Programatically associating Lambda@Edge with a CloudFront distribution

Here's a little script which can be used to programatically associate Lambda@Edge functions with CloudFront.

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It's input is a JSON configuration file (cf-associations.json) that looks like this:

[
  {
    "distributionId":"ASDFASDFASDF",
    "DefaultCacheBehavior": 
      {
        "Quantity": 2,
        "Items": [
          {
            "LambdaFunctionARN": "arn:aws:lambda:us-east-1:12345:function:yourfunctionname:",
            "EventType": "origin-response"
          },
          {
            "LambdaFunctionARN": "arn:aws:lambda:us-east-1:12345:function:baisc-auth:",
            "EventType": "viewer-request"
          }
        ]
      },
    "CacheBehaviors": [
      {
        "path": "/somepathcsp*",
        "rules": 
        {
          "Quantity": 1,
          "Items": [
            {
              "LambdaFunctionARN": "arn:aws:lambda:us-east-1:12345:function:anotherfunction:",
              "EventType": "origin-response"
            }
          ]
        }
      },
      {
        "path": "/someotherpath*",
        "rules": 
        {
          "Quantity": 0
        }
      }
    ]
  }
]

The rules are a 1 to 1 mapping to the JSON structure returned by the aws cloudfront get-distribution-config command, with the only difference being that the ARN does not include the version number.

The script parses the config, grabs the current distribution configuration, publishes a new Lambda version (if necessary), and associates the configured behaviors to the right Lambda functions.