This PR enables DNS 0x20 as per
https://datatracker.ietf.org/doc/html/draft-vixie-dnsext-dns0x20-00 .
DNS 0x20 adds additional entropy to the request by randomly altering the
case of the DNS question to help prevent cache poisoning attacks.
Google DNS has implemented this support as of 2023, even though this is
a proposed and expired standard from 2008:
https://groups.google.com/g/public-dns-discuss/c/KxIDPOydA5M
There have been documented cases of name server and caching server
non-conformance, though it is expected to become more rare, especially
since Google has started using this.
This can be enabled via the `ARES_FLAG_DNS0x20` flag, which is currently
disabled by default. The test cases do however enable this flag to
validate this feature.
Implementors using this flag will notice that responses will retain the
mixed case, but since DNS names are case-insensitive, any proper
implementation should not be impacted.
There is currently no fallback mechanism implemented as it isn't
immediately clear how this may affect a stub resolver like c-ares where
we aren't querying the authoritative name server, but instead an
intermediate recursive resolver where some domains may return invalid
results while others return valid results, all while querying the same
nameserver. Likely using DNS cookies as suggested by #620 is a better
mechanism to fight cache poisoning attacks for stub resolvers.
TCP queries do not use this feature even if the `ARES_FLAG_DNS0x20` flag
is specified since they are not subject to cache poisoning attacks.
Fixes Issue: #795
Fix By: Brad House (@bradh352)
c-ares uses multiple code styles, standardize on one. Talking with @bagder he feels strongly about maintaining an 80 column limit, but feels less strongly about things I feel strongly about (like alignment).
Can re-run the formatter on the codebase via:
```
clang-format -i */*.c */*.h */*/*.c */*/*.h
```
Fix By: Brad House (@bradh352)
All files have their licence and copyright information clearly
identifiable. If not in the file header, they are set separately in
.reuse/dep5.
All used license texts are provided in LICENSES/
There is too much inconsistency between platforms for arpa/nameser.h and arpa/nameser_compat.h for the way the current files are structured. Still load the respective system files but make our private nameser.h more forgiving.
Fixes: #388
Fix By: Brad House (@bradh352)
The rc4 function iterates over a buffer of size buffer_len who's maximum
value is INT_MAX with a counter of type short that is not guaranteed to
have maximum size INT_MAX.
In circumstances where short is narrower than int and where buffer_len
is larger than the maximum value of a short, it may be possible to loop
infinitely as counter will overflow and never be greater than or equal
to buffer_len.
The solution is to make the comparison be between types of equal width.
This commit defines counter as an int.
Fix By: Fionn Fitzmaurice (@fionn)
Brad House
Daniel Stenberg
Martin Holeš
Fionn Fitzmaurice