Re: [BUG] Default search path used in require_resolvable_fromhost

On Mon, 26 Jul 2010, Charlie Brady wrote:

> On Sun, 25 Jul 2010, Robert Spier wrote:
> 
> > I've committed this as ab7c2601f0740fac1c3c117e7e5c0a5690348194.
> > 
> > I'm not 100% sure it's a good idea, but I think it's mostly a good
> > thing.
> 
> What are your reservations?
> 
> I don't think it would ever be acceptable for the fromhost to be 
> resolvable only when the server's default domain is appended as suffix. 
> And as reported, the current code is exploitable, and Jesper claimed to 
> see it being exploited (but I am skeptical - is a spambot really injecting 
> mail to [email protected] direct to his server?).

There are multiple other uses of Net::DNS::Resolver, and some thought 
should be given to where some or all should also use dnsrch => 0 in the 
constructor.

[charlieb@localhost qpsmtpd-0.83]$ grep -r Net::DNS::Resolver .
./qpsmtpd-async:        $Net::DNS::Resolver::global{id} = 1;
./qpsmtpd-async:        $Net::DNS::Resolver::global{id} = int(rand(Net::DNS::Resolver::MAX_ID()));
./qpsmtpd-async:        # print "Next DNS ID: $Net::DNS::Resolver::global{id}\n";
./lib/Qpsmtpd/TcpServer.pm:  my $res = new Net::DNS::Resolver;
./plugins/require_resolvable_fromhost:  my $res = new Net::DNS::Resolver;
./plugins/require_resolvable_fromhost:  my $res   = new Net::DNS::Resolver;
./plugins/uribl:use Net::DNS::Resolver;
./plugins/uribl:    $self->{resolver} = new Net::DNS::Resolver or return undef;
./plugins/dns_whitelist_soft:  my $res = new Net::DNS::Resolver;
./plugins/dns_whitelist_soft:  my $res = new Net::DNS::Resolver;
./plugins/dnsbl:  my $res = new Net::DNS::Resolver;
./plugins/dnsbl:  my $res = new Net::DNS::Resolver;
./plugins/rhsbl:  my $res = new Net::DNS::Resolver;
./plugins/rhsbl:  my $res = new Net::DNS::Resolver;
[charlieb@localhost qpsmtpd-0.83]$ 



> 
> > Charlie - It would be great if you could send patches instead of
> > "suggestions".
> 
> It wasn't my suggestion - I was just relaying it. But point taken.
> 
> > -R
> > 
> > 
> > Charlie Brady wrote:
> > > 
> > > 
> > > http://bugs.contribs.org/show_bug.cgi?id=5808
> > > 
> > >  Jesper Knudsen      2010-03-01 01:29:10 MST 
> > > 
> > > When using the require_resolvable_fromhost plugin for qpsmtpd I noticed 
> > > that mails from [email protected] was actually getting through 
> > > this filter. I finally found out that the plugin has a bug that causes it 
> > > to insert default search path if it cannot find the domain. This means in 
> > > my case that localhost.localdomain was then tried resolved as 
> > > localhost.localdomain.swerts-knudsen.dk and since I have a wilcard CNAME 
> > > was resolved as my public IP.
> > > 
> > > Since this plugin is only enabled for public interface the fix is to set 
> > > the "dnsrch" flag when creating the Net::DNS object.
> > > 
> > > In require_resolvable_fromhost:
> > > my $res = Net::DNS::Resolver->new (
> > >                                    dnsrch => 0
> > >                                    );
> > 
>