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authorEmma Miler <emma.pi@protonmail.com>2022-12-19 19:32:16 +0100
committerGitHub <noreply@github.com>2022-12-19 19:32:16 +0100
commite04f3b36accccb590a2d51b4829256b9964ac3fd (patch)
tree20ee30c82e6f53e6e772be2e1b9613eebca12bf3 /NorthstarDLL/shared/exploit_fixes/exploitfixes.cpp
parent33f18a735986dcd136bf8ba70ad8331306c28227 (diff)
downloadNorthstarLauncher-e04f3b36accccb590a2d51b4829256b9964ac3fd.tar.gz
NorthstarLauncher-e04f3b36accccb590a2d51b4829256b9964ac3fd.zip
Restructuring (#365)
* Remove launcher proxy * Restructuring * More restructuring * Fix include dirs * Fix merge * Remove clang thing * Filters * Oops
Diffstat (limited to 'NorthstarDLL/shared/exploit_fixes/exploitfixes.cpp')
-rw-r--r--NorthstarDLL/shared/exploit_fixes/exploitfixes.cpp458
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");
+}