B2B Identity Federation

Securing the Supply Chain

B2B Identity Federation (Business-to-Business) is the strategic practice of extending organizational resources to external partners without compromising security perimeter integrity. Unlike standard SSO, B2B federation must account for diverse security postures, varying levels of trust, and the need for granular governance over “Guest” identities. By allowing partners to use their own credentials while maintaining centralized control over resource access, organizations can accelerate collaboration while ensuring that external access is always verified and audit-ready.

Core Mission

External Identity Governance. Providing a secure, scalable mechanism for external users to interact with internal apps while ensuring that the organization retains absolute control over the "Authorization" of those users.

Like a Gated Business Park: You own the park (The Resource Realm). You allow other companies (Partners) to rent office space. Their employees bring their own company IDs (IdP-managed). However, you control the main gate, you assign the badges that unlock specific buildings, and you can revoke those badges instantly if a partnership ends—even if their home ID is still valid.

Supplier Portals / Joint Ventures / SaaS Vendor Management

Partner Onboarding Matrix

The onboarding pattern determines how much manual effort is required to manage external identities.

Strategic Onboarding Comparison

Model	Mechanism	Friction	Security Control
Whitelisted (Invite)	Admin sends unique link.	High	Highest (Pre-vetted).
Self-Service	Verified domain signup.	Low	Medium (Domain-locked).
JIT (Federated)	Account created on first login.	None	Low (Reactive).
Directory Sync	Cross-tenant group sync.	Medium	High (Deep Integration).

The Partner Onboarding Journey

Successful B2B collaboration requires a disciplined lifecycle that balances speed with verification.

graph LR
    Invite[Invite Partner] --> Hydrate[Hydrate Profile]
    Hydrate --> Verify[Verify Domain/MFA]
    Verify --> Activate[Activate Access]
    Activate --> Audit[Periodic Review]

Identify & Verify

The partner admin or user initiates registration. The system verifies the partner's domain and ensures their Identity Provider (IdP) meets minimum security requirements (e.g., mandatory MFA).

Map & Authorize

External groups/roles are mapped to internal permissions. This "Identity Translation" ensures that a partner's 'Lead Engineer' receives only the necessary access to specific internal project repos.

Govern & Rotate

Access is time-bound or subject to periodic "Access Reviews." If the user leaves their home organization, the federated link is automatically severed, preventing orphaned access.

Technical B2B Governance

Implementing B2B trust requires rigorous attribute validation and tenant-based isolation.

Partner Access Evaluation (Java Example)

// Simplified B2B Access Policy Entry
public AccessDecision evaluatePartnerAccess(String partnerId, String userId, String resourceId) {
    // 1. Verify Partner Status
    PartnerConfig partner = repository.getPartner(partnerId);
    if (!partner.isActive()) return AccessDecision.DENY;

    // 2. Enforce IP/Location Restrictions
    if (!isAllowedIp(partner.getWhitelistedIps())) return AccessDecision.DENY;

    // 3. Confirm MFA Assurance
    if (!isMfaVerified(userId)) return AccessDecision.REQUIRE_STEPUP;

    // 4. Final Role Validation
    return checkPermissions(userId, resourceId);
}

Federation Pattern Guides

Master the implementation of secure, partner-centric identity architectures.

Next Steps

Explore Cross-Tenant Sync for deep collaboration between Azure AD or Okta organizations.
Review Tenant Separation Patterns to ensure partner data isolation.
Check Conditional Access for Guests to enforce security baselines on external identities.