text: /*
  
  Copyright (c) 2003-2016, 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/config.hpp"
  #include "libtorrent/gzip.hpp"
  #include "libtorrent/socket_io.hpp"
  
  #include "libtorrent/aux_/disable_warnings_push.hpp"
  
  #include <utility>
  #include <vector>
  #include <list>
  #include <cctype>
  #include <algorithm>
  
  #include <boost/bind.hpp>
  
  #include "libtorrent/aux_/disable_warnings_pop.hpp"
  
  #include "libtorrent/tracker_manager.hpp"
  #include "libtorrent/http_tracker_connection.hpp"
  #include "libtorrent/http_connection.hpp"
  #include "libtorrent/entry.hpp"
  #include "libtorrent/bencode.hpp"
  #include "libtorrent/torrent.hpp"
  #include "libtorrent/io.hpp"
  #include "libtorrent/socket.hpp"
  #include "libtorrent/broadcast_socket.hpp" // for is_local
  #include "libtorrent/string_util.hpp" // for is_i2p_url
  #include "libtorrent/aux_/session_settings.hpp"
  #include "libtorrent/resolver_interface.hpp"
  #include "libtorrent/ip_filter.hpp"
  
  using namespace libtorrent;
  
  namespace libtorrent
  {
  	http_tracker_connection::http_tracker_connection(
  		io_service& ios
  		, tracker_manager& man
  		, tracker_request const& req
  		, boost::weak_ptr<request_callback> c)
  		: tracker_connection(man, req, ios, std::move(c))
  		, m_man(man)
  	{}
  
  	void http_tracker_connection::start()
  	{
  		std::string url = tracker_req().url;
  
  		if (0 != (tracker_req().kind & tracker_request::scrape_request))
  		{
  			// find and replace "announce" with "scrape"
  			// in request
  
  			std::size_t pos = url.find("announce");
  			if (pos == std::string::npos)
  			{
  				tracker_connection::fail(errors::scrape_not_available);
  				return;
  			}
  			url.replace(pos, 8, "scrape");
  		}
  
  #if TORRENT_USE_I2P
  		bool const i2p = is_i2p_url(url);
  #else
  		static const bool i2p = false;
  #endif
  
  		aux::session_settings const& settings = m_man.settings();
  
  		// if request-string already contains
  		// some parameters, append an ampersand instead
  		// of a question mark
  		size_t arguments_start = url.find('?');
  		if (arguments_start != std::string::npos)
  			url += "&";
  		else
  			url += "?";
  
  		url += "info_hash=";
  		url += escape_string(tracker_req().info_hash.data(), 20);
  
  		if (0 == (tracker_req().kind & tracker_request::scrape_request))
  		{
  			static const char* event_string[] = {"completed", "started", "stopped", "paused"};
  
  			char str[1024];
  			const bool stats = tracker_req().send_stats;
  			snprintf(str, sizeof(str)
  				, "&peer_id=%s"
  				"&port=%d"
  				"&uploaded=%" PRId64
  				"&downloaded=%" PRId64
  				"&left=%" PRId64
  				"&corrupt=%" PRId64
  				"&key=%08X"
  				"%s%s" // event
  				"&numwant=%d"
  				"&compact=1"
  				"&no_peer_id=1"
  				, escape_string(tracker_req().pid.data(), 20).c_str()
  				// the i2p tracker seems to verify that the port is not 0,
  				// even though it ignores it otherwise
  				, i2p ? 1 : tracker_req().listen_port
  				, stats ? tracker_req().uploaded : 0
  				, stats ? tracker_req().downloaded : 0
  				, stats ? tracker_req().left : 0
  				, stats ? tracker_req().corrupt : 0
  				, tracker_req().key
  				, (tracker_req().event != tracker_request::none) ? "&event=" : ""
  				, (tracker_req().event != tracker_request::none) ? event_string[tracker_req().event - 1] : ""
  				, tracker_req().num_want);
  			url += str;
  #if !defined(TORRENT_DISABLE_ENCRYPTION) && !defined(TORRENT_DISABLE_EXTENSIONS)
  			if (settings.get_int(settings_pack::in_enc_policy) != settings_pack::pe_disabled
  				&& settings.get_bool(settings_pack::announce_crypto_support))
  				url += "&supportcrypto=1";
  #endif
  			if (stats && settings.get_bool(settings_pack::report_redundant_bytes))
  			{
  				url += "&redundant=";
  				url += to_string(tracker_req().redundant).elems;
  			}
  			if (!tracker_req().trackerid.empty())
  			{
  				std::string id = tracker_req().trackerid;
  				url += "&trackerid=";
  				url += escape_string(id.c_str(), id.length());
  			}
  
  #if TORRENT_USE_I2P
  			if (i2p && tracker_req().i2pconn)
  			{
  				if (tracker_req().i2pconn->local_endpoint().empty())
  				{
  					fail(errors::no_i2p_endpoint, -1, "Waiting for i2p acceptor from SAM bridge", 5);
  					return;
  				}
  				else
  				{
  					url += "&ip=" + tracker_req ().i2pconn->local_endpoint () + ".i2p";
  				}
  			}
  			else
  #endif
  			if (!settings.get_bool(settings_pack::anonymous_mode))
  			{
  				const std::string& announce_ip = settings.get_str(settings_pack::announce_ip);
  				if (!announce_ip.empty())
  				{
  					url += "&ip=" + escape_string(announce_ip.c_str(), announce_ip.size());
  				}
  			}
  		}
  
  #if TORRENT_USE_IPV6
  		if (tracker_req().ipv6 != address_v6() && !i2p)
  		{
  			error_code err;
  			std::string const ip = tracker_req().ipv6.to_string(err);
  			if (!err)
  			{
  				url += "&ipv6=";
  				url += escape_string(ip.c_str(), ip.size());
  			}
  		}
  #endif
  
  		m_tracker_connection.reset(new http_connection(get_io_service(), m_man.host_resolver()
  			, boost::bind(&http_tracker_connection::on_response, shared_from_this(), _1, _2, _3, _4)
  			, true, settings.get_int(settings_pack::max_http_recv_buffer_size)
  			, boost::bind(&http_tracker_connection::on_connect, shared_from_this(), _1)
  			, boost::bind(&http_tracker_connection::on_filter, shared_from_this(), _1, _2)
  #ifdef TORRENT_USE_OPENSSL
  			, tracker_req().ssl_ctx
  #endif
  			));
  
  		int const timeout = tracker_req().event==tracker_request::stopped
  			?settings.get_int(settings_pack::stop_tracker_timeout)
  			:settings.get_int(settings_pack::tracker_completion_timeout);
  
  		// in anonymous mode we omit the user agent to mitigate fingerprinting of
  		// the client. Private torrents is an exception because some private
  		// trackers may requre the user agent
  		std::string const user_agent = settings.get_bool(settings_pack::anonymous_mode)
  			&& !tracker_req().private_torrent ? "" : settings.get_str(settings_pack::user_agent);
  
  		// when sending stopped requests, prefer the cached DNS entry
  		// to avoid being blocked for slow or failing responses. Chances
  		// are that we're shutting down, and this should be a best-effort
  		// attempt. It's not worth stalling shutdown.
  		aux::proxy_settings ps(settings);
  		m_tracker_connection->get(url, seconds(timeout)
  			, tracker_req().event == tracker_request::stopped ? 2 : 1
  			, ps.proxy_tracker_connections ? &ps : NULL
  			, 5, user_agent, tracker_req().bind_ip
  			, tracker_req().event == tracker_request::stopped
  				? resolver_interface::cache_only : 0
  				| resolver_interface::abort_on_shutdown
  #ifndef TORRENT_NO_DEPRECATE
  			, tracker_req().auth
  #else
  			, ""
  #endif
  #if TORRENT_USE_I2P
  			, tracker_req().i2pconn
  #endif
  			);
  
  		// the url + 100 estimated header size
  		sent_bytes(url.size() + 100);
  
  #ifndef TORRENT_DISABLE_LOGGING
  
  		boost::shared_ptr<request_callback> cb = requester();
  		if (cb)
  		{
  			cb->debug_log("==> TRACKER_REQUEST [ url: %s ]", url.c_str());
  		}
  #endif
  	}
  
  	void http_tracker_connection::close()
  	{
  		if (m_tracker_connection)
  		{
  			m_tracker_connection->close();
  			m_tracker_connection.reset();
  		}
  		tracker_connection::close();
  	}
  
  	// endpoints is an in-out parameter
  	void http_tracker_connection::on_filter(http_connection& c
  		, std::vector<tcp::endpoint>& endpoints)
  	{
  		TORRENT_UNUSED(c);
  		if (!tracker_req().filter) return;
  
  		// remove endpoints that are filtered by the IP filter
  		for (std::vector<tcp::endpoint>::iterator i = endpoints.begin();
  			i != endpoints.end();)
  		{
  			if (tracker_req().filter->access(i->address()) == ip_filter::blocked)
  				i = endpoints.erase(i);
  			else
  				++i;
  		}
  
  #ifndef TORRENT_DISABLE_LOGGING
  		boost::shared_ptr<request_callback> cb = requester();
  		if (cb)
  		{
  			cb->debug_log("*** TRACKER_FILTER");
  		}
  #endif
  		if (endpoints.empty())
  			fail(errors::banned_by_ip_filter);
  	}
  
  	void http_tracker_connection::on_connect(http_connection& c)
  	{
  		error_code ec;
  		tcp::endpoint ep = c.socket().remote_endpoint(ec);
  		m_tracker_ip = ep.address();
  		boost::shared_ptr<request_callback> cb = requester();
  	}
  
  	void http_tracker_connection::on_response(error_code const& ec
  		, http_parser const& parser, char const* data, int size)
  	{
  		// keep this alive
  		boost::shared_ptr<http_tracker_connection> me(shared_from_this());
  
  		if (ec && ec != boost::asio::error::eof)
  		{
  			fail(ec);
  			return;
  		}
  
  		if (!parser.header_finished())
  		{
  			fail(boost::asio::error::eof);
  			return;
  		}
  
  		if (parser.status_code() != 200)
  		{
  			fail(error_code(parser.status_code(), http_category())
  				, parser.status_code(), parser.message().c_str());
  			return;
  		}
  
  		if (ec && ec != boost::asio::error::eof)
  		{
  			fail(ec, parser.status_code());
  			return;
  		}
  
  		received_bytes(size + parser.body_start());
  
  		// handle tracker response
  		error_code ecode;
  
  		boost::shared_ptr<request_callback> cb = requester();
  		if (!cb)
  		{
  			close();
  			return;
  		}
  
  		tracker_response resp = parse_tracker_response(data, size, ecode
  			, tracker_req().kind, tracker_req().info_hash);
  
  		if (!resp.warning_message.empty())
  			cb->tracker_warning(tracker_req(), resp.warning_message);
  
  		if (ecode)
  		{
  			fail(ecode, parser.status_code(), resp.failure_reason.c_str()
  				, resp.interval, resp.min_interval);
  			close();
  			return;
  		}
  
  		// do slightly different things for scrape requests
  		if (0 != (tracker_req().kind & tracker_request::scrape_request))
  		{
  			cb->tracker_scrape_response(tracker_req(), resp.complete
  				, resp.incomplete, resp.downloaded, resp.downloaders);
  		}
  		else
  		{
  			std::list<address> ip_list;
  			if (m_tracker_connection)
  			{
  				error_code ignore;
  				std::vector<tcp::endpoint> const& epts = m_tracker_connection->endpoints();
  				for (std::vector<tcp::endpoint>::const_iterator i = epts.begin()
  					, end(epts.end()); i != end; ++i)
  				{
  					ip_list.push_back(i->address());
  				}
  			}
  
  			cb->tracker_response(tracker_req(), m_tracker_ip, ip_list, resp);
  		}
  		close();
  	}
  
  	// TODO: 2 returning a bool here is redundant. Instead this function should
  	// return the peer_entry
  	bool extract_peer_info(bdecode_node const& info, peer_entry& ret, error_code& ec)
  	{
  		// extract peer id (if any)
  		if (info.type() != bdecode_node::dict_t)
  		{
  			ec = errors::invalid_peer_dict;
  			return false;
  		}
  		bdecode_node i = info.dict_find_string("peer id");
  		if (i && i.string_length() == 20)
  		{
  			std::copy(i.string_ptr(), i.string_ptr()+20, ret.pid.begin());
  		}
  		else
  		{
  			// if there's no peer_id, just initialize it to a bunch of zeroes
  			std::fill_n(ret.pid.begin(), 20, 0);
  		}
  
  		// extract ip
  		i = info.dict_find_string("ip");
  		if (i == 0)
  		{
  			ec = errors::invalid_tracker_response;
  			return false;
  		}
  		ret.hostname = i.string_value();
  
  		// extract port
  		i = info.dict_find_int("port");
  		if (i == 0)
  		{
  			ec = errors::invalid_tracker_response;
  			return false;
  		}
  		ret.port = boost::uint16_t(i.int_value());
  
  		return true;
  	}
  
  	tracker_response parse_tracker_response(char const* data, int size, error_code& ec
  		, int const flags, sha1_hash scrape_ih)
  	{
  		tracker_response resp;
  
  		bdecode_node e;
  		int res = bdecode(data, data + size, e, ec);
  
  		if (ec) return resp;
  
  		if (res != 0 || e.type() != bdecode_node::dict_t)
  		{
  			ec = errors::invalid_tracker_response;
  			return resp;
  		}
  
  		int interval = int(e.dict_find_int_value("interval", 0));
  		// if no interval is specified, default to 30 minutes
  		if (interval == 0) interval = 1800;
  		int const min_interval = int(e.dict_find_int_value("min interval", 30));
  
  		resp.interval = interval;
  		resp.min_interval = min_interval;
  
  		bdecode_node tracker_id = e.dict_find_string("tracker id");
  		if (tracker_id)
  			resp.trackerid = tracker_id.string_value();
  
  		// parse the response
  		bdecode_node failure = e.dict_find_string("failure reason");
  		if (failure)
  		{
  			resp.failure_reason = failure.string_value();
  			ec = errors::tracker_failure;
  			return resp;
  		}
  
  		bdecode_node warning = e.dict_find_string("warning message");
  		if (warning)
  			resp.warning_message = warning.string_value();
  
  		if (0 != (flags & tracker_request::scrape_request))
  		{
  			bdecode_node files = e.dict_find_dict("files");
  			if (!files)
  			{
  				ec = errors::invalid_files_entry;
  				return resp;
  			}
  
  			bdecode_node scrape_data = files.dict_find_dict(
  				scrape_ih.to_string());
  
  			if (!scrape_data)
  			{
  				ec = errors::invalid_hash_entry;
  				return resp;
  			}
  
  			resp.complete = int(scrape_data.dict_find_int_value("complete", -1));
  			resp.incomplete = int(scrape_data.dict_find_int_value("incomplete", -1));
  			resp.downloaded = int(scrape_data.dict_find_int_value("downloaded", -1));
  			resp.downloaders = int(scrape_data.dict_find_int_value("downloaders", -1));
  
  			return resp;
  		}
  
  		// look for optional scrape info
  		resp.complete = int(e.dict_find_int_value("complete", -1));
  		resp.incomplete = int(e.dict_find_int_value("incomplete", -1));
  		resp.downloaded = int(e.dict_find_int_value("downloaded", -1));
  
  		bdecode_node peers_ent = e.dict_find("peers");
  		if (peers_ent && peers_ent.type() == bdecode_node::string_t)
  		{
  			char const* peers = peers_ent.string_ptr();
  			int len = peers_ent.string_length();
  #if TORRENT_USE_I2P
  			if (0 != (flags & tracker_request::i2p))
  			{
  				error_code parse_error;
  				for (int i = 0; i < len; i += 32)
  				{
  					if (len - i < 32) break;
  					peer_entry p;
  					p.hostname = base32encode(std::string(peers + i, 32), string::i2p);
  					p.hostname += ".b32.i2p";
  					p.port = 6881;
  					resp.peers.push_back(p);
  				}
  			}
  			else
  #endif
  			{
  				resp.peers4.reserve(len / 6);
  				for (int i = 0; i < len; i += 6)
  				{
  					if (len - i < 6) break;
  
  					ipv4_peer_entry p;
  					p.ip = detail::read_v4_address(peers).to_v4().to_bytes();
  					p.port = detail::read_uint16(peers);
  					resp.peers4.push_back(p);
  				}
  			}
  		}
  		else if (peers_ent && peers_ent.type() == bdecode_node::list_t)
  		{
  			int len = peers_ent.list_size();
  			resp.peers.reserve(len);
  			error_code parse_error;
  			for (int i = 0; i < len; ++i)
  			{
  				peer_entry p;
  				if (!extract_peer_info(peers_ent.list_at(i), p, parse_error))
  					continue;
  				resp.peers.push_back(p);
  			}
  
  			// only report an error if all peer entries are invalid
  			if (resp.peers.empty() && parse_error)
  			{
  				ec = parse_error;
  				return resp;
  			}
  		}
  		else
  		{
  			peers_ent.clear();
  		}
  
  #if TORRENT_USE_IPV6
  		bdecode_node ipv6_peers = e.dict_find_string("peers6");
  		if (ipv6_peers)
  		{
  			char const* peers = ipv6_peers.string_ptr();
  			int len = ipv6_peers.string_length();
  			resp.peers6.reserve(len / 18);
  			for (int i = 0; i < len; i += 18)
  			{
  				if (len - i < 18) break;
  
  				ipv6_peer_entry p;
  				p.ip = detail::read_v6_address(peers).to_v6().to_bytes();
  				p.port = detail::read_uint16(peers);
  				resp.peers6.push_back(p);
  			}
  		}
  		else
  		{
  			ipv6_peers.clear();
  		}
  #else
  		bdecode_node ipv6_peers;
  #endif
  /*
  		// if we didn't receive any peers. We don't care if we're stopping anyway
  		if (peers_ent == 0 && ipv6_peers == 0
  			&& tracker_req().event != tracker_request::stopped)
  		{
  			ec = errors::invalid_peers_entry;
  			return resp;
  		}
  */
  		bdecode_node ip_ent = e.dict_find_string("external ip");
  		if (ip_ent)
  		{
  			char const* p = ip_ent.string_ptr();
  			if (ip_ent.string_length() == int(address_v4::bytes_type().size()))
  				resp.external_ip = detail::read_v4_address(p);
  #if TORRENT_USE_IPV6
  			else if (ip_ent.string_length() == int(address_v6::bytes_type().size()))
  				resp.external_ip = detail::read_v6_address(p);
  #endif
  		}
  
  		return resp;
  	}
  }
  
  