Add internal support for regionalized OIDC token exchange (BYO-CIAM)

ExchangeTokenRequestTests.swift

@@ -0,0 +1,154 @@
+// Copyright 2023 Google LLC
+//
+// 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 Foundation
+import XCTest
+
+@testable import FirebaseAuth
+import FirebaseCore
+
+/// Tests for `ExchangeTokenRequest`
+@available(iOS 13, *)
+class ExchangeTokenRequestTests: XCTestCase {
+  // MARK: - Constants for Testing
+
+  let kAPIKey = "test-api-key"
+  let kProjectID = "test-project-id"
+  let kLocation = "us-east1"
+  let kTenantID = "test-tenant-id-123"
+  let kIdToken = "a-very-long-and-secure-oidc-token-string"
+  let kIdpConfigId = "oidc.my-test-provider"
+
+  let kProductionHost = "identityplatform.googleapis.com"
+  let kStagingHost = "staging-identityplatform.sandbox.googleapis.com"
+
+  // MARK: - Test Cases
+
+  /// Tests that the production URL is correctly formed for a specific region.
+  func testProductionURLIsCorrectlyConstructed() {
+    let (auth, app) = createTestAuthInstance(
+      projectID: kProjectID,
+      location: kLocation,
+      tenantId: kTenantID
+    )
+
+    let request = ExchangeTokenRequest(
+      idToken: kIdToken,
+      idpConfigID: kIdpConfigId,
+      config: auth.requestConfiguration,
+      useStaging: false
+    )
+
+    let expectedHost = "\(kLocation)-\(kProductionHost)"
+    let expectedURL = "https://\(expectedHost)/v2beta/projects/\(kProjectID)" +
+      "/locations/\(kLocation)/tenants/\(kTenantID)/idpConfigs/\(kIdpConfigId):exchangeOidcToken?key=\(kAPIKey)"
+
+    XCTAssertEqual(request.requestURL().absoluteString, expectedURL)
+  }
+
+  /// Tests that the production URL is correctly formed for the "prod-global" location.
+  func testProductionURLIsCorrectlyConstructedForGlobalLocation() {
+    let (auth, app) = createTestAuthInstance(
+      projectID: kProjectID,
+      location: "prod-global",
+      tenantId: kTenantID
+    )
+    _ = app
+
+    let request = ExchangeTokenRequest(
+      idToken: kIdToken,
+      idpConfigID: kIdpConfigId,
+      config: auth.requestConfiguration,
+      useStaging: false
+    )
+
+    let expectedHost = kProductionHost
+    let expectedURL = "https://\(expectedHost)/v2beta/projects/\(kProjectID)" +
+      "/locations/global/tenants/\(kTenantID)/idpConfigs/\(kIdpConfigId):exchangeOidcToken?key=\(kAPIKey)"
+
+    XCTAssertEqual(request.requestURL().absoluteString, expectedURL)
+  }
+
+  /// Tests that the staging URL is correctly formed.
+  func testStagingURLIsCorrectlyConstructed() {
+    let (auth, app) = createTestAuthInstance(
+      projectID: kProjectID,
+      location: kLocation,
+      tenantId: kTenantID
+    )
+    _ = app
+
+    let request = ExchangeTokenRequest(
+      idToken: kIdToken,
+      idpConfigID: kIdpConfigId,
+      config: auth.requestConfiguration,
+      useStaging: true
+    )
+
+    let expectedHost = "\(kLocation)-\(kStagingHost)"
+    let expectedURL = "https://\(expectedHost)/v2beta/projects/\(kProjectID)" +
+      "/locations/\(kLocation)/tenants/\(kTenantID)/idpConfigs/\(kIdpConfigId):exchangeOidcToken?key=\(kAPIKey)"
+
+    XCTAssertEqual(request.requestURL().absoluteString, expectedURL)
+  }
+
+  /// Tests that the unencoded HTTP body contains the correct id_token.
+  func testUnencodedHTTPBodyIsCorrect() {
+    let (auth, app) = createTestAuthInstance(
+      projectID: kProjectID,
+      location: kLocation,
+      tenantId: kTenantID
+    )
+    _ = app
+
+    let request = ExchangeTokenRequest(
+      idToken: kIdToken,
+      idpConfigID: kIdpConfigId,
+      config: auth.requestConfiguration
+    )
+
+    let body = request.unencodedHTTPRequestBody
+    XCTAssertNotNil(body)
+    XCTAssertEqual(body?.count, 1)
+    XCTAssertEqual(body?["id_token"] as? String, kIdToken)
+  }
+
+  // MARK: - Helper Function
+
+  /// Creates a test FirebaseApp and Auth instance with specified configurations.
+  private func createTestAuthInstance(projectID: String?, location: String?,
+                                      tenantId: String?) -> (auth: Auth, app: FirebaseApp) {
+    let appName = "TestApp-\(UUID().uuidString)"
+    let options = FirebaseOptions(
+      googleAppID: "1:1234567890:ios:abcdef123456",
+      gcmSenderID: "1234567890"
+    )
+    options.apiKey = kAPIKey
+    if let projectID = projectID {
+      options.projectID = projectID
+    }
+
+    if FirebaseApp.app(name: appName) != nil {
+      FirebaseApp.app(name: appName)?.delete { _ in }
+    }
+    let app = FirebaseApp(instanceWithName: appName, options: options)
+
+    let auth = Auth(app: app)
+    auth.app = app
+    auth.requestConfiguration.location = location
+    auth.requestConfiguration.tenantId = tenantId
+
+    return (auth, app)
+  }
+}

FirebaseAuth/Sources/Swift/Auth/Auth.swift

@@ -18,6 +18,7 @@ import FirebaseAppCheckInterop
 import FirebaseAuthInterop
 import FirebaseCore
 import FirebaseCoreExtension
+import FirebaseCoreInternal
 #if COCOAPODS
   internal import GoogleUtilities
 #else
@@ -83,48 +84,74 @@ extension Auth: AuthInterop {
   public func getToken(forcingRefresh forceRefresh: Bool,
                        completion callback: @escaping (String?, Error?) -> Void) {
     kAuthGlobalWorkQueue.async { [weak self] in
-      if let strongSelf = self {
-        // Enable token auto-refresh if not already enabled.
-        if !strongSelf.autoRefreshTokens {
-          AuthLog.logInfo(code: "I-AUT000002", message: "Token auto-refresh enabled.")
-          strongSelf.autoRefreshTokens = true
-          strongSelf.scheduleAutoTokenRefresh()
-
-          #if os(iOS) || os(tvOS) // TODO(ObjC): Is a similar mechanism needed on macOS?
-            strongSelf.applicationDidBecomeActiveObserver =
-              NotificationCenter.default.addObserver(
-                forName: UIApplication.didBecomeActiveNotification,
-                object: nil, queue: nil
-              ) { notification in
-                if let strongSelf = self {
-                  strongSelf.isAppInBackground = false
-                  if !strongSelf.autoRefreshScheduled {
-                    strongSelf.scheduleAutoTokenRefresh()
-                  }
-                }
-              }
-            strongSelf.applicationDidEnterBackgroundObserver =
-              NotificationCenter.default.addObserver(
-                forName: UIApplication.didEnterBackgroundNotification,
-                object: nil, queue: nil
-              ) { notification in
-                if let strongSelf = self {
-                  strongSelf.isAppInBackground = true
-                }
-              }
-          #endif
+      guard let self else {
+        DispatchQueue.main.async { callback(nil, nil) }
+        return
+      }
+      /// Before checking for a standard user, check if we are in a token-only session established
+      /// by a successful exchangeToken call.
+      let rGCIPToken = self.rGCIPFirebaseTokenLock.withLock { $0 }
+
+      if let token = rGCIPToken {
+        /// Logic for tokens obtained via exchangeToken (R-GCIP mode)
+        if token.expirationDate < Date() {
+          /// Token expired
+          let error = AuthErrorUtils
+            .userTokenExpiredError(
+              message: "The firebase access token obtained via exchangeToken() has expired."
+            )
+          Auth.wrapMainAsync(callback: callback, with: .failure(error))
+        } else if forceRefresh {
+          /// Token is not expired, but forceRefresh was requested which is currently unsupported
+          let error = AuthErrorUtils
+            .operationNotAllowedError(
+              message: "forceRefresh is not supported for firebase access tokens obtained via exchangeToken()."
+            )
+          Auth.wrapMainAsync(callback: callback, with: .failure(error))
+        } else {
+          /// The token is valid and not expired.
+          Auth.wrapMainAsync(callback: callback, with: .success(token.token))
         }
+        /// Exit here as this path is for rGCIPFirebaseToken only.
+        return
       }
-      // Call back with 'nil' if there is no current user.
-      guard let strongSelf = self, let currentUser = strongSelf._currentUser else {
+      /// Fallback to standard `currentUser` logic if not in token-only mode.
+      if !self.autoRefreshTokens {
+        AuthLog.logInfo(code: "I-AUT000002", message: "Token auto-refresh enabled.")
+        self.autoRefreshTokens = true
+        self.scheduleAutoTokenRefresh()
+
+        #if os(iOS) || os(tvOS)
+          self.applicationDidBecomeActiveObserver =
+            NotificationCenter.default.addObserver(
+              forName: UIApplication.didBecomeActiveNotification,
+              object: nil,
+              queue: nil
+            ) { [weak self] _ in
+              guard let self = self, !self.isAppInBackground,
+                    !self.autoRefreshScheduled else { return }
+              self.scheduleAutoTokenRefresh()
+            }
+          self.applicationDidEnterBackgroundObserver =
+            NotificationCenter.default.addObserver(
+              forName: UIApplication.didEnterBackgroundNotification,
+              object: nil,
+              queue: nil
+            ) { [weak self] _ in
+              self?.isAppInBackground = true
+            }
+        #endif
+      }
+
+      guard let currentUser = self._currentUser else {
         DispatchQueue.main.async {
           callback(nil, nil)
         }
         return
       }
       // Call back with current user token.
       currentUser
-        .internalGetToken(forceRefresh: forceRefresh, backend: strongSelf.backend) { token, error in
+        .internalGetToken(forceRefresh: forceRefresh, backend: self.backend) { token, error in
           DispatchQueue.main.async {
             callback(token, error)
           }
@@ -2265,6 +2292,11 @@ extension Auth: AuthInterop {
     return { result in
       switch result {
       case let .success(authResult):
+        /// When a standard user successfully signs in, any existing token-only session must be
+        /// invalidated to prevent a conflicting auth state.
+        /// Clear any R-GCIP session state when a standard user signs in. This ensures we exit
+        /// Token-Only Mode.
+        self.rGCIPFirebaseTokenLock.withLock { $0 = nil }
         do {
           try self.updateCurrentUser(authResult.user, byForce: false, savingToDisk: true)
           Auth.wrapMainAsync(callback: callback, with: .success(authResult))
@@ -2428,9 +2460,20 @@ extension Auth: AuthInterop {
   ///
   /// Mutations should occur within a @synchronized(self) context.
   private var listenerHandles: NSMutableArray = []
+
+  // R-GCIP Token-Only Session State
+
+  /// The session token obtained from a successful `exchangeToken` call, protected by a lock.
+  ///
+  /// This property is used to support a "token-only" authentication mode for Regionalized
+  /// GCIP, where no `User` object is created. It is mutually exclusive with `_currentUser`.
+  /// If the wrapped value is non-nil, the `AuthInterop` layer will use it for token generation
+  /// instead of relying on a `currentUser`.
+  private let rGCIPFirebaseTokenLock = FIRAllocatedUnfairLock<FirebaseToken?>(initialState: nil)
 }
 
-/// Regionalized auth
+// MARK: - Regionalized auth
+
 @available(iOS 13, tvOS 13, macOS 10.15, macCatalyst 13, watchOS 7, *)
 public extension Auth {
   /// Gets the Auth object for a `FirebaseApp` configured for a specific Regional Google Cloud
@@ -2457,10 +2500,75 @@ public extension Auth {
     ///
     /// - Parameters:
     ///   - tenantId: The ID of the tenant.
-    ///   - location: The location of the tenant. Defaults to "prod-global".
-    public init(tenantId: String, location: String = "prod-global") {
+    ///   - location: The location of the tenant. Defaults to "global".
+    public init(tenantId: String, location: String = "global") {
       self.location = location
       self.tenantId = tenantId
     }
   }
+
+  /// Exchanges a third-party OIDC ID token for a Firebase ID token.
+  ///
+  /// This method is used for Bring Your Own CIAM (BYO-CIAM) in Regionalized GCIP (R-GCIP),
+  /// where the `Auth` instance must be configured with a `TenantConfig`, including `location`
+  /// and `tenantId`,  typically by using `Auth.auth(app:tenantConfig:)`.
+  ///
+  /// Unlike standard sign-in methods, this flow *does not*  create or update a `User`object  and
+  /// *does not* set `CurrentUser`  on the `Auth` instance. It only returns a Firebase token.
+  ///
+  /// - Parameters:
+  ///   - oidcToken: The OIDC ID token obtained from the third-party identity provider.
+  ///   - idpConfigId: The ID of the Identity Provider configuration within your GCIP tenant
+  ///   - useStaging: A Boolean value indicating whether to use the staging Identity Platform
+  ///     backend. Defaults to `false`.
+  /// - Returns: A `FirebaseToken` containing the Firebase ID token and its expiration date.
+  /// - Throws: An error if the `Auth` instance is not configured for R-GCIP, if the network
+  ///   call fails, or if the token response parsing fails.
+  func exchangeToken(idToken: String, idpConfigId: String,
+                     useStaging: Bool = false) async throws -> FirebaseToken {
+    // Ensure R-GCIP is configured with location and tenant ID
+    guard let _ = requestConfiguration.tenantConfig?.location,
+          let _ = requestConfiguration.tenantConfig?.tenantId
+    else {
+      /// This should never happen in production code, as it indicates a misconfiguration.
+      fatalError("R-GCIP is not configured correctly.")
+    }
+    let request = ExchangeTokenRequest(
+      idToken: idToken,
+      idpConfigID: idpConfigId,
+      config: requestConfiguration,
+      useStaging: useStaging
+    )
+    do {
+      let response = try await backend.call(with: request)
+      let newToken = FirebaseToken(
+        token: response.firebaseToken,
+        expirationDate: response.expirationDate
+      )
+      // Lock and update the token, signing out any current user.
+      rGCIPFirebaseTokenLock.withLock { token in
+        if self._currentUser != nil {
+          try? self.signOut()
+        }
+        token = newToken
+      }
+      return newToken
+    } catch {
+      throw error
+    }
+  }
+}
+
+/// Represents the result of a successful OIDC token exchange, containing a Firebase ID token
+/// and its expiration.
+public struct FirebaseToken: Sendable {
+  /// The Firebase ID token string.
+  public let token: String
+  /// The date at which the Firebase ID token expires.
+  public let expirationDate: Date
+
+  init(token: String, expirationDate: Date) {
+    self.token = token
+    self.expirationDate = expirationDate
+  }
 }