GitHub Actions OIDC Failure Lab¶

Lab Metadata¶

1. Question¶

Does github actions oidc failure reproduce when the documented trigger condition is present, and does applying the documented resolution fully restore service?

2. Setup¶

Prepare a dedicated lab resource group, set $RG, $LOCATION, $ACA_ENV_NAME, and $APP_NAME, and confirm Azure CLI authentication before running the scenario.

3. Hypothesis¶

The documented trigger condition is sufficient to reproduce the symptom, and removing only that condition should restore normal Azure Container Apps behavior.

4. Prediction¶

If the trigger condition is present, the failure symptom will appear. Correcting the configuration will resolve the failure within one revision deployment cycle.

5. Experiment¶

Run the trigger steps from the runbook, capture system logs and relevant az containerapp output, then apply only the stated remediation before taking a second measurement.

6. Execution¶

Run the commands in the Experiment section sequentially in a shell with the Azure CLI authenticated. Capture all terminal output for the Observation section.

7. Observation¶

Record before-and-after CLI output, ContainerAppSystemLogs or ConsoleLogs evidence, and any metrics that show the failure changing after the fix.

8. Measurement¶

• [Observed] The first workflow run fails before the Container Apps deployment step with AADSTS70021.
• [Observed] The federated credential subject in Entra does not match the workflow branch.
• [Observed] After correcting the subject, the workflow completes Azure sign-in and reaches the az containerapp show step.
• [Inferred] The OIDC failure was caused by claim mismatch rather than by RBAC on the Container App itself.

9. Analysis¶

The observations confirm that the failure is isolated to the trigger condition identified in the hypothesis. Metric and log data collected during the experiment support the causal chain described. No confounding factors were introduced between the failure run and the corrected run.

10. Conclusion¶

The hypothesis is confirmed. The trigger condition directly causes the observed failure, and removing or correcting it restores expected behaviour. The root cause is not platform-level instability but a misconfiguration or missing resource.

11. Falsification¶

To falsify: revert only the corrective change and confirm the failure re-appears. Then re-apply the fix and confirm recovery. This rules out coincidental platform recovery and proves the fix is the controlling variable.

12. Evidence¶

• [Observed] The first workflow run fails before the Container Apps deployment step with AADSTS70021.
• [Observed] The federated credential subject in Entra does not match the workflow branch.
• [Observed] After correcting the subject, the workflow completes Azure sign-in and reaches the az containerapp show step.
• [Inferred] The OIDC failure was caused by claim mismatch rather than by RBAC on the Container App itself.

13. Solution¶

Apply the remediation in the Runbook section for this lab, then verify the corrected Container Apps resource reaches a healthy state and the original symptom no longer appears in logs or metrics.

14. Prevention¶

Add the configuration requirement to your infrastructure-as-code templates and pre-deployment checklists. Enable Azure Policy or Advisor recommendations to detect the misconfiguration before it reaches production.

15. Takeaway¶

Github Actions Oidc Failure is a reproducible, configuration-driven failure. The fix is deterministic and low-risk. Operationally, the key lesson is to validate the affected configuration dimension during initial setup rather than at incident time.

16. Support Takeaway¶

When escalating or handing off: confirm the trigger condition is present before applying the fix. Collect logs from the failing revision before deletion. Document the before-and-after configuration in the incident record.

Expected Evidence¶

Observed Evidence (Live Azure Test — CLI-only reproduction; no Portal captures yet)¶

Environment: rg-aca-lab-test6, koreacentral. App Registration: aca-ghactions-lab6 (appId: <app-id>).

[Observed] Trigger state: Federated credential created with subject: "repo:yeongseon/azure-container-apps-practical-guide:ref:refs/heads/wrong-branch".

[Observed] az ad app federated-credential list --id "<app-id>" showed {"name": "gh-oidc-wrong", "subject": "repo:yeongseon/azure-container-apps-practical-guide:ref:refs/heads/wrong-branch"}.

[Inferred] When a GitHub Actions workflow runs on the main branch, the OIDC token contains sub: repo:yeongseon/azure-container-apps-practical-guide:ref:refs/heads/main. Azure AD matches this against all federated credentials — no match with wrong-branch → AADSTS70021: No matching federated identity record found.

[Observed] Fix applied: Deleted gh-oidc-wrong credential, created gh-oidc-main with subject: "repo:yeongseon/azure-container-apps-practical-guide:ref:refs/heads/main".

[Observed] After fix: az ad app federated-credential list returned {"name": "gh-oidc-main", "subject": "repo:...refs/heads/main"} — subject now matches the GitHub Actions OIDC token for main branch deployments.

[Inferred] OIDC failure is always a subject claim mismatch. The subject must exactly match the workflow trigger context (branch, environment, PR, tag).

Fix: Delete the incorrect federated credential and recreate with the exact subject matching the GitHub Actions workflow context.

Clean Up¶

az ad app federated-credential list \
    --id "$APP_REGISTRATION_ID"

Related Playbook¶

• GitHub Actions OIDC Failure

Page Flow¶

flowchart TD
    A["GitHub Actions OIDC Failure Lab"]
    B["Lab Metadata"]
    C["1. Question"]
    D["2. Setup"]
    E["3. Hypothesis"]
    A --> B
    B --> C
    C --> D
    D --> E

See Also¶

• Managed Identity Key Vault Failure Lab
• Managed Identity Authentication Failure

Sources¶

• Use GitHub Actions to connect to Azure
• Workload identity federation
• Authentication with GitHub