SSO Implementation Guide: From Legacy Applications to Modern Identity Platforms

 


Typically, enterprise applications don't rely on just one authentication method. A company can have modern cloud applications as well as older applications that rely upon headers, passwords, LDAP, Kerberos, or NTLM. The combination can complicate an SSO implementation more than just integration of applications to an identity provider.

The journey towards a successful migration begins with knowing what each application supports and progresses towards a centralized authentication without impacting critical business systems.

Start With an Application Inventory

Prior to changing authentication, establish an application listing of the applications that employees are using. This ensures that systems that are not as obvious and older systems are not overlooked.

For each application, identify:

  • Who uses it and how critical it is

  • Where it is hosted

  • Its current authentication method

  • Whether it supports SAML or OpenID Connect (OIDC)

  • Dependencies on directories or existing identity systems

  • Whether authentication can be modified

In this exercise, it typically turns out that there are various application classes. Some are ready to be modern federated, others need more integration.

Sort Applications by Authentication Type

A practical migration does not treat every application identically.

Application Type

Typical Authentication

Possible SSO Direction

Modern web app

OIDC, OAuth 2.0

Connect to modern identity platform

Enterprise SaaS

SAML, OIDC

Federated SSO

Traditional enterprise app

SAML

Federated SSO

Legacy internal app

Kerberos, NTLM, LDAP

Bridge, proxy, or modernization

Password-based app

Username/password

Password-based SSO where supported

OIDC is an identity layer on top of OAuth 2.0 that can be better applied to modern web and mobile applications, while SAML is broadly used for enterprise federation.

Decide What Should Move First

The risk of trying to move the whole application portfolio at once is unnecessary.

Generally, a staged approach is easier to manage.

Wave 1: Modern applications

Start with SAML- or OIDC-enabled applications. They tend to be less intrusive with regard to redesigning the authentication environment and can be used to support the new identity environment.

Wave 2: Configurable business applications

Next, address applications that can support federation after configuration changes, connector deployment, or application updates.

Wave 3: Legacy applications

Lastly, assess applications that are related to older authentication methods. Some will be modernized, others may require an intermediate access method as it is not feasible to change the underlying application.

Choose the Right Protocol Instead of Forcing One

Standardization doesn't mean all applications should use the same protocol.

SAML 2.0 is based on XML assertions for the exchange of authentication and attribute information. OIDC employs contemporary patterns in web-based authentication, and is well suited to newer application architectures.

Applications can then use the protocols that are appropriate for their architecture, and the identity platform will offer centralized authentication

Add Security Controls Around SSO

While SSO enhances user experience, strong authentication still matters.

Organizations should consider combining single sign on software with controls such as:

  • Multi-factor authentication

  • Passwordless authentication

  • Context-based access policies

  • Device-related access requirements

  • Role and group-based authorization

  • Authentication and access monitoring

Centralizing authentication can make these controls easier to apply consistently because identity policies no longer have to be managed separately within every compatible application.

Test Before Each Migration Wave

The authentication changes can impact more than just the login screen. Test user attributes, group mappings, application roles, session behavior, logout and account access prior to production.

Test with the following users: normal users, administrators, remote users and important application workflows. It is also important to have a rollback plan if there is a deviation from the integration behavior in production.

Build SSO as an Identity Foundation

It's not just about eliminating passwords when it comes to the strongest SSO strategy. It provides a shared authentication layer on a mixed application environment.

Inventories of applications, groups based on authentication, and incremental migrations in waves combined with more stringent access policies allow enterprises to modernize their identity incrementally. Legacy applications don't need to be phased out immediately. They can be dealt with on a technical basis, while newer applications adopt standards-based authentication and a more common identity architecture.

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