On Fri, Feb 21, 2020 at 03:50:48AM -0800, Satya Tangirala wrote:
> diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
> index 65cb09fa6ead..7c157130c16a 100644
> --- a/fs/crypto/keysetup.c
> +++ b/fs/crypto/keysetup.c
> @@ -19,6 +19,8 @@ struct fscrypt_mode fscrypt_modes[] = {
> .cipher_str = "xts(aes)",
> .keysize = 64,
> .ivsize = 16,
> + .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_256_XTS,
> + .blk_crypto_dun_bytes_required = 8,
> },
> [FSCRYPT_MODE_AES_256_CTS] = {
> .friendly_name = "AES-256-CTS-CBC",
> @@ -31,6 +33,8 @@ struct fscrypt_mode fscrypt_modes[] = {
> .cipher_str = "essiv(cbc(aes),sha256)",
> .keysize = 16,
> .ivsize = 16,
> + .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV,
> + .blk_crypto_dun_bytes_required = 8,
> },
> [FSCRYPT_MODE_AES_128_CTS] = {
> .friendly_name = "AES-128-CTS-CBC",
> @@ -43,6 +47,8 @@ struct fscrypt_mode fscrypt_modes[] = {
> .cipher_str = "adiantum(xchacha12,aes)",
> .keysize = 32,
> .ivsize = 32,
> + .blk_crypto_mode = BLK_ENCRYPTION_MODE_ADIANTUM,
> + .blk_crypto_dun_bytes_required = 24,
> },
> };
The DUN bytes required is actually determined by the IV generation method too.
Currently fscrypt has the following combinations:
AES-256-XTS: 8 bytes
AES-128-CBC-ESSIV: 8 bytes
Adiantum without DIRECT_KEY: 8 bytes
Adiantum with DIRECT_KEY: 24 bytes
I.e., DIRECT_KEY is only allowed with Adiantum, but not required for it.
So it's technically incorrect to always pass dun_bytes_required=24 for Adiantum.
And it's conceivable that in the future we could add an fscrypt setting that
uses AES-256-XTS with 16 IV bytes. Such a setting wouldn't be usable with UFS
inline encryption, yet the existing AES-256-XTS settings still would.
So, how about instead of putting .blk_crypto_dun_bytes_required in the
crypto_mode table, using logic like:
dun_bytes_required = 8;
if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY)
dun_bytes_required += 16;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 3cd4fe6b845e..2331ff0464b2 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1370,6 +1370,7 @@ extern int send_sigurg(struct fown_struct *fown);
> #define SB_NODIRATIME 2048 /* Do not update directory access times */
> #define SB_SILENT 32768
> #define SB_POSIXACL (1<<16) /* VFS does not apply the umask */
> +#define SB_INLINE_CRYPT (1<<17) /* inodes in SB use blk-crypto */
> #define SB_KERNMOUNT (1<<22) /* this is a kern_mount call */
> #define SB_I_VERSION (1<<23) /* Update inode I_version field */
> #define SB_LAZYTIME (1<<25) /* Update the on-disk [acm]times lazily */
This flag probably should be called "SB_INLINECRYPT" to match the mount option,
which is "inlinecrypt" not "inline_crypt".
Also, the addition of this flag, along with the update to show_sb_opts() in
fs/proc_namespace.c which I think is needed, maybe should go in a separate patch
whose subject is prefixed with "fs: " to make it clearer to reviewers that this
part is a VFS-level change.
- Eric
