregister with ipa, chef, puppet, etc. We just need to reword the spec to cover that use case too.

I'm also not tied to the implementation listed. it just needs to meet the requirements.


From: Adam Young [ayoung at redhat.com]
Sent: Wednesday, April 06, 2016 2:09 PM
To: openstack-dev at lists.openstack.org
Subject: Re: [openstack-dev] [nova] Minimal secure identification of a new VM

On 04/06/2016 05:42 AM, Daniel P. Berrange wrote:
> On Tue, Apr 05, 2016 at 06:00:55PM -0400, Adam Young wrote:
>> We have a use case where we want to register a newly spawned Virtual machine
>> with an identity provider.
>> Heat also has a need to provide some form of Identity for a new VM.
>> Looking at the set of utilities right now, there does not seem to be a
>> secure way to do this.  Injecting files does not provide a path that cannot
>> be seen by other VMs or machines in the system.
>> For our use case, a short lived One-Time-Password is sufficient, but for
>> others, I think asymmetric key generation makes more sense.
>> Is the following possible:
>> 1.  In cloud-init, the VM generates a Keypair, then notifies the No0va
>> infrastructure (somehow) that it has done so.
> There's no currently secure channel for the guest to push information
> to Nova.
We need to secure the message queue from the compute node to conductor.
This is very achievable:

1.  Each compute node gets its own rabbit user
2.  Messages from compute node to Conductor are validated as to what
node sent them

We should enable TLS on the network as well, or password can be
sniffed.  Self signed is crappy, but probably sufficient for a baseline
deployment. Does not defend against MITM.  Puppet based deployments can
X509 client cert is a better auth mechanism than password, but not

>   The best we have is the metadata service, but we'd need to
> secure that with https, because the metadata server cannot be assumed
> to be running on the same host as the VM & so the channel is not protected
> against MITM attacks.
> Also currently the metadata server is readonly with the guest pulling
> information from it - it doesn't currently allow guests to push information
> into it. This is nice because the metadata servers could theoretically be
> locked down to prevent may interactions with the rest of nova - it should
> only need read-only access to info about the guests it is serving. If we
> turn the metadata server into a bi-directional service which can update
> information about guests, then it opens it up as a more attractive avenue
> of attack for guest OS trying breach the host infra. This is a fairly
> general concern with any approach where the guest has to have the ability
> to push information back into Nova.
>> 2.  Nova Compute reads the public Key off the device and sends it to
>> conductor, which would then associate the public key with the server?
>> 3.  A third party system could then validate the association of the public
>> key and the server, and build a work flow based on some signed document from
>> the VM?
> Regards,
> Daniel

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