Preventing applications from bypassing the AI governance proxy to reach LLM APIs
To prevent AI governance proxy bypass, make the proxy the only workload that both can reach LLM provider endpoints and holds valid provider credentials. Layer default-deny egress with allow-listing, centralized key custody, workload identity for authenticating to the proxy, build and platform guardrails, and detection that flags any direct call. Then test the controls regularly and track the gaps that remain.
Control layers in order
| Layer | Description |
|---|---|
| 1. Network egress | Default-deny outbound traffic, with LLM endpoints reachable only from the proxy. |
| 2. Credential custody | Provider keys held by the proxy and nowhere else. |
| 3. Workload identity | Applications authenticate to the proxy with short-lived, platform-issued identity. |
| 4. Build and platform guardrails | Secrets scanning, SDK and endpoint restrictions, admission policy. |
| 5. Detection and verification | Logs, reconciliation and recurring bypass tests. |
The main bypass paths
A bypass happens when an application can reach an LLM provider endpoint directly, or can obtain a valid provider credential outside the proxy. The goal is to make the proxy the only workload that can do both.
Start by finding where those paths exist today. Inventory:
- Which workloads, CI/CD systems and workstations can reach provider endpoints.
- Which provider keys exist outside the proxy.
Layer one: network egress allow-listing
Apply default-deny outbound traffic, with LLM endpoints reachable only from the proxy. Enforce default-deny egress with the proxy as the only allowed source, and run bypass tests to confirm that other sources are blocked.
Before enforcing, turn on egress logging in detect-only mode to find current direct usage.
Layer two: credential custody and workload identity
Provider keys should be held by the proxy and nowhere else. Applications authenticate to the proxy with short-lived, platform-issued identity rather than with provider keys.
Move applications to the proxy using workload identity, then rotate or revoke the keys they used.
Layer three: secrets scanning, SDK and endpoint restrictions
Build and platform guardrails include secrets scanning, SDK and endpoint restrictions, and admission policy. Run secrets scanning in detect-only mode first to find provider keys that exist outside the proxy.
Layer four: detection and verification
Detection relies on logs, reconciliation and recurring bypass tests. The aim is to flag any direct call to a provider and to confirm that the controls keep working.
Reconcile provider usage with proxy logs on a recurring basis, and test the controls regularly.
Sequencing and residual gaps
Roll the controls out in this order:
- Inventory which workloads, CI/CD systems and workstations can reach provider endpoints, and which keys exist outside the proxy.
- Turn on egress logging and secrets scanning in detect-only mode to find current direct usage.
- Move applications to the proxy using workload identity, then rotate or revoke the keys they used.
- Enforce default-deny egress with the proxy as the only allowed source, and run bypass tests.
- Reconcile provider usage with proxy logs on a recurring basis.
Make the proxy path the enforced path
Trussed AI provides runtime governance for enterprise AI agents, including runtime policy enforcement, agent identity and audit logging. If you are designing enforcement around an AI governance proxy, we can discuss how these controls fit your environment.
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