Usually, the communication between native and the app is done via
sending intents to either broadcast or activity. These communication
channels are for launching root requests dialogs, sending root request
notifications (the toast you see when an app gained root access), and
root request logging.
Sending intents by am (activity manager) usually requires specifying
the component name in the format of <pkg>/<class name>. This means parts
of Magisk Manager cannot be randomized or else the native daemon is
unable to know where to send data to the app.
On modern Android (not sure which API is it introduced), it is possible
to send broadcasts to a package, not a specific component. Which
component will receive the intent depends on the intent filter declared
in AndroidManifest.xml. Since we already have a mechanism in native code
to keep track of the package name of Magisk Manager, this makes it
perfect to pass intents to Magisk Manager that have components being
randomly obfuscated (stub APKs).
There are a few caveats though. Although this broadcasting method works
perfectly fine on AOSP and most systems, there are OEMs out there
shipping ROMs blocking broadcasts unexpectedly. In order to make sure
Magisk works in all kinds of scenarios, we run actual tests every boot
to determine which communication method should be used.
We have 3 methods in total, ordered in preference:
1. Broadcasting to a package
2. Broadcasting to a specific component
3. Starting a specific activity component
Method 3 will always work on any device, but the downside is anytime
a communication happens, Magisk Manager will steal foreground focus
regardless of whether UI is drawn. Method 1 is the only way to support
obfuscated stub APKs. The communication test will test method 1 and 2,
and if Magisk Manager is able to receive the messages, it will then
update the daemon configuration to use whichever is preferable. If none
of the broadcasts can be delivered, then the fallback method 3 will be
used.
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!)
The state of ROM A/B OTA addon.d-v2 support is an inconsistent mess currently:
- LineageOS builds userdebug with permissive update_engine domain, OmniROM builds userdebug with a more restricted update_engine domain, and CarbonROM builds user with a hybrid closer to Omni's
- addon.d-v2 scripts cannot function to the full extent they should when there is a more restricted update_engine domain sepolicy in place, which is likely why Lineage made update_engine completely permissive
Evidence for the above:
- many addon.d-v2 scripts only work (or fully work) on Lineage, see below
- Magisk's addon.d-v2 script would work on Lineage without issue, but would work on Carbon and Omni only if further allow rules were added for basic things like "file read" and "dir search" suggesting these ROMs' addon.d-v2 is severely limited
- Omni includes a /system/addon.d/69-gapps.sh script with the ROM itself (despite shipping without GApps), and with Magisk's more permissive sepolicy and no GApps installed it will remove important ROM files during OTA, resulting in a bootloop; the issue with shipping this script was therefore masked by Omni's overly restrictive update_engine sepolicy not allowing the script to function as intended
The solution:
- guarantee a consistent addon.d-v2 experience for users across ROMs when rooted with Magisk by making update_engine permissive as Lineage has
- hopefully ROMs can work together to come up with something standard for unrooted addon.d-v2 function
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.
- while many newer devices cannot allow / (system partition) to be mounted rw due to compressed fs (e.g. erofs) or logical partitions, it should remain possible to alter rootfs files/directories on those that previously allowed it
The way how logical partition, or "Logical Resizable Android Partitions"
as they say in AOSP source code, is setup makes it impossible to early
mount the partitions from the shared super partition with just
a few lines of code; in fact, AOSP has a whole "fs_mgr" folder which
consist of multiple complex libraries, with 15K lines of code just
to deal with the device mapper shenanigans.
In order to keep the already overly complicated MagiskInit more
managable, I chose NOT to go the route of including fs_mgr directly
into MagiskInit. Luckily, starting from Android Q, Google decided to
split init startup into 3 stages, with the first stage doing _only_
early mount. This is great news, because we can simply let the stock
init do its own thing for us, and we intercept the bootup sequence.
So the workflow can be visualized roughly below:
Magisk First Stage --> First Stage Mount --> Magisk Second Stage --+
(MagiskInit) (Original Init) (MagiskInit) +
+
+
...Rest of the boot... <-- Second Stage <-- Selinux Setup <--+
(__________________ Original Init ____________________)
The catch here is that after doing all the first stage mounting, /init
will pivot /system as root directory (/), leaving us impossible to
regain control after we hand it over. So the solution here is to patch
fstab in /first_stage_ramdisk on-the-fly to redirect /system to
/system_root, making the original init do all the hard work for
us and mount required early mount partitions, but skips the step of
switching root directory. It will also conveniently hand over execution
back to MagiskInit, which we will reuse the routine for patching
root directory in normal system-as-root situations.
- Magisk "dirty" flashes would remove the /overlay directory which might have been put there by a custom kernel or other mod
- this is a leftover from when Magisk itself used /overlay for placing init.magisk.rc, so just remove this file specifically and leave the rest intact
The current system-as-root magiskinit implementation (converting
root directory in system partition to legacy rootfs setup) is now
considered as backwards compatible only.
The new implementation that is hide and Android Q friendly is coming soon.
- when input image had a compressed ramdisk magiskboot had no way to force the repack with the uncompressed ramdisk.cpio since it does not formally recognize cpio as its own format, so add a switch to support forcing repacking to any possible ramdisk format regardless of input image
- when input image had a different supported format (e.g. gzip) magiskboot would not accept a manually compressed ramdisk or kernel in an unsupported format (e.g. lzop) despite being able to recognize it, so instead would double compress using whatever the input format was, breaking the image with, in effect, a ramdisk.cpio.lzo.gz
In commit 8d4c407, native Magisk always launches an activity for
communicating with Magisk Manager. While this works extremely well,
since it also workaround stupid OEMs that blocks broadcasts, it has a
problem: launching an activity will claim the focus of the device,
which could be super annoying in some circumstances.
This commit adds a new feature to run a broadcast test on boot complete.
If Magisk Manager successfully receives the broadcast, it will toggle
a setting in magiskd so all future su loggings and notifies will always
use broadcasts instead of launching activities.
Fix#1412
For devices come with two /data mount points, magisk will bind the one in tmpfs and failed to load modules since this partition is empty.
Signed-off-by: Shaka Huang <shakalaca@gmail.com>
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.
Some stupid Samsung ROMs will spawn multiple zygote daemons. Since we
switched to ptrace based process monitoring, we have to know all zygote
processes to trace. This is an attempt to fix this issue.
Close#1272
Since Android Q does not allow launching activities from the background
(Services/BroadcastReceivers) and our native process is root, directly
launch activities and use it for communication between native and app.
The target activity is not exported, so non-root apps cannot send an
intent to fool Magisk Manager. This is as safe as the previous
implementation, which uses protected system broadcasts.
This also workaround broadcast limitations in many ROMs (especially
in Chinese ROMs) which blocks the su request dialog if the app is
frozen/force stopped by the system.
Close#1326
The root nodes are /system and /vendor. Adding new files into these
directories, although works on some devices, mostly bootloops on many
devices out there. So don't allow it, which also makes the whole magic
mounting logic much easier and extensible.
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.
Forseeing the future that more and more A only system-as-root devices
would have similar bootloader behavior as the latest Samsung devices
(that is, no ramdisk will be loaded into memory when booting from
the boot partition), a solution/workaround has to be made when Magisk
is installed to the recovery partition, making custom recoveries
unable to co-exist with Magisk.
This commit allows magiskinit to read input device events from the
kernel to detect when a user holds volume key up to toggle whether
system-as-root mode is enabled. When system-as-root mode is disabled,
magiskinit will boot with ramdisk instead of cloning rootfs from system,
which in this case will boot to the recovery.
Some devices (mainly new Samsung phones we're talking here...) using
A only system-as-root refuse to load ramdisk when booted with boot
no matter what we do. With many A only system-as-root devices, even
though their boot image is kernel only, we can still be able to add
a ramdisk section into the image and force the kernel to use it as
rootfs. However the bootloader on devices like the S10 simply does
not load anything within boot image into memory other than the kernel.
This gives as the only option is to install Magisk on the recovery
partition. This commits adds proper support for these kind of scenarios.
It seems that even adding this to the list doesn't 100% works on all
devices out there, and some even reported crashes on several Google
services. Disable it for now and do further investigations in the future.
95%+ of existing modules enables auto mount (obviously).
Switching auto mount to opt-out makes more sense than opt-in as
in previous module format. The file 'auto_mount' will be ignored, and
the file 'skip_mount' will be checked to toggle the mounting behavior.
After scanning through the current Magisk Module Repo modules, no
modules are using custom bind mounting; all modules with auto mount
disabled have empty system folder, which means this change will not
affect any existing module.
It seems both Android cancers, Samsung and Huawei devices, don't
like preloading sepolicy. For a temporary solution now is to limit
the sepolicy loading to Android Q only.
Of course, the cancer of Android, Huawei, has to do some f**king weird
modifications to the Linux kernel. Its kernel only accepts 1 single
policy load in its lifetime, a second load will result in ENOMEM error.
Since Huawei devices always use their own stupid ramdisk setup and not
system-as-root, not loading sepolicy is not a concern (for now).
Android Q init assumes rootfs to always be on EXT4 images, thus
never runs restorecon on the whole root directory. This is an issue
because some folders in rootfs were set with special selabels in
the system partition, but when copying over to initramfs by magiskinit,
these labels will not be preserved.
So the solution is to relabel the files in rootfs with the original
context right? Yes, but rootfs does not allow security xattr to be set
on files before the kernel SELinux initializes with genfs_contexts.
We have to load our sepolicy to the kernel before we clone the root
directory from system partition, which we will also restore the selabel
in the meantime.
Unfortunately this means that for each reboot, the exact same policy
will be loaded to the kernel twice: once in magiskinit so we can label
rootfs properly, and once by the original init, which is part of the
boot procedure. There is no easy way to prevent init from loading
sepolicy, as init will refuse to continue if policy loading has failed.
Allow zygote to execute other programs (such as dex2oat).
This fixes the bug that cause ART framework boot images failed to load
and result to extremely serious performance degradation.
Fix#1195
vector<bool> uses bitsets, so we actually only use 12k memory to
store all 3 possible PID info tables. PID checkup will be now become
O(1) instead of O(logn).
P.S. The reason why we don't use unordered_map is because including it
will result in significant binary size increase (might be due to the
complex hash table STL implementation? I really don't know).
