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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.

Taking that fact in account, I have thought of Brianna's patch to be okay.

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
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> ------------------------------
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> OpenStack-dev mailing list
>>>>>>> OpenStack-dev at lists.openstack.org
>>>>>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>>>>>>>
>>>>>>>
>>>>>>> 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

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