Non-Bug: Deadwood **DOES NOT** crash when given a CNAME label with a NULL in it

[samboy]

I got a private security report, very detailed, claiming Deadwood crashes when given a CNAME label with a NULL in it.

Nope. Yes, I am sure Deadwood has security bugs. There may even be “packet of death” security bugs. But this isn’t one of them.

I have created a test bed, where we send Deadwood a CNAME label with a NULL in it.

Deadwood does not crash.

Here is the testbed: https://github.com/samboy/MaraDNS/tree/master/deadwood-github/sqa/sqa_null_in_cname

This supposed security bug report claims, that when I run do.test in that directory, that Deadwood will crash.

Let me verify there isn't an issue. In Ubuntu 24.04, I ran the following commands in the Linux (UNIX!) shell:

git clone https://github.com/samboy/MaraDNS
cd MaraDNS
git checkout 27f0586fc47b51efeb4c710e62afd50d4ad518cd
./configure
make
sudo cp coLunacyDNS/lunacy/lunacy /usr/local/bin/
sudo cp tools/askmara /usr/local/bin/
cd deadwood-github/sqa/sqa_null_in_cname/
sudo ./do.test

(I’m adding stuff to /usr/local/bin because Deadwood needs my fork of Lua 5.1 and askmara for some of the tests in one’s path)

This is what I see:

Deadwood version git-27f0586fc4
Deadwood: A DNS UDP non-recursive cache (IPv6 supported)
We bound to 1 addresses
# Querying the server with the IP 127.0.1.10
HERE0 (nil)
HERE0 (nil)
HERE0 (nil)
HERE0 (nil)
HERE0 (nil)
HERE0 (nil)
# Remote server said: SERVER FAILURE
# Question: Aname.foo.example.com.
# NS replies:
# AR replies:
# Querying the server with the IP 127.0.1.10
# Question: Aname.example.com.
name.example.com. +86400 a 127.99.99.99
# NS replies:
# AR replies:

Got signal 1 to process...

Point being:

• We hit that code around line 2272 in DwRecurse.c
• I added a Debug message showing Deadwood processing and not crashing in 27f0586
• I ran a test where Deadwood gets a CNAME with a NULL in it
• DEADWOOD DOES NOT CRASH
• Deadwood is able to process other queries

So I closed the security report: Works for me.