How to create a Custom Authorizer in AWS lambda that takes into account the Base Path Mapping from a Custom Domain Name in API Gateway?

Question

Seems like the authorizer doesn't receive any info related to the base path. Even if you pass it in the context, there seems to be no way to add it to the policy.

eg: domain.com/basepath1**/resource/resourceID** domain.com/basepath2**/resource/resourceID**

current policy statements:

[{ Action: 'execute-api:Invoke', Effect: 'Allow', Resource: 'arn:aws:execute-api:us-east-1:accountID:apiID/dev/GET**/resource/resourceID**' }]

Answer 1

API Gateway recently released some enhancements to customer authorizers, including a new REQUEST type authorizer which is passed much more information from the incoming request. While the base path is not explicitly called out, it may be present in one of the path parameters.

{
    "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"
    }
}

From documentation here