[openstack-dev] [glance] [nova] Verification of glance images before boot
Nikhil Komawar
nik.komawar at gmail.com
Fri Sep 11 14:49:25 UTC 2015
On 9/11/15 10:40 AM, Flavio Percoco wrote:
> On 11/09/15 07:58 -0400, Nikhil Komawar wrote:
>> You are right in the sense that's the ideal scenario.
>>
>> (Impl-wise) However, even today we do not guarantee that behavior. If
>> someone
>> were to propose a new driver or a change driver capability or any
>> thing of such
>> order, images in status killed won't be guaranteed to have removed
>> the garbage
>> data. The driver may not choose to be resilient enough or would not
>> take the
>> responsibility of data removal synchronously on failures.
>
> I think it's glance's responsibility to make sure the driver deletes
> the image data. If the API is not strong enough to guarantee this,
> then we should change that.
>
Sounds like a good direction but I still think we cannot commit to it.
It really depends on the driver and introduction of new or upgrades to
the existing drivers (if not their capabilities) is a not a good idea.
This will result in backward incompatibility in many cases and there can
be enough corner cases when we think about v1, v2 and tasks to address
them at Glance API level.
I personally prefer the image-data delete to be asynchronous and fault
tolerant (on DELETE of image record). However, even that cannot match
the performance of a scrubber like service.
So, in certain cases we need to advice running the scrubber if the data
has the tendency to be left behind.
>> Taking that fact in account, I have thought of Brianna's patch to be
>> okay.
>
> Oh sure, I'm not trying to say it was a wrong choice. Sorry if it
> sounded like that. I was replying to the thought of extending scrubber
> (unless there's a patch that does this that I might have missed).
>
> Cheers,
> Flavio
>
>>
>> On 9/11/15 4:42 AM, Flavio Percoco wrote:
>>
>> On 10/09/15 15:36 -0400, Nikhil Komawar wrote:
>>
>> The solution to this problem is to improve the scrubber to
>> clean up the
>> garbage data left behind in the backend store during such failed
>> uploads.
>>
>> Currently, scrubber cleans up images in pending_delete and
>> extending
>> that to images in killed status would avoid such a situation.
>>
>>
>> While the above would certainly help, I think it's not the right
>> solution. Images in status "killed" should not have data to begin
>> with.
>>
>> I'd rather find a way to clean that data as soon as the image is
>> moved to a "killed" state instead of extending the scrubber.
>>
>> Cheers,
>> Flavio
>>
>>
>> On 9/10/15 3:28 PM, Poulos, Brianna L. wrote:
>>
>> Malini,
>>
>> Thank you for bringing up the ³killed² state as it
>> relates to
>> quota. We
>> opted to move the image to a killed state since that is
>> what occurs
>> when
>> an upload fails, and the signature verification failure
>> would occur
>> during
>> an upload. But we should keep in mind the potential to
>> take up
>> space and
>> yet not take up quota when signature verification fails.
>>
>> Regarding the MD5 hash, there is currently a glance spec
>> [1] to
>> allow the
>> hash method used for the checksum to be
>> configurable‹currently it
>> is
>> hardcoded in glance. After making it configurable, the
>> default
>> would
>> transition from MD5 to something more secure (like SHA-256).
>>
>> [1] https://review.openstack.org/#/c/191542/
>>
>> Thanks,
>> ~Brianna
>>
>>
>>
>>
>> On 9/10/15, 5:10 , "Bhandaru, Malini K"
>> <malini.k.bhandaru at intel.com>
>> wrote:
>>
>>
>> Brianna, I can imagine a denial of service attack by
>> uploading
>> images
>> whose signature is invalid if we allow them to reside
>> in Glance
>> In a "killed" state. This would be less of an issue
>> "killed"
>> images still
>> consume storage quota until actually deleted.
>> Also given MD-5 less secure, why not have the default
>> hash be
>> SHA-1 or 2?
>> Regards
>> Malini
>>
>> -----Original Message-----
>> From: Poulos, Brianna L.
>> [mailto:Brianna.Poulos at jhuapl.edu]
>> Sent: Wednesday, September 09, 2015 9:54 AM
>> To: OpenStack Development Mailing List (not for usage
>> questions)
>> Cc: stuart.mclaren at hp.com
>> Subject: Re: [openstack-dev] [glance] [nova]
>> Verification of
>> glance
>> images before boot
>>
>> Stuart is right about what will currently happen in
>> Nova when
>> an image is
>> downloaded, which protects against unintentional
>> modifications
>> to the
>> image data.
>>
>> What is currently being worked on is adding the
>> ability to
>> verify a
>> signature of the checksum. The flow of this is as
>> follows:
>> 1. The user creates a signature of the "checksum hash"
>> (currently MD5) of
>> the image data offline.
>> 2. The user uploads a public key certificate, which
>> can be used
>> to verify
>> the signature to a key manager (currently Barbican).
>> 3. The user creates an image in glance, with signature
>> metadata
>> properties.
>> 4. The user uploads the image data to glance.
>> 5. If the signature metadata properties exist, glance
>> verifies
>> the
>> signature of the "checksum hash", including retrieving
>> the
>> certificate
>>
>> >from the key manager.
>>
>> 6. If the signature verification fails, glance moves
>> the image
>> to a
>> killed state, and returns an error message to the user.
>> 7. If the signature verification succeeds, a log message
>> indicates that
>> it succeeded, and the image upload finishes successfully.
>>
>> 8. Nova requests the image from glance, along with the
>> image
>> properties,
>> in order to boot it.
>> 9. Nova uses the signature metadata properties to
>> verify the
>> signature
>> (if a configuration option is set).
>> 10. If the signature verification fails, nova does not
>> boot the
>> image,
>> but errors out.
>> 11. If the signature verification succeeds, nova boots
>> the
>> image, and a
>> log message notes that the verification succeeded.
>>
>> Regarding what is currently in Liberty, the blueprint
>> mentioned
>> [1] has
>> merged, and code [2] has also been merged in glance,
>> which
>> handles steps
>> 1-7 of the flow above.
>>
>> For steps 7-11, there is currently a nova blueprint
>> [3], along
>> with code
>> [4], which are proposed for Mitaka.
>>
>> Note that we are in the process of adding official
>> documentation, with
>> examples of creating the signature as well as the
>> properties
>> that need to
>> be added for the image before upload. In the
>> meantime, there's
>> an
>> etherpad that describes how to test the signature
>> verification
>> functionality in Glance [5].
>>
>> Also note that this is the initial approach, and there
>> are some
>> limitations. For example, ideally the signature would
>> be based
>> on a
>> cryptographically secure (i.e. not MD5) hash of the
>> image.
>> There is a
>> spec in glance to allow this hash to be configurable [6].
>>
>> [1]
>> https://blueprints.launchpad.net/glance/+spec/
>> image-signing-and-verificati
>> o
>> n-support
>> [2]
>> https://github.com/openstack/glance/commit/
>> 484ef1b40b738c87adb203bba6107dd
>> b
>> 4b04ff6e
>> [3] https://review.openstack.org/#/c/188874/
>> [4] https://review.openstack.org/#/c/189843/
>> [5]
>> https://etherpad.openstack.org/p/
>> liberty-glance-image-signing-instructions
>> [6] https://review.openstack.org/#/c/191542/
>>
>>
>> Thanks,
>> ~Brianna
>>
>>
>>
>>
>> On 9/9/15, 12:16 , "Nikhil Komawar"
>> <nik.komawar at gmail.com>
>> wrote:
>>
>>
>> That's correct.
>>
>> The size and the checksum are to be verified
>> outside of
>> Glance, in this
>> case Nova. However, you may want to note that it's
>> not
>> necessary that
>> all Nova virt drivers would use py-glanceclient so
>> you
>> would want to
>> check the download specific code in the virt
>> driver your
>> Nova
>> deployment is using.
>>
>> Having said that, essentially the flow seems
>> appropriate.
>> Error must be
>> raise on mismatch.
>>
>> The signing BP was to help prevent the compromised
>> Glance
>> from changing
>> the checksum and image blob at the same time. Using a
>> digital
>> signature, you can prevent download of compromised
>> data.
>> However, the
>> feature has just been implemented in Glance;
>> Glance users
>> may take time
>> to adopt.
>>
>>
>>
>> On 9/9/15 11:15 AM, stuart.mclaren at hp.com wrote:
>>
>> The glance client (running 'inside' the Nova
>> server)
>> will
>> re-calculate the checksum as it downloads the
>> image and
>> then compare
>> it against the expected value. If they don't
>> match an
>> error will be
>> raised.
>>
>>
>> How can I know that the image that a new
>> instance
>> is spawned from -
>> is actually the image that was originally
>> registered in glance - and
>> has not been maliciously tampered with in
>> some way?
>>
>> Is there some kind of verification that is
>> performed against the
>> md5sum of the registered image in glance
>> before a
>> new instance is
>> spawned?
>>
>> Is that done by Nova?
>> Glance?
>> Both? Neither?
>>
>> The reason I ask is some 'paranoid'
>> security (that
>> is their job I
>> suppose) people have raised these questions.
>>
>> I know there is a glance BP already merged
>> for L
>> [1] - but I would
>> like to understand the actual flow in a
>> bit more
>> detail.
>>
>> Thanks.
>>
>> [1]
>>
>>
>> https://blueprints.launchpad.net/glance/+spec/
>> image-signing-and-verif
>> ica
>> tion-support
>>
>>
>> --
>> Best Regards,
>> Maish Saidel-Keesing
>>
>>
>>
>> ------------------------------
>>
>>
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>>
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>>
>> End of OpenStack-dev Digest, Vol 41, Issue 22
>> *********************************************
>>
>>
>>
>>
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>> Thanks,
>> Nikhil
>>
>>
>>
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>> Thanks,
>> Nikhil
>>
>>
>>
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>> Thanks,
>> Nikhil
>>
>
--
Thanks,
Nikhil
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