Sample public source code scan with compliance check for Supply Chain Security Tools - Scan

This topic includes an example public source code scan with a compliance check for Supply Chain Security Tools (SCST) - Scan.

Public source scan

This example performs a source scan on a public repository. The source revision has 192 known Common Vulnerabilities and Exposures (CVEs), spanning several severities. SourceScan uses the ScanPolicy to run a compliance check against the CVEs.

The example policy is set to only consider Critical severity CVEs as violations, which returns 7 CVEs.

Caution

This example ScanPolicy is deliberately constructed to showcase the features available and must not be considered an acceptable base policy.

For this example, this scan:

• Finds all 192 of the CVEs
• Ignores any CVEs that have severities that are not critical
• Indicates in the Status.Conditions that 7 CVEs have violated policy compliance

Run an example public source scan

To perform an example source scan on a public repository:

1. Create sample-public-source-scan-with-compliance-check.yaml with the following content to define ScanPolicy and SourceScan:

   ---
   apiVersion: scanning.apps.tanzu.vmware.com/v1beta1
   kind: ScanPolicy
   metadata:
     name: sample-scan-policy
     labels:
       'app.kubernetes.io/part-of': 'enable-in-gui'
   spec:
     regoFile: |
       package main
   
       # Accepted Values: "Critical", "High", "Medium", "Low", "Negligible", "UnknownSeverity"
       notAllowedSeverities := ["Critical"]
       ignoreCves := []
   
       contains(array, elem) = true {
         array[_] = elem
       } else = false { true }
   
       isSafe(match) {
         severities := { e | e := match.ratings.rating.severity } | { e | e := match.ratings.rating[_].severity }
         some i
         fails := contains(notAllowedSeverities, severities[i])
         not fails
       }
   
       isSafe(match) {
         ignore := contains(ignoreCves, match.id)
         ignore
       }
   
       deny[msg] {
         comps := { e | e := input.bom.components.component } | { e | e := input.bom.components.component[_] }
         some i
         comp := comps[i]
         vulns := { e | e := comp.vulnerabilities.vulnerability } | { e | e := comp.vulnerabilities.vulnerability[_] }
         some j
         vuln := vulns[j]
         ratings := { e | e := vuln.ratings.rating.severity } | { e | e := vuln.ratings.rating[_].severity }
         not isSafe(vuln)
         msg = sprintf("CVE %s %s %s", [comp.name, vuln.id, ratings])
       }
   
   ---
   apiVersion: scanning.apps.tanzu.vmware.com/v1beta1
   kind: SourceScan
   metadata:
     name: sample-public-source-scan-with-compliance-check
   spec:
     git:
       url: "https://github.com/houndci/hound.git"
       revision: "5805c650"
     scanTemplate: public-source-scan-template
     scanPolicy: sample-scan-policy
   

2. (Optional) Before deploying the resources to a user-specified namespace, set up a watch in another terminal to view the progression by running:

   watch kubectl get sourcescans,imagescans,pods,taskruns,scantemplates,scanpolicies -n DEV-NAMESPACE
   

   Where DEV-NAMESPACE is the developer namespace where the scanner is installed.

   For more information, see Observing and Troubleshooting.

3. Deploy the resources by running:

   kubectl apply -f sample-public-source-scan-with-compliance-check.yaml -n DEV-NAMESPACE
   

   Where DEV-NAMESPACE is the developer namespace where the scanner is installed.

4. When the scan completes, view the results by running:

   kubectl describe sourcescan sample-public-source-scan-with-compliance-check -n DEV-NAMESPACE
   

   The Status.Conditions includes a Reason: EvaluationFailed and Message: Policy violated because of 7 CVEs. For more information, see Viewing and Understanding Scan Status Conditions.

5. If the failing CVEs are acceptable, or the build must be deployed regardless of these CVEs, the app is patched to remove the vulnerabilities. Update the ignoreCVEs array in the ScanPolicy to include the CVEs to ignore by running:

   ...
   spec:
    regoFile: |
      package policies
   
      default isCompliant = false
   
      # Accepted Values: "UnknownSeverity", "Critical", "High", "Medium", "Low", "Negligible"
      violatingSeverities := ["Critical"]
      # Adding the failing CVEs to the ignore array
      ignoreCVEs := ["CVE-2018-14643", "GHSA-f2jv-r9rf-7988", "GHSA-w457-6q6x-cgp9", "CVE-2021-23369", "CVE-2021-23383", "CVE-2020-15256", "CVE-2021-29940"]
   ...
   

6. The changes applied to the new ScanPolicy trigger the scan to run again. Reapply the resources by running:

   kubectl apply -f sample-public-source-scan-with-compliance-check.yaml -n DEV-NAMESPACE
   

7. Re-describe the SourceScan CR by running:

   kubectl describe sourcescan sample-public-source-scan-with-compliance-check -n DEV-NAMESPACE
   

8. Ensure that Status.Conditions now includes Reason: EvaluationPassed and No CVEs were found that violated the policy. You can update the violatingSeverities array in the ScanPolicy. The example Grype scan returns the following severity spread of vulnerabilities:

   • Critical: 7
   • High: 88
   • Medium: 92
   • Low: 5
   • Negligible: 0
   • UnknownSeverity: 0

9. Clean up by running:

   kubectl delete -f sample-public-source-scan-with-compliance-check.yaml -n DEV-NAMESPACE