Function ReadFromFileOrGenerateGatewayKeys

Src/Core/BackendCommons.cpp:15–64

Obtains Gateway's encryption keys. If the key file exists, it's contents will be Base64 decoded and validated. Otherwise they will be generated. @param keysFilePath path to the keys file. @return std::tuple with a flag (true if keys were read, false if generated) and all the keys.

	/// @param keysFilePath path to the keys file.
	/// @return std::tuple with a flag (true if keys were read, false if generated) and all the keys.
	std::tuple<bool, FSecure::Crypto::SignatureKeys, FSecure::Crypto::SymmetricKey> ReadFromFileOrGenerateGatewayKeys(std::filesystem::path const& keysFilePath)
	{
		// Check if file exists.
		if (std::filesystem::exists(keysFilePath))
			try
			{
				// Parse keys.
				auto keys = json::parse(std::ifstream{ keysFilePath, std::ios::in });

				// Helper lambda to read patch entries. TODO: rewrite as a template lambda when C++20 is out.
				auto ParseEntry = [&keys](auto* typePtr, auto const& entryName) -> std::remove_pointer_t<decltype(typePtr)>
				{
					try
					{
						return cppcodec::base64_rfc4648::decode<FSecure::ByteVector>(keys[entryName].template get<std::string>());
					}
					catch (std::exception& exception)
					{
						throw std::runtime_error{ OBF("Couldn't parse ") + std::string(entryName) + OBF(" element from patch. ") + exception.what() };
					}
					catch (...)
					{
						throw std::runtime_error{ OBF("Caught an unknown exception while parsing ") + std::string(entryName) + OBF(" element from patch.") };
					}
				};

				// Parse and return keys.
				return std::make_tuple(true, FSecure::Crypto::SignatureKeys{ ParseEntry((FSecure::Crypto::PrivateSignature*)nullptr, OBF("Private signature")),
					ParseEntry((FSecure::Crypto::PublicSignature*)nullptr, OBF("Public signature")) }, ParseEntry((FSecure::Crypto::SymmetricKey*)nullptr, OBF("Broadcast key")));
			}
			catch (const std::exception & exception)
			{
				throw std::runtime_error{ OBF_STR("Incorrect key file. ") + exception.what() };
			}

		// File doesn't exist. Generate all the keys.
		auto singatures = FSecure::Crypto::GenerateSignatureKeys();
		auto broadcastKey = FSecure::Crypto::GenerateSymmetricKey();

		// Create json tree.
		auto keys = json{};
		keys[OBF("Private signature")] = cppcodec::base64_rfc4648::encode(singatures.first.ToByteVector().data(), FSecure::Crypto::PrivateSignature::Size);
		keys[OBF("Public signature")] = cppcodec::base64_rfc4648::encode(singatures.second.ToByteVector().data(), FSecure::Crypto::PublicSignature::Size);
		keys[OBF("Broadcast key")] = cppcodec::base64_rfc4648::encode(broadcastKey.ToByteVector().data(), FSecure::Crypto::SymmetricKey::Size);

		// Store them in provided file and return.
		std::ofstream{ keysFilePath, std::ios::out | std::ios::trunc } << keys.dump(4);									// dump(4) adds 4 space indentation to file.

		return std::make_tuple(false, singatures, broadcastKey);
	}

	/// Obtains Gateway's configuration.
	/// @param configurationFilePath path to the configuration file.