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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef NS_WINDOWS_DLL_INTERCEPTOR_H_
#define NS_WINDOWS_DLL_INTERCEPTOR_H_
#include <windows.h>
#include <winternl.h>
/*
* Simple function interception.
*
* We have two separate mechanisms for intercepting a function: We can use the
* built-in nop space, if it exists, or we can create a detour.
*
* Using the built-in nop space works as follows: On x86-32, DLL functions
* begin with a two-byte nop (mov edi, edi) and are preceeded by five bytes of
* NOP instructions.
*
* When we detect a function with this prelude, we do the following:
*
* 1. Write a long jump to our interceptor function into the five bytes of NOPs
* before the function.
*
* 2. Write a short jump -5 into the two-byte nop at the beginning of the function.
*
* This mechanism is nice because it's thread-safe. It's even safe to do if
* another thread is currently running the function we're modifying!
*
* When the WindowsDllNopSpacePatcher is destroyed, we overwrite the short jump
* but not the long jump, so re-intercepting the same function won't work,
* because its prelude won't match.
*
*
* Unfortunately nop space patching doesn't work on functions which don't have
* this magic prelude (and in particular, x86-64 never has the prelude). So
* when we can't use the built-in nop space, we fall back to using a detour,
* which works as follows:
*
* 1. Save first N bytes of OrigFunction to trampoline, where N is a
* number of bytes >= 5 that are instruction aligned.
*
* 2. Replace first 5 bytes of OrigFunction with a jump to the Hook
* function.
*
* 3. After N bytes of the trampoline, add a jump to OrigFunction+N to
* continue original program flow.
*
* 4. Hook function needs to call the trampoline during its execution,
* to invoke the original function (so address of trampoline is
* returned).
*
* When the WindowsDllDetourPatcher object is destructed, OrigFunction is
* patched again to jump directly to the trampoline instead of going through
* the hook function. As such, re-intercepting the same function won't work, as
* jump instructions are not supported.
*
* Note that this is not thread-safe. Sad day.
*
*/
#include <stdint.h>
namespace mozilla {
namespace internal {
class AutoVirtualProtect
{
public:
AutoVirtualProtect(void* aFunc, size_t aSize, DWORD aProtect)
: mFunc(aFunc), mSize(aSize), mNewProtect(aProtect), mOldProtect(0),
mSuccess(false)
{}
~AutoVirtualProtect()
{
if (mSuccess) {
VirtualProtectEx(GetCurrentProcess(), mFunc, mSize, mOldProtect,
&mOldProtect);
}
}
bool Protect()
{
mSuccess = !!VirtualProtectEx(GetCurrentProcess(), mFunc, mSize,
mNewProtect, &mOldProtect);
return mSuccess;
}
private:
void* const mFunc;
size_t const mSize;
DWORD const mNewProtect;
DWORD mOldProtect;
bool mSuccess;
};
class WindowsDllNopSpacePatcher
{
typedef unsigned char* byteptr_t;
HMODULE mModule;
// Dumb array for remembering the addresses of functions we've patched.
// (This should be nsTArray, but non-XPCOM code uses this class.)
static const size_t maxPatchedFns = 128;
byteptr_t mPatchedFns[maxPatchedFns];
int mPatchedFnsLen;
public:
WindowsDllNopSpacePatcher()
: mModule(0)
, mPatchedFnsLen(0)
{}
~WindowsDllNopSpacePatcher()
{
// Restore the mov edi, edi to the beginning of each function we patched.
for (int i = 0; i < mPatchedFnsLen; i++) {
byteptr_t fn = mPatchedFns[i];
// Ensure we can write to the code.
AutoVirtualProtect protect(fn, 2, PAGE_EXECUTE_READWRITE);
if (!protect.Protect()) {
// printf("VirtualProtectEx failed! %d\n", GetLastError());
continue;
}
// mov edi, edi
*((uint16_t*)fn) = 0xff8b;
// I don't think this is actually necessary, but it can't hurt.
FlushInstructionCache(GetCurrentProcess(),
/* ignored */ nullptr,
/* ignored */ 0);
}
}
void Init(const char* aModuleName)
{
mModule = LoadLibraryExA(aModuleName, nullptr, 0);
if (!mModule) {
//printf("LoadLibraryEx for '%s' failed\n", aModuleName);
return;
}
}
#if defined(_M_IX86)
bool AddHook(const char* aName, intptr_t aHookDest, void** aOrigFunc)
{
if (!mModule) {
return false;
}
if (mPatchedFnsLen == maxPatchedFns) {
// printf ("No space for hook in mPatchedFns.\n");
return false;
}
byteptr_t fn = reinterpret_cast<byteptr_t>(GetProcAddress(mModule, aName));
if (!fn) {
//printf ("GetProcAddress failed\n");
return false;
}
fn = ResolveRedirectedAddress(fn);
// Ensure we can read and write starting at fn - 5 (for the long jmp we're
// going to write) and ending at fn + 2 (for the short jmp up to the long
// jmp). These bytes may span two pages with different protection.
AutoVirtualProtect protectBefore(fn - 5, 5, PAGE_EXECUTE_READWRITE);
AutoVirtualProtect protectAfter(fn, 2, PAGE_EXECUTE_READWRITE);
if (!protectBefore.Protect() || !protectAfter.Protect()) {
//printf ("VirtualProtectEx failed! %d\n", GetLastError());
return false;
}
bool rv = WriteHook(fn, aHookDest, aOrigFunc);
if (rv) {
mPatchedFns[mPatchedFnsLen] = fn;
mPatchedFnsLen++;
}
return rv;
}
bool WriteHook(byteptr_t aFn, intptr_t aHookDest, void** aOrigFunc)
{
// Check that the 5 bytes before aFn are NOP's or INT 3's,
// and that the 2 bytes after aFn are mov(edi, edi).
//
// It's safe to read aFn[-5] because we set it to PAGE_EXECUTE_READWRITE
// before calling WriteHook.
for (int i = -5; i <= -1; i++) {
if (aFn[i] != 0x90 && aFn[i] != 0xcc) { // nop or int 3
return false;
}
}
// mov edi, edi. Yes, there are two ways to encode the same thing:
//
// 0x89ff == mov r/m, r
// 0x8bff == mov r, r/m
//
// where "r" is register and "r/m" is register or memory. Windows seems to
// use 8bff; I include 89ff out of paranoia.
if ((aFn[0] != 0x8b && aFn[0] != 0x89) || aFn[1] != 0xff) {
return false;
}
// Write a long jump into the space above the function.
aFn[-5] = 0xe9; // jmp
*((intptr_t*)(aFn - 4)) = aHookDest - (uintptr_t)(aFn); // target displacement
// Set aOrigFunc here, because after this point, aHookDest might be called,
// and aHookDest might use the aOrigFunc pointer.
*aOrigFunc = aFn + 2;
// Short jump up into our long jump.
*((uint16_t*)(aFn)) = 0xf9eb; // jmp $-5
// I think this routine is safe without this, but it can't hurt.
FlushInstructionCache(GetCurrentProcess(),
/* ignored */ nullptr,
/* ignored */ 0);
return true;
}
private:
static byteptr_t ResolveRedirectedAddress(const byteptr_t aOriginalFunction)
{
// If function entry is jmp [disp32] such as used by kernel32,
// we resolve redirected address from import table.
if (aOriginalFunction[0] == 0xff && aOriginalFunction[1] == 0x25) {
return (byteptr_t)(**((uint32_t**) (aOriginalFunction + 2)));
}
return aOriginalFunction;
}
#else
bool AddHook(const char* aName, intptr_t aHookDest, void** aOrigFunc)
{
// Not implemented except on x86-32.
return false;
}
#endif
};
class WindowsDllDetourPatcher
{
typedef unsigned char* byteptr_t;
public:
WindowsDllDetourPatcher()
: mModule(0), mHookPage(0), mMaxHooks(0), mCurHooks(0)
{
}
~WindowsDllDetourPatcher()
{
int i;
byteptr_t p;
for (i = 0, p = mHookPage; i < mCurHooks; i++, p += kHookSize) {
#if defined(_M_IX86)
size_t nBytes = 1 + sizeof(intptr_t);
#elif defined(_M_X64)
size_t nBytes = 2 + sizeof(intptr_t);
#else
#error "Unknown processor type"
#endif
byteptr_t origBytes = *((byteptr_t*)p);
// ensure we can modify the original code
AutoVirtualProtect protect(origBytes, nBytes, PAGE_EXECUTE_READWRITE);
if (!protect.Protect()) {
//printf ("VirtualProtectEx failed! %d\n", GetLastError());
continue;
}
// Remove the hook by making the original function jump directly
// in the trampoline.
intptr_t dest = (intptr_t)(p + sizeof(void*));
#if defined(_M_IX86)
*((intptr_t*)(origBytes + 1)) =
dest - (intptr_t)(origBytes + 5); // target displacement
#elif defined(_M_X64)
*((intptr_t*)(origBytes + 2)) = dest;
#else
#error "Unknown processor type"
#endif
}
}
void Init(const char* aModuleName, int aNumHooks = 0)
{
if (mModule) {
return;
}
mModule = LoadLibraryExA(aModuleName, nullptr, 0);
if (!mModule) {
//printf("LoadLibraryEx for '%s' failed\n", aModuleName);
return;
}
int hooksPerPage = 4096 / kHookSize;
if (aNumHooks == 0) {
aNumHooks = hooksPerPage;
}
mMaxHooks = aNumHooks + (hooksPerPage % aNumHooks);
mHookPage = (byteptr_t)VirtualAllocEx(GetCurrentProcess(), nullptr,
mMaxHooks * kHookSize,
MEM_COMMIT | MEM_RESERVE,
PAGE_EXECUTE_READWRITE);
if (!mHookPage) {
mModule = 0;
return;
}
}
bool Initialized() { return !!mModule; }
void LockHooks()
{
if (!mModule) {
return;
}
DWORD op;
VirtualProtectEx(GetCurrentProcess(), mHookPage, mMaxHooks * kHookSize,
PAGE_EXECUTE_READ, &op);
mModule = 0;
}
bool AddHook(const char* aName, intptr_t aHookDest, void** aOrigFunc)
{
if (!mModule) {
return false;
}
void* pAddr = (void*)GetProcAddress(mModule, aName);
if (!pAddr) {
//printf ("GetProcAddress failed\n");
return false;
}
pAddr = ResolveRedirectedAddress((byteptr_t)pAddr);
CreateTrampoline(pAddr, aHookDest, aOrigFunc);
if (!*aOrigFunc) {
//printf ("CreateTrampoline failed\n");
return false;
}
return true;
}
protected:
const static int kPageSize = 4096;
const static int kHookSize = 128;
HMODULE mModule;
byteptr_t mHookPage;
int mMaxHooks;
int mCurHooks;
void CreateTrampoline(void* aOrigFunction, intptr_t aDest, void** aOutTramp)
{
*aOutTramp = nullptr;
byteptr_t tramp = FindTrampolineSpace();
if (!tramp) {
return;
}
byteptr_t origBytes = (byteptr_t)aOrigFunction;
int nBytes = 0;
int pJmp32 = -1;
#if defined(_M_IX86)
while (nBytes < 5) {
// Understand some simple instructions that might be found in a
// prologue; we might need to extend this as necessary.
//
// Note! If we ever need to understand jump instructions, we'll
// need to rewrite the displacement argument.
if (origBytes[nBytes] >= 0x88 && origBytes[nBytes] <= 0x8B) {
// various MOVs
unsigned char b = origBytes[nBytes + 1];
if (((b & 0xc0) == 0xc0) ||
(((b & 0xc0) == 0x00) &&
((b & 0x07) != 0x04) && ((b & 0x07) != 0x05))) {
// REG=r, R/M=r or REG=r, R/M=[r]
nBytes += 2;
} else if ((b & 0xc0) == 0x40) {
if ((b & 0x07) == 0x04) {
// REG=r, R/M=[SIB + disp8]
nBytes += 4;
} else {
// REG=r, R/M=[r + disp8]
nBytes += 3;
}
} else {
// complex MOV, bail
return;
}
} else if (origBytes[nBytes] == 0xB8) {
// MOV 0xB8: http://ref.x86asm.net/coder32.html#xB8
nBytes += 5;
} else if (origBytes[nBytes] == 0x83) {
// ADD|ODR|ADC|SBB|AND|SUB|XOR|CMP r/m, imm8
unsigned char b = origBytes[nBytes + 1];
if ((b & 0xc0) == 0xc0) {
// ADD|ODR|ADC|SBB|AND|SUB|XOR|CMP r, imm8
nBytes += 3;
} else {
// bail
return;
}
} else if (origBytes[nBytes] == 0x68) {
// PUSH with 4-byte operand
nBytes += 5;
} else if ((origBytes[nBytes] & 0xf0) == 0x50) {
// 1-byte PUSH/POP
nBytes++;
} else if (origBytes[nBytes] == 0x6A) {
// PUSH imm8
nBytes += 2;
} else if (origBytes[nBytes] == 0xe9) {
pJmp32 = nBytes;
// jmp 32bit offset
nBytes += 5;
} else if (origBytes[nBytes] == 0xff && origBytes[nBytes + 1] == 0x25) {
// jmp [disp32]
nBytes += 6;
} else {
//printf ("Unknown x86 instruction byte 0x%02x, aborting trampoline\n", origBytes[nBytes]);
return;
}
}
#elif defined(_M_X64)
byteptr_t directJmpAddr;
while (nBytes < 13) {
// if found JMP 32bit offset, next bytes must be NOP or INT3
if (pJmp32 >= 0) {
if (origBytes[nBytes] == 0x90 || origBytes[nBytes] == 0xcc) {
nBytes++;
continue;
}
return;
}
if (origBytes[nBytes] == 0x0f) {
nBytes++;
if (origBytes[nBytes] == 0x1f) {
// nop (multibyte)
nBytes++;
if ((origBytes[nBytes] & 0xc0) == 0x40 &&
(origBytes[nBytes] & 0x7) == 0x04) {
nBytes += 3;
} else {
return;
}
} else if (origBytes[nBytes] == 0x05) {
// syscall
nBytes++;
} else {
return;
}
} else if (origBytes[nBytes] == 0x40 ||
origBytes[nBytes] == 0x41) {
// Plain REX or REX.B
nBytes++;
if ((origBytes[nBytes] & 0xf0) == 0x50) {
// push/pop with Rx register
nBytes++;
} else if (origBytes[nBytes] >= 0xb8 && origBytes[nBytes] <= 0xbf) {
// mov r32, imm32
nBytes += 5;
} else {
return;
}
} else if (origBytes[nBytes] == 0x45) {
// REX.R & REX.B
nBytes++;
if (origBytes[nBytes] == 0x33) {
// xor r32, r32
nBytes += 2;
} else {
return;
}
} else if ((origBytes[nBytes] & 0xfb) == 0x48) {
// REX.W | REX.WR
nBytes++;
if (origBytes[nBytes] == 0x81 &&
(origBytes[nBytes + 1] & 0xf8) == 0xe8) {
// sub r, dword
nBytes += 6;
} else if (origBytes[nBytes] == 0x83 &&
(origBytes[nBytes + 1] & 0xf8) == 0xe8) {
// sub r, byte
nBytes += 3;
} else if (origBytes[nBytes] == 0x83 &&
(origBytes[nBytes + 1] & 0xf8) == 0x60) {
// and [r+d], imm8
nBytes += 5;
} else if ((origBytes[nBytes] & 0xfd) == 0x89) {
// MOV r/m64, r64 | MOV r64, r/m64
if ((origBytes[nBytes + 1] & 0xc0) == 0x40) {
if ((origBytes[nBytes + 1] & 0x7) == 0x04) {
// R/M=[SIB+disp8], REG=r64
nBytes += 4;
} else {
// R/M=[r64+disp8], REG=r64
nBytes += 3;
}
} else if (((origBytes[nBytes + 1] & 0xc0) == 0xc0) ||
(((origBytes[nBytes + 1] & 0xc0) == 0x00) &&
((origBytes[nBytes + 1] & 0x07) != 0x04) &&
((origBytes[nBytes + 1] & 0x07) != 0x05))) {
// REG=r64, R/M=r64 or REG=r64, R/M=[r64]
nBytes += 2;
} else {
// complex MOV
return;
}
} else if (origBytes[nBytes] == 0xc7) {
// MOV r/m64, imm32
if (origBytes[nBytes + 1] == 0x44) {
// MOV [r64+disp8], imm32
// ModR/W + SIB + disp8 + imm32
nBytes += 8;
} else {
return;
}
} else if (origBytes[nBytes] == 0xff) {
pJmp32 = nBytes - 1;
// JMP /4
if ((origBytes[nBytes + 1] & 0xc0) == 0x0 &&
(origBytes[nBytes + 1] & 0x07) == 0x5) {
// [rip+disp32]
// convert JMP 32bit offset to JMP 64bit direct
directJmpAddr =
(byteptr_t)*((uint64_t*)(origBytes + nBytes + 6 +
(*((int32_t*)(origBytes + nBytes + 2)))));
nBytes += 6;
} else {
// not support yet!
return;
}
} else {
// not support yet!
return;
}
} else if ((origBytes[nBytes] & 0xf0) == 0x50) {
// 1-byte push/pop
nBytes++;
} else if (origBytes[nBytes] == 0x90) {
// nop
nBytes++;
} else if (origBytes[nBytes] == 0xb8) {
// MOV 0xB8: http://ref.x86asm.net/coder32.html#xB8
nBytes += 5;
} else if (origBytes[nBytes] == 0xc3) {
// ret
nBytes++;
} else if (origBytes[nBytes] == 0xe9) {
pJmp32 = nBytes;
// convert JMP 32bit offset to JMP 64bit direct
directJmpAddr = origBytes + pJmp32 + 5 + (*((int32_t*)(origBytes + pJmp32 + 1)));
// jmp 32bit offset
nBytes += 5;
} else if (origBytes[nBytes] == 0xff) {
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) = aOrigFunction;
tramp += sizeof(void*);
memcpy(tramp, aOrigFunction, 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 - 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) {
// 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.
*aOutTramp = tramp;
// ensure we can modify the original code
AutoVirtualProtect protect(aOrigFunction, nBytes, PAGE_EXECUTE_READWRITE);
if (!protect.Protect()) {
//printf ("VirtualProtectEx failed! %d\n", GetLastError());
return;
}
#if defined(_M_IX86)
// now modify the original bytes
origBytes[0] = 0xE9; // jmp
*((intptr_t*)(origBytes + 1)) =
aDest - (intptr_t)(origBytes + 5); // target displacement
#elif defined(_M_X64)
// mov r11, address
origBytes[0] = 0x49;
origBytes[1] = 0xbb;
*((intptr_t*)(origBytes + 2)) = aDest;
// jmp r11
origBytes[10] = 0x41;
origBytes[11] = 0xff;
origBytes[12] = 0xe3;
#endif
}
byteptr_t FindTrampolineSpace()
{
if (mCurHooks >= mMaxHooks) {
return 0;
}
byteptr_t p = mHookPage + mCurHooks * kHookSize;
mCurHooks++;
return p;
}
static void* ResolveRedirectedAddress(const byteptr_t aOriginalFunction)
{
#if defined(_M_IX86)
// If function entry is jmp [disp32] such as used by kernel32,
// we resolve redirected address from import table.
if (aOriginalFunction[0] == 0xff && aOriginalFunction[1] == 0x25) {
return (void*)(**((uint32_t**) (aOriginalFunction + 2)));
}
#elif defined(_M_X64)
if (aOriginalFunction[0] == 0xe9) {
// require for TestDllInterceptor with --disable-optimize
int32_t offset = *((int32_t*)(aOriginalFunction + 1));
return aOriginalFunction + 5 + offset;
}
#endif
return aOriginalFunction;
}
};
} // namespace internal
class WindowsDllInterceptor
{
internal::WindowsDllNopSpacePatcher mNopSpacePatcher;
internal::WindowsDllDetourPatcher mDetourPatcher;
const char* mModuleName;
int mNHooks;
public:
WindowsDllInterceptor()
: mModuleName(nullptr)
, mNHooks(0)
{}
void Init(const char* aModuleName, int aNumHooks = 0)
{
if (mModuleName) {
return;
}
mModuleName = aModuleName;
mNHooks = aNumHooks;
mNopSpacePatcher.Init(aModuleName);
// Lazily initialize mDetourPatcher, since it allocates memory and we might
// not need it.
}
void LockHooks()
{
if (mDetourPatcher.Initialized()) {
mDetourPatcher.LockHooks();
}
}
bool AddHook(const char* aName, intptr_t aHookDest, void** aOrigFunc)
{
// Use a nop space patch if possible, otherwise fall back to a detour.
// This should be the preferred method for adding hooks.
if (!mModuleName) {
return false;
}
if (mNopSpacePatcher.AddHook(aName, aHookDest, aOrigFunc)) {
return true;
}
return AddDetour(aName, aHookDest, aOrigFunc);
}
bool AddDetour(const char* aName, intptr_t aHookDest, void** aOrigFunc)
{
// Generally, code should not call this method directly. Use AddHook unless
// there is a specific need to avoid nop space patches.
if (!mModuleName) {
return false;
}
if (!mDetourPatcher.Initialized()) {
mDetourPatcher.Init(mModuleName, mNHooks);
}
return mDetourPatcher.AddHook(aName, aHookDest, aOrigFunc);
}
};
} // namespace mozilla
#endif /* NS_WINDOWS_DLL_INTERCEPTOR_H_ */
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