n/dns.md: note ECS size (/24 or /56 and what those mean), some emphasis

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Aminda Suomalainen 2024-05-03 18:14:58 +03:00
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@ -64,6 +64,13 @@ brings up two bigger issues EDNS client-subnet:
queries. queries.
- Think of VPNs where traffic within the VPN is encrypted, but it won't - Think of VPNs where traffic within the VPN is encrypted, but it won't
magically encrypt plain traffic leaving it. magically encrypt plain traffic leaving it.
- The part given to the au4thoritative nameserver is `/24` on IPv4 and
`/56` on IPv6. These equal 192.0.2.x so if a MITM wanted to know who you
are there would be 254 options (assuming there are no NATs). On IPv6 a
`/56` includes 256 `/64` blocks and `/64` is the most used block and there
is a recommendation of giving customers a `/56` block, so it would point
directly to your connection. However some mobile operators give a `/64`
so it will again point to 256 options again. Not that many.
- Anyone between the recursive and authoritative nameservers can perform cache - Anyone between the recursive and authoritative nameservers can perform cache
poisoning attack and give it a narrow target. With short TTL, it may be poisoning attack and give it a narrow target. With short TTL, it may be
impossible to audit afterwards. Only DNSSEC can protect from this, but impossible to audit afterwards. Only DNSSEC can protect from this, but
@ -81,8 +88,8 @@ These issues bring additional questions:
for gayming. Virtual machine lab? Who cares. Larger organization? That may for gayming. Virtual machine lab? Who cares. Larger organization? That may
be a big target? be a big target?
- How much does getting local content matter to you? More or less than - How much does getting local content matter to you? More or less than
increased resource use of contacting a server further away? Is private ECS increased resource use of contacting a server further away? _Is private ECS
an option? ([r/resolv.tsv](/r/resolv.tsv)) an option?_ ([r/resolv.tsv](/r/resolv.tsv))
- What is the impact of domains you visit being surveilled? - What is the impact of domains you visit being surveilled?
- This page mentions cases like FFUpdater where the surveillance would - This page mentions cases like FFUpdater where the surveillance would
reveal that I interact with github.com and other sites it downloads apk reveal that I interact with github.com and other sites it downloads apk