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Sophos Firewall: v19.5 GA: Feedback and experiences

Release Post:  Sophos Firewall v19.5 is Now Available 

Old v19.0 MR1 thread:  Sophos Firewall: v19.0 MR1: Feedback and experiences 

EAP Sub thread:  SFOS v19.5 Early Access Program 

EAP 19.5 Thread:  Sophos Firewall: v19.5 EAP1: Feedback and experiences 



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  • This is indeed expected behavior of the FCI feature.  What follows is a Draft of a KB Article I'm writing (feedback welcome).



    In XG 18.0 the DPI proxy was introduced, with many more SSL/TLS scanning options and certificate protection. There are some certificate security concerns with that are blocked in most configurations, however they are allowed without any warning when using DPI mode with the decryption profile "Maximum compatibility". In these cases the XG decrypts and re-signs, creating a new certificate with its own Certificate Authority that hides potential problems that the end user should know about which that would be blocked in other configurations.

    In 19.0 a new feature was added called Forward Certificate Invalidity (FCI). This feature detects certain types of certificate invalidity and "forwards" (tells the user) about them. Because we cannot create a certificate with the same error, so we create one in a special way that we know will cause browsers to warn users. A CA is used that us unique and untrusted, and the certificate Common Name is used as the error message to tell the end user what the problem is. This changes the behavior of DPI mode with Maximum Compatibility. By signing it in the way, browsers will warn users that there is a certificate problem but will allow users to proceed and load the pages as they did in 18.0/18.5.

    The most common issue that FCI catches on the public internet is websites that do not send their entire certificate chain. When a website provides their certificate, they usually provide the certificate, the CA that signed it (usually an intermediate CA), the CA that signed that one, up to the root CA. The root CA is trusted by the browser, and the browser can verify the entire chain.

    However some websites do not provide the chain. They may provide only the certificate, or they provide the certificate and the root CA, but they do not provide the intermediate CA. While this is valid, it is not best practice and sites like ssllabs.com which rate sites will cap their score.

    If a website does not provide the chain they usually implement AIA (Authority Information Access). This is a link within the certificate that says where to download the CA that signed it.

    Some browsers (Chrome 58+, Edge, Safari) will automatically use the AIA to download the intermediate and store it for future use. Firefox 75+ uses a different mechanism called intermediate CA preloading (wiki.mozilla.org/.../Intermediate_Preloading). Older Android (pre Oreo) devices do not support any mechanism. The XG does not currently support AIA.

    If the website does not provide the full chain, the XG behavior depends on the configuration. It is important to note that v19 did not introduce blocking of sites that do not provide the full chain. The XG has always blocked these sites when using normal security, and the resolution below has always worked. The difference is that when using a decryption profile that does not block self signed certificate, invalid issuers, or many other security concerns (such as "Maximum compatibility") we used to allow the connection and sign it in a way that made it appear more secure. Now we allow but sign it in a way that appears insecure.

    How to configure the system to allow access to sites that do not provide a complete certificate chain.

    Method 1 - Do not decrypt
    Configure the domain to not be decrypted. Adding the domain to the Local TLS Exclusion List is the best option for DPI mode. Adding it to a Web Exception will exclude it for both DPI and Proxy mode.

    Method 2 - Add the Intermediate certificate to the XG CA store

    Option 1:
    Test the site in www.ssllabs.com/.../
    You should see that the grade is capped to B and the Certification Path includes an "Extra Download". In the section under Issuer there should be an AIA link.

    Option 2:
    Use a browser that is not going through the XG, or is going through the XG with HTTPS not decrypted so that you get the original certificates as presented by the site. Ask the browser to display the certificate information and the AIA link should be there. How this is displayed is browser specific.

    Once you have the AIA link, download the certificate to your computer. Then in WebAdmin go to Certificates > Certificate Authorities and Add. Choose the file.
    With the Intermediate in the CA store, the page will load in all configurations.

    Jump to answer
  •  Like wise Dev team would like to investigate this setup too. Can you share access details and info as above for your installation in private message to me.

  • Others of us still having the issue, so please don't be so eager to wipe this part of the discussion out. I do not have multiple choices, I only have a single choice as I only have one firewall of one type with one license, so it's not possible for me to pick the wrong one as far as I can tell.

    The only download .sig file that I'm offered is:

    HW-19.5.0_GA.SF310-197.sig

    Not sure if that's for the XGS87 or not. (I suspect so because previous .sig files that worked were SF310 but that's just a naming convention and the contents might not match the name.)

  •    in addition to above, if we can get full backup and complete logs from /log that will help.

  • Found the fix and disabled the assistant.

    ian

    XG115W - v19.5.1 mr-1 - Home

    If a post solves your question please use the 'Verify Answer' button.

  • On my xg115w the update took a long time, then the reboot time is around 8 minutes.

    the selection menu is not user friendly. When you enter your license, then you click on your licence which then offers you software for your device.

    ian

    XG115W - v19.5.1 mr-1 - Home

    If a post solves your question please use the 'Verify Answer' button.

  • Hello Ian,

    As I communicated to you earlier (around Oct timeframe), your issue is being tracked with NC-108057.

    As per investigation done that time, this is not 19.5 specific issue but there since older releases.

    We will try to work on it in upcoming MRs.

    Regards,

    Sanket Shah

    Regards,

    Sanket Shah

    Senior Development Manager, Sophos Firewall

  • Thank you for the update and refresh. I posted because the GA does not kill the interface like the EAP version.

    ian

    XG115W - v19.5.1 mr-1 - Home

    If a post solves your question please use the 'Verify Answer' button.

  • Memory usage dropped after upgrade, sitting stable around 75% for the last 24h.

     
    SFVH (SFOS 19.5.1 MR-1-Build278)  - Last (re)boot on Februari 20 2023
    Asus H410i-plus - Pentium 6605 Gold - 250GB M.2 PCIe NVMe SSD - 8GB - 3 ports
    [If any of my posts are helpful to you please use the 'Verify Answer' link]
  • Mine is sitting at 80%, usually takes a couple of days to settle down.

    Ian

    XG115W - v19.5.1 mr-1 - Home

    If a post solves your question please use the 'Verify Answer' button.

  • **We are currently investigating the problematic scenario/use case under NC-109623 as we have not faced such issue internally during our testing.

     We worked with Jaroslav Faldik and able to resolve the problem with additional configuration of “no bgp network import-check”.  This will help overcome extra validation performed by the BGP service before advertising network that specific network should be available in RIB before advertising to peer.

    E.g.

    BGP Network Configuration:

    !

    address-family ipv4 unicast

      network 100.100.0.0/16

       maximum-paths 15

    exit-address-family

    !

    How to check if specific network is advertised to peer? 

    bgp# sh ip bgp 100.100.0.0/16

    BGP routing table entry for 100.100.0.0/16, version 18

    Paths: (1 available, no best path)

      Not advertised to any peer

      Local

        0.0.0.0 (inaccessible) from 0.0.0.0 (200.0.0.8)

          Origin IGP, metric 0, weight 32768, invalid, sourced, local

          Last update: Fri Nov 18 09:06:38 2022

    Basically, when you are seeing configured BGP network is not getting advertised to any peer, which stopped working after migration/upgrade to v19.5:

    1. Interface link is down where this subnet is configured. 
    2. Interface subnet mismatch compared to network configured in BGP e.g., in case interface subnet is “100.100.100.0/24”, and configured network is “100.100.0.0/16”.

    One can try the additional CLI command no bgp network import-check” in BGP to overcome these validations.