| // Copyright 2017 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "base/win/com_init_check_hook.h" |
| |
| #include <windows.h> |
| #include <objbase.h> |
| #include <stdint.h> |
| #include <string.h> |
| |
| #include "base/strings/stringprintf.h" |
| #include "base/synchronization/lock.h" |
| #include "base/win/com_init_util.h" |
| #include "base/win/patch_util.h" |
| |
| namespace base { |
| namespace win { |
| |
| #if defined(COM_INIT_CHECK_HOOK_ENABLED) |
| |
| namespace { |
| |
| // Hotpatchable Microsoft x86 32-bit functions take one of two forms: |
| // Newer format: |
| // RelAddr Binary Instruction Remarks |
| // -5 cc int 3 |
| // -4 cc int 3 |
| // -3 cc int 3 |
| // -2 cc int 3 |
| // -1 cc int 3 |
| // 0 8bff mov edi,edi Actual entry point and no-op. |
| // 2 ... Actual body. |
| // |
| // Older format: |
| // RelAddr Binary Instruction Remarks |
| // -5 90 nop |
| // -4 90 nop |
| // -3 90 nop |
| // -2 90 nop |
| // -1 90 nop |
| // 0 8bff mov edi,edi Actual entry point and no-op. |
| // 2 ... Actual body. |
| // |
| // The "int 3" or nop sled as well as entry point no-op are critical, as they |
| // are just enough to patch in a short backwards jump to -5 (2 bytes) then that |
| // can do a relative 32-bit jump about 2GB before or after the current address. |
| // |
| // To perform a hotpatch, we need to figure out where we want to go and where |
| // we are now as the final jump is relative. Let's say we want to jump to |
| // 0x12345678. Relative jumps are calculated from eip, which for our jump is the |
| // next instruction address. For the example above, that means we start at a 0 |
| // base address. |
| // |
| // Our patch will then look as follows: |
| // RelAddr Binary Instruction Remarks |
| // -5 e978563412 jmp 0x12345678-(-0x5+0x5) Note little-endian format. |
| // 0 ebf9 jmp -0x5-(0x0+0x2) Goes to RelAddr -0x5. |
| // 2 ... Actual body. |
| // Note: The jmp instructions above are structured as |
| // Address(Destination)-(Address(jmp Instruction)+sizeof(jmp Instruction)) |
| |
| // The struct below is provided for convenience and must be packed together byte |
| // by byte with no word alignment padding. This comes at a very small |
| // performance cost because now there are shifts handling the fields, but |
| // it improves readability. |
| #pragma pack(push, 1) |
| struct StructuredHotpatch { |
| unsigned char jmp_32_relative = 0xe9; // jmp relative 32-bit. |
| int32_t relative_address = 0; // 32-bit signed operand. |
| unsigned char jmp_8_relative = 0xeb; // jmp relative 8-bit. |
| unsigned char back_address = 0xf9; // Operand of -7. |
| }; |
| #pragma pack(pop) |
| |
| static_assert(sizeof(StructuredHotpatch) == 7, |
| "Needs to be exactly 7 bytes for the hotpatch to work."); |
| |
| // nop Function Padding with "mov edi,edi" |
| const unsigned char g_hotpatch_placeholder_nop[] = {0x90, 0x90, 0x90, 0x90, |
| 0x90, 0x8b, 0xff}; |
| |
| // int 3 Function Padding with "mov edi,edi" |
| const unsigned char g_hotpatch_placeholder_int3[] = {0xcc, 0xcc, 0xcc, 0xcc, |
| 0xcc, 0x8b, 0xff}; |
| |
| class HookManager { |
| public: |
| static HookManager* GetInstance() { |
| static auto* hook_manager = new HookManager(); |
| return hook_manager; |
| } |
| |
| void RegisterHook() { |
| AutoLock auto_lock(lock_); |
| if (init_count_ == 0) |
| WriteHook(); |
| |
| ++init_count_; |
| } |
| |
| void UnregisterHook() { |
| AutoLock auto_lock(lock_); |
| DCHECK_NE(0U, init_count_); |
| if (init_count_ == 1) |
| RevertHook(); |
| |
| --init_count_; |
| } |
| |
| private: |
| enum class HotpatchPlaceholderFormat { |
| // The hotpatch placeholder is currently unknown |
| UNKNOWN, |
| // The hotpatch placeholder used int 3's in the sled. |
| INT3, |
| // The hotpatch placeholder used nop's in the sled. |
| NOP, |
| // This function has already been patched by a different component. |
| EXTERNALLY_PATCHED, |
| }; |
| |
| HookManager() = default; |
| ~HookManager() = default; |
| |
| void WriteHook() { |
| lock_.AssertAcquired(); |
| DCHECK(!ole32_library_); |
| ole32_library_ = ::LoadLibrary(L"ole32.dll"); |
| |
| if (!ole32_library_) |
| return; |
| |
| // See banner comment above why this subtracts 5 bytes. |
| co_create_instance_padded_address_ = |
| reinterpret_cast<uint32_t>( |
| GetProcAddress(ole32_library_, "CoCreateInstance")) - 5; |
| |
| // See banner comment above why this adds 7 bytes. |
| original_co_create_instance_body_function_ = |
| reinterpret_cast<decltype(original_co_create_instance_body_function_)>( |
| co_create_instance_padded_address_ + 7); |
| |
| uint32_t dchecked_co_create_instance_address = |
| reinterpret_cast<uint32_t>(&HookManager::DCheckedCoCreateInstance); |
| uint32_t jmp_offset_base_address = co_create_instance_padded_address_ + 5; |
| structured_hotpatch_.relative_address = |
| dchecked_co_create_instance_address - jmp_offset_base_address; |
| |
| HotpatchPlaceholderFormat format = GetHotpatchPlaceholderFormat( |
| reinterpret_cast<const void*>(co_create_instance_padded_address_)); |
| if (format == HotpatchPlaceholderFormat::UNKNOWN) { |
| NOTREACHED() << "Unrecognized hotpatch function format: " |
| << FirstSevenBytesToString( |
| co_create_instance_padded_address_); |
| return; |
| } else if (format == HotpatchPlaceholderFormat::EXTERNALLY_PATCHED) { |
| hotpatch_placeholder_format_ = format; |
| NOTREACHED() << "CoCreateInstance appears to be previously patched. <" |
| << FirstSevenBytesToString( |
| co_create_instance_padded_address_) |
| << "> Attempted to write <" |
| << FirstSevenBytesToString( |
| reinterpret_cast<uint32_t>(&structured_hotpatch_)) |
| << ">"; |
| return; |
| } |
| |
| DCHECK_EQ(hotpatch_placeholder_format_, HotpatchPlaceholderFormat::UNKNOWN); |
| DWORD patch_result = internal::ModifyCode( |
| reinterpret_cast<void*>(co_create_instance_padded_address_), |
| reinterpret_cast<void*>(&structured_hotpatch_), |
| sizeof(structured_hotpatch_)); |
| if (patch_result == NO_ERROR) |
| hotpatch_placeholder_format_ = format; |
| } |
| |
| void RevertHook() { |
| lock_.AssertAcquired(); |
| |
| DWORD revert_result = NO_ERROR; |
| switch (hotpatch_placeholder_format_) { |
| case HotpatchPlaceholderFormat::INT3: |
| if (WasHotpatchChanged()) |
| return; |
| revert_result = internal::ModifyCode( |
| reinterpret_cast<void*>(co_create_instance_padded_address_), |
| reinterpret_cast<const void*>(&g_hotpatch_placeholder_int3), |
| sizeof(g_hotpatch_placeholder_int3)); |
| break; |
| case HotpatchPlaceholderFormat::NOP: |
| if (WasHotpatchChanged()) |
| return; |
| revert_result = internal::ModifyCode( |
| reinterpret_cast<void*>(co_create_instance_padded_address_), |
| reinterpret_cast<const void*>(&g_hotpatch_placeholder_nop), |
| sizeof(g_hotpatch_placeholder_nop)); |
| break; |
| case HotpatchPlaceholderFormat::EXTERNALLY_PATCHED: |
| case HotpatchPlaceholderFormat::UNKNOWN: |
| break; |
| } |
| DCHECK_EQ(revert_result, static_cast<DWORD>(NO_ERROR)) |
| << "Failed to revert CoCreateInstance hot-patch"; |
| |
| hotpatch_placeholder_format_ = HotpatchPlaceholderFormat::UNKNOWN; |
| |
| if (ole32_library_) { |
| ::FreeLibrary(ole32_library_); |
| ole32_library_ = nullptr; |
| } |
| |
| co_create_instance_padded_address_ = 0; |
| original_co_create_instance_body_function_ = nullptr; |
| } |
| |
| HotpatchPlaceholderFormat GetHotpatchPlaceholderFormat(const void* address) { |
| if (::memcmp(reinterpret_cast<void*>(co_create_instance_padded_address_), |
| reinterpret_cast<const void*>(&g_hotpatch_placeholder_int3), |
| sizeof(g_hotpatch_placeholder_int3)) == 0) { |
| return HotpatchPlaceholderFormat::INT3; |
| } |
| |
| if (::memcmp(reinterpret_cast<void*>(co_create_instance_padded_address_), |
| reinterpret_cast<const void*>(&g_hotpatch_placeholder_nop), |
| sizeof(g_hotpatch_placeholder_nop)) == 0) { |
| return HotpatchPlaceholderFormat::NOP; |
| } |
| |
| const unsigned char* instruction_bytes = |
| reinterpret_cast<const unsigned char*>( |
| co_create_instance_padded_address_); |
| const unsigned char entry_point_byte = instruction_bytes[5]; |
| // Check for all of the common jmp opcodes. |
| if (entry_point_byte == 0xeb || entry_point_byte == 0xe9 || |
| entry_point_byte == 0xff || entry_point_byte == 0xea) { |
| return HotpatchPlaceholderFormat::EXTERNALLY_PATCHED; |
| } |
| |
| return HotpatchPlaceholderFormat::UNKNOWN; |
| } |
| |
| bool WasHotpatchChanged() { |
| if (::memcmp(reinterpret_cast<void*>(co_create_instance_padded_address_), |
| reinterpret_cast<const void*>(&structured_hotpatch_), |
| sizeof(structured_hotpatch_)) == 0) { |
| return false; |
| } |
| |
| NOTREACHED() << "CoCreateInstance patch overwritten. Expected: <" |
| << FirstSevenBytesToString(co_create_instance_padded_address_) |
| << ">, Actual: <" |
| << FirstSevenBytesToString( |
| reinterpret_cast<uint32_t>(&structured_hotpatch_)) |
| << ">"; |
| return true; |
| } |
| |
| static HRESULT __stdcall DCheckedCoCreateInstance(const CLSID& rclsid, |
| IUnknown* pUnkOuter, |
| DWORD dwClsContext, |
| REFIID riid, |
| void** ppv) { |
| // Chromium COM callers need to make sure that their thread is configured to |
| // process COM objects to avoid creating an implicit MTA or silently failing |
| // STA object creation call due to the SUCCEEDED() pattern for COM calls. |
| // |
| // If you hit this assert as part of migrating to the Task Scheduler, |
| // evaluate your threading guarantees and dispatch your work with |
| // base::CreateCOMSTATaskRunnerWithTraits(). |
| // |
| // If you need MTA support, ping //base/task/task_scheduler/OWNERS. |
| AssertComInitialized( |
| "CoCreateInstance calls in Chromium require explicit COM " |
| "initialization via base::CreateCOMSTATaskRunnerWithTraits() or " |
| "ScopedCOMInitializer. See the comment in DCheckedCoCreateInstance for " |
| "more details."); |
| return original_co_create_instance_body_function_(rclsid, pUnkOuter, |
| dwClsContext, riid, ppv); |
| } |
| |
| // Returns the first 7 bytes in hex as a string at |address|. |
| static std::string FirstSevenBytesToString(uint32_t address) { |
| const unsigned char* bytes = |
| reinterpret_cast<const unsigned char*>(address); |
| return base::StringPrintf("%02x %02x %02x %02x %02x %02x %02x", bytes[0], |
| bytes[1], bytes[2], bytes[3], bytes[4], bytes[5], |
| bytes[6]); |
| } |
| |
| // Synchronizes everything in this class. |
| base::Lock lock_; |
| size_t init_count_ = 0; |
| HMODULE ole32_library_ = nullptr; |
| uint32_t co_create_instance_padded_address_ = 0; |
| HotpatchPlaceholderFormat hotpatch_placeholder_format_ = |
| HotpatchPlaceholderFormat::UNKNOWN; |
| StructuredHotpatch structured_hotpatch_; |
| static decltype( |
| ::CoCreateInstance)* original_co_create_instance_body_function_; |
| |
| DISALLOW_COPY_AND_ASSIGN(HookManager); |
| }; |
| |
| decltype(::CoCreateInstance)* |
| HookManager::original_co_create_instance_body_function_ = nullptr; |
| |
| } // namespace |
| |
| #endif // defined(COM_INIT_CHECK_HOOK_ENABLED) |
| |
| ComInitCheckHook::ComInitCheckHook() { |
| #if defined(COM_INIT_CHECK_HOOK_ENABLED) |
| HookManager::GetInstance()->RegisterHook(); |
| #endif // defined(COM_INIT_CHECK_HOOK_ENABLED) |
| } |
| |
| ComInitCheckHook::~ComInitCheckHook() { |
| #if defined(COM_INIT_CHECK_HOOK_ENABLED) |
| HookManager::GetInstance()->UnregisterHook(); |
| #endif // defined(COM_INIT_CHECK_HOOK_ENABLED) |
| } |
| |
| } // namespace win |
| } // namespace base |
