lib/psa/dice_protection_environment.c - trusted-firmware-a - Git at Google

 /*
  * Copyright (c) 2024, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  *
  */

 #include <qcbor/qcbor_decode.h>
 #include <qcbor/qcbor_encode.h>
 #include <qcbor/qcbor_spiffy_decode.h>

 #include <common/debug.h>
 #include <dice.h>
 #include <dice_protection_environment.h>
 #include <psa/client.h>
 #include <psa_manifest/sid.h>

 enum dpe_command_id_t {
 	/* Standard commands */
 	DPE_GET_PROFILE = 1,
 	DPE_OPEN_SESSION = 2,
 	DPE_CLOSE_SESSION = 3,
 	DPE_SYNC_SESSION = 4,
 	DPE_EXPORT_SESSION = 5,
 	DPE_IMPORT_SESSION = 6,
 	DPE_INITIALIZE_CONTEXT = 7,
 	DPE_DERIVE_CONTEXT = 8,
 	DPE_CERTIFY_KEY = 9,
 	DPE_SIGN = 10,
 	DPE_SEAL = 11,
 	DPE_UNSEAL = 12,
 	DPE_DERIVE_SEALING_PUBLIC_KEY = 13,
 	DPE_ROTATE_CONTEXT_HANDLE = 14,
 	DPE_DESTROY_CONTEXT = 15,
 };

 enum dice_input_labels_t {
 	DICE_CODE_HASH = 1,
 	DICE_CODE_DESCRIPTOR = 2,
 	DICE_CONFIG_TYPE = 3,
 	DICE_CONFIG_VALUE = 4,
 	DICE_CONFIG_DESCRIPTOR = 5,
 	DICE_AUTHORITY_HASH = 6,
 	DICE_AUTHORITY_DESCRIPTOR = 7,
 	DICE_MODE = 8,
 	DICE_HIDDEN = 9,
 };

 enum dpe_derive_context_input_labels_t {
 	DPE_DERIVE_CONTEXT_CONTEXT_HANDLE = 1,
 	DPE_DERIVE_CONTEXT_RETAIN_PARENT_CONTEXT = 2,
 	DPE_DERIVE_CONTEXT_ALLOW_NEW_CONTEXT_TO_DERIVE = 3,
 	DPE_DERIVE_CONTEXT_CREATE_CERTIFICATE = 4,
 	DPE_DERIVE_CONTEXT_NEW_SESSION_INITIATOR_HANDSHAKE = 5,
 	DPE_DERIVE_CONTEXT_INPUT_DATA = 6,
 	DPE_DERIVE_CONTEXT_INTERNAL_INPUTS = 7,
 	DPE_DERIVE_CONTEXT_TARGET_LOCALITY = 8,
 	DPE_DERIVE_CONTEXT_RETURN_CERTIFICATE = 9,
 	DPE_DERIVE_CONTEXT_ALLOW_NEW_CONTEXT_TO_EXPORT = 10,
 	DPE_DERIVE_CONTEXT_EXPORT_CDI = 11,
 	/* enum values 256 and onwards are reserved for custom arguments */
 	DPE_DERIVE_CONTEXT_CERT_ID = 256,
 };

 enum dpe_derive_context_output_labels_t {
 	DPE_DERIVE_CONTEXT_NEW_CONTEXT_HANDLE = 1,
 	DPE_DERIVE_CONTEXT_NEW_SESSION_RESPONDER_HANDSHAKE = 2,
 	DPE_DERIVE_CONTEXT_PARENT_CONTEXT_HANDLE = 3,
 	DPE_DERIVE_CONTEXT_NEW_CERTIFICATE = 4,
 	DPE_DERIVE_CONTEXT_EXPORTED_CDI = 5,
 };

 struct derive_context_input_t {
 	int context_handle;
 	uint32_t cert_id;
 	bool retain_parent_context;
 	bool allow_new_context_to_derive;
 	bool create_certificate;
 	const DiceInputValues *dice_inputs;
 	int32_t target_locality;
 	bool return_certificate;
 	bool allow_new_context_to_export;
 	bool export_cdi;
 };

 struct derive_context_output_t {
 	int new_context_handle;
 	int new_parent_context_handle;
 	const uint8_t *new_certificate;
 	size_t new_certificate_size;
 	const uint8_t *exported_cdi;
 	size_t exported_cdi_size;
 };

 static void encode_dice_inputs(QCBOREncodeContext *encode_ctx,
 			       const DiceInputValues *input)
 {
 	/* Wrap the DICE inputs into a byte string */
 	QCBOREncode_BstrWrapInMapN(encode_ctx, DPE_DERIVE_CONTEXT_INPUT_DATA);

 	/* Inside the byte string the DICE inputs are encoded as a map */
 	QCBOREncode_OpenMap(encode_ctx);

 	QCBOREncode_AddBytesToMapN(encode_ctx, DICE_CODE_HASH,
 				  (UsefulBufC) { input->code_hash,
 						 sizeof(input->code_hash) });

 	QCBOREncode_AddBytesToMapN(encode_ctx, DICE_CODE_DESCRIPTOR,
 				   (UsefulBufC) { input->code_descriptor,
 						  input->code_descriptor_size });

 	QCBOREncode_AddInt64ToMapN(encode_ctx, DICE_CONFIG_TYPE,
 				   input->config_type);

 	if (input->config_type == kDiceConfigTypeInline) {
 		QCBOREncode_AddBytesToMapN(encode_ctx, DICE_CONFIG_VALUE,
 					   (UsefulBufC) { input->config_value,
 							  sizeof(input->config_value) });
 	} else {
 		QCBOREncode_AddBytesToMapN(encode_ctx, DICE_CONFIG_DESCRIPTOR,
 					   (UsefulBufC) { input->config_descriptor,
 							  input->config_descriptor_size });
 	}

 	QCBOREncode_AddBytesToMapN(encode_ctx, DICE_AUTHORITY_HASH,
 				   (UsefulBufC) { input->authority_hash,
 						  sizeof(input->authority_hash) });

 	QCBOREncode_AddBytesToMapN(encode_ctx, DICE_AUTHORITY_DESCRIPTOR,
 				   (UsefulBufC) { input->authority_descriptor,
 						  input->authority_descriptor_size });

 	QCBOREncode_AddInt64ToMapN(encode_ctx, DICE_MODE, input->mode);

 	QCBOREncode_AddBytesToMapN(encode_ctx, DICE_HIDDEN,
 				   (UsefulBufC) { input->hidden,
 						  sizeof(input->hidden) });

 	QCBOREncode_CloseMap(encode_ctx);
 	QCBOREncode_CloseBstrWrap2(encode_ctx, true, NULL);
 }

 static QCBORError encode_derive_context(const struct derive_context_input_t *args,
 					UsefulBuf buf,
 					UsefulBufC *encoded_buf)
 {
 	QCBOREncodeContext encode_ctx;

 	QCBOREncode_Init(&encode_ctx, buf);

 	QCBOREncode_OpenArray(&encode_ctx);
 	QCBOREncode_AddUInt64(&encode_ctx, DPE_DERIVE_CONTEXT);

 	/* Encode DeriveContext command */
 	QCBOREncode_OpenMap(&encode_ctx);
 	QCBOREncode_AddBytesToMapN(&encode_ctx,
 				   DPE_DERIVE_CONTEXT_CONTEXT_HANDLE,
 				   (UsefulBufC) { &args->context_handle,
 						  sizeof(args->context_handle) });
 	QCBOREncode_AddUInt64ToMapN(&encode_ctx,
 				    DPE_DERIVE_CONTEXT_CERT_ID,
 				    args->cert_id);
 	QCBOREncode_AddBoolToMapN(&encode_ctx,
 				  DPE_DERIVE_CONTEXT_RETAIN_PARENT_CONTEXT,
 				  args->retain_parent_context);
 	QCBOREncode_AddBoolToMapN(&encode_ctx,
 				  DPE_DERIVE_CONTEXT_ALLOW_NEW_CONTEXT_TO_DERIVE,
 				  args->allow_new_context_to_derive);
 	QCBOREncode_AddBoolToMapN(&encode_ctx,
 				  DPE_DERIVE_CONTEXT_CREATE_CERTIFICATE,
 				  args->create_certificate);
 	encode_dice_inputs(&encode_ctx, args->dice_inputs);
 	QCBOREncode_AddBytesToMapN(&encode_ctx,
 				   DPE_DERIVE_CONTEXT_TARGET_LOCALITY,
 				   (UsefulBufC) { &args->target_locality,
 						  sizeof(args->target_locality) });
 	QCBOREncode_AddBoolToMapN(&encode_ctx,
 				  DPE_DERIVE_CONTEXT_RETURN_CERTIFICATE,
 				  args->return_certificate);
 	QCBOREncode_AddBoolToMapN(&encode_ctx,
 				  DPE_DERIVE_CONTEXT_ALLOW_NEW_CONTEXT_TO_EXPORT,
 				  args->allow_new_context_to_export);
 	QCBOREncode_AddBoolToMapN(&encode_ctx,
 				  DPE_DERIVE_CONTEXT_EXPORT_CDI,
 				  args->export_cdi);
 	QCBOREncode_CloseMap(&encode_ctx);

 	QCBOREncode_CloseArray(&encode_ctx);

 	return QCBOREncode_Finish(&encode_ctx, encoded_buf);
 }

 static QCBORError decode_derive_context_response(UsefulBufC encoded_buf,
 						 struct derive_context_output_t *args,
 						 dpe_error_t *dpe_err)
 {
 	QCBORDecodeContext decode_ctx;
 	UsefulBufC out;
 	int64_t response_dpe_err;

 	QCBORDecode_Init(&decode_ctx, encoded_buf, QCBOR_DECODE_MODE_NORMAL);

 	QCBORDecode_EnterArray(&decode_ctx, NULL);

 	/* Get the error code from the response. DPE returns int32_t */
 	QCBORDecode_GetInt64(&decode_ctx, &response_dpe_err);
 	*dpe_err = (dpe_error_t)response_dpe_err;

 	/* Decode DeriveContext response if successful */
 	if (*dpe_err == DPE_NO_ERROR) {
 		QCBORDecode_EnterMap(&decode_ctx, NULL);

 		QCBORDecode_GetByteStringInMapN(&decode_ctx,
 						DPE_DERIVE_CONTEXT_NEW_CONTEXT_HANDLE,
 						&out);
 		if (out.len != sizeof(args->new_context_handle)) {
 			return QCBORDecode_Finish(&decode_ctx);
 		}
 		memcpy(&args->new_context_handle, out.ptr, out.len);

 		QCBORDecode_GetByteStringInMapN(&decode_ctx,
 						DPE_DERIVE_CONTEXT_PARENT_CONTEXT_HANDLE,
 						&out);
 		if (out.len != sizeof(args->new_parent_context_handle)) {
 			return QCBORDecode_Finish(&decode_ctx);
 		}
 		memcpy(&args->new_parent_context_handle, out.ptr, out.len);

 		QCBORDecode_GetByteStringInMapN(&decode_ctx,
 						DPE_DERIVE_CONTEXT_NEW_CERTIFICATE,
 						&out);
 		args->new_certificate = out.ptr;
 		args->new_certificate_size = out.len;

 		QCBORDecode_GetByteStringInMapN(&decode_ctx,
 						DPE_DERIVE_CONTEXT_EXPORTED_CDI,
 						&out);
 		args->exported_cdi = out.ptr;
 		args->exported_cdi_size = out.len;

 		QCBORDecode_ExitMap(&decode_ctx);
 	}

 	QCBORDecode_ExitArray(&decode_ctx);

 	return QCBORDecode_Finish(&decode_ctx);
 }

 static int32_t dpe_client_call(const char *cmd_input, size_t cmd_input_size,
 			       char *cmd_output, size_t *cmd_output_size)
 {
 	int32_t err;

 	psa_invec in_vec[] = {
 		{ cmd_input, cmd_input_size },
 	};
 	psa_outvec out_vec[] = {
 		{ cmd_output, *cmd_output_size },
 	};

 	err = psa_call(RSE_DPE_SERVICE_HANDLE, 0,
 			in_vec, IOVEC_LEN(in_vec), out_vec, IOVEC_LEN(out_vec));

 	if (err == PSA_SUCCESS) {
 		*cmd_output_size = out_vec[0].len;
 	}

 	return err;
 }

 dpe_error_t dpe_derive_context(int context_handle,
 			       uint32_t cert_id,
 			       bool retain_parent_context,
 			       bool allow_new_context_to_derive,
 			       bool create_certificate,
 			       const DiceInputValues *dice_inputs,
 			       int32_t target_locality,
 			       bool return_certificate,
 			       bool allow_new_context_to_export,
 			       bool export_cdi,
 			       int *new_context_handle,
 			       int *new_parent_context_handle,
 			       uint8_t *new_certificate_buf,
 			       size_t new_certificate_buf_size,
 			       size_t *new_certificate_actual_size,
 			       uint8_t *exported_cdi_buf,
 			       size_t exported_cdi_buf_size,
 			       size_t *exported_cdi_actual_size)
 {
 	int32_t service_err;
 	dpe_error_t dpe_err;
 	QCBORError qcbor_err;
 	UsefulBufC encoded_buf;
 	UsefulBuf_MAKE_STACK_UB(cmd_buf, 612);

 	const struct derive_context_input_t in_args = {
 		context_handle,
 		cert_id,
 		retain_parent_context,
 		allow_new_context_to_derive,
 		create_certificate,
 		dice_inputs,
 		target_locality,
 		return_certificate,
 		allow_new_context_to_export,
 		export_cdi,
 	};
 	struct derive_context_output_t out_args;

 	/*
 	 * Validate the output params here because they are not sent to the
 	 * service. Input params are validated by the DPE service.
 	 */
 	if ((new_context_handle == NULL) ||
 	    (retain_parent_context == true && new_parent_context_handle == NULL) ||
 	    (return_certificate == true &&
 		(new_certificate_buf == NULL || new_certificate_actual_size == NULL)) ||
 	    (export_cdi == true &&
 		(exported_cdi_buf == NULL || exported_cdi_actual_size == NULL))) {
 		return DPE_INVALID_ARGUMENT;
 	}

 	qcbor_err = encode_derive_context(&in_args, cmd_buf, &encoded_buf);
 	if (qcbor_err != QCBOR_SUCCESS) {
 		return DPE_INTERNAL_ERROR;
 	}

 	service_err = dpe_client_call(encoded_buf.ptr, encoded_buf.len,
 				      cmd_buf.ptr, &cmd_buf.len);
 	if (service_err != 0) {
 		return DPE_INTERNAL_ERROR;
 	}

 	qcbor_err = decode_derive_context_response(UsefulBuf_Const(cmd_buf),
 						   &out_args, &dpe_err);
 	if (qcbor_err != QCBOR_SUCCESS) {
 		return DPE_INTERNAL_ERROR;
 	} else if (dpe_err != DPE_NO_ERROR) {
 		return dpe_err;
 	}

 	/* Copy returned values into caller's memory */
 	*new_context_handle = out_args.new_context_handle;

 	if (retain_parent_context == true) {
 		*new_parent_context_handle = out_args.new_parent_context_handle;
 	}

 	if (return_certificate == true) {
 		if (out_args.new_certificate_size > new_certificate_buf_size) {
 			return DPE_INVALID_ARGUMENT;
 		}

 		memcpy(new_certificate_buf, out_args.new_certificate,
 			out_args.new_certificate_size);
 		*new_certificate_actual_size = out_args.new_certificate_size;
 	}

 	if (export_cdi == true) {
 		if (out_args.exported_cdi_size > exported_cdi_buf_size) {
 			return DPE_INVALID_ARGUMENT;
 		}

 		memcpy(exported_cdi_buf, out_args.exported_cdi,
 			out_args.exported_cdi_size);
 		*exported_cdi_actual_size = out_args.exported_cdi_size;
 	}

 	return DPE_NO_ERROR;
 }
	/*
	* Copyright (c) 2024, Arm Limited. All rights reserved.
	*
	* SPDX-License-Identifier: BSD-3-Clause
	*
	*/

	#include <qcbor/qcbor_decode.h>
	#include <qcbor/qcbor_encode.h>
	#include <qcbor/qcbor_spiffy_decode.h>

	#include <common/debug.h>
	#include <dice.h>
	#include <dice_protection_environment.h>
	#include <psa/client.h>
	#include <psa_manifest/sid.h>

	enum dpe_command_id_t {
	/* Standard commands */
	DPE_GET_PROFILE = 1,
	DPE_OPEN_SESSION = 2,
	DPE_CLOSE_SESSION = 3,
	DPE_SYNC_SESSION = 4,
	DPE_EXPORT_SESSION = 5,
	DPE_IMPORT_SESSION = 6,
	DPE_INITIALIZE_CONTEXT = 7,
	DPE_DERIVE_CONTEXT = 8,
	DPE_CERTIFY_KEY = 9,
	DPE_SIGN = 10,
	DPE_SEAL = 11,
	DPE_UNSEAL = 12,
	DPE_DERIVE_SEALING_PUBLIC_KEY = 13,
	DPE_ROTATE_CONTEXT_HANDLE = 14,
	DPE_DESTROY_CONTEXT = 15,
	};

	enum dice_input_labels_t {
	DICE_CODE_HASH = 1,
	DICE_CODE_DESCRIPTOR = 2,
	DICE_CONFIG_TYPE = 3,
	DICE_CONFIG_VALUE = 4,
	DICE_CONFIG_DESCRIPTOR = 5,
	DICE_AUTHORITY_HASH = 6,
	DICE_AUTHORITY_DESCRIPTOR = 7,
	DICE_MODE = 8,
	DICE_HIDDEN = 9,
	};

	enum dpe_derive_context_input_labels_t {
	DPE_DERIVE_CONTEXT_CONTEXT_HANDLE = 1,
	DPE_DERIVE_CONTEXT_RETAIN_PARENT_CONTEXT = 2,
	DPE_DERIVE_CONTEXT_ALLOW_NEW_CONTEXT_TO_DERIVE = 3,
	DPE_DERIVE_CONTEXT_CREATE_CERTIFICATE = 4,
	DPE_DERIVE_CONTEXT_NEW_SESSION_INITIATOR_HANDSHAKE = 5,
	DPE_DERIVE_CONTEXT_INPUT_DATA = 6,
	DPE_DERIVE_CONTEXT_INTERNAL_INPUTS = 7,
	DPE_DERIVE_CONTEXT_TARGET_LOCALITY = 8,
	DPE_DERIVE_CONTEXT_RETURN_CERTIFICATE = 9,
	DPE_DERIVE_CONTEXT_ALLOW_NEW_CONTEXT_TO_EXPORT = 10,
	DPE_DERIVE_CONTEXT_EXPORT_CDI = 11,
	/* enum values 256 and onwards are reserved for custom arguments */
	DPE_DERIVE_CONTEXT_CERT_ID = 256,
	};

	enum dpe_derive_context_output_labels_t {
	DPE_DERIVE_CONTEXT_NEW_CONTEXT_HANDLE = 1,
	DPE_DERIVE_CONTEXT_NEW_SESSION_RESPONDER_HANDSHAKE = 2,
	DPE_DERIVE_CONTEXT_PARENT_CONTEXT_HANDLE = 3,
	DPE_DERIVE_CONTEXT_NEW_CERTIFICATE = 4,
	DPE_DERIVE_CONTEXT_EXPORTED_CDI = 5,
	};

	struct derive_context_input_t {
	int context_handle;
	uint32_t cert_id;
	bool retain_parent_context;
	bool allow_new_context_to_derive;
	bool create_certificate;
	const DiceInputValues *dice_inputs;
	int32_t target_locality;
	bool return_certificate;
	bool allow_new_context_to_export;
	bool export_cdi;
	};

	struct derive_context_output_t {
	int new_context_handle;
	int new_parent_context_handle;
	const uint8_t *new_certificate;
	size_t new_certificate_size;
	const uint8_t *exported_cdi;
	size_t exported_cdi_size;
	};

	static void encode_dice_inputs(QCBOREncodeContext *encode_ctx,
	const DiceInputValues *input)
	{
	/* Wrap the DICE inputs into a byte string */
	QCBOREncode_BstrWrapInMapN(encode_ctx, DPE_DERIVE_CONTEXT_INPUT_DATA);

	/* Inside the byte string the DICE inputs are encoded as a map */
	QCBOREncode_OpenMap(encode_ctx);

	QCBOREncode_AddBytesToMapN(encode_ctx, DICE_CODE_HASH,
	(UsefulBufC) { input->code_hash,
	sizeof(input->code_hash) });

	QCBOREncode_AddBytesToMapN(encode_ctx, DICE_CODE_DESCRIPTOR,
	(UsefulBufC) { input->code_descriptor,
	input->code_descriptor_size });

	QCBOREncode_AddInt64ToMapN(encode_ctx, DICE_CONFIG_TYPE,
	input->config_type);

	if (input->config_type == kDiceConfigTypeInline) {
	QCBOREncode_AddBytesToMapN(encode_ctx, DICE_CONFIG_VALUE,
	(UsefulBufC) { input->config_value,
	sizeof(input->config_value) });
	} else {
	QCBOREncode_AddBytesToMapN(encode_ctx, DICE_CONFIG_DESCRIPTOR,
	(UsefulBufC) { input->config_descriptor,
	input->config_descriptor_size });
	}

	QCBOREncode_AddBytesToMapN(encode_ctx, DICE_AUTHORITY_HASH,
	(UsefulBufC) { input->authority_hash,
	sizeof(input->authority_hash) });

	QCBOREncode_AddBytesToMapN(encode_ctx, DICE_AUTHORITY_DESCRIPTOR,
	(UsefulBufC) { input->authority_descriptor,
	input->authority_descriptor_size });

	QCBOREncode_AddInt64ToMapN(encode_ctx, DICE_MODE, input->mode);

	QCBOREncode_AddBytesToMapN(encode_ctx, DICE_HIDDEN,
	(UsefulBufC) { input->hidden,
	sizeof(input->hidden) });

	QCBOREncode_CloseMap(encode_ctx);
	QCBOREncode_CloseBstrWrap2(encode_ctx, true, NULL);
	}

	static QCBORError encode_derive_context(const struct derive_context_input_t *args,
	UsefulBuf buf,
	UsefulBufC *encoded_buf)
	{
	QCBOREncodeContext encode_ctx;

	QCBOREncode_Init(&encode_ctx, buf);

	QCBOREncode_OpenArray(&encode_ctx);
	QCBOREncode_AddUInt64(&encode_ctx, DPE_DERIVE_CONTEXT);

	/* Encode DeriveContext command */
	QCBOREncode_OpenMap(&encode_ctx);
	QCBOREncode_AddBytesToMapN(&encode_ctx,
	DPE_DERIVE_CONTEXT_CONTEXT_HANDLE,
	(UsefulBufC) { &args->context_handle,
	sizeof(args->context_handle) });
	QCBOREncode_AddUInt64ToMapN(&encode_ctx,
	DPE_DERIVE_CONTEXT_CERT_ID,
	args->cert_id);
	QCBOREncode_AddBoolToMapN(&encode_ctx,
	DPE_DERIVE_CONTEXT_RETAIN_PARENT_CONTEXT,
	args->retain_parent_context);
	QCBOREncode_AddBoolToMapN(&encode_ctx,
	DPE_DERIVE_CONTEXT_ALLOW_NEW_CONTEXT_TO_DERIVE,
	args->allow_new_context_to_derive);
	QCBOREncode_AddBoolToMapN(&encode_ctx,
	DPE_DERIVE_CONTEXT_CREATE_CERTIFICATE,
	args->create_certificate);
	encode_dice_inputs(&encode_ctx, args->dice_inputs);
	QCBOREncode_AddBytesToMapN(&encode_ctx,
	DPE_DERIVE_CONTEXT_TARGET_LOCALITY,
	(UsefulBufC) { &args->target_locality,
	sizeof(args->target_locality) });
	QCBOREncode_AddBoolToMapN(&encode_ctx,
	DPE_DERIVE_CONTEXT_RETURN_CERTIFICATE,
	args->return_certificate);
	QCBOREncode_AddBoolToMapN(&encode_ctx,
	DPE_DERIVE_CONTEXT_ALLOW_NEW_CONTEXT_TO_EXPORT,
	args->allow_new_context_to_export);
	QCBOREncode_AddBoolToMapN(&encode_ctx,
	DPE_DERIVE_CONTEXT_EXPORT_CDI,
	args->export_cdi);
	QCBOREncode_CloseMap(&encode_ctx);

	QCBOREncode_CloseArray(&encode_ctx);

	return QCBOREncode_Finish(&encode_ctx, encoded_buf);
	}

	static QCBORError decode_derive_context_response(UsefulBufC encoded_buf,
	struct derive_context_output_t *args,
	dpe_error_t *dpe_err)
	{
	QCBORDecodeContext decode_ctx;
	UsefulBufC out;
	int64_t response_dpe_err;

	QCBORDecode_Init(&decode_ctx, encoded_buf, QCBOR_DECODE_MODE_NORMAL);

	QCBORDecode_EnterArray(&decode_ctx, NULL);

	/* Get the error code from the response. DPE returns int32_t */
	QCBORDecode_GetInt64(&decode_ctx, &response_dpe_err);
	*dpe_err = (dpe_error_t)response_dpe_err;

	/* Decode DeriveContext response if successful */
	if (*dpe_err == DPE_NO_ERROR) {
	QCBORDecode_EnterMap(&decode_ctx, NULL);

	QCBORDecode_GetByteStringInMapN(&decode_ctx,
	DPE_DERIVE_CONTEXT_NEW_CONTEXT_HANDLE,
	&out);
	if (out.len != sizeof(args->new_context_handle)) {
	return QCBORDecode_Finish(&decode_ctx);
	}
	memcpy(&args->new_context_handle, out.ptr, out.len);

	QCBORDecode_GetByteStringInMapN(&decode_ctx,
	DPE_DERIVE_CONTEXT_PARENT_CONTEXT_HANDLE,
	&out);
	if (out.len != sizeof(args->new_parent_context_handle)) {
	return QCBORDecode_Finish(&decode_ctx);
	}
	memcpy(&args->new_parent_context_handle, out.ptr, out.len);

	QCBORDecode_GetByteStringInMapN(&decode_ctx,
	DPE_DERIVE_CONTEXT_NEW_CERTIFICATE,
	&out);
	args->new_certificate = out.ptr;
	args->new_certificate_size = out.len;

	QCBORDecode_GetByteStringInMapN(&decode_ctx,
	DPE_DERIVE_CONTEXT_EXPORTED_CDI,
	&out);
	args->exported_cdi = out.ptr;
	args->exported_cdi_size = out.len;

	QCBORDecode_ExitMap(&decode_ctx);
	}

	QCBORDecode_ExitArray(&decode_ctx);

	return QCBORDecode_Finish(&decode_ctx);
	}

	static int32_t dpe_client_call(const char *cmd_input, size_t cmd_input_size,
	char cmd_output, size_t cmd_output_size)
	{
	int32_t err;

	psa_invec in_vec[] = {
	{ cmd_input, cmd_input_size },
	};
	psa_outvec out_vec[] = {
	{ cmd_output, *cmd_output_size },
	};

	err = psa_call(RSE_DPE_SERVICE_HANDLE, 0,
	in_vec, IOVEC_LEN(in_vec), out_vec, IOVEC_LEN(out_vec));

	if (err == PSA_SUCCESS) {
	*cmd_output_size = out_vec[0].len;
	}

	return err;
	}

	dpe_error_t dpe_derive_context(int context_handle,
	uint32_t cert_id,
	bool retain_parent_context,
	bool allow_new_context_to_derive,
	bool create_certificate,
	const DiceInputValues *dice_inputs,
	int32_t target_locality,
	bool return_certificate,
	bool allow_new_context_to_export,
	bool export_cdi,
	int *new_context_handle,
	int *new_parent_context_handle,
	uint8_t *new_certificate_buf,
	size_t new_certificate_buf_size,
	size_t *new_certificate_actual_size,
	uint8_t *exported_cdi_buf,
	size_t exported_cdi_buf_size,
	size_t *exported_cdi_actual_size)
	{
	int32_t service_err;
	dpe_error_t dpe_err;
	QCBORError qcbor_err;
	UsefulBufC encoded_buf;
	UsefulBuf_MAKE_STACK_UB(cmd_buf, 612);

	const struct derive_context_input_t in_args = {
	context_handle,
	cert_id,
	retain_parent_context,
	allow_new_context_to_derive,
	create_certificate,
	dice_inputs,
	target_locality,
	return_certificate,
	allow_new_context_to_export,
	export_cdi,
	};
	struct derive_context_output_t out_args;

	/*
	* Validate the output params here because they are not sent to the
	* service. Input params are validated by the DPE service.
	*/
	if ((new_context_handle == NULL) \|\|
	(retain_parent_context == true && new_parent_context_handle == NULL) \|\|
	(return_certificate == true &&
	(new_certificate_buf == NULL \|\| new_certificate_actual_size == NULL)) \|\|
	(export_cdi == true &&
	(exported_cdi_buf == NULL \|\| exported_cdi_actual_size == NULL))) {
	return DPE_INVALID_ARGUMENT;
	}

	qcbor_err = encode_derive_context(&in_args, cmd_buf, &encoded_buf);
	if (qcbor_err != QCBOR_SUCCESS) {
	return DPE_INTERNAL_ERROR;
	}

	service_err = dpe_client_call(encoded_buf.ptr, encoded_buf.len,
	cmd_buf.ptr, &cmd_buf.len);
	if (service_err != 0) {
	return DPE_INTERNAL_ERROR;
	}

	qcbor_err = decode_derive_context_response(UsefulBuf_Const(cmd_buf),
	&out_args, &dpe_err);
	if (qcbor_err != QCBOR_SUCCESS) {
	return DPE_INTERNAL_ERROR;
	} else if (dpe_err != DPE_NO_ERROR) {
	return dpe_err;
	}

	/* Copy returned values into caller's memory */
	*new_context_handle = out_args.new_context_handle;

	if (retain_parent_context == true) {
	*new_parent_context_handle = out_args.new_parent_context_handle;
	}

	if (return_certificate == true) {
	if (out_args.new_certificate_size > new_certificate_buf_size) {
	return DPE_INVALID_ARGUMENT;
	}

	memcpy(new_certificate_buf, out_args.new_certificate,
	out_args.new_certificate_size);
	*new_certificate_actual_size = out_args.new_certificate_size;
	}

	if (export_cdi == true) {
	if (out_args.exported_cdi_size > exported_cdi_buf_size) {
	return DPE_INVALID_ARGUMENT;
	}

	memcpy(exported_cdi_buf, out_args.exported_cdi,
	out_args.exported_cdi_size);
	*exported_cdi_actual_size = out_args.exported_cdi_size;
	}

	return DPE_NO_ERROR;
	}