ext4 crypto: add ext4 encryption facilities

On encrypt, we will re-assign the buffer_heads to point to a bounce
page rather than the control_page (which is the original page to write
that contains the plaintext). The block I/O occurs against the bounce
page.  On write completion, we re-assign the buffer_heads to the
original plaintext page.

On decrypt, we will attach a read completion callback to the bio
struct. This read completion will decrypt the read contents in-place
prior to setting the page up-to-date.

The current encryption mode, AES-256-XTS, lacks cryptographic
integrity. AES-256-GCM is in-plan, but we will need to devise a
mechanism for handling the integrity data.

Signed-off-by: Michael Halcrow <mhalcrow@google.com>
Signed-off-by: Ildar Muslukhov <ildarm@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 8 insertions, 0 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index e47a552fea05..1008ca258de4 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -876,6 +876,9 @@ static struct inode *ext4_alloc_inode(struct super_block *sb)
         atomic_set(&ei->i_ioend_count, 0);
         atomic_set(&ei->i_unwritten, 0);
         INIT_WORK(&ei->i_rsv_conversion_work, ext4_end_io_rsv_work);
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
+        ei->i_encryption_key.mode = EXT4_ENCRYPTION_MODE_INVALID;
+#endif
 
         return &ei->vfs_inode;
 }
@@ -3431,6 +3434,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
         if (sb->s_bdev->bd_part)
                 sbi->s_sectors_written_start =
                         part_stat_read(sb->s_bdev->bd_part, sectors[1]);
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
+        /* Modes of operations for file and directory encryption. */
+        sbi->s_file_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
+        sbi->s_dir_encryption_mode = EXT4_ENCRYPTION_MODE_INVALID;
+#endif
 
         /* Cleanup superblock name */
         for (cp = sb->s_id; (cp = strchr(cp, '/'));)