Stop specifying /BASE option to mozc_tip32.dll and mozc_tip64.dll

[yukawa]

Description

Currently mozc_tip32.dll and mozc_tip64.dll are built with /BASE option.

mozc/src/win32/tip/tip.gyp

Lines 155 to 157 in af20906

	'VCLinkerTool': {
	'BaseAddress': '0x06000000',
	},

mozc/src/win32/tip/tip.gyp

Lines 174 to 176 in af20906

	'VCLinkerTool': {
	'BaseAddress': '0x06000000',
	},

This is however now discouraged as follows.

Note

For security reasons, Microsoft recommends you use the /DYNAMICBASE option instead of specifying base addresses for your executables. /DYNAMICBASE generates an executable image that can be randomly rebased at load time by using the address space layout randomization (ASLR) feature of Windows. The /DYNAMICBASE option is on by default.

You can also find the following warning while building Mozc for Windows (e.g. from build #186)

[456/457] LINK_EMBED(DLL) mozc_tip64.dll
LINK : warning LNK4281: undesirable base address 0x6000000 for x64 image; set base address above 4GB for best ASLR optimization

Also from Does ASLR relocate all DLLs by the same offset? - The Old New Thing

ASLR chooses the base address pseudo-randomly, though it does take some of the original base addresses into account. For example, if the original base address was below the 4GB boundary, then the new pseudo-random base address will also be below the 4GB boundary.

Steps to reproduce

1. Build and install Mozc for Windows
2. dumpbin /HEADERS .\out_win\Release\mozc_tip32.dll
3. dumpbin /HEADERS .\out_win\Release_x64\mozc_tip64.dll
4. Launch Notepad (64-bit)
5. Select Mozc as the current IME

Expected behavior

• At the step 5, mozc_tip64.dll is loaded into somewhere above 0x100000000

Expected result in the step 2

OPTIONAL HEADER VALUES
             10B magic # (PE32)

  (snip)

         6000000 image base (06000000 to 064D0FFF)

  (snip)

               2 subsystem (Windows GUI)
             140 DLL characteristics
                   Dynamic base
                   NX compatible

Expected result in the step 3

OPTIONAL HEADER VALUES
             20B magic # (PE32+)

  (snip)

         6000000 image base (0000000006000000 to 000000000650CFFF)

  (snip)

               2 subsystem (Windows GUI)
             160 DLL characteristics
                   High Entropy Virtual Addresses
                   Dynamic base
                   NX compatible

Actual behavior

• At the step 5, mozc_tip64.dll is loaded into somewhere below 0x100000000 (not as expected).

Actual result in the step 2

OPTIONAL HEADER VALUES
             10B magic # (PE32)

  (snip)

        10000000 image base (10000000 to 104D0FFF)
            1000 section alignment

  (snip)

               2 subsystem (Windows GUI)
             140 DLL characteristics
                   Dynamic base
                   NX compatible

Actual result in the step 3

OPTIONAL HEADER VALUES
             20B magic # (PE32+)

  (snip)

       180000000 image base (0000000180000000 to 000000018050CFFF)

  (snip)

               2 subsystem (Windows GUI)
             160 DLL characteristics
                   High Entropy Virtual Addresses
                   Dynamic base
                   NX compatible

Screenshots

Version or commit-id

82ff093

Environment

• OS: Windows 11 22H2