ext4 crypto: add padding to filenames before encrypting

This obscures the length of the filenames, to decrease the amount of
information leakage.  By default, we pad the filenames to the next 4
byte boundaries.  This costs nothing, since the directory entries are
aligned to 4 byte boundaries anyway.  Filenames can also be padded to
8, 16, or 32 bytes, which will consume more directory space.

Change-Id: Ibb7a0fb76d2c48e2061240a709358ff40b14f322
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index dfb113816672..bca1bdc67725 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -911,6 +911,7 @@ struct ext4_inode_info {
 
         /* on-disk additional length */
         __u16 i_extra_isize;
+        char i_crypt_policy_flags;
 
         /* Indicate the inline data space. */
         u16 i_inline_off;