git.stella-ops.org/docs/examples/policies/baseline.md

Baseline Policy Example (baseline.stella)

This sample policy provides a balanced default for production workloads: block critical findings, require strong VEX justifications to suppress advisories, and warn on deprecated runtimes. Use it as a starting point for tenants that want guardrails without excessive noise.

policy "Baseline Production Policy" syntax "stella-dsl@1" {
  metadata {
    description = "Block critical, escalate high, enforce VEX justifications."
    tags = ["baseline","production"]
  }

  profile severity {
    map vendor_weight {
      source "GHSA" => +0.5
      source "OSV" => +0.0
      source "VendorX" => -0.2
    }
    env exposure_adjustments {
      if env.exposure == "internet" then +0.5
      if env.runtime == "legacy" then +0.3
    }
  }

  rule block_critical priority 5 {
    when severity.normalized >= "Critical"
    then status := "blocked"
    because "Critical severity must be remediated before deploy."
  }

  rule escalate_high_internet {
    when severity.normalized == "High"
         and env.exposure == "internet"
    then escalate to severity_band("Critical")
    because "High severity on internet-exposed asset escalates to critical."
  }

  rule require_vex_justification {
    when vex.any(status in ["not_affected","fixed"])
         and vex.justification in ["component_not_present","vulnerable_code_not_present"]
    then status := vex.status
         annotate winning_statement := vex.latest().statementId
    because "Respect strong vendor VEX claims."
  }

  rule alert_warn_eol_runtime priority 1 {
    when severity.normalized <= "Medium"
         and sbom.has_tag("runtime:eol")
    then warn message "Runtime marked as EOL; upgrade recommended."
    because "Deprecated runtime should be upgraded."
  }

  rule block_ruby_dev priority 4 {
    when sbom.any_component(ruby.group("development") and ruby.declared_only())
    then status := "blocked"
    because "Development-only Ruby gems without install evidence cannot ship."
  }

  rule warn_ruby_git_sources {
    when sbom.any_component(ruby.source("git"))
    then warn message "Git-sourced Ruby gem present; review required."
    because "Git-sourced Ruby dependencies require explicit review."
  }
}

Commentary

• Severity profile tightens vendor weights and applies exposure modifiers so internet-facing/high severity pairs escalate automatically.
• VEX rule only honours strong justifications, preventing weaker claims from hiding issues.
• Warnings first – The alert_warn_eol_runtime rule name ensures it sorts before the require-VEX rule, keeping alerts visible without flipping to RequiresVex.
• Ruby supply-chain guardrails enforce Bundler groups and provenance: development-only gems without install evidence are blocked and git-sourced gems trigger review warnings.
• Works well as shared tenant-global baseline; use tenant overrides for stricter tolerant environments.

Try it out

stella policy new --policy-id P-baseline --template blank --open
stella policy lint examples/policies/baseline.stella
stella policy simulate P-baseline --candidate 1 --sbom sbom:sample-prod

Compliance checklist

• Policy compiled via stella policy lint without diagnostics.
• Simulation diff reviewed against golden SBOM set.
• Approval note documents rationale before promoting to production.
• EOL runtime tags kept up to date in SBOM metadata.
• VEX vendor allow-list reviewed quarterly.

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Last updated: 2025-11-10.