[OpenWrt-Devel] OpenWRT www version banner a security risk
mauritsvb at xs4all.nl
Sun Sep 13 11:34:55 EDT 2015
I see where you’re coming from but I disagree that one should always rely on the user to know exactly what to do and what not to do. A bit of basic prevention doesn’t hurt.
Wouldn’t you agree that if you follow that line you might as well argue that OpenWRT should not come with default-deny rules in the firewall? After all, anyone who is savvy enough to install OpenWRT should then also know that by default it has no firewall rules.
There is a reason that not displaying too much information in banners is good security practice. It slows down the reconnaissance phase of an attack (using “banner grabbing” tools) and can persuade many attackers to even skip a specific target. Even for complex server software and hardware that requires far more expert operators than OpenWRT it is still best practice not to give too much away about the specific version. It’s why companies such as Cisco and Juniper advise not to disclose version information in banners.
Of course, by not displaying by default but making it a configurable option any admin who requires if for support purposes could still enable it.
As for your idea about warning users that their LuCI is reachable via WAN, I agree, that definitely makes sense. However, I see that as a separate issue from displaying security sensitive information on the login page.
> On 13 Sep 2015, at 15:28, Daniel Dickinson <openwrt at daniel.thecshore.com> wrote:
> Quite frankly if someone has unintionally exposed LuCI to the internet I think they've got a lot bigger problem than exposed version information, and that not putting the version information at best delays only very slightly a would be attacker.
> And for properly configured installs, the version information is extremely useful for doing support and such like.
> Not that it likely means much, by vote is against such weak bandaid to what is fundamentally an issue a user creates for themselves that is much larger than the details of what's on the screen.
> What would be more relevent solution is for LuCI to have a banner that indicates that the LuCI is visible on the WAN, thus alerting the user to a misconfiguration, if it is that.
> On 2015-09-13 10:21 AM, MauritsVB wrote:
>> At the moment the OpenWRT www login screen provides *very* detailed version information before anyone has even entered a password. It displays not just “15.05” or “Chaos Calmer” but even the exact git version on the banner.
>> While it’s not advised to open this login screen to the world, fact is that it does happen intentionally or accidentally. Just a Google search for “Powered by LuCI Master (git-“ will provide many accessible OpenWRT login screens, including exact version information.
>> As soon as someone discovers a vulnerability in a OpenWRT version all an attacker needs to do is perform a Google search to find many installations with versions that are vulnerable (even if a patch is already available).
>> In the interest of hardening the default OpenWRT install, can I suggest that by default OpenWRT doesn’t disclose the version (not even 15.05 or “Chaos Calmer”) on the login screen? For extra safety I would even suggest to leave “OpenWRT” off the login screen, the only people who should use this screen already know it’s running OpenWRT.
>> Any thoughts?
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