On Tue, Dec 15, 2015 at 10:04 PM, Gregory Farnum <gfar...@redhat.com> wrote:
> On Tue, Dec 15, 2015 at 1:58 AM, Adam Kupczyk <akupc...@mirantis.com> wrote:
>>
>>
>> On Mon, Dec 14, 2015 at 9:28 PM, Gregory Farnum <gfar...@redhat.com> wrote:
>>>
>>> On Mon, Dec 14, 2015 at 5:17 AM, Radoslaw Zarzynski
>>> <rzarzyn...@mirantis.com> wrote:
>>> > Hello Folks,
>>> >
>>> > I would like to publish a proposal regarding improvements to Ceph
>>> > data-at-rest encryption mechanism. Adam Kupczyk and I worked
>>> > on that in last weeks.
>>> >
>>> > Initially we considered several architectural approaches and made
>>> > several iterations of discussions with Intel storage group. The proposal
>>> > is condensed description of the solution we see as the most promising
>>> > one.
>>> >
>>> > We are open to any comments and questions.
>>> >
>>> > Regards,
>>> > Adam Kupczyk
>>> > Radoslaw Zarzynski
>>> >
>>> >
>>> > =======================
>>> > Summary
>>> > =======================
>>> >
>>> > Data at-rest encryption is mechanism for protecting data center
>>> > operator from revealing content of physical carriers.
>>> >
>>> > Ceph already implements a form of at rest encryption. It is performed
>>> > through dm-crypt as intermediary layer between OSD and its physical
>>> > storage. The proposed at rest encryption mechanism will be orthogonal
>>> > and, in some ways, superior to already existing solution.
>>> >
>>> > =======================
>>> > Owners
>>> > =======================
>>> >
>>> > * Radoslaw Zarzynski (Mirantis)
>>> > * Adam Kupczyk (Mirantis)
>>> >
>>> > =======================
>>> > Interested Parties
>>> > =======================
>>> >
>>> > If you are interested in contributing to this blueprint, or want to be
>>> > a "speaker" during the Summit session, list your name here.
>>> >
>>> > Name (Affiliation)
>>> > Name (Affiliation)
>>> > Name
>>> >
>>> > =======================
>>> > Current Status
>>> > =======================
>>> >
>>> > Current data at rest encryption is achieved through dm-crypt placed
>>> > under OSD’s filestore. This solution is a generic one and cannot
>>> > leverage Ceph-specific characteristics. The best example is that
>>> > encryption is done multiple times - one time for each replica. Another
>>> > issue is lack of granularity - either OSD encrypts nothing, or OSD
>>> > encrypts everything (with dm-crypt on).
>>> >
>>> > Cryptographic keys are stored on filesystem of storage node that hosts
>>> > OSDs. Changing them require redeploying the OSDs.
>>> >
>>> > The best way to address those issues seems to be introducing
>>> > encryption into Ceph OSD.
>>> >
>>> > =======================
>>> > Detailed Description
>>> > =======================
>>> >
>>> > In addition to the currently available solution, Ceph OSD would
>>> > accommodate encryption component placed in the replication mechanisms.
>>> >
>>> > Data incoming from Ceph clients would be encrypted by primary OSD. It
>>> > would replicate ciphertext to non-primary members of an acting set.
>>> > Data sent to Ceph client would be decrypted by OSD handling read
>>> > operation. This allows to:
>>> > * perform only one encryption per write,
>>> > * achieve per-pool key granulation for both key and encryption itself.
>>> >
>>> > Unfortunately, having always and everywhere the same key for a given
>>> > pool is unacceptable - it would make cluster migration and key change
>>> > extremely burdensome process. To address those issues crypto key
>>> > versioning would be introduced. All RADOS objects inside single
>>> > placement group stored on a given OSD would use the same crypto key
>>> > version. The same PG on other replica may use different version of the
>>> > same, per pool-granulated key.
>>> >
>>> > In typical case ciphertext data transferred from OSD to OSD can be
>>> > used without change. This is when both OSDs have the same crypto key
>>> > version for given placement group. In rare cases when crypto keys are
>>> > different (key change or transition period) receiving OSD will recrypt
>>> > with local key versions.
>>>
>>> I don't understand this part at all. Do you plan to read and rewrite
>>> the entire PG whenever you change the "key version"? How often do you
>>> plan to change these keys? What is even the point of changing them,
>>> since anybody who can control an OSD can grab the entire current key
>>> set?
>>
>> We envision that key change will happen very infrequently. Usually in
>> reaction to some possible security breach.
>> After key version is incremented, nothing happens automatically. Old key is
>> used for as long as  PG is not empty. When first RADOS object is created,
>> the current key version is locked to PG.
>> There is no solution when someone gets control over OSD - either by running
>> custom OSD binary or extracting data by impersonating client. It is outside
>> of scope of at-rest-encryption. We only addressed cases when media storage
>> somehow leaves datacenter premises. Ability to change key is necessary,
>> since we need procedure to recover data security after keys are compromised.
>>>
>>>
>>> > For compression to be effective it must be done before encryption. Due
>>> > to that encryption may be applied differently for replication pools
>>> > and EC pools. Replicated pools do not implement compression; for those
>>> > pools encryption is applied right after data enters OSD. For EC pools
>>> > encryption is applied after compressing. When compression will be
>>> > implemented for replicated pools, it must be placed before encryption.
>>>
>>> So this means you'll be encrypting the object data, but not the omap
>>> nor xattrs, and not the file names on disk. Is that acceptable to
>>> people? It's probably fine for a lot of rbd use cases, but not for
>>> RGW, CephFS, nor raw RADOS where meaningful metadata (and even *data*)
>>> is stored in those regions. I'd rather a solution worked on the full
>>> data set. :/
>>
>> We intend to encrypt:
>> - object data
>> - omap values
>> - xattr values
>> We consider to encrypt:
>> - object names
>> - xattr names
>> We are unable to encrypt:
>> - omap names
>
> Are there any encryption mechanisms that can efficiently and
> effectively encrypt pieces of data that small? I don't have any
> expertise in crypto but I thought you needed a certain minimum size of
> the output blob to get any security at all. If we're turning every
> 8-byte thing into a 64-byte thing that's going to go much worse for us
> than just having every OSD encrypt their local disk...
> -Greg

Hello Greg,

In addition to what Adam said:
 * stream ciphers don't have requirements on data length,
 * block cipher like AES may be turned into stream cipher
   using specific mode of operation (eg. CTR).

Regards,
Radoslaw
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