Fixes an infinite recursion error where Metasploit would attempt to
resolve a nameserver specified as a hostname in /etc/resolv.conf while
initializing.
Values for the namserver key in the resolv.conf file must be IP
addresses per the man page while the Resolver class in theory allows
them to be added by hostname however an existing one must be defined by
which it will be resolved.
This notably prevents IPv6 addresses with a scope ID from being allowed
in Ruby versions < 3.1.
This solves the looping problem. Since the TCP connection wouldn't
necessarily close, we couldn't count on a 0-length recv, and the
connection was timing out. Changed it so send_tcp can take a block, in
which we do parsing. AXFR responses are sandwiched between SOA answers,
so when the second one is reached, the transfer is done.
This is also cleaner for existing code that uses send_tcp, since if no
block is passed, it just returns the first response and tears down the
connection, just like it used to.
This required some changes to send_tcp: it now loops, reading as many
length-prefixed DNS responses as are available before the connection
closes. This shouldn't affect other uses of the function, since most
questions only have one response in answer.
AXFR support in net-dns is broken. This fixes it, and makes the
requisite modifications to enum_dns module. Basic problem is that AXFR
responses consist of a chain of DNS replies, not a single reply with
multiple answers. Previously, only the first of these replies, the SOA
record, was returned. Also added some exception handling to avoid
problems like #483.
adfoster-r7