Force Server Side Encryption for S3 Bucket
I want to set an S3 bucket policy so that all requests to upload to that bucket will use server side encryption, even if it is not specified in the request header.
I have seen this post (Amazon S3 Server Side Encryption Bucket Policy problems) where someone has managed to set a bucket policy that denies all put requests that don't specify server side encryption, but I don't want to deny, I want the puts to succeed but use server side encryption.
My issue is with streaming the output from EMR to my S3 bucket, I don't control the code that is making the requests, and it seems to me that server side encryption must be specified on a per request basis.
Answer
IMHO There is no way to automatically tell Amazon S3 to turn on SSE for every PUT requests. So, what I would investigate is the following :
write a script that list your bucket
for each object, get the meta data
if SSE is not enabled, use the PUT COPY API (http://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectCOPY.html) to add SSE "(...) When copying an object, you can preserve most of the metadata (default) or specify new metadata (...)"
If the PUT operation succeeded, use the DELETE object API to delete the original object
Then run that script on an hourly or daily basis, depending on your business requirements. You can use S3 API in Python (http://boto.readthedocs.org/en/latest/ref/s3.html) to make it easier to write the script.
If this "change-after-write" solution is not valid for you business wise, you can work at different level (aligned with Julio's answer above)
use a proxy between your API client and S3 API (like a reverse proxy on your site), and configure it to add the SSE HTTP header for every PUT / POST requests. Developer must go through the proxy and not be authorised to issue requests against S3 API endpoints
write a wrapper library to add the SSE meta data automatically and oblige developer to use your library on top of the SDK.
The later today are a matter of discipline in the organisation, as it is not easy to enforce them at a technical level.
Seb