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

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Date:   Thu, 24 Feb 2022 11:21:42 +0000
From:   Luís Henriques <lhenriques@...e.de>
To:     Jeff Layton <jlayton@...nel.org>, Xiubo Li <xiubli@...hat.com>,
        Ilya Dryomov <idryomov@...il.com>
Cc:     ceph-devel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Luís Henriques <lhenriques@...e.de>
Subject: [RFC PATCH] ceph: add support for encrypted snapshot names

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.
+	 */
+	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);