src/platform/ESP32/ESP32SecureCertDACProvider.cpp

/*
 *
 *    Copyright (c) 2023 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 <credentials/CHIPCert.h>
#include <crypto/CHIPCryptoPAL.h>
#include <esp_fault.h>
#include <esp_log.h>
#include <esp_secure_cert_read.h>
#include <platform/ESP32/ESP32Config.h>
#include <platform/ESP32/ESP32SecureCertDACProvider.h>

#define TAG "dac_provider"

#if CONFIG_SEC_CERT_DAC_PROVIDER

namespace chip {
namespace DeviceLayer {

using namespace chip::Credentials;
using namespace chip::DeviceLayer::Internal;

namespace {
static constexpr uint32_t kDACPrivateKeySize = 32;
static constexpr uint32_t kDACPublicKeySize  = 65;
static constexpr uint8_t kPrivKeyOffset      = 7;
static constexpr uint8_t kPubKeyOffset       = 56;

CHIP_ERROR LoadKeypairFromRaw(ByteSpan privateKey, ByteSpan publicKey, Crypto::P256Keypair & keypair)
{
    Crypto::P256SerializedKeypair serializedKeypair;
    ReturnErrorOnFailure(serializedKeypair.SetLength(privateKey.size() + publicKey.size()));
    memcpy(serializedKeypair.Bytes(), publicKey.data(), publicKey.size());
    memcpy(serializedKeypair.Bytes() + publicKey.size(), privateKey.data(), privateKey.size());
    return keypair.Deserialize(serializedKeypair);
}
} // namespace

CHIP_ERROR ESP32SecureCertDACProvider ::GetCertificationDeclaration(MutableByteSpan & outBuffer)
{
    size_t certSize;
    ReturnErrorOnFailure(
        ESP32Config::ReadConfigValueBin(ESP32Config::kConfigKey_CertDeclaration, outBuffer.data(), outBuffer.size(), certSize));
    outBuffer.reduce_size(certSize);
    return CHIP_NO_ERROR;
}

CHIP_ERROR ESP32SecureCertDACProvider ::GetFirmwareInformation(MutableByteSpan & out_firmware_info_buffer)
{
    // We do not provide any FirmwareInformation.
    out_firmware_info_buffer.reduce_size(0);
    return CHIP_NO_ERROR;
}

CHIP_ERROR ESP32SecureCertDACProvider ::GetDeviceAttestationCert(MutableByteSpan & outBuffer)
{
    char * dac_cert  = NULL;
    uint32_t dac_len = 0;

    esp_err_t err = esp_secure_cert_get_device_cert(&dac_cert, &dac_len);
    if (err == ESP_OK && dac_cert != NULL && dac_len != 0)
    {
        ESP_FAULT_ASSERT(err == ESP_OK && dac_cert != NULL && dac_len != 0);
        VerifyOrReturnError(dac_len <= kMaxDERCertLength, CHIP_ERROR_UNSUPPORTED_CERT_FORMAT,
                            esp_secure_cert_free_ca_cert(dac_cert));
        VerifyOrReturnError(dac_len <= outBuffer.size(), CHIP_ERROR_BUFFER_TOO_SMALL, esp_secure_cert_free_ca_cert(dac_cert));
        memcpy(outBuffer.data(), dac_cert, outBuffer.size());
        outBuffer.reduce_size(dac_len);
        esp_secure_cert_free_device_cert(dac_cert);
        return CHIP_NO_ERROR;
    }

    ESP_LOGE(TAG, "esp_secure_cert_get_device_cert failed err:%d", err);
    return CHIP_ERROR_INCORRECT_STATE;
}

CHIP_ERROR ESP32SecureCertDACProvider ::GetProductAttestationIntermediateCert(MutableByteSpan & outBuffer)
{
    char * pai_cert  = NULL;
    uint32_t pai_len = 0;
    esp_err_t err    = esp_secure_cert_get_ca_cert(&pai_cert, &pai_len);
    if (err == ESP_OK && pai_cert != NULL && pai_len != 0)
    {
        ESP_FAULT_ASSERT(err == ESP_OK && pai_cert != NULL && pai_len != 0);
        VerifyOrReturnError(pai_len <= kMaxDERCertLength, CHIP_ERROR_UNSUPPORTED_CERT_FORMAT,
                            esp_secure_cert_free_ca_cert(pai_cert));
        VerifyOrReturnError(pai_len <= outBuffer.size(), CHIP_ERROR_BUFFER_TOO_SMALL, esp_secure_cert_free_ca_cert(pai_cert));
        memcpy(outBuffer.data(), pai_cert, outBuffer.size());
        outBuffer.reduce_size(pai_len);
        esp_secure_cert_free_ca_cert(pai_cert);
        return CHIP_NO_ERROR;
    }

    ESP_LOGE(TAG, "esp_secure_cert_get_ca_cert failed err:%d", err);
    return CHIP_ERROR_INCORRECT_STATE;
}

CHIP_ERROR ESP32SecureCertDACProvider ::SignWithDeviceAttestationKey(const ByteSpan & messageToSign,
                                                                     MutableByteSpan & outSignBuffer)
{
    Crypto::P256ECDSASignature signature;
    Crypto::P256Keypair keypair;
    char * sc_keypair       = NULL;
    uint32_t sc_keypair_len = 0;

    VerifyOrReturnError(IsSpanUsable(outSignBuffer), CHIP_ERROR_INVALID_ARGUMENT);
    VerifyOrReturnError(IsSpanUsable(messageToSign), CHIP_ERROR_INVALID_ARGUMENT);
    VerifyOrReturnError(outSignBuffer.size() >= signature.Capacity(), CHIP_ERROR_BUFFER_TOO_SMALL);

    esp_err_t err = esp_secure_cert_get_priv_key(&sc_keypair, &sc_keypair_len);
    if (err == ESP_OK && sc_keypair != NULL && sc_keypair_len != 0)
    {
        ESP_FAULT_ASSERT(err == ESP_OK && sc_keypair != NULL && sc_keypair_len != 0);
        CHIP_ERROR chipError =
            LoadKeypairFromRaw(ByteSpan(reinterpret_cast<const uint8_t *>(sc_keypair + kPrivKeyOffset), kDACPrivateKeySize),
                               ByteSpan(reinterpret_cast<const uint8_t *>(sc_keypair + kPubKeyOffset), kDACPublicKeySize), keypair);
        VerifyOrReturnError(chipError == CHIP_NO_ERROR, chipError, esp_secure_cert_free_priv_key(sc_keypair));

        chipError = keypair.ECDSA_sign_msg(messageToSign.data(), messageToSign.size(), signature);
        VerifyOrReturnError(chipError == CHIP_NO_ERROR, chipError, esp_secure_cert_free_priv_key(sc_keypair));

        esp_secure_cert_free_priv_key(sc_keypair);
        chipError = CopySpanToMutableSpan(ByteSpan{ signature.ConstBytes(), signature.Length() }, outSignBuffer);
        return chipError;
    }

    ESP_LOGE(TAG, "esp_secure_cert_get_priv_key failed err:%d", err);
    return CHIP_ERROR_INCORRECT_STATE;
}

} // namespace DeviceLayer
} // namespace chip

#endif // CONFIG_SEC_CERT_DAC_PROVIDER