API Gateway with open access

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Metadata

Id: 15ccec05-5476-4890-ad19-53991eba1db8

Cloud Provider: aws

Framework: Terraform

Severity: Medium

Category: Insecure Configurations

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Description

API Gateway methods should restrict the authorization type to prevent unauthenticated access, except for the OPTIONS method used in CORS preflight requests. If you configure an API Gateway method without specifying authorization, as shown in the example below, it allows open, unauthenticated access to your API, increasing the risk of data exposure and abuse.

resource "aws_api_gateway_method" "example" {
  http_method   = "GET"
  authorization = "NONE"
  // ...
}

Proper configuration requires setting authorization = "NONE" only for the OPTIONS method. For example:

resource "aws_api_gateway_method" "example" {
  http_method   = "OPTIONS"
  authorization = "NONE"
  // ...
}

This ensures that only preflight CORS requests remain unauthenticated, while all other methods require proper authorization, reducing the attack surface of your API.

Compliant Code Examples

resource "aws_api_gateway_method" "negative1" {
  rest_api_id   = aws_api_gateway_rest_api.this.id
  resource_id   = aws_api_gateway_resource.this.id
  http_method   = "OPTIONS"
  authorization = "NONE"
  authorizer_id = aws_api_gateway_authorizer.this.id

  request_parameters = {
    "method.request.path.proxy" = true
  }
}

Non-Compliant Code Examples

resource "aws_api_gateway_method" "positive1" {
  rest_api_id   = aws_api_gateway_rest_api.this.id
  resource_id   = aws_api_gateway_resource.this.id
  http_method   = "GET"
  authorization = "NONE"
  authorizer_id = aws_api_gateway_authorizer.this.id

  request_parameters = {
    "method.request.path.proxy" = true
  }
}