How to add AWS WAF to an ALB via CloudFormation

Question

I can't find any examples or documentation on how to associate a WAF with an ALB via CloudFormation. Supposedly its possible going by this news announcement https://aws.amazon.com/about-aws/whats-new/2017/05/cloudformation-support-for-aws-waf-on-alb/ but there isn't anything I've found that shows how. Using CloudFront instead of ALB is well documented but I haven't found a single example with regard to using an ALB (via CloudFormation).

Update: I dont need a full example that does the entire setup for me but at least a snippet that points out how the WAF will know to associate with the ALB or vice versa. The linking is whats missing.

Answer 1

To solve this I browsed through their release history and found the CloudFormation resources that were updated to support WAF & ALB http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/ReleaseHistory.html From there I was able to deduce that the linking component is a WebACLAssociation that maps WAF and ALB. But this also requires that instead of a normal WebACL you must use the WAFRegional. So far it seems to only mean changing ::WAF to ::WAFRegional throughout your code.

WAFRegional (AWS::WAFRegional::WebACL): http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-wafregional-webacl.html

"MyWebACL": {
  "Type": "AWS::WAFRegional::WebACL",
  "Properties": {
    "Name": "WebACL to with three rules",
    "DefaultAction": {
      "Type": "ALLOW"
    },
    "MetricName" : "MyWebACL",
    "Rules": [
      {
        "Action" : {
          "Type" : "BLOCK"
        },
        "Priority" : 1,
        "RuleId" : { "Ref" : "MyRule" }
      },
      {
        "Action" : {
          "Type" : "BLOCK"
        },
        "Priority" : 2,
        "RuleId" : { "Ref" : "BadReferersRule" }
      },
      {
        "Action" : {
          "Type" : "BLOCK"
        },
        "Priority" : 3,
        "RuleId" : { "Ref" : "SqlInjRule" }
      }
    ]
  }      
}

WebACLAssociation (AWS::WAFRegional::WebACLAssociation) http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-wafregional-webaclassociation.html

    "MyWebACLAssociation": {
  "Type": "AWS::WAFRegional::WebACLAssociation",
  "Properties": {
    "ResourceArn": { "Ref": "MyLoadBalancer" },
    "WebACLId": { "Ref": "MyWebACL" }
  }
}