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Sherer last won the day on October 25

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  1. Sherer


    Nah man idk what did I write boost. I meant cryptopp.
  2. Sherer

    c++ Clear Banned Player Data

    Small hint. Don't put any table/container loose like that. Keep it either in anonymous namespace or add static keyword in order to make it internal linked (just in a matter of good code style). Additionally bear to check for nullpointers/array elements once they can cause a lot of unexpected stuff in your code. I like the idea but I think this implementation might not be the point. The player data can still be DB's cache thus once flush session kicks in the data may be resaved. Same applies to billing. You might like to handle this as well.
  3. Sherer


    Or use older version of boost Meant cryptopp
  4. Sherer

    Game/Auth handshake vulnerability

    Updated github repo with code line that's gonna solve this issue.
  5. Sherer

    Game/Auth handshake vulnerability

    Looks really interesting. How did it work for you? Once you added the ip into mitigation one wasn't able to connect to the server no more? Did the user get dropped immediately?
  6. Sherer

    Game/Auth handshake vulnerability

    Thanks for the hint. Due to your feedback I refactored handshake authentication to be done through P2P rather than by CORE->DB->CORE. If someone follows this tutorial you need to reimplement that part (with github stuff). According to your third question I don't really think it matters since some of methods don't even bother sending any packets at all. They just spoof the queue with fake connection and stuck in handshake stage. Nice idea with OVH_API - haven't really heard about that (you can make some tutorial if you find it helpful for us). In reference to the code you attached all methods bother sending packets at all.
  7. Sherer

    Game/Auth handshake vulnerability

    Added new link
  8. Sherer

    c++ Reimplementation of Events

    Reupload (cannot edit thread):
  9. Hello, Didn't know whether to place this subject either here or on guides but since I'm gonna not only share the mitigation but also express my conclusion about this issue and further after-effects. Only part of codes are attached below. For methods definitions + headers jump here: 1. Vulnerability overview. Any kind of tcp application is required to have a server (anda client). Once a server is launched it's binded to appropriate socket and set on listening for further connections (in a cutoff, navigate here for more precise info) On the other side client is the one which is suppose to connect to server. It does it by connecting to server's socket and start to process a handshake. This is how it works in a big shortcut - or I should rather say, it does work if we deal with normal peer. In case of more-like modern apps the traffic is held by efficient algorithms that can carry even heavy traffic or eventual feeble attack. But since Metin2's core is not a state-of-art app and simply runs on old C style code (libthecore) without a real concurrency support that might dive us into some tricky issues. So let's imagine what happens if someone tries to pull off an attack and flood the server with enormous amount of packets. Since each of connection needs to be validated first, it goes through the handshake. Server catches it through the fdwatch function (jump to io_loop, main.cpp), then if no desc is presented moves it to AcceptDesc where the connection is validated. It is usually allowed unless the peer's ip is not in a banlist. Then desc is created and connection is saved for further handshake response. Sounds reasonable, right? Now imagine when thousands connection are accepted, validated, and expected to send handshake response. Does it still sound so optimistic? Additionally, when a desc is created it does allocated buffer for I/O traffic. Each connection. Each time. Each desc. Now do the math and try to conceive how much of memory is simply wasted. So that's the point we've been heading. That's our vulnerability. And btw, if so many agents are in the queue, do you think anybody will be able to connect your server? 2. Four major problems. Let's start from handshake itself. Imagine that someone approaches you and gives you his hand to shake it. And than second. And then third. Doesn't make sense, does it? Same applies to handshake process. Simply, only one handshake shall be ongoing for the host unless it completes it. So, let's jump to AcceptDesc in desc_manager.cpp and add this little code above: newd = M2_NEW DESC; // Let's check if a handshake from this host is already ongoing if (GetHostHandshake(peer)) { sys_log(0, "Handshake from %s is not permitted!", host); socket_close(desc); return NULL; } So let's consider this as solved for now. Then the second issue. Let's imagine yet another event. Someone shakes your hand but this time completes the handshake. But he does it again. And again. And again. Sounds exhausting? Let's add this 2 conditions below our recent code from above: static const int HOST_CONNECTION_LIMIT = 3; // In case if host completed handshake process let's check if it doesn't reach the limit if (GetHostConnectionCount(peer) >= HOST_CONNECTION_LIMIT) { sys_log(0, "Host %s connection limit has been reached!", host); socket_close(desc); return NULL; } // And block intrusive connections as well if (IsIntrusiveConnection(host)) { sys_log(0, "Host %s is intrusive!", host); socket_close(desc); return NULL; } First if checks if host doesn't reach the handshake limit and if it does - the host is dropped. Second if seeks for intrusive peers. That simply means if one tries to connect again, and again, and again in defined time lapse it probably turns out to be an attacking IP. Let's jump for a moment to desc.cpp, Initialize and add this variable initialization there: tt_creation_time = get_global_time(); Yet another problem solved. Still tho, all this code is considered to work more for authentication than for game's core. Why is so? Imagine a person how is not suppose to have any attention at all - a movie star for example. Usually when one walks on red carpet there are bunch of body guards sealing him/her out from the crowd around. Same should happen to game cores because why one would try to perform a handshake with game if hadn't even logged in? So that's we are going to do, simply whitelist players who were succeeded to perform through the login process and obtained login key. Firstly let's jump back to the desc_manager.cpp and add this little code above our previous alterations: // If it's not an auth server - check for validation first if (!g_bAuthServer) { if (!IsOnHandshakeWhitelist(peer)) { // sys_log(0, "Host %s has not validated through login!", host); socket_close(desc); return NULL; } } Now open input_db.cpp, move to AuthLogin function and add at the end: // Validating handshake TPacketGGHandshakeValidate pack; pack.header = HEADER_GG_HANDSHAKE_VALIDATION; strlcpy(pack.sUserIP, d->GetHostName(), sizeof(pack.sUserIP)); P2P_MANAGER::instance().Send(&pack, sizeof(pack)); And so on repeat it for AuthLoginOpenID if you use it. Now let's jump to input_p2p.cpp, move to Analyze function and after the initial syslog: // Auth server is not allowed for p2p if (g_bAuthServer) { // Clearing buffers for dynamic packets switch (bHeader) { case HEADER_GG_RELAY: { TPacketGGRelay * p = (TPacketGGRelay *) c_pData; if (m_iBufferLeft < sizeof(TPacketGGRelay) + p->lSize) iExtraLen = -1; else iExtraLen = p->lSize; } break; case HEADER_GG_NOTICE: { TPacketGGNotice * p = (TPacketGGNotice *) c_pData; if (m_iBufferLeft < sizeof(TPacketGGNotice) + p->lSize) iExtraLen = -1; else iExtraLen = p->lSize; } break; case HEADER_GG_GUILD: { iExtraLen = m_iBufferLeft - sizeof(TPacketGGGuild); } break; case HEADER_GG_MONARCH_NOTICE: { TPacketGGMonarchNotice * p = (TPacketGGMonarchNotice *) c_pData; if (m_iBufferLeft < p->lSize + sizeof(TPacketGGMonarchNotice)) iExtraLen = -1; else iExtraLen = p->lSize; } break; } return iExtraLen; } Since some of the packets might be dynamic, we need to ensure that data they hold is cleared properly. If you have more dynamic packets binded - add them as above. Move to db.cpp, find function SendLoginPing and replace with following: void DBManager::SendLoginPing(const char * c_pszLogin) { /* TPacketGGLoginPing ptog; ptog.bHeader = HEADER_GG_LOGIN_PING; strlcpy(ptog.szLogin, c_pszLogin, sizeof(ptog.szLogin)); if (!g_pkAuthMasterDesc) // If I am master, broadcast to others { P2P_MANAGER::instance().Send(&ptog, sizeof(TPacketGGLoginPing)); } else // If I am slave send login ping to master { g_pkAuthMasterDesc->Packet(&ptog, sizeof(TPacketGGLoginPing)); } */ } Avoiding clearing billing like that (wtf is that btw, shouldn't be executed at all). Now move to packet_info.cpp and add this code in constructor: Set(HEADER_GG_HANDSHAKE_VALIDATION, sizeof(TPacketGGHandshakeValidate), "HandShakeValidation", false); Jump back to input_p2p.cpp and add this case in Analyze function: case HEADER_GG_HANDSHAKE_VALIDATION: DESC_MANAGER::instance().AddToHandshakeWhiteList((const TPacketGGHandshakeValidate *) c_pData); break; Finally jump to ClientManager.cpp in DB. Find function QUERY_SETUP and if condition with bAuthServer and add there following code: peer->SetChannel(1); Sine P2P communication is allowed only for peers possessing any channel number greater than zero, we set it. Usually this practice should be forbidden but since we restrain the traffic for auth server (with code above) it should be safe. Beware that this might cause first login failed because of packet propagation that can reach the cores after player connects. Voilà, were mostly done with coding! Last but no least, we need to take a brief introduction into kqueue and tedious tour between sockets and kernel vars. Starting with kqueue. I would try to explain this but you better jump to this link. Freebsd documentation always appreciated. Since Metin2 implementation of kqueue wrapper has its size limit you may try to increase it a bit and seek for a feedback. If'd like to do so jump to main.cpp, start function and edit this variable: main_fdw = fdwatch_new(VALUE); Yet keep in mind! Do not try to over-optimize it! Try to experiment, put the different values. If you somehow screw it up it might drag you into the checkpoint issues and eventually crash the whole app. So now a few words about sockets and how the listening process works. When each connection aiming to appropriate port is detected it is dropped into the queue where it's waiting for application to pick it up. So simply we can consider this as a waiting queue like in a grocery store. The point is that this queue has it's limit and once the limit is reached, any new connection is declined at sight. The listening limit for Metin2 core is wrapped into variable called SOMAXCONN. If you dive into C socket documentation you can find something like this: /* *Maximum queue length specifiable by listen /* #define SOMAXCONN 10 As for me it was 128. Since it's a define the value is simply embedded into the app and you cannot manipulate it once a binary is built. So let's change it to let more connection be scheduled. You may ask, why? If player tries to log in it does connect the channel port. If the channel is unavailable you see fadeout and connection is terminated. It happens because there is no place in the queue thus connection is scheduled at all. But be careful! Do not set this value into some high-peak numbers! Be aware that our io_loop function need to iterate through these all events and manage to handle this during the heartbeat session. If you try to over optimize this value you can end up causing lags on the server, internal packets delays and more. In case you'd ask me, value around 1024 is acceptable but still it's better if you take some lecture and experiment a bit. And one more thing, don't forget to set this kernel option on the machine where your server runs: sysctl kern.ipc.soacceptqueue=1024 sysctl kern.ipc.somaxconn=1024 So we are done! Don't forget to add the code from my github repo! Epilogue Metin2's quite an old app and we should not forget about that. The netcode is old, rubbish and cumbersome thus this issue might be only one of many we haven't found just yet. Keep in mind tho that even that mitigation won't protect your server. Actually I doubt that even rewriting the code into more modern shape would do that if you don't get yourselves a good protection. Protection, filters, external firewalls are actually the key especially now when stressers and all this stuff are back and harmful again. Hope that this little thread will help you in your future development. Extra I manage to write a little collector for getting rid of handshakes that never completed this process (outdated). If you'd like to switch it on jump to desc_manager.cpp constructor and add there: CEventFunctionHandler::instance().AddEvent([this](SArgumentSupportImpl *) { desc_manager_garbage_collector_info* info = AllocEventInfo<desc_manager_garbage_collector_info>(); m_pkDescManagerGarbageCollector = event_create(desc_manager_garbage_collector_event, info, PASSES_PER_SEC(1)); }, "DESC_MANAGER_COLLECTOR", 1); Beware that you need this feature: And don't forget to add this to destructor: event_cancel(&m_pkDescManagerGarbageCollector); Regards Btw, credits for @Flourine for flooding my dev server with 20k packets per sec (asked for 2 btw). That helped me to analyze the problem.
  10. Sherer

    ah shit here we go again

    Mum look I'm a hacker. Mum look I got my first stresser for 10$. Mum I'm taking down this server. Mum.. Why are you packing my things? Mum look at me! I want your attention. More serious. I don't think that removing that crappy stuff would seal the deal. It's most of the sync packets being sent to server to overflow it. It shouldn't be allowed by firewall to pull off this kind of traffic (most of these IPs are from China, Russia, India). Simple ddos, get some protection bois. Small hint: sysctl net.inet.tcp.syncache.rexmtlimit=0 Should make it harder (at lest a bit) for attackers. 5$ for fix pls.
  11. Sherer

    open can't I get a long long data type?

    % is a format specifier. Take a look at this:
  12. Sherer


    The error lies here: if chr.IsNPC(dstChrID): if app.ENABLE_REFINE_RENEWAL: Either use "or" or add tabs into code below.
  13. Sherer


    What's the difference between server "A" and server "B"?
  14. Sherer

    Gameforge again

  15. Sherer

    How I can use this?

    I don't think it's gonna fix anything but you can try..