Microsoft AzureOverview
Client certificates allow for the app to request a certificate for incoming requests. Only clients that have a valid certificate will be able to reach the app.
Rationale
The TLS mutual authentication technique in enterprise environments ensures the authenticity of clients to the server. If incoming client certificates are enabled, then only an authenticated client who has valid certificates can access the app.
Impact
Utilizing and maintaining client certificates will require additional work to obtain and managed replacement and key rotation.
Remediation guidance
From Azure Console
- Go to
App Services - For each app, under
Settings, selectConfiguration - Go to
General settings - Under
Incoming client certificates, setClient certificate modetoRequire
Using Azure Command Line Interface
To set Incoming client certificates value for an existing app, run the following command:
az webapp update --resource-group <resourceGroup> --name <applicationName> --set clientCertEnabled=true
Default Value
By default, incoming client certificates will be disabled when a new app is created using the command-line tool or Azure Portal console.
References
Multiple Remediation Paths
Azure
SERVICE-WIDE (RECOMMENDED when many resources are affected): Assign Azure Policy initiatives at management group/subscription scope and trigger remediation tasks.
az policy assignment create --name <assignment-name> --scope /subscriptions/<subscription-id> --policy-set-definition <initiative-id>
az policy remediation create --name <remediation-name> --policy-assignment <assignment-id>
ASSET-LEVEL: Apply the resource-specific remediation steps above to the listed non-compliant resources.
PREVENTIVE: Embed Azure Policy checks into landing zones and IaC workflows to block or auto-remediate drift.
References for Service-Wide Patterns
- Azure Policy overview: https://learn.microsoft.com/en-us/azure/governance/policy/overview
- Azure Policy remediation: https://learn.microsoft.com/en-us/azure/governance/policy/how-to/remediate-resources
- Azure Policy initiative structure: https://learn.microsoft.com/en-us/azure/governance/policy/concepts/initiative-definition-structure
Operational Rollout Workflow
Use this sequence to reduce risk and avoid repeated drift.
1. Contain at Service-Wide Scope First (Recommended)
- Azure: assign policy initiatives at management group/subscription scope and run remediation tasks.
az policy assignment create --name <assignment-name> --scope /subscriptions/<subscription-id> --policy-set-definition <initiative-id>
az policy remediation create --name <remediation-name> --policy-assignment <assignment-id>
2. Remediate Existing Affected Assets
- Execute the control-specific Console/CLI steps documented above for each flagged resource.
- Prioritize internet-exposed and production assets first.
3. Validate and Prevent Recurrence
- Re-scan after each remediation batch.
- Track exceptions with owner and expiry date.
- Add preventive checks in IaC/CI pipelines.
Query logic
These are the stored checks tied to this control.
The web app has 'Client Certificates (Incoming client certificates)' set to 'On'
Connectors
Covered asset types
Expected check: eq []
{sites(where:{clientCertEnabled_NOT:true}){...AssetFragment}}
