Magisk/native/jni/zygisk/hook.cpp
2022-03-02 22:01:35 -08:00

673 lines
21 KiB
C++

#include <android/dlext.h>
#include <sys/mount.h>
#include <dlfcn.h>
#include <bitset>
#include <xhook.h>
#include <utils.hpp>
#include <flags.h>
#include <daemon.hpp>
#include "zygisk.hpp"
#include "memory.hpp"
#include "module.hpp"
#include "deny/deny.hpp"
using namespace std;
using jni_hook::hash_map;
using jni_hook::tree_map;
using xstring = jni_hook::string;
// Extreme verbose logging
//#define ZLOGV(...) ZLOGD(__VA_ARGS__)
#define ZLOGV(...)
static bool unhook_functions();
namespace {
enum {
DO_UNMOUNT,
FORK_AND_SPECIALIZE,
APP_SPECIALIZE,
SERVER_SPECIALIZE,
CAN_DLCLOSE,
FLAG_MAX
};
#define DCL_PRE_POST(name) \
void name##_pre(); \
void name##_post();
struct HookContext {
JNIEnv *env;
union {
AppSpecializeArgs_v3 *args;
ServerSpecializeArgs_v1 *server_args;
void *raw_args;
};
const char *process;
vector<ZygiskModule> modules;
bitset<FLAG_MAX> state;
int pid;
uint32_t flags;
HookContext() : pid(-1), flags(0) {}
static void close_fds();
void unload_zygisk();
DCL_PRE_POST(fork)
void run_modules_pre(const vector<int> &fds);
void run_modules_post();
DCL_PRE_POST(nativeForkAndSpecialize)
DCL_PRE_POST(nativeSpecializeAppProcess)
DCL_PRE_POST(nativeForkSystemServer)
};
#undef DCL_PRE_POST
// Global variables
vector<tuple<const char *, const char *, void **>> *xhook_list;
map<string, vector<JNINativeMethod>, StringCmp> *jni_hook_list;
hash_map<xstring, tree_map<xstring, tree_map<xstring, void *>>> *jni_method_map;
// Current context
HookContext *g_ctx;
const JNINativeInterface *old_functions;
JNINativeInterface *new_functions;
#define HOOK_JNI(method) \
if (methods[i].name == #method##sv) { \
int j = 0; \
for (; j < method##_methods_num; ++j) { \
if (strcmp(methods[i].signature, method##_methods[j].signature) == 0) { \
jni_hook_list->try_emplace(className).first->second.push_back(methods[i]); \
method##_orig = methods[i].fnPtr; \
newMethods[i] = method##_methods[j]; \
ZLOGI("replaced %s#" #method "\n", className); \
--hook_cnt; \
break; \
} \
} \
if (j == method##_methods_num) { \
ZLOGE("unknown signature of %s#" #method ": %s\n", className, methods[i].signature); \
} \
continue; \
}
// JNI method hook definitions, auto generated
#include "jni_hooks.hpp"
#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;
}
// -----------------------------------------------------------------
#define DCL_HOOK_FUNC(ret, func, ...) \
ret (*old_##func)(__VA_ARGS__); \
ret new_##func(__VA_ARGS__)
jint env_RegisterNatives(
JNIEnv *env, jclass clazz, const JNINativeMethod *methods, jint numMethods) {
auto className = get_class_name(env, clazz);
ZLOGV("JNIEnv->RegisterNatives [%s]\n", className.data());
auto newMethods = hookAndSaveJNIMethods(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) {
ZLOGV("jniRegisterNativeMethods [%s]\n", className);
auto newMethods = hookAndSaveJNIMethods(className, methods, numMethods);
return old_jniRegisterNativeMethods(env, className, newMethods.get() ?: methods, numMethods);
}
// Skip actual fork and return cached result if applicable
// Also unload first stage zygisk if necessary
DCL_HOOK_FUNC(int, fork) {
return (g_ctx && g_ctx->pid >= 0) ? g_ctx->pid : old_fork();
}
// Unmount stuffs in the process's private mount namespace
DCL_HOOK_FUNC(int, unshare, int flags) {
int res = old_unshare(flags);
if (g_ctx && (flags & CLONE_NEWNS) != 0 && res == 0) {
if (g_ctx->state[DO_UNMOUNT]) {
revert_unmount();
} else {
umount2("/system/bin/app_process64", MNT_DETACH);
umount2("/system/bin/app_process32", MNT_DETACH);
}
}
return res;
}
// A place to clean things up before zygote evaluates fd table
DCL_HOOK_FUNC(void, android_log_close) {
HookContext::close_fds();
old_android_log_close();
}
// Last point before process secontext changes
DCL_HOOK_FUNC(int, selinux_android_setcontext,
uid_t uid, int isSystemServer, const char *seinfo, const char *pkgname) {
if (g_ctx) {
g_ctx->state[CAN_DLCLOSE] = unhook_functions();
}
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) {
ZLOGD("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 = &env_RegisterNatives;
// 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. It will also restore the vtable.
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;
}
ZLOGD("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 hookJniNativeMethods(JNIEnv *env, const char *clz, JNINativeMethod *methods, int numMethods) {
auto class_map = jni_method_map->find(clz);
if (class_map == jni_method_map->end()) {
for (int i = 0; i < numMethods; ++i) {
methods[i].fnPtr = nullptr;
}
return;
}
vector<JNINativeMethod> hooks;
for (int i = 0; i < numMethods; ++i) {
auto method_map = class_map->second.find(methods[i].name);
if (method_map != class_map->second.end()) {
auto it = method_map->second.find(methods[i].signature);
if (it != method_map->second.end()) {
// Copy the JNINativeMethod
hooks.push_back(methods[i]);
// Save the original function pointer
methods[i].fnPtr = it->second;
// Do not allow double hook, remove method from map
method_map->second.erase(it);
continue;
}
}
// No matching method found, set fnPtr to null
methods[i].fnPtr = nullptr;
}
if (hooks.empty())
return;
old_jniRegisterNativeMethods(env, clz, hooks.data(), hooks.size());
}
ZygiskModule::ZygiskModule(int id, void *handle, void *entry)
: raw_entry(entry), api(this), id(id), handle(handle) {}
ApiTable::ApiTable(ZygiskModule *m)
: module(m), registerModule(&ZygiskModule::RegisterModule) {}
bool ZygiskModule::RegisterModule(ApiTable *table, long *module) {
long ver = *module;
// Unsupported version
if (ver > ZYGISK_API_VERSION)
return false;
// Set the actual module_abi*
table->module->ver = module;
// Fill in API accordingly with module API version
switch (ver) {
case 3:
case 2:
table->v2.getModuleDir = [](ZygiskModule *m) { return m->getModuleDir(); };
table->v2.getFlags = [](auto) { return ZygiskModule::getFlags(); };
// fallthrough
case 1:
table->v1.hookJniNativeMethods = &hookJniNativeMethods;
table->v1.pltHookRegister = [](const char *p, const char *s, void *n, void **o) {
xhook_register(p, s, n, o);
};
table->v1.pltHookExclude = [](const char *p, const char *s) {
xhook_ignore(p, s);
};
table->v1.pltHookCommit = []{ bool r = xhook_refresh(0) == 0; xhook_clear(); return r; };
table->v1.connectCompanion = [](ZygiskModule *m) { return m->connectCompanion(); };
table->v1.setOption = [](ZygiskModule *m, auto opt) { m->setOption(opt); };
break;
default:
// Unknown version number
return false;
}
return true;
}
int ZygiskModule::connectCompanion() const {
if (int fd = zygisk_request(ZygiskRequest::CONNECT_COMPANION); fd >= 0) {
write_int(fd, id);
return fd;
}
return -1;
}
int ZygiskModule::getModuleDir() const {
if (int fd = zygisk_request(ZygiskRequest::GET_MODDIR); fd >= 0) {
write_int(fd, id);
int dfd = recv_fd(fd);
close(fd);
return dfd;
}
return -1;
}
void ZygiskModule::setOption(zygisk::Option opt) {
if (g_ctx == nullptr)
return;
switch (opt) {
case zygisk::FORCE_DENYLIST_UNMOUNT:
g_ctx->state[DO_UNMOUNT] = true;
break;
case zygisk::DLCLOSE_MODULE_LIBRARY:
unload = true;
break;
}
}
uint32_t ZygiskModule::getFlags() {
return g_ctx ? (g_ctx->flags & ~PRIVATE_MASK) : 0;
}
void HookContext::run_modules_pre(const vector<int> &fds) {
// Since we directly use the pointer to elements in the vector, in order to prevent dangling
// pointers, the vector has to be pre-allocated to ensure reallocation does not occur
modules.reserve(fds.size());
for (int i = 0; i < fds.size(); ++i) {
android_dlextinfo info {
.flags = ANDROID_DLEXT_USE_LIBRARY_FD,
.library_fd = fds[i],
};
if (void *h = android_dlopen_ext("/jit-cache", RTLD_LAZY, &info)) {
if (void *e = dlsym(h, "zygisk_module_entry")) {
modules.emplace_back(i, h, e);
}
}
close(fds[i]);
}
// Record all open fds
bitset<1024> open_fds;
auto dir = open_dir("/proc/self/fd");
for (dirent *entry; (entry = xreaddir(dir.get()));) {
int fd = parse_int(entry->d_name);
if (fd < 0 || fd >= 1024) {
close(fd);
continue;
}
open_fds[fd] = true;
}
for (auto &m : modules) {
m.entry(&m.api, env);
if (state[APP_SPECIALIZE]) {
m.preAppSpecialize(args);
} else if (state[SERVER_SPECIALIZE]) {
m.preServerSpecialize(server_args);
}
}
// Add all ignored fd onto whitelist
if (state[APP_SPECIALIZE] && args->fds_to_ignore) {
int len = env->GetArrayLength(*args->fds_to_ignore);
int *arr = env->GetIntArrayElements(*args->fds_to_ignore, nullptr);
for (int i = 0; i < len; ++i) {
int fd = arr[i];
if (fd >= 0 && fd < 1024) {
open_fds[fd] = true;
}
}
env->ReleaseIntArrayElements(*args->fds_to_ignore, arr, 0);
}
// Close all unrecorded fds
rewinddir(dir.get());
for (dirent *entry; (entry = xreaddir(dir.get()));) {
int fd = parse_int(entry->d_name);
if (fd < 0 || fd >= 1024 || !open_fds[fd]) {
close(fd);
}
}
}
void HookContext::run_modules_post() {
for (const auto &m : modules) {
if (state[APP_SPECIALIZE]) {
m.postAppSpecialize(args);
} else if (state[SERVER_SPECIALIZE]) {
m.postServerSpecialize(server_args);
}
m.doUnload();
}
}
void HookContext::close_fds() {
close(logd_fd.exchange(-1));
}
void HookContext::unload_zygisk() {
if (state[CAN_DLCLOSE]) {
// Do NOT call the destructor
operator delete(jni_method_map);
// Directly unmap the whole memory block
jni_hook::memory_block::release();
// Strip out all API function pointers
for (auto &m : modules) {
memset(&m.api, 0, sizeof(m.api));
}
new_daemon_thread(reinterpret_cast<thread_entry>(&dlclose), self_handle);
}
}
// -----------------------------------------------------------------
void HookContext::nativeSpecializeAppProcess_pre() {
g_ctx = this;
state[APP_SPECIALIZE] = true;
process = env->GetStringUTFChars(args->nice_name, nullptr);
if (state[FORK_AND_SPECIALIZE]) {
ZLOGV("pre forkAndSpecialize [%s]\n", process);
} else {
ZLOGV("pre specialize [%s]\n", process);
}
vector<int> module_fds;
int fd = remote_get_info(args->uid, process, &flags, module_fds);
if ((flags & UNMOUNT_MASK) == UNMOUNT_MASK) {
ZLOGI("[%s] is on the denylist\n", process);
state[DO_UNMOUNT] = true;
} else if (fd >= 0) {
run_modules_pre(module_fds);
}
close(fd);
close_fds();
android_logging();
}
void HookContext::nativeSpecializeAppProcess_post() {
if (state[FORK_AND_SPECIALIZE]) {
ZLOGV("post forkAndSpecialize [%s]\n", process);
} else {
ZLOGV("post specialize [%s]\n", process);
}
env->ReleaseStringUTFChars(args->nice_name, process);
run_modules_post();
if (flags & PROCESS_IS_MAGISK_APP) {
setenv("ZYGISK_ENABLED", "1", 1);
}
g_ctx = nullptr;
if (!state[FORK_AND_SPECIALIZE]) {
unload_zygisk();
}
}
void HookContext::nativeForkSystemServer_pre() {
fork_pre();
state[SERVER_SPECIALIZE] = true;
if (pid == 0) {
ZLOGV("pre forkSystemServer\n");
vector<int> module_fds;
int fd = remote_get_info(1000, "system_server", &flags, module_fds);
if (fd >= 0) {
if (module_fds.empty()) {
write_int(fd, 0);
} else {
run_modules_pre(module_fds);
// Send the bitset of module status back to magiskd from system_server
dynamic_bitset bits;
for (const auto &m : modules)
bits[m.getId()] = true;
write_int(fd, bits.slots());
for (int i = 0; i < bits.slots(); ++i) {
auto l = bits.get_slot(i);
xwrite(fd, &l, sizeof(l));
}
}
close(fd);
}
close_fds();
android_logging();
}
}
void HookContext::nativeForkSystemServer_post() {
if (pid == 0) {
ZLOGV("post forkSystemServer\n");
run_modules_post();
}
fork_post();
}
void HookContext::nativeForkAndSpecialize_pre() {
fork_pre();
state[FORK_AND_SPECIALIZE] = true;
if (pid == 0) {
nativeSpecializeAppProcess_pre();
}
}
void HookContext::nativeForkAndSpecialize_post() {
if (pid == 0) {
nativeSpecializeAppProcess_post();
}
fork_post();
}
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
void HookContext::fork_pre() {
g_ctx = this;
sigmask(SIG_BLOCK, SIGCHLD);
pid = old_fork();
}
// Unblock SIGCHLD in case the original method didn't
void HookContext::fork_post() {
sigmask(SIG_UNBLOCK, SIGCHLD);
g_ctx = nullptr;
unload_zygisk();
}
} // namespace
static bool hook_refresh() {
if (xhook_refresh(0) == 0) {
xhook_clear();
return true;
} else {
ZLOGE("xhook failed\n");
return false;
}
}
static 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) {
ZLOGE("Failed to register hook \"%s\"\n", symbol);
return ret;
}
xhook_list->emplace_back(path, symbol, old_func);
return 0;
}
#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() {
#if 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, unshare);
XHOOK_REGISTER(ANDROID_RUNTIME, jniRegisterNativeMethods);
XHOOK_REGISTER(ANDROID_RUNTIME, selinux_android_setcontext);
XHOOK_REGISTER_SYM(ANDROID_RUNTIME, "__android_log_close", android_log_close);
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) {
ZLOGD("jniRegisterNativeMethods not hooked, using fallback\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);
}
}
static bool unhook_functions() {
bool success = true;
// Restore JNIEnv
if (g_ctx->env->functions == new_functions) {
g_ctx->env->functions = old_functions;
if (gClassRef) {
g_ctx->env->DeleteGlobalRef(gClassRef);
gClassRef = nullptr;
class_getName = nullptr;
}
}
// Unhook JNI methods
for (const auto &[clz, methods] : *jni_hook_list) {
if (!methods.empty() && old_jniRegisterNativeMethods(
g_ctx->env, clz.data(), methods.data(), methods.size()) != 0) {
ZLOGE("Failed to restore JNI hook of class [%s]\n", clz.data());
success = false;
}
}
delete jni_hook_list;
// Unhook xhook
for (const auto &[path, sym, old_func] : *xhook_list) {
if (xhook_register(path, sym, *old_func, nullptr) != 0) {
ZLOGE("Failed to register xhook [%s]\n", sym);
success = false;
}
}
delete xhook_list;
if (!hook_refresh()) {
ZLOGE("Failed to restore xhook\n");
success = false;
}
return success;
}