#!/usr/bin/perl
#
# dnswalk    Walk through a DNS tree, pulling out zone data and
# dumping it in a directory tree
#
# $Id: dnswalk,v 1.18 1997/10/06 13:23:58 barr Exp barr $
#
# check data collected for legality using standard resolver
#
# invoke as dnswalk domain > logfile
# Options:
#    -r    Recursively descend subdomains of domain
#    -i    Suppress check for invalid characters in a domain name.
#    -a    turn on warning of duplicate A records.
#    -d    Debugging
#    -m    Check only if the domain has been modified.  (Useful only if
#          dnswalk has been run previously.)
#    -F    Enable "facist" checking.  (See man page)
#    -l    Check lame delegations

use Getopt::Std;
use IO::Socket;
use Net::DNS;

getopts("D:rfiadmFl");

$num_error{'FAIL'}=0;		# failures to access data
$num_error{'WARN'}=0;		# questionable data
$num_error{'BAD'}=0;		# bad data

# Where all zone transfer information is saved.  You can change this to
# something like /tmp/dnswalk if you don't want to clutter up the current
# directory
if ($opt_D) {
    $basedir = $opt_D;
} else {
    $basedir = ".";
}
($domain = $ARGV[0]) =~ tr/A-Z/a-z/;
if ($domain !~ /\.$/) {
    die "Usage: dnswalk domain\ndomain MUST end with a '.'\n";
}
if (! -d $basedir) {
	mkdir($basedir,0777) || die "FAIL: Cannot create $basedir: $!\n";
}

&dowalk($domain);
print STDERR "$num_error{'FAIL'} failures, $num_error{'WARN'} warnings, $num_error{'BAD'} errors.\n";
exit $num_error{'BAD'};

sub dowalk {
    my (@subdoms);
    my (@sortdoms);
    my ($domain)=$_[0];
    $modified=0;
    return unless $domain;
    print "Checking $domain\n";
    @subdoms=&doaxfr($domain);
    &check_zone($domain) if (defined(@zone) && @zone);
    undef @zone;
    return if (!(defined(@subdoms) && @subdoms));
    @sortdoms = sort byhostname @subdoms;
    local ($subdom);
    if ($opt_r) {
        foreach $subdom (@sortdoms) {
            &dowalk($subdom);
        }
    }
}
# try to get a zone transfer, trying each listed authoritative server if
# if fails.
sub doaxfr {
    local ($domain)=@_[0];
    local (%subdoms)=();
    local ($subdom);
    local(@servers) = &getauthservers($domain);
    &printerr("BAD", "$domain has only one authoritative nameserver\n") 
	if (scalar(@servers) == 1);
    &printerr("BAD", "$domain has NO authoritative nameservers!\n")
	if (scalar(@servers) == 0);
    SERVER:
    foreach $server (@servers) {
        print STDERR "Getting zone transfer of $domain from $server...";
	my $res = new Net::DNS::Resolver;
	$res->nameservers($server);
	@zone=$res->axfr($domain);
	unless (defined(@zone) && @zone) {
	    print STDERR "failed\n";
		&printerr("FAIL",
			"Zone transfer of $domain from $server failed: ".
			$res->errorstring. "\n");
		next SERVER;
	}
	@subdoms=undef;
        foreach $rr (@zone) {
            if ($rr->type eq "NS") {
		$subdom = $rr->name;
                $subdom =~ tr/A-Z/a-z/;
                if ((!&equal($subdom,$domain)) && ( !$subdoms{$subdom})) {
                    $subdoms{$subdom}=1;
                }
            }
        }
        print STDERR "done.\n";
        last SERVER;
    } # foreach #
    unless (defined(@zone) && @zone) {
	    &printerr("BAD","All zone transfer attempts of $domain failed!\n");
	    return undef;
    }
    return (keys %subdoms);
}

sub getauthservers {
    my ($domain)=$_[0];
    my ($master)=&getmaster($domain);
    my ($foundmaster)=0;
    my ($ns);
    my ($ns_tmp);
    my ($res);
    my ($ns_req);
    my (@servers);
    my (%servhash);
    return if (!$master);  # this is null if there is no SOA or not found
    return if (!$domain);
    $res = new Net::DNS::Resolver;
    $ns_req = $res->query($domain, "NS");
    &printerr("FAIL", "No nameservers found for $domain: ". 
	$res->errorstring ."\n") 
	    unless (defined($ns_req) and ($ns_req->header->ancount > 0));
    foreach $ns ($ns_req->answer) {
	$ns_tmp = $ns->nsdname;
	$ns_tmp =~ tr/A-Z/a-z/;
	if (&equal($ns_tmp,$master)) {
	    $foundmaster=1;   # make sure the master is at the top
	} else {
	    push(@servers,$ns_tmp) if ($servhash{$ns_tmp}++<1);
	}
    }
    if ($foundmaster) {
	unshift(@servers,$master);
    }
    return @servers;
}

# return 'master' server for zone
sub getmaster {
    my ($zone)=$_[0];
    my ($res) = new Net::DNS::Resolver;
    my ($packet) = new Net::DNS::Packet($zone, "SOA", "IN");
    my ($soa_req) = $res->send($packet);
    unless (defined($soa_req)) {
	&printerr("FAIL", "Cannot get SOA record for $zone:". 
	    $res->errorstring ."\n");
	return "";
    }
    unless (($soa_req->header->ancount >= 1) && 
	   (($soa_req->answer)[0]->type eq "SOA")) {
	&printerr("BAD", "SOA record not found for $zone\n");
	return "";
    }
    return ($soa_req->answer)[0]->mname;
}

# open result of zone tranfer and check lots of nasty things
# here's where the fun begins
sub check_zone {
    my ($domain)=$_[0];
    local (%glues)=();	# look for duplicate glue (A) records
    local ($name, $aliases, $addrtype, $length, @addrs);
    local ($prio,$mx);
    local ($soa,$contact);
    local ($lastns);	# last NS record we saw
    local (@keys);	# temp variable
    foreach $rr (@zone) {
	# complain about invalid chars only for mail names
        if ((($rr->type eq "A") || ($rr->type eq "MX")) && (!$opt_i) &&
	    ($rr->name =~ /[^\*][^-A-Za-z0-9.]/)) {
            &printerr("WARN", $rr->name .": invalid character(s) in name\n");
        }
        if ($rr->type eq "SOA") {
	    print STDERR 's' if $opt_d;
	    print "SOA=". $rr->mname ."	contact=". $rr->rname ."\n";
	    # basic address check.  No "@", and user.dom.ain (two or more dots)
	    if (($rr->rname =~ /@/)||!($rr->rname =~ /\..*\./)) {
		&printerr("WARN", "SOA contact name (". 
		    $rr->rname .") is invalid\n");
	    }
        } elsif ($rr->type eq "PTR") {
            print STDERR 'p' if $opt_d;
            if (scalar((@keys=split(/\./,$rr->name))) == 6 ) {
                # check if forward name exists, but only if reverse is
                # a full IP addr
                # skip ".0" networks
                if ($keys[0] ne "0") {
                   ($name, $aliases, $addrtype, $length,
			    @addrs)=gethostbyname($rr->ptrdname);
#                   if (!(($name, $aliases, $addrtype, $length,
#			    @addrs)=gethostbyname($rr->ptrdname))) {
#                        &printerr("FAIL", "gethostbyname(". 
#			    $rr->ptrdname ."): $!\n");
#                   }
#                   else {
                        if (!$name) {
                            &printerr("WARN", $rr->name
				." PTR ". $rr->ptrdname .": unknown host\n");
                        }
                        elsif (!&equal($name,$rr->ptrdname)) {
                            &printerr("WARN", $rr->name 
			      ." PTR ". $rr->ptrdname .": CNAME (to $name)\n");
                        }    
                        elsif (!&matchaddrlist($rr->name)) {
                            &printerr("WARN", $rr->name
			     ." PTR ". $rr->ptrdname .": A record not found\n");
                        }
#                   }
                }
            }
        } elsif (($rr->type eq "A") ) {
            print STDERR 'a' if $opt_d;
	    # check to see that a reverse PTR record exists
            ($name,$aliases,$addrtype,$length,@addrs)=gethostbyaddr(pack('C4',
		    split(/\./,$rr->address)),2);
	    if (!$name) {
		# hack - allow RFC 1101 netmasks encoding
		if ($rr->address !=~ /^255/) {
		    &printerr("WARN", $rr->name ." A ".
			$rr->address .": no PTR record\n");
		}
	    }
	    elsif ($opt_F && !&equal($name,$rr->name)) {
		# Filter out "hostname-something" (like "neptune-le0")
		if (index(split (/\./, $rr->name, 2) . "-", 
			    split (/\./, $name, 2)) == -1 ) {
			&printerr("WARN", $rr->name ." A ". 
			    $rr->address .": points to $name\n") 
			    if ((split(/\./,$name))[0] ne "localhost");
		}
	    }
	    if ($main'opt_a) {
		# keep list in %glues, report any duplicates
		if ($glues{$rr->address} eq "") {
		    $glues{$rr->address}=$rr->name;
		}
		elsif (($glues{$rr->address} eq $rr->name) &&
			(!&equal($lastns,$domain))) {
		    &printerr("WARN", $rr->name
			.": possible duplicate A record (glue of $lastns?)\n");
		}
	    }
        } elsif ($rr->type eq "NS") {
            $lastns=$rr->name;
            print STDERR 'n' if $opt_d;
            # check to see if object of NS is real
            &checklamer($rr->name,$rr->nsdname) if ($main'opt_l);
	    # check for bogusnesses like NS->IP addr
	    if (&isipv4addr($rr->nsdname)) {
		&printerr("BAD", $rr->name
			." NS ". $rr->nsdname .": Nameserver must be a hostname\n");
	    }
            ($name, $aliases, $addrtype, $length,
		    @addrs)=gethostbyname($rr->nsdname);
#            if (!(($name, $aliases, $addrtype, $length,
#		    @addrs)=gethostbyname($rr->nsdname))) {
#                &printerr("FAIL", "gethostbyname(". $rr->nsdname ."): $!\n");
#            }
#            else {
                if (!$name) {
                    &printerr("BAD", $rr->name
			." NS ". $rr->nsdname .": unknown host\n");
                } elsif (!&equal($name,$rr->nsdname)) {
                    &printerr("BAD", $rr->name
			." NS ". $rr->nsdname .": CNAME (to $name)\n");
                }
#            }
        } elsif ($rr->type eq "MX") {
            print STDERR 'm' if $opt_d;
            # check to see if object of mx is real
	    if (&isipv4addr($rr->exchange)) {
		&printerr("BAD", $rr->name
			." MX ". $rr->exchange .": Mail exchange must be a hostname\n");
	    }
            ($name, $aliases, $addrtype, $length,
		    @addrs)=gethostbyname($rr->exchange);
#            if (!(($name, $aliases, $addrtype, $length,
#		    @addrs)=gethostbyname($rr->exchange))) {
#                &printerr("FAIL", "gethostbyname(". $rr->exchange ."): $!\n");
#            }
#            else {
                if (!$name) {
                    &printerr("WARN", $rr->name
			." MX ". $rr->exchange .": unknown host\n");
                }
                elsif (!&equal($name,$rr->exchange)) {
                    &printerr("WARN", $rr->name
			." MX ". $rr->exchange .": CNAME (to $name)\n");
                }
#            }
        } elsif ($rr->type eq "CNAME") {
            print STDERR 'c' if $opt_d;
            ($name, $aliases, $addrtype, $length,
		    @addrs)=gethostbyname($rr->cname);
	    if (&isipv4addr($rr->cname)) {
		&printerr("BAD", $rr->name
			." CNAME ". $rr->cname .": alias must be a hostname\n");
	    }
#            if (!(($name, $aliases, $addrtype, $length,
#		    @addrs)=gethostbyname($rr->cname))) {
#                &printerr("FAIL", "gethostbyname(". $rr->cname ."): $!\n");
#            }
#            else {
                if (!$name) {
                    &printerr("WARN", $rr->name
			." CNAME ". $rr->cname .": unknown host\n");
                } elsif (!&equal($name,$rr->cname)) {
                    &printerr("WARN", $rr->name
			." CNAME ". $rr->cname .": CNAME (to $name)\n");
                }
#            }
        }
    }
    print STDERR "\n" if $opt_d;
    close(FILE);
}

# prints an error message, suppressing duplicates
sub printerr {
    my ($type, $err)=@_;
    if ($errlist{$err}==undef) {
	print "$type: $err";
	$num_error{$type}++;
	print STDERR "!" if $opt_d;
	$errlist{$err}=1;
    } else {
	print STDERR "." if $opt_d;
    }
}

sub equal {
    # Do case-insensitive string comparisons
    local ($one)= $_[0];
    local ($two)= $_[1];
    $stripone=$one;
    if (chop($stripone) eq '.') {
	$one=$stripone;
    }
    $striptwo=$two;
    if (chop($striptwo) eq '.') {
	$two=$striptwo;
    }
    $one =~ tr/A-Z/a-z/;
    $two =~ tr/A-Z/a-z/;
    return ($one eq $two);
}

# check if argument looks like an IPv4 address
sub isipv4addr {
    my ($host)=$_[0];
    my ($one,$two,$three,$four);
    ($one,$two,$three,$four)=split(/\./,$host);
    my $whole="$one$two$three$four";
    # strings evaluated as numbers are zero
    return (($whole+0) eq $whole);
}
sub matchaddrlist {
    local($match)=pack('C4', reverse(split(/\./,$_[0],4)));
    local($found)=0;
    foreach $i (@addrs) {
        $found=1 if ($i eq $match);
    }
    return $found;
}

# there's a better way to do this, it just hasn't evolved from
# my brain to this program yet.
sub byhostname {
    @c = reverse(split(/\./,$a));
    @d = reverse(split(/\./,$b));
    for ($i=0;$i<=(($#c > $#d) ? $#c : $#d) ;$i++) {
        next if $c[$i] eq $d[$i];
        return -1 if $c[$i] eq "";
        return  1 if $d[$i] eq "";
        if ($c[$i] eq int($c[$i])) {
            # numeric
            return $c[$i] <=> $d[$i];
        }
        else {
            # string
            return $c[$i] cmp $d[$i];
        }
    }
    return 0;
}

sub checklamer {
    my ($zone,$nameserver)=@_;
    my ($packet) = new Net::DNS::Packet($zone, "SOA", "IN");
    my ($soa_req);
    my ($res) = new Net::DNS::Resolver;
    unless ($res->nameservers($nameserver)) {
	&printerr("FAIL", "Cannot find address for nameserver: ".
	    $res->errorstring. "\n");
    }
    $soa_req = $res->send($packet);
    unless (defined($soa_req)) {
	&printerr("FAIL",
	    "Cannot get SOA record for $zone from $nameserver (lame?): ".
		$res->errorstring ."\n");
	return;
    }
    &printerr("BAD", "$zone NS $nameserver: lame NS delegation\n") 
	unless ($soa_req->header->aa);
    return;
}