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Show HN: Use DNS TXT to share information

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Re: Show HN: Use DNS TXT to share information

#31
Timely. I've been noticing on flights that the in-flight wifi uses a squid proxy to block you until you pay - but most of the time, you'll get whatever data from the DNS Forwarder even if you haven't paid yet.

I've been noodling on how to build a simple proxy off DNS to test on my next flight.

Re: Show HN: Use DNS TXT to share information

#32
post #31

Timely. I've been noticing on flights that the in-flight wifi uses a squid proxy to block you until you pay - but most of the time, you'll get whatever data from the DNS Forwarder even if you haven't paid yet. I've been noodling on how to build a simple proxy off DNS to test on my next flight.

Search for iodine

Re: Show HN: Use DNS TXT to share information

#34
post #31

Timely. I've been noticing on flights that the in-flight wifi uses a squid proxy to block you until you pay - but most of the time, you'll get whatever data from the DNS Forwarder even if you haven't paid yet. I've been noodling on how to build a simple proxy off DNS to test on my next flight.

You might be interested in iodine.

https://github.com/yarrick/iodine

Re: Show HN: Use DNS TXT to share information

#35
post #27

It's always amusing when someone discovers DNS TXT records. ClamAV has been using them to announce the latest versions for more years than I care to remember. $ dig +short -t txt current.cvd.clamav.net "0.103.8:62:26972:1689593340:1:90:49192:334" For anyone interested, Freshclam interprets this as: Latest ClamAV version: 0.103.8 Latest Main DB version: 62 Latest Daily DB version: 26972 UNIX Timestamp 1689593340 ...an…

That is... interesting that they do not even use HTTPS or any type of signature for that info. So a man in the middle could prevent updates from happening, and freshclam wouldn't even throw a warning?

Won't DNSSEC prevent MITM attacks in this case?

From https://en.wikipedia.org/wiki/Domain_Name_System_Security_Ex... - "DNSSEC can protect any data published in the DNS, including text records (TXT) and mail exchange records (MX)"

Re: Show HN: Use DNS TXT to share information

#36
It was pretty common for orgs to use TXT and HINFO (“host info”) records up through the 1990s.

I still use them at work to provide hints and more information but the current fleet of IT workers don’t really grok anything beyond A and PTR.

You’re just using DNS as intended. :-P

Re: Show HN: Use DNS TXT to share information

#37
post #27

Earlier quoted context omitted.

That is... interesting that they do not even use HTTPS or any type of signature for that info. So a man in the middle could prevent updates from happening, and freshclam wouldn't even throw a warning?

Won't DNSSEC prevent MITM attacks in this case? From https://en.wikipedia.org/wiki/Domain_Name_System_Security_Ex... - "DNSSEC can protect any data published in the DNS, including text records (TXT) and mail exchange records (MX)"

clamav.net, like most domains, doesn't enable DNSSEC. Further, as designed, local resolvers don't validate DNSSEC, they just ask the recursive resolver to; a MITM between the local and the recursive can lie.

So when wikipedia says DNSSEC can protect, that's the permissive can. Like things can happen. But don't rely on it.

Re: Show HN: Use DNS TXT to share information

#38
post #27

Earlier quoted context omitted.

That is... interesting that they do not even use HTTPS or any type of signature for that info. So a man in the middle could prevent updates from happening, and freshclam wouldn't even throw a warning?

Won't DNSSEC prevent MITM attacks in this case? From https://en.wikipedia.org/wiki/Domain_Name_System_Security_Ex... - "DNSSEC can protect any data published in the DNS, including text records (TXT) and mail exchange records (MX)"

[deleted]

Re: Show HN: Use DNS TXT to share information

#39

Earlier quoted context omitted.

This is pretty good for bypassing captive portals on public Wi-Fi access points. Sometimes you can use it to get Internet for free without paying. These days most are more clever and will block everything other than the default gateway until you sign on.

Don't most of them hijack any DNS traffic to send it to their own portal?

That's not that typical anymore. For one thing, it poisons the client's dns cache, and it can be hard to go to the actual destination later. For another, if DNS was the access control mechanism, that's pretty weak, many people can figure out how to get around a DNS block.

It's more typical now to return the A records, and then route all IPs to a portal server until you login. Logged in sessions get to go forth to the internet.

Re: Show HN: Use DNS TXT to share information

#40
post #37

Earlier quoted context omitted.

Won't DNSSEC prevent MITM attacks in this case? From https://en.wikipedia.org/wiki/Domain_Name_System_Security_Ex... - "DNSSEC can protect any data published in the DNS, including text records (TXT) and mail exchange records (MX)"

clamav.net, like most domains, doesn't enable DNSSEC. Further, as designed, local resolvers don't validate DNSSEC, they just ask the recursive resolver to; a MITM between the local and the recursive can lie. So when wikipedia says DNSSEC can protect, that's the permissive can. Like things can happen. But don't rely on it.

No, stub resolvers are supposed to, and often do validate DNSSEC signatures. DNSSEC is designed so that validation should happen whenever any DNS data is received over the network.
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