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Introduction:
As AI agents gain access to internal systems, security teams face a false choice: grant agents full engineer privileges (fast but dangerous) or force engineers to rebuild years of RBAC inside a governance proxy (secure but impractical). The dual trust model resolves this by having the agent inherit the engineer’s existing scope – never more – enforced by Open Policy Agent (OPA) at the execution boundary, while the agent holds credentials only to the governance layer, not to backend services like Salesforce or GitHub.
Learning Objectives:
- Implement OPA/Rego policies to enforce least privilege for AI agents without modifying existing RBAC.
- Configure OAuth 2.0 delegation so agents inherit user scopes dynamically.
- Deploy a credential‑starved agent architecture using Assury Enforce (or open‑source alternatives) to prevent lateral movement.
You Should Know:
- How the Dual Trust Model Works – Step‑by‑Step Enforcement with OPA
The model creates two trust boundaries: engineer ↔ governance proxy, and proxy ↔ downstream services. The engineer authenticates via OAuth; the proxy requests a token with the engineer’s existing scope (or a subset). The agent only talks to the proxy, never directly to Salesforce, GitHub, or payment processors.
Step‑by‑step guide to simulate the flow using OPA and a mock agent:
- Engineer OAuth login – Obtain an access token with scopes (e.g.,
read:repos,write:issues).Simulate token request (using curl) curl -X POST https://your-oauth-provider/token \ -d "grant_type=client_credentials&scope=read:repos write:issues" \ -H "Authorization: Basic $(echo -n client:secret | base64)"
-
Agent calls governance proxy – Agent sends a request with the engineer’s token.
curl -X POST https://enforce.proxy/execute \ -H "Authorization: Bearer $ENGINEER_TOKEN" \ -d '{"action":"list_issues","repo":"acme/app"}' -
OPA policy evaluation – The proxy validates the token, extracts scopes, and checks Rego rules.
package agent.entitlements default allow = false allow { input.action == "list_issues" input.repo == "acme/app" input.scopes[bash] == "read:repos" } -
Proxy calls downstream API – Only if policy allows; the proxy uses its own service account (no engineer credentials forwarded).
curl -H "Authorization: Bearer $PROXY_TOKEN" https://api.github.com/repos/acme/app/issues
Linux/Windows Commands for Testing OPA Locally:
- Linux: `opa eval –data policy.rego –input input.json “data.agent.entitlements.allow”`
– Windows (PowerShell): `opa.exe eval –data policy.rego –input input.json “data.agent.entitlements.allow”`
2. Credential‑Starved Agent Design – Eliminating Direct Secrets
The agent holds only one credential: a short‑lived JWT to authenticate with the governance proxy. No database passwords, no API keys for Salesforce, no cloud IAM roles.
Step‑by‑step configuration using environment variables and a secrets manager (Hashicorp Vault):
- Generate agent identity – Create a service account with minimal privileges (only `connect` to the proxy).
Linux openssl rand -base64 32 | docker secret create agent_token -
-
Inject only proxy URL and token into the agent container.
docker-compose.yml environment:</p></li> </ol> <p>- PROXY_URL=https://enforce.proxy:8443 - AGENT_TOKEN=${AGENT_TOKEN}- Proxy stores downstream secrets – Use Vault to dynamically issue short‑lived credentials for each backend.
vault write database/creds/readonly ttl=1h
-
Verify agent cannot bypass proxy – Attempt direct connection to backend (should fail).
Agent container curl https://api.salesforce.com -H "Authorization: Bearer fake" No route or 403
Windows PowerShell alternative:
$env:PROXY_URL="https://enforce.proxy:8443" $env:AGENT_TOKEN = (Get-Random -Minimum 100000 -Maximum 999999).ToString()
- Inheriting RBAC Without Rebuilding – OAuth Scope Mapping & OPA Integration
Engineers keep their existing roles (e.g., “dev-lead” with 50+ permissions). The governance proxy translates those roles into OPA‑evaluated attributes.
Step‑by‑step to map Azure AD roles to Rego policies:
- Engineer logs in via Azure AD – The proxy receives an ID token containing `roles` claim.
{ "roles": ["developer", "repo-admin"], "email": "[email protected]" } -
Write Rego policy that references the engineer’s role without changing the original RBAC.
package proxy.decision allow if { input.engineer.roles[bash] == "repo-admin" input.request.method == "DELETE" input.request.path == ["repos", "acme", "app"] } -
Proxy enforces policy – If denied, agent receives `403 Forbidden` with explanation.
-
Audit log – OPA can log every decision with the engineer’s identity.
opa eval --format=pretty --explain=notes --data policy.rego --input request.json
Tutorial – Simulating Role Inheritance with OpenFGA and OPA:
Use OpenFGA to model relationships (user `alice` → `can_delete` on repoapp). Then OPA queries OpenFGA at runtime.fga query check --user user:alice --relation can_delete --object repo:app
- Cloud Hardening for the Governance Proxy – AWS IAM & Azure Managed Identities
Deploy the proxy in a dedicated VPC with strict network controls and use workload identity instead of long‑lived keys.
Step‑by‑step AWS configuration:
- Launch an EC2 instance (or EKS pod) for the proxy with an IAM role that has no permissions to downstream services – only to fetch OPA policies from S3.
{ "Effect": "Allow", "Action": "s3:GetObject", "Resource": "arn:aws:s3:::opa-policies/" } -
Attach an IAM role for downstream access to a separate service account that the proxy assumes dynamically using `sts:AssumeRole` based on OPA decision.
aws sts assume-role --role-arn "arn:aws:iam::123456789012:role/github-proxy" --role-session-name "agent-session"
-
Enable VPC endpoints for S3 and STS to avoid internet exposure.
aws ec2 create-vpc-endpoint --vpc-id vpc-xyz --service-name com.amazonaws.us-east-1.s3
Windows/Azure hardening:
- Use Azure Managed Identities for the proxy VM.
- Restrict outbound traffic with NSG rules to only approved APIs (e.g., `api.github.com` on port 443).
- API Security & Exploitation Mitigation – Preventing Privilege Escalation via Agents
Attackers who compromise the agent cannot steal backend credentials because the agent has none. However, they can try to manipulate the engineer’s OAuth token or OPA policies.
Step‑by‑step mitigation:
- Validate token audience and issuer in the proxy.
Using jq to decode JWT echo $TOKEN | cut -d. -f2 | base64 -d | jq '.aud, .iss'
-
Enforce short token TTL (e.g., 15 minutes) and refresh via OAuth refresh token held only by the proxy, not the agent.
-
Detect anomalous agent requests – Monitor for sudden scope changes or forbidden actions.
Linux – watch OPA logs for denied requests tail -f /var/log/opa/decision.log | grep '"result":false'
-
Use mTLS between agent and proxy to prevent token replay.
openssl req -new -x509 -days 365 -key agent.key -out agent.crt
Vulnerability exploitation example (simulated):
If an attacker obtains the engineer’s token (via XSS or phishing), they can impersonate the agent. Mitigation: Bind token to agent’s TLS fingerprint or use Proof of Possession (PoP) tokens.
- Training Course Recommendation – Implementing Zero‑Trust for AI Agents
Based on this architecture, security teams should pursue hands‑on training in OPA/Rego, OAuth delegation, and workload identity.
Recommended modules:
- OPA Fundamentals – Write, test, and debug Rego policies (Linux Academy / A Cloud Guru)
- OAuth 2.0 for Microservices – JWT, scopes, and token exchange (Udemy – “OAuth 2.0 in Depth”)
- Cloud Native Security – AWS IAM roles for service accounts (IRSA) and Azure Managed Identities
Hands‑on lab: Build a dual‑trust proxy using Node.js/Express, OPA as a sidecar, and mock GitHub API.
git clone https://github.com/open-policy-agent/opa-envoy-plugin docker-compose up
What Undercode Say:
- Key Takeaway 1: The dual trust model decouples agent permissions from engineer permissions – agents inherit only a subset of the engineer’s existing RBAC, never more, and never store backend credentials.
- Key Takeaway 2: OPA/Rego provides a policy‑as‑code layer that enforces least privilege at runtime without forcing engineers to rebuild their access controls from scratch – a critical adoption enabler.
Analysis: Traditional agent governance fails because it either over‑privileges agents or demands a complete RBAC redesign. The dual trust approach leverages OAuth delegation and policy‑based enforcement to maintain the engineer’s five years of access control investment while keeping the agent credential‑starved. For CISOs, this shifts the conversation from “rebuild everything” to “enforce boundaries with OPA.” The main implementation challenge is correctly mapping existing roles to Rego policies without gaps – solved by incremental rollout starting with read‑only actions. As AI agents become autonomous, this model will likely become the default pattern for enterprise agent security.
Prediction: Within 18 months, major cloud providers will offer managed “agent governance proxies” that natively support dual‑trust RBAC inheritance. We will see the emergence of OPA‑as‑a‑service for AI workloads, and compliance frameworks (e.g., SOC2, ISO 27001) will add specific controls requiring agents to hold zero direct credentials to production data stores. Startups that fail to adopt this pattern will face audit failures and breaches as attackers pivot from vulnerable agents to backend systems.
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- Proxy stores downstream secrets – Use Vault to dynamically issue short‑lived credentials for each backend.
