Top Open-Source Authorization Tools for Enterprises in 2026

Authorization has become a core part of enterprise security architecture. As systems grow more distributed and data becomes more sensitive, "who can do what, on which resource, under which conditions" is no longer a simple RBAC table, it is a constantly changing graph.

Security architects, platform teams, and staff engineers increasingly turn to open-source tools and open standards to avoid vendor lock-in while still getting scalable, auditable authorization. These tools span everything from simple role checks to advanced, context-aware, relationship-based permissions that enforce least privilege across apps, APIs, data layers, and now AI agents.

This guide walks through the authorization tools most commonly used by enterprises in 2026, with an emphasis on open-source engines and ecosystems. For each, you will see where it shines, where it falls short, and how it fits into a modern IdP plus policy-engine stack, including agentic AI, RAG, and prompt filtering. We will also highlight where Permit.io, OPAL, and the Four-Perimeter AI Access Control Framework stand out when you need fine-grained, enterprise-grade control.

By the end, you will know how to:

• Classify tools as AuthN, AuthZ, IdP, or policy admin layer
• Understand which ones fit where in your stack
• Decide how to secure both traditional apps and AI workloads

AuthN vs AuthZ (and Why It Matters for AI)

Before picking tools, make sure you are solving the right half of the problem.

• Authentication (AuthN)
  - "Who or what is this?"
  
  Examples: SSO login, WebAuthn passkey, service account credentials.
• Authorization (AuthZ)
  - "What is this identity allowed to do?"
  
  Examples: Can this user update this invoice? Can this AI agent call this tool or access these documents?

In AI and RAG systems, this split is even more important:

• AuthN identifies the human or system behind an AI agent.
• AuthZ governs:
  • Which tools and APIs the agent may call
  • Which documents RAG may retrieve
  • Which prompts and responses are allowed (prompt filtering and response enforcement)

Most tools in this article are either:

• IdPs / IAMs
  - AuthN-first with some built-in AuthZ (Keycloak, ZITADEL, Authentik, etc.)
• Policy engines/ libraries/ languages
  - AuthZ-first (Permit.io, OPA, Cedar, Casbin, CASL.js), plugged into your apps and AI orchestrators
• Policy administration layers
  - like OPAL, which keep your policy agents up to date in real time

The winning pattern for zero-trust and agentic AI is:

Dedicated IdP (AuthN) + Dedicated policy engine/platform (AuthZ) + Real-time policy admin layer, wired together through tokens, claims, and policy checks.

Quick Comparison: Who Does What?

Here is a high-level view of the main projects covered:

Now let us dig into the policy/engine layer, then the IdPs.

Policy-First Authorization Engines and Admin Layers (AuthZ)

Permit.io - AuthZ Platform with Hybrid PDPs, Agent Security and AI Access Control

Permit.io is an authorization platform built for fine-grained, policy-based access control across applications, APIs, data layers, and AI agents. It is powered by open-source components like OPA and OPAL under the hood and can work with Rego and Cedar-style policies.

The control plane runs as SaaS, while policy decision points (PDPs) run next to your services in your own environment.

AuthZ profile: Deep RBAC/ABAC/ReBAC, multi-tenant, AI- and MCP-aware.

Key features:

• Policy models: RBAC, ABAC, and ReBAC for complex org and data graphs
• DX and UX: No-code policy editor plus policy-as-code (Rego, Cedar)
• Hybrid architecture: Stateless PDPs deployed in your infra for low latency, cloud control plane for management
• Integrations: SDKs for major languages/frameworks, plugs into existing IdPs (Auth0, Keycloak, ZITADEL, etc.)
• Observability: Centralized audit logs, decision traces, and OpenTelemetry hooks
• SaaS and B2B: First-class multi-tenancy, data filtering, and per-tenant policies

Pros

• Unified, fine-grained AuthZ across microservices, APIs, UIs, and AI agents
• Serves both developers (policy-as-code, SDKs) and non-dev stakeholders (policy UI)
• Hybrid PDP model keeps PII and decisions close to your services, improving latency and compliance

Cons

• Authorization-only: you still need an IdP/SSO for AuthN
• Like any serious AuthZ system, you must invest in modeling roles, resources, and relationships
• Some advanced governance and enterprise features are in paid tiers

Agentic AI, MCP, RAG, and Prompt Filtering

Permit.io provides a dedicated AI security model via the Four-Perimeter AI Access Control Framework:

1. Prompt Filtering
   - Check policies before prompts reach the LLM.
2. RAG Data Protection
   - Enforce document- and row-level access for vector stores and knowledge bases.
3. Securing External Access
   - Control which tools, MCP servers, and APIs agents can call.
4. Response Enforcement
   - Apply policy to the model output and block or redact disallowed content.

Permit.io also powers Agent.Security, an enterprise-grade security platform for AI agents and tools. Agent.Security focuses on managing agent identities, consent, delegation, and fine-grained permissions at scale. It integrates with the Model Context Protocol (MCP), an open standard for letting models talk to external tools and data sources.

MCP dramatically increases what agents can do, but also the blast radius if something goes wrong. With Permit.io and Agent.Security:

• MCP tools are treated as governed resources.
• MCP agents are treated as identities with scoped permissions.
• High-risk operations can be gated behind human approvals (for example via access request flows).
• The Four-Perimeter framework is applied to MCP: filtering prompts, governing which MCP servers/tools can be used, authorizing RAG over MCP-accessible data, and enforcing policy on responses.

Best for: Enterprises that want a central, fine-grained AuthZ layer for apps and AI pipelines, with strong auditability, MCP-aware security, and a hybrid enforcement model.

Open Policy Agent (OPA) - General-Purpose Policy Engine

Open Policy Agent is a CNCF-graduated, general-purpose policy engine that uses the Rego language to define and enforce policies across microservices, Kubernetes, APIs, CI/CD, and more.

AuthZ profile: Very flexible, an excellent building block for infra and app-level authorization and compliance.

Key features:

• Declarative policy language (Rego)
• Multiple deployment modes: sidecar, daemon, library, centralized service
• Common use cases: Kubernetes admission control, API gateways, microservices AuthZ, CI/CD policies
• Fits naturally into policy-as-code workflows (GitOps, CI checks)

Pros

• Single engine for many policy use cases (AuthZ, compliance, configuration checks)
• Strong community and ecosystem, widely adopted in cloud-native environments
• Stack-agnostic: use via HTTP, WASM, or SDKs

Cons

• No built-in UI or higher-level domain abstractions
• Rego and policy modeling can have a learning curve
• You must build and operate your own control plane and tooling around it

Agentic AI, RAG, and Prompt Filtering

OPA has no AI-specific features baked in, but it works very well as policy plumbing for AI systems:

• Tool access: run OPA alongside your AI orchestrator and check a Rego policy before each tool/API call.
• RAG authorization: secure vector and search queries by checking OPA before querying the index.
• LLM gateway guardrails: put OPA in front of your LLM API (via gateway or service mesh) to validate operation type, user role, and risk band.

You can then layer OPAL and/or a platform like Permit.io on top for real-time distribution and governance.

Best for: Teams comfortable with policy-as-code who want maximum flexibility and are fine owning the platform around OPA.

Cedar - Fine-Grained Policy Language and Engine

Cedar is an open-source policy language and evaluation engine designed specifically for fine-grained authorization (RBAC and ABAC). It was originally developed at AWS and is optimized for decoupling permissions from application logic, with human-readable and analyzable policies.

Cedar is increasingly being applied beyond AWS, including Kubernetes authorization and admission control scenarios.

AuthZ profile: Fine-grained language and engine with strong static analysis capabilities.

Key features:

• Purpose-built for fine-grained auth (RBAC and ABAC)
• Human-readable, declarative policies
• Schema support and policy validation to catch issues early
• High-performance evaluation suitable for real-time checks
• Evolving tooling for policy analysis and verification

Pros

• Designed from the ground up for authorization use cases
• Strong emphasis on analyzability, making it easier to reason about policy impact
• Good fit for high-assurance, regulated environments

Cons

• Primarily focused on language and engine; you still need distribution and control-plane tooling
• Ecosystem and integrations are newer compared to OPA
• Requires investing in Cedar-specific skills and tooling

Agentic AI, RAG, and Prompt Filtering

Cedar strengths, fine-grained modeling and static analysis, make it compelling when you need high-assurance AI access control:

• Model AI tools, RAG datasets, and operations as Cedar resources/actions.
• Use analysis tooling to understand how policy changes affect what agents can do before deployment.
• Combine Cedar with an admin layer like OPAL (and platforms like Permit.io, which can work with Cedar-like semantics) to keep policies consistent across microservices and AI agents.

Best for: Teams that want a purpose-built authorization language with strong verification capabilities, especially in cloud-native and regulated environments.

Casbin - Multi-Language Authorization Library

Casbin is an open-source authorization library that supports several access control models, ACL, RBAC, ABAC, ReBAC, and more, implemented in multiple languages (Go, Java, Node.js, Python, .NET, Rust, and others).

AuthZ profile: Powerful, library-level engine for embedding policy checks directly into services.

Key features:

• Support for ACL, RBAC, ABAC, ReBAC, and custom models
• Consistent APIs across multiple languages
• Policies stored in config files or various databases
• Online model editor and ecosystem of adapters

Pros

• Portable across many languages and stacks
• Flexible modeling, from simple role checks to attribute- and relationship-based control
• Good for teams that want control in code, close to business logic

Cons

• Library-only: you must design the policy lifecycle, control plane, and tooling
• No native UI or collaboration layer for non-developers
• Distributed configuration and real-time policy updates are DIY

Agentic AI, RAG, and Prompt Filtering

Casbin fits well as a policy engine inside AI services:

• Agent tool authorization: before an agent calls an API or tool, your orchestrator checks Casbin for permission.
• RAG access control: use ABAC/ReBAC models to restrict which datasets, indexes, or tenants the RAG layer can query.
• Prompt/action filtering: represent high-risk operations as Casbin actions and block prompts that would trigger unauthorized behavior.

Best for: Teams that like embeddable libraries, want strongly typed models in code, and are comfortable running their own policy platform.

CASL.js - JavaScript/TypeScript Authorization Library

CASL is an isomorphic JavaScript authorization library that helps you describe what a user "can" and "cannot" do on particular resources, on both frontend and backend.

AuthZ profile: App-level authorization for JS/TS stacks, ideal for aligning UI with server-side permissions.

Key features:

• Declarative abilities (for example
  can('read', 'Post', { authorId: user.id })
  )
• Same rules can be used in browser and Node.js backends
• Integration helpers for React, Angular, Vue, and others
• Flexible from simple RBAC-style rules to attribute-based conditions

Pros

• Great developer experience for JavaScript/TypeScript teams
• Isomorphic rules keep UI and backend logic aligned
• Very natural way to shape UI behavior (show/hide/disable actions)

Cons

• Focused on app-level AuthZ, not a full IAM or enterprise control plane
• Frontend use alone is not secure; you must enforce rules on the server as well
• No built-in multi-service governance or management UI

Agentic AI, RAG, and Prompt Filtering

CASL is a good lightweight guardrail around AI UX and APIs:

• Feature gating: decide which AI features the user sees (for example advanced "Ask AI with internal data" vs basic "public Q&A").
• Backend checks: in a Node.js AI gateway, call CASL before invoking an LLM or RAG pipeline to ensure the requested operation is allowed.
• Simple prompt constraints: map abilities to safe prompt types or toolsets, and deny or downgrade high-risk operations based on CASL rules.

Best for: JS-heavy teams that want a clean permission model across frontend and backend and a straightforward way to gate AI features.

OPAL - Real-Time Policy and Data Administration Layer

OPAL (Open Policy Administration Layer) is an open-source administration layer for policy engines like OPA and Cedar. It detects changes to policy and policy data in real time and pushes live updates to your policy agents so they are always in sync with the latest state.

AuthZ profile: Not an engine itself, a distribution and admin layer that keeps OPA/Cedar/other agents up to date.

Key features:

• Watches sources like Git, databases, APIs, object storage, and SaaS services for changes in policies and auth data
• Streams only relevant updates to policy agents (for example sidecars in microservices)
• Cloud-native and microservices-friendly architecture
• Works with multiple engines and policy languages (Rego, Cedar, etc.)

Pros

• Solves the "how do I keep all my policy agents in sync?" problem
• Decouples policy lifecycle and data distribution from the engines themselves
• Highly relevant for dynamic environments (microservices, multi-region, AI workloads)

Cons

• Another moving part in your architecture (though one you almost certainly need at scale)
• You still need to pick and operate your policy engines (OPA, Cedar, etc.)

Agentic AI, RAG, and Prompt Filtering

For AI-heavy environments, OPAL becomes critical infrastructure:

• Keeps policy agents near your AI services and MCP servers up to date with the latest roles, risk flags, and data entitlements.
• Ensures that when an AI agent permissions change (for example temporary elevation via an access request), the change propagates quickly and safely.
• Connects to dynamic data sources (RBAC assignments, org structure, risk signals) so AI authorization decisions reflect real-time context.

Best for: Teams that adopt OPA/Cedar (or Permit.io OPA/Cedar-based stack) and need a robust, real-time way to distribute policy and data across fleets of services and AI agents.

IdPs and IAM Platforms (AuthN plus Built-In AuthZ)

These tools primarily handle authentication (SSO, MFA, federation) and user lifecycle, with some authorization capabilities.

Keycloak - Open-Source IdP with RBAC/UMA

Keycloak is a widely adopted IdP providing SSO, MFA, and federation with support for OIDC and SAML. It offers RBAC and User-Managed Access (UMA) for resource permissions.

Role: IdP (AuthN) plus built-in AuthZ.

AuthZ profile: Strong RBAC plus some resource-based AuthZ. Often paired with a dedicated AuthZ engine for complex, cross-service policies.

Key features:

• SSO, MFA, and social logins
• Support for OIDC, SAML, and other standards
• User federation with LDAP/AD and other user stores
• Admin and user consoles, REST APIs
• Clustering and HA for large deployments

Pros

• Mature and widely used in enterprises
• Strong ecosystem and community
• Works both self-hosted and via managed offerings

Cons

• Configuration and upgrades can be complex
• Java stack may not fit every organization preferences
• Authorization model can be coarse for complex domain graphs

Best for: Enterprises that want a mature, open-source IdP and can integrate external engines (like Permit.io or OPA/Cedar-based services) for deeper AuthZ and AI use cases.

ZITADEL - Identity Infrastructure with Multi-Tenancy

ZITADEL is an open-source identity platform built in Go, designed for multi-tenancy and automation. It provides authentication, RBAC, and event-sourced audit trails.

Role: IdP / IAM (AuthN plus AuthZ).

AuthZ profile: Tenant- and project-level RBAC with strong auditability, not focused on very fine-grained, cross-service policies.

Key features:

• Passwordless logins, MFA, and SSO
• Multi-tenant projects and organizations
• Event-sourced audit logs for identities and permissions
• API-first design with gRPC, REST, and Terraform support

Best for: Cloud-native teams and SaaS providers who want multi-tenant identity plus API-driven management, and will use a specialized AuthZ engine for very granular policies.

Gluu - Comprehensive IAM Suite

Gluu is a full IAM platform providing SSO, OAuth2/OIDC, SAML, MFA, and more. It can serve as an open-source alternative to commercial IAM suites.

Role: IAM (AuthN plus AuthZ).

AuthZ profile: Token-based access control and adaptive policies embedded in a large IAM solution.

Key features:

• Enterprise-grade SSO and federation
• Adaptive MFA and policy-based risk controls
• Admin console and extension points
• Support for customer and workforce identity use cases

Best for: Larger organizations that want a self-hosted IAM to handle a wide variety of identity and access scenarios and are comfortable operating a heavier stack.

Authentik - Flexible Self-Hosted IdP

Authentik is a self-hosted IdP that supports OIDC, SAML, LDAP, and more, with highly customizable flows.

Role: IdP (AuthN) plus some AuthZ.

AuthZ profile: RBAC and flow-based policies; complex scenarios often implemented via scripts or custom code.

Key features:

• OIDC and SAML support
• LDAP and RADIUS integration
• Flexible, editor-based flows for onboarding and access workflows
• Admin UI for users, groups, and policies

Best for: Teams that want to own their IdP, integrate with legacy systems, and design custom onboarding and access flows.

Authelia - Gateway-Style SSO and MFA

Authelia is an authentication and authorization server that sits behind reverse proxies (NGINX, Traefik, etc.), providing SSO, MFA, and route-based AuthZ.

Role: IAM/gateway (AuthN plus coarse AuthZ).

AuthZ profile: Route-, domain-, and group-based rules. Great as a hardened front door, not designed for deep, domain-specific AuthZ.

Key features:

• 2FA/MFA with TOTP, hardware keys, WebAuthn
• Integrates as a forward-auth service with reverse proxies
• Uses backends like LDAP or SQL for identity
• Docker- and Kubernetes-friendly deployment

Best for: Teams protecting a set of web apps behind a proxy and wanting SSO plus MFA without replacing their entire IAM stack.

Dex - OIDC IdP and Identity Broker

Dex is an OIDC identity provider that federates identities from LDAP, SAML, GitHub, and others, exposing a unified OIDC interface.

Role: IdP / identity broker (AuthN).

AuthZ profile: Primarily scopes and claims, real resource-level authorization is usually implemented downstream.

Key features:

• Connectors for popular IdPs and directories
• Kubernetes-native deployment patterns
• Simple configuration and operation model

Best for: Kubernetes and microservices environments that need consistent identity federation with minimal overhead.

Ory Hydra - OAuth2/OIDC Token Service

Ory Hydra is an OAuth2/OIDC server focused on issuing tokens and handling consent; it delegates user management and UX to other systems.

Role: Token/consent service (AuthN plumbing, limited AuthZ).

AuthZ profile: Scope-level decisions and consent flows, expects you to handle resource-level authorization elsewhere.

Key features:

• Fully RFC-compliant OAuth2/OIDC implementation
• Consent flows customizable via your own UI services
• Cloud-native, horizontally scalable architecture

Best for: Highly modular, microservice-heavy architectures that want a minimal, standards-compliant token service.

Hanko - Passwordless / WebAuthn Authentication

Hanko focuses on modern login UX with passkeys/WebAuthn, MFA, and social logins.

Role: AuthN.

AuthZ profile: Minimal, serves as the identity provider you feed into a separate AuthZ layer.

Key features:

• Passwordless login via WebAuthn
• Multi-factor authentication
• Drop-in UI components and SDKs

Best for: Teams that want great passwordless UX and will handle authorization in other layers.

SuperTokens - Login and Session Management

SuperTokens provides login, sign-up, session management, and security best practices with SDKs and prebuilt UIs.

Role: AuthN plus session management.

AuthZ profile: Useful for "is the user logged in and what is their role?", not for complex RBAC/ABAC/ReBAC.

Key features:

• Prebuilt auth UIs and flows
• Refresh token and session management
• Self-hosted or managed deployment

Best for: Startups and product teams shipping quickly who may add a dedicated AuthZ engine later.

Platform-Integrated Auth

Supabase Auth - Auth plus Postgres Row-Level Security

Supabase Auth integrates authentication with PostgreSQL row-level security (RLS) by issuing JWTs that Postgres uses to enforce access control.

Role: Platform AuthN plus DB-level AuthZ.

AuthZ profile: Very strong at the database layer for Postgres-backed apps, not a general-purpose, cross-service authorization plane.

Key features:

• Password, passwordless, and social logins
• JWT-based AuthN tied to Postgres RLS policies
• Tight integration with Supabase platform services

Best for: Greenfield projects built on Supabase/Postgres where most logic lives in the database, and cross-service AuthZ requirements are relatively simple.

How These Tools Fit Agentic AI, RAG, MCP, and Prompt Filtering

Putting it all together for AI and RAG systems:

1. IdPs / AuthN

Tools like Keycloak, ZITADEL, Authentik, Authelia, Dex, Hanko, SuperTokens, Supabase Auth:

• Authenticate humans and services
• Issue tokens with roles, org IDs, and attributes
• Provide the identity context for AI agents (for example "agent acting on behalf of user X in tenant Y")

2. Policy Engines, Languages, and Libraries (AuthZ)

Tools like Permit.io, OPA, Cedar, Casbin, CASL.js:

• Make fine-grained decisions about:
  • Which tools/APIs an agent can call
  • Which tenants and documents RAG is allowed to query
  • Which prompt types and responses are permitted

3. Policy Administration and Distribution

OPAL:

• Keeps all your policy agents (OPA, Cedar-based, Permit PDPs, etc.) in sync with current policies and data in real time
• Ensures AI agents and MCP servers enforce up-to-date permissions as business context changes

4. AI-Specific Access Control (Permit.io plus Agent.Security plus MCP)

Permit.io Four-Perimeter Framework and the Agent.Security platform give you a structured way to apply authorization across the AI stack:

1. Prompt Filtering
   - Check prompts against policy before sending them to the model.
2. RAG Data Protection
   - Only expose documents, rows, or fields the user/agent is allowed to see.
3. Securing External Access (including MCP tools)
   - Control agents access to external tools, APIs, and MCP servers.
4. Response Enforcement
   - Validate and, if needed, redact the model response before returning it.

Permit.io and Agent.Security integrate with MCP (Model Context Protocol) so you can:

• Treat MCP tools as policy-governed resources
• Give MCP agents scoped permissions tied back to human identities and org structure
• Keep humans in the loop for high-risk operations via access requests and approvals

Key Criteria for Evaluating Authorization Tools in 2026

Whether you are securing classic SaaS or multi-agent AI systems, focus on:

1. Security and Compliance
   • Least privilege, auditability, policy review
   • Fit for regulations (SOC 2, GDPR, HIPAA, etc.)
2. Reliability and Performance
   • Can it handle your authorization check volume and latency requirements, especially for chatty AI agents and MCP tool calls?
3. Scalability
   • Does it support many tenants, users, agents, MCP servers, services, and regions without becoming unmanageable?
4. Expressiveness and Extensibility
   • Does it support RBAC, ABAC, and ReBAC when you need them?
   • Can you incorporate AI-specific context (tool type, dataset, risk level, MCP server identity)?
5. Operational Overhead
   • Who runs it (you vs vendor)?
   • How painful are upgrades, incident response, and migrations?
6. Developer and Stakeholder Experience
   • Are there good SDKs and APIs?
   • Can security, platform, and product teams collaborate on policies without blocking each other?

Permit.io is designed to score well across all of these, especially for AI-heavy workloads. It builds on open-source engines (like OPA, Cedar, and OPAL), provides a hybrid PDP architecture, exposes both code- and UI-based policy workflows, and adds AI-native capabilities through the Four-Perimeter framework, Agent.Security, and MCP integrations.

What to Do Next

A practical path for most enterprises in 2026 looks like this:

1. Pick or confirm your IdP
   • Keycloak, ZITADEL, Authentik, Authelia, or a managed IdP, whatever fits your identity strategy.
2. Add a dedicated AuthZ layer
   • Use a policy platform like
     Permit.io
     (with OPA/Cedar/OPAL under the hood) or a combination of
     OPA, Cedar, Casbin, CASL.js
     if you want to build more yourself.
3. Adopt a policy admin layer
   • Use
     OPAL
     to keep policies and data synchronized in real time across your services and AI agents.
4. Apply an AI security model
   • Use the
     Four-Perimeter Framework
     plus
     Agent.Security
     and MCP integrations to extend authorization to prompts, RAG data, tools, and responses.
5. Start small, then expand
   • Secure one critical API or AI agent first (for example "billing assistant" or "admin AI"), validate the model, then roll it out to more services and agents.

To dive deeper into the authorization side:

• Configure your first RBAC policy in Permit.io
• Create a ReBAC policy
• Four-Perimeter Framework for AI Access Control

From there, you will have the building blocks to create a modern, identity- and policy-driven security architecture that works for both humans and AI agents across microservices, RAG, and MCP-powered tools.