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" }
  }
}

Answer 2

I found the simplest way to associate a WebACL with an ALB to be to just use the AWS CLI. In my scenario the WebACL is a shared resource and therefore is owned by a different CloudFormation stack to the ALB. After deploying the ALB stack, by deployment script simply does this...

aws wafv2 associate-web-acl --web-acl-arn <WEB_ACL_ARN> --resource-arn <ALB_ARN>

Answer 3

Below is the example in YAML format.

   Resources:
    WafAcldev:
     DependsOn: Whitelist
     DependsOn: WafRule
     Type: AWS::WAF::WebACL
     Condition: CreateDEVResources
     Properties:
      DefaultAction:
        Type: "BLOCK"
      MetricName: test
      Name: test
      Rules:
        -
          Action:
            Type: "ALLOW"
          Priority: 1
          RuleId: !Ref WafRule

    WafRule:
        DependsOn: WhitelistIPdev
        Type: AWS::WAF::Rule
        Condition: CreateDEVResources
        Properties:
          MetricName: test
          Name: test
          Predicates:
            -
              DataId:
               Ref: "Whitelist"
              Negated: false
              Type: "IPMatch"

    MyWebACLAssociation:
          Type: "AWS::WAFRegional::WebACLAssociation"
          Properties:
            ResourceArn: arn:aws:elasticloadbalancing:us-east-2:123456789012:listener/app/my-load-balancer/1234567890123456/1234567890123456
            WebACLId:
              Ref: WafAcldev
    Whitelist:
        Type: AWS::WAF::IPSet
        Condition: CreateDEVResources
        Properties:
          Name: "IPSet for Whitelisted IP adresses"
          IPSetDescriptors:
            -
             Type: "IPV4"
             Value: "213.126.223.11/32"
            -