Messages in this thread | | | Subject | Re: [RFC PATCH v2 0/3] ceph: add support for snapshot names encryption | From | Xiubo Li <> | Date | Thu, 17 Mar 2022 20:44:36 +0800 |
| |
On 3/17/22 8:41 PM, Jeff Layton wrote: > On Thu, 2022-03-17 at 20:31 +0800, Xiubo Li wrote: >> On 3/17/22 8:01 PM, Jeff Layton wrote: >>> On Thu, 2022-03-17 at 11:11 +0000, Luís Henriques wrote: >>>> Xiubo Li <xiubli@redhat.com> writes: >>>> >>>>> On 3/17/22 6:01 PM, Jeff Layton wrote: >>>>>> I'm not sure we want to worry about .snap directories here since they >>>>>> aren't "real". IIRC, snaps are inherited from parents too, so you could >>>>>> do something like >>>>>> >>>>>> mkdir dir1 >>>>>> mkdir dir1/.snap/snap1 >>>>>> mkdir dir1/dir2 >>>>>> fscrypt encrypt dir1/dir2 >>>>>> >>>>>> There should be nothing to prevent encrypting dir2, but I'm pretty sure >>>>>> dir2/.snap will not be empty at that point. >>>>> If we don't take care of this. Then we don't know which snapshots should do >>>>> encrypt/dencrypt and which shouldn't when building the path in lookup and when >>>>> reading the snapdir ? >>>> In my patchset (which I plan to send a new revision later today, I think I >>>> still need to rebase it) this is handled by using the *real* snapshot >>>> parent inode. If we're decrypting/encrypting a name for a snapshot that >>>> starts with a '_' character, we first find the parent inode for that >>>> snapshot and only do the operation if that parent is encrypted. >>>> >>>> In the other email I suggested that we could prevent enabling encryption >>>> in a directory when there are snapshots above in the hierarchy. But now >>>> that I think more about it, it won't solve any problem because you could >>>> create those snapshots later and then you would still need to handle these >>>> (non-encrypted) "_name_xxxx" snapshots anyway. >>>> >>> Yeah, that sounds about right. >>> >>> What happens if you don't have the snapshot parent's inode in cache? >>> That can happen if you (e.g.) are running NFS over ceph, or if you get >>> crafty with name_to_handle_at() and open_by_handle_at(). >>> >>> Do we have to do a LOOKUPINO in that case or does the trace contain that >>> info? If it doesn't then that could really suck in a big hierarchy if >>> there are a lot of different snapshot parent inodes to hunt down. >>> >>> I think this is a case where the client just doesn't have complete >>> control over the dentry name. It may be better to just not encrypt them >>> if it's too ugly. >>> >>> Another idea might be to just use the same parent inode (maybe the >>> root?) for all snapshot names. It's not as secure, but it's probably >>> better than nothing. >> Does it allow to have different keys for the subdirs in the hierarchy ? >> From my test it doesn't. >> > No. Once you set a key on directory you can't set another on a subtree > of it. If so. Yeah, I think your approach mentioned above is the best. >> If so we can always use the same oldest ancestor in the hierarchy, who >> has encryption key, to encyrpt/decrypt all the .snap in the hierarchy, >> then just need to lookup oldest ancestor inode only once. >> Just like this.
-- Xiubo
> That's a possibility.
| |