# Permission System 2.0
## Background
This PR migrates the extension permission system to [the new `PermissionController`](https://github.com/MetaMask/snaps-skunkworks/tree/main/packages/controllers/src/permissions).
The original permission system, based on [`rpc-cap`](https://github.com/MetaMask/rpc-cap), introduced [`ZCAP-LD`](https://w3c-ccg.github.io/zcap-ld/)-like permissions to our JSON-RPC stack.
We used it to [implement](https://github.com/MetaMask/metamask-extension/pull/7004) what we called "LoginPerSite" in [version 7.7.0](https://github.com/MetaMask/metamask-extension/releases/tag/v7.7.0) of the extension, which enabled the user to choose which accounts, if any, should be exposed to each dapp.
While that was a worthwhile feature in and of itself, we wanted a permission _system_ in order to enable everything we are going to with Snaps.
Unfortunately, the original permission system was difficult to use, and necessitated the creation of the original `PermissionsController` (note the "s"), which was more or less a wrapper for `rpc-cap`.
With this PR, we shake off the yoke of the original permission system, in favor of the modular, self-contained, ergonomic, and more mature permission system 2.0.
Note that [the `PermissionController` readme](https://github.com/MetaMask/snaps-skunkworks/tree/main/packages/controllers/src/permissions/README.md) explains how the new permission system works.
The `PermissionController` and `SubjectMetadataController` are currently shipped via `@metamask/snap-controllers`. This is a temporary state of affairs, and we'll move them to `@metamask/controllers` once they've landed in prod.
## Changes in Detail
First, the changes in this PR are not as big as they seem. Roughly half of the additions in this PR are fixtures in the test for the new migration (number 68), and a significant portion of the remaining ~2500 lines are due to find-and-replace changes in other test fixtures and UI files.
- The extension `PermissionsController` has been deleted, and completely replaced with the new `PermissionController` from [`@metamask/snap-controllers`](https://www.npmjs.com/package/@metamask/snap-controllers).
- The original `PermissionsController` "domain metadata" functionality is now managed by the new `SubjectMetadataController`, also from [`@metamask/snap-controllers`](https://www.npmjs.com/package/@metamask/snap-controllers).
- The permission activity and history log controller has been renamed `PermissionLogController` and has its own top-level state key, but is otherwise functionally equivalent to the existing implementation.
- Migration number 68 has been added to account for the new state changes.
- The tests in `app/scripts/controllers/permissions` have been migrated from `mocha` to `jest`.
Reviewers should focus their attention on the following files:
- `app/scripts/`
- `metamask-controller.js`
- This is where most of the integration work for the new `PermissionController` occurs.
Some functions that were internal to the original controller were moved here.
- `controllers/permissions/`
- `selectors.js`
- These selectors are for `ControllerMessenger` selector subscriptions. The actual subscriptions occur in `metamask-controller.js`. See the `ControllerMessenger` implementation for details.
- `specifications.js`
- The caveat and permission specifications are required by the new `PermissionController`, and are used to specify the `eth_accounts` permission and its JSON-RPC method implementation.
See the `PermissionController` readme for details.
- `migrations/068.js`
- The new state should be cross-referenced with the controllers that manage it.
The accompanying tests should also be thoroughly reviewed.
Some files may appear new but have just moved and/or been renamed:
- `app/scripts/lib/rpc-method-middleware/handlers/request-accounts.js`
- This was previously implemented in `controllers/permissions/permissionsMethodMiddleware.js`.
- `test/mocks/permissions.js`
- A truncated version of `test/mocks/permission-controller.js`.
Co-authored-by: Mark Stacey <markjstacey@gmail.com>
A new page has been created for viewing assets. This replaces the old
`selectedToken` state, which previously would augment the home page
to show token-specific information.
The new asset page shows the standard token overview as seen previously
on the home page, plus a history filtered to show just transactions
relevant to that token.
The actions that were available in the old token list menu have been
moved to a "Token Options" menu that mirrors the "Account Options"
menu.
The `selectedTokenAddress` state has been removed, as it is no longer
being used for anything.
`getMetaMetricState` has been renamed to `getBackgroundMetaMetricState`
because its sole purpose is extracting data from the background state
to send metrics from the background. It's not really a selector, but
it was convenient for it to use the same selectors the UI uses to
extract background data, so I left it there for now.
A new Redux store has been added to track state related to browser history.
The most recent "overview" page (i.e. the home page or the asset page) is
currently being tracked, so that actions taken from the asset page can return
the user back to the asset page when the action has finished.
This changeset updates the `getOriginOfCurrentTab` selector and the container
for the ConnectedSites page to use `activeTab.origin` instead of parsing the
URL. The `activeTab` URL is parsed in `queryCurrentActiveTab` before the UI is
launched and any subsequent parsing of the URL is unnecessary.
See `queryCurrentActiveTab` in `ui.js:86` [1].
[1]:e7bb0876f5/app/scripts/ui.js (L86-L118)
This change replaces `getRenderablePermissionsDomains` with a new selector `getConnectedDomainsForSelectedAddress` that works better. The data returned from this selector is used to populated the _Connected Sites_ modal, which (as of #8262) didn't use most of the data returned from the old selector.
The old selector only looked at the first address that was exposed, making it not work for anything other than the first account connected to a particular origin.
Niranjana Binoy
Erik Marks
Brad Decker
Whymarrh Whitby
Mark Stacey
Erik Marks