On Thu, 1 Feb 2024 at 17:11, Konrad Dybcio <konrad.dybcio@xxxxxxxxxx> wrote: > > On 28.01.2024 00:14, Gaurav Kashyap wrote: > > Inline storage encryption may require deriving a software > > secret from storage keys added to the kernel. > > > > For non-wrapped keys, this can be directly done in the kernel as > > keys are in the clear. > > > > However, hardware wrapped keys can only be unwrapped by the wrapping > > entity. In case of Qualcomm's wrapped key solution, this is done by > > the Hardware Key Manager (HWKM) from Trustzone. > > Hence, adding a new SCM call which in the end provides a hook > > to the software secret crypto profile API provided by the block > > layer. > > > > Signed-off-by: Gaurav Kashyap <quic_gaurkash@xxxxxxxxxxx> > > Tested-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx> > > --- > > drivers/firmware/qcom/qcom_scm.c | 65 ++++++++++++++++++++++++++ > > drivers/firmware/qcom/qcom_scm.h | 1 + > > include/linux/firmware/qcom/qcom_scm.h | 2 + > > 3 files changed, 68 insertions(+) > > > > diff --git a/drivers/firmware/qcom/qcom_scm.c b/drivers/firmware/qcom/qcom_scm.c > > index 7e17fd662bda..4882f8a36453 100644 > > --- a/drivers/firmware/qcom/qcom_scm.c > > +++ b/drivers/firmware/qcom/qcom_scm.c > > @@ -1220,6 +1220,71 @@ int qcom_scm_ice_set_key(u32 index, const u8 *key, u32 key_size, > > } > > EXPORT_SYMBOL_GPL(qcom_scm_ice_set_key); > > > > +/** > > + * qcom_scm_derive_sw_secret() - Derive software secret from wrapped key > > + * @wkey: the hardware wrapped key inaccessible to software > > + * @wkey_size: size of the wrapped key > > + * @sw_secret: the secret to be derived which is exactly the secret size > > + * @sw_secret_size: size of the sw_secret > > + * > > + * Derive a software secret from a hardware wrapped key for software crypto > > + * operations. > > + * For wrapped keys, the key needs to be unwrapped, in order to derive a > > + * software secret, which can be done in the hardware from a secure execution > > + * environment. > > + * > > + * For more information on sw secret, please refer to "Hardware-wrapped keys" > > + * section of Documentation/block/inline-encryption.rst. > > + * > > + * Return: 0 on success; -errno on failure. > > + */ > > +int qcom_scm_derive_sw_secret(const u8 *wkey, size_t wkey_size, > > + u8 *sw_secret, size_t sw_secret_size) > > +{ > > + struct qcom_scm_desc desc = { > > + .svc = QCOM_SCM_SVC_ES, > > + .cmd = QCOM_SCM_ES_DERIVE_SW_SECRET, > > + .arginfo = QCOM_SCM_ARGS(4, QCOM_SCM_RW, > > + QCOM_SCM_VAL, QCOM_SCM_RW, > > + QCOM_SCM_VAL), > > + .args[1] = wkey_size, > > + .args[3] = sw_secret_size, > > + .owner = ARM_SMCCC_OWNER_SIP, > > + }; > > + > > + void *secret_buf; > > + void *wkey_buf; > > + int ret; > > + > > + wkey_buf = qcom_tzmem_alloc(__scm->mempool, wkey_size, GFP_KERNEL); > > + if (!wkey_buf) > > + return -ENOMEM; > > + > > + secret_buf = qcom_tzmem_alloc(__scm->mempool, sw_secret_size, GFP_KERNEL); > > + if (!secret_buf) { > > + ret = -ENOMEM; > > + goto err_free_wrapped; > > + } > > + > > + memcpy(wkey_buf, wkey, wkey_size); > > + desc.args[0] = qcom_tzmem_to_phys(wkey_buf); > > + desc.args[2] = qcom_tzmem_to_phys(secret_buf); > > + > > + ret = qcom_scm_call(__scm->dev, &desc, NULL); > > + if (!ret) > > + memcpy(sw_secret, secret_buf, sw_secret_size); > > + > > + memzero_explicit(secret_buf, sw_secret_size); > > + qcom_tzmem_free(secret_buf); > > + > > +err_free_wrapped: > > + memzero_explicit(wkey_buf, wkey_size); > > + qcom_tzmem_free(wkey_buf); > __free(qcom_tzmem) attribute instead? > I second this. Please look at other implementations. Bart > Konrad >