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/*
* Copyright © 2024 Michael Smith <mikesmiffy128@gmail.com>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
* REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
* OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
* PERFORMANCE OF THIS SOFTWARE.
*/
#include <stdbool.h>
#include <Windows.h>
#include "fakeiat.h"
#include "intdefs.h"
extern struct HINSTANCE__ __ImageBase;
struct _fakeiat IAT;
static int len(const ushort *s) {
int i = 0;
for (; *s; ++s) ++i;
return i;
}
static _Noreturn void die(int status, const ushort *message) {
MessageBoxW(0, message, L"Thread fix wrapper error", 0);
ExitProcess(status);
}
__declspec(noinline) int __stdcall injectedentry(int unused); // injected.c
static void *rpc(void *proc, void *rfunc, void *rparam, const ushort *errstr) {
void *rthread = CreateRemoteThread(proc, 0, 32768,
(LPTHREAD_START_ROUTINE)rfunc, rparam, 0, 0);
if (!rthread) {
TerminateProcess(proc, -1);
die(100, errstr);
}
WaitForSingleObject(rthread, INFINITE);
void *ret;
GetExitCodeThread(rthread, (ulong *)&ret);
return ret;
}
// main EXE entry point. this seems not to get called when we're LoadLibrary'd!
_Noreturn void __stdcall WinMainCRTStartup(void) {
ushort name[MAX_PATH], origname[MAX_PATH];
ushort cmdline[32678];
ushort *myargs = GetCommandLineW();
bool quote = false, oddslash = false;
for (;; ++myargs) {
if (*myargs == '\0') die(1, L"Unexpected end of command line");
if (*myargs == '\\') {
oddslash = !oddslash;
}
else {
if (*myargs == '"') { if (!oddslash) quote = !quote; }
else if ((*myargs == ' ' || *myargs == '\t') && !quote) break;
oddslash = false;
}
}
while (*++myargs == ' ' || *myargs == '\t');
if (len(myargs) > 32767 - MAX_PATH - sizeof("\"\"-steam -insecure ") - 1) {
die(1, L"Command line is too long");
}
int namelen = GetModuleFileNameW(0, name, MAX_PATH);
if (namelen < sizeof("x.wrap.exe") - 1 ||
memcmp(name + namelen - 9, L".wrap.exe", 9)) {
die(2, L"Wrapper name must end in .wrap.exe");
}
cmdline[0] = L'"';
int i = 0;
for (; i < namelen - 9; ++i) {
origname[i] = name[i];
cmdline[i + 1] = name[i]; // XXX: assuming no quotes etc. prolly fine?
}
memcpy(origname + i, L".exe", 4 * sizeof(*origname));
memcpy(cmdline + i + 1, L".exe\" -steam -insecure ", 23 * sizeof(*cmdline));
const ushort *p = myargs; ushort *q = cmdline + i + 24;
do *q++ = *p; while (*p++);
PROCESS_INFORMATION info;
STARTUPINFOW startinfo = {.cb = sizeof(startinfo)};
if (!CreateProcessW(origname, cmdline, 0, 0, 0, CREATE_SUSPENDED, 0, 0,
&startinfo, &info)) {
die(100, L"Couldn't start subprocess");
}
// avoid any possible thunky weirdness using GPA rather than &LoadLibraryW
void *k32 = GetModuleHandleW(L"kernel32.dll");
if (!k32) die(100, L"Couldn't get kernel32 module; everything is on fire!");
void *lladdr = (void *)GetProcAddress(k32, "LoadLibraryW");
int namebytes = (namelen + 1) * sizeof(*name);
int rsize = sizeof("ThreadFixEntryPoint");
if (namebytes > rsize) rsize = namebytes;
void *rmem = VirtualAllocEx(info.hProcess, 0, rsize,
MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
if (!rmem) {
TerminateProcess(info.hProcess, -1);
die(100, L"Couldn't allocate memory in subprocess");
}
WriteProcessMemory(info.hProcess, rmem, name, namebytes, 0);
void *rdll = rpc(info.hProcess, lladdr, rmem,
L"Couldn't call LoadLibrary in subprocess");
if (!rdll) {
TerminateProcess(info.hProcess, -1);
die(100, L"LoadLibrary call in subprocess returned an error");
}
// injectentry will be at the same offset, just a different base
void *rfunc = (char *)rdll + ((char *)&injectedentry - (char *)&__ImageBase);
VirtualFreeEx(info.hProcess, rmem, rsize, MEM_RELEASE);
// Fill out the "fake IAT" table and use WPM to copy it to the injected side
// of things. See fakeiat.h for more exposition.
#define PUTIAT(f) IAT.f = (_iat_##f##_func)GetProcAddress(k32, #f)
PUTIAT(GetSystemInfo);
PUTIAT(FlushInstructionCache);
PUTIAT(VirtualProtect);
#undef PUTIAT
IAT.GetSystemInfo = (_iat_GetSystemInfo_func)GetProcAddress(
k32, "GetSystemInfo");
IAT.FlushInstructionCache = (_iat_FlushInstructionCache_func)GetProcAddress(
k32, "FlushInstructionCache");
IAT.VirtualProtect = (_iat_VirtualProtect_func)GetProcAddress(
k32, "VirtualProtect");
IAT.FlushInstructionCache = &FlushInstructionCache;
IAT.VirtualProtect = &VirtualProtect;
void *riat = (char *)rdll + ((char *)&IAT - (char *)&__ImageBase);
WriteProcessMemory(info.hProcess, riat, &IAT, sizeof(IAT), 0);
if (!rpc(info.hProcess, rfunc, 0,
L"Couldn't call injected entry point in subprocess")) {
die(100, L"Injected code failed to hook GetSystemInfo");
}
ResumeThread(info.hThread);
CloseHandle(info.hThread);
WaitForSingleObject(info.hProcess, INFINITE);
ulong status;
GetExitCodeProcess(info.hProcess, &status);
ExitProcess(status);
}
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