#!/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"
CHECK_SCORED_extra734="NOT_SCORED"
CHECK_CIS_LEVEL_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"
CHECK_SERVICENAME_extra734="s3"
CHECK_RISK_extra734='Amazon S3 default encryption provides a way to set the default encryption behavior for an S3 bucket. This will ensure data-at-rest is encrypted.'
CHECK_REMEDIATION_extra734='Ensure that S3 buckets has encryption at rest enabled.'
CHECK_DOC_extra734='https://docs.aws.amazon.com/AmazonS3/latest/dev/bucket-encryption.html'
CHECK_CAF_EPIC_extra734='Data Protection'

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 "${bucket}" --output text 2>&1)
      if grep -q 'AccessDenied' <<< "${BUCKET_LOCATION}"; then
        textInfo "${REGION}: Access Denied Trying to Get Bucket Location for ${bucket}" "${REGION}" "${bucket}"
        continue
      fi
      if [[ $BUCKET_LOCATION == "None" ]]; then
        BUCKET_LOCATION="us-east-1"
      fi
      if [[ $BUCKET_LOCATION == "EU" ]]; then
        BUCKET_LOCATION="eu-west-1"
      fi
      # For this test to pass one of the following must be present:
      # - Configure ServerSideEncryptionConfiguration rule for AES256 or aws:kms
      #  OR
      # - Have bucket policy denying s3:PutObject when s3:x-amz-server-side-encryption is absent
      # query to get if has encryption enabled or not
      RESULT=$("${AWSCLI}" s3api get-bucket-encryption ${PROFILE_OPT} --region ${BUCKET_LOCATION} --bucket "${bucket}" --query ServerSideEncryptionConfiguration.Rules[].ApplyServerSideEncryptionByDefault[].SSEAlgorithm --output text 2>&1)
      if grep -q 'AccessDenied' <<< "${RESULT}"; then
        textInfo "${BUCKET_LOCATION}: Access Denied Trying to Get Encryption for ${bucket}" "${BUCKET_LOCATION}" "${bucket}"
        continue
      elif grep -q 'ServerSideEncryptionConfigurationNotFoundError' <<< "${RESULT}"
      then
        textFail "${BUCKET_LOCATION}: Server Side Encryption configuration is not configured for ${bucket}" "${BUCKET_LOCATION}" "${bucket}"
        continue
      fi

      if [[ "${RESULT}" == "AES256" || "${RESULT}" == "aws:kms" ]];
      then
        textPass "${BUCKET_LOCATION}: Bucket $bucket is enabled for default encryption with ${RESULT}" "${BUCKET_LOCATION}" "${bucket}"
        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 -q 'AccessDenied' <<< "${TEMP_SSE_POLICY_FILE}"; then
        textInfo "${BUCKET_LOCATION}: Access Denied Trying to Get Bucket Policy for ${bucket}" "${BUCKET_LOCATION}" "${bucket}"
        rm -f "${TEMP_SSE_POLICY_FILE}"
        continue
      fi
      if grep -q 'NoSuchBucketPolicy' <<< "${TEMP_SSE_POLICY_FILE}"; then
        textFail "${BUCKET_LOCATION}: No bucket policy for ${bucket}" "${BUCKET_LOCATION}" "${bucket}"
        rm -f "${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=$(jq --arg arn "arn:${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.StringNotEquals."s3:x-amz-server-side-encryption" != null)' < "${TEMP_SSE_POLICY_FILE}")
      if [[ "${CHECK_BUCKET_SSE_POLICY_PRESENT}" == "" ]]; then
        textFail "${BUCKET_LOCATION}: Bucket ${bucket} does not enforce encryption!" "${BUCKET_LOCATION}" "${bucket}"
        rm -f "${TEMP_SSE_POLICY_FILE}"
        continue
      fi
      CHECK_BUCKET_SSE_POLICY_VALUE=$(jq -r '.Condition.StringNotEquals."s3:x-amz-server-side-encryption"' <<< "${CHECK_BUCKET_SSE_POLICY_PRESENT}")

      textPass "${BUCKET_LOCATION}: Bucket ${bucket} has S3 bucket policy to enforce encryption with ${CHECK_BUCKET_SSE_POLICY_VALUE}" "${BUCKET_LOCATION}" "${bucket}"

      rm -f "${TEMP_SSE_POLICY_FILE}"
    done

  else
    textInfo "${REGION}: No S3 Buckets found" "${REGION}"
  fi
}