examples/platform/silabs/SilabsDeviceAttestationCreds.cpp

/*
 *
 *    Copyright (c) 2022 Project CHIP Authors
 *
 *    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.
 */
#include "SilabsDeviceAttestationCreds.h"
#include <crypto/CHIPCryptoPAL.h>
#include <lib/core/CHIPError.h>
#include <lib/support/CodeUtils.h>
#include <lib/support/Span.h>

#include "psa/crypto.h"
#include "silabs_creds.h"

extern uint8_t __attestation_credentials_base[];

namespace chip {
namespace Credentials {
namespace Silabs {

namespace {

class DeviceAttestationCredsSilabs : public DeviceAttestationCredentialsProvider
{

public:
    CHIP_ERROR GetCertificationDeclaration(MutableByteSpan & out_buffer) override
    {
        ByteSpan cd_span(((uint8_t *) __attestation_credentials_base) + SILABS_CREDENTIALS_CD_OFFSET, SILABS_CREDENTIALS_CD_SIZE);
        return CopySpanToMutableSpan(cd_span, out_buffer);
    }

    CHIP_ERROR GetFirmwareInformation(MutableByteSpan & out_firmware_info_buffer) override
    {
        // TODO: We need a real example FirmwareInformation to be populated.
        out_firmware_info_buffer.reduce_size(0);
        return CHIP_NO_ERROR;
    }

    CHIP_ERROR GetDeviceAttestationCert(MutableByteSpan & out_buffer) override
    {
        ByteSpan cert_span(((uint8_t *) __attestation_credentials_base) + SILABS_CREDENTIALS_DAC_OFFSET,
                           SILABS_CREDENTIALS_DAC_SIZE);
        return CopySpanToMutableSpan(cert_span, out_buffer);
    }

    CHIP_ERROR GetProductAttestationIntermediateCert(MutableByteSpan & out_pai_buffer) override
    {
        ByteSpan cert_span(((uint8_t *) __attestation_credentials_base) + SILABS_CREDENTIALS_PAI_OFFSET,
                           SILABS_CREDENTIALS_PAI_SIZE);
        return CopySpanToMutableSpan(cert_span, out_pai_buffer);
    }

    CHIP_ERROR SignWithDeviceAttestationKey(const ByteSpan & message_to_sign, MutableByteSpan & out_buffer) override
    {
        psa_key_id_t key_id   = SILABS_CREDENTIALS_DAC_KEY_ID;
        uint8_t signature[64] = { 0 };
        size_t signature_size = sizeof(signature);

        psa_status_t err = psa_sign_message(key_id, PSA_ALG_ECDSA(PSA_ALG_SHA_256), message_to_sign.data(), message_to_sign.size(),
                                            signature, signature_size, &signature_size);
        VerifyOrReturnError(!err, CHIP_ERROR_INTERNAL);

        return CopySpanToMutableSpan(ByteSpan(signature, signature_size), out_buffer);
    }
};

} // namespace

DeviceAttestationCredentialsProvider * GetSilabsDacProvider()
{
    static DeviceAttestationCredsSilabs dac_provider;
    return &dac_provider;
}

} // namespace Silabs
} // namespace Credentials
} // namespace chip