Central Authentication & Authorizationin Multi Cloud

Excellent — this is one of the most common and deep-dive questions Enterprise Architects get in interviews 👇

❓“In a multi-cloud hybrid environment, how do you manage authentication and authorization consistently across Azure, AWS, and on-prem?”

Let’s break it down step-by-step, like a real-world Enterprise Architect explaining it to a CTO panel.

🧩 Step 1: Understand the Core Challenge

In multi-cloud setups, you have:

• Workloads across Azure (AKS, APIM), AWS (EKS, API Gateway), and On-Prem (VMware, Finacle, Oracle)

• Users, partners, and apps that need to authenticate once and access services across these clouds

• Different cloud-native IAM systems (Azure AD, AWS IAM, GCP IAM), each with its own identity model

So the challenge:👉 How to create a single, consistent identity and access model across all clouds + on-premwithout duplicating identity or having fragmented access control.

🧱 Step 2: Adopt a Centralized Identity Provider (IdP)

In production, banks and large enterprises NEVER depend on cloud-native IAM alone.

They use a central enterprise-grade Identity Provider that acts as the single source of truth for identity and access.

Identity Provider	Typical Enterprise Usage
Azure AD / Entra ID	Most common in BFSI
Ping Identity / PingFederate	Often used in banks for hybrid setups
Okta / ForgeRock / IBM Security Verify	Large global organizations
On-Prem AD + Federation	Legacy coexistence

So, all clouds (Azure, AWS, GCP) trust this single IdP via federation.

🛠️ Step 3: Authentication (AuthN) Flow

Let’s see how a real authentication flow happens step by step in production:

🔹 Scenario:

Customer logs into api.deuebank.com/lending/applyLending is hosted on Azure, CRM on AWS, and core systems on on-prem.

🔸 Step-by-step Authentication:

1. User Access Request

   • User tries to access Lending Portal (Azure Front Door URL).

2. Redirection to Central IdP

   • App redirects to Azure AD (or PingFederate) for authentication.

   • This IdP is federated with AWS IAM and On-Prem AD.

3. Credential Validation

   • User enters credentials (could be username/password, certificate, or SSO).

   • IdP validates it against enterprise directory (Active Directory / LDAP).

4. Token Issuance

   • On successful authentication, IdP issues:

     • OIDC ID Token (for user identity)

     • OAuth2 Access Token (for API access)

     • JWT format, signed with the IdP’s private key.

5. Token Validation by APIs

   • API Gateways (Azure APIM, AWS API Gateway, On-Prem Kong) validate the same JWT using the IdP’s public key (JWKS endpoint).

   • No matter which cloud the API is in, it uses the same token validation logic.

✅ Result: Single Sign-On (SSO) across Azure, AWS, and On-Prem.

🧰 Step 4: Authorization (AuthZ) Flow

Once authenticated, authorization defines what you can do.

Authorization happens at 3 layers:

Layer	Responsibility	Tools / Mechanism
1. Gateway-level	Enforce API scopes, rate limits	Azure APIM policies / Apigee / Kong
2. Service-level	Fine-grained access (e.g., view loan, approve loan)	Role-based / Attribute-based access control (RBAC/ABAC)
3. Data-level	Row-level / column masking	Database-level RBAC or policies

🔸 Step-by-Step Authorization Example:

Continuing our Digital Lending use case 👇

1. API Gateway (Azure APIM) validates the OAuth2 token.

   • Token claims:

     { "sub": "anand.nirurkar", "roles": ["LoanOfficer", "Underwriter"], "scope": "loan.read loan.approve" }

2. Gateway Enforces Scopes

   • Only requests with scope loan.approve can call the /approve endpoint.

3. Backend Microservice

   • Uses the same JWT claims (via Spring Security or OAuth2 Resource Server)

   • Authorizes based on roles/attributes in the token.

4. Cross-cloud Authorization

   • AWS microservices (CRM) and On-Prem services (CBS Adapter) use the same token introspection endpoint from the central IdP.

   • Therefore, no re-login is needed.

✅ Result: Unified role-based access across all clouds and systems.

🔐 Step 5: Token Federation & Trust Setup

Cloud	Trust Mechanism	Description
Azure Cloud	Azure AD Enterprise App Federation	Trusts central IdP via SAML / OIDC
AWS Cloud	AWS Cognito Federation / IAM OIDC Provider	Trusts same IdP for token validation
On-Prem	PingFederate / ADFS / Keycloak	Trusts same IdP via SAML

💡 So, the same JWT or SAML assertion is valid across all environments.

🧩 Step 6: Real Production Security Controls

Concern	Control	Implementation
MFA (Multi-Factor Auth)	Required for admin & sensitive roles	Azure AD / Ping MFA
Token Lifetime	Short-lived (15–30 min)	Rotated via refresh tokens
Zero Trust Access	Validate every request	No implicit trust between networks
Service-to-Service Auth	mTLS + Service Identity (SPIFFE / SPIRE)	Inside mesh (Istio, Dapr)
Secrets Management	Centralized vault	HashiCorp Vault / Azure Key Vault
Audit & Logging	SIEM Integration	Splunk / Azure Sentinel

🧠 Step 7: How Enterprises Operate This in Practice

• Azure AD (or PingFederate) acts as central identity hub.

• All APIs in Azure, AWS, and on-prem are registered with the same IdP.

• Global API Gateway (Apigee / Kong) uses OAuth2 + OpenID Connect tokens.

• Service meshes (Istio / Dapr) inside clusters perform mTLS for internal authentication.

• Auditing, access logs, and token traces are centralized in Splunk or Sentinel.

✅ Summary

“In our multi-cloud architecture, we use a central identity provider — Azure AD integrated with PingFederate — as the single source of truth for authentication and authorization.All workloads across Azure, AWS, and on-prem trust this IdP using OIDC and SAML federation.This ensures that a user or service authenticated once can securely access resources across any environment using a JWT-based OAuth2 token.Authorization is enforced at multiple layers — API Gateway, microservices, and data — using scopes, roles, and attributes embedded in the token. Service-to-service authentication uses mTLS and SPIFFE-based identities within service meshes like Istio. This gives us centralized identity management, consistent access control, and full auditability across multi-cloud and hybrid systems — meeting RBI and GDPR compliance.”