firmware: qcom: scm: add calls for wrapped key support

Add helper functions for the SCM calls required to support
hardware-wrapped inline storage encryption keys. These SCM calls manage
wrapped keys via Qualcomm's Hardware Key Manager (HWKM), which can only
be accessed from TrustZone.

QCOM_SCM_ES_GENERATE_ICE_KEY and QCOM_SCM_ES_IMPORT_ICE_KEY create a new
long-term wrapped key, with the former making the hardware generate the
key and the latter importing a raw key. QCOM_SCM_ES_PREPARE_ICE_KEY
converts the key to ephemerally-wrapped form so that it can be used for
inline storage encryption. These are planned to be wired up to new
ioctls via the blk-crypto framework; see the proposed documentation for
the hardware-wrapped keys feature for more information.

Similarly there's also QCOM_SCM_ES_DERIVE_SW_SECRET which derives a
"software secret" from an ephemerally-wrapped key and will be wired up
to the corresponding operation in the blk_crypto_profile.

These will all be used by the ICE driver in drivers/soc/qcom/ice.c.

[EB: merged related patches, fixed error handling, fixed naming, fixed
docs for size parameters, fixed qcom_scm_has_wrapped_key_support(),
improved comments, improved commit message.]

Signed-off-by: Gaurav Kashyap <[e-mail]>
Signed-off-by: Bartosz Golaszewski <[e-mail]>
Signed-off-by: Eric Biggers <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Bjorn Andersson <[e-mail]>

drivers/firmware/qcom/qcom_scm.c

···
 }
 EXPORT_SYMBOL_GPL(qcom_scm_ice_set_key);
 
+bool qcom_scm_has_wrapped_key_support(void)
+{
+	return __qcom_scm_is_call_available(__scm->dev, QCOM_SCM_SVC_ES,
+					    QCOM_SCM_ES_DERIVE_SW_SECRET) &&
+	       __qcom_scm_is_call_available(__scm->dev, QCOM_SCM_SVC_ES,
+					    QCOM_SCM_ES_GENERATE_ICE_KEY) &&
+	       __qcom_scm_is_call_available(__scm->dev, QCOM_SCM_SVC_ES,
+					    QCOM_SCM_ES_PREPARE_ICE_KEY) &&
+	       __qcom_scm_is_call_available(__scm->dev, QCOM_SCM_SVC_ES,
+					    QCOM_SCM_ES_IMPORT_ICE_KEY);
+}
+EXPORT_SYMBOL_GPL(qcom_scm_has_wrapped_key_support);
+
+/**
+ * qcom_scm_derive_sw_secret() - Derive software secret from wrapped key
+ * @eph_key: an ephemerally-wrapped key
+ * @eph_key_size: size of @eph_key in bytes
+ * @sw_secret: output buffer for the software secret
+ * @sw_secret_size: size of the software secret to derive in bytes
+ *
+ * Derive a software secret from an ephemerally-wrapped key for software crypto
+ * operations.  This is done by calling into the secure execution environment,
+ * which then calls into the hardware to unwrap and derive the secret.
+ *
+ * For more information on sw_secret, see the "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 *eph_key, size_t eph_key_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),
+		.owner = ARM_SMCCC_OWNER_SIP,
+	};
+	int ret;
+
+	void *eph_key_buf __free(qcom_tzmem) = qcom_tzmem_alloc(__scm->mempool,
+								eph_key_size,
+								GFP_KERNEL);
+	if (!eph_key_buf)
+		return -ENOMEM;
+
+	void *sw_secret_buf __free(qcom_tzmem) = qcom_tzmem_alloc(__scm->mempool,
+								  sw_secret_size,
+								  GFP_KERNEL);
+	if (!sw_secret_buf)
+		return -ENOMEM;
+
+	memcpy(eph_key_buf, eph_key, eph_key_size);
+	desc.args[0] = qcom_tzmem_to_phys(eph_key_buf);
+	desc.args[1] = eph_key_size;
+	desc.args[2] = qcom_tzmem_to_phys(sw_secret_buf);
+	desc.args[3] = sw_secret_size;
+
+	ret = qcom_scm_call(__scm->dev, &desc, NULL);
+	if (!ret)
+		memcpy(sw_secret, sw_secret_buf, sw_secret_size);
+
+	memzero_explicit(eph_key_buf, eph_key_size);
+	memzero_explicit(sw_secret_buf, sw_secret_size);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(qcom_scm_derive_sw_secret);
+
+/**
+ * qcom_scm_generate_ice_key() - Generate a wrapped key for storage encryption
+ * @lt_key: output buffer for the long-term wrapped key
+ * @lt_key_size: size of @lt_key in bytes.  Must be the exact wrapped key size
+ *		 used by the SoC.
+ *
+ * Generate a key using the built-in HW module in the SoC.  The resulting key is
+ * returned wrapped with the platform-specific Key Encryption Key.
+ *
+ * Return: 0 on success; -errno on failure.
+ */
+int qcom_scm_generate_ice_key(u8 *lt_key, size_t lt_key_size)
+{
+	struct qcom_scm_desc desc = {
+		.svc = QCOM_SCM_SVC_ES,
+		.cmd =  QCOM_SCM_ES_GENERATE_ICE_KEY,
+		.arginfo = QCOM_SCM_ARGS(2, QCOM_SCM_RW, QCOM_SCM_VAL),
+		.owner = ARM_SMCCC_OWNER_SIP,
+	};
+	int ret;
+
+	void *lt_key_buf __free(qcom_tzmem) = qcom_tzmem_alloc(__scm->mempool,
+							       lt_key_size,
+							       GFP_KERNEL);
+	if (!lt_key_buf)
+		return -ENOMEM;
+
+	desc.args[0] = qcom_tzmem_to_phys(lt_key_buf);
+	desc.args[1] = lt_key_size;
+
+	ret = qcom_scm_call(__scm->dev, &desc, NULL);
+	if (!ret)
+		memcpy(lt_key, lt_key_buf, lt_key_size);
+
+	memzero_explicit(lt_key_buf, lt_key_size);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(qcom_scm_generate_ice_key);
+
+/**
+ * qcom_scm_prepare_ice_key() - Re-wrap a key with the per-boot ephemeral key
+ * @lt_key: a long-term wrapped key
+ * @lt_key_size: size of @lt_key in bytes
+ * @eph_key: output buffer for the ephemerally-wrapped key
+ * @eph_key_size: size of @eph_key in bytes.  Must be the exact wrapped key size
+ *		  used by the SoC.
+ *
+ * Given a long-term wrapped key, re-wrap it with the per-boot ephemeral key for
+ * added protection.  The resulting key will only be valid for the current boot.
+ *
+ * Return: 0 on success; -errno on failure.
+ */
+int qcom_scm_prepare_ice_key(const u8 *lt_key, size_t lt_key_size,
+			     u8 *eph_key, size_t eph_key_size)
+{
+	struct qcom_scm_desc desc = {
+		.svc = QCOM_SCM_SVC_ES,
+		.cmd =  QCOM_SCM_ES_PREPARE_ICE_KEY,
+		.arginfo = QCOM_SCM_ARGS(4, QCOM_SCM_RO, QCOM_SCM_VAL,
+					 QCOM_SCM_RW, QCOM_SCM_VAL),
+		.owner = ARM_SMCCC_OWNER_SIP,
+	};
+	int ret;
+
+	void *lt_key_buf __free(qcom_tzmem) = qcom_tzmem_alloc(__scm->mempool,
+							       lt_key_size,
+							       GFP_KERNEL);
+	if (!lt_key_buf)
+		return -ENOMEM;
+
+	void *eph_key_buf __free(qcom_tzmem) = qcom_tzmem_alloc(__scm->mempool,
+								eph_key_size,
+								GFP_KERNEL);
+	if (!eph_key_buf)
+		return -ENOMEM;
+
+	memcpy(lt_key_buf, lt_key, lt_key_size);
+	desc.args[0] = qcom_tzmem_to_phys(lt_key_buf);
+	desc.args[1] = lt_key_size;
+	desc.args[2] = qcom_tzmem_to_phys(eph_key_buf);
+	desc.args[3] = eph_key_size;
+
+	ret = qcom_scm_call(__scm->dev, &desc, NULL);
+	if (!ret)
+		memcpy(eph_key, eph_key_buf, eph_key_size);
+
+	memzero_explicit(lt_key_buf, lt_key_size);
+	memzero_explicit(eph_key_buf, eph_key_size);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(qcom_scm_prepare_ice_key);
+
+/**
+ * qcom_scm_import_ice_key() - Import key for storage encryption
+ * @raw_key: the raw key to import
+ * @raw_key_size: size of @raw_key in bytes
+ * @lt_key: output buffer for the long-term wrapped key
+ * @lt_key_size: size of @lt_key in bytes.  Must be the exact wrapped key size
+ *		 used by the SoC.
+ *
+ * Import a raw key and return a long-term wrapped key.  Uses the SoC's HWKM to
+ * wrap the raw key using the platform-specific Key Encryption Key.
+ *
+ * Return: 0 on success; -errno on failure.
+ */
+int qcom_scm_import_ice_key(const u8 *raw_key, size_t raw_key_size,
+			    u8 *lt_key, size_t lt_key_size)
+{
+	struct qcom_scm_desc desc = {
+		.svc = QCOM_SCM_SVC_ES,
+		.cmd =  QCOM_SCM_ES_IMPORT_ICE_KEY,
+		.arginfo = QCOM_SCM_ARGS(4, QCOM_SCM_RO, QCOM_SCM_VAL,
+					 QCOM_SCM_RW, QCOM_SCM_VAL),
+		.owner = ARM_SMCCC_OWNER_SIP,
+	};
+	int ret;
+
+	void *raw_key_buf __free(qcom_tzmem) = qcom_tzmem_alloc(__scm->mempool,
+								raw_key_size,
+								GFP_KERNEL);
+	if (!raw_key_buf)
+		return -ENOMEM;
+
+	void *lt_key_buf __free(qcom_tzmem) = qcom_tzmem_alloc(__scm->mempool,
+							       lt_key_size,
+							       GFP_KERNEL);
+	if (!lt_key_buf)
+		return -ENOMEM;
+
+	memcpy(raw_key_buf, raw_key, raw_key_size);
+	desc.args[0] = qcom_tzmem_to_phys(raw_key_buf);
+	desc.args[1] = raw_key_size;
+	desc.args[2] = qcom_tzmem_to_phys(lt_key_buf);
+	desc.args[3] = lt_key_size;
+
+	ret = qcom_scm_call(__scm->dev, &desc, NULL);
+	if (!ret)
+		memcpy(lt_key, lt_key_buf, lt_key_size);
+
+	memzero_explicit(raw_key_buf, raw_key_size);
+	memzero_explicit(lt_key_buf, lt_key_size);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(qcom_scm_import_ice_key);
+
 /**
  * qcom_scm_hdcp_available() - Check if secure environment supports HDCP.
  *

drivers/firmware/qcom/qcom_scm.h

···
 #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_ES_GENERATE_ICE_KEY	0x08
+#define QCOM_SCM_ES_PREPARE_ICE_KEY	0x09
+#define QCOM_SCM_ES_IMPORT_ICE_KEY	0x0a
 
 #define QCOM_SCM_SVC_HDCP		0x11
 #define QCOM_SCM_HDCP_INVOKE		0x01

include/linux/firmware/qcom/qcom_scm.h

···
 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);
+bool qcom_scm_has_wrapped_key_support(void);
+int qcom_scm_derive_sw_secret(const u8 *eph_key, size_t eph_key_size,
+			      u8 *sw_secret, size_t sw_secret_size);
+int qcom_scm_generate_ice_key(u8 *lt_key, size_t lt_key_size);
+int qcom_scm_prepare_ice_key(const u8 *lt_key, size_t lt_key_size,
+			     u8 *eph_key, size_t eph_key_size);
+int qcom_scm_import_ice_key(const u8 *raw_key, size_t raw_key_size,
+			    u8 *lt_key, size_t lt_key_size);
 
 bool qcom_scm_hdcp_available(void);
 int qcom_scm_hdcp_req(struct qcom_scm_hdcp_req *req, u32 req_cnt, u32 *resp);