optimized encryption

include/libtorrent/pe_crypto.hpp

@@ -58,7 +58,9 @@ namespace libtorrent
 		// m_dh_secret.
 		int compute_secret(const char* remote_pubkey);
 
-		const char* get_secret() const;
+		char const* get_secret() const { return m_dh_secret; }
+
+		sha1_hash const& get_hash_xor_mask() const { return m_xor_mask; }
 		
 	private:
 		int get_local_key_size() const
@@ -71,6 +73,7 @@ namespace libtorrent
 
 		char m_dh_local_key[96];
 		char m_dh_secret[96];
+		sha1_hash m_xor_mask;
 	};
 	
 	class RC4_handler // Non copyable

include/libtorrent/torrent.hpp

@@ -132,6 +132,14 @@ namespace libtorrent
 
 		void parse_resume_data(std::vector<char>* resume_data);
 
+#ifndef TORRENT_DISABLE_ENCRYPTION
+		sha1_hash const& obfuscated_hash() const
+		{ return m_obfuscated_hash; }
+#endif
+
+		sha1_hash const& info_hash() const
+		{ return m_torrent_file->info_hash(); }
+
 		// starts the announce timer
 		void start();
 
@@ -821,6 +829,11 @@ namespace libtorrent
 		// longer be used and will be reset
 		boost::scoped_ptr<std::string> m_name;
 
+#ifndef TORRENT_DISABLE_ENCRYPTION
+		// this is SHA1("req2" + info-hash), used for
+		// encrypted hand shakes
+		sha1_hash m_obfuscated_hash;
+#endif
 		session_settings const& m_settings;
 
 		storage_constructor_type m_storage_constructor;

src/bt_peer_connection.cpp

@@ -1841,7 +1841,8 @@ namespace libtorrent
 					return;
 				}
 
-				cut_receive_buffer(bytes_processed, (std::min)(packet_size(), (512+20) - m_sync_bytes_read));
+				cut_receive_buffer(bytes_processed, (std::min)(packet_size()
+					, (512+20) - m_sync_bytes_read));
 
 				TORRENT_ASSERT(!packet_finished());
 				return;
@@ -1872,51 +1873,32 @@ namespace libtorrent
 
 			recv_buffer = receive_buffer();
 
-			// only calls info_hash() on the torrent_handle's, which
-			// never throws.
-			session_impl::mutex_t::scoped_lock l(m_ses.m_mutex);
+			aux::session_impl::torrent_map::const_iterator i;
 
-			std::vector<torrent_handle> active_torrents = m_ses.get_torrents();
-			std::vector<torrent_handle>::const_iterator i;
-			hasher h;
-			sha1_hash skey_hash, obfs_hash;
-
-			for (i = active_torrents.begin(); i != active_torrents.end(); ++i)
+			for (i = m_ses.m_torrents.begin(); i != m_ses.m_torrents.end(); ++i)
 			{
-				torrent_handle const& t_h = *i; // TODO possible errors
-				sha1_hash const& info_hash = t_h.info_hash();
-				// TODO Does info_hash need to be checked for validity?
-				
-				h.reset();
-				h.update("req2", 4);
-				h.update((char*)info_hash.begin(), 20);
-
-			    skey_hash = h.final();
-				
-				h.reset();
-				h.update("req3", 4);
-				h.update(m_dh_key_exchange->get_secret(), dh_key_len);
-
-				obfs_hash = h.final();
+				torrent const& ti = *i->second;
+				sha1_hash const& skey_hash = ti.obfuscated_hash();
+				sha1_hash obfs_hash = m_dh_key_exchange->get_hash_xor_mask();
 				obfs_hash ^= skey_hash;
 
 				if (std::equal(recv_buffer.begin, recv_buffer.begin + 20,
-					(char*)obfs_hash.begin()))
+					(char*)&obfs_hash[0]))
 				{
 					if (!t)
 					{
-						attach_to_torrent(info_hash);
+						attach_to_torrent(ti.info_hash());
 						if (is_disconnecting()) return;
 
 						t = associated_torrent().lock();
 						TORRENT_ASSERT(t);
 					}
 
-					init_pe_RC4_handler(m_dh_key_exchange->get_secret(), info_hash);
+					init_pe_RC4_handler(m_dh_key_exchange->get_secret(), ti.info_hash());
 #ifdef TORRENT_VERBOSE_LOGGING
 					(*m_logger) << " stream key found, torrent located.\n";
 #endif
-					continue; // TODO Check flow control with multiple torrents
+					break;
 				}
 			}
 

src/pe_crypto.cpp

@@ -38,6 +38,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include <openssl/engine.h>
 
 #include "libtorrent/pe_crypto.hpp"
+#include "libtorrent/hasher.hpp"
 #include "libtorrent/assert.hpp"
 
 namespace libtorrent
@@ -144,12 +145,14 @@ namespace libtorrent
 		}
 		std::copy(dh_secret, dh_secret + secret_size, m_dh_secret + 96 - secret_size);
 		BN_free(bn_remote_pubkey);
-		return 0;
-	}
 
-	char const* dh_key_exchange::get_secret() const
-	{
-		return m_dh_secret;
+		// calculate the xor mask for the obfuscated hash
+		hasher h;
+		h.update("req3", 4);
+		h.update(m_dh_secret, 96);
+		m_xor_mask = h.final();
+
+		return 0;
 	}
 
 } // namespace libtorrent

src/torrent.cpp

@@ -206,6 +206,13 @@ namespace libtorrent
 		, m_complete_sent(false)
 	{
 		parse_resume_data(resume_data);
+
+#ifndef TORRENT_DISABLE_ENCRYPTION
+		hasher h;
+		h.update("req2", 4);
+		h.update((char*)&tf->info_hash()[0], 20);
+		m_obfuscated_hash = h.final();
+#endif
 	}
 
 	torrent::torrent(
@@ -280,6 +287,14 @@ namespace libtorrent
 		, m_complete_sent(false)
 	{
 		parse_resume_data(resume_data);
+
+#ifndef TORRENT_DISABLE_ENCRYPTION
+		hasher h;
+		h.update("req2", 4);
+		h.update((char*)&info_hash[0], 20);
+		m_obfuscated_hash = h.final();
+#endif
+
 #ifndef NDEBUG
 		m_files_checked = false;
 #endif