This patchset proposes a method for encrypting in EXT4 data read and write paths. It's a proof-of-concept/prototype only right now. Outstanding issues: * While it seems to work well with complex tasks like a parallel kernel build, fsx is pretty good at reliably breaking it in its current form. I think it's trying to decrypt a page of all zeros when doing a mmap'd write after an falloc. I want to get feedback on the overall approach before I spend too much time bug-hunting. * It has not undergone a security audit/review. It isn't IND-CCA2 secure, and that's the goal. We need a way to store (at least) page-granular metadata. * Only the file data is encrypted. I'd like to look into also encrypting the file system metadata with a mount-wide key. That's for another phase of development. * The key management isn't fleshed out. I've hacked in some eCryptfs stuff because it was the fastest way for me to stand up the prototype with real crypto keys. Use ecryptfs-add-passphrase to add a key to the keyring, and then pass the hex sig as the encrypt_key_sig mount option: # apt-get install ecryptfs-utils # echo -n "hunter2" | ecryptfs-add-passphrase Passphrase: Inserted auth tok with sig [4cb927ea0c564410] into the user session keyring # mount -o encrypt_key_sig=4cb927ea0c564410 /dev/sdb1 /mnt/ext4crypt * The EXT4 block size must be the same as the page size. I'm not yet sure whether I will want to try to support block-granular encryption or page-granular encryption. There are implications with respect to how much the integrity data occupies in relation to the encrypted data. Mimi, maybe an approach like this one will work out for IMA. We've just got to figure out where to store the block- or page-granular integrity data. I've broken up the patches so that not only can each one build after application, but discrete steps of functionality can be tested one patch at a time. A couple of other thoughts: * Maybe the write submit path can complete on the encryption callback. Not sure what that might buy us. * Maybe a key with a specific descriptor in each user's keyring (e.g. "EXT4_DEFAULT_KEY") can be used when creating new files so that each user can use his own key in a common EXT4 mount. Or maybe we can specify an encryption context in the parent directory xattr. Michael Halcrow (5): ext4: Adds callback support for bio read completion ext4: Adds EXT4 encryption facilities ext4: Implements the EXT4 encryption write path ext4: Adds EXT4 encryption read callback support ext4: Implements real encryption in the EXT4 write and read paths fs/buffer.c | 46 +++- fs/ext4/Makefile | 9 +- fs/ext4/crypto.c | 629 ++++++++++++++++++++++++++++++++++++++++++++ fs/ext4/ext4.h | 50 ++++ fs/ext4/file.c | 9 +- fs/ext4/inode.c | 196 +++++++++++++- fs/ext4/namei.c | 3 + fs/ext4/page-io.c | 182 ++++++++++--- fs/ext4/super.c | 34 ++- fs/ext4/xattr.h | 1 + include/linux/bio.h | 3 + include/linux/blk_types.h | 4 + include/linux/buffer_head.h | 8 + 13 files changed, 1118 insertions(+), 56 deletions(-) create mode 100644 fs/ext4/crypto.c -- 2.0.0.526.g5318336 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
