使用自定义声明和安全规则控制访问

Firebase Admin SDK 支持在用户帐户上定义自定义属性。这提供了在 Firebase 应用中实施各种访问控制策略的能力，包括基于角色的访问控制。这些自定义属性可以为用户提供不同级别的访问权限（角色），这些权限在应用程序的安全规则中强制执行。

可以为以下常见情况定义用户角色：

• 授予用户访问数据和资源的管理权限。
• 定义用户所属的不同组。
• 提供多级访问：
  • 区分付费/未付费用户。
  • 将版主与普通用户区分开来。
  • 教师/学生申请等
• 为用户添加附加标识符。例如，Firebase 用户可以映射到另一个系统中的不同 UID。

让我们考虑一个您想要限制对数据库节点“adminContent”的访问的情况。您可以通过在管理员用户列表中查找数据库来做到这一点。但是，您可以使用名为admin的自定义用户声明和以下实时数据库规则更有效地实现相同的目标：

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

自定义用户声明可通过用户的身份验证令牌访问。在上面的示例中，只有在其令牌声明中将admin设置为 true 的用户才具有对adminContent节点的读/写访问权限。由于 ID 令牌已经包含这些断言，因此不需要额外的处理或查找来检查管理员权限。此外，ID 令牌是交付这些自定义声明的可信机制。所有经过身份验证的访问都必须在处理相关请求之前验证 ID 令牌。

本页中描述的代码示例和解决方案来自Admin SDK提供的客户端 Firebase Auth API 和服务器端 Auth API。

通过 Admin SDK 设置和验证自定义用户声明

自定义声明可能包含敏感数据，因此它们只能由 Firebase Admin SDK 从特权服务器环境中设置。

// 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.
  });

// 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.

# 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.

// 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.
auth.go

// 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.

自定义声明对象不应包含任何OIDC保留键名称或Firebase 保留名称。自定义声明有效负载不得超过 1000 字节。

发送到后端服务器的 ID 令牌可以使用 Admin SDK 确认用户的身份和访问级别，如下所示：

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

// 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.
}

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

// 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.
	}
}
auth.go

// 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.
    }
}

您还可以检查用户现有的自定义声明，这些声明可作为用户对象的属性使用：

// 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']);
  });

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

# 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'))

// 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)
	}
}
auth.go

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

您可以通过为customClaims传递 null 来删除用户的自定义声明。

将自定义声明传播给客户端

通过 Admin SDK 在用户上修改新声明后，它们会通过 ID 令牌以下列方式传播到客户端上经过身份验证的用户：

• 修改自定义声明后，用户登录或重新验证。结果颁发的 ID 令牌将包含最新的声明。
• 旧令牌过期后，现有用户会话会刷新其 ID 令牌。
• 通过调用currentUser.getIdToken(true)强制刷新 ID 令牌。

访问客户端上的自定义声明

只能通过用户的 ID 令牌检索自定义声明。根据用户的角色或访问级别修改客户端 UI 可能需要访问这些声明。但是，在验证并解析其声明后，应始终通过 ID 令牌强制执行后端访问。自定义声明不应直接发送到后端，因为它们不能在令牌之外被信任。

最新声明传播到用户的 ID 令牌后，您可以通过检索 ID 令牌来获取它们：

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);
  });

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();
    }
  }
});

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()
  }
})

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];
    }
  }
}];

自定义声明的最佳实践

自定义声明仅用于提供访问控制。它们并非旨在存储其他数据（例如配置文件和其他自定义数据）。虽然这似乎是一种方便的机制，但强烈建议不要这样做，因为这些声明存储在 ID 令牌中，并且可能导致性能问题，因为所有经过身份验证的请求始终包含与登录用户对应的 Firebase ID 令牌。

• 使用自定义声明来存储数据，仅用于控制用户访问。所有其他数据应通过实时数据库或其他服务器端存储单独存储。
• 自定义声明的大小有限。传递大于 1000 字节的自定义声明有效负载将引发错误。

示例和用例

以下示例说明了特定 Firebase 用例上下文中的自定义声明。

在创建用户时通过 Firebase 函数定义角色

在此示例中，自定义声明是在使用 Cloud Functions 创建用户时设置的。

可以使用 Cloud Functions 添加自定义声明，并使用实时数据库立即传播。该函数仅在使用onCreate触发器注册时调用。一旦设置了自定义声明，它们就会传播到所有现有和未来的会话。下次用户使用用户凭据登录时，令牌将包含自定义声明。

客户端实现 (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);
  }
});

云函数逻辑

添加了一个新的数据库节点 (metadata/($uid)}，其读/写限制为经过身份验证的用户。

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);
    }
  }
});

数据库规则

{
  "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
      }
    }
  }
}

通过 HTTP 请求定义角色

以下示例通过 HTTP 请求对新登录的用户设置自定义用户声明。

客户端实现 (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);
});

后端实施（管理 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' }));
  }
});

升级现有用户的访问级别时可以使用相同的流程。以免费用户升级到付费订阅为例。用户的 ID 令牌通过 HTTP 请求与支付信息一起发送到后端服务器。成功处理付款后，通过 Admin SDK 将用户设置为付费订阅者。成功的 HTTP 响应返回给客户端以强制刷新令牌。

通过后端脚本定义角色

可以将循环脚本（不是从客户端启动）设置为运行以更新用户自定义声明：

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);
  });

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);
}

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
    })

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)
	}

}
auth.go

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);
}

自定义声明也可以通过 Admin SDK 逐步修改：

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);
  });

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);
}

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)

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)
	}

}
auth.go

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 = new Dictionary<string, object>(user.CustomClaims);
    // Add level.
    claims["level"] = 10;
    // Add custom claims for additional privileges.
    await FirebaseAuth.DefaultInstance.SetCustomUserClaimsAsync(user.Uid, claims);
}