SAML Roulette: When Your Identity Provider Plays Dirty

SAML Roulette: When Your Identity Provider Plays Dirty
  • March 27, 2025
By: Karrie Westmoreland
Welcome to the security casino, where the chips are credentials, and the stakes are your entire enterprise infrastructure. Today’s house favorite? SAML Roulette—an attack so sneaky, it makes phishing look like a carnival game. 
 
What Is SAML Roulette? 
SAML (Security Assertion Markup Language) is like the bouncer at Club Cloud. It checks your ID (aka identity assertions) from an Identity Provider (IdP) and lets you into your favorite SaaS party—Google Workspace, AWS, Slack, you name it. 
But here’s the twist: in SAML Roulette, attackers exploit misconfigured trust relationships or signature verification errors in SAML implementations. Basically, the IdP says, “This person’s cool,” but the app forgets to check who actually said it. 
It’s like trusting anyone in a fake uniform with a clipboard. 
 
How the Game Is Played
Example #1: The Mischievous IdP: A company integrates multiple IdPs for their internal services. One is tightly controlled; the other is... let’s say, “more relaxed.” An attacker crafts a SAML response claiming to be admin@victim.com, signs it with the weak IdP’s key, and bam—they're in. No hacking, just creative trust issues. 
 
Example #2: The Parser Party: Some apps don’t check the signature on the assertion, only on the outer SAML envelope. That’s like sealing an envelope with wax, but not checking the document inside. An attacker signs a harmless outer shell, then sneaks malicious assertions inside. The app accepts the message and grants access. Oops. 
 
How to Win at SAML Security 
Want to avoid losing big at the SAML table? Here are your best bets: 
 
Strict Signature Validation
Always validate the signature on the assertion, not just the outer message. Double-check that it’s signed by a trusted IdP only. 
 
Whitelisted IdPs Only
Ensure your application only trusts specific, known IdPs. Don’t let just any SAML response through the velvet rope. 
 
Audience Restriction Checks
Make sure the assertion is intended for your app, not repurposed from another service. Think of this as checking that a love letter was meant for you. 
 
Short Assertion Lifetimes
Keep token validity windows tight—no one likes stale credentials hanging around. 
 
Test with SAML Scanners
Tools like SAML Raider or SAMLtool.com can help you simulate attacks and check for vulnerabilities in your SSO setup. 
 
 
Final Thoughts 
SAML is powerful, but misconfiguration turns it into a game of Russian Roulette—except all the bullets are labeled "root access." Don’t gamble with your cloud security. Audit, test, and verify like your job depends on it—because it does. 
 
So, next time someone says SSO is secure by design, just smile and whisper, “Not if you play SAML Roulette.” 
 

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