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romank
romank
Explorer III
September 14, 2023
Question

FortiWeb - Cookie signed verification failed

  • September 14, 2023
  • 3 replies
  • 4662 views

coockie security profile setup.pngcoockie security profile setup_log.pngHello,

I have a few services exposed over FortiWeb, many profiles enabled including "Cookie Security Policy"

im struggling witj error below that is blocking trafic if"alert_and_deny" im not sure why there is "signed verification failed". How to troubleshoot it?

Cookie name (AMP_899c7e29a9), signed verification failed; track lost; Domain: some.domain..com; Path: /somepath/

3 replies

spoojary
Staff
spoojary
Staff
September 14, 2023

The error you're seeing from FortiWeb's "Cookie Security Policy" suggests a possible integrity issue with the AMP_899c7e29a9 cookie. To troubleshoot:

  1. Review the Policy: Familiarize yourself with FortiWeb's "Cookie Security Policy" settings to understand its cookie verifications.
  2. Check Logs: Examine FortiWeb logs for deeper insights on the error. Look for patterns like specific sources or times.
  3. Origin & Integrity: Determine which service sets this cookie. Ensure it's generated and signed correctly per FortiWeb's standards.
  4. Client-Side Checks: Use a clean browser environment to check if browser extensions or scripts are affecting the cookie.
  5. Adjust Policy: Based on your findings, either modify the service setting the cookie or fine-tune the FortiWeb policy.
  6. Documentation & Support: Refer to FortiWeb's official documentation for more insights, and if unresolved, contact Fortinet's technical support.

 

    romank
    romankAuthor
    Explorer III
    September 14, 2023

    Of course i did check logs and seen which particular cookie is problematic, but i dont understand why is it.. I guess i'll need to get deeply into this - how forti is processing it. There must be sth that couses such errors. I suspecting at first " track lost".

    Its weird for me that forti couldn't check such cookie, so it will not prevent poisoning.

    anignan
    Staff
    anignan
    Staff
    September 14, 2023

    Hi @romank 

     

    It is happening for all users? Seems like a device is changing the cookie which is not matching the one that is being cache by FortiWeb for the session.

     

    Abdel

    NSE4,5x2,6x2,7x4

     

    romank
    romankAuthor
    Explorer III
    September 15, 2023

    Yes, its happening for all users, I was also thinking that maybe there is some expiration date on destination server? i did enable expiration of cookie for 15min  - just for testing but no special result i got :)

    shafiq23
    Staff & Editor
    shafiq23
    Staff & Editor
    September 19, 2023

    Hello romank,

     

    As per FortiWeb Administration Guide on Cookie Security "Signed" mode, FortiWeb will track cookies value responded by web server in the first HTTP/S request from the client, hash it and track if there is any tampering in the following requests.

     

    https://docs.fortinet.com/document/fortiweb/7.2.4/administration-guide/2851/cookie-security

     

    The cookie name mentioned (AMP_899c7e29a9) value may have changed and FortiWeb took action according to configured action in the cookie security policy. Please refer below for possible solutions;

     

    1. Change to "Encrypted" mode - works in some cases where cookies value keeps on changing(not preferred if you would like to prevent cookie poisoning attack)
    2. Do exceptions according to the cookie name

     

    Thanks.

     

    Regards,

    Shafiq

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