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#!/usr/bin/perl -w
#
# a2enmod by Stefan Fritsch <sf@debian.org>
# Licensed under Apache License 2.0
#
# The coding style is "perltidy -pbp"

use strict;
use Cwd 'realpath';
use File::Spec;
use File::Basename;
use File::Path;
use Getopt::Long;
use 5.014;
no if $] >= 5.017011, warnings => 'experimental::smartmatch';

my $quiet;
my $force;
my $maintmode;
my $purge;

Getopt::Long::Configure('bundling');
GetOptions(
    'quiet|q'     => \$quiet,
    'force|f'     => \$force,
    'maintmode|m' => \$maintmode,
    'purge|p'     => \$purge
) or exit 2;

my $basename = basename($0);
$basename =~ /^a2(en|dis)(mod|site|conf)((?:-.+)?)$/
    or die "$basename call name unknown\n";
my $act        = $1;
my $obj        = $2;
my $dir_suffix = $3;

my @essential_module_list = qw(alias auth_basic authn_file authz_host
    authz_user autoindex deflate dir env filter logio mime negotiation
    setenvif unixd version watchdog);
my $env_file = $ENV{APACHE_ENVVARS};
if (! $env_file) {
    if ($ENV{APACHE_CONFDIR}) {
        $env_file = "$ENV{APACHE_CONFDIR}/envvars";
    }
    else {
        $env_file = "/etc/apache2$dir_suffix/envvars";
    }
}
$ENV{LANG} = 'C';
read_env_file($env_file);

$act .= 'able';
my ( $name, $dir, $sffx, $reload );
if ( $obj eq 'mod' ) {
    $obj    = 'module';
    $dir    = 'mods';
    $sffx   = '.load';
    $reload = 'restart';
}
elsif ( $obj eq 'conf' ) {
    $obj    = 'conf';
    $dir    = 'conf';
    $sffx   = '.conf';
    $reload = 'reload';
}
else {
    $dir    = 'sites';
    $sffx   = '.conf';
    $reload = 'reload';
}
$name = ucfirst($obj);

my $confdir = $ENV{APACHE_CONFDIR} || "/etc/apache2$dir_suffix";
my $availdir = $ENV{ uc("APACHE_${dir}_AVAILABLE") }
    || "$confdir/$dir-available";
my $enabldir = $ENV{ uc("APACHE_${dir}_ENABLED") } || "$confdir/$dir-enabled";
my $statedir = $ENV{ uc("APACHE_STATE_DIRECTORY") } || "/var/lib/apache2";

$statedir .= "/$obj";

my $choicedir = $act eq 'enable' ? $availdir : $enabldir;
my $linkdir = File::Spec->abs2rel( $availdir, $enabldir );

my $request_reload = 0;
my $request_htcacheclean;
my $htc = "apache-htcacheclean$dir_suffix";
my $htc_service = "apache-htcacheclean";  # Service name for systemd
my $apache_service = "apache2";
if (defined($dir_suffix) and $dir_suffix ne '') {
    # Uses '@instance.service' suffix instead of '-instance' suffix
    my $service_suffix = '@' . substr($dir_suffix, 1) . '.service';
    $htc_service .= $service_suffix;
    $apache_service .= $service_suffix;
}
my $rc = 0;

if ( !scalar @ARGV ) {
    my @choices = myglob('*');
    print "Your choices are: @choices\n";
    print "Which ${obj}(s) do you want to $act (wildcards ok)?\n";
    my $input = <>;
    @ARGV = split /\s+/, $input;

}

my @objs;
foreach my $arg (@ARGV) {
    $arg =~ s/${sffx}$//;
    my @glob = myglob($arg);
    if ( !@glob ) {
        error("No $obj found matching $arg!\n");
        $rc = 1;
    }
    else {
        push @objs, @glob;
    }
}

foreach my $acton (@objs) {
    doit($acton) or $rc = 1;
}

my $htcstart = "";
my $apache_reload = "";
my $cmd = ($act eq "enable") ? "start" : "stop";
if (is_systemd()) {
    $htcstart = "  systemctl $cmd $htc_service\n";
    $apache_reload = "  systemctl $reload $apache_service\n";
} else {
    $htcstart = "  service $htc $cmd\n";
    $apache_reload = "  service apache2$dir_suffix $reload\n";
}
info(  "To activate the new configuration, you need to run:\n"
     . $apache_reload
     . ($request_htcacheclean ? $htcstart : "")
) if $request_reload;

exit($rc);

##############################################################################

sub myglob {
    my $arg = shift;

    my @glob = map {
        s{^$choicedir/}{};
        s{$sffx$}{};
        $_
    } glob("$choicedir/$arg$sffx");

    return @glob;
}

sub doit {
    my $acton = shift;

    my ( $conftgt, $conflink );
    if ( $obj eq 'module' ) {
        if ( $act eq 'enable' && $acton eq 'cgi' && threaded() ) {
            print
                "Your MPM seems to be threaded. Selecting cgid instead of cgi.\n";
            $acton = 'cgid';
        }

        $conftgt = "$availdir/$acton.conf";
        if ( -e $conftgt ) {
            $conflink = "$enabldir/$acton.conf";
        }
    }

    my $tgt  = "$availdir/$acton$sffx";
    my $link = "$enabldir/$acton$sffx";

    if ( !-e $tgt ) {
        if ( -l $link && !-e $link ) {
            if ( $act eq 'disable' ) {
                info("removing dangling symlink $link\n");
                unlink($link);

                # force a .conf path. It may exist as dangling link, too
                $conflink = "$enabldir/$acton.conf";

                if ( -l $conflink && !-e $conflink ) {
                    info("removing dangling symlink $conflink\n");
                    unlink($conflink);
                }

                return 1;
            }
            else {
                error("$link is a dangling symlink!\n");
            }
        }

        if ( $purge ) {
            switch_marker( $obj, $act, $acton );
            # exit silently, we are purging anyway
            return 1;
        }

        error("$name $acton does not exist!\n");
        return 0;
    }

    # handle module dependencies
    if ( $obj eq 'module' ) {
        if ( $act eq 'enable' ) {
            my @depends = get_deps("$availdir/$acton.load");
            do_deps( $acton, @depends ) or return 0;

            my @conflicts = get_deps( "$availdir/$acton.load", "Conflicts" );
            check_conflicts( $acton, @conflicts ) or return 0;
        }
        else {
            my @depending;
            foreach my $d ( glob("$enabldir/*.load") ) {
                my @deps = get_deps($d);
                if ( is_in( $acton, @deps ) ) {
                    $d =~ m,/([^/]+).load$,;
                    push @depending, $1;
                }
            }
            if ( scalar @depending ) {
                if ($force) {
                    do_deps( $acton, @depending ) or return 0;
                }
                else {
                    error(
                        "The following modules depend on $acton ",
                        "and need to be disabled first: @depending\n"
                    );
                    return 0;
                }
            }
        }
    }
    elsif ( $act eq 'enable' ) {
        my @depends = get_deps("$availdir/$acton$sffx");
        warn_deps( $acton, @depends ) or return 0;
    }

    if ( $act eq 'enable' ) {
        my $check = check_link( $tgt, $link );
        if ( $check eq 'ok' ) {
            if ($conflink) {

                # handle .conf file
                my $confcheck = check_link( $conftgt, $conflink );
                if ( $confcheck eq 'ok' ) {
                    info("$name $acton already enabled\n");
                    return 1;
                }
                elsif ( $confcheck eq 'missing' ) {
                    print "Enabling config file $acton.conf.\n";
                    add_link( $conftgt, $conflink ) or return 0;
                }
                else {
                    error(
                        "Config file $acton.conf not properly enabled: $confcheck\n"
                    );
                    return 0;
                }
            }
            else {
                info("$name $acton already enabled\n");
                return 1;
            }
        }
        elsif ( $check eq 'missing' ) {
            if ($conflink) {

                # handle .conf file
                my $confcheck = check_link( $conftgt, $conflink );
                if ( $confcheck eq 'missing' ) {
                    add_link( $conftgt, $conflink ) or return 0;
                }
                elsif ( $confcheck ne 'ok' ) {
                    error(
                        "Config file $acton.conf not properly enabled: $confcheck\n"
                    );
                    return 0;
                }
            }

            print "Enabling $obj $acton.\n";
            special_module_handling($acton);
            return add_link( $tgt, $link )
                && switch_marker( $obj, $act, $acton );
        }
        else {
            error("$name $acton not properly enabled: $check\n");
            return 0;
        }
    }
    else {
        if ( -e $link || -l $link ) {
            special_module_handling($acton);
            if ($obj eq 'module' && grep {$_ eq $acton} @essential_module_list) {
                  $force || essential_module_handling($acton);
            }
            remove_link($link);
            if ( $conflink && -e $conflink ) {
                remove_link($conflink);
            }
            switch_marker( $obj, $act, $acton );
            print "$name $acton disabled.\n";
        }
        elsif ( $conflink && -e $conflink ) {
            print "Disabling stale config file $acton.conf.\n";
            remove_link($conflink);
        }
        else {
            info("$name $acton already disabled\n");
            if ( $purge ) {
                switch_marker( $obj, $act, $acton );
            }
            return 1;
        }
    }

    return 1;
}

sub get_deps {
    my $file = shift;
    my $type = shift || "Depends";

    my $fd;
    if ( !open( $fd, '<', $file ) ) {
        error("Can't open $file: $!");
        return;
    }
    my $line;
    while ( defined( $line = <$fd> ) ) {
        chomp $line;
        if ( $line =~ /^# $type:\s+(.*?)\s*$/ ) {
            my $deps = $1;
            return split( /[\n\s]+/, $deps );
        }

        # only check until the first non-empty non-comment line
        last if ( $line !~ /^\s*(?:#.*)?$/ );
    }
    return;
}

sub do_deps {
    my $acton = shift;
    foreach my $d (@_) {
        info("Considering dependency $d for $acton:\n");
        if ( !doit($d) ) {
            error("Could not $act dependency $d for $acton, aborting\n");
            return 0;
        }
    }
    return 1;
}

sub warn_deps {
    my $acton = shift;
    my $modsenabldir = $ENV{APACHE_MODS_ENABLED} || "$confdir/mods-enabled";
    foreach my $d (@_) {
        info("Checking dependency $d for $acton:\n");
        if ( !-e "$modsenabldir/$d.load" ) {
            warning(
                "Module $d is not enabled, but $acton depends on it, aborting\n"
            );
            return 0;
        }
    }
    return 1;
}

sub check_conflicts {
    my $acton    = shift;
    my $haderror = 0;
    foreach my $d (@_) {
        info("Considering conflict $d for $acton:\n");

        my $tgt  = "$availdir/$d$sffx";
        my $link = "$enabldir/$d$sffx";

        my $confcheck = check_link( $tgt, $link );
        if ( $confcheck eq 'ok' ) {
            error(
                "Module $d is enabled - cannot proceed due to conflicts. It needs to be disabled first!\n"
            );

            # Don't return immediately, there could be several conflicts
            $haderror++;
        }
    }

    if ($haderror) {
        return 0;
    }

    return 1;
}

sub add_link {
    my ( $tgt, $link ) = @_;

    # create relative link
    if ( !symlink( File::Spec->abs2rel( $tgt, dirname($link) ), $link ) ) {
        die("Could not create $link: $!\n");
    }
    $request_reload = 1;
    return 1;
}

sub check_link {
    my ( $tgt, $link ) = @_;

    if ( !-e $link ) {
        if ( -l $link ) {

            # points to nowhere
            info("Removing dangling link $link");
            unlink($link) or die "Could not remove $link\n";
        }
        return 'missing';
    }

    if ( -e $link && !-l $link ) {
        return "$link is a real file, not touching it";
    }
    if ( realpath($link) ne realpath($tgt) ) {
        return "$link exists but does not point to $tgt, not touching it";
    }
    return 'ok';
}

sub remove_link {
    my ($link) = @_;

    if ( -l $link ) {
        unlink($link) or die "Could not remove $link: $!\n";
    }
    elsif ( -e $link ) {
        error("$link is not a symbolic link, not deleting\n");
        return 0;
    }
    $request_reload = 1;
    return 1;
}

sub threaded {
    my $result = "";
    $result = qx{/usr/sbin/apache2ctl -V | grep 'threaded'}
        if -x '/usr/sbin/apache2ctl';
    if ( $? != 0 ) {

        # config doesn't work
        if ( -e "$enabldir/mpm_prefork.load" )
        {
            return 0;
        }
        elsif (-e "$enabldir/mpm_worker.load"
            || -e "$enabldir/mpm_event.load" )
        {
            return 1;
        }
        else {
            error("Can't determine enabled MPM");

            # do what user requested
            return 0;
        }
    }
    if ( $result =~ / no/ ) {
        return 0;
    }
    elsif ( $result =~ / yes/ ) {
        return 1;
    }
    else {
        die("Can't parse output from apache2ctl -V:\n$result\n");
    }
}

sub info {
    print @_ if !$quiet;
}

sub error {
    print STDERR 'ERROR: ', @_;
}

sub warning {
    print STDERR 'WARNING: ', @_;
}

sub is_in {
    my $needle = shift;
    foreach my $e (@_) {
        return 1 if $needle eq $e;
    }
    return 0;
}

sub read_env_file {
    my $file = shift;

    -r $file or return;
    my @lines = qx{env - sh -c '. $file && env'};
    if ($?) {
        die "Could not read $file\n";
    }

    foreach my $l (@lines) {
        chomp $l;
        $l =~ /^(.*)?=(.*)$/ or die "Could not parse $file\n";
        $ENV{$1} = $2;
    }
}

sub switch_marker {
    die('usage: switch_marker([module|site|conf], [enable|disable], $name)')
        if @_ != 3;
    my $which = shift;
    my $what  = shift;
    my $name  = shift;

    my $mode = "admin";
    $mode = "maint" if $maintmode;

    #print("switch_marker $which $what $name\n");
    # TODO: get rid of the magic string(s)
    my $state_marker_dir = "$statedir/$what" . "d" . "_by_$mode";
    my $state_marker     = "$state_marker_dir/$name";
    if ( !-d $state_marker_dir ) {
        File::Path::mkpath("$state_marker_dir")
            || error(
            "Failed to create marker directory: '$state_marker_dir'\n");
    }

    # XXX: swap find with perl alternative
    my @markers = qx{find "$statedir" -type f -a -name "$name"};
    chomp(@markers);
    foreach (@markers) {
        unless ( unlink $_ ) {
            error("Failed to remove old marker '$_'!\n") && return 0;
        }
    }
    unless ($purge) {
        qx{touch "$state_marker"};
        if ( $? != 0 ) {
            error("Failed to create marker '$state_marker'!\n") && return 0;
        }
        return 1;
    }
}

sub essential_module_handling {
    my $module = shift;

    print "WARNING: The following essential module will be disabled.\n";
    print "This might result in unexpected behavior and should NOT be done\n";
    print "unless you know exactly what you are doing!\n $module\n\n";
    print "To continue type in the phrase 'Yes, do as I say!' or retry by passing '-f': ";
    my $input = <STDIN>;
    chomp($input);
    if ($input ne 'Yes, do as I say!') {
        print("Aborting\n");
        exit(1)
    }
}

sub special_module_handling {
    my $acton = shift;

    if ($obj ne 'module') {
        return;
    }

    given ($acton) {
        when ('ssl') {
            if ( $act eq 'enable' ) {
                info(  "See /usr/share/doc/apache2/README.Debian.gz on "
                     . "how to configure SSL and create self-signed "
                     . "certificates.\n"
                );
            }
        }
        when ('cache_disk') {
            $request_htcacheclean = 1;
            my $verb = "\u$act";
            my $command;
            $verb =~ s/e$/ing/;
            if (-d "/run/systemd" and -x "/bin/systemctl") {
                info("$verb external service $htc_service\n");
                $command = "systemctl $act $htc_service";
            } else {
                info("$verb external service $htc\n");
                $command = "update-rc.d $htc $act";
            }
            my $res = system($command);
            if ($res == 0) {
                info("The service will be started on next reboot.\n")
                    if $act eq 'enable';
            }
            else {
                warning("'$command' failed\n");
            }

        }
    }
}

sub is_systemd
{
    my $init = readlink("/proc/1/exe") || "";
    return scalar $init =~ /systemd/;
}