aws-cloudformationaws-security-group

AWS CloudFormation returning "null" error message

I am creating a Security Group resource via CloudFormation in a yaml template. I am able to create a change set for this, but when I execute the change, the Security Group creation step fails (CREATE_FAILED) with this message:

Resource handler returned message: "null" (RequestToken: <some_token>, HandlerErrorCode: InternalFailure)

Without loss of information, this is how the Security Group is being defined:

MySecurityGroup:
  Type: AWS::EC2::SecurityGroup
  Properties:
    GroupDescription: For allowing something to something when something
    GroupName: !Sub some-prefix-${Environment}
    Tags:
      - Name: Environment
        Value: !Sub ${Environment}
    VpcId: !Sub ${VpcId}

Surely there's something wrong with this definition, but AWS is keeping it a secret ( :

Solution

  • It turns out the problem was that I had simply misread the documentation on key names. A Security Group Tag is documented as:

      Key: String
  Value: String

    But instead of Key, I was using Name on accident!

    I'm documenting this on Stack Overflow just in case anyone else has this error and the solution happens to be similar. I wasn't able to find anything myself online.