| Message ID | 20240906-wrapped-keys-v6-6-d59e61bc0cb4@linaro.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | Mike Snitzer |
| Headers | show |
| Series | Hardware wrapped key support for QCom ICE and UFS core | expand |
On 6.09.2024 8:07 PM, Bartosz Golaszewski wrote: > From: Gaurav Kashyap <quic_gaurkash@quicinc.com> > > Inline storage encryption may require deriving a software secret from > storage keys added to the kernel. > > For raw keys, this can be directly done in the kernel as keys are not > encrypted in memory. > > However, hardware wrapped keys can only be unwrapped by the HW wrapping > entity. In case of Qualcomm's wrapped key solution, this is done by the > Hardware Key Manager (HWKM) from Trustzone. > > Add a new SCM call which provides a hook to the software secret crypto > profile API provided by the block layer. > > Tested-by: Neil Armstrong <neil.armstrong@linaro.org> > Signed-off-by: Gaurav Kashyap <quic_gaurkash@quicinc.com> > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> > --- > 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 10986cb11ec0..ad3f9e9ed35d 100644 > --- a/drivers/firmware/qcom/qcom_scm.c > +++ b/drivers/firmware/qcom/qcom_scm.c > @@ -1252,6 +1252,71 @@ 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, > + }; > + > + int ret; > + > + void *wkey_buf __free(qcom_tzmem) = qcom_tzmem_alloc(__scm->mempool, > + wkey_size, > + GFP_KERNEL); > + if (!wkey_buf) > + return -ENOMEM; > + > + void *secret_buf __free(qcom_tzmem) = qcom_tzmem_alloc(__scm->mempool, > + sw_secret_size, > + GFP_KERNEL); > + if (!secret_buf) { > + ret = -ENOMEM; > + goto out_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); > + > +out_free_wrapped: Is there a reason to zero out the buffer that's being zero-allocated? Konrad > + memzero_explicit(wkey_buf, wkey_size);
On Mon, Sep 9, 2024 at 1:23 PM Konrad Dybcio <konradybcio@kernel.org> wrote: > > + > > + memzero_explicit(secret_buf, sw_secret_size); > > + > > +out_free_wrapped: > > Is there a reason to zero out the buffer that's being zero-allocated? > It's my understanding that it is a good practice in crypto routines to immediately and explicitly zero out the memory used for storing secrets. Bart
diff --git a/drivers/firmware/qcom/qcom_scm.c b/drivers/firmware/qcom/qcom_scm.c index 10986cb11ec0..ad3f9e9ed35d 100644 --- a/drivers/firmware/qcom/qcom_scm.c +++ b/drivers/firmware/qcom/qcom_scm.c @@ -1252,6 +1252,71 @@ 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, + }; + + int ret; + + void *wkey_buf __free(qcom_tzmem) = qcom_tzmem_alloc(__scm->mempool, + wkey_size, + GFP_KERNEL); + if (!wkey_buf) + return -ENOMEM; + + void *secret_buf __free(qcom_tzmem) = qcom_tzmem_alloc(__scm->mempool, + sw_secret_size, + GFP_KERNEL); + if (!secret_buf) { + ret = -ENOMEM; + goto out_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); + +out_free_wrapped: + memzero_explicit(wkey_buf, wkey_size); + + return ret; +} +EXPORT_SYMBOL_GPL(qcom_scm_derive_sw_secret); + /** * qcom_scm_hdcp_available() - Check if secure environment supports HDCP. * diff --git a/drivers/firmware/qcom/qcom_scm.h b/drivers/firmware/qcom/qcom_scm.h index 685b8f59e7a6..5a98b90ece32 100644 --- a/drivers/firmware/qcom/qcom_scm.h +++ b/drivers/firmware/qcom/qcom_scm.h @@ -127,6 +127,7 @@ struct qcom_tzmem_pool *qcom_scm_get_tzmem_pool(void); #define QCOM_SCM_SVC_ES 0x10 /* Enterprise Security */ #define QCOM_SCM_ES_INVALIDATE_ICE_KEY 0x03 #define QCOM_SCM_ES_CONFIG_SET_ICE_KEY 0x04 +#define QCOM_SCM_ES_DERIVE_SW_SECRET 0x07 #define QCOM_SCM_SVC_HDCP 0x11 #define QCOM_SCM_HDCP_INVOKE 0x01 diff --git a/include/linux/firmware/qcom/qcom_scm.h b/include/linux/firmware/qcom/qcom_scm.h index 9f14976399ab..0ef4415e2023 100644 --- a/include/linux/firmware/qcom/qcom_scm.h +++ b/include/linux/firmware/qcom/qcom_scm.h @@ -103,6 +103,8 @@ bool qcom_scm_ice_available(void); int qcom_scm_ice_invalidate_key(u32 index); int qcom_scm_ice_set_key(u32 index, const u8 *key, u32 key_size, enum qcom_scm_ice_cipher cipher, u32 data_unit_size); +int qcom_scm_derive_sw_secret(const u8 *wkey, size_t wkey_size, + u8 *sw_secret, size_t sw_secret_size); bool qcom_scm_hdcp_available(void); int qcom_scm_hdcp_req(struct qcom_scm_hdcp_req *req, u32 req_cnt, u32 *resp);