Re: Important: RGW multisite bug may silently corrupt encrypted objects on replication

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On Tue, May 30, 2023 at 8:22 AM Tobias Urdin <tobias.urdin@xxxxxxxxxx> wrote:
>
> Hello Casey,
>
> Thanks for the information!
>
> Can you please confirm that this is only an issue when using “rgw_crypt_default_encryption_key”
> config opt that says “testing only” in the documentation [1] to enable encryption and not when using
> Barbican or Vault as KMS or using SSE-C with the S3 API?

unfortunately, all flavors of server-side encryption (SSE-C, SSE-KMS,
SSE-S3, and rgw_crypt_default_encryption_key) are affected by this
bug, as they share the same encryption logic. the main difference is
where they get the key

>
> [1] https://docs.ceph.com/en/quincy/radosgw/encryption/#automatic-encryption-for-testing-only
>
> > On 26 May 2023, at 22:45, Casey Bodley <cbodley@xxxxxxxxxx> wrote:
> >
> > Our downstream QE team recently observed an md5 mismatch of replicated
> > objects when testing rgw's server-side encryption in multisite. This
> > corruption is specific to s3 multipart uploads, and only affects the
> > replicated copy - the original object remains intact. The bug likely
> > affects Ceph releases all the way back to Luminous where server-side
> > encryption was first introduced.
> >
> > To expand on the cause of this corruption: Encryption of multipart
> > uploads requires special handling around the part boundaries, because
> > each part is uploaded and encrypted separately. In multisite, objects
> > are replicated in their encrypted form, and multipart uploads are
> > replicated as a single part. As a result, the replicated copy loses
> > its knowledge about the original part boundaries required to decrypt
> > the data correctly.
> >
> > We don't have a fix yet, but we're tracking it in
> > https://tracker.ceph.com/issues/46062. The fix will only modify the
> > replication logic, so won't repair any objects that have already
> > replicated incorrectly. We'll need to develop a radosgw-admin command
> > to search for affected objects and reschedule their replication.
> >
> > In the meantime, I can only advise multisite users to avoid using
> > encryption for multipart uploads. If you'd like to scan your cluster
> > for existing encrypted multipart uploads, you can identify them with a
> > s3 HeadObject request. The response would include a
> > x-amz-server-side-encryption header, and the ETag header value (with
> > "s removed) would be longer than 32 characters (multipart ETags are in
> > the special form "<md5sum>-<num parts>"). Take care not to delete the
> > corrupted replicas, because an active-active multisite configuration
> > would go on to delete the original copy.
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>
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