/******************************************************************************
 * Icinga 2                                                                   *
 * Copyright (C) 2012-2018 Icinga Development Team (https://www.icinga.com/)  *
 *                                                                            *
 * This program is free software; you can redistribute it and/or              *
 * modify it under the terms of the GNU General Public License                *
 * as published by the Free Software Foundation; either version 2             *
 * of the License, or (at your option) any later version.                     *
 *                                                                            *
 * This program is distributed in the hope that it will be useful,            *
 * but WITHOUT ANY WARRANTY; without even the implied warranty of             *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the              *
 * GNU General Public License for more details.                               *
 *                                                                            *
 * You should have received a copy of the GNU General Public License          *
 * along with this program; if not, write to the Free Software Foundation     *
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.             *
 ******************************************************************************/

#include "base/tlsstream.hpp"
#include "base/utility.hpp"
#include "base/exception.hpp"
#include "base/logger.hpp"
#include <iostream>

#ifndef _WIN32
#	include <poll.h>
#endif /* _WIN32 */

using namespace icinga;

int TlsStream::m_SSLIndex;
bool TlsStream::m_SSLIndexInitialized = false;

/**
 * Constructor for the TlsStream class.
 *
 * @param role The role of the client.
 * @param sslContext The SSL context for the client.
 */
TlsStream::TlsStream(const Socket::Ptr& socket, const String& hostname, ConnectionRole role, const std::shared_ptr<SSL_CTX>& sslContext)
	: SocketEvents(socket, this), m_Eof(false), m_HandshakeOK(false), m_VerifyOK(true), m_ErrorCode(0),
	m_ErrorOccurred(false),  m_Socket(socket), m_Role(role), m_SendQ(new FIFO()), m_RecvQ(new FIFO()),
	m_CurrentAction(TlsActionNone), m_Retry(false), m_Shutdown(false)
{
	std::ostringstream msgbuf;
	char errbuf[120];

	m_SSL = std::shared_ptr<SSL>(SSL_new(sslContext.get()), SSL_free);

	if (!m_SSL) {
		msgbuf << "SSL_new() failed with code " << ERR_peek_error() << ", \"" << ERR_error_string(ERR_peek_error(), errbuf) << "\"";
		Log(LogCritical, "TlsStream", msgbuf.str());

		BOOST_THROW_EXCEPTION(openssl_error()
			<< boost::errinfo_api_function("SSL_new")
			<< errinfo_openssl_error(ERR_peek_error()));
	}

	if (!m_SSLIndexInitialized) {
		m_SSLIndex = SSL_get_ex_new_index(0, const_cast<char *>("TlsStream"), nullptr, nullptr, nullptr);
		m_SSLIndexInitialized = true;
	}

	SSL_set_ex_data(m_SSL.get(), m_SSLIndex, this);

	SSL_set_verify(m_SSL.get(), SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE, &TlsStream::ValidateCertificate);

	socket->MakeNonBlocking();

	SSL_set_fd(m_SSL.get(), socket->GetFD());

	if (m_Role == RoleServer)
		SSL_set_accept_state(m_SSL.get());
	else {
#ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME
		if (!hostname.IsEmpty())
			SSL_set_tlsext_host_name(m_SSL.get(), hostname.CStr());
#endif /* SSL_CTRL_SET_TLSEXT_HOSTNAME */

		SSL_set_connect_state(m_SSL.get());
	}
}

TlsStream::~TlsStream()
{
	CloseInternal(true);
}

int TlsStream::ValidateCertificate(int preverify_ok, X509_STORE_CTX *ctx)
{
	auto *ssl = static_cast<SSL *>(X509_STORE_CTX_get_ex_data(ctx, SSL_get_ex_data_X509_STORE_CTX_idx()));
	auto *stream = static_cast<TlsStream *>(SSL_get_ex_data(ssl, m_SSLIndex));

	if (!preverify_ok) {
		stream->m_VerifyOK = false;

		std::ostringstream msgbuf;
		int err = X509_STORE_CTX_get_error(ctx);
		msgbuf << "code " << err << ": " << X509_verify_cert_error_string(err);
		stream->m_VerifyError = msgbuf.str();
	}

	return 1;
}

bool TlsStream::IsVerifyOK() const
{
	return m_VerifyOK;
}

String TlsStream::GetVerifyError() const
{
	return m_VerifyError;
}

/**
 * Retrieves the X509 certficate for this client.
 *
 * @returns The X509 certificate.
 */
std::shared_ptr<X509> TlsStream::GetClientCertificate() const
{
	boost::mutex::scoped_lock lock(m_Mutex);
	return std::shared_ptr<X509>(SSL_get_certificate(m_SSL.get()), &Utility::NullDeleter);
}

/**
 * Retrieves the X509 certficate for the peer.
 *
 * @returns The X509 certificate.
 */
std::shared_ptr<X509> TlsStream::GetPeerCertificate() const
{
	boost::mutex::scoped_lock lock(m_Mutex);
	return std::shared_ptr<X509>(SSL_get_peer_certificate(m_SSL.get()), X509_free);
}

void TlsStream::OnEvent(int revents)
{
	int rc;
	size_t count;

	boost::mutex::scoped_lock lock(m_Mutex);

	if (!m_SSL)
		return;

	char buffer[64 * 1024];

	if (m_CurrentAction == TlsActionNone) {
		if (revents & (POLLIN | POLLERR | POLLHUP))
			m_CurrentAction = TlsActionRead;
		else if (m_SendQ->GetAvailableBytes() > 0 && (revents & POLLOUT))
			m_CurrentAction = TlsActionWrite;
		else {
			ChangeEvents(POLLIN);
			return;
		}
	}

	bool success = false;

	/* Clear error queue for this thread before using SSL_{read,write,do_handshake}.
	 * Otherwise SSL_*_error() does not work reliably.
	 */
	ERR_clear_error();

	switch (m_CurrentAction) {
		case TlsActionRead:
			do {
				rc = SSL_read(m_SSL.get(), buffer, sizeof(buffer));

				if (rc > 0) {
					m_RecvQ->Write(buffer, rc);
					success = true;
				}
			} while (rc > 0);

			if (success)
				m_CV.notify_all();

			break;
		case TlsActionWrite:
			count = m_SendQ->Peek(buffer, sizeof(buffer), true);

			rc = SSL_write(m_SSL.get(), buffer, count);

			if (rc > 0) {
				m_SendQ->Read(nullptr, rc, true);
				success = true;
			}

			break;
		case TlsActionHandshake:
			rc = SSL_do_handshake(m_SSL.get());

			if (rc > 0) {
				success = true;
				m_HandshakeOK = true;
				m_CV.notify_all();
			}

			break;
		default:
			VERIFY(!"Invalid TlsAction");
	}

	if (rc <= 0) {
		int err = SSL_get_error(m_SSL.get(), rc);

		switch (err) {
			case SSL_ERROR_WANT_READ:
				m_Retry = true;
				ChangeEvents(POLLIN);

				break;
			case SSL_ERROR_WANT_WRITE:
				m_Retry = true;
				ChangeEvents(POLLOUT);

				break;
			case SSL_ERROR_ZERO_RETURN:
				lock.unlock();

				Close();

				return;
			default:
				m_ErrorCode = ERR_peek_error();
				m_ErrorOccurred = true;

				if (m_ErrorCode != 0) {
					Log(LogWarning, "TlsStream")
						<< "OpenSSL error: " << ERR_error_string(m_ErrorCode, nullptr);
				} else {
					Log(LogWarning, "TlsStream", "TLS stream was disconnected.");
				}

				lock.unlock();

				Close();

				return;
		}
	}

	if (success) {
		m_CurrentAction = TlsActionNone;

		if (!m_Eof) {
			if (m_SendQ->GetAvailableBytes() > 0)
				ChangeEvents(POLLIN|POLLOUT);
			else
				ChangeEvents(POLLIN);
		}

		lock.unlock();

		while (m_RecvQ->IsDataAvailable() && IsHandlingEvents())
			SignalDataAvailable();
	}

	if (m_Shutdown && !m_SendQ->IsDataAvailable()) {
		if (!success)
			lock.unlock();

		Close();
	}
}

void TlsStream::HandleError() const
{
	if (m_ErrorOccurred) {
		BOOST_THROW_EXCEPTION(openssl_error()
			<< boost::errinfo_api_function("TlsStream::OnEvent")
			<< errinfo_openssl_error(m_ErrorCode));
	}
}

void TlsStream::Handshake()
{
	boost::mutex::scoped_lock lock(m_Mutex);

	m_CurrentAction = TlsActionHandshake;
	ChangeEvents(POLLOUT);

	while (!m_HandshakeOK && !m_ErrorOccurred && !m_Eof)
		m_CV.wait(lock);

	if (m_Eof)
		BOOST_THROW_EXCEPTION(std::runtime_error("Socket was closed during TLS handshake."));

	HandleError();
}

/**
 * Processes data for the stream.
 */
size_t TlsStream::Peek(void *buffer, size_t count, bool allow_partial)
{
	boost::mutex::scoped_lock lock(m_Mutex);

	if (!allow_partial)
		while (m_RecvQ->GetAvailableBytes() < count && !m_ErrorOccurred && !m_Eof)
			m_CV.wait(lock);

	HandleError();

	return m_RecvQ->Peek(buffer, count, true);
}

size_t TlsStream::Read(void *buffer, size_t count, bool allow_partial)
{
	boost::mutex::scoped_lock lock(m_Mutex);

	if (!allow_partial)
		while (m_RecvQ->GetAvailableBytes() < count && !m_ErrorOccurred && !m_Eof)
			m_CV.wait(lock);

	HandleError();

	return m_RecvQ->Read(buffer, count, true);
}

void TlsStream::Write(const void *buffer, size_t count)
{
	boost::mutex::scoped_lock lock(m_Mutex);

	m_SendQ->Write(buffer, count);

	ChangeEvents(POLLIN|POLLOUT);
}

void TlsStream::Shutdown()
{
	m_Shutdown = true;
	ChangeEvents(POLLOUT);
}

/**
 * Closes the stream.
 */
void TlsStream::Close()
{
	CloseInternal(false);
}

void TlsStream::CloseInternal(bool inDestructor)
{
	if (m_Eof)
		return;

	m_Eof = true;

	if (!inDestructor)
		SignalDataAvailable();

	SocketEvents::Unregister();

	Stream::Close();

	boost::mutex::scoped_lock lock(m_Mutex);

	if (!m_SSL)
		return;

	(void)SSL_shutdown(m_SSL.get());
	m_SSL.reset();

	m_Socket->Close();
	m_Socket.reset();

	m_CV.notify_all();
}

bool TlsStream::IsEof() const
{
	return m_Eof;
}

bool TlsStream::SupportsWaiting() const
{
	return true;
}

bool TlsStream::IsDataAvailable() const
{
	boost::mutex::scoped_lock lock(m_Mutex);

	return m_RecvQ->GetAvailableBytes() > 0;
}

Socket::Ptr TlsStream::GetSocket() const
{
	return m_Socket;
}