本頁面由 Cloud Translation API 翻譯而成。

在 iOS 上透過 Facebook 登入使用者

您可以將 Facebook 登入或 Facebook 有限登入功能整合至應用程式，讓使用者透過 Facebook 帳戶驗證 Identity Platform。本頁說明如何使用 Identity Platform，將「使用 Facebook 登入」功能新增至 iOS 應用程式。

事前準備

將 Firebase 新增至 iOS 專案。
請在 Podfile 中加入下列 Pod：
```
pod 'FirebaseAuth'
```
前往 Google Cloud 控制台的「Identity Providers」頁面。

前往「Identity Providers」(識別資訊提供者) 頁面
按一下「Add A Provider」。
從清單中選取「Facebook」Facebook。
輸入 Facebook 應用程式 ID 和 應用程式密鑰。如果您還沒有 ID 和密鑰，可以前往 Facebook 開發人員頁面取得。
將「Configure Facebook」下列出的 URI 設為 Facebook 應用程式的有效 OAuth 重新導向 URI。如果您在 Identity Platform 中設定了自訂網域，請更新 Facebook 應用程式設定中的重新導向 URI，以便使用自訂網域而非預設網域。例如，將 https://myproject.firebaseapp.com/__/auth/handler 變更為 https://auth.myownpersonaldomain.com/__/auth/handler。
按一下「Authorized Domains」下方的「Add Domain」，即可註冊應用程式的網域。為方便開發，localhost 已預設為啟用。

重要事項： 在 2025 年 4 月 28 日後建立的專案中，Identity Platform 不再預設將 localhost 納入授權網域。Google 強烈建議您不要在正式版專案中使用 localhost。如果您選擇授權 localhost，可以按一下「設定」頁面中的「已授權網域」，然後點選「新增網域」，手動新增該網域。
按一下「設定應用程式」下方的「設定詳細資料」。將程式碼片段複製到應用程式的程式碼中，即可初始化 Identity Platform 用戶端 SDK。
按一下 [儲存]。

實作 Facebook 登入功能

如要使用「傳統」Facebook 登入功能，請完成下列步驟。您也可以使用 Facebook 有限登入功能，詳情請參閱下一節。

按照開發人員說明文件的說明，將 Facebook 登入整合至應用程式。初始化 FBSDKLoginButton 物件時，請設定委派作業，以便接收登入和登出事件。例如：

Swift

let loginButton = FBSDKLoginButton()
loginButton.delegate = self

Objective-C

FBSDKLoginButton *loginButton = [[FBSDKLoginButton alloc] init];
loginButton.delegate = self;

在委派函式中實作 didCompleteWithResult:error:。

Swift

func loginButton(_ loginButton: FBSDKLoginButton!, didCompleteWith result: FBSDKLoginManagerLoginResult!, error: Error!) {
  if let error = error {
    print(error.localizedDescription)
    return
  }
  // ...
}

Objective-C

- (void)loginButton:(FBSDKLoginButton *)loginButton
    didCompleteWithResult:(FBSDKLoginManagerLoginResult *)result
                    error:(NSError *)error {
  if (error == nil) {
    // ...
  } else {
    NSLog(error.localizedDescription);
  }
}

在 UIApplicationDelegate 中匯入 Firebase 模組：

Swift

import FirebaseCore
import FirebaseAuth

Objective-C

@import FirebaseCore;
@import FirebaseAuth;

設定 FirebaseApp 共用例項，通常是在應用程式的 application:didFinishLaunchingWithOptions: 方法中：

Swift

// Use Firebase library to configure APIs
FirebaseApp.configure()

Objective-C

// Use Firebase library to configure APIs
[FIRApp configure];

使用者成功登入後，在 didCompleteWithResult:error: 的實作中，取得已登入使用者的存取權杖，然後兌換為 Identity Platform 憑證：

Swift

let credential = FacebookAuthProvider
  .credential(withAccessToken: AccessToken.current!.tokenString)

Objective-C

FIRAuthCredential *credential = [FIRFacebookAuthProvider
    credentialWithAccessToken:[FBSDKAccessToken currentAccessToken].tokenString];

實作 Facebook 限制登入

如要使用 Facebook 限時登入功能，而非「傳統」Facebook 登入功能，請完成下列步驟。

按照開發人員說明文件的說明，將 Facebook 有限登入功能整合至應用程式。

針對每項登入要求，產生一個專屬的隨機字串 (稱為「Nonce」)，您可以利用這項資訊，確保您取得的 ID 權杖是專門針對應用程式的驗證要求核發。這個步驟對於防範重送攻擊至關重要。您可以使用 SecRandomCopyBytes(_:_:_) 在 iOS 上產生加密安全的 Nonce，如以下範例所示：

Swift

private func randomNonceString(length: Int = 32) -> String {
  precondition(length > 0)
  var randomBytes = [UInt8](repeating: 0, count: length)
  let errorCode = SecRandomCopyBytes(kSecRandomDefault, randomBytes.count, &randomBytes)
  if errorCode != errSecSuccess {
    fatalError(
      "Unable to generate nonce. SecRandomCopyBytes failed with OSStatus \(errorCode)"
    )
  }

  let charset: [Character] =
    Array("0123456789ABCDEFGHIJKLMNOPQRSTUVXYZabcdefghijklmnopqrstuvwxyz-._")

  let nonce = randomBytes.map { byte in
    // Pick a random character from the set, wrapping around if needed.
    charset[Int(byte) % charset.count]
  }

  return String(nonce)
}

Objective-C

// Adapted from https://auth0.com/docs/api-auth/tutorials/nonce#generate-a-cryptographically-random-nonce
- (NSString *)randomNonce:(NSInteger)length {
  NSAssert(length > 0, @"Expected nonce to have positive length");
  NSString *characterSet = @"0123456789ABCDEFGHIJKLMNOPQRSTUVXYZabcdefghijklmnopqrstuvwxyz-._";
  NSMutableString *result = [NSMutableString string];
  NSInteger remainingLength = length;

  while (remainingLength > 0) {
    NSMutableArray *randoms = [NSMutableArray arrayWithCapacity:16];
    for (NSInteger i = 0; i < 16; i++) {
      uint8_t random = 0;
      int errorCode = SecRandomCopyBytes(kSecRandomDefault, 1, &random);
      NSAssert(errorCode == errSecSuccess, @"Unable to generate nonce: OSStatus %i", errorCode);

      [randoms addObject:@(random)];
    }

    for (NSNumber *random in randoms) {
      if (remainingLength == 0) {
        break;
      }

      if (random.unsignedIntValue < characterSet.length) {
        unichar character = [characterSet characterAtIndex:random.unsignedIntValue];
        [result appendFormat:@"%C", character];
        remainingLength--;
      }
    }
  }

  return [result copy];
}

您會透過登入要求傳送 Nonce 的 SHA-256 雜湊，Facebook 會在回應中原封不動地傳遞該雜湊。Identity Platform 會透過對原始 Nonce 進行雜湊運算，並將其與 Facebook 傳遞的值進行比較，驗證回應。

Swift

@available(iOS 13, *)
private func sha256(_ input: String) -> String {
  let inputData = Data(input.utf8)
  let hashedData = SHA256.hash(data: inputData)
  let hashString = hashedData.compactMap {
    String(format: "%02x", $0)
  }.joined()

  return hashString
}

Objective-C

- (NSString *)stringBySha256HashingString:(NSString *)input {
  const char *string = [input UTF8String];
  unsigned char result[CC_SHA256_DIGEST_LENGTH];
  CC_SHA256(string, (CC_LONG)strlen(string), result);

  NSMutableString *hashed = [NSMutableString stringWithCapacity:CC_SHA256_DIGEST_LENGTH * 2];
  for (NSInteger i = 0; i < CC_SHA256_DIGEST_LENGTH; i++) {
    [hashed appendFormat:@"%02x", result[i]];
  }
  return hashed;
}

設定 FBSDKLoginButton 時，請設定委派作業來接收登入和登出事件，將追蹤模式設為 FBSDKLoginTrackingLimited，並附加 Nonce。例如：

Swift

func setupLoginButton() {
    let nonce = randomNonceString()
    currentNonce = nonce
    loginButton.delegate = self
    loginButton.loginTracking = .limited
    loginButton.nonce = sha256(nonce)
}

Objective-C

- (void)setupLoginButton {
  NSString *nonce = [self randomNonce:32];
  self.currentNonce = nonce;
  self.loginButton.delegate = self;
  self.loginButton.loginTracking = FBSDKLoginTrackingLimited
  self.loginButton.nonce = [self stringBySha256HashingString:nonce];
}

在委派函式中實作 didCompleteWithResult:error:。

Swift

func loginButton(_ loginButton: FBSDKLoginButton!, didCompleteWith result: FBSDKLoginManagerLoginResult!, error: Error!) {
  if let error = error {
    print(error.localizedDescription)
    return
  }
  // ...
}

Objective-C

- (void)loginButton:(FBSDKLoginButton *)loginButton
    didCompleteWithResult:(FBSDKLoginManagerLoginResult *)result
                    error:(NSError *)error {
  if (error == nil) {
    // ...
  } else {
    NSLog(error.localizedDescription);
  }
}

在 UIApplicationDelegate 中匯入 Firebase 模組：
Swift
```
import Firebase
```
Objective-C
```
@import Firebase;
```

設定 FirebaseApp 共用例項，通常是在應用程式的 application:didFinishLaunchingWithOptions: 方法中：

Swift

// Use Firebase library to configure APIs
FirebaseApp.configure()

Objective-C

// Use Firebase library to configure APIs
[FIRApp configure];

在使用者成功登入後，在 didCompleteWithResult:error: 的實作中，請使用 Facebook 回應中的 ID 符記，搭配未經雜湊處理的 Nonce，取得 Identity Platform 憑證：

Swift

// Initialize an Identity Platform credential.
let idTokenString = AuthenticationToken.current?.tokenString
let nonce = currentNonce
let credential = OAuthProvider.credential(withProviderID: "facebook.com",
                                          IDToken: idTokenString,
                                          rawNonce: nonce)

Objective-C

// Initialize an Identity Platform credential.
NSString *idTokenString = FBSDKAuthenticationToken.currentAuthenticationToken.tokenString;
NSString *rawNonce = self.currentNonce;
FIROAuthCredential *credential = [FIROAuthProvider credentialWithProviderID:@"facebook.com"
                                                                    IDToken:idTokenString
                                                                   rawNonce:rawNonce];

使用 Identity Platform 進行驗證

最後，請使用 Identity Platform 憑證，透過 Identity Platform 進行驗證：

Swift

Auth.auth().signIn(with: credential) { authResult, error in
    if let error = error {
      let authError = error as NSError
      if isMFAEnabled, authError.code == AuthErrorCode.secondFactorRequired.rawValue {
        // The user is a multi-factor user. Second factor challenge is required.
        let resolver = authError
          .userInfo[AuthErrorUserInfoMultiFactorResolverKey] as! MultiFactorResolver
        var displayNameString = ""
        for tmpFactorInfo in resolver.hints {
          displayNameString += tmpFactorInfo.displayName ?? ""
          displayNameString += " "
        }
        self.showTextInputPrompt(
          withMessage: "Select factor to sign in\n\(displayNameString)",
          completionBlock: { userPressedOK, displayName in
            var selectedHint: PhoneMultiFactorInfo?
            for tmpFactorInfo in resolver.hints {
              if displayName == tmpFactorInfo.displayName {
                selectedHint = tmpFactorInfo as? PhoneMultiFactorInfo
              }
            }
            PhoneAuthProvider.provider()
              .verifyPhoneNumber(with: selectedHint!, uiDelegate: nil,
                                 multiFactorSession: resolver
                                   .session) { verificationID, error in
                if error != nil {
                  print(
                    "Multi factor start sign in failed. Error: \(error.debugDescription)"
                  )
                } else {
                  self.showTextInputPrompt(
                    withMessage: "Verification code for \(selectedHint?.displayName ?? "")",
                    completionBlock: { userPressedOK, verificationCode in
                      let credential: PhoneAuthCredential? = PhoneAuthProvider.provider()
                        .credential(withVerificationID: verificationID!,
                                    verificationCode: verificationCode!)
                      let assertion: MultiFactorAssertion? = PhoneMultiFactorGenerator
                        .assertion(with: credential!)
                      resolver.resolveSignIn(with: assertion!) { authResult, error in
                        if error != nil {
                          print(
                            "Multi factor finanlize sign in failed. Error: \(error.debugDescription)"
                          )
                        } else {
                          self.navigationController?.popViewController(animated: true)
                        }
                      }
                    }
                  )
                }
              }
          }
        )
      } else {
        self.showMessagePrompt(error.localizedDescription)
        return
      }
      // ...
      return
    }
    // User is signed in
    // ...
}

Objective-C

[[FIRAuth auth] signInWithCredential:credential
                          completion:^(FIRAuthDataResult * _Nullable authResult,
                                       NSError * _Nullable error) {
    if (isMFAEnabled && error && error.code == FIRAuthErrorCodeSecondFactorRequired) {
      FIRMultiFactorResolver *resolver = error.userInfo[FIRAuthErrorUserInfoMultiFactorResolverKey];
      NSMutableString *displayNameString = [NSMutableString string];
      for (FIRMultiFactorInfo *tmpFactorInfo in resolver.hints) {
        [displayNameString appendString:tmpFactorInfo.displayName];
        [displayNameString appendString:@" "];
      }
      [self showTextInputPromptWithMessage:[NSString stringWithFormat:@"Select factor to sign in\n%@", displayNameString]
                           completionBlock:^(BOOL userPressedOK, NSString *_Nullable displayName) {
       FIRPhoneMultiFactorInfo* selectedHint;
       for (FIRMultiFactorInfo *tmpFactorInfo in resolver.hints) {
         if ([displayName isEqualToString:tmpFactorInfo.displayName]) {
           selectedHint = (FIRPhoneMultiFactorInfo *)tmpFactorInfo;
         }
       }
       [FIRPhoneAuthProvider.provider
        verifyPhoneNumberWithMultiFactorInfo:selectedHint
        UIDelegate:nil
        multiFactorSession:resolver.session
        completion:^(NSString * _Nullable verificationID, NSError * _Nullable error) {
          if (error) {
            [self showMessagePrompt:error.localizedDescription];
          } else {
            [self showTextInputPromptWithMessage:[NSString stringWithFormat:@"Verification code for %@", selectedHint.displayName]
                                 completionBlock:^(BOOL userPressedOK, NSString *_Nullable verificationCode) {
             FIRPhoneAuthCredential *credential =
                 [[FIRPhoneAuthProvider provider] credentialWithVerificationID:verificationID
                                                              verificationCode:verificationCode];
             FIRMultiFactorAssertion *assertion = [FIRPhoneMultiFactorGenerator assertionWithCredential:credential];
             [resolver resolveSignInWithAssertion:assertion completion:^(FIRAuthDataResult * _Nullable authResult, NSError * _Nullable error) {
               if (error) {
                 [self showMessagePrompt:error.localizedDescription];
               } else {
                 NSLog(@"Multi factor finanlize sign in succeeded.");
               }
             }];
           }];
          }
        }];
     }];
    }
  else if (error) {
    // ...
    return;
  }
  // User successfully signed in. Get user data from the FIRUser object
  if (authResult == nil) { return; }
  FIRUser *user = authResult.user;
  // ...
}];

後續步驟

進一步瞭解 Identity Platform 使用者。
使用其他身分識別提供者登入使用者。