linux-kernel - Re: [RFC PATCH] ceph: add support for encrypted snapshot names

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Date:   Fri, 25 Feb 2022 13:27:52 +0000
From:   Luís Henriques <lhenriques@...e.de>
To:     Xiubo Li <xiubli@...hat.com>
Cc:     Jeff Layton <jlayton@...nel.org>,
        Ilya Dryomov <idryomov@...il.com>, ceph-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] ceph: add support for encrypted snapshot names

Xiubo Li <xiubli@...hat.com> writes:

> On 2/25/22 5:48 PM, Luís Henriques wrote:
>> Xiubo Li <xiubli@...hat.com> writes:
>>
>>> On 2/24/22 7:21 PM, Luís Henriques wrote:
>>>> Since filenames in encrypted directories are already encrypted and shown
>>>> as a base64-encoded string when the directory is locked, snapshot names
>>>> should show a similar behaviour.
>>>>
>>>> Signed-off-by: Luís Henriques <lhenriques@...e.de>
>>>> ---
>>>>    fs/ceph/dir.c   | 15 +++++++++++++++
>>>>    fs/ceph/inode.c | 10 +++++++++-
>>>>    2 files changed, 24 insertions(+), 1 deletion(-)
>>>>
>>>> Support on the MDS for names that'll be > MAX_NAME when base64 encoded is
>>>> still TBD.  I thought it would be something easy to do, but snapshots
>>>> don't seem to make use of the CDir/CDentry (which is where alternate_name
>>>> is stored on the MDS).  I'm still looking into this, but I may need some
>>>> help there :-(
>>>>
>>>> Cheers,
>>>> --
>>>> Luís
>>>>
>>>> diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
>>>> index a449f4a07c07..20ae600ee7cd 100644
>>>> --- a/fs/ceph/dir.c
>>>> +++ b/fs/ceph/dir.c
>>>> @@ -1065,6 +1065,13 @@ static int ceph_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
>>>>    		op = CEPH_MDS_OP_MKSNAP;
>>>>    		dout("mksnap dir %p snap '%pd' dn %p\n", dir,
>>>>    		     dentry, dentry);
>>>> +		/* XXX missing support for alternate_name in snapshots */
>>>> +		if (IS_ENCRYPTED(dir) && (dentry->d_name.len >= 189)) {
>>>> +			dout("encrypted snapshot name too long: %pd len: %d\n",
>>>> +			     dentry, dentry->d_name.len);
>>>> +			err = -ENAMETOOLONG;
>>>> +			goto out;
>>>> +		}
>>>>    	} else if (ceph_snap(dir) == CEPH_NOSNAP) {
>>>>    		dout("mkdir dir %p dn %p mode 0%ho\n", dir, dentry, mode);
>>>>    		op = CEPH_MDS_OP_MKDIR;
>>>> @@ -1109,6 +1116,14 @@ static int ceph_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
>>>>    	    !req->r_reply_info.head->is_target &&
>>>>    	    !req->r_reply_info.head->is_dentry)
>>>>    		err = ceph_handle_notrace_create(dir, dentry);
>>>> +
>>>> +	/*
>>>> +	 * If we have created a snapshot we need to clear the cache, otherwise
>>>> +	 * snapshot will show encrypted filenames in readdir.
>>>> +	 */
>>> Do you mean dencrypted filenames ?
>> What I see without this d_drop() is that, if I run an 'ls' in a snapshot
>> directory immediately after creating it, the filenames in that snapshot
>> will be encrypted.  Maybe there's a bug somewhere else and this d_drop()
>> isn't the right fix...?
>
> Maybe should fix this in ceph_fill_trace() in

Hmm... maybe, I'll have to check.  Thank's for the suggestion.  I'll try
to investigate this before sending a new revision which, hopefully, will
have some MDS-side changes to support the altname (which I'm still trying
to untangle).

Cheers,
-- 
Luís

>
>        } else if ((req->r_op == CEPH_MDS_OP_LOOKUPSNAP ||... {
>
>        }
>
> ?
>
> I still haven't gotten where will encrypt it yet in mksnap case. Because the MDS
> will set the 'rinfo->head->is_target' but won't set the
> 'rinfo->head->is_dentry', so in this case the dentry should keep the 
> human readable name.
>
> - Xiubo
>
>
>> Cheers,
>