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AI-agent security guide

What Is a Credential-Injection Proxy?

Learn how credential-injection proxies let AI agents call approved APIs without receiving long-lived keys, and where the security boundary belongs.

Short answer

A credential-injection proxy stores long-lived secrets outside an AI agent, evaluates where each secret may be used, and adds the credential only as an approved request crosses the network boundary.

Separate credential custody from permission to call an API

An agent often needs permission to make a request, but it does not need to possess the long-lived credential that authenticates that request. A credential-injection proxy creates a separate boundary: the agent connects using an assigned proxy credential or sends a configured placeholder, while the upstream secret remains in controlled storage.

How a request crosses the boundary

The response returns to the client through the same proxy path. Logs should capture the decision and relevant metadata without recording the secret value.

  1. The client sends an HTTP request through the configured proxy.
  2. The proxy identifies the destination and applicable credential binding.
  3. Request policy is evaluated before forwarding.
  4. If the request is permitted, the credential is injected into the configured header and the proxy forwards the request.

Tradeoffs and limits

Placeholder-based injection can protect credentials without requiring TLS interception, but it only recognizes the locations and formats configured for replacement. A firewall mode that inspects TLS can evaluate more request details and may require a client trust configuration. Neither mode prevents an agent from misusing an API action it is allowed to make, and neither makes sensitive response data harmless.

Practical implementation checklist

  • Keep long-lived keys out of prompts, source files, notebooks, and process logs.
  • Bind each secret to the exact service hosts that require it.
  • Use the narrowest upstream credential scopes available.
  • Test denied hosts, missing secrets, expiration, and revocation.
  • Review request metadata without copying secret values into logs or tickets.

Applying the pattern with Hyperproxy

Hyperproxy provides Auto-Auth placeholders for configured request headers and Firewall mode for TLS inspection and CEL allow, deny, or hold decisions. Start with the quick start, review the security architecture, and test the exact hosts and actions your agents will use. Network-boundary credential separation reduces direct secret-read exposure; it does not guarantee that every permitted request is safe.

Sources

Safe example

export CIFP_PROXY_URL='https://user:pass@<proxy-host>:443'
curl -x "$CIFP_PROXY_URL" \
  -H 'Authorization: Bearer {$SERVICE_TOKEN}' \
  https://api.example.com/v1/resource