6 ms·

Fuzzing DNS Zone Parsers

57 points by fcambus 7y ago

ifoundthetao 7y ago
Excellent! Would you be willing to do a second article on the process you used when wading through the findings?
tptacek 7y ago
This is a little disturbing; nsd is kind of a big deal, and afl on zone files is a pretty basic test to run. Kudos to the author for doing it, but why haven't the authors of nsd done it already, and what else haven't they done? There is really no good reason for DNS servers to be written in C anymore.
- bluejekyll 7y ago
  > There is really no good reason for DNS servers to be written in C anymore. I’m a little behind on docs, but we have a pretty decent start on one in Rust: https://github.com/bluejekyll/trust-dns https://github.com/bluejekyll/trust-dns We still need an AXFR, IXFR, or replication solution. Also, I haven’t had time to fuzz the zone parsers, so I can’t guarantee we’re resilient to the above yet, but the packet parsers are getting pretty widely used across multiple Rust projects now through the trust-dns-resolver library.
  - tptacek 7y ago
    What's wrong with rsync?
    - bluejekyll 7y ago
      Nothing. Depends on the mode of operation we want to support. I want to support that, but we need to add some signal handling (or similar mechanism) to properly reload configs after an raunchy is done. Right now a restart would be required.
- techntoke 7y ago
  Simply not true and a matter of opinion.
nly 7y ago
Nobody knows how to parse zone files. I fuzzed a few zone file parsers several years ago, but to find the differences between implementations rather than crashes. The problem is the format is really poorly specified, has been refined over about 10 RFCs, and still riddled with ambiguities. Every implementation out there handles things slightly differently. I'll just dump some notes I wrote at the time, containing a list of RFCs and some findings, to gist: https://gist.github.com/nlyan/2a958fa476182e1b07955a945f0d7052 https://gist.github.com/nlyan/2a958fa476182e1b07955a945f0d70...
- wipseabusbus 7y ago
  Off topic: Hello from the person who forked synergy a couple of years ago :)

57 points by fcambus 7y ago

Excellent! Would you be willing to do a second article on the process you used when wading through the findings?

This is a little disturbing; nsd is kind of a big deal, and afl on zone files is a pretty basic test to run. Kudos to the author for doing it, but why haven't the authors of nsd done it already, and what else haven't they done? There is really no good reason for DNS servers to be written in C anymore.

bluejekyll 7y ago
> There is really no good reason for DNS servers to be written in C anymore. I’m a little behind on docs, but we have a pretty decent start on one in Rust: https://github.com/bluejekyll/trust-dns https://github.com/bluejekyll/trust-dns We still need an AXFR, IXFR, or replication solution. Also, I haven’t had time to fuzz the zone parsers, so I can’t guarantee we’re resilient to the above yet, but the packet parsers are getting pretty widely used across multiple Rust projects now through the trust-dns-resolver library.
- tptacek 7y ago
  What's wrong with rsync?
  - bluejekyll 7y ago
    Nothing. Depends on the mode of operation we want to support. I want to support that, but we need to add some signal handling (or similar mechanism) to properly reload configs after an raunchy is done. Right now a restart would be required.
techntoke 7y ago
Simply not true and a matter of opinion.

nly 7y ago

Nobody knows how to parse zone files. I fuzzed a few zone file parsers several years ago, but to find the differences between implementations rather than crashes. The problem is the format is really poorly specified, has been refined over about 10 RFCs, and still riddled with ambiguities. Every implementation out there handles things slightly differently. I'll just dump some notes I wrote at the time, containing a list of RFCs and some findings, to gist: https://gist.github.com/nlyan/2a958fa476182e1b07955a945f0d7052 https://gist.github.com/nlyan/2a958fa476182e1b07955a945f0d70...

wipseabusbus 7y ago
Off topic: Hello from the person who forked synergy a couple of years ago :)