#!/usr/bin/perl # # dyndns.pl - CGI-BIN script to handle Dynamic DNS updates through http # # Last Update: $Date$ # # Latest version and documentation on http://projects.lindenaar.net/p/dyndns # # Copyright (C) 2013 Frederik Lindenaar # # This program is free software; you can redistribute it and/or modify it under # the terms of the GNU General Public License as published by the Free Software # Foundation; either version 2 of the License, or (at your option) any later # version. # # This program is distributed in the hope that it will be useful, but WITHOUT # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS # FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. # # You should have received a copy of the GNU General Public License along with # this program; if not, write to the Free Software Foundation, Inc., 59 Temple # Place, Suite 330, Boston, MA 02111-1307 USA # use strict; use CGI; use POSIX; use Net::DNS; use feature 'state'; ############################## # Configuration section my $DNSServer = '192.168.1.1'; # DNS Server to communicate with (use IP!) my $ExpandCNAMEs = 1; # CNAME levels to expand (0 to disable) my $AllowDebugKey = 'on'; # Debuging, 'off' to disable, '' for always on # and other values to enable with debug= param. my $AuthMode = 'remote'; # either 'static', 'remote' or 'both' my $StaticSigner = ''; # required for AuthMode 'static' or 'both' my $StaticKey = ''; # required for AuthMode 'static' or 'both' my $RequireRR = ''; # Require existing record of this type for upd. my $ExpireAfter = '1w'; # Expire time for registrations in minutes, # hours, weeks or seconds. format: [0-9]+[mhws]? my @ReplaceRR = ('A', 'AAAA', 'TXT'); # Records types to replace in update my $UpdateTXT = 'Last DynDNS update on '; my $DeleteTXT = 'DynDNS cleared on '; ############################## # Support functions my %months = (Jan=> 0, Feb=> 1, Mar=> 2, Apr=> 3, May=>4, Jun=> 5, Jul=> 6, Aug=> 7, Sep=> 8, Sep=> 8, Oct=> 9, Nov=> 10, Dec=> 11); # Parse the date and return time for: Sun May 26 21:22:15 2013 sub parse_localtime($) { my ($day, $month, $mday, $time, $year)=split(' ', $_[0]); return mktime(reverse(split(':',$time)),$mday,$months{$month},$year-1900); } sub is_ipv4 { return $_[0]=~/^((25[0-5]|(2[0-4]|[01]?[0-9]?)[0-9])(\.|$)){4}/; } sub is_ipv6 { return $_[0]=~/^([0-9a-fA-F]{0,4}(:|$)){3,8}/i; } sub periodSeconds($) { my ($number, $units) = ($_[0]=~/^(\d+)([smhdw])?$/); if($number && $units && $units cmp 's') { $number *= 60; # Convert to minutes if($units cmp 'm') { $number *= 60; # Convert to hours if($units cmp 'h') { $number *= 24; # Convert to days if($units cmp 'd') { $number *= 7; # Convert to weeks } } } } return $number; } # Provide a resolver object for further use, re-using the initially created one sub getResolver() { state $resolver; unless($resolver) { $resolver = Net::DNS::Resolver->new( nameservers => [ $DNSServer ], recurse => 0, ); } return $resolver; } my %DNS_label = ( A => 'IPv4 Address', AAAA => 'IPv6 Address', CNAME => 'Alias', TXT => 'Additional Information', MX => 'Mail Server', NS => 'Name Server', HINFO => 'Host Information', ); sub DNS_decode_rr($) { my ($rr) = @_; return $rr->address if($rr->type eq 'A'); return $rr->address if($rr->type eq 'AAAA'); return lc($rr->cname) if($rr->type eq 'CNAME'); return $rr->txtdata if($rr->type eq 'TXT'); return $rr->nsdname if($rr->type eq 'NS'); return $rr->exchange.' (priority '.$rr->preference.')' if($rr->type eq 'MX'); return $rr->cpu.', '.$rr->os if($rr->type eq 'HINFO'); die "No support for $rr->type in DNS_get()!, aborted!"; } # Retrieve a single value from the DNS server of a given type or everything sub DNS_get($;$) { my ($host, $type) = @_; if (my $response = getResolver()->send($host, $type || 'ANY')) { return $response unless($type); foreach my $rr ($response->answer) { next unless $rr->type eq $type; return DNS_decode_rr($rr); } } else { die 'DNS query failed: ', getResolver()->errorstring, "\n"; } } # Check whether the hostname provided is actually a CNAME, returns the host # it points to in case of a CNAME or the original hostname if it is not. sub expand_CNAME($;$) { my ($host, @found) = @_; if(my $cname=DNS_get($host, 'CNAME')) { push(@found, $host); die $found[0]."has > $ExpandCNAMEs level deep CNAME chain, aborting!\n" unless($#found < $ExpandCNAMEs); foreach my $r (@found) { die "found CNAME loop for $host, aborting!\n" if($cname eq $r); } return &expand_CNAME($cname, @found); } return $host; } # Method to perform an DNS Update for a single host sub DNS_Update($$$$$$$) { my ($dnsdomain, $dnshost, $ipv4, $ipv6, $signer, $key, $debug) = @_; my $dnsupdate = Net::DNS::Update->new($dnsdomain); # If $RequireRR is set, ensure an records of specified type exist for the name $dnsupdate->push(pre => yxrrset("$dnshost. $RequireRR")) if($RequireRR); # Replace any existing A, AAAA and TXT entries (update was requested) foreach my $rrtype (@ReplaceRR) { $dnsupdate->push(update=>rr_del("$dnshost. $rrtype")); } # Add new A and AAAA record based on whether ipv4 and ipv6 address provided $dnsupdate->push(update=>rr_add("$dnshost. 3600 A $ipv4")) if($ipv4); $dnsupdate->push(update=>rr_add("$dnshost. 3600 AAAA $ipv6")) if($ipv6); # Always add a new TXT record with the timestamp of the last update my $txt = ($ipv4 or $ipv6) ? $UpdateTXT : $DeleteTXT; $dnsupdate->push(update=>rr_add($dnshost. '. 3600 TXT "' . $txt . localtime() . '"')) if($txt); # Sign the request with the signer and key $dnsupdate->sign_tsig($signer, $key); my $debugmessage = ($debug) ? "\n\n\n========================================================\n" . $dnsupdate->string . "\n" : "\n"; if(my $response = getResolver()->send($dnsupdate)) { $debugmessage .= $response->string . "\n" if($debug); if ($response->header->rcode eq 'NOERROR') { return (200, "OK - DNS update for $dnshost succeeded: " . $response->header->rcode . $debugmessage); } else { # REFUSED, FORMERR return (400, "ERROR - DNS update for $dnshost failed: " . $response->header->rcode . $debugmessage); } } else { return (503, 'ERROR - DNS update for $dnshost failed: '. getResolver()->errorstring. $debugmessage); } } ############################## # Handlers for the different requests sub handle_update($$$$$$) { my ($cgi, $mode, $host, $dnshost, $dnsdomain, $debug) = @_; # Get signer and key parameters my $signer = ($AuthMode eq 'static') ? $StaticSigner : ($cgi->param('user') || (($AuthMode eq 'both') ? $StaticSigner : $host)); my $key = ($AuthMode eq 'static') ? $StaticKey : ($cgi->param('secret') || (($AuthMode eq 'both') ? $StaticSigner : undef)); # perform the action my ($statuscode, $statusmessage); if($mode eq 'delete') { ($statuscode, $statusmessage) = DNS_Update($dnsdomain, $dnshost, undef, undef, $signer, $key, $debug) } else { # Get ipv4, and ipv6 parameters my $remote_addr = $cgi->remote_addr; my $ipv4addr = $cgi->param('ipv4addr') || $cgi->param('ip') || (is_ipv4($remote_addr) ? $remote_addr : undef); my $ipv6addr = $cgi->param('ipv6addr') || (! $ipv4addr and is_ipv6($remote_addr)) ? $remote_addr : undef; ($statuscode, $statusmessage) = DNS_Update($dnsdomain, $dnshost, $ipv4addr, $ipv6addr, $signer, $key, $debug); } # And report back the status print $cgi->header(-status=>$statuscode, -type=>'text/plain'), $statusmessage; } sub handle_expire($$$$$$) { my ($cgi, $mode, $host, $dnshost, $dnsdomain, $debug) = @_; # Get signer and key parameters my $signer = ($AuthMode eq 'static') ? $StaticSigner : ($cgi->param('user') || (($AuthMode eq 'both') ? $StaticSigner : $host)); my $key = ($AuthMode eq 'static') ? $StaticKey : ($cgi->param('secret') || (($AuthMode eq 'both') ? $StaticSigner : undef)); my $debugmsg = ($debug) ? "\n" : ''; # perform the action if(my $period = periodSeconds($ExpireAfter)) { my $validafter = time - $period; if($debug) { $debugmsg .= "ExpireAfter $ExpireAfter, expiring all entries older than "; $debugmsg .= localtime($validafter) . "\n"; } foreach my $rr (getResolver->axfr($dnsdomain)) { next if($rr->name eq $dnsdomain); if($rr->type eq 'TXT' && $rr->txtdata=~/$UpdateTXT(.*\d\d:\d\d:\d\d \d{4})$/){ if(my $lastupdate = parse_localtime($1)) { DNS_Update($dnsdomain, $dnshost, undef, undef, $signer, $key, $debug) unless($lastupdate > $validafter); if($debug) { $debugmsg .= ($lastupdate > $validafter) ? 'Keeping ' : 'Expiring '; $debugmsg .= $rr->name . " last update ($1)\n"; } } elsif($debug) { $debugmsg .= 'Skipping '. $rr->name ." TXT: '". $rr->txtdata ."'\n"; } } } # And report back the status print $cgi->header(-status=>200, -type=>'text/plain'), "OK - DNS expiry for $dnsdomain succeeded\n" . $debugmsg; } } sub handle_status($$$$$$) { my ($cgi, $mode, $host, $dnshost, $dnsdomain, $debug) = @_; my $title = "DynDNS Updater - $host"; print $cgi->header(-status=>200), $cgi->start_html(-title => $title), $cgi->h1($title); print $cgi->p("$host resolves to $dnshost") if($host cmp $dnshost); print $cgi->p("Current DNS information for $dnshost:"), $cgi->start_table, $cgi->Tr({-align=>'LEFT',-valign=>'TOP'}, [ $cgi->th(['Field', 'Value']) ]); foreach my $rr (DNS_get($dnshost)->answer) { print $cgi->Tr([ $cgi->td([$DNS_label{$rr->type}, DNS_decode_rr($rr)]) ]); } print $cgi->end_table(); print $cgi->end_html(); } sub handle_view($$$$$$) { my ($cgi, $mode, $host, $dnshost, $dnsdomain, $debug) = @_; my $title = "DynDNS Updater - $dnsdomain"; print $cgi->header(-status=>200), $cgi->start_html(-title => $title), $cgi->h1($title); print $cgi->p("Current DNS information for $dnsdomain:"), $cgi->start_table, $cgi->Tr({-align=>'LEFT',-valign=>'TOP'}, [ $cgi->th(['Name', 'Field', 'Value']) ]); my $lastname = ''; foreach my $rr (getResolver->axfr($dnsdomain)) { next if($rr->name eq $dnsdomain); print $cgi->Tr([ $cgi->td([ ($lastname cmp $rr->name) ? $rr->name : '', $DNS_label{$rr->type}, DNS_decode_rr($rr)]) ]); $lastname = $rr->name; } print $cgi->end_table(); print $cgi->end_html(); } my $cgi = CGI->new; ############################## # Validate Configuration my $CE = 'Configuration Error:'; die "$CE \$AuthMode '$AuthMode' is unsupported must be remote, static or both\n" unless $AuthMode=~/remote|static|both/; die "$CE \$StaticSigner must be set for \$AuthMode '$AuthMode'\n" unless ($StaticSigner or $AuthMode eq 'remote'); die "$CE \$StaticKey must be set for \$AuthMode '$AuthMode'\n" unless ($StaticKey or $AuthMode eq 'remote'); die "$CE \$RequireRR is set to unsupported type '$RequireRR'\n" if ($RequireRR and not $DNS_label{$RequireRR}); die "$CE \$ExpireAfter '$ExpireAfter' is not supported\n" unless ($ExpireAfter=~/^\d+[smhw]$/); die "$CE \$UpdateTXT must be set when \$ExpireAfter is set\n" if($ExpireAfter and not $UpdateTXT); foreach my $rrtype (@ReplaceRR) { die "$CE \$ReplaceRR contains unsupported type '$rrtype'\n" unless ($DNS_label{$rrtype}); } ############################## # Determine what to do and fetch the input parameters my $mode = $cgi->path_info || $cgi->param('mode') || '/status'; $mode=~s/^\/([^\/]+)(\/(.*))?/$1/; my $host = $cgi->param('host') || $3; my $debug = ($AllowDebugKey eq 'off') ? 0 : ($AllowDebugKey eq ($cgi->param('debug') || '')); ############################## # Dispatch the request to the correct handler my %handlers = ( status => \&handle_status, update => \&handle_update, delete => \&handle_update, view => \&handle_view, expire => \&handle_expire, ); if($host eq '' and $mode cmp 'view' and $mode cmp 'expire') { print $cgi->header(-status=>400, -type=>'text/plain'), "ERROR - No host name to act on specified\n"; } elsif(my $handler = $handlers{$mode}) { # Replace provided host with that of a CNAME it points to and determine domain my $dnshost = ($host) ? expand_CNAME($host) : undef; my $dnsdomain = $cgi->param('domain') || ($dnshost=~/\.(.*)$/)[0]; $handler->($cgi, $mode, $host, $dnshost, $dnsdomain, $debug); } else { print $cgi->header(-status=>($cgi->path_info) ? 404 : 400, -type=>'text/plain'), "ERROR - File Not Found / Invalid Mode '$mode' specified\n"; }