safetynet-fix/riru

Riru - Template

Riru module template.

Build

1. Rename module.example.gradle to module.gradle
2. Replace module info in module.gradle (all lines end with "replace with yours")
3. Write your codes
4. Run gradle task :module:assembleRelease task from Android Studio or command line, zip will be saved in out.

File structure

A Riru module is a Magisk module, please read Magisk module document first.

If the folder $MODPATH/riru exists, the module is considered as a Riru module. All files in $MODPATH/riru/lib(64) will be loaded by Riru.

API changes

API 26 (Riru v26)

• Remove the support of pre-24 modules

• /data/adb/dev_random is planned to be moved to another place in the next major version

• Libraries in /dev do not have stacktrace, developers have to put so file into /system, Riru v26 makes this simpler

  Create an empty file, libxxx (no .so suffix), at $MODPATH/riru/lib(64), Riru will try to load /system/lib(64)/libxxx.so

API 25 (Riru v25)

• Modules can be unloaded (see main.cpp)
• shouldSkipUid is removed for API 25 modules

API 24 (Riru v24)

• The Riru API version is unified with Riru version, now the API version is 24
• The /data/adb/riru/modules/<name> folder is deprecated, modules only need to place library files in $MODPATH/riru/lib(64) (see customize.sh post-fs-data.sh)
• The init function is called only once (see main.cpp)
• It's recommended to place modules files in the Magisk module folder, zygote has permission read this folder directly (the path is passed through init function, see main.cpp)

API 10 (Riru v23)

Background of rirud:

Riru v22.0 move config files to /data/adb, this makes patch SELinux rules a must. However Magisk's sepolicy.rule actually not work for maybe lots of devices. As the release of Riru v22.0, these people "suddenly" appears.

sepolicy.rule support was added from Magisk v20.2, a long time ago, no one report to Magisk 😒.

To workaround this "problem", "rirud" is introduced. It will be started by post-fs-data.sh and run a socket runs under u:r:zygote:s0 context. All file operations can be done through this socket.

From Riru v23, "read file" and "read dir" function are added for "rirud". Modules can use this to read files that zygote itself has not permission to access. Note, for hide purpose, "rirud" socket is only available before system_server is started.

In order to give the module enough freedom (like how to allocate memory), there is no "API". The module needs to implement socket codes by itself.

Pseudocode of read file:

socket(PF_UNIX, SOCK_STREAM)
setup_sockaddr("rirud")

write(ACTION_READ_FILE /* 4 */, sizeof(uint32))
write(path_size, sizeof(uint32))
write(path, path_size)

errno = read(sizeof(int32_t)) // errno of "open" in "rirud"
if (errno != 0) return

bytes_count = read(sizeof(int32_t))

if (bytes_count > 0) {
  // file has size
  // read total "bytes_count" bytes
} else if (bytes_count == 0) {
  // file has no size, read until 0
  // read until 0
}

Pseudocode of read dir:

socket(PF_UNIX, SOCK_STREAM)
setup_sockaddr("rirud")

write(ACTION_READ_DIR /* 5 */, sizeof(uint32))
write(path_size, sizeof(uint32))
write(path, path_size)

errno = read(sizeof(int32_t)) // errno of "opendir" in "rirud"
if (errno != 0) return

while (true) {
  write(1 /* continue */, sizeof(uint8))

  reply = read(sizeof(int32))
  if (reply == -1) break // end
  if (reply != 0) continue  // reply is errno of "readdir" in "rirud"

  d_type = read(sizeof(uchar))
  d_name = read(256)
}

Example implementation: https://github.com/RikkaApps/Riru-LocationReportEnabler/commit/89b2e396efcd928121ba3d254b96af1560cfaf4d

API 9 (Riru v22)

API

Functions like nativeForkAnd... do not need to be exported directly. The only function to export is void *init(void *). See the comment of init and template's implementation for more.

This has these advantages:

• Module can support different Riru versions
• Riru itself will not relay on ".prop" file (unreliable) to get module information

Riru

Starting v22.0, Riru has switched to "native bridge" (ro.dalvik.vm.native.bridge) to inject zygote, this will lead Riru and modules be loaded later (LoadNativeBridge vs __attribute__((constructor))).

For most modules, this should have no problem, but modules like Xposed frameworks may have to make changes.

Magisk may provider Riru-like features in the far future, and of course, it will have more strict restrictions, module codes will not be run in zygote. Maybe Xposed framework modules should prepare for this?

Riru v22 also provides hide function to make the memory of the module to anonymous memory (see the implementation). This is an opt-in behavior (module->supportHide) and Riru itself also has a global toggle (/data/adb/riru/enable_hide).

Module installer

RIRU_PATH has been changed to /data/adb/riru for hide purpose. If you have other files in /data/misc/riru, move them here (or anywhere else if you want).

Note /data/adb/riru have the same SELinux like other Magisk files (set by Riru in post-fs-data), u:object_r:magisk_file:s0. DO NOT reset the context to something else.