CryptoBuffer CommonCryptoCipher::DecryptBuffer(const CryptoBuffer& encryptedData)
{
if (m_failure)
{
AWS_LOGSTREAM_FATAL(CC_LOG_TAG, "Cipher not properly initialized for decryption. Aborting");
return CryptoBuffer();
}
CheckInitDecryptor();
size_t lengthWritten = encryptedData.GetLength() + (GetBlockSizeBytes() - 1);
CryptoBuffer decryptedText(static_cast<size_t>(lengthWritten));
CCStatus status = CCCryptorUpdate(m_cryptoHandle, encryptedData.GetUnderlyingData(), encryptedData.GetLength(),
decryptedText.GetUnderlyingData(), decryptedText.GetLength(), &lengthWritten);
if (status != kCCSuccess)
{
m_failure = true;
AWS_LOGSTREAM_ERROR(CC_LOG_TAG, "Decryption of buffer failed with status code: " << status);
return CryptoBuffer();
}
if (lengthWritten < decryptedText.GetLength())
{
return CryptoBuffer(decryptedText.GetUnderlyingData(), static_cast<size_t>(lengthWritten));
}
return decryptedText;
}
void SymmetricCipher::Validate()
{
assert(m_key.GetLength() >= SYMMETRIC_KEY_LENGTH);
assert(m_initializationVector.GetLength() == 0 || m_initializationVector.GetLength() >= MIN_IV_LENGTH);
if(m_key.GetLength() < SYMMETRIC_KEY_LENGTH ||
(m_initializationVector.GetLength() > 0 && m_initializationVector.GetLength() < MIN_IV_LENGTH))
{
m_failure = true;
AWS_LOGSTREAM_FATAL(LOG_TAG, "Invalid state for symmetric cipher, key length is " << m_key.GetLength() <<
" iv length is " << m_initializationVector.GetLength());
}
}
CryptoBuffer GenerateXRandomBytes(size_t lengthBytes, bool ctrMode)
{
std::shared_ptr<SecureRandomBytes> rng = CreateSecureRandomBytesImplementation();
CryptoBuffer bytes(lengthBytes);
size_t lengthToGenerate = ctrMode ? (3 * bytes.GetLength()) / 4 : bytes.GetLength();
rng->GetBytes(bytes.GetUnderlyingData(), lengthToGenerate);
if(!*rng)
{
AWS_LOGSTREAM_FATAL(LOG_TAG, "Random Number generation failed. Abort all crypto operations.");
assert(false);
abort();
}
return bytes;
}
CryptoBuffer CommonCryptoCipher::FinalizeDecryption()
{
if (m_failure)
{
AWS_LOGSTREAM_FATAL(CC_LOG_TAG,
"Cipher not properly initialized for decryption finalization. Aborting");
return CryptoBuffer();
}
CryptoBuffer finalBlock(GetBlockSizeBytes());
size_t writtenSize = static_cast<int>(finalBlock.GetLength());
CCStatus status = CCCryptorFinal(m_cryptoHandle, finalBlock.GetUnderlyingData(), finalBlock.GetLength(), &writtenSize);
if (status != kCCSuccess)
{
m_failure = true;
AWS_LOGSTREAM_ERROR(CC_LOG_TAG, "Decryption of buffer failed with status code: " << status);
return CryptoBuffer();
}
return CryptoBuffer(finalBlock.GetUnderlyingData(), writtenSize);
}