vpc-ssh-bastion.yaml

---
# Copyright 2018 widdix GmbH
#
# 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.
AWSTemplateFormatVersion: '2010-09-09'
Description: 'VPC: highly available SSH bastion host/instance, a cloudonaut.io template'
Metadata:
  'AWS::CloudFormation::Interface':
    ParameterGroups:
    - Label:
        default: 'Parent Stacks'
      Parameters:
      - ParentVPCStack
      - ParentAlertStack
      - ParentZoneStack
    - Label:
        default: 'EC2 Parameters'
      Parameters:
      - InstanceType
      - KeyName
      - IAMUserSSHAccess
      - SystemsManagerAccess
      - LogsRetentionInDays
      - SubDomainNameWithDot
      - ManagedPolicyArns
    - Label:
        default: 'Permission Parameters'
      Parameters:
      - PermissionsBoundary
Parameters:
  ParentVPCStack:
    Description: 'Stack name of parent VPC stack based on vpc/vpc-*azs.yaml template.'
    Type: String
  ParentAlertStack:
    Description: 'Optional but recommended stack name of parent alert stack based on operations/alert.yaml template.'
    Type: String
    Default: ''
  ParentZoneStack:
    Description: 'Optional stack name of parent zone stack based on vpc/zone-*.yaml template.'
    Type: String
    Default: ''
  PermissionsBoundary:
    Description: 'Optional ARN for a policy that will be used as the permission boundary for all roles created by this template.'
    Type: String
    Default: ''
  KeyName:
    Description: 'Optional key pair of the ec2-user to establish a SSH connection to the SSH bastion host/instance.'
    Type: String
    Default: ''
  IAMUserSSHAccess:
    Description: 'Synchronize public keys of IAM users to enable personalized SSH access (Doc: https://cloudonaut.io/manage-aws-ec2-ssh-access-with-iam/).'
    Type: String
    Default: false
    AllowedValues:
    - true
    - false
  SystemsManagerAccess:
    Description: 'Enable AWS Systems Manager agent and authorization.'
    Type: String
    Default: true
    AllowedValues:
    - true
    - false
  InstanceType:
    Description: 'Instance type of the SSH bastion host/instance.'
    Type: String
    Default: 't2.nano'
  LogsRetentionInDays:
    Description: 'Specifies the number of days you want to retain log events.'
    Type: Number
    Default: 14
    AllowedValues: [1, 3, 5, 7, 14, 30, 60, 90, 120, 150, 180, 365, 400, 545, 731, 1827, 3653]
  SubDomainNameWithDot:
    Description: 'Name that is used to create the DNS entry with trailing dot, e.g. §{SubDomainNameWithDot}§{HostedZoneName}. Leave blank for naked (or apex and bare) domain. Requires ParentZoneStack parameter!'
    Type: String
    Default: 'ssh.'
  ManagedPolicyArns:
    Description: 'Optional comma-delimited list of IAM managed policy ARNs to attach to the instance''s IAM role'
    Type: String
    Default: ''
Mappings:
  RegionMap:
    'ap-south-2':
      AMI: 'ami-0ab51832ad0357955'
    'ap-south-1':
      AMI: 'ami-0d6eab68a2aa4419b'
    'eu-south-1':
      AMI: 'ami-0c17f1490200f1b98'
    'eu-south-2':
      AMI: 'ami-0a8f09e218768d19d'
    'me-central-1':
      AMI: 'ami-07e91783d8a16e1f2'
    'il-central-1':
      AMI: 'ami-04ee358ea26a28621'
    'ca-central-1':
      AMI: 'ami-06aa9bf8acd13295e'
    'eu-central-1':
      AMI: 'ami-0b26dd07b92ba60b5'
    'eu-central-2':
      AMI: 'ami-08b6d5c9e5f65725a'
    'us-west-1':
      AMI: 'ami-0b301738029f9f48e'
    'us-west-2':
      AMI: 'ami-076e3756930a93fbb'
    'af-south-1':
      AMI: 'ami-04c86004365f50376'
    'eu-north-1':
      AMI: 'ami-05668410ca8bbacb3'
    'eu-west-3':
      AMI: 'ami-0e240183bb3096e67'
    'eu-west-2':
      AMI: 'ami-08ceb58c67626d304'
    'eu-west-1':
      AMI: 'ami-064857453c447bed5'
    'ap-northeast-3':
      AMI: 'ami-0806b1119517557f0'
    'ap-northeast-2':
      AMI: 'ami-00252d017d66f9cdd'
    'me-south-1':
      AMI: 'ami-05263463386d9b3a5'
    'ap-northeast-1':
      AMI: 'ami-08aa3b50f80805e20'
    'sa-east-1':
      AMI: 'ami-0cd4a737dad460342'
    'ap-east-1':
      AMI: 'ami-0a97c2677505cda75'
    'ca-west-1':
      AMI: 'ami-01c7593ec24183809'
    'ap-southeast-1':
      AMI: 'ami-083068d1edaf8af18'
    'ap-southeast-2':
      AMI: 'ami-094ff1d74ab636074'
    'ap-southeast-3':
      AMI: 'ami-08990191cc9b187ac'
    'ap-southeast-4':
      AMI: 'ami-0d9704c67691a5331'
    'us-east-1':
      AMI: 'ami-046eeba8a7f7bbefd'
    'us-east-2':
      AMI: 'ami-02c4f64d0cbab1731'
Conditions:
  HasPermissionsBoundary: !Not [!Equals [!Ref PermissionsBoundary, '']]
  HasKeyName: !Not [!Equals [!Ref KeyName, '']]
  HasIAMUserSSHAccess: !Equals [!Ref IAMUserSSHAccess, 'true']
  HasSystemsManagerAccess: !Equals [!Ref SystemsManagerAccess, 'true']
  HasAlertTopic: !Not [!Equals [!Ref ParentAlertStack, '']]
  HasZone: !Not [!Equals [!Ref ParentZoneStack, '']]
  HasManagedPolicyArns: !Not [!Equals [!Ref ManagedPolicyArns, '']]
Resources:
  RecordSet:
    Condition: HasZone
    Type: 'AWS::Route53::RecordSet'
    Properties:
      HostedZoneId: {'Fn::ImportValue': !Sub '${ParentZoneStack}-HostedZoneId'}
      Name: !Sub
      - '${SubDomainNameWithDot}${HostedZoneName}'
      - SubDomainNameWithDot: !Ref SubDomainNameWithDot
        HostedZoneName: {'Fn::ImportValue': !Sub '${ParentZoneStack}-HostedZoneName'}
      ResourceRecords:
      - !Ref EIP
      TTL: 60
      Type: A
  EIP:
    Type: 'AWS::EC2::EIP'
    Properties:
      Domain: vpc
  Logs:
    Type: 'AWS::Logs::LogGroup'
    Properties:
      RetentionInDays: !Ref LogsRetentionInDays
  SecurityGroup:
    Type: 'AWS::EC2::SecurityGroup'
    Properties:
      GroupDescription: !Ref 'AWS::StackName'
      SecurityGroupIngress:
      - IpProtocol: tcp
        FromPort: 22
        ToPort: 22
        CidrIp: '0.0.0.0/0'
      VpcId: {'Fn::ImportValue': !Sub '${ParentVPCStack}-VPC'}
  InstanceProfile:
    Type: 'AWS::IAM::InstanceProfile'
    Properties:
      Roles:
      - !Ref IAMRole
  IAMRole:
    Type: 'AWS::IAM::Role'
    Properties:
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
        - Effect: Allow
          Principal:
            Service: 'ec2.amazonaws.com'
          Action: 'sts:AssumeRole'
      ManagedPolicyArns: !If [HasManagedPolicyArns, !Split [',', !Ref ManagedPolicyArns], !Ref 'AWS::NoValue']
      PermissionsBoundary: !If [HasPermissionsBoundary, !Ref PermissionsBoundary, !Ref 'AWS::NoValue']
      Policies:
      - !If
        - HasSystemsManagerAccess
        - PolicyName: ssm
          PolicyDocument:
            Version: '2012-10-17'
            Statement:
            - Effect: Allow
              Action:
              - 'ssmmessages:*' # SSM Agent by https://docs.aws.amazon.com/systems-manager/latest/userguide/systems-manager-setting-up-messageAPIs.html
              - 'ssm:UpdateInstanceInformation' # SSM agent by https://docs.aws.amazon.com/systems-manager/latest/userguide/systems-manager-setting-up-messageAPIs.html
              - 'ec2messages:*' # SSM Session Manager by https://docs.aws.amazon.com/systems-manager/latest/userguide/systems-manager-setting-up-messageAPIs.html
              Resource: '*'
        - !Ref 'AWS::NoValue'
      - PolicyName: 'ec2'
        PolicyDocument:
          Version: '2012-10-17'
          Statement:
          - Effect: Allow
            Action:
            - 'ec2:AssociateAddress'
            Resource:
            - '*'
      - PolicyName: logs
        PolicyDocument:
          Version: '2012-10-17'
          Statement:
          - Effect: Allow
            Action:
            - 'logs:CreateLogGroup'
            - 'logs:CreateLogStream'
            - 'logs:PutLogEvents'
            - 'logs:DescribeLogStreams'
            Resource: !GetAtt 'Logs.Arn'
  IAMPolicySSHAccess:
    Type: 'AWS::IAM::Policy'
    Condition: HasIAMUserSSHAccess
    Properties:
      Roles:
      - !Ref IAMRole
      PolicyName: iam
      PolicyDocument:
        Version: '2012-10-17'
        Statement:
        - Effect: Allow
          Action:
          - 'iam:ListUsers'
          Resource:
          - '*'
        - Effect: Allow
          Action:
          - 'iam:ListSSHPublicKeys'
          - 'iam:GetSSHPublicKey'
          Resource:
          - !Sub 'arn:aws:iam::${AWS::AccountId}:user/*'
  LaunchTemplate:
    Type: 'AWS::EC2::LaunchTemplate'
    Metadata:
      'AWS::CloudFormation::Init':
        configSets:
          default: !If [HasIAMUserSSHAccess, [awslogs, ssh-access, config], [awslogs, config]]
        awslogs:
          packages:
            yum:
              awslogs: []
          files:
            '/etc/awslogs/awscli.conf':
              content: !Sub |
                [default]
                region = ${AWS::Region}
                [plugins]
                cwlogs = cwlogs
              mode: '000644'
              owner: root
              group: root
            '/etc/awslogs/awslogs.conf':
              content: !Sub |
                [general]
                state_file = /var/lib/awslogs/agent-state
                [/var/log/amazon/ssm/amazon-ssm-agent.log]
                datetime_format = %Y-%m-%d %H:%M:%S
                file = /var/log/amazon/ssm/amazon-ssm-agent.log
                log_stream_name = {instance_id}/var/log/amazon/ssm/amazon-ssm-agent.log
                log_group_name = ${Logs}
                [/var/log/amazon/ssm/errors.log]
                datetime_format = %Y-%m-%d %H:%M:%S
                file = /var/log/amazon/ssm/errors.log
                log_stream_name = {instance_id}/var/log/amazon/ssm/errors.log
                log_group_name = ${Logs}
                [/var/log/audit/audit.log]
                file = /var/log/audit/audit.log
                log_stream_name = {instance_id}/var/log/audit/audit.log
                log_group_name = ${Logs}
                [/var/log/awslogs.log]
                datetime_format = %Y-%m-%d %H:%M:%S
                file = /var/log/awslogs.log
                log_stream_name = {instance_id}/var/log/awslogs.log
                log_group_name = ${Logs}
                [/var/log/boot.log]
                file = /var/log/boot.log
                log_stream_name = {instance_id}/var/log/boot.log
                log_group_name = ${Logs}
                [/var/log/cfn-hup.log]
                datetime_format = %Y-%m-%d %H:%M:%S
                file = /var/log/cfn-hup.log
                log_stream_name = {instance_id}/var/log/cfn-hup.log
                log_group_name = ${Logs}
                [/var/log/cfn-init-cmd.log]
                datetime_format = %Y-%m-%d %H:%M:%S
                file = /var/log/cfn-init-cmd.log
                log_stream_name = {instance_id}/var/log/cfn-init-cmd.log
                log_group_name = ${Logs}
                [/var/log/cfn-init.log]
                datetime_format = %Y-%m-%d %H:%M:%S
                file = /var/log/cfn-init.log
                log_stream_name = {instance_id}/var/log/cfn-init.log
                log_group_name = ${Logs}
                [/var/log/cfn-wire.log]
                datetime_format = %Y-%m-%d %H:%M:%S
                file = /var/log/cfn-wire.log
                log_stream_name = {instance_id}/var/log/cfn-wire.log
                log_group_name = ${Logs}
                [/var/log/cloud-init-output.log]
                file = /var/log/cloud-init-output.log
                log_stream_name = {instance_id}/var/log/cloud-init-output.log
                log_group_name = ${Logs}
                [/var/log/cloud-init.log]
                datetime_format = %b %d %H:%M:%S
                file = /var/log/cloud-init.log
                log_stream_name = {instance_id}/var/log/cloud-init.log
                log_group_name = ${Logs}
                [/var/log/cron]
                datetime_format = %b %d %H:%M:%S
                file = /var/log/cron
                log_stream_name = {instance_id}/var/log/cron
                log_group_name = ${Logs}
                [/var/log/dmesg]
                file = /var/log/dmesg
                log_stream_name = {instance_id}/var/log/dmesg
                log_group_name = ${Logs}
                [/var/log/grubby_prune_debug]
                file = /var/log/grubby_prune_debug
                log_stream_name = {instance_id}/var/log/grubby_prune_debug
                log_group_name = ${Logs}
                [/var/log/maillog]
                datetime_format = %b %d %H:%M:%S
                file = /var/log/maillog
                log_stream_name = {instance_id}/var/log/maillog
                log_group_name = ${Logs}
                [/var/log/messages]
                datetime_format = %b %d %H:%M:%S
                file = /var/log/messages
                log_stream_name = {instance_id}/var/log/messages
                log_group_name = ${Logs}
                [/var/log/secure]
                datetime_format = %b %d %H:%M:%S
                file = /var/log/secure
                log_stream_name = {instance_id}/var/log/secure
                log_group_name = ${Logs}
                [/var/log/yum.log]
                datetime_format = %b %d %H:%M:%S
                file = /var/log/yum.log
                log_stream_name = {instance_id}/var/log/yum.log
                log_group_name = ${Logs}
              mode: '000644'
              owner: root
              group: root
          services:
            sysvinit:
              awslogsd:
                enabled: true
                ensureRunning: true
                packages:
                  yum:
                  - awslogs
                files:
                - '/etc/awslogs/awslogs.conf'
                - '/etc/awslogs/awscli.conf'
        ssh-access:
          files:
            '/opt/authorized_keys_command.sh':
              content: |
                #!/bin/bash -e
                if [ -z "$1" ]; then
                  exit 1
                fi
                UnsaveUserName="$1"
                UnsaveUserName=${UnsaveUserName//".plus."/"+"}
                UnsaveUserName=${UnsaveUserName//".equal."/"="}
                UnsaveUserName=${UnsaveUserName//".comma."/","}
                UnsaveUserName=${UnsaveUserName//".at."/"@"}
                aws iam list-ssh-public-keys --user-name "$UnsaveUserName" --query "SSHPublicKeys[?Status == 'Active'].[SSHPublicKeyId]" --output text | while read -r KeyId; do
                  aws iam get-ssh-public-key --user-name "$UnsaveUserName" --ssh-public-key-id "$KeyId" --encoding SSH --query "SSHPublicKey.SSHPublicKeyBody" --output text
                done
              mode: '000755'
              owner: root
              group: root
            '/opt/import_users.sh':
              content: |
                #!/bin/bash -e
                aws iam list-users --query "Users[].[UserName]" --output text | while read User; do
                  SaveUserName="$User"
                  SaveUserName=${SaveUserName//"+"/".plus."}
                  SaveUserName=${SaveUserName//"="/".equal."}
                  SaveUserName=${SaveUserName//","/".comma."}
                  SaveUserName=${SaveUserName//"@"/".at."}
                  if [ "${#SaveUserName}" -le "32" ]; then
                    if ! id -u "$SaveUserName" > /dev/null 2>&1; then
                      # don't grant sudo rights on bastion host!
                      /usr/sbin/useradd "$SaveUserName"
                    fi
                  else
                    echo "Can not import IAM user ${SaveUserName}. User name is longer than 32 characters."
                  fi
                done
              mode: '000755'
              owner: root
              group: root
            '/etc/cron.d/import_users':
              content: |
                */10 * * * * root /opt/import_users.sh
              mode: '000644'
              owner: root
              group: root
          commands:
            'a_configure_sshd_command':
              command: 'sed -e ''/AuthorizedKeysCommand / s/^#*/#/'' -i /etc/ssh/sshd_config; echo -e ''\nAuthorizedKeysCommand /opt/authorized_keys_command.sh'' >> /etc/ssh/sshd_config'
              test: '! grep -q ''^AuthorizedKeysCommand /opt/authorized_keys_command.sh'' /etc/ssh/sshd_config'
            'b_configure_sshd_commanduser':
              command: 'sed -e ''/AuthorizedKeysCommandUser / s/^#*/#/'' -i /etc/ssh/sshd_config; echo -e ''\nAuthorizedKeysCommandUser nobody'' >> /etc/ssh/sshd_config'
              test: '! grep -q ''^AuthorizedKeysCommandUser nobody'' /etc/ssh/sshd_config'
            'c_import_users':
              command: './import_users.sh'
              cwd: '/opt'
          services:
            sysvinit:
              sshd:
                enabled: true
                ensureRunning: true
                commands:
                - 'a_configure_sshd_command'
                - 'b_configure_sshd_commanduser'
        config:
          packages:
            yum:
              mariadb: []
          files:
            '/etc/cfn/cfn-hup.conf':
              content: !Sub |
                [main]
                stack=${AWS::StackId}
                region=${AWS::Region}
                interval=1
              mode: '000400'
              owner: root
              group: root
            '/etc/cfn/hooks.d/cfn-auto-reloader.conf':
              content: !Sub |
                [cfn-auto-reloader-hook]
                triggers=post.update
                path=Resources.LaunchTemplate.Metadata.AWS::CloudFormation::Init
                action=/opt/aws/bin/cfn-init --verbose --stack=${AWS::StackName} --region=${AWS::Region} --resource=LaunchTemplate
                runas=root
          services:
            sysvinit:
              cfn-hup:
                enabled: true
                ensureRunning: true
                files:
                - '/etc/cfn/cfn-hup.conf'
                - '/etc/cfn/hooks.d/cfn-auto-reloader.conf'
              amazon-ssm-agent:
                enabled: !If [HasSystemsManagerAccess, true, false]
                ensureRunning: !If [HasSystemsManagerAccess, true, false]
    Properties:
      LaunchTemplateData:
        BlockDeviceMappings:
        - DeviceName: '/dev/xvda'
          Ebs:
            Encrypted: true
            VolumeType: gp3
        IamInstanceProfile:
          Name: !Ref InstanceProfile
        ImageId: !FindInMap [RegionMap, !Ref 'AWS::Region', AMI]
        InstanceType: !Ref InstanceType
        KeyName: !If [HasKeyName, !Ref KeyName, !Ref 'AWS::NoValue']
        MetadataOptions:
          HttpTokens: required
        NetworkInterfaces:
        - AssociatePublicIpAddress: true
          DeviceIndex: 0
          Groups:
          - !Ref SecurityGroup
        UserData:
          'Fn::Base64': !Sub |
            #!/bin/bash -ex
            trap '/opt/aws/bin/cfn-signal -e 1 --stack ${AWS::StackName} --resource AutoScalingGroup --region ${AWS::Region}' ERR
            TOKEN=$(curl --silent --max-time 60 -X PUT http://169.254.169.254/latest/api/token -H "X-aws-ec2-metadata-token-ttl-seconds: 30")
            INSTANCEID=$(curl --silent --max-time 60 -H "X-aws-ec2-metadata-token: $TOKEN" http://169.254.169.254/latest/meta-data/instance-id)
            aws --region ${AWS::Region} ec2 associate-address --instance-id $INSTANCEID --allocation-id ${EIP.AllocationId}
            /opt/aws/bin/cfn-init -v --stack ${AWS::StackName} --resource LaunchTemplate --region ${AWS::Region}
            /opt/aws/bin/cfn-signal -e 0 --stack ${AWS::StackName} --resource AutoScalingGroup --region ${AWS::Region}
  AutoScalingGroup:
    Type: 'AWS::AutoScaling::AutoScalingGroup'
    Properties:
      LaunchTemplate:
        LaunchTemplateId: !Ref LaunchTemplate
        Version: !GetAtt 'LaunchTemplate.LatestVersionNumber'
      MaxSize: '1'
      MinSize: '1'
      Tags:
      - Key: Name
        Value: !Sub
        - 'SSH bastion host/instance ${CidrBlock}'
        - CidrBlock: {'Fn::ImportValue': !Sub '${ParentVPCStack}-CidrBlock'}
        PropagateAtLaunch: true
      NotificationConfigurations: !If
      - HasAlertTopic
      - - NotificationTypes:
          - 'autoscaling:EC2_INSTANCE_LAUNCH_ERROR'
          - 'autoscaling:EC2_INSTANCE_TERMINATE_ERROR'
          TopicARN: {'Fn::ImportValue': !Sub '${ParentAlertStack}-TopicARN'}
      - []
      VPCZoneIdentifier: !Split [',', {'Fn::ImportValue': !Sub '${ParentVPCStack}-SubnetsPublic'}]
    CreationPolicy:
      ResourceSignal:
        Count: 1
        Timeout: PT10M
    UpdatePolicy:
      AutoScalingRollingUpdate:
        PauseTime: PT10M
        SuspendProcesses:
        - HealthCheck
        - ReplaceUnhealthy
        - AZRebalance
        - AlarmNotification
        - ScheduledActions
        WaitOnResourceSignals: true
  CPUTooHighAlarm:
    Condition: HasAlertTopic
    Type: 'AWS::CloudWatch::Alarm'
    Properties:
      AlarmDescription: 'Average CPU utilization over last 10 minutes higher than 80%'
      Namespace: 'AWS/EC2'
      MetricName: CPUUtilization
      Statistic: Average
      Period: 600
      EvaluationPeriods: 1
      ComparisonOperator: GreaterThanThreshold
      Threshold: 80
      AlarmActions:
      - {'Fn::ImportValue': !Sub '${ParentAlertStack}-TopicARN'}
      Dimensions:
      - Name: AutoScalingGroupName
        Value: !Ref AutoScalingGroup
Outputs:
  TemplateID:
    Description: 'cloudonaut.io template id.'
    Value: 'vpc/vpc-ssh-bastion'
  TemplateVersion:
    Description: 'cloudonaut.io template version.'
    Value: '__VERSION__'
  StackName:
    Description: 'Stack name.'
    Value: !Sub '${AWS::StackName}'
  SecurityGroup:
    Description: 'Use this Security Group to reference incoming traffic from the SSH bastion host/instance.'
    Value: !Ref SecurityGroup
    Export:
      Name: !Sub '${AWS::StackName}-SecurityGroup'
  IPAddress:
    Description: 'The public IP address of the SSH bastion host/instance.'
    Value: !Ref EIP
    Export:
      Name: !Sub '${AWS::StackName}-IPAddress'