Support code injection on Android 12

This commit is contained in:
topjohnwu 2021-08-11 00:00:21 -07:00
parent 25efdd3d6f
commit a260e99090
6 changed files with 180 additions and 53 deletions

View File

@ -87,9 +87,8 @@ static void inject_cleanup_wait() {
__attribute__((constructor))
static void inject_init() {
inject_logging();
if (getenv(INJECT_ENV_2)) {
inject_logging();
LOGD("zygote: inject 2nd stage\n");
active_threads = 1;
unsetenv(INJECT_ENV_2);
@ -97,6 +96,7 @@ static void inject_init() {
// Get our own handle
self_handle = dlopen(INJECT_LIB_2, RTLD_LAZY);
dlclose(self_handle);
unlink(INJECT_LIB_2);
hook_functions();
@ -105,6 +105,7 @@ static void inject_init() {
active_threads++;
new_daemon_thread(&unload_first_stage);
} else if (char *env = getenv(INJECT_ENV_1)) {
inject_logging();
LOGD("zygote: inject 1st stage\n");
if (env[0] == '1')
@ -117,6 +118,7 @@ static void inject_init() {
cp_afc(INJECT_LIB_1, INJECT_LIB_2);
dlopen(INJECT_LIB_2, RTLD_LAZY);
unlink(INJECT_LIB_1);
unsetenv(INJECT_ENV_1);
}
}
@ -128,7 +130,7 @@ int app_process_main(int argc, char *argv[]) {
return 1;
int in = xopen(buf, O_RDONLY);
int out = xopen(INJECT_LIB_1, O_CREAT | O_WRONLY | O_TRUNC, 0777);
int out = xopen(INJECT_LIB_1, O_WRONLY | O_CREAT, 0644);
sendfile(out, in, nullptr, INT_MAX);
close(in);
close(out);

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@ -1,3 +1,4 @@
#include <dlfcn.h>
#include <xhook.h>
#include <utils.hpp>
#include <flags.hpp>
@ -64,13 +65,17 @@ struct HookContext {
void *raw_args;
};
};
struct vtable_t;
static vector<tuple<const char *, const char *, void **>> *xhook_list;
static vector<JNINativeMethod> *jni_hook_list;
static hash_map<xstring, tree_map<xstring, tree_map<xstring, void *>>> *jni_method_map;
static JavaVM *g_jvm;
static HookContext *current_ctx;
static JavaVM *g_jvm;
static vtable_t *gAppRuntimeVTable;
static const JNINativeInterface *old_functions;
static JNINativeInterface *new_functions;
#define DCL_HOOK_FUNC(ret, func, ...) \
static ret (*old_##func)(__VA_ARGS__); \
@ -103,10 +108,8 @@ if (methods[i].name == #method##sv) { \
continue; \
}
DCL_HOOK_FUNC(int, jniRegisterNativeMethods,
static unique_ptr<JNINativeMethod[]> hookAndSaveJNIMethods(
JNIEnv *env, const char *className, const JNINativeMethod *methods, int numMethods) {
LOGD("hook: jniRegisterNativeMethods %s", className);
if (g_jvm == nullptr) {
// Save for later unhooking
env->GetJavaVM(&g_jvm);
@ -129,7 +132,40 @@ DCL_HOOK_FUNC(int, jniRegisterNativeMethods,
HOOK_JNI(nativeForkSystemServer);
}
}
return newMethods;
}
static jclass gClassRef;
static jmethodID class_getName;
static 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;
}
// -----------------------------------------------------------------
static jint new_env_RegisterNatives(
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);
}
@ -148,11 +184,56 @@ DCL_HOOK_FUNC(int, selinux_android_setcontext,
return old_selinux_android_setcontext(uid, isSystemServer, seinfo, pkgname);
}
static int sigmask(int how, int signum) {
sigset_t set;
sigemptyset(&set);
sigaddset(&set, signum);
return sigprocmask(how, &set, nullptr);
// -----------------------------------------------------------------
// 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);
};
// This method is a trampoline for hooking JNIEnv->RegisterNatives
DCL_HOOK_FUNC(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;
// 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);
}
// This method is a trampoline for swizzling android::AppRuntime vtable
static 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");
// 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;
swizzled = true;
old_setArgv0(self, argv0, setProcName);
}
// -----------------------------------------------------------------
@ -181,6 +262,13 @@ static void nativeSpecializeAppProcess_post(HookContext *ctx, JNIEnv *env, jclas
// -----------------------------------------------------------------
static 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() \
@ -210,6 +298,16 @@ static void nativeForkAndSpecialize_post(HookContext *ctx, JNIEnv *env, jclass c
// -----------------------------------------------------------------
static 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__);
}
@ -245,22 +343,50 @@ static int hook_register(const char *path, const char *symbol, void *new_func, v
return 0;
}
template<class T>
static inline void default_new(T *&p) { p = new T(); }
#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) \
hook_register(PATH_REGEX, #NAME, (void*) new_##NAME, (void **) &old_##NAME)
XHOOK_REGISTER_SYM(PATH_REGEX, #NAME, NAME)
#define ANDROID_RUNTIME ".*/libandroid_runtime.so$"
#define APP_PROCESS "^/system/bin/app_process.*"
void hook_functions() {
#ifdef MAGISK_DEBUG
xhook_enable_debug(1);
xhook_enable_sigsegv_protection(0);
#endif
xhook_list = new remove_pointer_t<decltype(xhook_list)>();
jni_hook_list = new remove_pointer_t<decltype(jni_hook_list)>();
jni_method_map = new remove_pointer_t<decltype(jni_method_map)>();
default_new(xhook_list);
default_new(jni_hook_list);
default_new(jni_method_map);
XHOOK_REGISTER(".*\\libandroid_runtime.so$", jniRegisterNativeMethods);
XHOOK_REGISTER(".*\\libandroid_runtime.so$", fork);
XHOOK_REGISTER(".*\\libandroid_runtime.so$", selinux_android_setcontext);
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() {

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@ -11,11 +11,11 @@
// Unmap all pages matching the name
void unmap_all(const char *name);
// Get library name and base address that contains the function
uintptr_t get_function_lib(uintptr_t addr, char *lib);
// Get library name + offset (from start of ELF), given function address
uintptr_t get_function_off(int pid, uintptr_t addr, char *lib);
// Get library base address with name
uintptr_t get_remote_lib(int pid, const char *lib);
// Get function address, given library name + offset
uintptr_t get_function_addr(int pid, const char *lib, uintptr_t off);
void self_unload();
void hook_functions();

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@ -5,7 +5,8 @@ namespace jni_hook {
// We know our minimum alignment is WORD size (size of pointer)
static constexpr size_t ALIGN = sizeof(long);
static constexpr size_t CAPACITY = (1 << 24);
// 4MB is more than enough
static constexpr size_t CAPACITY = (1 << 22);
// No need to be thread safe as the initial mmap always happens on the main thread
static uint8_t *_area = nullptr;

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@ -226,16 +226,15 @@ uintptr_t remote_call_abi(int pid, uintptr_t func_addr, int nargs, va_list va) {
uintptr_t remote_call_vararg(int pid, uintptr_t addr, int nargs, ...) {
char lib_name[4096];
auto local = get_function_lib(addr, lib_name);
if (local == 0)
auto off = get_function_off(getpid(), addr, lib_name);
if (off == 0)
return 0;
auto remote = get_remote_lib(pid, lib_name);
auto remote = get_function_addr(pid, lib_name, off);
if (remote == 0)
return 0;
addr = addr - local + remote;
va_list va;
va_start(va, nargs);
auto result = remote_call_abi(pid, addr, nargs, va);
auto result = remote_call_abi(pid, remote, nargs, va);
va_end(va);
return result;
}

View File

@ -1,3 +1,4 @@
#include <cinttypes>
#include <utils.hpp>
#include "inject.hpp"
@ -9,10 +10,11 @@ namespace {
struct map_info {
uintptr_t start;
uintptr_t end;
uintptr_t off;
int perms;
char *path;
map_info() : start(0), end(0), perms(0), path(nullptr) {}
map_info() : start(0), end(0), off(0), perms(0), path(nullptr) {}
enum {
EXEC = (1 << 0),
@ -30,27 +32,24 @@ static void parse_maps(int pid, Func fn) {
// format: start-end perms offset dev inode path
sprintf(file, "/proc/%d/maps", pid);
file_readline(true, file, [=](string_view l) -> bool {
char *pos = (char *) l.data();
char *line = (char *) l.data();
map_info info;
char perm[5];
int path_off;
// Parse address hex strings
info.start = strtoul(pos, &pos, 16);
info.end = strtoul(++pos, &pos, 16);
if (sscanf(line, "%" PRIxPTR "-%" PRIxPTR " %4s %" PRIxPTR " %*x:%*x %*d %n%*s",
&info.start, &info.end, perm, &info.off, &path_off) != 4)
return true;
// Parse permissions
if (*(++pos) != '-')
if (perm[0] != '-')
info.perms |= map_info::READ;
if (*(++pos) != '-')
if (perm[1] != '-')
info.perms |= map_info::WRITE;
if (*(++pos) != '-')
if (perm[2] != '-')
info.perms |= map_info::EXEC;
pos += 3;
// Skip everything except path
int path_off;
sscanf(pos, "%*s %*s %*s %n%*s", &path_off);
pos += path_off;
info.path = pos;
info.path = line + path_off;
return fn(info);
});
@ -74,28 +73,28 @@ void unmap_all(const char *name) {
}
}
uintptr_t get_function_lib(uintptr_t addr, char *lib) {
uintptr_t base = 0;
parse_maps(getpid(), [=, &base](map_info &info) -> bool {
uintptr_t get_function_off(int pid, uintptr_t addr, char *lib) {
uintptr_t off = 0;
parse_maps(pid, [=, &off](map_info &info) -> bool {
if (addr >= info.start && addr < info.end) {
if (lib)
strcpy(lib, info.path);
base = info.start;
off = addr - info.start + info.off;
return false;
}
return true;
});
return base;
return off;
}
uintptr_t get_remote_lib(int pid, const char *lib) {
uintptr_t base = 0;
parse_maps(pid, [=, &base](map_info &info) -> bool {
uintptr_t get_function_addr(int pid, const char *lib, uintptr_t off) {
uintptr_t addr = 0;
parse_maps(pid, [=, &addr](map_info &info) -> bool {
if (strcmp(info.path, lib) == 0 && (info.perms & map_info::EXEC)) {
base = info.start;
addr = info.start - info.off + off;
return false;
}
return true;
});
return base;
return addr;
}