RandomizingLibs.md

Compiling shared libraries with vtable-rando

If a target application for vtable-rando is calling virtual methods in shared libraries, the shared libraries should also be compiled by vtable-rando. Especially, C++ standard library contains a lot of virtual methods and using it is almost inevitable in C++ programming. The following explains how to compile the C++ standard libraries with vtable-rando. We can use either libc++ or libstdc++ but libc++ is recommended because libstdc++ is only known to work in the specific environment.

Option 1: libc++ (recommended)

Get libcxxabi and libcxx source:

git clone -b release_38 http://llvm.org/git/libcxxabi.git
git clone -b release_38 http://llvm.org/git/libcxx.git

Build libcxxabi (libcxx is dependent on libcxxabi):

NOTE: This example is assuming that you are installing libcxx to the same path where libcxxabi has been installed for simplicity.

cd libcxxabi
mkdir build
cd build
cmake .. \
-DLIBCXXABI_LIBCXX_PATH=path-to-libcxx-source \
-DCMAKE_C_COMPILER=multicompiler-path/clang \
-DCMAKE_BUILD_TYPE=Release \
-DCMAKE_CXX_COMPILER=multicompiler-path/clang++ \
-DLLVM_PATH=path-to-multicompiler-source \
-DCMAKE_C_FLAGS="-fvtable-rando" \
-DCMAKE_CXX_FLAGS="-fvtable-rando" \
-DCMAKE_EXE_LINKER_FLAGS="-fvtable-rando -Wl,--plugin-opt,-random-seed=1" \
-DLIBCXXABI_LIBCXX_INCLUDES=path-to-libcxx-source/include \
-DCMAKE_INSTALL_PREFIX=path-to-install-libcxx
make && make install

Build libcxx:

cmake .. \
-DCMAKE_C_COMPILER=multicompiler-path/clang \
-DCMAKE_CXX_COMPILER=multicompiler-path/clang++ \
-DCMAKE_INSTALL_PREFIX=path-to-install-libcxx \
-DCMAKE_BUILD_TYPE=Release -DLIBCXX_CXX_ABI=libcxxabi \
-DLIBCXX_CXX_ABI_INCLUDE_PATHS=path-to-install-libcxx/include \
-DLLVM_PATH=path-to-multicompiler-source \
-DLIBCXX_CXX_ABI_LIBRARY_PATH=path-to-install-libcxx/lib \
-DCMAKE_C_FLAGS="-fvtable-rando" \
-DCMAKE_CXX_FLAGS="-fvtable-rando" \
-DCMAKE_EXE_LINKER_FLAGS="-fvtable-rando -Wl,--plugin-opt,-random-seed=1"

NOTE: Do not locate the custom libc++ in the same path to multicompiler unless you've built multicompiler with vtable-rando.

For more information, see: http://libcxx.llvm.org/docs/BuildingLibcxx.html

Linking against the randomized libcxx:

After you compiled libc++ with multicompiler and vtable-rando option, you should link your target application against the custom-built libc++.

In order to do that, you should pass the following flags to compiler and linker respectively.

For compiler: -nostdinc++ -I{path-to-install-libcxx}/include/c++/v1 -L{path-to-install-libcxx}/lib

For linker: -stdlib=libc++ -Wl,-rpath,path-to-install-libcxx/lib

For more information, see: http://libcxx.llvm.org/docs/UsingLibcxx.html

Option 2: libstdc++

NOTE: This is only known to work with gcc-4.8 on Ubuntu-14.04.

Get gcc-4.8 source:

git clone -b gcc-4_8_4-release git://gcc.gnu.org/git/gcc.git gcc-4_8_4
cd gcc-4_8_4
git checkout -b gcc-4_8_4-release

Build and install libstdc++:

cd libstdc++-v3
mkdir build && cd build
../configure CC=multicompiler-path/clang CXX=multicompiler-path/clang++ CXXFLAGS='-frandom-seed=1 -fvtable-rando' LDFLAGS='-fvtable-rando' --prefix=path-to-install-custom-libstdc++ --disable-multilib --disable-nls 
make && make install

NOTE: Do not install the custom libstdc++ alongside the multicompiler unless you've built multicompiler with vtable-rando.

NOTE: when configuring libstdc++, make sure that the gthread headers (gthr.h, gthr-default.h, etc.) are found. On a stock Ubuntu 14.04 you might have to add -I/usr/include/x86_64-linux-gnu/c++/4.8/bits to CXXFLAGS. Failure to do so will prevent multi-threaded C++ applications from building.

Linking against the randomized libstdc++:

After you compiled libstdc++ with multicompiler and vtable-rando option, you should link your target application against the custom-built libstdc++. In order to do that you should add the following flags:

To the compiler: -I{path-to-install-custom-libstdc++}/include/c++/4.8.4/ -L{path-to-install-custom-libstdc++}/lib

To the linker: -Wl,-rpath,path-to-install-custom-libstdc++/lib