SAML vs. OAuth: Understanding the Differences

This guide discusses distinctions to make between SAML and OAuth and is part of a series that will also discuss Single Sign On, Identity Access Management, and Access Control.

What is SAML and How Does it Work?

SAML (Security Assertion Markup Language) is an XML-based standard for exchanging authentication and authorization data between parties, in particular, between an identity provider and a service provider.

It is commonly used to provide single sign-on functionality, allowing users to authenticate to multiple applications with a single set of login credentials.

SAML authentication works by the identity provider (IdP) authenticating the user and then providing an assertion to the service provider (SP) to prove the user's identity.

The assertion is a document that contains information about the authenticated user and is digitally signed by the IdP.

The SP can then use the information in the assertion to grant the user access to the protected resources.

When was SAML Initially Developed and by Whom?

SAML was initially developed by the OASIS Security Services Technical Committee in the early 2000s.

It was developed by a group of vendors, researchers, and practitioners from different organizations and companies, such as IBM, Microsoft, and VeriSign among others.

What is the Latest Version of SAML?

The first version of the standard, SAML 1.0, was released in November 2002.

The latest version, SAML 2.0, was released in March 2005 and is the most widely used version of the standard.

Where is SAML Commonly Used?

SAML is commonly used in enterprise environments to provide single sign-on functionality across different applications and systems.

It is often used to authenticate users to web-based applications, cloud-based services, and other resources that are protected by a service provider.

What is OAuth and How Does it Work?

OAuth (Open Authentication) is an open standard for authorization that allows users to share their private resources (e.g., photos, videos, contact lists) stored on one site with another site without having to share their credentials, typically a username and password.

It enables users to authorize third-party applications to access their resources without sharing their passwords.

OAuth provides a way for a user to grant a third-party application access to their resources without sharing their credentials.

The user is redirected to the service provider (e.g., Google, Facebook) to authenticate and authorize the application, and the service provider then provides the user privileges to the application with an access token.

This token can be used by the application to access the user's resources on the service provider's site.

OAuth uses a token-based authentication system, where the user is issued a token that represents their authorization to grant access to the protected resources.

The token is sent with each request for a protected resource, and the service provider uses it to authenticate the user and authorize access.

What is the Latest Version of OAuth?

OAuth 2.0 is the latest version of the standard, which provides more flexibility and security compared to the previous version (OAuth 1.0).

OAuth 2.0 is widely adopted in RESTful APIs and it has become the most popular protocol for this use case.

Where is OAuth Commonly Used?

OAuth is commonly used by service providers, such as social media sites, email providers, and other web-based services, to allow third-party applications to access their users' protected resources.

This allows users to share their information and content with other applications without having to share their login credentials.

Developers of third-party applications, such as mobile apps, desktop applications, and web-based services, often use OAuth to authenticate and authorize their users to access the protected resources on a service provider's site.

By using OAuth, developers can focus on building their application's functionality without having to worry about the complexities of user authentication and the authorization process.

What are the Similarities Between SAML and OAuth?

Both SAML and OAuth:

• Are widely adopted and supported by many companies, organizations, and service providers.
• Provide a way for users to authenticate and authorize access to protected resources without sharing their login credentials.
• Use token-based systems for authentication and authorization, where the user is issued a token that represents their authorization to access the protected resources.
• Are used in enterprise environments and are often integrated with other systems and services.
• Are designed to provide a secure way to share user's protected resources between different web services and applications

What are the Differences Between SAML and OAuth?

Purpose:

SAML is mainly used for Single Sign-On and Federated Identity scenarios, while OAuth is mainly used for allowing third-party applications to access the user's protected resources on a service provider's site.

Protocol:

SAML is an authentication protocol, it allows for the exchange of authentication and authorization data between parties, in particular, between an identity provider and a service provider.

OAuth is an authorization protocol, it allows third-party applications to access the user's protected resources without sharing the user's credentials.

More information about authentication vs authorization

Token-Based System:

Both OAuth and SAML use token-based systems for authentication and authorization, but they use different types of tokens.

SAML uses assertions, which are long-lived and can be used to authenticate the user to multiple service providers.

OAuth uses access tokens, which are short-lived and can be used to access resources on the service provider's site.

Flow:

SAML uses a post-based flow, where the user authenticates to the IdP, then the IdP sends an assertion to the SP to prove the user's identity.

OAuth uses a redirect-based flow, where the user is redirected to the service provider to authenticate and authorize the application, then the user is redirected back to the application with the access token.

Flexibility:

OAuth is more flexible compared to SAML, it allows for different types of grants, such as authorization code, implicit, and client credentials, which can be used in different scenarios.

SAML is more rigid, it requires the use of a specific message format and a specific flow.

Can SAML and OAuth Work Together?

Organizations have the option to leverage both standards to offer their employees and customers a seamless Single Sign-On (SSO) experience across various applications and services.

For example, by using a SAML assertion from an Identity Provider (IdP), user identity can be verified during communication between an authorization server and a resource server.

The authorization server can utilize an OAuth token to verify user identity and grant the end user access to resources based on their security credentials.

Furthermore, certain environments may necessitate the use of both SAML and OAuth, such as in Microsoft environments.

In such cases, SAML facilitates system access grants, while OAuth enables access to protected resources.

When Should You Use SAML?

Use SAML:

• For Single Sign-On (SSO) and Federated Identity scenarios, where users need to authenticate to multiple systems and applications with a single set of login credentials.
• When you need to support a wider range of use cases and messaging formats, such as Web Browser SSO Profile, Single Logout, and Identity Provider Discovery. OAuth is mainly used for RESTful API, and it has a more narrow range of use cases.
• When you need a more secure protocol, which uses digital signatures and encryption to protect the assertion and ensure its authenticity and integrity.

When Should You Use OAuth?

Use OAuth:

• When you want to allow third-party applications to access the user's protected resources on a service provider's site without sharing the user's credentials.
• When you need a more flexible protocol, which allows for different types of grants, such as authorization code, implicit, and client credentials.