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AWSTemplateFormatVersion: '2010-09-09'
Description: Creates an S3 proxy to access S3 Gateway Endpoints over cconnections such as VPN, Direct Connect and VPC Peering.
Parameters: 
  InstanceType:
    Type: String
    Default: c5n.large
    Description: Squid proxy instance type.
  AllowedIpRange:
    Type: String
    Description: CIDR Range allowed to use the proxy. Eg the On-prem network using the proxy.
    Default: 10.0.0.0/8
  VpcCidr:
    Type: String
    Description: The VPC CIDR where the proxy whould be deployed
    Default: 10.24.34.128/25
  NumberOfInstances:
    Type: Number
    Description: Number of Squid proxies behind the Load balancer.
    Default: 1
  VpcId:
    Type: AWS::EC2::VPC::Id
    Description: VPC ID to launch this stack
  Subnets:
    Type: List<AWS::EC2::Subnet::Id>
    Description: The subnets the Proxy should be deploy into.
  ProxyListenerPort:
    Type: Number
    Default: 8080
  ImageId:
    Type: AWS::SSM::Parameter::Value<AWS::EC2::Image::Id>
    Default: '/aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2'

Resources:
  NetworkLoadBalancer:
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties:
      Scheme: internal
      LoadBalancerAttributes:
        - Key: load_balancing.cross_zone.enabled
          Value: 'true'
      Subnets: !Ref Subnets
      Type: network
      IpAddressType: ipv4
      Tags:
      - Key: Name
        Value: !Sub ${AWS::StackName} Network Load Balancer

  HttpListener:
    Type: AWS::ElasticLoadBalancingV2::Listener
    Properties:
      DefaultActions:
      - TargetGroupArn: !Ref TargetGroupHTTP
        Type: forward
      LoadBalancerArn: !Ref NetworkLoadBalancer
      Port: !Ref ProxyListenerPort
      Protocol: TCP

  TargetGroupHTTP:
    Type: AWS::ElasticLoadBalancingV2::TargetGroup
    Properties:
      Port: 8888
      Protocol:  TCP
      VpcId: !Ref 'VpcId'

  EC2InstanceProfile:
    Type: 'AWS::IAM::InstanceProfile'
    Properties:
      Roles:
        - Ref: EC2Role
      Path: /
  EC2Role:
    Type: 'AWS::IAM::Role'
    Properties:
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Effect: Allow
            Principal:
              Service:
                - ec2.amazonaws.com
            Action:
              - 'sts:AssumeRole'
      Policies:
        - PolicyName: s3-all-bucket-proxy-policy
          PolicyDocument:
            Version: '2012-10-17'
            Statement:
              - Effect: Allow
                Action:
                  - 's3:*Object*'
                  - 's3:ListBucket'
                Resource: '*'
              - Effect: Allow
                Action:
                  - 'ec2:ModifyInstanceAttribute'
                Resource: '*'
      ManagedPolicyArns:
      - arn:aws:iam::aws:policy/AmazonSSMManagedInstanceCore

  EC2SecurityGroup:
    Type: 'AWS::EC2::SecurityGroup'
    Properties:
      GroupDescription: Squid proxy EC2 security group
      VpcId: !Ref 'VpcId'
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 8888
          ToPort: 8888
          CidrIp: !Ref 'AllowedIpRange'
        - IpProtocol: tcp
          FromPort: 8888
          ToPort: 8888
          CidrIp: !Ref 'VpcCidr'
      SecurityGroupEgress:
        - CidrIp: 0.0.0.0/0
          FromPort: -1
          IpProtocol: '-1'
          ToPort: -1

  LaunchConfig:
    Type: AWS::AutoScaling::LaunchConfiguration
    Properties:
      AssociatePublicIpAddress: false
      InstanceType: !Ref InstanceType
      SecurityGroups:
        - !Ref EC2SecurityGroup
      ImageId: !Ref ImageId
      InstanceMonitoring: true
      IamInstanceProfile: !Ref EC2InstanceProfile
      UserData: !Base64
        Fn::Sub: |
          #!/bin/bash -xe
          yum install -y squid
          instanceID=$(curl http://169.254.169.254/latest/meta-data/instance-id)

          aws ec2 modify-instance-attribute --no-source-dest-check --instance-id $instanceID --region ${AWS::Region}
          
          cat > /etc/squid/squid.conf << 'EOF'
          acl SSL_ports port 443
          acl Safe_ports port 80                    # http
          acl Safe_ports port 21                    # ftp
          acl Safe_ports port 443                  # https
          acl Safe_ports port 70                    # gopher
          acl Safe_ports port 210                  # wais
          acl Safe_ports port 1025-65535  # unregistered ports
          acl Safe_ports port 280                  # http-mgmt
          acl Safe_ports port 488                  # gss-http
          acl Safe_ports port 591                  # filemaker
          acl Safe_ports port 777                  # multiling http
          acl CONNECT method CONNECT
          http_access deny !Safe_ports
          http_access deny CONNECT !SSL_ports
          http_access allow localhost manager
          http_access deny manager
          http_access allow all
          http_access allow localhost
          http_access deny all
          http_port 8888
          coredump_dir /var/spool/squid
          refresh_pattern ^ftp:                     1440       20%        10080
          refresh_pattern ^gopher:            1440       0%          1440
          refresh_pattern -i (/cgi-bin/|\?) 0             0%          0
          refresh_pattern (Release|Packages(.gz)*)$      0       20%     2880
          refresh_pattern .                             0              20%        4320
          visible_hostname ec2.internal
          EOF
          chmod 400 /etc/squid/squid.conf
          systemctl start squid
          systemctl enable squid

  ASGroup:
    Type: AWS::AutoScaling::AutoScalingGroup
    Properties:
      DesiredCapacity: !Ref NumberOfInstances
      HealthCheckType: ELB
      HealthCheckGracePeriod: 300
      VPCZoneIdentifier: !Ref Subnets
      MaxSize: !Ref NumberOfInstances
      MinSize: !Ref NumberOfInstances
      TargetGroupARNs:
      - !Ref TargetGroupHTTP
      LaunchConfigurationName: !Ref LaunchConfig
 
Outputs:
  HttpProxy:
    Description: NLB DNS Name and Port
    Value: !Sub http://${NetworkLoadBalancer.DNSName}:${ProxyListenerPort}

  ProxyAddress:
    Description: NLB DNS Name
    Value: !Sub ${NetworkLoadBalancer.DNSName}

  ProxyPort:
    Description: NLB Port
    Value: !Sub ${ProxyListenerPort}