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Don't depend on vtable ABI layout

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topjohnwu 2021-08-12 06:41:59 -07:00
parent 0d977b54f7
commit c2c3bf0ba4
1 changed files with 34 additions and 27 deletions
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61
native/jni/inject/hook.cpp
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@ -118,7 +118,7 @@ string get_class_name(JNIEnv *env, jclass clazz) {
ret (*old_##func)(__VA_ARGS__); \
ret new_##func(__VA_ARGS__)
jint new_env_RegisterNatives(
jint jniRegisterNatives(
JNIEnv *env, jclass clazz, const JNINativeMethod *methods, jint numMethods) {
auto className = get_class_name(env, clazz);
LOGD("hook: JNIEnv->RegisterNatives %s\n", className.data());
@ -150,34 +150,33 @@ DCL_HOOK_FUNC(int, selinux_android_setcontext,
// -----------------------------------------------------------------
// android::AndroidRuntime vtable layout
struct vtable_t {
void *rtti;
void *dtor;
void (*onVmCreated)(void *self, JNIEnv* env);
void (*onStarted)(void *self);
void (*onZygoteInit)(void *self);
void (*onExit)(void *self, int code);
};
vtable_t *gAppRuntimeVTable;
// The original android::AppRuntime virtual table
void **gAppRuntimeVTable;
// This method is a trampoline for hooking JNIEnv->RegisterNatives
DCL_HOOK_FUNC(void, onVmCreated, void *self, JNIEnv *env) {
void onVmCreated(void *self, JNIEnv* env) {
LOGD("hook: AppRuntime::onVmCreated\n");
// Restore the virtual table, we no longer need it
auto *new_table = *reinterpret_cast<vtable_t**>(self);
*reinterpret_cast<vtable_t**>(self) = gAppRuntimeVTable;
delete new_table;
// Restore virtual table
auto new_table = *reinterpret_cast<void***>(self);
*reinterpret_cast<void***>(self) = gAppRuntimeVTable;
delete[] new_table;
new_functions = new JNINativeInterface();
memcpy(new_functions, env->functions, sizeof(*new_functions));
new_functions->RegisterNatives = &jniRegisterNatives;
// Replace the function table in JNIEnv to hook RegisterNatives
old_functions = env->functions;
new_functions = new JNINativeInterface();
memcpy(new_functions, env->functions, sizeof(*new_functions));
new_functions->RegisterNatives = new_env_RegisterNatives;
env->functions = new_functions;
old_onVmCreated(self, env);
}
template<int N>
void vtable_entry(void *self, JNIEnv* env) {
// The first invocation will be onVmCreated
onVmCreated(self, env);
// Call original function
reinterpret_cast<decltype(&onVmCreated)>(gAppRuntimeVTable[N])(self, env);
}
// This method is a trampoline for swizzling android::AppRuntime vtable
@ -190,13 +189,21 @@ DCL_HOOK_FUNC(void, setArgv0, void *self, const char *argv0, bool setProcName) {
LOGD("hook: AndroidRuntime::setArgv0\n");
// We don't know which entry is onVmCreated, so overwrite every one
// We also don't know the size of the vtable, but 8 is more than enough
auto new_table = new void*[8];
new_table[0] = reinterpret_cast<void*>(&vtable_entry<0>);
new_table[1] = reinterpret_cast<void*>(&vtable_entry<1>);
new_table[2] = reinterpret_cast<void*>(&vtable_entry<2>);
new_table[3] = reinterpret_cast<void*>(&vtable_entry<3>);
new_table[4] = reinterpret_cast<void*>(&vtable_entry<4>);
new_table[5] = reinterpret_cast<void*>(&vtable_entry<5>);
new_table[6] = reinterpret_cast<void*>(&vtable_entry<6>);
new_table[7] = reinterpret_cast<void*>(&vtable_entry<7>);
// Swizzle C++ vtable to hook virtual function
gAppRuntimeVTable = *reinterpret_cast<vtable_t**>(self);
old_onVmCreated = gAppRuntimeVTable->onVmCreated;
auto *new_table = new vtable_t();
memcpy(new_table, gAppRuntimeVTable, sizeof(vtable_t));
new_table->onVmCreated = &new_onVmCreated;
*reinterpret_cast<vtable_t**>(self) = new_table;
gAppRuntimeVTable = *reinterpret_cast<void***>(self);
*reinterpret_cast<void***>(self) = new_table;
swizzled = true;
old_setArgv0(self, argv0, setProcName);