I figured it out, there needs to be a "Null" condition to handle the case where the header is not present.  The following policy will require SSE-KMS encryption on all objects in the bucket "testing".

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Deny",
            "Sid": "RequireAWSKMS",
            "Principal": "*",
            "Action": "s3:PutObject",
            "Resource": "arn:aws:s3:::testing/*",
            "Condition": {
                "StringNotEquals": {
                    "s3:x-amz-server-side-encryption": "aws:kms"
                }
            }
        },
        {
            "Effect": "Deny",
            "Sid": "RequireEncHeader",
            "Principal": "*",
            "Action": "s3:PutObject",
            "Resource": "arn:aws:s3:::testing/*",
            "Condition": {
                "Null": {
                    "s3:x-amz-server-side-encryption": "true"
                }
            }
        }
    ]
}



On Thu, Apr 30, 2020 at 5:52 AM Abhishek Lekshmanan <abhishek@suse.com> wrote:
Wyllys Ingersoll <wyllys.ingersoll@keepertech.com> writes:

> In Mimic, how extensive is the S3 bucket policy support?
>
> I'm trying to configure a bucket to require encryption using the following
> policy, but it doesn't appear to have any effect, I can still upload
> unencrypted objects. I tried different variations on the policy structure
> but nothing seems to have any effect and I don't see anything in the logs
> (debug_rgw = 5/5).

The policy asks to deny PutObject requests when
s3:x-amz-server-side-encryption is not aws:kms. But if the string is not
supplied the condition is not evaluated.

Try an allow-based policy with StringEquals? also you might want to
restrict the Principal to a specific user/tenant if that is an intent ?
>
> {
>     "Version": "2012-10-17",
>     "Statement": [
>         {
>             "Effect": "Deny",
>             "Principal": "*",
>             "Action": "s3:PutObject",
>             "Resource": "arn:aws:s3:::testing/*",
>             "Condition": {
>                 "StringNotEquals": {
>                     "s3:x-amz-server-side-encryption": "aws:kms"
>                 }
>             }
>         }
>     ]
> }
>
>
> Thanks,
>    Wyllys Ingersoll
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--
Abhishek Lekshmanan
SUSE Software Solutions Germany GmbH
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah, HRB 21284 (AG Nürnberg)