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
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: ''
  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.'
Mappings:
  RegionMap:
    'ap-south-1':
      AMI: 'ami-0937dcc711d38ef3f'
    'eu-west-3':
      AMI: 'ami-0854d53ce963f69d8'
    'eu-north-1':
      AMI: 'ami-6d27a913'
    'eu-west-2':
      AMI: 'ami-0664a710233d7c148'
    'eu-west-1':
      AMI: 'ami-0fad7378adf284ce0'
    'ap-northeast-2':
      AMI: 'ami-018a9a930060d38aa'
    'ap-northeast-1':
      AMI: 'ami-0d7ed3ddb85b521a6'
    'sa-east-1':
      AMI: 'ami-0b04450959586da29'
    'ca-central-1':
      AMI: 'ami-0de8b8e4bc1f125fe'
    'ap-southeast-1':
      AMI: 'ami-04677bdaa3c2b6e24'
    'ap-southeast-2':
      AMI: 'ami-0c9d48b5db609ad6e'
    'eu-central-1':
      AMI: 'ami-0eaec5838478eb0ba'
    'us-east-1':
      AMI: 'ami-035be7bafff33b6b6'
    'us-east-2':
      AMI: 'ami-04328208f4f0cf1fe'
    'us-west-1':
      AMI: 'ami-0799ad445b5727125'
    'us-west-2':
      AMI: 'ami-032509850cf9ee54e'
Conditions:
  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, '']]
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 '${ParentVPCStack}-VPC'}
  InstanceProfile:
    Type: 'AWS::IAM::InstanceProfile'
    Properties:
      Path: '/'
      Roles:
      - !Ref IAMRole
  IAMRole:
    Type: 'AWS::IAM::Role'
    Properties:
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
        - Effect: Allow
          Principal:
            Service:
            - 'ec2.amazonaws.com'
          Action:
          - 'sts:AssumeRole'
      Path: '/'
      ManagedPolicyArns: !If [HasSystemsManagerAccess, ['arn:aws:iam::aws:policy/service-role/AmazonEC2RoleforSSM'], []] # TODO get rid of managed policy
      Policies:
      - PolicyName: 'ec2'
        PolicyDocument:
          Version: '2012-10-17'
          Statement:
          - Effect: Allow
            Action:
            - 'ec2:AssociateAddress'
            Resource:
            - '*'
      - PolicyName: logs
        PolicyDocument:
          Version: '2012-10-17'
          Statement:
          - Effect: Allow
            Action:
            - 'logs:CreateLogStream'
            - 'logs:PutLogEvents'
            - 'logs:DescribeLogStreams'
            Resource: !GetAtt 'Logs.Arn'
  IAMPolicySSHAccess:
    Type: 'AWS::IAM::Policy'
    Condition: HasIAMUserSSHAccess
    Properties:
      Roles:
      - !Ref IAMRole
      PolicyName: iam
      PolicyDocument:
        Version: '2012-10-17'
        Statement:
        - Effect: Allow
          Action:
          - 'iam:ListUsers'
          Resource:
          - '*'
        - Effect: Allow
          Action:
          - 'iam:ListSSHPublicKeys'
          - 'iam:GetSSHPublicKey'
          Resource:
          - !Sub 'arn:aws:iam::${AWS::AccountId}:user/*'
  LaunchConfiguration:
    Type: 'AWS::AutoScaling::LaunchConfiguration'
    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=${AWS::Region}
                interval=1
              mode: '000400'
              owner: root
              group: root
            '/etc/cfn/hooks.d/cfn-auto-reloader.conf':
              content: !Sub |
                [cfn-auto-reloader-hook]
                triggers=post.update
                path=Resources.LaunchConfiguration.Metadata.AWS::CloudFormation::Init
                action=/opt/aws/bin/cfn-init --verbose --stack=${AWS::StackName} --region=${AWS::Region} --resource=LaunchConfiguration
                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:
      AssociatePublicIpAddress: true
      EbsOptimized: false
      IamInstanceProfile: !Ref InstanceProfile
      ImageId: !FindInMap [RegionMap, !Ref 'AWS::Region', AMI]
      InstanceType: !Ref InstanceType
      SecurityGroups:
      - !Ref SecurityGroup
      KeyName: !If [HasKeyName, !Ref KeyName, !Ref 'AWS::NoValue']
      UserData:
        'Fn::Base64': !Sub |
          #!/bin/bash -ex
          trap '/opt/aws/bin/cfn-signal -e 1 --stack ${AWS::StackName} --resource AutoScalingGroup --region ${AWS::Region}' ERR
          INSTANCEID=$(curl -s -m 60 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 LaunchConfiguration --region ${AWS::Region}
          /opt/aws/bin/cfn-signal -e 0 --stack ${AWS::StackName} --resource AutoScalingGroup --region ${AWS::Region}
  AutoScalingGroup:
    Type: 'AWS::AutoScaling::AutoScalingGroup'
    Properties:
      LaunchConfigurationName: !Ref LaunchConfiguration
      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'