There is a new CERT vulnerability that can leave you vulnerable to a Man-in-the-Middle attack. You can mitigate this vulnerability today by adding these two lines to your /etc/hosts file:
example.com is a stand in for your local domain. So replace example.com with whatever your local domain is.
The essence of this vulnerability is that an attacker can add a device to the network named wpad and get a DHCP lease, thus inserting the name wpad.example.com in the local DNS pointing to the attacker's machine. The presence of that A record allows control of the proxy settings of any browser in the network.
You can learn more about the technology behind this attack at Google's Project Zero page--it's an older article, but gives some insight into the inner workings of the attack.
The next release of dnsmasq includes an option (dhcp-ignore-names) that can be used to mitigate the attack at the source, but we haven't heard how Simon will act on this new vulnerability.
Since FTLDNS is just our fork of dnsmasq, we can easily merge in any upstream changes from him, but we wanted to let you know of the /etc/hosts fix that you can immediately implement.
@jacob.salmela
A long time ago, I responded to a topic, regarding excessive wpad queries and provided a solution to have lighttpd respond.
Does this imply that the solution is no longer a good solution?
I'm aware the solution doesn't have an entry for IPv6, but this can be easily fixed, NOT sure if lighttpd will also provide the response...
edit
The solution was further discussed in this topic, section Q/A (Q: Why so many local requests?) /edit
edit2
checked to see if IPv6 requests are responded to by lighttpd -> YES
IPv4 request (http://192.168.xxx.xxx/wpad.dat), entry in the lighttpd log
You're right, thanks msatter. Thought it needs to have a * to match wpad.custom_tld (ie wpad.box) but it will Interpret ^wpad as the beginning of a domain string anyway matching wpad and wpad.box .
Using ^wpad* would also match wpadddd which is overkill.
Anyway is there any drawback in using the blacklist instead of the hosts?
This is weird, I demonstrated this exploit back in the early naughties .
You also want to aim for registering wpad.[tld], if a Windows machine can't find wpad in it's local domain name, it will go up till it does, example: wpad.yourdomain.co.uk
when wpad does not exist, windows tries: wpad.co.uk
if that exists, bingo machine hyjacked.
in the blacklist of pihole now for some days with a good experience. It will block every request, that is of the character wpad.* (where * is any domain like yourdomain.co.uk or co.uk). I prefer this variant over the hosts file because it is part of the pihole mechanism and I get statistics as usual.
I guess this is the reason why I always disable any Proxy related settings in all my browsers and also check if any unneeded Services are running via services.msc
Both is possible and it doesn't really matter regarding security.
But I still prefer the blacklist method. Using this one can see which device is quering wpad in the statistics of Pi-hole. Having this information you can reach out to the vulnerable device and deactivate the "auto proxy" setting directly.
If you are tempted to create a "fix" for this wpad thingy...
Please make sure it is configuarable as I use wpad.
If pihole starts blocking this as security feature, there will be issues with users like me.
Many use the wpad dns entry to let clients know where to find wpad.dat or proxy.pac.
DNS wpad entry is picked up by clients, as clients send wpad question to dchp when getting ip stuff.
wpad entry in DNS is based on IP or hostname. And the wpad must be served from a webserver on port 80.
A solution could be adding a wpad thingly in the gui. For users without wpad, just enter 0.0.0.0
For me: I would use 192.168.1.4 or fqdn name.
DNSmasq can also be used to NOT serve a DHCP IP to a hostname:
Perhaps this works? Have not tested it:
dhcp-host=id:wpad,ignore