SAML (Security Assertion Markup Language) and OAuth (Open Authorization) are two of the most common user authentication and authorization protocols. Both of them help manage identity and access using tokens, but they serve different purposes and operate in different contexts. This blog explains the key similarities and differences between SAML and OAuth and the specific use cases where they are most commonly employed.
Getting Started: A Helpful Analogy
The core difference between SAML and OAuth lies in the nature of the tokens they use. SAML will hand you a big, official-looking XML token. It’s stamped, notarized, and smells like paperwork. OAuth, in contrast, tosses you a little JWT token and says “Here, this will get you into the VIP section for a few hours. Just don’t lose it.”
Here’s a handy way to visualize this difference. SAML is like going to an exclusive party where you wonder if you are even going to get admitted. Thankfully, a friend of yours comes to the door and says, “This person is with me; they’re cool,” so the host lets you in, no questions asked, and you get to stay as long as you like.
OAuth is more like someone loaning you their car. They don’t give you access to their house or their bank account or their bicycle — just their car. Similarly, OAuth authorizes specific things without giving away all your info. You’ve probably seen this when you click on “Log in with Facebook” or “Log in with Google.” Facebook or Google gives the app you want to access to just enough information to get the job done — like your name and email address — but not your whole life story. In particular, OAuth doesn’t share your password with the app. Instead, it gives a special web token that says, “This person is allowed to do X, Y and Z.”
Deeper Dive: SAML (Security Assertion Markup Language)
We said SAML is like a friend vouching for you to get into a party. With SAML, you are requesting access not to a party but to an application or service, and the friend is an identity provider (like Google or your company’s internal system), which tells the service that it has already authenticated you so the service should grant your access request.
Primary Use Case
The primary benefit of SAML is enabling single sign-on (SSO) — allowing users to authenticate once and then access multiple systems without having to sign in again or use separate accounts.
Accordingly, SAML is ideal for environments where SSO is critical, such as enterprises in the education, healthcare and government sectors. If you are managing users across multiple applications in different domains and want to simplify authentication without forcing users to log in multiple times, SAML is the go-to protocol.
How SAML Works
SAML involves three primary components:
- User — The person trying to gain access
- Service provider — The host of the application or service the user wants to access
- Identity provider — The entity that authenticates the user
These components interact as follows:
- A user tries to access an application or service.
- The service provider redirects the user to the identity provider for authentication.
- The identity provider checks that the user has already been authenticated (and if not, performs the authentication step), and sends back an XML token vouching for the user.
- Based on the XML token, the service provider grants the user access to the app or service.
Key Features of SAML
- Federated identity — Allows for an identity to be shared across different domains
- SSO — Enables seamless authentication across different systems
- Enterprise use — Used primarily in B2B environments, where secure identity sharing across internal and third-party applications is critical
- XML-based — Relies heavily on XML for communication between parties
Advantages of Using SAML
- Reduced risk of account compromise — Since users need only one set of credentials, they’re more likely to choose strong passwords and be able to remember them without resorting to risky workarounds like writing them down.
- Reduced IT overhead — Fewer password resets and support tickets related to login issues saves time for both users and IT staff.
- Reduced risk of password theft — Passwords are not transmitted between the user and service provider.
Deeper Dive: OAuth
We said that OAuth is like a friend allowing you to use their car but not any of their other belongings. Similarly, OAuth authorizes a limited set of access permissions without sharing your password. For example, OAuth enables you to authorize a third-party app or website to access your Facebook photo — without exposing any of the other information that Facebook stores about you, including your login credentials.
How OAuth Works
The primary components of OAuth are:
- Client — An application that is requesting access to a resource on behalf of a user
- Resource owner — The user or system that owns the data or application being requested and can grant access to it
- Authorization server — The server that issues tokens after user consent
- Resource server — The API or service storing the resource
Here’s the process:
- A user wants grant a client application access certain data about them, which is held by a resource owner.
- The client requests authorization from the appropriate authorization server.
- The authorization server authenticates the client, gets consent from the resource owner for access, and sends an access token to the client.
- Using the access token, the client requests access to the desired resource from the resource server.
Use Cases for OAuth
OAuth is best suited for consumer-facing applications and situations where third-party apps need limited access to user data. For example, if you are building a mobile app that needs to access data from an external API, OAuth provides a secure and standardized way to grant that access without compromising the user’s credentials.
Key Features of OAuth
- Focused on authorization — Designed to grant third-party access to resources without sharing credentials
- API-centric — Widely used for securing access to APIs, especially in mobile, web and cloud applications
- Token-based —Uses access tokens (usually in JSON format) to allow or deny access
- Consumer-focused — Commonly used in B2C applications like Facebook and Google.
Advantages of Using OAuth
- Reduced risk of breaches — OAuth uses tokens that grant access to only specific resources for a limited time.
- Flexibility — OAuth can be used with mobile devices, desktops, web browsers and IoT devices.
- Increased customer satisfaction — Organizations can use a trusted third-party authorization systems like Google or Facebook to allow access to their own resources, simplifying the customer experience.
Comparative Analysis: SAML vs. OAuth
Similarities Between SAML and OAuth
- Both OAuth and SAML enable single sign-on so users can authenticate once and access multiple services.
- Both protocols enable the sharing of identity information across multiple systems, applications or organizations.
- Both protocols enhance user convenience and security by eliminating the need for sharing or storing credentials with third-party services.
Differences Between SAML and OAuth
- OAuth uses lightweight JSON-based tokens, whereas SAML uses verbose XML-based tokens.
- OAuth is typically used for consumer web and mobile apps, while SAML is mainly used for enterprise-level SSO and identity federation.
- OAuth tokens are used to authorize access to APIs, while SAML assertions are used to establish authentication between systems.
Side-by-Side Comparison
| Feature | SAML | OAuth |
| Purpose | Authentication | Passwordless authorization |
| Focus | Single sign-on | API access |
| Token Format | XML | JSON |
| Key Use Case | Enterprise and B2B environments | Consumer web and mobile apps |
| Complexity | More complex | Lighter and more flexible |
Protocol Coexistence
SAML and OAuth can work together in systems requiring both authentication and authorization. For example, an employee might log into a corporate system using SAML, but then the system issues an OAuth access token to enable them to interact with external services or APIs such as Microsoft Graph or Google Drive.
Security Concerns and Best Practices
Token Theft and Replay Attacks
Because they are normally long-lasting, OAuth tokens are vulnerable to capture by malicious actors, who can use them to access critical data or systems. For example, OAuth tokens can be intercepted through techniques like Man-in-the-Middle attacks, or stolen from insufficiently protected storage.
To minimize these risks, organizations can use short-lived access tokens and always use HTTPS, which provides TLS encryption.
XML Signature Wrapping
An XML signature is a digital signature that is attached to an XML document, such as a SAML token. A valid signature indicates that the document comes from a trusted source and has not been tampered with. Adversaries can exploit this verification mechanism by injecting malicious data into a SAML token while maintaining a valid signature.
To defend against these attacks, organizations can require strong digital signatures and encrypt SAML tokens to protect their integrity and confidentiality.
Future Trends and Developments
Organizations are rapidly moving away from traditional password-only authentication in favor of methods like multifactor authentication (MFA) and passwordless options like passkeys. More broadly, they are adopting Zero Trust security models, which emphasize the need to “never trust, always verify.” In addition, they are embracing artificial intelligence (AI) and machine learning (ML) to enhance their threat detection capabilities.
Conclusion
While SAML and OAuth both play crucial roles in managing access to applications and data, they address different challenges: SAML focuses on confirming a user’s identity and is commonly used for SSO in enterprise environments, while OAuth is designed for granular, passwordless authorization for secure access to APIs and resources in web and mobile applications. Both protocols will support your efforts to create a smoother and simpler user experience while maintaining strong security
