Is it possible to require a custom header like

"x-amz-meta-blah:foobar"

when making a GET request for an s3 object as part of your bucket policy?

Something like;

{
  "Version":"2012-10-17",
  "Statement":[
   {
     "Sid":"111",
     "Effect":"Allow",
     "Principal":{
      "AWS":"123456789"
     },
     "Action":"s3:GetObject",
     "Resource":"arn:aws:s3:::bucket01/*"
   },
   {
     "Sid":"112",
     "Effect":"Allow",
     "Principal":{
      "AWS":"123456789"
     },
     "Action":"s3:GetObject",
     "Resource":"arn:aws:s3:::bucket01/*",
     "Condition":{
      "StringEquals":{
        "s3:x-amz-meta-blah":[
         "x-amz-meta-blah:foobar"
        ]
      }
     }
   }
  ]
}