AWS WAF: How to block requests that do not contain a particular header using Terraform

Question

I want to block requests that do not contain Authorization header. I came up with the following rule but I see that the requests which do not contain this header are also being allowed. What is the correct way to specify this condition?

rule {
    name = "restrict-requests-without-authorization-header"
    priority = 2

    action {
      block {}
    }

    statement {
      size_constraint_statement {
        field_to_match {
          single_header {
            name = "authorization"
          }
        }

        comparison_operator = "LE"
        size = 0
        text_transformation {
          priority = 0
          type = "NONE"
        }
      }
    }

    visibility_config {
      cloudwatch_metrics_enabled = true
      metric_name = "restrict-requests-without-authorization-header-metrics"
      sampled_requests_enabled = true
    }
  }

Answer 1

You need to create a rule and a regex patter (can be a wildcard) like this:

RULE:

rule {
    name     = "AuthorizationHeaderRule"
    priority = 1

    action {
      allow {}
    }

        statement {
          regex_pattern_set_reference_statement {
            arn = aws_wafv2_regex_pattern_set.your_regex_pattern.arn

            field_to_match {
              single_header {
                name = "authorization"
              }
            }

            text_transformation {
              priority = 2
              type     = "NONE"
            }
          }
      }

And this can be the regex patter:

resource "aws_wafv2_regex_pattern_set" "your_regex_pattern" {
  name  = "your-regex-pattern"
  scope = "REGIONAL"

  regular_expression {
    regex_string = "prefix-.*"
  }
}