Improved packet obfuscation reliability

- Fixes bugreport:7607
  http://hercules.ws/board/tracker/issue-7607-changing-emblem-with-packet-obfuscation-2-unknown-packet/
- Resolved unintended disconnections caused by invalid packets when
  obfuscation is enabled and a fragmented packet is received.
- Improved packet parsing reliability when packet obfuscation is set to
  optional.
Special thanks to serverkid for reporting the issue and Ind for figuring
out the cause and suggesting a solution.

Signed-off-by: Haru <haru@dotalux.com>

3 files changed, 41 insertions, 23 deletions

diff --git a/src/map/clif.c b/src/map/clif.c
index 5110ca76b..2f63ec5c0 100644
--- a/src/map/clif.c
+++ b/src/map/clif.c
@@ -9209,8 +9209,11 @@ void clif_parse_WantToConnection(int fd, struct map_session_data* sd) {
 
 	CREATE(sd, TBL_PC, 1);
 	sd->fd = fd;
-	sd->cryptKey = (( clif->cryptKey[0] * clif->cryptKey[1] ) + clif->cryptKey[2]) & 0xFFFFFFFF;
-	
+
+	sd->cryptKey = (( ((( clif->cryptKey[0] * clif->cryptKey[1] ) + clif->cryptKey[2]) & 0xFFFFFFFF)
+						* clif->cryptKey[1] ) + clif->cryptKey[2]) & 0xFFFFFFFF;
+	sd->parse_cmd_func = clif->parse_cmd;
+
 	session[fd]->session_data = sd;
 
 	pc->setnewpc(sd, account_id, char_id, login_id1, client_tick, sex, fd);
@@ -17481,42 +17484,41 @@ void clif_cart_additem_ack(struct map_session_data *sd, int flag) {
 /* */
 unsigned short clif_decrypt_cmd( int cmd, struct map_session_data *sd ) {
 	if( sd ) {
-		sd->cryptKey = (( sd->cryptKey * clif->cryptKey[1] ) + clif->cryptKey[2]) & 0xFFFFFFFF;
 		return (cmd ^ ((sd->cryptKey >> 16) & 0x7FFF));
 	}
 	return (cmd ^ (((( clif->cryptKey[0] * clif->cryptKey[1] ) + clif->cryptKey[2]) >> 16) & 0x7FFF));
 }
-unsigned short clif_parse_cmd_normal ( int fd, struct map_session_data *sd ) {
+unsigned short clif_parse_cmd_normal( int fd, struct map_session_data *sd ) {
 	unsigned short cmd = RFIFOW(fd,0);
+
 	// filter out invalid / unsupported packets
-	if (cmd > MAX_PACKET_DB || packet_db[cmd].len == 0)
+	if( cmd > MAX_PACKET_DB || cmd < MIN_PACKET_DB || packet_db[cmd].len == 0 )
 		return 0;
 
 	return cmd;
 }
-unsigned short clif_parse_cmd_optional ( int fd, struct map_session_data *sd ) {
+unsigned short clif_parse_cmd_decrypt( int fd, struct map_session_data *sd ) {
 	unsigned short cmd = RFIFOW(fd,0);
 
+	cmd = clif->decrypt_cmd(cmd, sd);
+
 	// filter out invalid / unsupported packets
-	if (cmd > MAX_PACKET_DB || packet_db[cmd].len == 0) {
-		cmd = clif->decrypt_cmd( cmd, sd );
-		if( cmd > MAX_PACKET_DB || packet_db[cmd].len == 0 )
-			return 0;
-		RFIFOW(fd, 0) = cmd;
-	}
+	if( cmd > MAX_PACKET_DB || cmd < MIN_PACKET_DB || packet_db[cmd].len == 0 )
+		return 0;
 
 	return cmd;
 }
-unsigned short clif_parse_cmd_decrypt ( int fd, struct map_session_data *sd ) {
+unsigned short clif_parse_cmd_optional( int fd, struct map_session_data *sd ) {
 	unsigned short cmd = RFIFOW(fd,0);
 
-	cmd = clif->decrypt_cmd( cmd, sd );
-	
 	// filter out invalid / unsupported packets
-	if (cmd > MAX_PACKET_DB || packet_db[cmd].len == 0 )
-		return 0;
-	
-	RFIFOW(fd, 0) = cmd;
+	if( cmd > MAX_PACKET_DB || cmd < MIN_PACKET_DB || packet_db[cmd].len == 0 ) {
+		if( sd )
+			sd->parse_cmd_func = clif_parse_cmd_decrypt;
+		return clif_parse_cmd_decrypt(fd, sd);
+	} else if( sd ) {
+		sd->parse_cmd_func = clif_parse_cmd_normal;
+	}
 
 	return cmd;
 }
@@ -17536,6 +17538,8 @@ int clif_parse(int fd) {
 		// begin main client packet processing loop
 		
 		sd = (TBL_PC *)session[fd]->session_data;
+		unsigned short (*parse_cmd_func)(int fd, struct map_session_data *sd);
+
 		if (session[fd]->flag.eof) {
 			if (sd) {
 				if (sd->state.autotrade) {
@@ -17563,8 +17567,13 @@ int clif_parse(int fd) {
 		if (RFIFOREST(fd) < 2)
 			return 0;
 		
-		if( !( cmd = clif->parse_cmd(fd,sd) ) ) {
-			ShowWarning("clif_parse: Received unsupported packet (packet 0x%04x, %d bytes received), disconnecting session #%d.\n", RFIFOW(fd,0), RFIFOREST(fd), fd);
+		if( sd )
+			parse_cmd_func = sd->parse_cmd_func;
+		else
+			parse_cmd_func = clif->parse_cmd;
+
+		if( !( cmd = parse_cmd_func(fd,sd) ) ) {
+			ShowWarning("clif_parse: Received unsupported packet (packet 0x%04x (0x%04x), %d bytes received), disconnecting session #%d.\n", cmd, RFIFOW(fd,0), RFIFOREST(fd), fd);
 #ifdef DUMP_INVALID_PACKET
 			ShowDump(RFIFOP(fd,0), RFIFOREST(fd));
 #endif
@@ -17593,6 +17602,13 @@ int clif_parse(int fd) {
 		if ((int)RFIFOREST(fd) < packet_len)
 			return 0; // not enough data received to form the packet
 
+		if( cmd != RFIFOW(fd, 0) ) {
+			RFIFOW(fd, 0) = cmd;
+			if( sd ) {
+				sd->cryptKey = (( sd->cryptKey * clif->cryptKey[1] ) + clif->cryptKey[2]) & 0xFFFFFFFF; // Update key for the next packet
+			}
+		}
+
 		if( packet_db[cmd].func == clif->pDebug )
 			packet_db[cmd].func(fd, sd);
 		else if( packet_db[cmd].func != NULL ) {
diff --git a/src/map/clif.h b/src/map/clif.h
index 9bb5f25e7..43b2fa1a6 100644
--- a/src/map/clif.h
+++ b/src/map/clif.h
@@ -52,7 +52,8 @@ struct skill_cd;
  * Enumerations
  **/
 enum {// packet DB
-	MAX_PACKET_DB  = 0xF00,
+	MIN_PACKET_DB  = 0x0064,
+	MAX_PACKET_DB  = 0x0F00,
 	MAX_PACKET_POS = 20,
 };
 
diff --git a/src/map/pc.h b/src/map/pc.h
index 42bfb56c1..1f1538e1f 100644
--- a/src/map/pc.h
+++ b/src/map/pc.h
@@ -502,7 +502,8 @@ struct map_session_data {
 	unsigned int queues_count;
 	
 	/* Made Possible Thanks to Yommy~! */
-	unsigned int cryptKey;
+	unsigned int cryptKey;                                                 ///< Packet obfuscation key to be used for the next received packet
+	unsigned short (*parse_cmd_func)(int fd, struct map_session_data *sd); ///< parse_cmd_func used by this player
 	
 	unsigned char delayed_damage;//ref. counter bugreport:7307 [Ind/Hercules]