nsWindowsDllInterceptor.h
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
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*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is the Mozilla Foundation.
* Portions created by the Initial Developer are Copyright (C) 2009
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Vladimir Vukicevic <vladimir@pobox.com>
*
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* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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#ifndef NS_WINDOWS_DLL_INTERCEPTOR_H_
#define NS_WINDOWS_DLL_INTERCEPTOR_H_
#include <windows.h>
#include <winternl.h>
/*
* Simple trampoline interception
*
* 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 WindowsDllInterceptor class 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.
*/
class WindowsDllInterceptor
{
typedef unsigned char *byteptr_t;
public:
WindowsDllInterceptor()
: mModule(0)
{
}
WindowsDllInterceptor(const char *modulename, int nhooks = 0) {
Init(modulename, nhooks);
}
~WindowsDllInterceptor() {
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
DWORD op;
if (!VirtualProtectEx(GetCurrentProcess(), origBytes, nBytes, PAGE_EXECUTE_READWRITE, &op)) {
//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
// restore protection; if this fails we can't really do anything about it
VirtualProtectEx(GetCurrentProcess(), origBytes, nBytes, op, &op);
}
}
void Init(const char *modulename, int nhooks = 0) {
if (mModule)
return;
mModule = LoadLibraryExA(modulename, NULL, 0);
if (!mModule) {
//printf("LoadLibraryEx for '%s' failed\n", modulename);
return;
}
int hooksPerPage = 4096 / kHookSize;
if (nhooks == 0)
nhooks = hooksPerPage;
mMaxHooks = nhooks + (hooksPerPage % nhooks);
mCurHooks = 0;
mHookPage = (byteptr_t) VirtualAllocEx(GetCurrentProcess(), NULL, mMaxHooks * kHookSize,
MEM_COMMIT | MEM_RESERVE,
PAGE_EXECUTE_READWRITE);
if (!mHookPage) {
mModule = 0;
return;
}
}
void LockHooks() {
if (!mModule)
return;
DWORD op;
VirtualProtectEx(GetCurrentProcess(), mHookPage, mMaxHooks * kHookSize, PAGE_EXECUTE_READ, &op);
mModule = 0;
}
bool AddHook(const char *pname,
intptr_t hookDest,
void **origFunc)
{
if (!mModule)
return false;
void *pAddr = (void *) GetProcAddress(mModule, pname);
if (!pAddr) {
//printf ("GetProcAddress failed\n");
return false;
}
void *tramp = CreateTrampoline(pAddr, hookDest);
if (!tramp) {
//printf ("CreateTrampoline failed\n");
return false;
}
*origFunc = tramp;
return true;
}
protected:
const static int kPageSize = 4096;
const static int kHookSize = 128;
HMODULE mModule;
byteptr_t mHookPage;
int mMaxHooks;
int mCurHooks;
byteptr_t CreateTrampoline(void *origFunction,
intptr_t dest)
{
byteptr_t tramp = FindTrampolineSpace();
if (!tramp)
return 0;
byteptr_t origBytes = (byteptr_t) origFunction;
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) && ((b & 0x38) != 0x20)) {
// REG=r, R/M=[r + disp8]
nBytes += 3;
} else {
// complex MOV, bail
return 0;
}
} 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 0;
}
} 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 {
//printf ("Unknown x86 instruction byte 0x%02x, aborting trampoline\n", origBytes[nBytes]);
return 0;
}
}
#elif defined(_M_X64)
while (nBytes < 13) {
// if found JMP 32bit offset, next bytes must be NOP
if (pJmp32 >= 0) {
if (origBytes[nBytes++] != 0x90)
return 0;
continue;
}
if (origBytes[nBytes] == 0x41) {
// 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 0;
}
} else if (origBytes[nBytes] == 0x45) {
// REX.R & REX.B
nBytes++;
if (origBytes[nBytes] == 0x33) {
// xor r32, r32
nBytes += 2;
} else {
return 0;
}
} 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 0;
}
} else {
// not support yet!
return 0;
}
} else if ((origBytes[nBytes] & 0xf0) == 0x50) {
// 1-byte push/pop
nBytes++;
} else if (origBytes[nBytes] == 0x90) {
// nop
nBytes++;
} else if (origBytes[nBytes] == 0xe9) {
pJmp32 = nBytes;
// jmp 32bit offset
nBytes += 5;
} else if (origBytes[nBytes] == 0xff) {
nBytes++;
if ((origBytes[nBytes] & 0xf8) == 0xf0) {
// push r64
nBytes++;
} else {
return 0;
}
} else {
return 0;
}
}
#else
#error "Unknown processor type"
#endif
if (nBytes > 100) {
//printf ("Too big!");
return 0;
}
// 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
// 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 0;
}
#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);
return tramp;
}
byteptr_t FindTrampolineSpace() {
if (mCurHooks >= mMaxHooks)
return 0;
byteptr_t p = mHookPage + mCurHooks*kHookSize;
mCurHooks++;
return p;
}
};
#endif /* NS_WINDOWS_DLL_INTERCEPTOR_H_ */
