Due to changes in ec3705f2ed187863efc34af5415495e1ee7775d2, the app can
no longer communicate with the dameon through a socket opened on the
daemon side due to SELinux restrictions. The workaround here is to have
the daemon decide a socket name, send it to the app, have the app create
the socket server, then finally the daemon connects to the app through
the socket.
Introduce new domain `magisk_client` and new file type `magisk_exec`.
Connection to magiskd's always-on socket is restricted to magisk_client
only. Whitelisted process domains can transit to magisk_client through
executing files labelled magisk_exec. The main magisk binary shall be
the only file labelled as magisk_exec throughout the whole system.
All processes thus are no longer allowed to connect to magiskd directly
without going through the proper magisk binary.
Connection failures are silenced from audit logs with dontaudit rules,
so crazy processes which traverse through all unix domain sockets to try
connection can no longer check logcat to know the actual reason behind
EACCES, leaking the denied process policy (which is u:r:magisk:s0).
This also allows us to remove many rules that open up holes in
untrusted_app domains that were used to make remote shell work properly.
Since all processes establishing the remote shell are now restricted to
the magisk_client domain, all these rules are moved to magisk_client.
This makes Magisk require fewer compromises in Android's security model.
Note: as of this commit, requesting new root access via Magisk Manager
will stop working as Magisk Manager can no longer communicate with
magiskd directly. This will be addressed in a future commit that
involves changes in both native and application side.
It is possible that a module is breaking the device so bad that zygote
cannot even be started. In this case, system_server cannot start and
detect the safe mode key combo, set the persist property, and reboot.
Also on old Android versions, the system directly goes to safe mode
after detecting a key combo without rebooting, defeating the purpose of
Magisk's safe mode protection if we only check for the persist property.
Directly adding key combo check natively in magiskd allows us to enter
Magisk safe mode before the system is even aware of it.
The existing method for handling legacy SAR is:
1. Mount /sbin tmpfs overlay
2. Dump all patched/new files into /sbin
3. Magic mount root dir and re-exec patched stock init
With Android 11 removing the /sbin folder, it is quite obvious that
things completely break down right in step 1.
To overcome this issue, we have to find a way to swap out the init
binary AFTER we re-exec stock init. This is where 2SI comes to rescue!
2SI normal boot procedure is:
1st stage -> Load sepolicy -> 2nd stage -> boot continue...
2SI Magisk boot procedure is:
MagiskInit 1st stage -> Stock 1st stage -> MagiskInit 2nd Stage ->
-> Stock init load sepolicy -> Stock 2nd stage -> boot continue...
As you can see, the trick is to make stock 1st stage init re-exec back
into MagiskInit so we can do our setup. This is possible by manipulating
some ramdisk files on initramfs based 2SI devices (old ass non SAR
devices AND super modern devices like Pixel 3/4), but not possible
on device that are stuck using legacy SAR (device that are not that
modern but not too old, like Pixel 1/2. Fucking Google logic!!)
This commit introduces a new way to intercept stock init re-exec flow:
ptrace init with forked tracer, monitor PTRACE_EVENT_EXEC, then swap
out the init file with bind mounts right before execv returns!
Going through this flow however will lose some necessary backup files,
so some bookkeeping has to be done by making the tracer hold these
files in memory and act as a daemon. 2nd stage MagiskInit will ack the
daemon to release these files at the correct time.
It just works™ ¯\_(ツ)_/¯
Old Qualcomn devices have their own special QC table of DTB to
store device trees. Since patching fstab is now mandatory on Android 10,
and for older devices all early mount devices have to be included into
the fstab in DTBs, patching QCDT is crucial for rooting Android 10
on legacy devices.
Close#1876 (Thanks for getting me aware of this issue!)
Directly read from urandom instead of using std::random_device.
libc++ will use iostream under-the-hood, which brings significant
binary size increase that is not welcomed, especially in magiskinit.
We used to construct /sbin tmpfs overlay in early-init stage after
SELinux is properly initialized. However the way it is implemented
(forking daemon from magiskinit with complicated file waiting triggers)
is extremely complicated and error prone.
This commit moves the construction of the sbin overlay to pre-init
stage. The catch is that since SELinux is not present at that point,
proper selabel has to be reconstructed afterwards. Some additional
SEPolicy rules are added to make sure init can access magisk binaries,
and the secontext relabeling task is assigned to the main Magisk daemon.
Samsung does not like running cmd before system services are started.
Instead of failing, it will enter an infinite wait on binder.
Move APK installation to boot complete to make sure pm can be run
without blocking process.
Shut down any UID matching process and resume if it turns out not to
be our target. Since we will record every single process we have ever
paused, this means that the same process will not be paused erroneously
for another time.
This is an optimization to hijack the app as soon as possible.
Before switching to the new MagiskHide implementation (APK inotify),
logcat parsing provides us lots of information to target a process.
We were targeting components so that apps with multi-processes
can still be hidden properly.
After switching to the new implementation, our granularity is limited
to the UID of the process. This is especially dangerous since Android
allow apps signed with the same signature to share UIDs, and many system
apps utilize this for elevated permissions for some services.
This commit introduces process name matching. We could not blanketly
target an UID, so the workaround is to verify its process name before
unmounting.
The tricky thing is that any app developer is allowed to name the
process of its component to whatever they want; there is no 'one
rule to catch them all' to target a specific package. As a result,
Magisk Manager is updated to scan through all components of all apps,
and show different processes of the same app, each as a separate
hide target in the list.
The hide target database also has to be updated accordingly.
Each hide target is now a <package name, process name> pair. The
magiskhide CLI and Magisk Manager is updated to support this new
target format.
Most Chinese devices (and supposedly Galaxy S10) running Android Pie
is using system-as-root without A/B partition.
https://source.android.com/devices/bootloader/system-as-root#about-system-as-root
According to the docs above, these devices will have a ramdisk block
with size 0 in their boot images. Since magiskinit can run independently
on system-as-root devices, we simply just create an empty ramdisk with
magiskinit added as init.
Huge thanks to @vvb2060 for the heads up and original PR.
Close#980, close#1102
Since we switched to imageless Magisk, module files are directly
stored in /data. However, /data is mounted with nosuid, which also
prevents SELinux typetransition to work (auto transition from one
domain to another when executing files with specific context).
This could cause serious issues when we are replacing system critical
components (e.g. app_process for Xposed), because most of them
are daemons that run in special process domains.
This commit introduced /data mirror. Using similar mirroring technique
we used for system and vendor, we mount another mirror that mounts
/data without nosuid flag. All module files are then mounted from this
mirror mountpoint instead of directly from /data.
Close#1080
