Commit 77df7f207d / http://aosp/1217657 ("Refactor to use
EncryptionPolicy everywhere we used to use raw_ref") unintentionally
made fscrypt_initialize_systemwide_keys() start specifying keepOld=true
(via default parameter value) when retrieving the system DE key, and
likewise for read_or_create_volkey() and volume keys.
As a result, if the associated Keymaster key needs to be upgraded, the
upgraded key blob gets written to "keymaster_key_blob_upgraded", but it
doesn't replace the original "keymaster_key_blob", nor is the original
key deleted from Keymaster. This happens at every boot, eventually
resulting in the RPMB partition in Keymaster becoming full.
Only the metadata encryption key ever needs keepOld=true, since it's the
only key that isn't stored in /data, and the purpose of keepOld=true is
to allow a key that isn't stored in /data to be committed or rolled back
when a userdata checkpoint is committed or rolled back.
So, fix this bug by removing the default value of keepOld, and
specifying false everywhere except the metadata encryption key.
Note that when an affected device gets this fix, it will finally upgrade
its system DE key correctly. However, this fix doesn't free up space in
Keymaster that was consumed by this bug.
Test: On bramble:
- Flashed rvc-d1-dev build, with wiping userdata
- Flashed a newer build, without wiping userdata
- Log expectedly shows key upgrades:
$ adb logcat | grep 'Upgrading key'
D vold : Upgrading key: /metadata/vold/metadata_encryption/key
D vold : Upgrading key: /data/unencrypted/key
D vold : Upgrading key: /data/misc/vold/user_keys/de/0
D vold : Upgrading key: /data/misc/vold/user_keys/ce/0/current
- Rebooted
- Log unexpectedly shows the system DE key being upgraded again:
$ adb logcat | grep 'Upgrading key'
D vold : Upgrading key: /data/unencrypted/key
- "keymaster_key_blob_upgraded" unexpectedly still exists:
$ adb shell find /data /metadata -name keymaster_key_blob_upgraded
/data/unencrypted/key/keymaster_key_blob_upgraded
- Applied this fix and flashed, without wiping userdata
- Log shows system DE key being upgraded (expected because due to the
bug, the upgraded key didn't replace the original one before)
$ adb logcat | grep 'Upgrading key'
D vold : Upgrading key: /data/unencrypted/key
- "keymaster_key_blob_upgraded" expectedly no longer exists
$ adb shell find /data /metadata -name keymaster_key_blob_upgraded
- Rebooted
- Log expectedly doesn't show any more key upgrades
$ adb logcat | grep 'Upgrading key'
Bug: 171944521
Bug: 172019387
Change-Id: I42d3f5fbe32cb2ec229f4b614cfb271412a3ed29
c493903732