/*

Copyright (c) 2007-2016, Arvid Norberg
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in
      the documentation and/or other materials provided with the distribution.
    * Neither the name of the author nor the names of its
      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.

*/

#include "libtorrent/socks5_stream.hpp"
#include "libtorrent/socket_io.hpp"

using namespace std::placeholders;

namespace libtorrent
{

	namespace socks_error
	{
		boost::system::error_code make_error_code(socks_error_code e)
		{
			return error_code(e, get_socks_category());
		}
	}

	struct socks_error_category : boost::system::error_category
	{
		const char* name() const BOOST_SYSTEM_NOEXCEPT override
		{ return "socks error"; }
		std::string message(int ev) const BOOST_SYSTEM_NOEXCEPT override
		{
			static char const* messages[] =
			{
				"SOCKS no error",
				"SOCKS unsupported version",
				"SOCKS unsupported authentication method",
				"SOCKS unsupported authentication version",
				"SOCKS authentication error",
				"SOCKS username required",
				"SOCKS general failure",
				"SOCKS command not supported",
				"SOCKS no identd running",
				"SOCKS identd could not identify username"
			};

			if (ev < 0 || ev >= socks_error::num_errors) return "unknown error";
			return messages[ev];
		}
		boost::system::error_condition default_error_condition(
			int ev) const BOOST_SYSTEM_NOEXCEPT override
		{ return boost::system::error_condition(ev, *this); }
	};

	TORRENT_EXPORT boost::system::error_category& get_socks_category()
	{
		static socks_error_category socks_category;
		return socks_category;
	}

	namespace
	{
		// parse out the endpoint from a SOCKS response
		tcp::endpoint parse_endpoint(std::vector<char> const& buffer
			, int const version)
		{
			using namespace libtorrent::detail;
			char const* p = &buffer[0];
			p += 2; // version & response code
			if (version == 5)
			{
				++p; // reserved byte
				int const atyp = read_uint8(p);

				if (atyp == 1)
				{
					tcp::endpoint ret;
					ret.address(read_v4_address(p));
					ret.port(read_uint16(p));
					return ret;
				}
				else if (atyp == 3)
				{
					// we don't support resolving the endpoint address
					// if we receive a domain name, just set the remote
					// endpoint to INADDR_ANY
					return tcp::endpoint();
				}
				else if (atyp == 4)
				{
					tcp::endpoint ret;
#if TORRENT_USE_IPV6
					ret.address(read_v6_address(p));
					ret.port(read_uint16(p));
#endif
					return ret;
				}
			}
			else if (version == 4)
			{
				tcp::endpoint ret;
				ret.port(read_uint16(p));
				ret.address(read_v4_address(p));
				return ret;
			}
			TORRENT_ASSERT_FAIL();
			return tcp::endpoint();
		}
	}

	void socks5_stream::name_lookup(error_code const& e, tcp::resolver::iterator i
		, std::shared_ptr<handler_type> h)
	{
		COMPLETE_ASYNC("socks5_stream::name_lookup");
		if (handle_error(e, h)) return;

		error_code ec;
		if (!m_sock.is_open())
		{
			m_sock.open(i->endpoint().protocol(), ec);
			if (handle_error(ec, h)) return;
		}

		// TOOD: we could bind the socket here, since we know what the
		// target endpoint is of the proxy
		ADD_OUTSTANDING_ASYNC("socks5_stream::connected");
		m_sock.async_connect(i->endpoint(), std::bind(
			&socks5_stream::connected, this, _1, h));
	}

	void socks5_stream::connected(error_code const& e, std::shared_ptr<handler_type> h)
	{
		COMPLETE_ASYNC("socks5_stream::connected");
		if (handle_error(e, h)) return;

		using namespace libtorrent::detail;
		if (m_version == 5)
		{
			// send SOCKS5 authentication methods
			m_buffer.resize(m_user.empty()?3:4);
			char* p = &m_buffer[0];
			write_uint8(5, p); // SOCKS VERSION 5
			if (m_user.empty())
			{
				write_uint8(1, p); // 1 authentication method (no auth)
				write_uint8(0, p); // no authentication
			}
			else
			{
				write_uint8(2, p); // 2 authentication methods
				write_uint8(0, p); // no authentication
				write_uint8(2, p); // username/password
			}
			ADD_OUTSTANDING_ASYNC("socks5_stream::handshake1");
			async_write(m_sock, boost::asio::buffer(m_buffer)
				, std::bind(&socks5_stream::handshake1, this, _1, h));
		}
		else if (m_version == 4)
		{
			socks_connect(h);
		}
		else
		{
			(*h)(socks_error::unsupported_version);
		}
	}

	void socks5_stream::handshake1(error_code const& e, std::shared_ptr<handler_type> h)
	{
		COMPLETE_ASYNC("socks5_stream::handshake1");
		if (handle_error(e, h)) return;

		ADD_OUTSTANDING_ASYNC("socks5_stream::handshake2");
		m_buffer.resize(2);
		async_read(m_sock, boost::asio::buffer(m_buffer)
			, std::bind(&socks5_stream::handshake2, this, _1, h));
	}

	void socks5_stream::handshake2(error_code const& e, std::shared_ptr<handler_type> h)
	{
		COMPLETE_ASYNC("socks5_stream::handshake2");
		if (handle_error(e, h)) return;

		using namespace libtorrent::detail;

		char* p = &m_buffer[0];
		int version = read_uint8(p);
		int method = read_uint8(p);

		if (version < m_version)
		{
			(*h)(socks_error::unsupported_version);
			return;
		}

		if (method == 0)
		{
			socks_connect(h);
		}
		else if (method == 2)
		{
			if (m_user.empty())
			{
				(*h)(socks_error::username_required);
				return;
			}

			// start sub-negotiation
			m_buffer.resize(m_user.size() + m_password.size() + 3);
			p = &m_buffer[0];
			write_uint8(1, p);
			TORRENT_ASSERT(m_user.size() < 0x100);
			write_uint8(uint8_t(m_user.size()), p);
			write_string(m_user, p);
			TORRENT_ASSERT(m_password.size() < 0x100);
			write_uint8(uint8_t(m_password.size()), p);
			write_string(m_password, p);

			ADD_OUTSTANDING_ASYNC("socks5_stream::handshake3");
			async_write(m_sock, boost::asio::buffer(m_buffer)
				, std::bind(&socks5_stream::handshake3, this, _1, h));
		}
		else
		{
			(*h)(socks_error::unsupported_authentication_method);
			return;
		}
	}

	void socks5_stream::handshake3(error_code const& e
		, std::shared_ptr<handler_type> h)
	{
		COMPLETE_ASYNC("socks5_stream::handshake3");
		if (handle_error(e, h)) return;

		ADD_OUTSTANDING_ASYNC("socks5_stream::handshake4");
		m_buffer.resize(2);
		async_read(m_sock, boost::asio::buffer(m_buffer)
			, std::bind(&socks5_stream::handshake4, this, _1, h));
	}

	void socks5_stream::handshake4(error_code const& e
		, std::shared_ptr<handler_type> h)
	{
		COMPLETE_ASYNC("socks5_stream::handshake4");
		if (handle_error(e, h)) return;

		using namespace libtorrent::detail;

		char* p = &m_buffer[0];
		int version = read_uint8(p);
		int status = read_uint8(p);

		if (version != 1)
		{
			(*h)(socks_error::unsupported_authentication_version);
			return;
		}

		if (status != 0)
		{
			(*h)(socks_error::authentication_error);
			return;
		}

		std::vector<char>().swap(m_buffer);
		socks_connect(h);
	}

	void socks5_stream::socks_connect(std::shared_ptr<handler_type> h)
	{
		using namespace libtorrent::detail;

		if (m_version == 5)
		{
			// send SOCKS5 connect command
			m_buffer.resize(6 + (!m_dst_name.empty()
				?m_dst_name.size() + 1
				:(m_remote_endpoint.address().is_v4()?4:16)));
			char* p = &m_buffer[0];
			write_uint8(5, p); // SOCKS VERSION 5
			write_uint8(m_command, p); // CONNECT/BIND command
			write_uint8(0, p); // reserved
			if (!m_dst_name.empty())
			{
				write_uint8(3, p); // address type
				TORRENT_ASSERT(m_dst_name.size() < 0x100);
				write_uint8(uint8_t(m_dst_name.size()), p);
				std::copy(m_dst_name.begin(), m_dst_name.end(), p);
				p += m_dst_name.size();
			}
			else
			{
				// we either need a hostname or a valid endpoint
				TORRENT_ASSERT(m_command == socks5_bind
					|| m_remote_endpoint.address() != address());

				write_uint8(m_remote_endpoint.address().is_v4()?1:4, p); // address type
				write_address(m_remote_endpoint.address(), p);
			}
			write_uint16(m_remote_endpoint.port(), p);
		}
		else if (m_version == 4)
		{
			// SOCKS4 only supports IPv4
			if (!m_remote_endpoint.address().is_v4())
			{
				(*h)(boost::asio::error::address_family_not_supported);
				return;
			}
			m_buffer.resize(m_user.size() + 9);
			char* p = &m_buffer[0];
			write_uint8(4, p); // SOCKS VERSION 4
			write_uint8(m_command, p); // CONNECT/BIND command
			write_uint16(m_remote_endpoint.port(), p);
			write_uint32(m_remote_endpoint.address().to_v4().to_ulong(), p);
			std::copy(m_user.begin(), m_user.end(), p);
			p += m_user.size();
			write_uint8(0, p); // 0-terminator
		}
		else
		{
			(*h)(socks_error::unsupported_version);
			return;
		}

		ADD_OUTSTANDING_ASYNC("socks5_stream::connect1");
		async_write(m_sock, boost::asio::buffer(m_buffer)
			, std::bind(&socks5_stream::connect1, this, _1, h));
	}

	void socks5_stream::connect1(error_code const& e, std::shared_ptr<handler_type> h)
	{
		COMPLETE_ASYNC("socks5_stream::connect1");
		if (handle_error(e, h)) return;

		if (m_version == 5)
			m_buffer.resize(6 + 4); // assume an IPv4 address
		else if (m_version == 4)
			m_buffer.resize(8);

		ADD_OUTSTANDING_ASYNC("socks5_stream::connect2");
		async_read(m_sock, boost::asio::buffer(m_buffer)
			, std::bind(&socks5_stream::connect2, this, _1, h));
	}

	void socks5_stream::connect2(error_code const& e, std::shared_ptr<handler_type> h)
	{
		COMPLETE_ASYNC("socks5_stream::connect2");
		if (handle_error(e, h)) return;

		using namespace libtorrent::detail;

		char const* p = &m_buffer[0];
		int const version = read_uint8(p);
		int const response = read_uint8(p);

		if (m_version == 5)
		{
			if (version < m_version)
			{
				(*h)(socks_error::unsupported_version);
				return;
			}
			if (response != 0)
			{
				error_code ec(socks_error::general_failure, get_socks_category());
				switch (response)
				{
					case 2: ec = boost::asio::error::no_permission; break;
					case 3: ec = boost::asio::error::network_unreachable; break;
					case 4: ec = boost::asio::error::host_unreachable; break;
					case 5: ec = boost::asio::error::connection_refused; break;
					case 6: ec = boost::asio::error::timed_out; break;
					case 7: ec = socks_error::command_not_supported; break;
					case 8: ec = boost::asio::error::address_family_not_supported; break;
				}
				(*h)(ec);
				return;
			}
			p += 1; // reserved
			int const atyp = read_uint8(p);
			// read the proxy IP it was bound to (this is variable length depending
			// on address type)
			if (atyp == 1)
			{
				if (m_command == socks5_bind)
				{
					if (m_listen == 0)
					{
						m_local_endpoint = parse_endpoint(m_buffer, m_version);
						m_listen = 1;
					}
					else
					{
						m_remote_endpoint = parse_endpoint(m_buffer, m_version);
					}
					std::vector<char>().swap(m_buffer);
					(*h)(e);
				}
				else
				{
					std::vector<char>().swap(m_buffer);
					(*h)(e);
				}
				return;
			}
			int extra_bytes = 0;
			if (atyp == 4)
			{
				// IPv6
				extra_bytes = 12;
			}
			else if (atyp == 3)
			{
				// hostname with length prefix
				extra_bytes = read_uint8(p) - 3;
			}
			else
			{
				(*h)(boost::asio::error::address_family_not_supported);
				return;
			}
			m_buffer.resize(m_buffer.size() + extra_bytes);

			ADD_OUTSTANDING_ASYNC("socks5_stream::connect3");
			TORRENT_ASSERT(extra_bytes > 0);
			async_read(m_sock, boost::asio::buffer(&m_buffer[m_buffer.size() - extra_bytes], extra_bytes)
				, std::bind(&socks5_stream::connect3, this, _1, h));
		}
		else if (m_version == 4)
		{
			if (version != 0)
			{
				(*h)(socks_error::general_failure);
				return;
			}

			// access granted
			if (response == 90)
			{
				if (m_command == socks5_bind)
				{
					if (m_listen == 0)
					{
						m_local_endpoint = parse_endpoint(m_buffer, m_version);
						m_listen = 1;
					}
					else
					{
						m_remote_endpoint = parse_endpoint(m_buffer, m_version);
					}
					std::vector<char>().swap(m_buffer);
					(*h)(e);
				}
				else
				{
					std::vector<char>().swap(m_buffer);
					(*h)(e);
				}
				return;
			}

			error_code ec(socks_error::general_failure, get_socks_category());
			switch (response)
			{
				case 91: ec = boost::asio::error::connection_refused; break;
				case 92: ec = socks_error::no_identd; break;
				case 93: ec = socks_error::identd_error; break;
			}
			(*h)(ec);
		}
	}

	void socks5_stream::connect3(error_code const& e, std::shared_ptr<handler_type> h)
	{
		COMPLETE_ASYNC("socks5_stream::connect3");
		using namespace libtorrent::detail;

		if (handle_error(e, h)) return;

		if (m_command == socks5_bind)
		{
			if (m_listen == 0)
			{
				m_local_endpoint = parse_endpoint(m_buffer, m_version);
				m_listen = 1;
			}
			else
			{
				m_remote_endpoint = parse_endpoint(m_buffer, m_version);
			}
		}
		std::vector<char>().swap(m_buffer);
		(*h)(e);
	}
}