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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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