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

["Luís Henriques" <lhenriques@suse.de>]

Xiubo Li <xiubli@redhat.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@suse.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 :-(
>
> Yeah, good catch. The snapshot handler in MDS hasn't handled this case yet,
> though the kclient has passed it to MDS server.
>
> The snapshot alternate_name raw ciphertext should be stored in SnapInfo struct
> along with the 'name'.
>
>
>>
>> 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;
>> +		}
>
> We should fix the MDS side bug and then this workaroud will be no needed.

Yep, I've been looking into that too but it's taking a bit to understand
all that's going on there.  I'm still trying, but the MDS code (and C++ in
general) is a bit... challenging.

Cheers,
-- 
Luís

>
> - Xiubo
>
>>   	} 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.
>> +	 */
>> +	if (ceph_snap(dir) == CEPH_SNAPDIR)
>> +		d_drop(dentry);
>> +
>>   out_req:
>>   	ceph_mdsc_put_request(req);
>>   out:
>> diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
>> index 8b0832271fdf..080824610b73 100644
>> --- a/fs/ceph/inode.c
>> +++ b/fs/ceph/inode.c
>> @@ -182,6 +182,13 @@ struct inode *ceph_get_snapdir(struct inode *parent)
>>   	ci->i_rbytes = 0;
>>   	ci->i_btime = ceph_inode(parent)->i_btime;
>>   +	/* if encrypted, just borough fscrypt_auth from parent */
>> +	if (IS_ENCRYPTED(parent)) {
>> +		struct ceph_inode_info *pci = ceph_inode(parent);
>> +		inode->i_flags |= S_ENCRYPTED;
>> +		ci->fscrypt_auth_len = pci->fscrypt_auth_len;
>> +		ci->fscrypt_auth = pci->fscrypt_auth;
>> +	}
>>   	if (inode->i_state & I_NEW) {
>>   		inode->i_op = &ceph_snapdir_iops;
>>   		inode->i_fop = &ceph_snapdir_fops;
>> @@ -632,7 +639,8 @@ void ceph_free_inode(struct inode *inode)
>>     	kfree(ci->i_symlink);
>>   #ifdef CONFIG_FS_ENCRYPTION
>> -	kfree(ci->fscrypt_auth);
>> +	if (ceph_snap(inode) != CEPH_SNAPDIR)
>> +		kfree(ci->fscrypt_auth);
>>   #endif
>>   	fscrypt_free_inode(inode);
>>   	kmem_cache_free(ceph_inode_cachep, ci);
>>
>