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/*
*
* Copyright (c) 2022 Project CHIP Authors
* All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* @file
* Header file that contains private definitions used by PSA crypto backend.
*
* This file should not be included directly by the application. Instead, use
* cryptographic primitives defined in CHIPCryptoPAL.h or SessionKeystore.h.
*/
#pragma once
#include "CHIPCryptoPAL.h"
#include <lib/core/DataModelTypes.h>
#include <lib/support/SafePointerCast.h>
#include <psa/crypto.h>
namespace chip {
namespace Crypto {
/**
* @def CHIP_CONFIG_CRYPTO_PSA_KEY_ID_BASE
*
* @brief
* Base of the PSA key identifier range used by Matter.
*
* Cryptographic keys stored in the PSA Internal Trusted Storage must have
* a user-assigned identifer from the range PSA_KEY_ID_USER_MIN to
* PSA_KEY_ID_USER_MAX. This option allows to override the base used to derive
* key identifiers used by Matter to avoid overlapping with other firmware
* components that also use PSA crypto API. The default value was selected
* not to interfere with OpenThread's default base that is 0x20000.
*
* Note that volatile keys like ephemeral keys used for ECDH have identifiers
* auto-assigned by the PSA backend.
*/
#ifndef CHIP_CONFIG_CRYPTO_PSA_KEY_ID_BASE
#define CHIP_CONFIG_CRYPTO_PSA_KEY_ID_BASE 0x30000
#endif // CHIP_CONFIG_CRYPTO_PSA_KEY_ID_BASE
/**
* @brief Defines subranges of the PSA key identifier space used by Matter.
*/
enum class KeyIdBase : psa_key_id_t
{
Minimum = CHIP_CONFIG_CRYPTO_PSA_KEY_ID_BASE,
Operational = Minimum, ///< Base of the PSA key ID range for Node Operational Certificate private keys
Maximum = Operational + kMaxValidFabricIndex,
};
static_assert(to_underlying(KeyIdBase::Minimum) >= PSA_KEY_ID_USER_MIN && to_underlying(KeyIdBase::Maximum) <= PSA_KEY_ID_USER_MAX,
"PSA key ID base out of allowed range");
/**
* @brief Calculates PSA key ID for Node Operational Certificate private key for the given fabric.
*/
constexpr psa_key_id_t MakeOperationalKeyId(FabricIndex fabricIndex)
{
return to_underlying(KeyIdBase::Operational) + static_cast<psa_key_id_t>(fabricIndex);
}
/**
* @brief Concrete P256 keypair context used by PSA crypto backend.
*/
struct PsaP256KeypairContext
{
psa_key_id_t key_id;
};
inline PsaP256KeypairContext & ToPsaContext(P256KeypairContext & context)
{
return *SafePointerCast<PsaP256KeypairContext *>(&context);
}
inline const PsaP256KeypairContext & ToConstPsaContext(const P256KeypairContext & context)
{
return *SafePointerCast<const PsaP256KeypairContext *>(&context);
}
/**
* @brief Wrapper for PSA key derivation API.
*/
class PsaKdf
{
public:
~PsaKdf()
{
psa_key_derivation_abort(&mOperation);
psa_destroy_key(mSecretKeyId);
}
/**
* @brief Initializes the key derivation operation.
*/
CHIP_ERROR Init(const ByteSpan & secret, const ByteSpan & salt, const ByteSpan & info);
/**
* @brief Initializes the key derivation operation.
*/
CHIP_ERROR Init(const HkdfKeyHandle & hkdfKey, const ByteSpan & salt, const ByteSpan & info);
/**
* @brief Derives raw key material from the operation.
*
* This method together with @p DeriveKeys can be called multiple times to
* derive several keys.
*
* @param[out] output Span that provides location and length for the derived key material.
*
* @retval CHIP_NO_ERROR On success.
* @retval CHIP_ERROR_INTERNAL On PSA crypto API error.
*/
CHIP_ERROR DeriveBytes(const MutableByteSpan & output);
/**
* @brief Derives a key from the operation.
*
* This method together with @p DeriveBytes can be called multiple times to
* derive several keys.
*
* @param[in] attributes Attributes of the derived key.
* @param[out] keyId PSA key ID of the derived key.
*
* @retval CHIP_NO_ERROR On success.
* @retval CHIP_ERROR_INTERNAL On PSA crypto API error.
*/
CHIP_ERROR DeriveKey(const psa_key_attributes_t & attributes, psa_key_id_t & keyId);
private:
CHIP_ERROR InitOperation(psa_key_id_t hkdfKey, const ByteSpan & salt, const ByteSpan & info);
psa_key_id_t mSecretKeyId = 0;
psa_key_derivation_operation_t mOperation = PSA_KEY_DERIVATION_OPERATION_INIT;
};
} // namespace Crypto
} // namespace chip