運用自訂著作權聲明和安全性規則控管存取權

Firebase Admin SDK 可讓您在使用者帳戶中定義自訂屬性。這可讓您在 Firebase 應用程式中實作各種存取控制策略,包括以角色為基礎的存取控制。這些自訂屬性可為使用者提供不同層級的存取權 (角色),並在應用程式的安全性規則中強制執行。

使用者角色可用於下列常見情況:

  • 授予使用者管理權限,以便存取資料和資源。
  • 定義使用者所屬的不同群組。
  • 提供多層級存取權:
    • 區分付費/免付費訂閱者。
    • 區分版主和一般使用者。
    • 老師/學生申請表等
  • 為使用者新增其他 ID。舉例來說,Firebase 使用者可能會對應至其他系統中的不同 UID。

假設您想限制對資料庫節點「adminContent」的存取權,您可以透過管理員使用者清單中的資料庫查詢來執行這項操作。不過,您可以使用名為 admin 的自訂使用者宣稱,搭配下列 Realtime Database 規則,更有效率地達成相同目標:

{
  "rules": {
    "adminContent": {
      ".read": "auth.token.admin === true",
      ".write": "auth.token.admin === true",
    }
  }
}

您可以透過使用者的驗證權杖存取自訂使用者宣告。在上述範例中,只有在權杖宣告中將 admin 設為 true 的使用者,才能讀取/寫入 adminContent 節點。由於 ID 權杖已包含這些斷言,因此無需額外處理或查詢,即可檢查管理員權限。此外,ID 權杖是提供這些自訂宣告的可信賴機制。所有已驗證的存取權都必須先驗證 ID 權杖,才能處理相關要求。

本頁所述的程式碼範例和解決方案,皆取自用戶端 Firebase Auth API 和 Admin SDK 提供的伺服器端 Auth API。

透過 Admin SDK 設定及驗證自訂使用者憑證

自訂權杖可能包含敏感資料,因此只有 Firebase Admin SDK 才能在特權伺服器環境中設定這些權杖。

Node.js

// Set admin privilege on the user corresponding to uid.

getAuth()
  .setCustomUserClaims(uid, { admin: true })
  .then(() => {
    // The new custom claims will propagate to the user's ID token the
    // next time a new one is issued.
  });

Java

// Set admin privilege on the user corresponding to uid.
Map<String, Object> claims = new HashMap<>();
claims.put("admin", true);
FirebaseAuth.getInstance().setCustomUserClaims(uid, claims);
// The new custom claims will propagate to the user's ID token the
// next time a new one is issued.

Python

# Set admin privilege on the user corresponding to uid.
auth.set_custom_user_claims(uid, {'admin': True})
# The new custom claims will propagate to the user's ID token the
# next time a new one is issued.

Go

// Get an auth client from the firebase.App
client, err := app.Auth(ctx)
if err != nil {
	log.Fatalf("error getting Auth client: %v\n", err)
}

// Set admin privilege on the user corresponding to uid.
claims := map[string]interface{}{"admin": true}
err = client.SetCustomUserClaims(ctx, uid, claims)
if err != nil {
	log.Fatalf("error setting custom claims %v\n", err)
}
// The new custom claims will propagate to the user's ID token the
// next time a new one is issued.

C#

// Set admin privileges on the user corresponding to uid.
var claims = new Dictionary<string, object>()
{
    { "admin", true },
};
await FirebaseAuth.DefaultInstance.SetCustomUserClaimsAsync(uid, claims);
// The new custom claims will propagate to the user's ID token the
// next time a new one is issued.

自訂權利聲明物件不得包含任何 OIDC 保留的鍵名稱或 Firebase 保留名稱。自訂宣告酬載不得超過 1000 個位元組。

傳送至後端伺服器的 ID 權杖可透過 Admin SDK 確認使用者的身分和存取層級,如下所示:

Node.js

// Verify the ID token first.
getAuth()
  .verifyIdToken(idToken)
  .then((claims) => {
    if (claims.admin === true) {
      // Allow access to requested admin resource.
    }
  });

Java

// Verify the ID token first.
FirebaseToken decoded = FirebaseAuth.getInstance().verifyIdToken(idToken);
if (Boolean.TRUE.equals(decoded.getClaims().get("admin"))) {
  // Allow access to requested admin resource.
}

Python

# Verify the ID token first.
claims = auth.verify_id_token(id_token)
if claims['admin'] is True:
    # Allow access to requested admin resource.
    pass

Go

// Verify the ID token first.
token, err := client.VerifyIDToken(ctx, idToken)
if err != nil {
	log.Fatal(err)
}

claims := token.Claims
if admin, ok := claims["admin"]; ok {
	if admin.(bool) {
		//Allow access to requested admin resource.
	}
}

C#

// Verify the ID token first.
FirebaseToken decoded = await FirebaseAuth.DefaultInstance.VerifyIdTokenAsync(idToken);
object isAdmin;
if (decoded.Claims.TryGetValue("admin", out isAdmin))
{
    if ((bool)isAdmin)
    {
        // Allow access to requested admin resource.
    }
}

您也可以查看使用者現有的自訂宣稱,這些宣稱可做為使用者物件的屬性:

Node.js

// Lookup the user associated with the specified uid.
getAuth()
  .getUser(uid)
  .then((userRecord) => {
    // The claims can be accessed on the user record.
    console.log(userRecord.customClaims['admin']);
  });

Java

// Lookup the user associated with the specified uid.
UserRecord user = FirebaseAuth.getInstance().getUser(uid);
System.out.println(user.getCustomClaims().get("admin"));

Python

# Lookup the user associated with the specified uid.
user = auth.get_user(uid)
# The claims can be accessed on the user record.
print(user.custom_claims.get('admin'))

Go

// Lookup the user associated with the specified uid.
user, err := client.GetUser(ctx, uid)
if err != nil {
	log.Fatal(err)
}
// The claims can be accessed on the user record.
if admin, ok := user.CustomClaims["admin"]; ok {
	if admin.(bool) {
		log.Println(admin)
	}
}

C#

// Lookup the user associated with the specified uid.
UserRecord user = await FirebaseAuth.DefaultInstance.GetUserAsync(uid);
Console.WriteLine(user.CustomClaims["admin"]);

您可以傳遞 customClaims 的空值,藉此刪除使用者的自訂宣告。

將自訂憑證傳播至用戶端

透過 Admin SDK 修改使用者的新宣告後,系統會透過 ID 權杖,以以下方式將這些宣告傳播至用戶端的已驗證使用者:

  • 自訂權利聲明修改後,使用者會登入或重新驗證。因此,系統會在 ID 權杖中加入最新的憑證附加資訊。
  • 當舊權杖到期後,現有使用者工作階段會重新整理 ID 權杖。
  • 呼叫 currentUser.getIdToken(true) 可強制重新整理 ID 權杖。

在用戶端存取自訂憑證附加資訊

您只能透過使用者的 ID 權杖擷取自訂權杖。您可能需要存取這些宣告,才能根據使用者的角色或存取層級修改用戶端 UI。不過,您應一律在驗證 ID 權杖並剖析其宣告後,透過 ID 權杖強制執行後端存取權。自訂宣告不應直接傳送至後端,因為在權杖之外無法信任這些宣告。

最新的宣告已傳播至使用者的 ID 權杖,您可以透過擷取 ID 權杖來取得這些宣告:

JavaScript

firebase.auth().currentUser.getIdTokenResult()
  .then((idTokenResult) => {
     // Confirm the user is an Admin.
     if (!!idTokenResult.claims.admin) {
       // Show admin UI.
       showAdminUI();
     } else {
       // Show regular user UI.
       showRegularUI();
     }
  })
  .catch((error) => {
    console.log(error);
  });

Android

user.getIdToken(false).addOnSuccessListener(new OnSuccessListener<GetTokenResult>() {
  @Override
  public void onSuccess(GetTokenResult result) {
    boolean isAdmin = result.getClaims().get("admin");
    if (isAdmin) {
      // Show admin UI.
      showAdminUI();
    } else {
      // Show regular user UI.
      showRegularUI();
    }
  }
});

Swift

user.getIDTokenResult(completion: { (result, error) in
  guard let admin = result?.claims?["admin"] as? NSNumber else {
    // Show regular user UI.
    showRegularUI()
    return
  }
  if admin.boolValue {
    // Show admin UI.
    showAdminUI()
  } else {
    // Show regular user UI.
    showRegularUI()
  }
})

Objective-C

user.getIDTokenResultWithCompletion:^(FIRAuthTokenResult *result,
                                      NSError *error) {
  if (error != nil) {
    BOOL *admin = [result.claims[@"admin"] boolValue];
    if (admin) {
      // Show admin UI.
      [self showAdminUI];
    } else {
      // Show regular user UI.
      [self showRegularUI];
    }
  }
}];

自訂宣告的最佳做法

自訂權杖僅用於提供存取權控管。這些資料並非用於儲存額外資料 (例如設定檔和其他自訂資料)。雖然這似乎是方便的做法,但我們強烈建議您不要這麼做,因為這些驗證聲明會儲存在 ID 權杖中,且可能會導致效能問題,因為所有已驗證的要求都會包含與已登入使用者相對應的 Firebase ID 權杖。

  • 請使用自訂權利要求,只儲存用於控制使用者存取權的資料。所有其他資料都應透過即時資料庫或其他伺服器端儲存空間分開儲存。
  • 自訂權利聲明的大小有限制。如果傳遞的自訂宣告酬載大於 1000 個位元組,系統會擲回錯誤。

範例和用途

以下範例說明特定 Firebase 用途中的自訂權杖。

在建立使用者時透過 Firebase 函式定義角色

在這個範例中,使用 Cloud Functions 建立使用者時,會設定自訂憑證。

您可以使用 Cloud Functions 新增自訂權利要求,並立即透過 Realtime Database 進行傳播。這個函式只會在使用 onCreate 觸發條件註冊時呼叫。自訂宣告設定完成後,就會套用至所有現有和未來的工作階段。下次使用者以使用者憑證登入時,權杖就會包含自訂權杖。

用戶端實作 (JavaScript)

const provider = new firebase.auth.GoogleAuthProvider();
firebase.auth().signInWithPopup(provider)
.catch(error => {
  console.log(error);
});

let callback = null;
let metadataRef = null;
firebase.auth().onAuthStateChanged(user => {
  // Remove previous listener.
  if (callback) {
    metadataRef.off('value', callback);
  }
  // On user login add new listener.
  if (user) {
    // Check if refresh is required.
    metadataRef = firebase.database().ref('metadata/' + user.uid + '/refreshTime');
    callback = (snapshot) => {
      // Force refresh to pick up the latest custom claims changes.
      // Note this is always triggered on first call. Further optimization could be
      // added to avoid the initial trigger when the token is issued and already contains
      // the latest claims.
      user.getIdToken(true);
    };
    // Subscribe new listener to changes on that node.
    metadataRef.on('value', callback);
  }
});

Cloud Functions 邏輯

新增資料庫節點 (metadata/($uid)},其讀/寫權限僅限於已驗證的使用者。

const functions = require('firebase-functions');
const { initializeApp } = require('firebase-admin/app');
const { getAuth } = require('firebase-admin/auth');
const { getDatabase } = require('firebase-admin/database');

initializeApp();

// On sign up.
exports.processSignUp = functions.auth.user().onCreate(async (user) => {
  // Check if user meets role criteria.
  if (
    user.email &&
    user.email.endsWith('@admin.example.com') &&
    user.emailVerified
  ) {
    const customClaims = {
      admin: true,
      accessLevel: 9
    };

    try {
      // Set custom user claims on this newly created user.
      await getAuth().setCustomUserClaims(user.uid, customClaims);

      // Update real-time database to notify client to force refresh.
      const metadataRef = getDatabase().ref('metadata/' + user.uid);

      // Set the refresh time to the current UTC timestamp.
      // This will be captured on the client to force a token refresh.
      await  metadataRef.set({refreshTime: new Date().getTime()});
    } catch (error) {
      console.log(error);
    }
  }
});

資料庫規則

{
  "rules": {
    "metadata": {
      "$user_id": {
        // Read access only granted to the authenticated user.
        ".read": "$user_id === auth.uid",
        // Write access only via Admin SDK.
        ".write": false
      }
    }
  }
}

透過 HTTP 要求定義角色

以下範例會透過 HTTP 要求,針對新登入的使用者設定自訂使用者宣告。

用戶端實作 (JavaScript)

const provider = new firebase.auth.GoogleAuthProvider();
firebase.auth().signInWithPopup(provider)
.then((result) => {
  // User is signed in. Get the ID token.
  return result.user.getIdToken();
})
.then((idToken) => {
  // Pass the ID token to the server.
  $.post(
    '/setCustomClaims',
    {
      idToken: idToken
    },
    (data, status) => {
      // This is not required. You could just wait until the token is expired
      // and it proactively refreshes.
      if (status == 'success' && data) {
        const json = JSON.parse(data);
        if (json && json.status == 'success') {
          // Force token refresh. The token claims will contain the additional claims.
          firebase.auth().currentUser.getIdToken(true);
        }
      }
    });
}).catch((error) => {
  console.log(error);
});

後端實作 (Admin SDK)

app.post('/setCustomClaims', async (req, res) => {
  // Get the ID token passed.
  const idToken = req.body.idToken;

  // Verify the ID token and decode its payload.
  const claims = await getAuth().verifyIdToken(idToken);

  // Verify user is eligible for additional privileges.
  if (
    typeof claims.email !== 'undefined' &&
    typeof claims.email_verified !== 'undefined' &&
    claims.email_verified &&
    claims.email.endsWith('@admin.example.com')
  ) {
    // Add custom claims for additional privileges.
    await getAuth().setCustomUserClaims(claims.sub, {
      admin: true
    });

    // Tell client to refresh token on user.
    res.end(JSON.stringify({
      status: 'success'
    }));
  } else {
    // Return nothing.
    res.end(JSON.stringify({ status: 'ineligible' }));
  }
});

升級現有使用者的存取層級時,可以使用相同的流程。舉例來說,免費使用者升級為付費訂閱。使用者的 ID 權杖會透過 HTTP 要求,連同付款資訊傳送至後端伺服器。付款成功處理後,系統會透過 Admin SDK 將使用者設為付費訂閱者。成功的 HTTP 回應會傳回至用戶端,以便強制重新整理權杖。

透過後端指令碼定義角色

您可以設定定期執行的 (非由用戶端啟動) 指令碼,以便更新使用者的自訂宣告:

Node.js

getAuth()
  .getUserByEmail('user@admin.example.com')
  .then((user) => {
    // Confirm user is verified.
    if (user.emailVerified) {
      // Add custom claims for additional privileges.
      // This will be picked up by the user on token refresh or next sign in on new device.
      return getAuth().setCustomUserClaims(user.uid, {
        admin: true,
      });
    }
  })
  .catch((error) => {
    console.log(error);
  });

Java

UserRecord user = FirebaseAuth.getInstance()
    .getUserByEmail("user@admin.example.com");
// Confirm user is verified.
if (user.isEmailVerified()) {
  Map<String, Object> claims = new HashMap<>();
  claims.put("admin", true);
  FirebaseAuth.getInstance().setCustomUserClaims(user.getUid(), claims);
}

Python

user = auth.get_user_by_email('user@admin.example.com')
# Confirm user is verified
if user.email_verified:
    # Add custom claims for additional privileges.
    # This will be picked up by the user on token refresh or next sign in on new device.
    auth.set_custom_user_claims(user.uid, {
        'admin': True
    })

Go

user, err := client.GetUserByEmail(ctx, "user@admin.example.com")
if err != nil {
	log.Fatal(err)
}
// Confirm user is verified
if user.EmailVerified {
	// Add custom claims for additional privileges.
	// This will be picked up by the user on token refresh or next sign in on new device.
	err := client.SetCustomUserClaims(ctx, user.UID, map[string]interface{}{"admin": true})
	if err != nil {
		log.Fatalf("error setting custom claims %v\n", err)
	}

}

C#

UserRecord user = await FirebaseAuth.DefaultInstance
    .GetUserByEmailAsync("user@admin.example.com");
// Confirm user is verified.
if (user.EmailVerified)
{
    var claims = new Dictionary<string, object>()
    {
        { "admin", true },
    };
    await FirebaseAuth.DefaultInstance.SetCustomUserClaimsAsync(user.Uid, claims);
}

您也可以透過 Admin SDK 逐步修改自訂宣稱:

Node.js

getAuth()
  .getUserByEmail('user@admin.example.com')
  .then((user) => {
    // Add incremental custom claim without overwriting existing claims.
    const currentCustomClaims = user.customClaims;
    if (currentCustomClaims['admin']) {
      // Add level.
      currentCustomClaims['accessLevel'] = 10;
      // Add custom claims for additional privileges.
      return getAuth().setCustomUserClaims(user.uid, currentCustomClaims);
    }
  })
  .catch((error) => {
    console.log(error);
  });

Java

UserRecord user = FirebaseAuth.getInstance()
    .getUserByEmail("user@admin.example.com");
// Add incremental custom claim without overwriting the existing claims.
Map<String, Object> currentClaims = user.getCustomClaims();
if (Boolean.TRUE.equals(currentClaims.get("admin"))) {
  // Add level.
  currentClaims.put("level", 10);
  // Add custom claims for additional privileges.
  FirebaseAuth.getInstance().setCustomUserClaims(user.getUid(), currentClaims);
}

Python

user = auth.get_user_by_email('user@admin.example.com')
# Add incremental custom claim without overwriting existing claims.
current_custom_claims = user.custom_claims
if current_custom_claims.get('admin'):
    # Add level.
    current_custom_claims['accessLevel'] = 10
    # Add custom claims for additional privileges.
    auth.set_custom_user_claims(user.uid, current_custom_claims)

Go

user, err := client.GetUserByEmail(ctx, "user@admin.example.com")
if err != nil {
	log.Fatal(err)
}
// Add incremental custom claim without overwriting existing claims.
currentCustomClaims := user.CustomClaims
if currentCustomClaims == nil {
	currentCustomClaims = map[string]interface{}{}
}

if _, found := currentCustomClaims["admin"]; found {
	// Add level.
	currentCustomClaims["accessLevel"] = 10
	// Add custom claims for additional privileges.
	err := client.SetCustomUserClaims(ctx, user.UID, currentCustomClaims)
	if err != nil {
		log.Fatalf("error setting custom claims %v\n", err)
	}

}

C#

UserRecord user = await FirebaseAuth.DefaultInstance
    .GetUserByEmailAsync("user@admin.example.com");
// Add incremental custom claims without overwriting the existing claims.
object isAdmin;
if (user.CustomClaims.TryGetValue("admin", out isAdmin) && (bool)isAdmin)
{
    var claims = user.CustomClaims.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
    // Add level.
    var level = 10;
    claims["level"] = level;
    // Add custom claims for additional privileges.
    await FirebaseAuth.DefaultInstance.SetCustomUserClaimsAsync(user.Uid, claims);
}