#!/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_extra771="7.71"
CHECK_TITLE_extra771="[extra771] Check if S3 buckets have policies which allow WRITE access "
CHECK_SCORED_extra771="NOT_SCORED"
CHECK_CIS_LEVEL_extra771="EXTRA"
CHECK_SEVERITY_extra771="Critical"
CHECK_ASFF_RESOURCE_TYPE_extra771="AwsS3Bucket"
CHECK_ALTERNATE_check771="extra771"
CHECK_SERVICENAME_extra771="s3"
CHECK_RISK_extra771='Non intended users can put objects in a given bucket.'
CHECK_REMEDIATION_extra771='Ensure proper bucket policy is in place with the least privilege principle applied.'
CHECK_DOC_extra771='https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_examples_s3_rw-bucket.html'
CHECK_CAF_EPIC_extra771='IAM'

extra771(){
  LIST_OF_BUCKETS=$("${AWSCLI}" s3api list-buckets $PROFILE_OPT --region "${REGION}" --query "sort_by(Buckets, &Name)[].Name" --output text 2>&1)
  if [[ $(echo "${LIST_OF_BUCKETS}" | grep -E 'AccessDenied|UnauthorizedOperation|AuthorizationError') ]]; then
      textInfo "${REGION}: Access Denied trying to list buckets" "${REGION}"
      return
  fi
  if [[ "${LIST_OF_BUCKETS}" ]]; then
    for bucket in ${LIST_OF_BUCKETS};do
      BUCKET_POLICY_STATEMENTS=$("${AWSCLI}" s3api $PROFILE_OPT get-bucket-policy --region "${REGION}" --bucket "${bucket}" --output json --query Policy 2>&1)
      if [[ $(echo "${BUCKET_POLICY_STATEMENTS}" | grep -E 'AccessDenied|UnauthorizedOperation|AuthorizationError') ]]; then
          textInfo "${REGION}: Access Denied trying to get bucket policy for ${bucket}" "${REGION}"
          continue
      fi
      if [[ $(echo "${BUCKET_POLICY_STATEMENTS}" | grep 'NoSuchBucketPolicy') ]]; then
        textInfo "$REGION: Bucket policy does not exist for bucket $bucket" "$REGION"
      else
        BUCKET_POLICY_BAD_STATEMENTS=$(echo "${BUCKET_POLICY_STATEMENTS}" | jq --compact-output --arg arn "arn:${AWS_PARTITION}:s3:::$bucket" 'fromjson | .Statement[]|select(
                                                                                                                                                                            .Effect=="Allow" and
                                                                                                                                                                            (
                                                                                                                                                                                ( (.Principal|type == "object") and (.Principal.AWS == "*") ) or
                                                                                                                                                                                ( (.Principal|type == "string") and (.Principal == "*") )
                                                                                                                                                                            ) and
                                                                                                                                                                            (
                                                                                                                                                                                ( (.Action|type == "string") and (.Action|startswith("s3:Put")) ) or
                                                                                                                                                                                ( (.Action|type == "string") and (.Action|startswith("s3:*")) ) or
                                                                                                                                                                                ( (.Action|type == "array") and (.Action[]|startswith("s3:Put")) ) or
                                                                                                                                                                                ( (.Action|type == "array") and (.Action[]|startswith("s3:*")) )
                                                                                                                                                                            ) and
                                                                                                                                                                            .Condition == null
                                                                                                                                                                          )' | tr '\n' ' ')
        # Make sure JSON comma characted will not break CSV output. Replace "," by word "[comma]"
        BUCKET_POLICY_BAD_STATEMENTS="${BUCKET_POLICY_BAD_STATEMENTS//,/[comma]}"
        if [[ "${BUCKET_POLICY_BAD_STATEMENTS}" != "" ]]; then
          textFail "${REGION}: Bucket ${bucket} allows public write: ${BUCKET_POLICY_BAD_STATEMENTS}" "${REGION}" "${bucket}"
        else
          textPass "${REGION}: Bucket ${bucket} has S3 bucket policy which does not allow public write access" "${REGION}" "${bucket}"
        fi
      fi
    done
  else
    textInfo "${REGION}: No S3 Buckets found"
  fi
}