#!/usr/bin/env bash

# Prowler - the handy cloud security tool (copyright 2018) by Toni de la Fuente
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may not
# use this file except in compliance with the License. You may obtain a copy
# of the License at http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software distributed
# under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
# CONDITIONS OF ANY KIND, either express or implied. See the License for the
# specific language governing permissions and limitations under the License.
CHECK_ID_extra734="7.34"
CHECK_TITLE_extra734="[extra734] Check if S3 buckets have default encryption (SSE) enabled or use a bucket policy to enforce it (Not Scored) (Not part of CIS benchmark)"
CHECK_SCORED_extra734="NOT_SCORED"
CHECK_TYPE_extra734="EXTRA"
CHECK_SEVERITY_extra734="Medium"
CHECK_ASFF_RESOURCE_TYPE_extra734="AwsS3Bucket"
CHECK_ALTERNATE_check734="extra734"
CHECK_ASFF_COMPLIANCE_TYPE_extra734="ens-mp.info.3.s3.1"

extra734(){
  LIST_OF_BUCKETS=$($AWSCLI s3api list-buckets $PROFILE_OPT --region $REGION --query Buckets[*].Name --output text|xargs -n1)
  if [[ $LIST_OF_BUCKETS ]]; then
    for bucket in $LIST_OF_BUCKETS;do
      BUCKET_LOCATION=$($AWSCLI s3api get-bucket-location $PROFILE_OPT --region $REGION --bucket $bucket --output text)
      # For this test to pass one of the following must be present:
      # - Configure ServerSideEncryptionConfiguration rule for AES256 or aws:kms
      #  OR
      # - Have bucket policy denying s3:PutObject when s3:x-amz-server-side-encryption is absent

      if [[ $BUCKET_LOCATION == "None" ]]; then
        BUCKET_LOCATION="us-east-1"
      fi
      if [[ $BUCKET_LOCATION == "EU" ]]; then
        BUCKET_LOCATION="eu-west-1"
      fi
      # query to get if has encryption enabled or not
      RESULT=$($AWSCLI s3api get-bucket-encryption $PROFILE_OPT --region $BUCKET_LOCATION --bucket $bucket --query ServerSideEncryptionConfiguration.Rules[].ApplyServerSideEncryptionByDefault[].SSEAlgorithm --output text 2>&1)
      if [[ $(echo "$RESULT" | grep AccessDenied) ]]; then
        textFail "Access Denied Trying to Get Encryption for $bucket"
        continue
      fi

      if [[ $RESULT == "AES256" || $RESULT == "aws:kms" ]];
      then
        textPass "Bucket $bucket is enabled for default encryption with $RESULT"
        continue
      fi

      TEMP_SSE_POLICY_FILE=$(mktemp -t prowler-${ACCOUNT_NUM}-${bucket}.policy.XXXXXXXXXX)

      # get bucket policy
      $AWSCLI s3api get-bucket-policy $PROFILE_OPT --bucket $bucket --region $BUCKET_LOCATION --output text --query Policy > $TEMP_SSE_POLICY_FILE 2>&1
      if [[ $(grep AccessDenied $TEMP_SSE_POLICY_FILE) ]]; then
        textFail "Access Denied Trying to Get Bucket Policy for $bucket"
        rm -f $TEMP_SSE_POLICY_FILE
        continue
      fi
      if [[ $(grep NoSuchBucketPolicy $TEMP_SSE_POLICY_FILE) ]]; then
        textFail "No bucket policy for $bucket"
        rm -f $TEMP_SSE_POLICY_FILE
        continue
      fi

      # check if the S3 policy forces SSE s3:x-amz-server-side-encryption:true
      CHECK_BUCKET_SSE_POLICY_PRESENT=$(cat $TEMP_SSE_POLICY_FILE | jq --arg arn "arn:${AWS_PARTITION}:s3:::${bucket}/*" '.Statement[]|select(.Effect=="Deny" and ((.Principal|type == "object") and .Principal.AWS == "*") or ((.Principal|type == "string") and .Principal == "*") and .Action=="s3:PutObject" and .Resource==$arn and .Condition.StringEquals."s3:x-amz-server-side-encryption" != null)')
      if [[ $CHECK_BUCKET_SSE_POLICY_PRESENT == "" ]]; then
        textFail "Bucket $bucket does not enforce encryption!"
        rm -f $TEMP_SSE_POLICY_FILE
        continue
      fi
      CHECK_BUCKET_SSE_POLICY_VALUE=$(echo "$CHECK_BUCKET_SSE_POLICY_PRESENT" | jq -r '.Condition.StringNotEquals."s3:x-amz-server-side-encryption"')

      textPass "Bucket $bucket has S3 bucket policy to enforce encryption with $CHECK_BUCKET_SSE_POLICY_VALUE"

      rm -f $TEMP_SSE_POLICY_FILE
    done

  else
    textInfo "No S3 Buckets found"
  fi
}