Re: [PATCH 05/10] scsi: ufs: prepare to support wrapped keys

Eric Biggers
2021-12-14T01:27:01Z

On Mon, Dec 06, 2021 at 02:57:20PM -0800, Gaurav Kashyap wrote:
> Adds support in ufshcd-core for wrapped keys.
> 1. Change program key vop to support wrapped key sizes by
> using blk_crypto_key directly instead of using ufs_crypto_cfg
> which is not suitable for wrapped keys.
> 2. Add derive_sw_secret vop and derive_sw_secret crypto_profile op.
>
> Signed-off-by: Gaurav Kashyap <quic_gaurkash@quicinc.com>
> ---
> drivers/scsi/ufs/ufshcd-crypto.c | 52 +++++++++++++++++++++++++-------
> drivers/scsi/ufs/ufshcd.h | 9 +++++-
> 2 files changed, 49 insertions(+), 12 deletions(-)

There will be a build error if the patch series is applied just up to here,
since this patch changes the prototype of ufs_hba_variant_ops::program_key but
doesn't update ufs_qcom which implements it.

Every intermediate step needs to be buildable, and that's more important than
keeping changes to different drivers separate.

So I recommend having one patch that does the program_key change, in both
ufshcd-crypto.c and ufs-qcom-ice.c.

Adding derive_sw_secret should be a separate patch, and maybe should be combined
with the other new methods.

> diff --git a/drivers/scsi/ufs/ufshcd-crypto.c b/drivers/scsi/ufs/ufshcd-crypto.c
> index 0ed82741f981..9d68621a0eb4 100644
> --- a/drivers/scsi/ufs/ufshcd-crypto.c
> +++ b/drivers/scsi/ufs/ufshcd-crypto.c
> @@ -18,16 +18,23 @@ static const struct ufs_crypto_alg_entry {
> };
>
> static int ufshcd_program_key(struct ufs_hba *hba,
> + const struct blk_crypto_key *key,
> const union ufs_crypto_cfg_entry *cfg, int slot)
> {
> int i;
> u32 slot_offset = hba->crypto_cfg_register + slot * sizeof(*cfg);
> int err = 0;
> + bool evict = false;
>
> ufshcd_hold(hba, false);
>
> if (hba->vops && hba->vops->program_key) {
> - err = hba->vops->program_key(hba, cfg, slot);
> + if (!(cfg->config_enable & UFS_CRYPTO_CONFIGURATION_ENABLE))
> + evict = true;
> + err = hba->vops->program_key(hba, key, slot,
> + cfg->data_unit_size,
> + cfg->crypto_cap_idx,
> + evict);
> goto out;
> }

This is a little weird because here we've already gone through the trouble of
creating a 'union ufs_crypto_cfg_entry', only to throw it away in the
->program_key case and just use the original blk_crypto_key instead.

I think that this should be refactored a bit to make it so that a
'ufs_crypto_cfg_entry' is only be initialized if program_key is not implemented.

Also, note that 'struct blk_crypto_key' includes the data unit size. So there's
no need to pass the data unit size as a separate argument to program_key.

> +static int ufshcd_crypto_derive_sw_secret(struct blk_crypto_profile *profile,
> + const u8 *wrapped_key,
> + unsigned int wrapped_key_size,
> + u8 sw_secret[BLK_CRYPTO_SW_SECRET_SIZE])
> +{
> + struct ufs_hba *hba =
> + container_of(profile, struct ufs_hba, crypto_profile);
> +
> + if (hba->vops && hba->vops->derive_secret)
> + return hba->vops->derive_secret(hba, wrapped_key,
> + wrapped_key_size, sw_secret);

There's a weird double space here.

> @@ -190,7 +215,12 @@ int ufshcd_hba_init_crypto_capabilities(struct ufs_hba *hba)
> hba->crypto_profile.ll_ops = ufshcd_crypto_ops;
> /* UFS only supports 8 bytes for any DUN */
> hba->crypto_profile.max_dun_bytes_supported = 8;
> - hba->crypto_profile.key_types_supported = BLK_CRYPTO_KEY_TYPE_STANDARD;
> + if (hba->hw_wrapped_keys_supported)
> + hba->crypto_profile.key_types_supported =
> + BLK_CRYPTO_KEY_TYPE_HW_WRAPPED;
> + else
> + hba->crypto_profile.key_types_supported =
> + BLK_CRYPTO_KEY_TYPE_STANDARD;

"hw_wrapped_keys_supported" is confusing because it doesn't just mean that
wrapped keys are supported, but also that standard keys are *not* supported.
"use_hw_wrapped_keys" would be clearer.

However, given that wrapped keys aren't specified by the UFS standard, I think
this better belongs as a bit in hba->quirks, like
UFSHCD_QUIRK_USES_WRAPPED_CRYPTO_KEYS.

> + int (*derive_secret)(struct ufs_hba *hba, const u8 *wrapped_key,
> + unsigned int wrapped_key_size,
> + u8 sw_secret[BLK_CRYPTO_SW_SECRET_SIZE]);

This probably should be called derive_sw_secret, not just derive_secret.

- Eric