Validate path param in AWS API Gateway through OpenAPI spec

Question

I created a POST API with path parameter and request body through openAPI spec.

```
"/v2/{lang}/subject": {
  "post": {
    "parameters": [
        {
          "name": "lang",
          "in": "path",
          "required": true,
          "type": "string"
        },
        {
          "in": "body",
          "name": "subject",
          "required": true,
          "schema": {
            "$ref": "#/definitions/subject"
          }
        }
      ],
    "requestBody": {
      "content": {
        "application/json": {
          "schema": {
            "$ref": "#/components/schemas/subject"
          }
        }
      },
      "required": true
    },
    "x-amazon-apigateway-request-validator" : "all",
    .....
   }
```
I want to validate the path param and request body at APIGW. Unfortunately, 1 test case is failing.

If I try accessing API with missing lang, ex: https://apigwsampleurl.com/v2/subject, AWS APIGW is throwing Missing Authentication Token error.

How this case should be handled through openapi configuration?

Answer

Hello,

I understand that you have created POST API with path parameter and request body validation using OpenAPI definition. You tested by sending API request with missing {lang}, to validate the path parameter, however it is not validating properly. Please correct, if I am misunderstanding.

API Gateway currently does not support request’s path parameter validation. If the schema includes "required: true”, basic request validation only verifies if the parameter is included. If you require that only specific paths should exist, please create the resource for those paths separately.

https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-method-request-validation.html

As a workaround, you can also consider implementing request validation logic, using Lambda authorizer or at the backend API integration itself.

API returns 403 “Missing Authentication Token” error, if request is made to a resource that doesn't exist, eg: /v2/subject. https://aws.amazon.com/premiumsupport/knowledge-center/api-gateway-authentication-token-errors/

We already have a feature request open with API Gateway service team, to support path parameter validation. I have added this post to the feature request. While I am unable to comment on if/when this feature may get released, I request you to keep an eye on our What's New (https://aws.amazon.com/new/) and Blog (https://aws.amazon.com/blogs/aws/) pages for any new feature announcements.

Please let us know if you have any further questions or concerns.

Validate path param in AWS API Gateway through OpenAPI spec

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