定義您的 Lambda 函數

AWS IoT Core 叫用您的授權方時，它會觸發與授權方相關聯的 Lambda，其中包含下列JSON物件的事件。範例JSON物件包含所有可能的欄位。不包含與連線請求無關的任何欄位。

{
    "token" :"aToken",
    "signatureVerified": Boolean, // Indicates whether the device gateway has validated the signature.
    "protocols": ["tls", "http", "mqtt"], // Indicates which protocols to expect for the request.
    "protocolData": {
        "tls" : {
            "serverName": "serverName" // The server name indication (SNI) host_name string.
        },
        "http": {
            "headers": {
                "#{name}": "#{value}"
            },
            "queryString": "?#{name}=#{value}"
        },
        "mqtt": {
            "username": "myUserName",
            "password": "myPassword", // A base64-encoded string.
            "clientId": "myClientId" // Included in the event only when the device sends the value.
        }
    },
    "connectionMetadata": {
        "id": UUID // The connection ID. You can use this for logging.
    },
}

Lambda 函數應該使用此資訊來驗證傳入連線，並決定連線中允許哪些動作。此函數應該傳送包含下列值的回應。

 下列JSON物件包含 Lambda 函數可以傳送的回應範例。

{
"isAuthenticated":true, //A Boolean that determines whether client can connect.
"principalId": "xxxxxxxx",  //A string that identifies the connection in logs.
"disconnectAfterInSeconds": 86400, 
"refreshAfterInSeconds": 300, 
 "policyDocuments": [
      {
        "Version": "2012-10-17",
        "Statement": [
           {
              "Action": "iot:Publish",
              "Effect": "Allow",
              "Resource": "arn:aws:iot:us-east-1:<your_aws_account_id>:topic/customauthtesting"
            }
         ]
       }
    ]
}

policyDocument 值必須包含有效的 AWS IoT Core 政策文件。如需 AWS IoT Core 政策的詳細資訊，請參閱 AWS IoT Core 政策。在MQTT連線之間TLS和MQTT連線 WebSockets之間，針對 refreshAfterInSeconds 欄位值中指定的間隔 AWS IoT Core 快取此政策。在HTTP連線的情況下，除非您的裝置使用HTTP持續連線 （也稱為HTTP保持連線或HTTP連線重複使用），否則 Lambda 函數會針對每個授權請求呼叫 ，您可以選擇在設定授權方時啟用快取。在此間隔期間， 會針對此快取政策在已建立的連線中 AWS IoT Core 授權動作，而不會再次觸發您的 Lambda 函數。如果在自訂身分驗證期間發生失敗， 會 AWS IoT Core 終止連線。如果連線開啟的時間超過 disconnectAfterInSeconds參數中指定的值， AWS IoT Core 也會終止連線。

下列 JavaScript 包含範例 Node.js Lambda 函數，可在 MQTT Connect 訊息中尋找值為 的密碼，test並傳回政策，該政策授予許可，以 AWS IoT Core 與名為 的用戶端連線，myClientName並發佈至包含相同用戶端名稱的主題。如果找不到預期的密碼，它會傳回拒絕這兩個動作的政策。

// A simple Lambda function for an authorizer. It demonstrates 
// how to parse an MQTT password and generate a response.

exports.handler = function(event, context, callback) { 
    var uname = event.protocolData.mqtt.username;
    var pwd = event.protocolData.mqtt.password;
    var buff = new Buffer(pwd, 'base64');
    var passwd = buff.toString('ascii');
    switch (passwd) { 
        case 'test': 
            callback(null, generateAuthResponse(passwd, 'Allow')); 
            break;
        default: 
            callback(null, generateAuthResponse(passwd, 'Deny'));  
    }
};

// Helper function to generate the authorization response.
var generateAuthResponse = function(token, effect) { 
    var authResponse = {}; 
    authResponse.isAuthenticated = true; 
    authResponse.principalId = 'TEST123'; 
    
    var policyDocument = {}; 
    policyDocument.Version = '2012-10-17'; 
    policyDocument.Statement = []; 
    var publishStatement = {}; 
    var connectStatement = {};
    connectStatement.Action = ["iot:Connect"];
    connectStatement.Effect = effect;
    connectStatement.Resource = ["arn:aws:iot:us-east-1:123456789012:client/myClientName"];
    publishStatement.Action = ["iot:Publish"]; 
    publishStatement.Effect = effect; 
    publishStatement.Resource = ["arn:aws:iot:us-east-1:123456789012:topic/telemetry/myClientName"]; 
    policyDocument.Statement[0] = connectStatement;
    policyDocument.Statement[1] = publishStatement; 
    authResponse.policyDocuments = [policyDocument]; 
    authResponse.disconnectAfterInSeconds = 3600; 
    authResponse.refreshAfterInSeconds = 300;
    
    return authResponse; 
}

上述 Lambda 函數會在 MQTT Connect 訊息test中收到預期的 密碼JSON時傳回下列項目。password 和 principalId 屬性的值將是 MQTT Connect 訊息的值。

{
  "password": "password",
  "isAuthenticated": true,
  "principalId": "principalId",
  "policyDocuments": [
    {
      "Version": "2012-10-17",
      "Statement": [
        {
          "Action": "iot:Connect",
          "Effect": "Allow",
          "Resource": "*"
        },
        {
          "Action": "iot:Publish",
          "Effect": "Allow",
          "Resource": "arn:aws:iot:region:accountId:topic/telemetry/${iot:ClientId}"
        },
        {
          "Action": "iot:Subscribe",
          "Effect": "Allow",
          "Resource": "arn:aws:iot:region:accountId:topicfilter/telemetry/${iot:ClientId}"
        },
        {
          "Action": "iot:Receive",
          "Effect": "Allow",
          "Resource": "arn:aws:iot:region:accountId:topic/telemetry/${iot:ClientId}"
        }
      ]
    }
  ],
  "disconnectAfterInSeconds": 3600,
  "refreshAfterInSeconds": 300
}