fix(device-approval-persistence): [PM-9112] Device Approval Persistence (#13680)

* feat(device-approval-persistence): [PM-9112] Device Approval Persistence - Added in view cache data needed to persist the approval process. Clears after 2 minutes.

libs/auth/src/common/services/auth-request/default-login-via-auth-request-cache.service.ts

@@ -0,0 +1,88 @@
+import { inject, Injectable, WritableSignal } from "@angular/core";
+
+import { ViewCacheService } from "@bitwarden/angular/platform/abstractions/view-cache.service";
+import { AuthRequest } from "@bitwarden/common/auth/models/request/auth.request";
+import { AuthRequestResponse } from "@bitwarden/common/auth/models/response/auth-request.response";
+import { LoginViaAuthRequestView } from "@bitwarden/common/auth/models/view/login-via-auth-request.view";
+import { FeatureFlag } from "@bitwarden/common/enums/feature-flag.enum";
+import { ConfigService } from "@bitwarden/common/platform/abstractions/config/config.service";
+import { Utils } from "@bitwarden/common/platform/misc/utils";
+
+const LOGIN_VIA_AUTH_CACHE_KEY = "login-via-auth-request-form-cache";
+
+/**
+ * This is a cache service used for the login via auth request component.
+ *
+ * There is sensitive information stored temporarily here. Cache will be cleared
+ * after 2 minutes.
+ */
+@Injectable()
+export class LoginViaAuthRequestCacheService {
+  private viewCacheService: ViewCacheService = inject(ViewCacheService);
+  private configService: ConfigService = inject(ConfigService);
+
+  /** True when the `PM9112_DeviceApproval` flag is enabled */
+  private featureEnabled: boolean = false;
+
+  private defaultLoginViaAuthRequestCache: WritableSignal<LoginViaAuthRequestView | null> =
+    this.viewCacheService.signal<LoginViaAuthRequestView | null>({
+      key: LOGIN_VIA_AUTH_CACHE_KEY,
+      initialValue: null,
+      deserializer: LoginViaAuthRequestView.fromJSON,
+    });
+
+  constructor() {}
+
+  /**
+   * Must be called once before interacting with the cached data, otherwise methods will be noop.
+   */
+  async init() {
+    this.featureEnabled = await this.configService.getFeatureFlag(
+      FeatureFlag.PM9112_DeviceApprovalPersistence,
+    );
+  }
+
+  /**
+   * Update the cache with the new LoginView.
+   */
+  cacheLoginView(
+    authRequest: AuthRequest,
+    authRequestResponse: AuthRequestResponse,
+    fingerprintPhrase: string,
+    keys: { privateKey: Uint8Array | undefined; publicKey: Uint8Array | undefined },
+  ): void {
+    if (!this.featureEnabled) {
+      return;
+    }
+
+    // When the keys get stored they should be converted to a B64 string to ensure
+    // data can be properly formed when json-ified. If not done, they are not stored properly and
+    // will not be parsable by the cryptography library after coming out of storage.
+    this.defaultLoginViaAuthRequestCache.set({
+      authRequest,
+      authRequestResponse,
+      fingerprintPhrase,
+      privateKey: keys.privateKey ? Utils.fromBufferToB64(keys.privateKey.buffer) : undefined,
+      publicKey: keys.publicKey ? Utils.fromBufferToB64(keys.publicKey.buffer) : undefined,
+    } as LoginViaAuthRequestView);
+  }
+
+  clearCacheLoginView(): void {
+    if (!this.featureEnabled) {
+      return;
+    }
+
+    this.defaultLoginViaAuthRequestCache.set(null);
+  }
+
+  /**
+   * Returns the cached LoginViaAuthRequestView when available.
+   */
+  getCachedLoginViaAuthRequestView(): LoginViaAuthRequestView | null {
+    if (!this.featureEnabled) {
+      return null;
+    }
+
+    return this.defaultLoginViaAuthRequestCache();
+  }
+}