Amazon Web Services has made it easy to implement encryption-at-rest for S3 buckets, but older S3 buckets may have predated this feature enhancement. If you have a large number of buckets, this could be a tedious thing to check via the console. Here is a simple one-liner to check all the buckets in a single account:
for ITEM in $(aws s3api list-buckets --profile $MYACCOUNT --output json | grep Name \ | cut -d":" -f2 | cut -d'"' -f2); do echo $ITEM " --- " $(aws s3api get-bucket-encryption \ --bucket $item --profile $MYACCOUNT 2>&1); done
Obviously you would set the value of MYACCOUNT with the name of the AWS Account you are inspecting. Alternatively you could also iterate through a number of AWS accounts by nesting the above command in another FOR loop.
The output will look like the following two lines, where the first example bucket ("my-unencrypted-bucket") shows the error that is returned by the get-bucket-encryption command when the default encryption is not set while the other line shows the response when default encryption is set.
my-unencrypted-bucket --- An error occurred (ServerSideEncryptionConfigurationNotFoundError) when calling the GetBucketEncryption operation: The server side encryption configuration was not found my-encrypted-bucket --- APPLYSERVERSIDEENCRYPTIONBYDEFAULT AES256