[OpenWrt-Devel] OpenWRT www version banner a security risk

[Etienne Champetier]

Hi Daniel,

Le 13 sept. 2015 22:04, "Daniel Dickinson" <openwrt at daniel.thecshore.com> a
écrit :
>
> I do think allowing to choose to disable the banner is a minor benefit,
however, as I've said, there are much more effective means of preventing
accidential exposure, and quite frankly if the user is *choosing* to open
the web interface I think an warning and disabling the banner if the user
foolishly insists on opening the interface despite the warning is more
useful thank disabling the banner by default.
>
> If you're going to argue it prevents against internal threats than I
would argue that if your internal network is hostile enough that you need
to worry about attacks on openwrt from your internal network AND you're not
skilled enough to limit access to LuCI (or better, build an image without
LuCI and just use SSH) to the specific trusted hosts (preferably by
combination of MAC address and IP address) in the firewall, or (better) to
use a 'management' VPN or VLAN that only trusted hosts can get on, then
you're in a lot more trouble than eliminating the banner for LuCI will
solve.
>
>
> Regards,
>
> Daniel
>
> 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?
>>
>> Maurits
>>

For me listenning only on lan will break all my setups (15+):
- On most of my openwrt there is no lan, it's management, or
'name-of-the-site' ...
- on some of them i can access from multiple interface (VPNs + ...)

You can't prevent people from shooting themselves in the foot (maybe port
openning was on purpose),
but you can:
-Put a huge warning in luci when you set firewall default to 'ACCEPT'
-add robots.txt (i think the router will still end up on shodan)
-add a big warning if robots.txt is accessed (reliable way to know that
you're open on the internet)

Also you are talking about luci but what about dropbear (ssh)? There is no
anti brute force, and maybe there is a banner (on my phone, can't check)

Please don't break my setups :)
Etienne
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