Magisk/native/jni/zygisk/hook.cpp
topjohnwu 003fea52b1 Remove all non-Magisk hiding code
Magisk no longer interferes with any signals/info that were not created
or caused by Magisk itself.
2021-08-18 02:01:54 -07:00

401 lines
13 KiB
C++

#include <dlfcn.h>
#include <xhook.h>
#include <utils.hpp>
#include <flags.hpp>
#include <daemon.hpp>
#include "inject.hpp"
#include "memory.hpp"
#include "api.hpp"
using namespace std;
using jni_hook::hash_map;
using jni_hook::tree_map;
using xstring = jni_hook::string;
namespace {
struct HookContext {
int pid;
bool do_hide;
union {
SpecializeAppProcessArgs *args;
ForkSystemServerArgs *server_args;
void *raw_args;
};
};
// Global variables
vector<tuple<const char *, const char *, void **>> *xhook_list;
vector<JNINativeMethod> *jni_hook_list;
hash_map<xstring, tree_map<xstring, tree_map<xstring, void *>>> *jni_method_map;
HookContext *current_ctx;
JavaVM *g_jvm;
const JNINativeInterface *old_functions;
JNINativeInterface *new_functions;
#define DCL_JNI_FUNC(name) \
void *name##_orig; \
void name##_pre(HookContext *ctx, JNIEnv *env, jclass clazz); \
void name##_post(HookContext *ctx, JNIEnv *env, jclass clazz);
// JNI method declarations
DCL_JNI_FUNC(nativeForkAndSpecialize)
DCL_JNI_FUNC(nativeSpecializeAppProcess)
DCL_JNI_FUNC(nativeForkSystemServer)
#undef DCL_JNI_FUNC
// JNI method definitions
// Includes all method signatures of all supported Android versions
#include "jni_hooks.hpp"
#define HOOK_JNI(method) \
if (methods[i].name == #method##sv) { \
jni_hook_list->push_back(methods[i]); \
method##_orig = methods[i].fnPtr; \
for (int j = 0; j < method##_methods_num; ++j) { \
if (strcmp(methods[i].signature, method##_methods[j].signature) == 0) { \
newMethods[i] = method##_methods[j]; \
LOGI("hook: replaced #" #method "\n"); \
++hooked; \
break; \
} \
} \
continue; \
}
unique_ptr<JNINativeMethod[]> hookAndSaveJNIMethods(
JNIEnv *env, const char *className, const JNINativeMethod *methods, int numMethods) {
if (g_jvm == nullptr) {
// Save for later unhooking
env->GetJavaVM(&g_jvm);
}
unique_ptr<JNINativeMethod[]> newMethods;
int hooked = numeric_limits<int>::max();
if (className == "com/android/internal/os/Zygote"sv) {
hooked = 0;
newMethods = make_unique<JNINativeMethod[]>(numMethods);
memcpy(newMethods.get(), methods, sizeof(JNINativeMethod) * numMethods);
}
auto &class_map = (*jni_method_map)[className];
for (int i = 0; i < numMethods; ++i) {
class_map[methods[i].name][methods[i].signature] = methods[i].fnPtr;
if (hooked < 3) {
HOOK_JNI(nativeForkAndSpecialize);
HOOK_JNI(nativeSpecializeAppProcess);
HOOK_JNI(nativeForkSystemServer);
}
}
return newMethods;
}
#undef HOOK_JNI
jclass gClassRef;
jmethodID class_getName;
string get_class_name(JNIEnv *env, jclass clazz) {
if (!gClassRef) {
jclass cls = env->FindClass("java/lang/Class");
gClassRef = (jclass) env->NewGlobalRef(cls);
env->DeleteLocalRef(cls);
class_getName = env->GetMethodID(gClassRef, "getName", "()Ljava/lang/String;");
}
auto nameRef = (jstring) env->CallObjectMethod(clazz, class_getName);
const char *name = env->GetStringUTFChars(nameRef, nullptr);
string className(name);
env->ReleaseStringUTFChars(nameRef, name);
std::replace(className.begin(), className.end(), '.', '/');
return className;
}
// -----------------------------------------------------------------
// TODOs
int remote_check_hide(int uid, const char *process) { return 0; }
void remote_request_hide() {}
// -----------------------------------------------------------------
#define DCL_HOOK_FUNC(ret, func, ...) \
ret (*old_##func)(__VA_ARGS__); \
ret new_##func(__VA_ARGS__)
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());
auto newMethods = hookAndSaveJNIMethods(env, className.data(), methods, numMethods);
return old_functions->RegisterNatives(env, clazz, newMethods.get() ?: methods, numMethods);
}
DCL_HOOK_FUNC(int, jniRegisterNativeMethods,
JNIEnv *env, const char *className, const JNINativeMethod *methods, int numMethods) {
LOGD("hook: jniRegisterNativeMethods %s\n", className);
auto newMethods = hookAndSaveJNIMethods(env, className, methods, numMethods);
return old_jniRegisterNativeMethods(env, className, newMethods.get() ?: methods, numMethods);
}
DCL_HOOK_FUNC(int, fork) {
return current_ctx ? current_ctx->pid : old_fork();
}
DCL_HOOK_FUNC(int, selinux_android_setcontext,
uid_t uid, int isSystemServer, const char *seinfo, const char *pkgname) {
if (current_ctx && current_ctx->do_hide) {
// Ask magiskd to hide ourselves before switching context
// because magiskd socket is not accessible on Android 8.0+
remote_request_hide();
LOGD("hook: process successfully hidden\n");
}
return old_selinux_android_setcontext(uid, isSystemServer, seinfo, pkgname);
}
// -----------------------------------------------------------------
// The original android::AppRuntime virtual table
void **gAppRuntimeVTable;
// This method is a trampoline for hooking JNIEnv->RegisterNatives
void onVmCreated(void *self, JNIEnv* env) {
LOGD("hook: AppRuntime::onVmCreated\n");
// 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;
env->functions = new_functions;
}
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
bool swizzled = false;
DCL_HOOK_FUNC(void, setArgv0, void *self, const char *argv0, bool setProcName) {
if (swizzled) {
old_setArgv0(self, argv0, setProcName);
return;
}
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<void***>(self);
*reinterpret_cast<void***>(self) = new_table;
swizzled = true;
old_setArgv0(self, argv0, setProcName);
}
#undef DCL_HOOK_FUNC
// -----------------------------------------------------------------
void nativeSpecializeAppProcess_pre(HookContext *ctx, JNIEnv *env, jclass clazz) {
current_ctx = ctx;
const char *process = env->GetStringUTFChars(ctx->args->nice_name, nullptr);
LOGD("hook: %s %s\n", __FUNCTION__, process);
if (ctx->args->mount_external != 0 /* TODO: Handle MOUNT_EXTERNAL_NONE cases */
&& remote_check_hide(ctx->args->uid, process)) {
ctx->do_hide = true;
LOGI("hook: [%s] should be hidden\n", process);
}
env->ReleaseStringUTFChars(ctx->args->nice_name, process);
}
void nativeSpecializeAppProcess_post(HookContext *ctx, JNIEnv *env, jclass clazz) {
current_ctx = nullptr;
LOGD("hook: %s\n", __FUNCTION__);
if (ctx->do_hide)
self_unload();
}
// -----------------------------------------------------------------
int sigmask(int how, int signum) {
sigset_t set;
sigemptyset(&set);
sigaddset(&set, signum);
return sigprocmask(how, &set, nullptr);
}
// Do our own fork before loading any 3rd party code
// First block SIGCHLD, unblock after original fork is done
#define PRE_FORK() \
current_ctx = ctx; \
sigmask(SIG_BLOCK, SIGCHLD); \
ctx->pid = old_fork(); \
if (ctx->pid != 0) \
return;
// Unblock SIGCHLD in case the original method didn't
#define POST_FORK() \
current_ctx = nullptr; \
sigmask(SIG_UNBLOCK, SIGCHLD); \
if (ctx->pid != 0)\
return;
void nativeForkAndSpecialize_pre(HookContext *ctx, JNIEnv *env, jclass clazz) {
PRE_FORK();
nativeSpecializeAppProcess_pre(ctx, env, clazz);
}
void nativeForkAndSpecialize_post(HookContext *ctx, JNIEnv *env, jclass clazz) {
POST_FORK();
nativeSpecializeAppProcess_post(ctx, env, clazz);
}
// -----------------------------------------------------------------
void nativeForkSystemServer_pre(HookContext *ctx, JNIEnv *env, jclass clazz) {
if (env->functions == new_functions) {
// Restore JNIEnv
env->functions = old_functions;
if (gClassRef) {
env->DeleteGlobalRef(gClassRef);
gClassRef = nullptr;
class_getName = nullptr;
}
}
PRE_FORK();
LOGD("hook: %s\n", __FUNCTION__);
}
void nativeForkSystemServer_post(HookContext *ctx, JNIEnv *env, jclass clazz) {
POST_FORK();
LOGD("hook: %s\n", __FUNCTION__);
}
#undef PRE_FORK
#undef POST_FORK
// -----------------------------------------------------------------
bool hook_refresh() {
if (xhook_refresh(0) == 0) {
xhook_clear();
LOGI("hook: xhook success\n");
return true;
} else {
LOGE("hook: xhook failed\n");
return false;
}
}
int hook_register(const char *path, const char *symbol, void *new_func, void **old_func) {
int ret = xhook_register(path, symbol, new_func, old_func);
if (ret != 0) {
LOGE("hook: Failed to register hook \"%s\"\n", symbol);
return ret;
}
xhook_list->emplace_back(path, symbol, old_func);
return 0;
}
} // namespace
#define XHOOK_REGISTER_SYM(PATH_REGEX, SYM, NAME) \
hook_register(PATH_REGEX, SYM, (void*) new_##NAME, (void **) &old_##NAME)
#define XHOOK_REGISTER(PATH_REGEX, NAME) \
XHOOK_REGISTER_SYM(PATH_REGEX, #NAME, NAME)
#define ANDROID_RUNTIME ".*/libandroid_runtime.so$"
#define APP_PROCESS "^/system/bin/app_process.*"
void hook_functions() {
#ifdef MAGISK_DEBUG
xhook_enable_debug(1);
xhook_enable_sigsegv_protection(0);
#endif
default_new(xhook_list);
default_new(jni_hook_list);
default_new(jni_method_map);
XHOOK_REGISTER(ANDROID_RUNTIME, fork);
XHOOK_REGISTER(ANDROID_RUNTIME, selinux_android_setcontext);
XHOOK_REGISTER(ANDROID_RUNTIME, jniRegisterNativeMethods);
hook_refresh();
// Remove unhooked methods
xhook_list->erase(
std::remove_if(xhook_list->begin(), xhook_list->end(),
[](auto &t) { return *std::get<2>(t) == nullptr;}),
xhook_list->end());
if (old_jniRegisterNativeMethods == nullptr) {
LOGD("hook: jniRegisterNativeMethods not used\n");
// android::AndroidRuntime::setArgv0(const char *, bool)
XHOOK_REGISTER_SYM(APP_PROCESS, "_ZN7android14AndroidRuntime8setArgv0EPKcb", setArgv0);
hook_refresh();
// We still need old_jniRegisterNativeMethods as other code uses it
// android::AndroidRuntime::registerNativeMethods(_JNIEnv*, const char *, const JNINativeMethod *, int)
constexpr char sig[] = "_ZN7android14AndroidRuntime21registerNativeMethodsEP7_JNIEnvPKcPK15JNINativeMethodi";
*(void **) &old_jniRegisterNativeMethods = dlsym(RTLD_DEFAULT, sig);
}
}
bool unhook_functions() {
JNIEnv* env;
if (g_jvm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6) != JNI_OK)
return false;
// Do NOT call any destructors
operator delete(jni_method_map);
// Directly unmap the whole memory block
jni_hook::memory_block::release();
// Unhook JNI methods
if (!jni_hook_list->empty() && old_jniRegisterNativeMethods(env,
"com/android/internal/os/Zygote",
jni_hook_list->data(), jni_hook_list->size()) != 0) {
LOGE("hook: Failed to register JNI hook\n");
return false;
}
delete jni_hook_list;
// Unhook xhook
for (auto &[path, sym, old_func] : *xhook_list) {
if (xhook_register(path, sym, *old_func, nullptr) != 0) {
LOGE("hook: Failed to register hook \"%s\"\n", sym);
return false;
}
}
delete xhook_list;
return hook_refresh();
}