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AWS Documentation » Amazon API Gateway » Developer Guide » Controlling Access to an API in API Gateway » Use API Gateway Lambda Authorizers » Input to an Amazon API Gateway Lambda Authorizer

Input to an Amazon API Gateway Lambda Authorizer

For a Lambda authorizer (formerly known as a custom authorizer) of the TOKEN type, you must specify a custom header as the Token Source when you configure the authorizer for your API. The API client must pass the required authorization token in the incoming request. Upon receiving the incoming method request, API Gateway extracts the token from the custom header. It then passes the token as the authorizationToken property of the event object of the Lambda function, in addition to the method ARN as the methodArn property: 

{
    "type":"TOKEN",
    "authorizationToken":"<caller-supplied-token>",
    "methodArn":"arn:aws:execute-api:<regionId>:<accountId>:<apiId>/<stage>/<method>/<resourcePath>"
}

In this example, the type property specifies the authorizer type, which is a TOKEN authorizer. The <caller-supplied-token> originates from the authorization header in a client request. The methodArn is the ARN of the incoming method request and is populated by API Gateway in accordance with the Lambda authorizer configuration.

For the example TOKEN authorizer Lambda function shown in the preceding section, the <caller-supplied-token> string is allow, deny, unauthorized, or any other string value. An empty string value is the same as unauthorized. The following shows an example of such an input to obtain an Allow policy on the GET method of an API (ymy8tbxw7b) of the AWS account (123456789012) in any stage (*). 

{
    "type":"TOKEN",
    "authorizationToken":"allow",
    "methodArn":"arn:aws:execute-api:us-west-2:123456789012:ymy8tbxw7b/*/GET/"
}

For a Lambda authorizer of the REQUEST type, API Gateway passes the required request parameters to the authorizer Lambda function as part of the event object. The affected request parameters include headers, path parameters, query string parameters, stage variables, and some of request context variables. The API caller can set the path parameters, headers, and query string parameters. The API developer must set the stage variables during the API deployment and API Gateway provides the request context at run time.

The following example shows an input to a REQUEST authorizer for an API method (GET /request) with a proxy integration: 

{
    "type": "REQUEST",
    "methodArn": "arn:aws:execute-api:us-east-1:123456789012:s4x3opwd6i/test/GET/request",
    "resource": "/request",
    "path": "/request",
    "httpMethod": "GET",
    "headers": {
        "X-AMZ-Date": "20170718T062915Z",
        "Accept": "*/*",
        "HeaderAuth1": "headerValue1",
        "CloudFront-Viewer-Country": "US",
        "CloudFront-Forwarded-Proto": "https",
        "CloudFront-Is-Tablet-Viewer": "false",
        "CloudFront-Is-Mobile-Viewer": "false",
        "User-Agent": "...",
        "X-Forwarded-Proto": "https",
        "CloudFront-Is-SmartTV-Viewer": "false",
        "Host": "....execute-api.us-east-1.amazonaws.com",
        "Accept-Encoding": "gzip, deflate",
        "X-Forwarded-Port": "443",
        "X-Amzn-Trace-Id": "...",
        "Via": "...cloudfront.net (CloudFront)",
        "X-Amz-Cf-Id": "...",
        "X-Forwarded-For": "..., ...",
        "Postman-Token": "...",
        "cache-control": "no-cache",
        "CloudFront-Is-Desktop-Viewer": "true",
        "Content-Type": "application/x-www-form-urlencoded"
    },
    "queryStringParameters": {
        "QueryString1": "queryValue1"
    },
    "pathParameters": {},
    "stageVariables": {
        "StageVar1": "stageValue1"
    },
    "requestContext": {
        "path": "/request",
        "accountId": "123456789012",
        "resourceId": "05c7jb",
        "stage": "test",
        "requestId": "...",
        "identity": {
            "apiKey": "...",
            "sourceIp": "..."
        },
        "resourcePath": "/request",
        "httpMethod": "GET",
        "apiId": "s4x3opwd6i"
    }
}

The requestContext is a map of key-value pairs and corresponds to the $context variable. Its outcome is API-dependent. API Gateway may add new keys to the map. For more information about the Lambda function input in a proxy integration, see Input Format of a Lambda Function for Proxy Integration.