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* HTC U11 Oreo is using keymaster3 FDE encryption which requires
the new services:
1- /system/bin/hwservicemanager
2- /vendor/bin/hw/android.hardware.keymaster@3.0-service
3- /vendor/bin/qseecomd (instead of /system/bin/qseecomd)
So in addition to /vendor/lib and /vendor/lib64 also
symlink /system/vendor/bin to /vendor/bin.
* vold_decrypt services now have separate prefixes:
1- 'sys_' referring to /system/bin
2- 'ven_' referring to /vendor/bin
* The additional (hwservicemanager, keymaster-3-0) and modified
(qseecomd) .rc files have been updated in the vold_decrypt
directory.
Comments were added directly in the .rc files, please check
them.
* /etc/recovery.fstab needs to be temporarily moved since
vold will use it if it finds the '/sbin/recovery' file
(refer to fs_mgr for the fstab load code https://goo.gl/8KaZyf).
Since fs_mgr cannot parse TWRP style fstab, we 'hide' it
and attempt to create a symlink to /fstab.{ro.hardware}.
Also remove shell dependencies, code cleanup, new error codes:
* Critical sections of vold_decrypt should not rely on the external
shell (and the available binaries) provided by TWFunc::Exec_Cmd.
Doing so may lead to failures resulting from different shell
provided binaries not working properly, especially since busybox
can be inconsistent across different trees.
In particular the following functions have been changed:
* run_vdc() no longer uses daisy chained commands, instead
it now forks and executes vdc directly including a 30 second
built in timeout.
* Symlink_Firmware_Files() no longer relies on the shell 'find'
command to retrieve the list of firmware/vendor files and instead
uses a built in function, Find_Firmware_Files(), which traverses
the system partition to retrieve the list of files.
* The code has also been cleaned up a little for better consistency,
and vold_decrypt will now return various error codes for the
different failures, as defined in vold_decrypt.h, which allows the
gui_msg to be moved back to partitionmanager.cpp.
Notes regarding pre Android 8.0 builds:
* Service names in .rc files cannot exceed 16 characters (including
the prepended 'sys_' or 'ven_') in Android 7.1 and below, so a
service name such as 'sys_hwservicemanager' is out of the question
for 7.1 and below.
* hwservicemanager will check ACLs on 'hwservicemanager' and 'ITokenManager'
if they are even allowed to run, otherwise the interfaces will fail.
The policies have only been introduced in 8.0, and although it is possible
to manually add them to the 7.1 policies it's not recommended.
* Therefore the best course of action is to build in 8.0.
* SIDE NOTE: On the HTC U11 we are actually using omni-7.1 with some changes
in the device tree to support both Nougat and Oreo decryption, please
refer to:
1- https://gerrit.twrp.me/c/2756/ for the necessary sepolicy and
BoardConfig changes.
2- The Android.mk file for vold_decrypt was modified to truncate
greater than 16 character service names (as mentioned therein)
Other changes:
* TW_CRYPTO_SYSTEM_VOLD_DISABLE_TIMEOUT is now deprecated due to built-
in fork and timeout.
* Output_dmesg_to_recovery_log() is also deprecated so upon a failed
decryption the recovery.log will no longer append it, instead you can
just use 'adb shell dmesg' to check it. Nonetheless if a true debug
build is needed use the original TW_CRYPTO_SYSTEM_VOLD_DEBUG flag as
outlined in the original commit message (see below).
Usage info:
This is an update to the initial vold_decrypt, for more info refer to
https://github.com/omnirom/android_bootable_recovery/commit/71c6c50d0da1f32dd18a749797e88de2358c5ba1
Change-Id: Id7129d125ae7f5dcba0779489825add718022ba3
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If TWRP crypto fails to decrypt partition, mount the system
partition and use system's own vold to attempt decryption.
This provides a fallback for proprietary OEM encryption as well as
encryption methods which TWRP hasn't been updated for.
Requirements in device tree:
* fstab.{ro.hardware} in device/recovery/root
The fstab does not need to be complete, but it does need the
data partition and the encryption entries.
* 'TW_CRYPTO_USE_SYSTEM_VOLD := true' in BoardConfig
or
* 'TW_CRYPTO_USE_SYSTEM_VOLD := <list of services>'
Notes:
* Setting the flag to 'true' will just use system's vdc+vold
or
* Setting the flag with additional services, will also start them
prior to attempting vdc+vold decryption, eg: for qualcomm based
devices you usually need 'TW_CRYPTO_USE_SYSTEM_VOLD := qseecomd'
* For each service listed an additional import will be automatically
added to the vold_decrypt.rc file in the form of
init.recovery.vold_decrypt.{service}.rc
You will need to add any not already existing .rc files in
your device/recovery/root folder.
* The service names specified in the vold_decrypt.{service}.rc files
have to be named 'sys_{service}'
eg: 'service sys_qseecomd /system/bin/qseecomd'
* Any service already existing in TWRP as {service} or sbin{service} will
be stopped and restarted as needed.
* You can override the default init.recovery.vold_decrypt.rc file(s)
by placing same named ones in your device/recovery/root folder.
If you do, you'll need to manually add the needed imports.
* If /vendor and /firmware folders are temporarily moved and symlinked
to the folders and files in the system partition, the properties
'vold_decrypt.symlinked_vendor' and 'vold_decrypt.symlinked_firmware'
will be set to 1.
This allows for additional control in the .rc files for any extra
actions (symlinks, cp files, etc) that may be needed for decryption
by using: on property:vold_decrypt.symlinked_vendor=1 and/or
on property:vold_decrypt.symlinked_firmware=1 triggers.
Debug mode: 'TW_CRYPTO_SYSTEM_VOLD_DEBUG := true' in BoardConfig
* Specifying this flag, will enable strace on init and vdc, which will
create separate log files in /tmp for every process created, allowing
for detailed analysis of which services and files are being accessed.
* Note that enabling strace will expose the password in the logs!!
* You need to manually add strace to your build.
Thanks to @Captain_Throwback for co-authoring and testing.
Tested successfully on HTC devices:
M8 (KK through MM), M9 (MM and N), A9 (N), 10 (N), Bolt (N),
Desire 626s (MM), U Ultra (N)
HTC One X9 (MTK device)
And by Nikolay Jeliazkov on: Xiaomi Mi Max
Change-Id: I4d22ab55baf6a2a50adde2e4c1c510c142714227
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