Add option to not send pre v25 init packet

The legacy init packet (pre v25) sends information about the client's
password that a server could use to log in to other servers if the
username and password are the same. All the other benefits of SRP of
protocol v25 are missed if the legacy init packet is still sent during
connection creation.

This patch adds an option to not send the v25 init packet. Not sending
the v25 packet means breaking compat with pre v25 servers, but as the
option is not enabled by default, no servers are affected unless the
user explicitly flips the switch. More than 90% of the servers on the
serverlist support post v25 protocols.

The patch also fixes a bug with greying out of non compliant servers
being done wrongly, the min and max params were mixed.

6 files changed, 49 insertions, 24 deletions

diff --git a/src/client.cpp b/src/client.cpp
index 41468f0fd..2a8e02d6e 100644
--- a/src/client.cpp
+++ b/src/client.cpp
@@ -386,25 +386,30 @@ void Client::step(float dtime)
 			Player *myplayer = m_env.getLocalPlayer();
 			FATAL_ERROR_IF(myplayer == NULL, "Local player not found in environment.");
 
-			// Send TOSERVER_INIT_LEGACY
-			// [0] u16 TOSERVER_INIT_LEGACY
-			// [2] u8 SER_FMT_VER_HIGHEST_READ
-			// [3] u8[20] player_name
-			// [23] u8[28] password (new in some version)
-			// [51] u16 minimum supported network protocol version (added sometime)
-			// [53] u16 maximum supported network protocol version (added later than the previous one)
-
-			char pName[PLAYERNAME_SIZE];
-			char pPassword[PASSWORD_SIZE];
-			memset(pName, 0, PLAYERNAME_SIZE * sizeof(char));
-			memset(pPassword, 0, PASSWORD_SIZE * sizeof(char));
-
-			std::string hashed_password = translate_password(myplayer->getName(), m_password);
-			snprintf(pName, PLAYERNAME_SIZE, "%s", myplayer->getName());
-			snprintf(pPassword, PASSWORD_SIZE, "%s", hashed_password.c_str());
-
-			sendLegacyInit(pName, pPassword);
-			if (LATEST_PROTOCOL_VERSION >= 25)
+			u16 proto_version_min = g_settings->getFlag("send_pre_v25_init") ?
+				CLIENT_PROTOCOL_VERSION_MIN_LEGACY : CLIENT_PROTOCOL_VERSION_MIN;
+
+			if (proto_version_min < 25) {
+				// Send TOSERVER_INIT_LEGACY
+				// [0] u16 TOSERVER_INIT_LEGACY
+				// [2] u8 SER_FMT_VER_HIGHEST_READ
+				// [3] u8[20] player_name
+				// [23] u8[28] password (new in some version)
+				// [51] u16 minimum supported network protocol version (added sometime)
+				// [53] u16 maximum supported network protocol version (added later than the previous one)
+
+				char pName[PLAYERNAME_SIZE];
+				char pPassword[PASSWORD_SIZE];
+				memset(pName, 0, PLAYERNAME_SIZE * sizeof(char));
+				memset(pPassword, 0, PASSWORD_SIZE * sizeof(char));
+
+				std::string hashed_password = translate_password(myplayer->getName(), m_password);
+				snprintf(pName, PLAYERNAME_SIZE, "%s", myplayer->getName());
+				snprintf(pPassword, PASSWORD_SIZE, "%s", hashed_password.c_str());
+
+				sendLegacyInit(pName, pPassword);
+			}
+			if (CLIENT_PROTOCOL_VERSION_MAX >= 25)
 				sendInit(myplayer->getName());
 		}
 
@@ -1003,10 +1008,13 @@ void Client::sendLegacyInit(const char* playerName, const char* playerPassword)
 	NetworkPacket pkt(TOSERVER_INIT_LEGACY,
 			1 + PLAYERNAME_SIZE + PASSWORD_SIZE + 2 + 2);
 
+	u16 proto_version_min = g_settings->getFlag("send_pre_v25_init") ?
+		CLIENT_PROTOCOL_VERSION_MIN_LEGACY : CLIENT_PROTOCOL_VERSION_MIN;
+
 	pkt << (u8) SER_FMT_VER_HIGHEST_READ;
 	pkt.putRawString(playerName,PLAYERNAME_SIZE);
 	pkt.putRawString(playerPassword, PASSWORD_SIZE);
-	pkt << (u16) CLIENT_PROTOCOL_VERSION_MIN << (u16) CLIENT_PROTOCOL_VERSION_MAX;
+	pkt << (u16) proto_version_min << (u16) CLIENT_PROTOCOL_VERSION_MAX;
 
 	Send(&pkt);
 }
@@ -1017,8 +1025,12 @@ void Client::sendInit(const std::string &playerName)
 
 	// we don't support network compression yet
 	u16 supp_comp_modes = NETPROTO_COMPRESSION_NONE;
+
+	u16 proto_version_min = g_settings->getFlag("send_pre_v25_init") ?
+		CLIENT_PROTOCOL_VERSION_MIN_LEGACY : CLIENT_PROTOCOL_VERSION_MIN;
+
 	pkt << (u8) SER_FMT_VER_HIGHEST_READ << (u16) supp_comp_modes;
-	pkt << (u16) CLIENT_PROTOCOL_VERSION_MIN << (u16) CLIENT_PROTOCOL_VERSION_MAX;
+	pkt << (u16) proto_version_min << (u16) CLIENT_PROTOCOL_VERSION_MAX;
 	pkt << playerName;
 
 	Send(&pkt);
diff --git a/src/defaultsettings.cpp b/src/defaultsettings.cpp
index 53059e8ad..84098e3d5 100644
--- a/src/defaultsettings.cpp
+++ b/src/defaultsettings.cpp
@@ -184,6 +184,8 @@ void set_default_settings(Settings *settings)
 	settings->setDefault("minimap_shape_round", "true");
 	settings->setDefault("minimap_double_scan_height", "true");
 
+	settings->setDefault("send_pre_v25_init", "true");
+
 	settings->setDefault("curl_timeout", "5000");
 	settings->setDefault("curl_parallel_limit", "8");
 	settings->setDefault("curl_file_download_timeout", "300000");
diff --git a/src/network/networkprotocol.h b/src/network/networkprotocol.h
index 7cde6d764..177b97680 100644
--- a/src/network/networkprotocol.h
+++ b/src/network/networkprotocol.h
@@ -145,7 +145,10 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #define SERVER_PROTOCOL_VERSION_MAX LATEST_PROTOCOL_VERSION
 
 // Client's supported network protocol range
-#define CLIENT_PROTOCOL_VERSION_MIN 13
+// The minimal version depends on whether
+// send_pre_v25_init is enabled or not
+#define CLIENT_PROTOCOL_VERSION_MIN 25
+#define CLIENT_PROTOCOL_VERSION_MIN_LEGACY 13
 #define CLIENT_PROTOCOL_VERSION_MAX LATEST_PROTOCOL_VERSION
 
 // Constant that differentiates the protocol from random data and other protocols
diff --git a/src/script/lua_api/l_mainmenu.cpp b/src/script/lua_api/l_mainmenu.cpp
index c924a5d9c..7b29db159 100644
--- a/src/script/lua_api/l_mainmenu.cpp
+++ b/src/script/lua_api/l_mainmenu.cpp
@@ -1095,7 +1095,9 @@ int ModApiMainMenu::l_get_screen_info(lua_State *L)
 /******************************************************************************/
 int ModApiMainMenu::l_get_min_supp_proto(lua_State *L)
 {
-	lua_pushinteger(L, CLIENT_PROTOCOL_VERSION_MIN);
+	u16 proto_version_min = g_settings->getFlag("send_pre_v25_init") ?
+		CLIENT_PROTOCOL_VERSION_MIN_LEGACY : CLIENT_PROTOCOL_VERSION_MIN;
+	lua_pushinteger(L, proto_version_min);
 	return 1;
 }
 
diff --git a/src/serverlist.cpp b/src/serverlist.cpp
index 6e79b55a4..de7962a68 100644
--- a/src/serverlist.cpp
+++ b/src/serverlist.cpp
@@ -69,8 +69,12 @@ std::vector<ServerListSpec> getLocal()
 std::vector<ServerListSpec> getOnline()
 {
 	std::ostringstream geturl;
+
+	u16 proto_version_min = g_settings->getFlag("send_pre_v25_init") ?
+		CLIENT_PROTOCOL_VERSION_MIN_LEGACY : CLIENT_PROTOCOL_VERSION_MIN;
+
 	geturl << g_settings->get("serverlist_url") <<
-		"/list?proto_version_min=" << CLIENT_PROTOCOL_VERSION_MIN <<
+		"/list?proto_version_min=" << proto_version_min <<
 		"&proto_version_max=" << CLIENT_PROTOCOL_VERSION_MAX;
 	Json::Value root = fetchJsonValue(geturl.str(), NULL);
 
diff --git a/src/settings_translation_file.cpp b/src/settings_translation_file.cpp
index f115bc011..0e0c3acc0 100644
--- a/src/settings_translation_file.cpp
+++ b/src/settings_translation_file.cpp
@@ -98,6 +98,8 @@ fake_function() {
 	gettext("Address to connect to.\nLeave this blank to start a local server.\nNote that the address field in the main menu overrides this setting.");
 	gettext("Remote port");
 	gettext("Port to connect to (UDP).\nNote that the port field in the main menu overrides this setting.");
+	gettext("Support older servers");
+	gettext("Whether to support older servers before protocol version 25.\nEnable if you want to connect to 0.4.12 servers and before.\nServers starting with 0.4.13 will work, 0.4.12-dev servers may work.\nDisabling this option will protect your password better.");
 	gettext("Saving map received from server");
 	gettext("Save the map received by the client on disk.");
 	gettext("Connect to external media server");