Component on Chrome OS is optional system software downloaded on-demand by any user. A component is stored to encrypted stateful partition and is shared by all users. We locally keeps track of who is using a Component by Chrome Local Preference (https://cs.chromium.org/chromium/src/chrome/browser/component_updater/metadata_table_chromeos.h) in order to properly delete components when no longer used and avoid deleting a component when used.

In Chrome, cryptohome is invoked when a user is deleted (https://cs.chromium.org/chromium/src/chrome/browser/chromeos/login/users/chrome_user_manager_impl.cc?type=cs&g=0&l=1381) via dbus RemoveAsync method to remove the cryptohome of a user.

Cryptohome itself automatically removes user account when disk space is low (https://cs.corp.google.com/chromeos_public/src/platform2/cryptohome/homedirs.cc?l=105). 

Problem: components should also be removed properly when accounts are deleted.

Proposal:
- Add an API in cryptohome - DoesUserExist which takes a sanitized username and return if it exists or not.
- In metadata_table_chromeos.c, switch to call GetSanitizedUsername dbus method call of cryptohome to get hased username.
- Chrome calls DoesUserExist at starting for each santized username that uses a component. If it returns 'not exist', we try to delete the component.


Alternate proposal:
- add an API in CrOSComponentManager - UnloadForUser which takes a sanitized username.
- figure out all places (cryptohome, Chrome, etc.) that deletes account and call this API at the same time.
This approach is less maintenable since we have to enforce all places that delete account to delete components as well. And it's possible that the account was removed during an active session, then component is still mounted and could not be deleted immediately (the preferred proposal cleans up component during system boot).
 

Component on Chrome OS is optional system software downloaded on-demand by any user. A component is stored to encrypted stateful partition and is shared by all users. We locally keeps track of who is using a Component by Chrome Local Preference (https://cs.chromium.org/chromium/src/chrome/browser/component_updater/metadata_table_chromeos.h) in order to properly delete components when no longer being used and avoid deleting a component when being used.

In Chrome, cryptohome is invoked when a user is deleted (https://cs.chromium.org/chromium/src/chrome/browser/chromeos/login/users/chrome_user_manager_impl.cc?type=cs&g=0&l=1381) via dbus RemoveAsync method to remove the cryptohome of a user.

Cryptohome itself automatically removes user account when disk space is low (https://cs.corp.google.com/chromeos_public/src/platform2/cryptohome/homedirs.cc?l=105). 

Problem: components should also be removed properly when accounts are deleted.

Proposal:
- Add an API in cryptohome - DoesUserExist which takes a sanitized username and return if it exists or not.
- In metadata_table_chromeos.c, switch to call GetSanitizedUsername dbus method call of cryptohome to get hased username.
- Chrome calls DoesUserExist at starting for each santized username that uses a component. If it returns 'not exist', we try to delete the component.


Alternate proposal:
- add an API in CrOSComponentManager - UnloadForUser which takes a sanitized username.
- figure out all places (cryptohome, Chrome, etc.) that deletes account and call this API at the same time.
This approach is less maintenable since we have to enforce all places that delete account to delete components as well. And it's possible that the account was removed during an active session, then component is still mounted and could not be deleted immediately (the preferred proposal cleans up component during system boot).
 

Component on Chrome OS is optional system software downloaded on-demand by any user. A component is stored to encrypted stateful partition and is shared by all users. We locally keeps track of who is using a Component by Chrome Local Preference (https://cs.chromium.org/chromium/src/chrome/browser/component_updater/metadata_table_chromeos.h) in order to properly delete components when no longer being used and avoid deleting a component when being used.

In Chrome, cryptohome is invoked when a user is deleted (https://cs.chromium.org/chromium/src/chrome/browser/chromeos/login/users/chrome_user_manager_impl.cc?type=cs&g=0&l=1381) via dbus RemoveAsync method to remove the cryptohome of a user.

Cryptohome itself automatically removes user account when disk space is low (https://cs.corp.google.com/chromeos_public/src/platform2/cryptohome/homedirs.cc?l=105). 

Problem: components should also be removed properly when accounts are deleted.

Proposal:
- Add an API in cryptohome - DoesUserExist which takes a sanitized username and return if it exists or not.
- In metadata_table_chromeos.c, switch to call GetSanitizedUsername dbus method call of cryptohome to get hased username.
- Chrome calls DoesUserExist at starting for each santized username that uses a component. If it returns 'not exist', we try to delete the component.


Alternate proposal:
- add an API in CrOSComponentManager - UnloadForUser which takes a sanitized username.
- figure out all places (cryptohome, Chrome, etc.) that deletes account and call this API at the same time.
This approach is less maintenable since we have to enforce all places that delete account to delete components as well. And it's possible that the account was removed during an active session, then component is still mounted and could not be deleted immediately (the preferred proposal cleans up component during system boot).

Design doc: https://docs.google.com/document/d/1KCJiqK3G9b5W3t25W6vzfqCOK5KOPY2G8bPCcpBlH6U/