Feature Request: Cross-platform library to query the system resolver for arbitrary DNS records #317
Description
I would like to have a cross-platform package to query the system DNS resolver and get DNS messages. This will enable:
- Fetching of the HTTPS (and SVCB) records to jump straight to TLS/H2/H3, bypassing vulnerable protocols.
- Fetching of ECH keys.
- Better detection of DNS interference on the fly.
I have prototypes for macOS/iOS, Linux and Android that queries an arbitrary resource record using the system resolver. It's Go code using cgo.
Some observations:
- libresolv doesn't work on Android and iOS because you can't query localhost:53.
- libresolv is bad, since it's blocking and doesnt' allow for cancellation.
- On Android you can call android_res_nquery from C/C++
- Apple was a pain to figure out due to lack of documentation. I found their source code to be helpful and I have pointers in my code. This repo has example clients as well.
- I haven't tried Windows yet, but I was going to try the DnsQueryEx api (example).