forkism / riru

Inject into zygote process

Riru

Riru only does one thing, inject into zygote in order to allow modules run their codes in apps or the system server.

The name, Riru, comes from a character. (https://www.pixiv.net/member_illust.php?mode=medium&illust_id=74128856)

Requirements

Android 6.0+ devices rooted with Magisk

Guide

Install

• From Magisk Manager

  1. Search "Riru" in Magisk Manager
  2. Install the module named "Riru"

  The Magisk version requirement is enforced by Magisk Manager. At the time of the release of Magisk v21.1, the requirement is v20.4.

• Manually

  1. Download the zip from GitHub release
  2. Install in Magisk Manager (Modules - Install from storage - Select downloaded zip)

• "Riru" app (show Riru status)

  Download

If you are use other modules that changes ro.dalvik.vm.native.bridge, Riru will not work. (Riru will automatically set it back)

A typical example is, some "optimize" modules changes this property. Since changing this property is meaningless for "optimization", their quality is very questionable. In fact, changing properties for optimization is a joke.

Config

• When the file /data/adb/riru/disable exists, Riru will do nothing
• When the file /data/adb/riru/enable_hide exists, the hide mechanism will be enabled (also requires the support of the modules)

How Riru works?

• How to inject into zygote process?

  Before v22.0, we use the method of replacing a system library (libmemtrack) that will be loaded by zygote. However, it seems to cause some weird problems. Maybe because libmemtrack is used by something else.

  Then we found a super easy way, the "native bridge" (ro.dalvik.vm.native.bridge). The specific "so" file will be automatically "dlopen-ed" and "dlclose-ed" by the system. This way is from here.

• How to know if we are in an app process or a system server process?

  Some JNI functions (com.android.internal.os.Zygote#nativeForkAndSpecialize & com.android.internal.os.Zygote#nativeForkSystemServer) is to fork the app process or the system server process. So we need to replace these functions to ours. This part is simple, hook jniRegisterNativeMethods since all Java native methods in libandroid_runtime.so is registered through this function. Then we can call the original jniRegisterNativeMethods again to replace them.

How hide Hide works?

From v22.0, Riru provide a hide mechanism (idea from Haruue Icymoon), make the memory of Riru and module to anonymous memory to hide from "/proc/maps string scanning".

Build

Run gradle task :riru:assembleRelease task from Android Studio or the terminal, zip will be saved to out.

Module template

https://github.com/RikkaApps/Riru-ModuleTemplate

Module API changes

https://github.com/RikkaApps/Riru-ModuleTemplate/blob/master/README.md#api-changes