PCNSE Practice Question: Securing Users and Applications with Authentication
After configuring SAML authentication for GlobalProtect, users report they are repeatedly prompted for credentials even though they already authenticated via the IdP. The firewall logs show 'saml-auth-success' but the portal log shows 'user-login-failure: invalid saml assertion'. What is the most likely cause?
⚠ Common exam trap
The trap here is that candidates see 'saml-auth-success' and assume the authentication succeeded end-to-end, but they miss that the firewall's portal log rejection indicates a validation failure on the assertion itself, not a failure at the IdP.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The firewall and IdP system clocks are out of sync
The firewall logs show 'saml-auth-success' (meaning the IdP successfully authenticated the user and issued a SAML assertion), but the portal log shows 'user-login-failure: invalid saml assertion'. This indicates the firewall received the assertion but rejected it as invalid. The most common cause for a validly signed assertion to be rejected is clock skew between the firewall and the IdP, because SAML assertions contain timestamps (NotBefore and NotOnOrAfter conditions) that are checked against the local system clock. If the clocks differ by more than the allowed skew (typically 5 minutes), the assertion is considered invalid even though it was correctly signed.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The IdP does not support IdP-initiated SAML flow
Why it's wrong here
GlobalProtect uses SP-initiated flow, so IdP-initiated is not required.
- ✗
The user mapping agent is not configured
Why it's wrong here
User mapping is for user identification, not SAML authentication.
- ✓
The firewall and IdP system clocks are out of sync
Why this is correct
Time skew can cause SAML assertion validation failure.
- ✗
The SAML identity provider certificate is expired
Why it's wrong here
Expired certificate would cause a different error, not invalid assertion.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCNSE practice question is part of Courseiva's free Palo Alto Networks certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCNSE exam.