How to read S3 object from encrypted S3 bucket using ebextensions files?

Hi,

I am trying to create a file from an encrypted s3 bucket in my EB instance using the "files" key in an ebextensions configuration file.
It's failing with a 400 error and the message: "Requests specifying Server Side Encryption with AWS KMS managed keys require AWS Signature Version 4."

Here are some details:

• The bucket is encrypted with a custom KMS key
• I'm using the "AWS::CloudFormation::Authentication" resource with role-based authentication
  eg:
  Resources:
  AWSEBAutoScalingGroup:
  Metadata:
  AWS::CloudFormation::Authentication:
  S3Auth:
  type: "s3"
  buckets:
  - "Fn::GetOptionSetting":
  Namespace: "aws:elasticbeanstalk:application:environment"
  OptionName: "ConfigBucketName"
  roleName:
  "Fn::GetOptionSetting":
  Namespace: "aws:autoscaling:launchconfiguration"
  OptionName: "IamInstanceProfile"

The role is set up with the correct policy to ListBucket and GetObject on the s3 bucket and the role is added as a Key User in KMS.
Any pointers on how to get this to work?

Thanks,
Kwan