aws-cloudfront: cdk incorrectly prevents attaching certificate when no aliases are given

[lexhl]

Describe the bug

Hi, I am trying to follow the instructions on how to move an alias from an existing alias from one CloudFront distribution to another. The instructions says that I need to set up the target distribution with a certificate that includes the alternative domain name that I want to move: https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/CNAMEs.html#alternate-domain-names-move-create-target

However when I try to set up the distribution with the certificate but without the alternative domain names (as directed in the instructions) I run into an error 'Must specify at least one domain name to use a certificate with a distribution' generated I think from this like of code within CDK:

aws-cdk/packages/aws-cdk-lib/aws-cloudfront/lib/distribution.ts
Line 323 in 6fdc458

 throw new Error('Must specify at least one domain name to use a certificate with a distribution'); 

It seems that CDK prevents me from adding a certificate unless I have a domain name; but that means I cannot follow the process for moving an alias from an old distribution to a new one. I can create a distribution with a certificate and no alias if I use the aws web console to do it; so I think CDK is wrong with this validation.

Expected Behavior

CDK should allow me to create a cloudfront distribution that has an ACM certificate attached but no aliases

Current Behavior

CDK raises an error message 'Must specify at least one domain name to use a certificate with a distribution' when I try to create a cloudfront distribution that has an ACM certificate attached but no aliases

Reproduction Steps

       distribution = cloudfront.Distribution(
            self,
            "Distribution",
            domain_names=[],
            default_behavior=cloudfront.BehaviorOptions(
                origin=origins.HttpOrigin(
                    dns_name,
                    protocol_policy=cloudfront.OriginProtocolPolicy.HTTPS_ONLY,
                    origin_ssl_protocols=[
                        cloudfront.OriginSslPolicy.TLS_V1_1,
                        cloudfront.OriginSslPolicy.TLS_V1_2,
                    ],
                    read_timeout=Duration.seconds(60),
                ),
                viewer_protocol_policy=cloudfront.ViewerProtocolPolicy.REDIRECT_TO_HTTPS,
                origin_request_policy=cloudfront.OriginRequestPolicy.ALL_VIEWER,
                cache_policy=cache_policy,
                allowed_methods=cloudfront.AllowedMethods.ALLOW_ALL,
                compress=True,
            ),
            price_class=cloudfront.PriceClass.PRICE_CLASS_200,
            enabled=True,
            log_includes_cookies=False,
            log_bucket=logging_bucket,
            enable_logging=True,
            web_acl_id=waf_acl_arn,
            ssl_support_method=cloudfront.SSLMethod.SNI,
            certificate=my_certificate,
            minimum_protocol_version=cloudfront.SecurityPolicyProtocol.TLS_V1_2_2021,
        )

Possible Solution

Remove the spurious validation check:

      if ((props.domainNames ?? []).length === 0) {
        throw new Error('Must specify at least one domain name to use a certificate with a distribution');
      }

Additional Information/Context

No response

CDK CLI Version

2.137.0 (build bb90b4c)

Framework Version

No response

Node.js Version

v21.7.1

OS

Mac OS

Language

Python

Language Version

Python 3.11

Other information

No response

[lexhl]

I believe as a work-around it is possible to proceed by using the escape hatches to manipulate the CloudFormation output:

        cfn_distribution: cloudfront.CfnDistribution = distribution.node.default_child
        cfn_distribution.add_property_override(
            "DistributionConfig.ViewerCertificate",
            {
                "AcmCertificateArn": my_certificate.certificate_arn,
                "SslSupportMethod": "sni-only",
                "MinimumProtocolVersion": "TLSv1.2_2021",
            },
        )

[ashishdhingra]

@lexhl Good afternoon. Per link https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/CNAMEs.html#alternate-domain-names-move-create-target that you shared, it specifies to Get an SSL/TLS certificate that includes the alternate domain name that you are moving.. However, you are trying to set up the distribution with the certificate but without the alternative domain names, which is not what instructions mention. Please let me know if I'm missing anything.

Thanks,
Ashish

[lexhl]

@ashishdhingra

@lexhl Good afternoon. Per link https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/CNAMEs.html#alternate-domain-names-move-create-target that you shared, it specifies to Get an SSL/TLS certificate that includes the alternate domain name that you are moving.. However, you are trying to set up the distribution with the certificate but without the alternative domain names, which is not what instructions mention. Please let me know if I'm missing anything.

Hi, the relevant instructions as per the article are as pasted below. You can see that you are required to first setup the distribution with the certificate but without the alias.

The second step is to run the associate-alias command, which moves the alias. This command is only allowed to be run if you have already created a target distribution that has the correct certificate attached but does not have the alias already associated with it. This is the point of the CloudFront associate-alias command.

This all works fine if done via the boto3 APIs or the web console. Only CDK blocks it -because CDK wrongly does not allow me to attach a certificate to a distribution that has no alias.

If you attempt to create a distribution that has the same alias as an existing distribution then CloudFront will prevent that. Hence why the associate-alias command exists to allow for zero downtime migration of aliases from one distribution to another.

1. Get an SSL/TLS certificate that includes the alternate domain name that you are moving. If you don’t have one, you can request one from AWS Certificate Manager (ACM), or get one from another certificate authority (CA) and import it into ACM. Make sure that you request or import the certificate in the US East (N. Virginia) (us-east-1) Region.
2. If you haven’t created the target distribution, create one now. As part of creating the target distribution, associate your certificate (from the previous step) with the distribution. For more information, see Creating a distribution.
3. If you already have a target distribution, associate your certificate (from the previous step) with the target distribution. For more information, see Updating a distribution.
4. Create a DNS TXT record that associates the alternate domain name with the distribution domain name of the target distribution. Create your TXT record with an underscore (_) in front of the alternate domain name. The following shows an example TXT record in DNS:
5. _www.example.com TXT d111111abcdef8.cloudfront.net
6. CloudFront uses this TXT record to validate your ownership of the alternate domain name.

.... and ...

1. Use the AWS CLI to run the CloudFront associate-alias command, as shown in the following example. Replace www.example.com with the alternate domain name, and EDFDVBD6EXAMPLE with the target distribution ID. Run this command using credentials that are in the same AWS account as the target distribution. Note the following restrictions for using this command:

   • You must have cloudfront:AssociateAlias and cloudfront:UpdateDistribution permissions on the target distribution.
   • If the source and target distributions are in the same AWS account, you must have cloudfront:UpdateDistribution permission on the source distribution.
   • If the source and target distributions are in different AWS accounts, the source distribution must be disabled.
   • The target distribution must be set up as described in Set up the target distribution.

   aws cloudfront associate-alias --alias www.example.com --target-distribution-id EDFDVBD6EXAMPLE
   

   This command updates both distributions by removing the alternate domain name from the source distribution and adding it to the target distribution.

2. After the target distribution is fully deployed, update your DNS configuration to point the alternate domain name’s DNS record to the distribution domain name of the target distribution.

[lexhl]

Hi @ashishdhingra I have had confirmation from AWS premium support that they have reproduced the issue and they also suggested a similar workaround that I suggested above of using the L1 constructs instead (which does work). However it would be nice if the L2 construct just allowed this use case as it is an important use case sometimes.

Quote from AWS support:

I was also facing the same error-> "Must specify at least one domain name to use a certificate with a distribution
at new Distribution" [1] [2]
This is due to the CDK limitation.

A possible workaround to resolve this issue could be using L1 Constructs. 
I have tested the below code and it is working fine.

[code showing use of L1 Constructs matching my L2 sample]

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