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680 lines
19 KiB
C++
680 lines
19 KiB
C++
/* -*- Mode: C++; tab-width: 40; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef NS_WINDOWS_DLL_INTERCEPTOR_H_
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#define NS_WINDOWS_DLL_INTERCEPTOR_H_
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#include <windows.h>
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#include <winternl.h>
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/*
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* Simple function interception.
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*
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* We have two separate mechanisms for intercepting a function: We can use the
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* built-in nop space, if it exists, or we can create a detour.
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*
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* Using the built-in nop space works as follows: On x86-32, DLL functions
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* begin with a two-byte nop (mov edi, edi) and are preceeded by five bytes of
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* NOP instructions.
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*
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* When we detect a function with this prelude, we do the following:
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*
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* 1. Write a long jump to our interceptor function into the five bytes of NOPs
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* before the function.
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*
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* 2. Write a short jump -5 into the two-byte nop at the beginning of the function.
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*
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* This mechanism is nice because it's thread-safe. It's even safe to do if
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* another thread is currently running the function we're modifying!
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*
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* When the WindowsDllNopSpacePatcher is destroyed, we overwrite the short jump
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* but not the long jump, so re-intercepting the same function won't work,
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* because its prelude won't match.
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*
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*
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* Unfortunately nop space patching doesn't work on functions which don't have
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* this magic prelude (and in particular, x86-64 never has the prelude). So
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* when we can't use the built-in nop space, we fall back to using a detour,
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* which works as follows:
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*
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* 1. Save first N bytes of OrigFunction to trampoline, where N is a
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* number of bytes >= 5 that are instruction aligned.
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*
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* 2. Replace first 5 bytes of OrigFunction with a jump to the Hook
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* function.
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*
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* 3. After N bytes of the trampoline, add a jump to OrigFunction+N to
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* continue original program flow.
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*
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* 4. Hook function needs to call the trampoline during its execution,
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* to invoke the original function (so address of trampoline is
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* returned).
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*
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* When the WindowsDllDetourPatcher object is destructed, OrigFunction is
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* patched again to jump directly to the trampoline instead of going through
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* the hook function. As such, re-intercepting the same function won't work, as
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* jump instructions are not supported.
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*
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* Note that this is not thread-safe. Sad day.
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*
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*/
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#include <mozilla/StandardInteger.h>
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namespace mozilla {
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namespace internal {
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class WindowsDllNopSpacePatcher
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{
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typedef unsigned char *byteptr_t;
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HMODULE mModule;
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// Dumb array for remembering the addresses of functions we've patched.
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// (This should be nsTArray, but non-XPCOM code uses this class.)
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static const size_t maxPatchedFns = 128;
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byteptr_t mPatchedFns[maxPatchedFns];
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int mPatchedFnsLen;
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public:
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WindowsDllNopSpacePatcher()
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: mModule(0)
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, mPatchedFnsLen(0)
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{}
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~WindowsDllNopSpacePatcher()
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{
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// Restore the mov edi, edi to the beginning of each function we patched.
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for (int i = 0; i < mPatchedFnsLen; i++) {
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byteptr_t fn = mPatchedFns[i];
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// Ensure we can write to the code.
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DWORD op;
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if (!VirtualProtectEx(GetCurrentProcess(), fn, 2, PAGE_EXECUTE_READWRITE, &op)) {
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// printf("VirtualProtectEx failed! %d\n", GetLastError());
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continue;
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}
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// mov edi, edi
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*((uint16_t*)fn) = 0xff8b;
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// Restore the old protection.
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VirtualProtectEx(GetCurrentProcess(), fn, 2, op, &op);
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// I don't think this is actually necessary, but it can't hurt.
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FlushInstructionCache(GetCurrentProcess(),
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/* ignored */ NULL,
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/* ignored */ 0);
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}
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}
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void Init(const char *modulename)
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{
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mModule = LoadLibraryExA(modulename, NULL, 0);
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if (!mModule) {
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//printf("LoadLibraryEx for '%s' failed\n", modulename);
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return;
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}
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}
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#if defined(_M_IX86)
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bool AddHook(const char *pname, intptr_t hookDest, void **origFunc)
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{
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if (!mModule)
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return false;
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if (mPatchedFnsLen == maxPatchedFns) {
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// printf ("No space for hook in mPatchedFns.\n");
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return false;
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}
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byteptr_t fn = reinterpret_cast<byteptr_t>(GetProcAddress(mModule, pname));
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if (!fn) {
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//printf ("GetProcAddress failed\n");
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return false;
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}
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// Ensure we can read and write starting at fn - 5 (for the long jmp we're
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// going to write) and ending at fn + 2 (for the short jmp up to the long
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// jmp).
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DWORD op;
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if (!VirtualProtectEx(GetCurrentProcess(), fn - 5, 7, PAGE_EXECUTE_READWRITE, &op)) {
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//printf ("VirtualProtectEx failed! %d\n", GetLastError());
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return false;
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}
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bool rv = WriteHook(fn, hookDest, origFunc);
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// Re-protect, and we're done.
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VirtualProtectEx(GetCurrentProcess(), fn - 5, 7, op, &op);
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if (rv) {
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mPatchedFns[mPatchedFnsLen] = fn;
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mPatchedFnsLen++;
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}
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return rv;
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}
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bool WriteHook(byteptr_t fn, intptr_t hookDest, void **origFunc)
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{
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// Check that the 5 bytes before fn are NOP's, and that the 2 bytes after
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// fn are mov(edi, edi).
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//
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// It's safe to read fn[-5] because we set it to PAGE_EXECUTE_READWRITE
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// before calling WriteHook.
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for (int i = -5; i <= -1; i++) {
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if (fn[i] != 0x90) // nop
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return false;
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}
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// mov edi, edi. Yes, there are two ways to encode the same thing:
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//
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// 0x89ff == mov r/m, r
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// 0x8bff == mov r, r/m
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//
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// where "r" is register and "r/m" is register or memory. Windows seems to
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// use 8bff; I include 89ff out of paranoia.
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if ((fn[0] != 0x8b && fn[0] != 0x89) || fn[1] != 0xff) {
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return false;
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}
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// Write a long jump into the space above the function.
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fn[-5] = 0xe9; // jmp
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*((intptr_t*)(fn - 4)) = hookDest - (uintptr_t)(fn); // target displacement
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// Set origFunc here, because after this point, hookDest might be called,
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// and hookDest might use the origFunc pointer.
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*origFunc = fn + 2;
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// Short jump up into our long jump.
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*((uint16_t*)(fn)) = 0xf9eb; // jmp $-5
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// I think this routine is safe without this, but it can't hurt.
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FlushInstructionCache(GetCurrentProcess(),
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/* ignored */ NULL,
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/* ignored */ 0);
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return true;
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}
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#else
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bool AddHook(const char *pname, intptr_t hookDest, void **origFunc)
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{
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// Not implemented except on x86-32.
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return false;
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}
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#endif
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};
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class WindowsDllDetourPatcher
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{
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typedef unsigned char *byteptr_t;
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public:
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WindowsDllDetourPatcher()
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: mModule(0), mHookPage(0), mMaxHooks(0), mCurHooks(0)
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{
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}
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~WindowsDllDetourPatcher()
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{
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int i;
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byteptr_t p;
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for (i = 0, p = mHookPage; i < mCurHooks; i++, p += kHookSize) {
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#if defined(_M_IX86)
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size_t nBytes = 1 + sizeof(intptr_t);
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#elif defined(_M_X64)
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size_t nBytes = 2 + sizeof(intptr_t);
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#else
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#error "Unknown processor type"
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#endif
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byteptr_t origBytes = *((byteptr_t *)p);
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// ensure we can modify the original code
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DWORD op;
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if (!VirtualProtectEx(GetCurrentProcess(), origBytes, nBytes, PAGE_EXECUTE_READWRITE, &op)) {
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//printf ("VirtualProtectEx failed! %d\n", GetLastError());
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continue;
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}
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// Remove the hook by making the original function jump directly
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// in the trampoline.
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intptr_t dest = (intptr_t)(p + sizeof(void *));
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#if defined(_M_IX86)
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*((intptr_t*)(origBytes+1)) = dest - (intptr_t)(origBytes+5); // target displacement
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#elif defined(_M_X64)
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*((intptr_t*)(origBytes+2)) = dest;
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#else
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#error "Unknown processor type"
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#endif
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// restore protection; if this fails we can't really do anything about it
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VirtualProtectEx(GetCurrentProcess(), origBytes, nBytes, op, &op);
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}
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}
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void Init(const char *modulename, int nhooks = 0)
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{
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if (mModule)
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return;
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mModule = LoadLibraryExA(modulename, NULL, 0);
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if (!mModule) {
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//printf("LoadLibraryEx for '%s' failed\n", modulename);
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return;
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}
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int hooksPerPage = 4096 / kHookSize;
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if (nhooks == 0)
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nhooks = hooksPerPage;
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mMaxHooks = nhooks + (hooksPerPage % nhooks);
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mHookPage = (byteptr_t) VirtualAllocEx(GetCurrentProcess(), NULL, mMaxHooks * kHookSize,
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MEM_COMMIT | MEM_RESERVE,
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PAGE_EXECUTE_READWRITE);
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if (!mHookPage) {
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mModule = 0;
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return;
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}
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}
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bool Initialized()
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{
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return !!mModule;
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}
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void LockHooks()
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{
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if (!mModule)
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return;
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DWORD op;
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VirtualProtectEx(GetCurrentProcess(), mHookPage, mMaxHooks * kHookSize, PAGE_EXECUTE_READ, &op);
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mModule = 0;
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}
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bool AddHook(const char *pname, intptr_t hookDest, void **origFunc)
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{
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if (!mModule)
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return false;
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void *pAddr = (void *) GetProcAddress(mModule, pname);
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if (!pAddr) {
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//printf ("GetProcAddress failed\n");
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return false;
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}
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CreateTrampoline(pAddr, hookDest, origFunc);
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if (!*origFunc) {
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//printf ("CreateTrampoline failed\n");
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return false;
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}
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return true;
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}
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protected:
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const static int kPageSize = 4096;
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const static int kHookSize = 128;
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HMODULE mModule;
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byteptr_t mHookPage;
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int mMaxHooks;
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int mCurHooks;
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void CreateTrampoline(void *origFunction,
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intptr_t dest,
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void **outTramp)
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{
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*outTramp = NULL;
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byteptr_t tramp = FindTrampolineSpace();
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if (!tramp)
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return;
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byteptr_t origBytes = (byteptr_t) origFunction;
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int nBytes = 0;
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int pJmp32 = -1;
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#if defined(_M_IX86)
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while (nBytes < 5) {
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// Understand some simple instructions that might be found in a
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// prologue; we might need to extend this as necessary.
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//
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// Note! If we ever need to understand jump instructions, we'll
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// need to rewrite the displacement argument.
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if (origBytes[nBytes] >= 0x88 && origBytes[nBytes] <= 0x8B) {
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// various MOVs
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unsigned char b = origBytes[nBytes+1];
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if (((b & 0xc0) == 0xc0) ||
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(((b & 0xc0) == 0x00) &&
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((b & 0x07) != 0x04) && ((b & 0x07) != 0x05)))
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{
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// REG=r, R/M=r or REG=r, R/M=[r]
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nBytes += 2;
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} else if (((b & 0xc0) == 0x40) && ((b & 0x38) != 0x20)) {
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// REG=r, R/M=[r + disp8]
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nBytes += 3;
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} else {
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// complex MOV, bail
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return;
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}
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} else if (origBytes[nBytes] == 0xB8) {
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// MOV 0xB8: http://ref.x86asm.net/coder32.html#xB8
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nBytes += 5;
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} else if (origBytes[nBytes] == 0x83) {
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// ADD|ODR|ADC|SBB|AND|SUB|XOR|CMP r/m, imm8
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unsigned char b = origBytes[nBytes+1];
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if ((b & 0xc0) == 0xc0) {
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// ADD|ODR|ADC|SBB|AND|SUB|XOR|CMP r, imm8
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nBytes += 3;
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} else {
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// bail
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return;
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}
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} else if (origBytes[nBytes] == 0x68) {
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// PUSH with 4-byte operand
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nBytes += 5;
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} else if ((origBytes[nBytes] & 0xf0) == 0x50) {
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// 1-byte PUSH/POP
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nBytes++;
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} else if (origBytes[nBytes] == 0x6A) {
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// PUSH imm8
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nBytes += 2;
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} else if (origBytes[nBytes] == 0xe9) {
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pJmp32 = nBytes;
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// jmp 32bit offset
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nBytes += 5;
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} else {
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//printf ("Unknown x86 instruction byte 0x%02x, aborting trampoline\n", origBytes[nBytes]);
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return;
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}
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}
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#elif defined(_M_X64)
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while (nBytes < 13) {
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// if found JMP 32bit offset, next bytes must be NOP
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if (pJmp32 >= 0) {
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if (origBytes[nBytes++] != 0x90)
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return;
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continue;
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}
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if (origBytes[nBytes] == 0x0f) {
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nBytes++;
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if (origBytes[nBytes] == 0x1f) {
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// nop (multibyte)
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nBytes++;
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if ((origBytes[nBytes] & 0xc0) == 0x40 &&
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(origBytes[nBytes] & 0x7) == 0x04) {
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nBytes += 3;
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} else {
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return;
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}
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} else if (origBytes[nBytes] == 0x05) {
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// syscall
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nBytes++;
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} else {
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return;
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}
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} else if (origBytes[nBytes] == 0x41) {
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// REX.B
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nBytes++;
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if ((origBytes[nBytes] & 0xf0) == 0x50) {
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// push/pop with Rx register
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nBytes++;
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} else if (origBytes[nBytes] >= 0xb8 && origBytes[nBytes] <= 0xbf) {
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// mov r32, imm32
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nBytes += 5;
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} else {
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return;
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}
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} else if (origBytes[nBytes] == 0x45) {
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// REX.R & REX.B
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nBytes++;
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if (origBytes[nBytes] == 0x33) {
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// xor r32, r32
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nBytes += 2;
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} else {
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return;
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}
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} else if ((origBytes[nBytes] & 0xfb) == 0x48) {
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// REX.W | REX.WR
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nBytes++;
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if (origBytes[nBytes] == 0x81 && (origBytes[nBytes+1] & 0xf8) == 0xe8) {
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// sub r, dword
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nBytes += 6;
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} else if (origBytes[nBytes] == 0x83 &&
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(origBytes[nBytes+1] & 0xf8) == 0xe8) {
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// sub r, byte
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nBytes += 3;
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} else if (origBytes[nBytes] == 0x83 &&
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(origBytes[nBytes+1] & 0xf8) == 0x60) {
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// and [r+d], imm8
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nBytes += 5;
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} else if ((origBytes[nBytes] & 0xfd) == 0x89) {
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// MOV r/m64, r64 | MOV r64, r/m64
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if ((origBytes[nBytes+1] & 0xc0) == 0x40) {
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if ((origBytes[nBytes+1] & 0x7) == 0x04) {
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// R/M=[SIB+disp8], REG=r64
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nBytes += 4;
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} else {
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// R/M=[r64+disp8], REG=r64
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nBytes += 3;
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}
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} else if (((origBytes[nBytes+1] & 0xc0) == 0xc0) ||
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(((origBytes[nBytes+1] & 0xc0) == 0x00) &&
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((origBytes[nBytes+1] & 0x07) != 0x04) && ((origBytes[nBytes+1] & 0x07) != 0x05))) {
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// REG=r64, R/M=r64 or REG=r64, R/M=[r64]
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nBytes += 2;
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} else {
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// complex MOV
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return;
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}
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} else if (origBytes[nBytes] == 0xc7) {
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// MOV r/m64, imm32
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if (origBytes[nBytes + 1] & 0xf8 == 0x40) {
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nBytes += 6;
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} else {
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return;
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}
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} else {
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// not support yet!
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return;
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}
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} else if ((origBytes[nBytes] & 0xf0) == 0x50) {
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// 1-byte push/pop
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nBytes++;
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} else if (origBytes[nBytes] == 0x90) {
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// nop
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nBytes++;
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} else if (origBytes[nBytes] == 0xb8) {
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// MOV 0xB8: http://ref.x86asm.net/coder32.html#xB8
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nBytes += 5;
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} else if (origBytes[nBytes] == 0xc3) {
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// ret
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nBytes++;
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} else if (origBytes[nBytes] == 0xe9) {
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pJmp32 = nBytes;
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// jmp 32bit offset
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nBytes += 5;
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} else if (origBytes[nBytes] == 0xff) {
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nBytes++;
|
|
if ((origBytes[nBytes] & 0xf8) == 0xf0) {
|
|
// push r64
|
|
nBytes++;
|
|
} else {
|
|
return;
|
|
}
|
|
} else {
|
|
return;
|
|
}
|
|
}
|
|
#else
|
|
#error "Unknown processor type"
|
|
#endif
|
|
|
|
if (nBytes > 100) {
|
|
//printf ("Too big!");
|
|
return;
|
|
}
|
|
|
|
// We keep the address of the original function in the first bytes of
|
|
// the trampoline buffer
|
|
*((void **)tramp) = origFunction;
|
|
tramp += sizeof(void *);
|
|
|
|
memcpy(tramp, origFunction, nBytes);
|
|
|
|
// OrigFunction+N, the target of the trampoline
|
|
byteptr_t trampDest = origBytes + nBytes;
|
|
|
|
#if defined(_M_IX86)
|
|
if (pJmp32 >= 0) {
|
|
// Jump directly to the original target of the jump instead of jumping to the
|
|
// original function.
|
|
// Adjust jump target displacement to jump location in the trampoline.
|
|
*((intptr_t*)(tramp+pJmp32+1)) += origBytes + pJmp32 - tramp;
|
|
} else {
|
|
tramp[nBytes] = 0xE9; // jmp
|
|
*((intptr_t*)(tramp+nBytes+1)) = (intptr_t)trampDest - (intptr_t)(tramp+nBytes+5); // target displacement
|
|
}
|
|
#elif defined(_M_X64)
|
|
// If JMP32 opcode found, we don't insert to trampoline jump
|
|
if (pJmp32 >= 0) {
|
|
// convert JMP 32bit offset to JMP 64bit direct
|
|
byteptr_t directJmpAddr = origBytes + pJmp32 + 5 + (*((LONG*)(origBytes+pJmp32+1)));
|
|
// mov r11, address
|
|
tramp[pJmp32] = 0x49;
|
|
tramp[pJmp32+1] = 0xbb;
|
|
*((intptr_t*)(tramp+pJmp32+2)) = (intptr_t)directJmpAddr;
|
|
|
|
// jmp r11
|
|
tramp[pJmp32+10] = 0x41;
|
|
tramp[pJmp32+11] = 0xff;
|
|
tramp[pJmp32+12] = 0xe3;
|
|
} else {
|
|
// mov r11, address
|
|
tramp[nBytes] = 0x49;
|
|
tramp[nBytes+1] = 0xbb;
|
|
*((intptr_t*)(tramp+nBytes+2)) = (intptr_t)trampDest;
|
|
|
|
// jmp r11
|
|
tramp[nBytes+10] = 0x41;
|
|
tramp[nBytes+11] = 0xff;
|
|
tramp[nBytes+12] = 0xe3;
|
|
}
|
|
#endif
|
|
|
|
// The trampoline is now valid.
|
|
*outTramp = tramp;
|
|
|
|
// ensure we can modify the original code
|
|
DWORD op;
|
|
if (!VirtualProtectEx(GetCurrentProcess(), origFunction, nBytes, PAGE_EXECUTE_READWRITE, &op)) {
|
|
//printf ("VirtualProtectEx failed! %d\n", GetLastError());
|
|
return;
|
|
}
|
|
|
|
#if defined(_M_IX86)
|
|
// now modify the original bytes
|
|
origBytes[0] = 0xE9; // jmp
|
|
*((intptr_t*)(origBytes+1)) = dest - (intptr_t)(origBytes+5); // target displacement
|
|
#elif defined(_M_X64)
|
|
// mov r11, address
|
|
origBytes[0] = 0x49;
|
|
origBytes[1] = 0xbb;
|
|
|
|
*((intptr_t*)(origBytes+2)) = dest;
|
|
|
|
// jmp r11
|
|
origBytes[10] = 0x41;
|
|
origBytes[11] = 0xff;
|
|
origBytes[12] = 0xe3;
|
|
#endif
|
|
|
|
// restore protection; if this fails we can't really do anything about it
|
|
VirtualProtectEx(GetCurrentProcess(), origFunction, nBytes, op, &op);
|
|
}
|
|
|
|
byteptr_t FindTrampolineSpace()
|
|
{
|
|
if (mCurHooks >= mMaxHooks)
|
|
return 0;
|
|
|
|
byteptr_t p = mHookPage + mCurHooks*kHookSize;
|
|
|
|
mCurHooks++;
|
|
|
|
return p;
|
|
}
|
|
};
|
|
|
|
} // namespace internal
|
|
|
|
class WindowsDllInterceptor
|
|
{
|
|
internal::WindowsDllNopSpacePatcher mNopSpacePatcher;
|
|
internal::WindowsDllDetourPatcher mDetourPatcher;
|
|
|
|
const char *mModuleName;
|
|
int mNHooks;
|
|
|
|
public:
|
|
WindowsDllInterceptor()
|
|
: mModuleName(NULL)
|
|
, mNHooks(0)
|
|
{}
|
|
|
|
void Init(const char *moduleName, int nhooks = 0)
|
|
{
|
|
if (mModuleName) {
|
|
return;
|
|
}
|
|
|
|
mModuleName = moduleName;
|
|
mNHooks = nhooks;
|
|
mNopSpacePatcher.Init(moduleName);
|
|
|
|
// Lazily initialize mDetourPatcher, since it allocates memory and we might
|
|
// not need it.
|
|
}
|
|
|
|
void LockHooks()
|
|
{
|
|
if (mDetourPatcher.Initialized())
|
|
mDetourPatcher.LockHooks();
|
|
}
|
|
|
|
bool AddHook(const char *pname, intptr_t hookDest, void **origFunc)
|
|
{
|
|
if (!mModuleName) {
|
|
// printf("AddHook before initialized?\n");
|
|
return false;
|
|
}
|
|
|
|
if (mNopSpacePatcher.AddHook(pname, hookDest, origFunc)) {
|
|
// printf("nopSpacePatcher succeeded.\n");
|
|
return true;
|
|
}
|
|
|
|
if (!mDetourPatcher.Initialized()) {
|
|
// printf("Initializing detour patcher.\n");
|
|
mDetourPatcher.Init(mModuleName, mNHooks);
|
|
}
|
|
|
|
bool rv = mDetourPatcher.AddHook(pname, hookDest, origFunc);
|
|
// printf("detourPatcher returned %d\n", rv);
|
|
return rv;
|
|
}
|
|
};
|
|
|
|
} // namespace mozilla
|
|
|
|
#endif /* NS_WINDOWS_DLL_INTERCEPTOR_H_ */
|