@cyclonedx/cdxgen/data/rules/rootfs-hardening.yaml

Creates CycloneDX Software Bill of Materials (SBOM) from source or container image

# Rootfs and Offline Host Hardening Rules
# Category: rootfs-hardening
# Evaluates repository trust, trust anchors, privileged helpers, and service execution paths

- id: RFS-001
  name: "Enabled OS repository uses plaintext HTTP transport"
  description: "Plain HTTP package repositories weaken integrity guarantees and make mirror tampering easier when network controls are absent."
  severity: high
  category: rootfs-hardening
  dry-run-support: full
  condition: |
    components[
      type = 'data'
      and $hasProp($, 'cdx:os:repo:type')
      and $safeStr($prop($, 'cdx:os:repo:enabled')) = 'true'
      and $startsWith($lowercase($safeStr($prop($, 'cdx:os:repo:url'))), 'http://')
    ]
  location: |
    {
      "bomRef": $."bom-ref",
      "purl": purl
    }
  message: "Repository '{{ name }}' is enabled and still uses plaintext HTTP: {{ $prop($, 'cdx:os:repo:url') }}"
  mitigation: "Move package sources to HTTPS or a trusted local mirror protected by authenticated transport and repository signing."
  evidence: |
    {
      "sourceFile": $prop($, 'SrcFile'),
      "repoType": $prop($, 'cdx:os:repo:type'),
      "repoUrl": $prop($, 'cdx:os:repo:url')
    }

- id: RFS-002
  name: "YUM repository has package signature checks disabled"
  description: "Disabling gpgcheck in a configured YUM repository removes a core package authenticity control."
  severity: critical
  category: rootfs-hardening
  dry-run-support: full
  condition: |
    components[
      type = 'data'
      and $safeStr($prop($, 'cdx:os:repo:type')) = 'yum-repository'
      and $safeStr($prop($, 'cdx:os:repo:enabled')) = 'true'
      and $safeStr($prop($, 'cdx:os:repo:gpgcheck')) = '0'
    ]
  location: |
    {
      "bomRef": $."bom-ref",
      "purl": purl
    }
  message: "YUM repository '{{ name }}' is enabled with gpgcheck disabled"
  mitigation: "Enable gpgcheck, pin the expected signing keys, and review recent repository changes before continuing to trust packages from this source."
  evidence: |
    {
      "sourceFile": $prop($, 'SrcFile'),
      "repoUrl": $prop($, 'cdx:os:repo:url'),
      "gpgcheck": $prop($, 'cdx:os:repo:gpgcheck'),
      "gpgkey": $prop($, 'cdx:os:repo:gpgkey')
    }

- id: RFS-003
  name: "Offline trust anchor is marked expired"
  description: "Expired trust anchors inside an image or rootfs can break planned rotations and hide stale trust relationships."
  severity: high
  category: rootfs-hardening
  dry-run-support: full
  condition: |
    components[
      type = 'cryptographic-asset'
      and $safeStr(cryptoProperties.assetType) = 'related-crypto-material'
      and $safeStr(cryptoProperties.relatedCryptoMaterialProperties.state) = 'expired'
    ]
  location: |
    {
      "bomRef": $."bom-ref"
    }
  message: "Trust anchor '{{ name }}' is marked expired and should be reviewed"
  mitigation: "Remove stale keys, replace expired trust anchors, and confirm the remaining repository trust chain matches approved policy."
  evidence: |
    {
      "path": $prop($, 'SrcFile'),
      "trustDomain": $prop($, 'cdx:crypto:trustDomain'),
      "keyId": $prop($, 'cdx:crypto:keyId'),
      "expiresAt": $prop($, 'cdx:crypto:expiresAt')
    }

- id: RFS-004
  name: "Offline image retains setuid GTFOBins execution helper"
  description: "Setuid GTFOBins-capable binaries increase privilege-escalation exposure inside rootfs and golden image baselines."
  severity: critical
  category: rootfs-hardening
  dry-run-support: full
  condition: |
    components[
      type = 'file'
      and (
        $prop($, 'internal:has_setuid') = 'true'
        or $prop($, 'internal:has_setgid') = 'true'
      )
      and $prop($, 'cdx:gtfobins:matched') = 'true'
      and (
        $listContains($prop($, 'cdx:gtfobins:functions'), 'shell')
        or $listContains($prop($, 'cdx:gtfobins:functions'), 'command')
        or $listContains($prop($, 'cdx:gtfobins:functions'), 'library-load')
      )
    ]
  location: |
    {
      "bomRef": $."bom-ref",
      "purl": purl
    }
  message: "Privileged helper '{{ name }}' keeps GTFOBins execution capability in the offline image"
  mitigation: "Remove unnecessary setuid or setgid bits, replace the helper with a safer alternative, or justify and baseline the exposure explicitly."
  evidence: |
    {
      "path": $prop($, 'SrcFile'),
      "functions": $prop($, 'cdx:gtfobins:functions'),
      "contexts": $prop($, 'cdx:gtfobins:contexts'),
      "riskTags": $prop($, 'cdx:gtfobins:riskTags')
    }

- id: RFS-005
  name: "Offline service executes from writable or temporary path"
  description: "Services pointing at writable or temporary paths are a strong persistence and drift signal in base images and offline hosts."
  severity: critical
  category: rootfs-hardening
  dry-run-support: full
  condition: |
    $auditServices($)[
      $contains($lowercase($safeStr($prop($, 'cdx:service:ExecStart'))), '/tmp/')
      or $contains($lowercase($safeStr($prop($, 'cdx:service:ExecStart'))), '/var/tmp/')
      or $contains($lowercase($safeStr($prop($, 'cdx:service:ExecStart'))), '/dev/shm/')
      or $contains($lowercase($safeStr($prop($, 'cdx:service:ExecStart'))), '/home/')
      or $contains($lowercase($safeStr($prop($, 'cdx:service:ExecStart'))), '/run/user/')
    ]
  location: |
    {
      "bomRef": $."bom-ref"
    }
  message: "Service '{{ name }}' launches from a writable or temporary path"
  mitigation: "Relocate approved service binaries into trusted system paths and investigate any service definition that executes from writable directories."
  evidence: |
    {
      "sourceFile": $prop($, 'SrcFile'),
      "manager": $prop($, 'cdx:service:manager'),
      "execStart": $prop($, 'cdx:service:ExecStart'),
      "packageRef": $prop($, 'cdx:service:packageRef')
    }

- id: RFS-006
  name: "Offline service pre-start step fetches or shells remote content"
  description: "ExecStartPre hooks that fetch remote content or shell inline commands add bootstrap drift and weaken image reproducibility."
  severity: high
  category: rootfs-hardening
  dry-run-support: full
  condition: |
    $auditServices($)[
      (
        $contains($lowercase($safeStr($prop($, 'cdx:service:ExecStartPre'))), 'curl ')
        or $contains($lowercase($safeStr($prop($, 'cdx:service:ExecStartPre'))), 'wget ')
      )
      and (
        $contains($lowercase($safeStr($prop($, 'cdx:service:ExecStartPre'))), 'http://')
        or $contains($lowercase($safeStr($prop($, 'cdx:service:ExecStartPre'))), 'https://')
        or $contains($lowercase($safeStr($prop($, 'cdx:service:ExecStartPre'))), '| sh')
        or $contains($lowercase($safeStr($prop($, 'cdx:service:ExecStartPre'))), '| bash')
      )
    ]
  location: |
    {
      "bomRef": $."bom-ref"
    }
  message: "Service '{{ name }}' uses a remote-fetching ExecStartPre hook: {{ $prop($, 'cdx:service:ExecStartPre') }}"
  mitigation: "Move bootstrap downloads into the image build pipeline, pin artifacts, and keep service startup paths deterministic and locally sourced."
  evidence: |
    {
      "sourceFile": $prop($, 'SrcFile'),
      "manager": $prop($, 'cdx:service:manager'),
      "execStartPre": $prop($, 'cdx:service:ExecStartPre')
    }