Troubleshooting SSO Issues: Capturing and Decoding SAML Responses

Updated at: 01/07/2025

Single Sign-On (SSO) simplifies access, but troubleshooting failures can be complex. This article empowers you to effectively diagnose SSO problems by focusing on SAML responses. We'll guide you through capturing these crucial messages and decoding their contents, revealing the root cause of authentication issues. Learn to interpret SAML attributes, identify error codes, and resolve common SSO headaches efficiently. Let's get started!

Step-by-Step Instructions

  1. Initiate SSO in Incognito Mode

    • Open an incognito browser window.
    • Navigate to the service provider initiated URL.
    Navigate to the service provider initiated URL. Navigate to the service provider initiated URL.
    Initiate SSO in Incognito Mode

  2. Capture SAML Response

    • Open the developer console (usually by pressing F12).
    • Go to the 'Network' tab in the developer console.
    • Click the link that initiates the SSO process.
    • Locate the SAML response in the network requests. This will likely be a base64 encoded string.
    Locate the SAML response in the network requests. This will likely be a base64 encoded string. Locate the SAML response in the network requests. This will likely be a base64 encoded string. Locate the SAML response in the network requests. This will likely be a base64 encoded string.
    Capture SAML Response
    • Copy the entire base64 encoded SAML response.
    Copy the entire base64 encoded SAML response.
    Capture SAML Response

  3. Decode SAML Response

    • Paste the response into Notepad++.
    • Use the Base64 decode plugin (like Mimi tools) in Notepad++ to decode the response.
    Use the Base64 decode plugin (like Mimi tools) in Notepad++ to decode the response. Use the Base64 decode plugin (like Mimi tools) in Notepad++ to decode the response.
    Decode SAML Response

  4. Analyze Decoded SAML Response

    • Examine the decoded SAML response for errors or relevant information such as email addresses, Federation IDs, and session IDs.
    Examine the decoded SAML response for errors or relevant information such as email addresses, Federation IDs, and session IDs.
    Analyze Decoded SAML Response
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Tips

  • Using an incognito window ensures a clean session without interference from browser cache or extensions.
  • The specific location of the SAML response in the network tab might vary depending on your browser and the SSO provider.
  • Notepad++ with a Base64 decoding plugin simplifies the decoding process.
  • The decoded SAML response will contain valuable information to pinpoint SSO issues; examine the attributes carefully.

Common Mistakes to Avoid

1. Incorrect SAML Endpoint URLs

Reason: Using the wrong Assertion Consumer Service (ACS) URL or Identity Provider (IdP) Single Sign-On (SSO) URL will prevent successful authentication.
Solution: Double-check the URLs in your Identity Provider and Service Provider configurations for accuracy.

2. Certificate Mismatch or Expiry

Reason: The certificates used for signing and encrypting the SAML response need to match between the IdP and Service Provider; expired certificates will cause authentication failures.
Solution: Verify that both the IdP and SP certificates are valid, correctly configured, and match.

3. Incorrect NameID Format or Attribute Mapping

Reason: The Service Provider may expect a specific NameID format or attributes in the SAML response which the Identity Provider doesn't provide or provides differently.
Solution: Ensure the NameID format and attribute mappings are correctly configured on both the IdP and SP to match expectations.

FAQs

How do I capture a SAML response?
The method for capturing a SAML response depends on your browser and network setup. Common approaches include using your browser's developer tools (Network tab) to intercept the response, employing a proxy server like Charles Proxy or Burp Suite, or utilizing browser extensions designed for network monitoring. Look for XML data containing SAML assertions within the response. Remember to respect privacy and only capture your own responses.
What should I look for when decoding a SAML response?
First, check the `<StatusCode>` element for error codes indicating authentication failures (e.g., `urn:oasis:names:tc:SAML:2.0:status:Responder`). Next, examine the `<Assertion>` element for attribute values. Look for missing or incorrect attributes (like `NameID` or user roles) which might explain why SSO isn't working correctly. Pay close attention to any error messages embedded within the response itself.