diff options
Diffstat (limited to 'NorthstarDLL/shared/exploit_fixes/exploitfixes.cpp')
| -rw-r--r-- | NorthstarDLL/shared/exploit_fixes/exploitfixes.cpp | 458 |
1 files changed, 458 insertions, 0 deletions
diff --git a/NorthstarDLL/shared/exploit_fixes/exploitfixes.cpp b/NorthstarDLL/shared/exploit_fixes/exploitfixes.cpp new file mode 100644 index 00000000..e4430fd4 --- /dev/null +++ b/NorthstarDLL/shared/exploit_fixes/exploitfixes.cpp @@ -0,0 +1,458 @@ +#include "pch.h" +#include "core/convar/cvar.h" +#include "ns_limits.h" +#include "dedicated/dedicated.h" +#include "core/tier0.h" +#include "engine/r2engine.h" +#include "client/r2client.h" +#include "core/math/vector.h" + +AUTOHOOK_INIT() + +ConVar* Cvar_ns_exploitfixes_log; +ConVar* Cvar_ns_should_log_all_clientcommands; + +ConVar* Cvar_sv_cheats; + +#define BLOCKED_INFO(s) \ + ( \ + [=]() -> bool \ + { \ + if (Cvar_ns_exploitfixes_log->GetBool()) \ + { \ + std::stringstream stream; \ + stream << "ExploitFixes.cpp: " << BLOCK_PREFIX << s; \ + spdlog::error(stream.str()); \ + } \ + return false; \ + }()) + +// block bad netmessages +// Servers can literally request a screenshot from any client, yeah no +// clang-format off +AUTOHOOK(CLC_Screenshot_WriteToBuffer, engine.dll + 0x22AF20, +bool, __fastcall, (void* thisptr, void* buffer)) // 48 89 5C 24 ? 57 48 83 EC 20 8B 42 10 +// clang-format on +{ + return false; +} + +// clang-format off +AUTOHOOK(CLC_Screenshot_ReadFromBuffer, engine.dll + 0x221F00, +bool, __fastcall, (void* thisptr, void* buffer)) // 48 89 5C 24 ? 48 89 6C 24 ? 48 89 74 24 ? 57 48 83 EC 20 48 8B DA 48 8B 52 38 +// clang-format on +{ + return false; +} + +// This is unused ingame and a big client=>server=>client exploit vector +// clang-format off +AUTOHOOK(Base_CmdKeyValues_ReadFromBuffer, engine.dll + 0x220040, +bool, __fastcall, (void* thisptr, void* buffer)) // 40 55 48 81 EC ? ? ? ? 48 8D 6C 24 ? 48 89 5D 70 +// clang-format on +{ + return false; +} + +// clang-format off +AUTOHOOK(CClient_ProcessSetConVar, engine.dll + 0x75CF0, +bool, __fastcall, (void* pMsg)) // 48 8B D1 48 8B 49 18 48 8B 01 48 FF 60 10 +// clang-format on +{ + + constexpr int ENTRY_STR_LEN = 260; + struct SetConVarEntry + { + char name[ENTRY_STR_LEN]; + char val[ENTRY_STR_LEN]; + }; + + struct NET_SetConVar + { + void* vtable; + void* unk1; + void* unk2; + void* m_pMessageHandler; + SetConVarEntry* m_ConVars; // convar entry array + void* unk5; // these 2 unks are just vector capacity or whatever + void* unk6; + int m_ConVars_count; // amount of cvar entries in array (this will not be out of bounds) + }; + + auto msg = (NET_SetConVar*)pMsg; + bool bIsServerFrame = Tier0::ThreadInServerFrameThread(); + + std::string BLOCK_PREFIX = + std::string {"NET_SetConVar ("} + (bIsServerFrame ? "server" : "client") + "): Blocked dangerous/invalid msg: "; + + if (bIsServerFrame) + { + constexpr int SETCONVAR_SANITY_AMOUNT_LIMIT = 69; + if (msg->m_ConVars_count < 1 || msg->m_ConVars_count > SETCONVAR_SANITY_AMOUNT_LIMIT) + { + return BLOCKED_INFO("Invalid m_ConVars_count (" << msg->m_ConVars_count << ")"); + } + } + + for (int i = 0; i < msg->m_ConVars_count; i++) + { + auto entry = msg->m_ConVars + i; + + // Safety check for memory access + if (MemoryAddress(entry).IsMemoryReadable(sizeof(*entry))) + { + // Find null terminators + bool nameValid = false, valValid = false; + for (int i = 0; i < ENTRY_STR_LEN; i++) + { + if (!entry->name[i]) + nameValid = true; + if (!entry->val[i]) + valValid = true; + } + + if (!nameValid || !valValid) + return BLOCKED_INFO("Missing null terminators"); + + ConVar* pVar = R2::g_pCVar->FindVar(entry->name); + + if (pVar) + { + memcpy( + entry->name, + pVar->m_ConCommandBase.m_pszName, + strlen(pVar->m_ConCommandBase.m_pszName) + 1); // Force name to match case + + int iFlags = bIsServerFrame ? FCVAR_USERINFO : FCVAR_REPLICATED; + if (!pVar->IsFlagSet(iFlags)) + return BLOCKED_INFO( + "Invalid flags (" << std::hex << "0x" << pVar->m_ConCommandBase.m_nFlags << "), var is " << entry->name); + } + } + else + { + return BLOCKED_INFO("Unreadable memory at " << (void*)entry); // Not risking that one, they all gotta be readable + } + } + + return CClient_ProcessSetConVar(msg); +} + +// prevent invalid user CMDs +// clang-format off +AUTOHOOK(CClient_ProcessUsercmds, engine.dll + 0x1040F0, +bool, __fastcall, (void* thisptr, void* pMsg)) // 40 55 56 48 83 EC 58 +// clang-format on +{ + struct CLC_Move + { + BYTE gap0[24]; + void* m_pMessageHandler; + int m_nBackupCommands; + int m_nNewCommands; + int m_nLength; + // bf_read m_DataIn; + // bf_write m_DataOut; + }; + + auto msg = (CLC_Move*)pMsg; + + const char* BLOCK_PREFIX = "ProcessUserCmds: "; + + if (msg->m_nBackupCommands < 0) + { + return BLOCKED_INFO("Invalid m_nBackupCommands (" << msg->m_nBackupCommands << ")"); + } + + if (msg->m_nNewCommands < 0) + { + return BLOCKED_INFO("Invalid m_nNewCommands (" << msg->m_nNewCommands << ")"); + } + + if (msg->m_nLength <= 0) + return BLOCKED_INFO("Invalid message length (" << msg->m_nLength << ")"); + + return CClient_ProcessUsercmds(thisptr, pMsg); +} + +// clang-format off +AUTOHOOK(ReadUsercmd, server.dll + 0x2603F0, +void, __fastcall, (void* buf, void* pCmd_move, void* pCmd_from)) // 4C 89 44 24 ? 53 55 56 57 +// clang-format on +{ + // Let normal usercmd read happen first, it's safe + ReadUsercmd(buf, pCmd_move, pCmd_from); + + // Now let's make sure the CMD we read isnt messed up to prevent numerous exploits (including server crashing) + struct alignas(4) SV_CUserCmd + { + DWORD command_number; + DWORD tick_count; + float command_time; + Vector3 worldViewAngles; + BYTE gap18[4]; + Vector3 localViewAngles; + Vector3 attackangles; + Vector3 move; + DWORD buttons; + BYTE impulse; + short weaponselect; + DWORD meleetarget; + BYTE gap4C[24]; + char headoffset; + BYTE gap65[11]; + Vector3 cameraPos; + Vector3 cameraAngles; + BYTE gap88[4]; + int tickSomething; + DWORD dword90; + DWORD predictedServerEventAck; + DWORD dword98; + float frameTime; + }; + + auto cmd = (SV_CUserCmd*)pCmd_move; + auto fromCmd = (SV_CUserCmd*)pCmd_from; + + std::string BLOCK_PREFIX = + "ReadUsercmd (command_number delta: " + std::to_string(cmd->command_number - fromCmd->command_number) + "): "; + + // fix invalid player angles + cmd->worldViewAngles.MakeValid(); + cmd->attackangles.MakeValid(); + cmd->localViewAngles.MakeValid(); + + // Fix invalid camera angles + cmd->cameraPos.MakeValid(); + cmd->cameraAngles.MakeValid(); + + // Fix invaid movement vector + cmd->move.MakeValid(); + + if (cmd->frameTime <= 0 || cmd->tick_count == 0 || cmd->command_time <= 0) + { + BLOCKED_INFO( + "Bogus cmd timing (tick_count: " << cmd->tick_count << ", frameTime: " << cmd->frameTime + << ", commandTime : " << cmd->command_time << ")"); + goto INVALID_CMD; // No simulation of bogus-timed cmds + } + + return; + +INVALID_CMD: + + // Fix any gameplay-affecting cmd properties + // NOTE: Currently tickcount/frametime is set to 0, this ~shouldn't~ cause any problems + cmd->worldViewAngles = cmd->localViewAngles = cmd->attackangles = cmd->cameraAngles = {0, 0, 0}; + cmd->tick_count = cmd->frameTime = 0; + cmd->move = cmd->cameraPos = {0, 0, 0}; + cmd->buttons = 0; + cmd->meleetarget = 0; +} + +// ensure that GetLocalBaseClient().m_bRestrictServerCommands is set correctly, which the return value of this function controls +// this is IsValveMod in source, but we're making it IsRespawnMod now since valve didn't make this one +// clang-format off +AUTOHOOK(IsRespawnMod, engine.dll + 0x1C6360, +bool, __fastcall, (const char* pModName)) // 48 83 EC 28 48 8B 0D ? ? ? ? 48 8D 15 ? ? ? ? E8 ? ? ? ? 85 C0 74 63 +// clang-format on +{ + // somewhat temp, store the modname here, since we don't have a proper ptr in engine to it rn + int iSize = strlen(pModName); + R2::g_pModName = new char[iSize + 1]; + strcpy(R2::g_pModName, pModName); + + return (!strcmp("r2", pModName) || !strcmp("r1", pModName)) && !Tier0::CommandLine()->CheckParm("-norestrictservercommands"); +} + +// ratelimit stringcmds, and prevent remote clients from calling commands that they shouldn't +bool (*CCommand__Tokenize)(CCommand& self, const char* pCommandString, R2::cmd_source_t commandSource); + +// clang-format off +AUTOHOOK(CGameClient__ExecuteStringCommand, engine.dll + 0x1022E0, +bool, __fastcall, (R2::CBaseClient* self, uint32_t unknown, const char* pCommandString)) +// clang-format on +{ + if (Cvar_ns_should_log_all_clientcommands->GetBool()) + spdlog::info("player {} (UID: {}) sent command: \"{}\"", self->m_Name, self->m_UID, pCommandString); + + if (!g_pServerLimits->CheckStringCommandLimits(self)) + { + R2::CBaseClient__Disconnect(self, 1, "Sent too many stringcmd commands"); + return false; + } + + // verify the command we're trying to execute is FCVAR_GAMEDLL_FOR_REMOTE_CLIENTS, if it's a concommand + char* commandBuf[1040]; // assumedly this is the size of CCommand since we don't have an actual constructor + memset(commandBuf, 0, sizeof(commandBuf)); + CCommand tempCommand = *(CCommand*)&commandBuf; + + if (!CCommand__Tokenize(tempCommand, pCommandString, R2::cmd_source_t::kCommandSrcCode) || !tempCommand.ArgC()) + return false; + + ConCommand* command = R2::g_pCVar->FindCommand(tempCommand.Arg(0)); + + // if the command doesn't exist pass it on to ExecuteStringCommand for script clientcommands and stuff + if (command && !command->IsFlagSet(FCVAR_GAMEDLL_FOR_REMOTE_CLIENTS)) + { + // ensure FCVAR_GAMEDLL concommands without FCVAR_GAMEDLL_FOR_REMOTE_CLIENTS can't be executed by remote clients + if (IsDedicatedServer()) + return false; + + if (strcmp(self->m_UID, R2::g_pLocalPlayerUserID)) + return false; + } + + // check for and block abusable legacy portal 2 commands + // these aren't actually concommands weirdly enough, they seem to just be hardcoded + if (!Cvar_sv_cheats->GetBool()) + { + constexpr const char* blockedCommands[] = { + "emit", // Sound-playing exploit (likely for Portal 2 coop devs testing splitscreen sound or something) + + // These both execute a command for every single entity for some reason, nice one valve + "pre_go_to_hub", + "pre_go_to_calibration", + + "end_movie", // Calls "__MovieFinished" script function, not sure exactly what this does but it certainly isn't needed + "load_recent_checkpoint" // This is the instant-respawn exploit, literally just calls RespawnPlayer() + }; + + int iCmdLength = strlen(tempCommand.Arg(0)); + + bool bIsBadCommand = false; + for (auto& blockedCommand : blockedCommands) + { + if (iCmdLength != strlen(blockedCommand)) + continue; + + for (int i = 0; tempCommand.Arg(0)[i]; i++) + if (tolower(tempCommand.Arg(0)[i]) != blockedCommand[i]) + goto NEXT_COMMAND; // break out of this loop, then go to next command + + // this is a command we need to block + return false; + NEXT_COMMAND:; + } + } + + return CGameClient__ExecuteStringCommand(self, unknown, pCommandString); +} + +// prevent clients from crashing servers through overflowing CNetworkStringTableContainer::WriteBaselines +bool bWasWritingStringTableSuccessful; + +// clang-format off +AUTOHOOK(CBaseClient__SendServerInfo, engine.dll + 0x104FB0, +void, __fastcall, (void* self)) +// clang-format on +{ + bWasWritingStringTableSuccessful = true; + CBaseClient__SendServerInfo(self); + if (!bWasWritingStringTableSuccessful) + R2::CBaseClient__Disconnect( + self, 1, "Overflowed CNetworkStringTableContainer::WriteBaselines, try restarting your client and reconnecting"); +} + +// return null when GetEntByIndex is passed an index >= 0x4000 +// this is called from exactly 1 script clientcommand that can be given an arbitrary index, and going above 0x4000 crashes +// clang-format off +AUTOHOOK(GetEntByIndex, server.dll + 0x2A8A50, +void*, __fastcall, (int i)) +// clang-format on +{ + const int MAX_ENT_IDX = 0x4000; + + if (i >= MAX_ENT_IDX) + { + spdlog::warn("GetEntByIndex {} is out of bounds (max {})", i, MAX_ENT_IDX); + return nullptr; + } + + return GetEntByIndex(i); +} +// clang-format off +AUTOHOOK(CL_CopyExistingEntity, engine.dll + 0x6F940, +bool, __fastcall, (void* a1)) +// clang-format on +{ + struct CEntityReadInfo + { + BYTE gap[40]; + int nNewEntity; + }; + + CEntityReadInfo* pReadInfo = (CEntityReadInfo*)a1; + if (pReadInfo->nNewEntity >= 0x1000 || pReadInfo->nNewEntity < 0) + { + // Value isn't sanitized in release builds for + // every game powered by the Source Engine 1 + // causing read/write outside of array bounds. + // This defect has let to the achievement of a + // full-chain RCE exploit. We hook and perform + // sanity checks for the value of m_nNewEntity + // here to prevent this behavior from happening. + return false; + } + + return CL_CopyExistingEntity(a1); +} + +ON_DLL_LOAD("engine.dll", EngineExploitFixes, (CModule module)) +{ + AUTOHOOK_DISPATCH_MODULE(engine.dll) + + CCommand__Tokenize = module.Offset(0x418380).As<bool (*)(CCommand&, const char*, R2::cmd_source_t)>(); + + // allow client/ui to run clientcommands despite restricting servercommands + module.Offset(0x4FB65).Patch("EB 11"); + module.Offset(0x4FBAC).Patch("EB 16"); + + // patch to set bWasWritingStringTableSuccessful in CNetworkStringTableContainer::WriteBaselines if it fails + { + MemoryAddress writeAddress(&bWasWritingStringTableSuccessful - module.Offset(0x234EDC).m_nAddress); + + MemoryAddress addr = module.Offset(0x234ED2); + addr.Patch("C7 05"); + addr.Offset(2).Patch((BYTE*)&writeAddress, sizeof(writeAddress)); + + addr.Offset(6).Patch("00 00 00 00"); + + addr.Offset(10).NOP(5); + } +} + +ON_DLL_LOAD_RELIESON("server.dll", ServerExploitFixes, ConVar, (CModule module)) +{ + AUTOHOOK_DISPATCH_MODULE(server.dll) + + // ret at the start of CServerGameClients::ClientCommandKeyValues as it has no benefit and is forwarded to client (i.e. security issue) + // this prevents the attack vector of client=>server=>client, however server=>client also has clientside patches + module.Offset(0x153920).Patch("C3"); + + // Dumb ANTITAMPER patches (they negatively impact performance and security) + constexpr const char* ANTITAMPER_EXPORTS[] = { + "ANTITAMPER_SPOTCHECK_CODEMARKER", + "ANTITAMPER_TESTVALUE_CODEMARKER", + "ANTITAMPER_TRIGGER_CODEMARKER", + }; + + // Prevent these from actually doing anything + for (auto exportName : ANTITAMPER_EXPORTS) + { + MemoryAddress exportAddr = module.GetExport(exportName); + if (exportAddr) + { + // Just return, none of them have any args or are userpurge + exportAddr.Patch("C3"); + spdlog::info("Patched AntiTamper function export \"{}\"", exportName); + } + } + + Cvar_ns_exploitfixes_log = + new ConVar("ns_exploitfixes_log", "1", FCVAR_GAMEDLL, "Whether to log whenever ExploitFixes.cpp blocks/corrects something"); + Cvar_ns_should_log_all_clientcommands = + new ConVar("ns_should_log_all_clientcommands", "0", FCVAR_NONE, "Whether to log all clientcommands"); + + Cvar_sv_cheats = R2::g_pCVar->FindVar("sv_cheats"); +} |