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#!/usr/bin/perl
# Copyright (C) 2014 Sergey Poznyakoff <gray@gnu.org>
#
# 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 3, 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, see <http://www.gnu.org/licenses/>.

use strict;
use Getopt::Long qw(:config gnu_getopt no_ignore_case);
use Pod::Usage;
use Pod::Man;
use Sys::Hostname;
use Cwd qw(getcwd realpath);
use Net::DNS;

my $script;        # This script name;

my $config_file = "/etc/vhostcname.conf";

my $cnamelist = "/var/run/vhostcname.cache";
my $host;          # This host name.
my @zone;          # List of acceptable DNS zones.
my $nameserver;    # Nameserver to use for updates.
my @tsig_args;     # Arguments to sing_tsig (path to the DNSSEC key file, or
                   # the key name and hash.
my $ttl = 3600;    # Default TTL.
my $confdir;       # Apache configuration directory.
my $confpat = "*"; # A globbing pattern for Apache configuration files.
my $dry_run;       # Dry-run mode.
my $debug;         # Debug level.
my $allow_wildcard_domains;

my $help;          # Display help summary.
my $man;           # Ditto in manpage format.

my $status = 0;    # Default exit status.

sub err {
    print STDERR "$script: ";
    print STDERR $_ for (@_);
    print STDERR "\n";
}		

sub abend {
    my $code = shift;
    &err;
    exit($code);
}

sub read_config_file($) {
    my $file = shift;
    unless (-f $file) {
	print STDERR "$script: configuration file $file does not exist\n"
	    if ($debug);
	return;
    }
    print STDERR "$script: reading $file\n" if ($debug);
    open(my $fd, "<", $file) or abend(1, "cannot open $file: $!");
    while (<$fd>) {
        chomp;
        s/^\s+//;
        s/\s+$//;
        s/\s+=\s+/=/;
        s/#.*//;
        next if ($_ eq "");
        unshift(@ARGV, "--$_");
    }
    close($fd);
}

# Domain names may be formed from the set of alphanumeric ASCII characters 
# (a-z, A-Z, 0-9). In addition the hyphen is permitted if it is surrounded 
# by characters, digits or hyphens, although it is not to start or end a 
# label.
sub valid_domain_name {
    my $name = shift;
    $name =~ s/^\*\.// if ($allow_wildcard_domains);
    foreach my $label (split(/\./, $name)) {
        $label =~ s/-+/-/g;
        $label =~ s/[a-zA-Z0-9]-[a-zA-Z0-9]//g;
        return 0 if $label =~ /^-/ or $label =~ /-$/;
        return 0 if $label =~ /[^a-zA-Z0-9]/;
    }
    return 1;
}

sub get_cnames($) {
    my $dir = shift;
    my %ret;

    foreach my $file (glob "$dir/$confpat") {
	next unless (-f $file);
	print STDERR "$script: reading cnames from $file\n" if ($debug > 2);
	
	open(my $fd, "<", $file) or do {
	    err("can't open file $file: $!");
	    next;
	};
	my $line = 0;
	while (<$fd>) {
	    s/#.*//;
	    s/^\s+//;
	    s/\s+$//;
	    next if (/^$/);
	    if (/^Server(Name|Alias)\s+(.*)/) {
		foreach my $name (split /\s+/, $2) {
		    unless (valid_domain_name($name)) {
			print STDERR "$script: $file:$line: $name: invalid domain name\n";
			next;
		    }
		    foreach my $z (@zone) {
			if ($name =~ /.*\.$z$/) {
			    if ($name =~ /^\*\.(.+)/ and $1 eq $z) {
				print STDERR "$script: $file:$line: $name: first-level wildcard\n";
				next;
			    }
			    $ret{$name} = $z;
			    last;
			}
		    }
		}
	    }
	}
	close($fd)
    }

    return %ret;
}

sub read_cname_list($) {
    my $file = shift;
    my %ret;

    if (-f $file) {
	open(my $fd, "<", $file) or abend(1, "cannot open $file: $!");
	while (<$fd>) {
	    chomp;
	    s/^\s+//;
	    s/\s+$//;
	    s/#.*//;
	    next if ($_ eq "");
	    my @a = split / /;
	    $ret{$a[0]} = $a[1];
	}
	close($fd);
    }
    return %ret;
}

sub write_cname_list {
    my ($file, %hash) = @_;

    return if ($dry_run);

    open(my $fd, ">", $file) or abend(1, "cannot open $file for writing: $!");
    foreach my $h (sort keys %hash) {
	print $fd "$h $hash{$h}\n";
    }
    close($fd);
}

sub ns_update {
    my $resolver = shift;
    my $name = shift;
    my $domain = shift;
    my %hash = @_;
    my %ignorerr;

    print STDERR "$script: updating $name in $domain: ".
	join(',', map { "$_ => $hash{$_}" } keys %hash) .
	"\n" if ($debug > 1);
    return 1 if ($dry_run);
    
    my $update = new Net::DNS::Update($domain);

    while (my ($k, $v) = each %hash) {
	if ($k eq 'ignore') {
	    $ignorerr{$v} = 1;
        } else {
	    $update->push($k => $v);
        }
    }
    $update->sign_tsig(@tsig_args) if ($#tsig_args >= 0);
    my $reply = $resolver->send($update);
    if ($reply) {
	if ($reply->header->rcode eq 'NOERROR') {
	    print STDERR "$script: update successful\n" if ($debug>3);
        } elsif ($ignorerr{$reply->header->rcode}) {
            print STDERR "$script: ignoring " . $reply->header->rcode . ': ' .
                join(',', map { "$_ => $hash{$_}" } keys %hash) . "\n"
		if ($debug>3);
	} else {
	    err("updating $name failed: ",
		join(',', map { "$_ => $hash{$_}" } keys %hash),
		': ',
		$reply->header->rcode);
	    $status = 2;
	    return 0;
	}
    } else {
	err("updating $name failed: ",
	    join(',', map { "$_ => $hash{$_}" } keys %hash),
	    ': ',
	    $resolver->errorstring);
	$status = 2;
	return 0;
    }
    return 1;
}

sub update_cnames_from_hash {
    my %hash = @_;
    
    print STDERR "$script: " . keys(%hash) . " names to update\n"
	if ($debug > 2);
    my %oldhash = read_cname_list($cnamelist);
    my @namelist = sort(keys(%hash));
    if (join(",", @namelist) eq join(".", sort(keys(%oldhash)))) {
	print STDERR "$script: nothing to update\n" if ($debug);
	return;
    }

    my $resolver = new Net::DNS::Resolver;
    $resolver->nameservers($nameserver) if defined($nameserver);
    
    my $name;
    foreach $name (@namelist) {
	if ($oldhash{$name}) {
	    delete $oldhash{$name};
	} else {
	    ns_update($resolver, $name, $hash{$name},
		      prereq => yxdomain($name),
		      update => rr_del($name),
                      ignore => 'NXDOMAIN');
	    print STDERR "$script: $name $ttl CNAME $host\n" if ($debug);
	    delete $hash{$name}
	        unless ns_update($resolver, $name, $hash{$name},
 			     update => rr_add("$name $ttl CNAME $host"));
	}
    }

    foreach $name (keys %oldhash) {
	ns_update($resolver, $name, $oldhash{$name},
		  prereq => yxrrset("$name CNAME"),
		  update => rr_del("$name CNAME"),
                  ignore => 'NXRRSET');
    }

    write_cname_list($cnamelist, %hash);
}

sub update_cnames_from_dir($) {
    update_cnames_from_hash(get_cnames(shift));
}
		      
sub nscleanup {
    print STDERR "$script: Removing DNS CNAME records\n" if ($debug);

    my $resolver = new Net::DNS::Resolver;
    $resolver->nameservers($nameserver) if defined($nameserver);

    my %hash = read_cname_list($cnamelist);
    foreach my $name (keys %hash) {
	print STDERR "$script: removing $name from $hash{$name}\n"
            if ($debug);
	delete $hash{$name}
	    if ns_update($resolver, $name, $hash{$name},
			 prereq => yxrrset("$name CNAME"),
			 update => rr_del("$name CNAME"),
                         ignore => 'NXRRSET');
    }

    write_cname_list($cnamelist, %hash);
}


###
($script = $0) =~ s/.*\///;

## Read configuration
read_config_file($ENV{'VHOSTCNAME_CONF'} ?
		 $ENV{'VHOSTCNAME_CONF'} : $config_file);

GetOptions("help" => \$man,
           "h" => \$help,
           "debug|d+" => \$debug,
	   "dry-run|n" => \$dry_run,
	   "hostname|H=s" => \$host,
	   "apache-config-pattern=s" => \$confpat,
	   "apache-config-directory=s" => \$confdir,
	   "ns-key-file=s" => sub {
	       abend(3, "NS key already set") if ($#tsig_args >= 0);
	       push @tsig_args, $_[1];
	   },
	   "ns-key=s" => sub {
	       abend(3, "NS key already set") if ($#tsig_args >= 0);
	       if ($_[1] =~ /(.+?)=(.+)/) {
                   push @tsig_args, $1;
                   push @tsig_args, $2;
               } else {
                   abend(3, "argument to --ns-key must be NAME=KEY");
               }
           },
	   "cname-file=s" => \$cnamelist,
	   "zone|z=s@" => \@zone,
	   "ttl=i" => \$ttl,
	   "server=s" => \$nameserver,
	   "allow-wildcard-domains" => \$allow_wildcard_domains
	   ) or exit(3);

pod2usage(-message => "$script: update DNS from Apache virtual host configuration",
	  -exitstatus => 0) if $help;
pod2usage(-exitstatus => 0, -verbose => 2) if $man;

unless (defined($confdir)) {
    foreach my $dir ("/etc/apache2", "/etc/httpd") {
	if (-e "$dir/sites-enabled" and -e "$dir/sites-available") {
	    $confdir = $dir;
	    last;
	}
	if (-e "$dir/vhosts.d") {
	    $confdir = "$dir/vhosts.d";
	    last;
	}
    }
    abend(3,
	  "don't know where virtual host configurations are located; use --apache-config-directory option")
	unless defined($confdir);
}

$host = hostname() unless defined($host);
push(@zone, $host) if ($#zone == -1);
$debug++ if ($dry_run);

if ($#ARGV == -1) {
    abend(3, "command not given") unless ($ENV{'DIREVENT_FILE'});
    print STDERR "$script: started as direvent handler for " .
	         "$ENV{'DIREVENT_GENEV_NAME'} on $ENV{'DIREVENT_FILE'}\n"
		 if ($debug);
    my $cwd = getcwd;
    my $update_dir;
    if (-d "$confdir/sites-available" && -d "$confdir/sites-enabled") {
	if ($cwd eq "$confdir/sites-available") {
	    foreach my $file (glob "$confdir/sites-enabled/$confpat") {
		next unless (-l $file);
		if (realpath(readlink($file)) eq 
		    "$confdir/sites-available/$ENV{'DIREVENT_FILE'}") {
		    $update_dir = "$confdir/sites-enabled";
		    last;
		}
	    }
	} elsif ($cwd eq "$confdir/sites-enabled") {
	    $update_dir = $cwd;
	}
    } else {
	$update_dir = $cwd;
    }

    update_cnames_from_dir($update_dir) if defined($update_dir);
} elsif ($#ARGV != 0) {
    abend(3, "too many arguments");
} elsif ($ARGV[0] =~ /^start|restart|force-restart|reload$/) {
    nscleanup if ($ARGV[0] =~ /start$/);
    my %cnames = get_cnames(-d "$confdir/sites-enabled" ?
			    "$confdir/sites-enabled" : $confdir);
    update_cnames_from_hash(%cnames);
    print STDERR "$script: no cnames defined\n" unless (keys(%cnames) > 0);
} elsif ($ARGV[0] eq "stop") {
    nscleanup;
} elsif ($ARGV[0] eq "status") {
    err("status command ignored");
} else {
    abend(3, "invalid command, try $script --help for more info");
}

exit($status);

__END__
=head1 NAME

vhostcname - synchronize DNS with Apache virtual host configuration

=head1 SYNOPSIS

B<vhostcname> [OPTIONS] B<COMMAND>

=head1 DESCRIPTION

The program takes a list of DNS zones and scans Apache virtual host
configuration files.  For each hostname found in B<ServerName> and
B<ServerAlias> statements, it checks whether this name ends in a
zone from the list, and if so, attempts to register this hostname
using the DNS dynamic updates mechanism (B<RFC 2136>).

A reverse operation is also supported: deregister all host name
registered on the previous run.

The mode of operation is requested by the B<COMMAND> argument.
The available B<COMMAND>s have been chosen so as to allow
B<vhostcname> to be run as one of the machine's startup
scripts.  The exact ways to register it to be run on server startup
and shutdown depend on the operating system and distribution in use.
For example, on Debian-based GNU/Linux:

    cd /etc/init.d
    ln -sf /usr/bin/vhostcname /etc/init.d
    update-rc.d vhostcname defaults

The program can also be ised as a B<direvent>(8) handler.  This use
allows for immediate updates of the DNS records upon any modifications
to the Apache configuration files.  The following example shows the
corresponding B<direvent.conf>(5) entry:    

    watcher {
        path /etc/apache2/sites-available;
        path /etc/apache2/sites-enabled;
        event (create,delete,write);
        timeout 10;
        option (stderr,stdout);
        command /usr/bin/vhostcname;
    }
    
=head1 COMMANDS

=over 4

=item B<start>

Scan the apache configuration files and register all server names matching
the supplied zones.
    
=item B<stop>

Deregister all hostnames registered previously.

=item B<restart>, B<force-restart>, B<reload>

Same as running B<vhostcname stop; vhostcname start>.    
    
=item B<status>

Ignored    
    
=back    
    
=head1 OPTIONS

=over 4    

=item B<--allow-wildcard-domains>

Allow the use of wildcard (B<*>).  When this option is in effect, a wildcard
will be allowed if it is the very first label in a domain name and it is
separated from the base zone (see the B<--zone> option) by one or more labels.
    
=item B<--apache-config-directory=>I<DIR>

Sets the Apache configuration directory.  I<DIR> should be either a directory
where virtual configuration file are located or a directory which hosts the
B<sites-available> and B<sites-enabled> directories.  In the latter case,
B<vhostcname> will look for files matching B<apache-config-pattern> in
I<DIR>B</sites-enabled>.

If this option is not given, B<vhostcname> will try to deduce where the
configuration files are located.  It will issue a warning message and
terminate if unable to do that.
    
=item B<--apache-config-pattern=>I<GLOB>

Shell globbing pattern for virtual host configuration files.  By default,
B<*> is used, meaning that B<vhostcname> will scan all files in the
configuration directory.
    
=item B<--cname-file=>I<NAME>

Name of the file where B<vhostcname> will keep successfully registered
host names.  Default is B</var/run/vhostcname.cache>.    
    
=item B<-d>, B<--debug>

Increases the debug level.  Multiple B<-d> options are allowed.
    
=item B<-n>, B<--dry-run>,

Enables I<dry-run> mode: print what would have been done without actually
doing it.    
    
=item B<--help>

Displays B<vhostcname> man page.
    
=item B<-h>

Displays a short help summary and exits.
    
=item B<-H>, B<--hostname>=I<NAME>

Sets the hostname.  Use this if B<vhostcname> is unable to correctly
determine it.
    
=item B<--ns-key=>I<NAME>=I<KEY>

Define the TSIG key.   
    
=item B<--ns-key-file=>I<KEYFILE>

Name of the key file.  The argument should be the name of a file
generated by the B<dnssec-keygen> utility.  Either B<.key> or B<.private>
file can be used.

This option cannot be used together with B<--ns-key>.    

=item B<--server=>I<NAME>

Name of the DNS server to use.  Normally B<vhostcname> determines what server
to use based on the B<SOA> record of the zone to be updated, so this option
is rarely needed.    
    
=item B<--ttl=>I<TIME>

TTL value for new DNS records.  Default is 3600.    
    
=item B<--zone=>I<NAME>

Name of the zone which B<vhostcname> can update.  Multiple B<--zone> options
can be given.

If no B<--zone> option is given, B<vhostcname> will take hostname as the
name of the zone.

=back

=head1 CONFIGURATION FILE

If the file B<etc/vhostcname.conf> exists, the program will read its
configuration from it.  A familiar UNIX configuration format is used.
Empty lines and UNIX comments are ignored.  Each non-empty line is either an
option name, or option assignment, i.e. B<opt>=B<val>, with any amount of
optional whitespace around the equals sign.  Valid option names are
the same as the long command line options, but without the leading B<-->.
For example:

  zone   = vhost.example.com
  ns-key-file = /etc/bind/Kvhost+157+43558.key
  ttl    = 3600

=head1 ENVIRONMENT

=over 4

=item B<VHOSTCNAME_CONF>

The name of the configuration file to use instead of the default
F</etc/vhostcname.conf>.

=back

=head1 EXIT CODE

=over 4

=item 0

Success

=item 1

Operating system error (unable to open file, etc.)

=item 2

Some of the host names could not be registered.    
    
=item 3

Command line usage error    

=back
    
=head1 BUGS

Only one key file can be given.  This means that if you use multiple
B<--zone> options, all zones must be configured to accept the same
DNSSEC key.  Ditto for the B<--server> option.    

=head1 SEE ALSO

B<direvent>(8).    
    
=head1 AUTHOR

Sergey Poznyakoff <gray@gnu.org>

=cut
    

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