Authorizer Tips

Here are some tips for working with API Gateway Authorizers. The tips may help those who are newer to API Gateway Authorizers.

Authorizer Type: Token

The token authorizer type is the simplest. The authorizer expects a secret token to pass in the header of the request. The header key is configured with the identity_source property. Example:

authorizer(
  name: "MyAuthorizer",
  identity_source: "Auth", # maps to method.request.header.Auth
  type: :token,
)

Example of passing the header with curl:

curl -H "Auth: test" https://bxqim55nwg.execute-api.us-west-2.amazonaws.com/dev/protected/url

API Gateway converts the Auth Host header to authorizationToken. Make sure the request you send to your API Gateway endpoint has the header configured in the identity_source, not authorizationToken.

By the time it hits the Authorizer Lambda function it looks like this:

{
    "type": "TOKEN",
    "methodArn": "arn:aws:execute-api:us-west-2:112233445566:bxqim55nwg/dev/GET/protected/url",
    "authorizationToken": "test"
}

So within the authorizer Lambda function, you can get the token with event['authorizationToken'].

Identity Source: Token

If the request does not include the host header that matches with the identify source, then the Lambda authorizer function does not even get called! You’ll get an Unauthorized response like so:

$ curl -H "WrongHeader: test" https://bxqim55nwg.execute-api.us-west-2.amazonaws.com/dev/protected/url
{"message":"Unauthorized"}

Remember even though you get a response. The response is from the AWS API Gateway side only. The request never hits your authorizer function. Please make sure to pass the header that matches what’s configured for identity_source. Jets sets Auth as the default identity source header.

Authorizer Type: Request

The request authorizer type is almost as simple as the token type. The Jets authorizer method uses it as as the default type. With the request type, you have more control over what items from the request that get passed through to the authorizer function. You also receive a fuller event payload in this structure:

{
    "type": "REQUEST",
    "methodArn": "arn:aws:execute-api:us-west-2:112233445566:lntmrm92ba/dev/GET/my/path",
    "resource": "/my/path",
    "path": "/my/path",
    "httpMethod": "GET",
    "headers": {
        "headerauth1": "headerValue1",
        ...
    },
    "multiValueHeaders": {...},
    "queryStringParameters": {
        "QueryString1": "queryValue1"
    },
    "multiValueQueryStringParameters": {..},
    "pathParameters": {},
    "stageVariables": {},
    "requestContext": {
        ...
        "identity": {
            "cognitoIdentityPoolId": null,
            ...
            "cognitoAuthenticationType": null,
            "cognitoAuthenticationProvider": null,
        },
        "domainName": "lntmrm92ba.execute-api.us-west-2.amazonaws.com",
        "apiId": "lntmrm92ba"
    }
}

Identity Sources: Request

For request type authorizers, the identity sources can be request headers, query string parameters, stage names, and or context variables. They are set as a comma-separated list on the identity_source property. Example:

authorizer(
  name: "MyAuthorizer",
  identity_source: "method.request.header.Header1,method.request.querystring.QueryString1",
  type: :request,
)

All identity sources must be provided with the request. If the request does not pass all the items in the identity_source list, then the Lambda authorizer function does not even get called! Remember to send them all. Example:

curl -H "Header1: test" "https://bxqim55nwg.execute-api.us-west-2.amazonaws.com/dev/protected/url?QueryString1=test"

Disable Caching First

When working with authorizers for the first time, it will likely help if you disable caching. Jets does not set the ttl property by default. So by default, caching is disabled.

Note, the CloudFormation docs state that the default ttl is 300, but that only seems to be with the API Gateway console.

Pro tip: Use the <- and -> arrow keys to move back and forward.

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