0x01 Brief About ElfHook
这份ElfHook的代码参考boyliang的AllHookInOne, 修复AllHookInOne的 ElfHook中的一些问题，同时也解决我们项目中遇到的一些问题。
-
NOT DT_HAST in .dynmaic section，but .gun.hash instead.
-
NOT DT_REL and DT_RELSZ in .dynmaic section, but DT_ANDROID_REL and DT_ANDROID_RELSZ instead.
-
计算动态库加载的base_addr是错误的，应该使用bias_addr来计算出ehdr、phdr和shdr之外的所有地址。
-
替换函数时，修改page的读写权限时，在SEAndroid上PROT_EXEC和PROT_WRITE同时设置可能会导致异常，
-
after hook "dlopen" function, how to get base_addr from return value of old dlopen in new dlopen function.
-
support aarch64 (arm64-v8a)
ref:
AllHookInOne : [https://github.com/boyliang/AllHookInOne.git]
AllHookInOne说明 : [http://bbs.pediy.com/showthread.php?p=1328038]
bionic : [https://android.googlesource.com/platform/bionic]
0x02 How To Build
Export android ndk path
export -p PATH=$PATH:$ANDROID_NDK
Build
make
make clean
make install # copy libElfHook.so to jniLibs dir in Demo.
or
ndk-build NDK_PROJECT_PATH=. NDK_OUT=./objs NDK_LIBS_OUT=./bin APP_BUILD_SCRIPT=./Android.mk APP_PLATFORM=android-23 APP_ABI=arm64-v8a,armeabi-v7a APP_STL=stlport_static
0x03 How To Use
elf_module is a shared library or executable, elf_hooker is wrapper of hook function.
- bool elf_hooker::phrase_proc_maps()
phrase /proc/self/maps to create all elf modules have been loadded
- void elf_hooker::dump_module_list()
print all elf moudle's info, base addr and full path.
- void elf_hooker::set_prehook_cb( prehook_cb ):
set a callback function, which would be invoked before hooked. if it return false, prehook_cb function like this:
bool prehook_cb(const char* module_name, const char* func_name);
module_name: the full filename of shared library or executable.
func_name: function name would be hooked.
- void elf_hooker::hook_all_modules(const char *func_name, void *pfn_new, void** ppfn_old)
hook a function of all the modules, MUST call phrase_proc_maps() before hook_all_modules()
func_name: the name of function that will be hooked.
pfn_new: new function pointer
ppfn_old: return raw function pointer, ppfn_old MUST NOT be NULL
- bool elf_hooker::hook(elf_module *module, const char* func_name, void *pfn_new, void **ppfn_old)
hook a function of a single module.
module: pointer of elf_module.
other parameters is the same as hook_all_modules()