Identity Broker Overview

The Identity Broker is a server-side authentication middleware for ASP.NET Core that manages the complete login lifecycle — local credentials, OIDC/SAML SSO, MFA, and session management — on your behalf. It keeps all tokens on the server and issues a single encrypted, HttpOnly cookie to the browser, implementing the Backend-for-Frontend (BFF) security pattern recommended by OWASP.

Why Identity Broker?

Modern security standards (OWASP 2026) discourage storing access tokens in the browser (LocalStorage/SessionStorage) due to XSS risks. The Identity Broker handles all token exchanges on the server and issues a secure, encrypted, partitioned cookie to the frontend.

Feature	Client-Side Auth (Standard)	Identity Broker (BFF)
Token Storage	LocalStorage (Vulnerable to XSS)	HttpOnly Cookie (Secure)
Encryption	None (JWT visible)	AES-256 Encrypted Cookie
CSRF	Rely on Samesite	Double-Submit Cookie Pattern
Privacy	3rd Party Cookies (Blocked by Safari)	First-Party Context

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Decision guide

• Identity Validator: Use this if your APIs already receive JWTs and only need token validation.
• Identity Broker: Use this if you need a complete login experience for a browser app and want secure cookie sessions.
• Both: Use Broker for the SPA and Validator for downstream APIs.

See: Identity Validator Overview

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Supported Providers

The broker supports seamless integration with major enterprise identity providers.

Azure AD / Entra ID

Multi-tenant SaaS support with Admin Consent flow.

OIDCSAMLEnterpriseMFA

Auth0

B2B SaaS isolation with Organizations.

OIDCB2BMFA

Google

Business login with Hosted Domain restrictions.

OIDCSAMLSocialMFA

Okta

Workforce identity with PKCE and Authorization Code flow.

OIDCSAMLPKCEMFA

Custom / Generic SAML

ADFS, Shibboleth, PingFederate, or any SAML 2.0 IdP without a dedicated provider page.

SAML 2.0EnterpriseMulti-IdP

Key Capabilities

Zero-Knowledge Frontend

The frontend application never sees the Access Token. It only holds a session cookie. This renders XSS attacks ineffective for token theft.

Just-In-Time (JIT) Provisioning

Automatically provision users in your local database when they log in via a trusted provider (like a corporate Azure AD).

Advanced Security

• AES-256 Encryption: Session cookies are encrypted using ASP.NET Data Protection, which uses AES-256-CBC by default. Even if an attacker intercepts the cookie, the token payload inside is unreadable without the server’s Data Protection keys.
• Partitioned Cookies (CHIPS): Browsers are restricting third-party cookies. The broker activates the Partitioned cookie attribute automatically when your app uses SameSite=None with HTTPS, ensuring the cookie remains usable in cross-site embedding scenarios. Most apps use the default SameSite=Strict and are unaffected.
• Strict CSRF: Uses the Double-Submit Cookie pattern. The server sets an XSRF-TOKEN cookie that JavaScript can read. Every POST must echo that value in an X-Primus-CSRF header. A third-party site cannot read your cookie, so it cannot forge a valid request.

Why can I see the cookie in another browser tab?

Both tabs are the same origin — browsers correctly share cookies across all tabs from the same website, and this is expected. The XSRF-TOKEN cookie is deliberately readable by your own JavaScript (it is not HttpOnly) so your frontend can echo it as a header.

The protection works at the domain level: a completely different website (for example, evil.com) cannot read your XSRF-TOKEN cookie due to the browser's Same-Origin Policy, so it cannot forge a valid X-Primus-CSRF header. Your own tabs can always see the cookie — a malicious third-party site cannot.

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Next Steps

Quickstart — get running in 15 minutes →

• Provider Setup — where each provider credential and metadata value comes from
• Database Setup — persist users with EF Core (SQLite, PostgreSQL, SQL Server)
• Advanced Configuration — custom stores, HA clustering
• Edge Cases — callback, MFA, and SSO troubleshooting
• Endpoint Reference — every /api/auth/* endpoint

Technical Specifications

Feature	Default Value	Description
Session Lifetime	60 minutes sliding	Session resets on every active request (SlidingExpiration = true). Configure via Jwt:ExpiryInMinutes in appsettings (default: 60).
Cookie Name	Primus.Session	Prefixed with __Host- in non-development environments for maximum browser security.
Session cookie mode	Cookie (HttpOnly)	Default. Browser never sees the token. Switch to JWT mode by setting IssueLocalJwt: true — used only when your stack needs a Bearer token instead of a cookie.
CSRF Cookie	XSRF-TOKEN	Readable by JavaScript (intentional). Set automatically on the first request through the broker middleware. Calling GET /api/auth/providers is the recommended first step.
CSRF Header	X-Primus-CSRF	Required on all POST requests to /api/auth/*. Your frontend reads XSRF-TOKEN and sends its value in this header.
Login rate limit	5 attempts/min per IP	Applies when BotProtection.Enabled = true. Returns 429 Too Many Requests with a Retry-After header. Not enabled by default.
Token Encryption	ASP.NET Data Protection	Any upstream token stored in the session cookie is encrypted using ASP.NET Data Protection (AES-256-CBC). For multi-node deployments, share keys using AddPrimusBrokerDataProtection().
Upstream Token Refresh	Not yet supported	Upstream access tokens (Azure AD, Auth0, etc.) are not automatically refreshed. When they expire, downstream API calls forwarding the token receive 401. Use the provider’s own SDK (e.g. MSAL) for long-lived API access.
Partitioned Cookies (CHIPS)	Off by default	Activated automatically when SameSite=None and HTTPS are both enforced. Most apps use the default SameSite=Strict and are unaffected.