Replace the concept of a Widget Security Key with an OIDC state

The security key naming/practice was misguided, so let's call it what it is (a settings key) and abstract away the complexity to a new store.

Fixes https://github.com/vector-im/element-web/issues/15820 while we're here.

src/stores/widgets/WidgetPermissionStore.ts

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2020 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { AsyncStore } from "../AsyncStore";
+import { ActionPayload } from "../../dispatcher/payloads";
+import defaultDispatcher from "../../dispatcher/dispatcher";
+import SettingsStore from "../../settings/SettingsStore";
+import { AsyncStoreWithClient } from "../AsyncStoreWithClient";
+import { IWidget, Widget, WidgetKind } from "matrix-widget-api";
+import { MatrixClientPeg } from "../../MatrixClientPeg";
+import WidgetUtils from "../../utils/WidgetUtils";
+import { SettingLevel } from "../../settings/SettingLevel";
+
+export enum OIDCState {
+    Allowed, // user has set the remembered value as allowed
+    Denied, // user has set the remembered value as disallowed
+    Unknown, // user has not set a remembered value
+}
+
+export class WidgetPermissionStore {
+    private static internalInstance: WidgetPermissionStore;
+
+    private constructor() {
+    }
+
+    public static get instance(): WidgetPermissionStore {
+        if (!WidgetPermissionStore.internalInstance) {
+            WidgetPermissionStore.internalInstance = new WidgetPermissionStore();
+        }
+        return WidgetPermissionStore.internalInstance;
+    }
+
+    // TODO (all functions here): Merge widgetKind with the widget definition
+
+    private packSettingKey(widget: Widget, kind: WidgetKind, roomId?: string): string {
+        let location = roomId;
+        if (kind !== WidgetKind.Room) {
+            location = MatrixClientPeg.get().getUserId();
+        }
+        if (kind === WidgetKind.Modal) {
+            location = '*MODAL*-' + location; // to guarantee differentiation from whatever spawned it
+        }
+        if (!location) {
+            throw new Error("Failed to determine a location to check the widget's OIDC state with");
+        }
+
+        return encodeURIComponent(`${location}::${widget.templateUrl}`);
+    }
+
+    public getOIDCState(widget: Widget, kind: WidgetKind, roomId?: string): OIDCState {
+        const settingsKey = this.packSettingKey(widget, kind, roomId);
+        const settings = SettingsStore.getValue("widgetOpenIDPermissions");
+        if (settings?.deny?.includes(settingsKey)) {
+            return OIDCState.Denied;
+        }
+        if (settings?.allow?.includes(settingsKey)) {
+            return OIDCState.Allowed;
+        }
+        return OIDCState.Unknown;
+    }
+
+    public setOIDCState(widget: Widget, kind: WidgetKind, roomId: string, newState: OIDCState) {
+        const settingsKey = this.packSettingKey(widget, kind, roomId);
+
+        const currentValues = SettingsStore.getValue("widgetOpenIDPermissions");
+        if (!currentValues.allow) currentValues.allow = [];
+        if (!currentValues.deny) currentValues.deny = [];
+
+        if (newState === OIDCState.Allowed) {
+            currentValues.allow.push(settingsKey);
+        } else if (newState === OIDCState.Denied) {
+            currentValues.deny.push(settingsKey);
+        } else {
+            currentValues.allow = currentValues.allow.filter(c => c !== settingsKey);
+            currentValues.deny = currentValues.deny.filter(c => c !== settingsKey);
+        }
+
+        SettingsStore.setValue("widgetOpenIDPermissions", null, SettingLevel.DEVICE, currentValues);
+    }
+}