diff options
| author | Theodore Ts'o <tytso@mit.edu> | 2015-05-01 16:56:50 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2015-05-01 16:56:50 -0400 |
| commit | a44cd7a05496d60fd2ba8cca080e3db8f481549b (patch) | |
| tree | dd8d05d845817e4a429804d8ffe09dd68b6881e6 /fs/ext4/ext4_crypto.h | |
| parent | 5de0b4d0cd153c471640b13aae6ae6d18d0a4603 (diff) | |
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>
Diffstat (limited to 'fs/ext4/ext4_crypto.h')
| -rw-r--r-- | fs/ext4/ext4_crypto.h | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/fs/ext4/ext4_crypto.h b/fs/ext4/ext4_crypto.h index c2ba35a914b6..d75159c101ce 100644 --- a/fs/ext4/ext4_crypto.h +++ b/fs/ext4/ext4_crypto.h @@ -20,12 +20,20 @@ struct ext4_encryption_policy { char version; char contents_encryption_mode; char filenames_encryption_mode; + char flags; char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE]; } __attribute__((__packed__)); #define EXT4_ENCRYPTION_CONTEXT_FORMAT_V1 1 #define EXT4_KEY_DERIVATION_NONCE_SIZE 16 +#define EXT4_POLICY_FLAGS_PAD_4 0x00 +#define EXT4_POLICY_FLAGS_PAD_8 0x01 +#define EXT4_POLICY_FLAGS_PAD_16 0x02 +#define EXT4_POLICY_FLAGS_PAD_32 0x03 +#define EXT4_POLICY_FLAGS_PAD_MASK 0x03 +#define EXT4_POLICY_FLAGS_VALID 0x03 + /** * Encryption context for inode * @@ -41,7 +49,7 @@ struct ext4_encryption_context { char format; char contents_encryption_mode; char filenames_encryption_mode; - char reserved; + char flags; char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE]; char nonce[EXT4_KEY_DERIVATION_NONCE_SIZE]; } __attribute__((__packed__)); @@ -120,6 +128,7 @@ struct ext4_fname_crypto_ctx { struct crypto_hash *htfm; struct page *workpage; struct ext4_encryption_key key; + unsigned flags : 8; unsigned has_valid_key : 1; unsigned ctfm_key_is_ready : 1; }; |