Create user and credentials for S3 multipart upload, output credentials for later configuration

s3-multipart-upload-example-step1.json

"S3UploadUser" : {
  "Type" : "AWS::IAM::User",
  "Properties" : {
    "Path" : "/",
    "Policies" : [ {
      "PolicyName" : "S3MultipartUpload",
      "PolicyDocument" : {
        "Version": "2012-10-17",
        "Statement" : [ {
          "Effect" : "Allow",
          "Action" : [ "s3:PutObject", "s3:GetObject", "s3:AbortMultipartUpload", "s3:ListMultipartUploadParts", "s3:ListBucketMultipartUploads" ],
          "Resource" : [
              { "Fn::Join" : [ "", ["arn:aws:s3:::", { "Ref" : "UploadBucketName" }, "/*"]]}
          ]
        }]
      }
    }]
  }
},
"S3UploadKey" : {
  "Type" : "AWS::IAM::AccessKey",
  "Properties" : {
    "Status": "Active",
    "UserName" : { "Ref" : "S3UploadUser" }
  }
}
.................
// Outputs for EC2 instances:
"S3UploadAccessKeyId": {
    "Description": "Access key id for S3 upload",
    "Value": { "Ref" : "S3UploadKey" }
},
"S3UploadSecretKey": {
    "Description": "Secret key for S3 upload",
    "Value" : { "Fn::GetAtt" : [ "S3UploadKey", "SecretAccessKey" ] }
}