ELI5: Does a DNS provider or an adversary know my real IP address if I have a DNS leak? (discuss.tchncs.de)

submitted 2 weeks ago by chemicalwonka@discuss.tchncs.de to c/explainlikeimfive@lemmy.world

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I use a VPN service that is connected to a server in another country, however this VPN service does not offer control over my DNS requests to block some sites so I preferred to use another DNS resolver that has this function.

My question is: When I access my VPN's website, it accuses that a "DNS leak" is occurring. Can the DNS provider know my real IP address, or does it only know my VPN's IP?

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[-] lurch@sh.itjust.works 5 points 2 weeks ago

the other DNS resolver can see your IP and the sites you look up if the route to it is not set to go through the VPN. you can maybe use something like traceroute to check that, but it should be possible to conclude it from the routing table.

[-] MummifiedClient5000@feddit.dk 3 points 2 weeks ago

Traceroute won't show if you leak DNS requests outside of your VPN. (Unless you coincidentally also leak traffic, but then you're pretty much just not using your VPN).

To confirm you'll need to analyze your traffic-flow using a tool like tcpdump or Wireshark and check the source and destination for DNS traffic. If you see incoming DNS responses on an interface that is not your VPN-adaptor or maybe a loopback interface then you're probably not tunnelling DNS through the VPN.

To answer the question in the headline: Regular DNS is unencrypted and quite easy to snoop on, so any node on the route between you and the DNS server will be able to read it if not using a VPN (i.e. DNS leak). Not sure what you mean by adversary, but it's not like anyone on the internet can see your traffic. The DNS server may log your request and if you're not on VPN, your IP address may be logged too.

[-] lurch@sh.itjust.works 2 points 2 weeks ago

no, you traceroute the DNS IP. that's what i meant. if it doesn't hop through the VPN in the beginning it doesn't work. but you have to capture network traffic, if the VPN server doesn't respond to trace packages and you want proof beyond the routing table

[-] MummifiedClient5000@feddit.dk 2 points 2 weeks ago

By doing a traceroute to the DNS IPs, you only confirm that traceroute goes through the VPN interface, not your DNS resolution.

[-] lurch@sh.itjust.works 1 points 2 weeks ago

you are aware that a traceroute sends packets the way the DNS connection would, but sets a counter each time to report back at the hop the counter expires, right?

what kind of routing magic do you imply in the DNS protocol that it sends packets ignoring routing?