I am dealing with a STIG image and part of the STIG is that /var has a noexec flag on it.

I am trying to use EC2 Image Builder to build out the STIG AMIs to be used for our deployments. Currently I am doing this manually.

When I use EC2 Image Builder I get errors:

2024-09-24 19:25:24.3374 INFO [ssm-agent-worker] [MessageService] [MGSInteractor] Sending reply {
  "additionalInfo": {
    "agent": {
      "lang": "en-US",
      "name": "amazon-ssm-agent",
      "os": "",
      "osver": "1",
      "ver": "3.3.859.0"
    },
    "dateTime": "2024-09-24T19:25:24.337Z",
    "runId": "",
    "runtimeStatusCounts": {
      "Failed": 1
    }
  },
  "documentStatus": "Failed",
  "documentTraceOutput": "",
  "runtimeStatus": {
    "aws:runShellScript": {
      "status": "Failed",
      "code": 126,
      "name": "aws:runShellScript",
      "output": "n----------ERROR-------nsh: /var/lib/amazon/ssm/i-0adb629670a162125/document/opt/ec2-image-builder-ssm-working-dir/f56cb6c1-6608-41c7-bc00-02783ba30c4e/awsrunShellScript/0.awsrunShellScript/_script.sh: Permission deniednfailed to run commands: exit status 126",
      "startDateTime": "2024-09-24T19:25:24.332Z",
      "endDateTime": "2024-09-24T19:25:24.336Z",
      "outputS3BucketName": "",
      "outputS3KeyPrefix": "",
      "stepName": "",
      "standardOutput": "",
      "standardError": "sh: /var/lib/amazon/ssm/i-0adb629670a162125/document/opt/ec2-image-builder-ssm-working-dir/f56cb6c1-6608-41c7-bc00-02783ba30c4e/awsrunShellScript/0.awsrunShellScript/_script.sh: Permission deniednfailed to run commands: exit status 126"
    }
  }
}

This is expected as /var has no executable permissions, per the STIG.

I wanted to try to install this agent into a custom location but I cannot figure out how to do this at all.

I even tried configuring the json file to point to a new directory but this seems to just be ignored completely.

              sudo cp /etc/amazon/ssm/amazon-ssm-agent.json.template /etc/amazon/ssm/amazon-ssm-agent.json
              sudo sed -i 's|"OrchestrationRootDir": ""|"OrchestrationRootDir": "/opt/ec2-image-builder-ssm-working-dir"|' /etc/amazon/ssm/amazon-ssm-agent.json
              sudo sed -i 's|"Region": ""|"Region": "${AWS::Region}"|' /etc/amazon/ssm/amazon-ssm-agent.json

I even tried this (found this online):

sudo dnf install --installroot=/opt/ec2-image-builder-ssm-working-dir --nogpgcheck amazon-ssm-agent.rpm

But that just failed to install at all.

No matter what I try, it is always installed in the /var directory so EC2 Image Builder always fails.

This has been a bit frustrating so I am reaching out here to see if anyone can give me any insight or other solutions.

This is the part of the CloudFormaiton template that I am working with:

TenableSecurityCenterImageRecipe:
    Type: "AWS::ImageBuilder::ImageRecipe"
    Properties:
      Name: !Sub "${AWS::StackName}-TenableSecurityCenterRecipe"
      Version: !Ref RecipeVersion
      Components:
        - ComponentArn:
            Fn::ImportValue: !Sub "${Ec2BuilderComponentsStackName}-FixStorageConfigurationComponent-Arn"
        - ComponentArn:
            Fn::ImportValue: !Sub "${Ec2BuilderComponentsStackName}-UpdateStigYumComponent-Arn"
        - ComponentArn:
            Fn::ImportValue: !Sub "${Ec2BuilderComponentsStackName}-CloudWatchAgentComponent-Arn"
        - ComponentArn:
            Fn::ImportValue: !Sub "${Ec2BuilderComponentsStackName}-AWSCLIInstallationComponent-Arn"
        - ComponentArn:
            Fn::ImportValue: !Sub "${Ec2BuilderComponentsStackName}-SuricataInstallationComponent-Arn"
        - ComponentArn: !Ref TenableSecurityCenterComponent
      ParentImage: !Ref AmiId
      AdditionalInstanceConfiguration:
        UserDataOverride:
          Fn::Base64:
            Fn::Sub: |
              #!/bin/bash

              # Fix STIG issue with noexec in /var directory
              sudo mkdir -p /opt/ec2-image-builder-ssm-working-dir

              sudo chown -R root:root /opt/ec2-image-builder-ssm-working-dir
              sudo chmod 750 /opt/ec2-image-builder-ssm-working-dir

              sudo dnf install --nogpgcheck -y 

              # fapolicyd rules for SSM agent
              sudo fapolicyd-cli --file add /usr/bin/amazon-ssm-agent --trust-file ssm
              sudo fapolicyd-cli --file add /usr/bin/ssm-session-worker --trust-file ssm
              sudo fapolicyd-cli --file add /usr/bin/ssm-cli --trust-file ssm
              sudo fapolicyd-cli --file add /var/lib/amazon/ssm --trust-file ssm
              sudo fapolicyd-cli --file add /opt/ec2-image-builder-ssm-working-dir --trust-file ssm

              sudo fagenrules --load
              sudo systemctl restart fapolicyd

              sudo systemctl enable amazon-ssm-agent
              sudo systemctl restart amazon-ssm-agent

              # Build our config once the files are in place
              sudo cp /etc/amazon/ssm/amazon-ssm-agent.json.template /etc/amazon/ssm/amazon-ssm-agent.json
              sudo sed -i 's|"OrchestrationRootDir": ""|"OrchestrationRootDir": "/opt/ec2-image-builder-ssm-working-dir"|' /etc/amazon/ssm/amazon-ssm-agent.json
              sudo sed -i 's|"Region": ""|"Region": "${AWS::Region}"|' /etc/amazon/ssm/amazon-ssm-agent.json

              sudo systemctl restart amazon-ssm-agent

      WorkingDirectory: "/opt/ec2-image-builder-ssm-working-dir" # Set to a STIG-compliant directory
      BlockDeviceMappings:
        - DeviceName: "/dev/sda1"
          Ebs:
            VolumeType: gp3
            VolumeSize: 150
            DeleteOnTermination: true
        - DeviceName: "/dev/xvdh"
          Ebs:
            VolumeType: gp3
            VolumeSize: 30
            DeleteOnTermination: true
        - DeviceName: "/dev/xvdl"
          Ebs:
            VolumeType: gp3
            VolumeSize: 2
            DeleteOnTermination: true
        - DeviceName: "/dev/xvdx"
          Ebs:
            VolumeType: gp3
            VolumeSize: 1
            DeleteOnTermination: true
        - DeviceName: "/dev/xvdz"
          Ebs:
            VolumeType: gp3
            VolumeSize: 1
            DeleteOnTermination: true

Thanks