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Sophos Firewall WAF Policy Crashing System

John Groller

Hello Sophos Community

Using the latest firmware as of today (SFOS 19.5.0 GA-Build197) on Sophos Firewall, installed as a virtual appliance in Proxmox 7.3-4.  It's a home license, on 4 virtual CPUs (host), and 6GB memory.  I'm using the official qcow2 images.

I am hosting a Wordpress blog behind it, using WAF, which I use mainly for sharing family pictures and videos.  Below is a screenshot of the policy.

When this policy is applied to the firewall rule, everything works fine until I attempt to upload a very large file to the blog.  Recently, I attempted to upload our family's Christmas morning video to my site, which was 1.3GB.  Not only did it fail, but the entire firewall crashed... and crashed hard.  The house went offline, DNS resolution went down, I couldn't connect to the firewall via the IP address, nothing.  It just died.  I had to go into Proxmox, kill the VM, then restart it.  Upon restart everything was fine.

If I remove the WAF policy, the file uploads.  If I enable the WAF policy and transfer the file, everything comes crashing down.  It's a very easily reproduced.  What could be causing this?



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  • in reply to John Groller +2 suggested

    Yes, unfortunately the UI doesn't allow you to skip a rule on site path level, you can only do that in the protection profile, which is applied to the whole WAF rule.

    What you can do is block access to /wp-admin from any network in the original WAF rule, and create a second rule that only provides access to /wp-admin with another protection policy that has the problematic rule skipped.

    This also allows you to have better control over who can access wp-admin. I guess the best practice would be to totally lock down this path from the Internet and only allow access to it from your internal network or from specific IPs, that way no attacker can access it. But this is just tweaking you can think about, not related to the original problem.

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  • 0 in reply to John Groller

    Alright, here's what I saw on this test:

    • File is a 1.3gb MP4 video.  Using Wordpress's built-in media uploading feature.
    • After about 1 minute all connections went down and the firewall froze.
    • Below I was able to capture "top" numbers in the firewall before the SSH session failed/froze
    • I saw a spike in Proxmox for the VM's memory and CPU... but they don't strike me as problematic.
    • The CPU spike did coincide with the firewall becoming unavailable.
    • After another minute or two, the firewall recovered itself and everything came back to life (except for the SSH session).
    • The firewall's downtime coincided with the CPU spike.
    • The transfer is hanging indefinitely, and presumably will eventually fail.

    NOTE: If not explicitly approved by Sophos support, any modifications
    top - 11:33:07 up 22:21,  2 users,  load average: 4.52, 1.14, 0.43
    Tasks: 464 total,   3 running, 459 sleeping,   0 stopped,   2 zombie
    %Cpu0  :  13.1/48.8   62[|||||||||||||||||||||||||||||||||||||                       ]     %Cpu1  :  17.3/56.5   74[||||||||||||||||||||||||||||||||||||||||||||                ]
    %Cpu2  :  15.2/67.3   82[|||||||||||||||||||||||||||||||||||||||||||||||||           ]     %Cpu3  :  19.4/46.7   66[||||||||||||||||||||||||||||||||||||||||                    ]
    GiB Mem : 99.8/5.8      [                                                            ]
    GiB Swap: 74.9/4.0      [   

  • 0 in reply to John Groller

    Hello there,

    Thank you for contacting the Sophos Community.

    Did you try the suggestion Attila mentioned?

    What does the Sophos Firewall system graphs at around that time?

    Do you see anything under /var/cores?

    Regards,

     
    Emmanuel (EmmoSophos)
    Technical Team Lead, Global Community Support
    Sophos Support Videos | Product Documentation  |  @SophosSupport  | Sign up for SMS Alerts
    If a post solves your question use the 'Verify Answer' link.
  • 0 in reply to emmosophos

    I have not tried Attila's suggestion yet.  I work from home, so I can't be bringing my firewall down over and over :-).  I will report back when I know more, but on first glance, I'm not seeing an association between WebDAV and Wordpress for the media upload  capability.

    In the end it's less about the ability to upload the files, and more about the fact that the firewall crashes when I attempt to upload something which, perhaps, is unsupported.  A more graceful solution for that would definitely be appreciated... I could always upload stuff another way.  I'll report back as I learn more.

    As for /var/cores, I looked in there just now, during normal operation, and see nothing.

    SFVH_KV01_SFOS 19.5.0 GA-Build197# ls -l /var/cores
    SFVH_KV01_SFOS 19.5.0 GA-Build197#

    As for the Sophos Firewall system graphs, the test today was around 11:30.