Dns

Someone recently reached out to me discussing DNS and as that person started taking deep dive in DNS, he came across the glue records. He asked me “Why not just use A records on a sub-zone with glue record at the parent zone”?

This was a fantastic question. I am going to document it in this post on why not. First and foremost let’s have a clear understanding of glue records.

Has been a while since I checked the status of root servers which are hosted at NIXI. The list as per their official member list stays the same i.e i root in Mumbai, K root in Noida and F root in Chennai. 

i root seems to be up!

show ip bgp neighbors 218.100.48.75 received-routes
       There are 5 received routes from neighbor 218.100.48.75
Searching for matching routes, use ^C to quit...
Status A:AGGREGATE B:BEST b:NOT-INSTALLED-BEST C:CONFED_EBGP D:DAMPED
       E:EBGP H:HISTORY I:IBGP L:LOCAL M:MULTIPATH m:NOT-INSTALLED-MULTIPATH
       S:SUPPRESSED F:FILTERED s:STALE
       Prefix             Next Hop        MED        LocPrf     Weight Status
1      192.36.148.0/24    218.100.48.75   0          100        0      BE
         AS_PATH: 8674 29216
2      194.58.198.0/24    218.100.48.75   0          100        0      BE
         AS_PATH: 8674 56908
3      194.58.199.0/24    218.100.48.75   0          100        0      BE
         AS_PATH: 8674 56908
4      194.146.106.0/24   218.100.48.75   0          100        0      BE
         AS_PATH: 8674
5      194.146.107.0/24   218.100.48.75   0          100        0      BE
         AS_PATH: 8674

A few days some folks in internet community noticed Cloudflare AS13335 announcing F root server’s routes covering prefix 192.5.5.0/24.  

dig version.bind ch txt @f.root-servers.net pic.twitter.com/YLW7hqt170

— Tony Finch (@fanf) April 3, 2017

Above tweet shows that case is clearly not a mistake but rather some sort of arrangement between Cloudflare and ISC (which is responsible for F-root). There was another discussion on DNS-OARC mailing list here. From our bgp.he.net tool, one can analyse route propagation for F root’s AS3557.

Yesterday Google’s Bangladeshi website google.com.bd was hacked and this happened via DNS. It was reported on the bdNOG mailing list at morning in a thread started by Mr Omar Ali.

This clearly shows how authoritative DNS for “com.bd.” (which is same as bd. btw) was poisoned and was reflecting attackers authoritative DNS. Later Mr Farhad Ahmed posted a screenshot of google.com.bd showing hackers page:

Later Mr Sumon Ahmed mentioned that it happened because web frontend of .bd was compromised. This was an interesting hijack as attacker attacked the key infrastructure of the registry instead of Google or Facebook servers. It’s also a warm reminder of the way DNS depends on the hierarchal structure by design and at this stage, we need to focus on DNSSEC to add on the security to the current system.   Lately .bd domain faced issues multiple time this year. I hope it will have a good stable time in the upcoming year. In terms of stability it is being backed by PCH anycast infrastructure but PCH’s DNS servers are just published in NS records of it’s existing auth servers, but not on the parent zone (which is root zone). Thus the point of failure remains and is yet to be fixed.

Talking about root DNS server’s anycast at APNIC42. YouTube here.