eCryptfs: don't encrypt file key with filename key

eCryptfs has file encryption keys (FEK), file encryption key encryption
keys (FEKEK), and filename encryption keys (FNEK).  The per-file FEK is
encrypted with one or more FEKEKs and stored in the header of the
encrypted file.  I noticed that the FEK is also being encrypted by the
FNEK.  This is a problem if a user wants to use a different FNEK than
their FEKEK, as their file contents will still be accessible with the
FNEK.

This is a minimalistic patch which prevents the FNEKs signatures from
being copied to the inode signatures list.  Ultimately, it keeps the FEK
from being encrypted with a FNEK.

Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Acked-by: Dustin Kirkland <kirkland@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index f6caeb1d1106..bdca1f4b3a3e 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -946,6 +946,8 @@ static int ecryptfs_copy_mount_wide_sigs_to_inode_sigs(
         list_for_each_entry(global_auth_tok,
                             &mount_crypt_stat->global_auth_tok_list,
                             mount_crypt_stat_list) {
+                if (global_auth_tok->flags & ECRYPTFS_AUTH_TOK_FNEK)
+                        continue;
                 rc = ecryptfs_add_keysig(crypt_stat, global_auth_tok->sig);
                 if (rc) {
                         printk(KERN_ERR "Error adding keysig; rc = [%d]\n", rc);