firewall-whitelisting-remote-cgi

#!/usr/bin/env perl -T

=for comment

firewall whitelisting CGI program
by Jon Jensen <jon@endpointdev.com>

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 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, see <https://www.gnu.org/licenses/>.

2005-03-04 - created
2005-12-09 - support multiple host iptables changes
2006-05-26 - support groups of users each with different server access
2006-07-06 - tolerate groups without URLs in HTML output
2006-09-20 - adapt for OpenBSD and pf tables on the local machine
2006-09-21 - daemonize and make listen on UNIX socket to avoid need for suidperl
2006-09-22 - re-unify and run under sudo
2007-03-16 - switch to CGI-based authentication instead of HTTP basic auth;
             limit number of bad attempts per user; quell pfctl success message;
2007-06-29 - added support for remote pf firewall rule setting
2008-04-02 - adapted for End Point by Kiel Christofferson;
             added support for multiple commands per iptables run
2011-02-16 - added pastebot access
2011-12-28 - added use of COMMENT module with a timestamp
2012-03-24 - remove trailing \n from syslog messages where it appears as \012
           - start phasing out CGI module
           - move to HTML5, don't cache, auto-select username field, turn off browser autocomplete

=cut

use strict;
use warnings;
no warnings 'qw';
use utf8;
use IO::Handle;
use Sys::Syslog qw(:DEFAULT setlogsock);
use CGI ();
use Digest::MD5 qw(md5_hex);
use Authen::Htpasswd ();
use DB_File;

my $now_time = time();

# authentication settings
my $max_failed_attempts = 3;
my $access_path = '/home/firewall/access';
my $users_file = "$access_path/firewall.users";
my $groups_file = "$access_path/firewall.groups";
my $user_attempts_file = '/var/log/httpd/firewall.users.failed.attempts';
my $email = 'someone@your.domain';

# firewall opening settings
my $command_timeout_seconds = 10;
my $iptables = '/sbin/iptables';
my $pfctl = '/sbin/pfctl';
my $ssh = '/usr/bin/ssh';
my $ssh_key = '/root/.ssh/id_rsa.firewall-whitelist';

*STDOUT->autoflush(1);
*STDERR->autoflush(1);

die "This application may only be accessed via https.\n"
	unless $ENV{HTTPS};

my $ip = $ENV{REMOTE_ADDR};
my $q = CGI->new;
my @params = $q->param;
my $action = $q->param('firewall_action');
my $user = $q->param('firewall_user');
my $pass = $q->param('firewall_pass');

# clear tainted environment
%ENV = ();

setlogsock 'unix';
openlog 'firewall CGI', 'pid nowait', 'LOG_AUTH';


# Validate source IP address

if (! $ip) {
	perish("Connection is missing IP address");
}
elsif ($ip =~ /^(\d+\.\d+\.\d+\.\d+)$/) {
	@_ = split /\./, $1 || '';
	my @ip;
	for (@_) {
		push @ip, $_ if $_ < 256;
	}
	perish("Invalid IP address")
		unless @ip == 4;
	$ip = join '.', @ip;
	perish("Devious IP address: $ip")
		if $ip eq '0.0.0.0' or $ip eq '255.255.255.255';
	announce("Connection reported from $ip");
}
else {
	perish("Connection from invalid IP address '$ip'");
}


# Deal with dual page personality:
# ask for user info vs. process and open firewalls

my $onload = '';
my @msg;
my $problems = ' if you run into any problems';

my $pwfile = Authen::Htpasswd->new($users_file, { encrypt_hash => 'sha1' })
	or perish("Error connecting to password file $users_file");

tie my %user_attempts, 'DB_File', $user_attempts_file
	or perish("Error tie-ing $user_attempts_file");

if (! $action) {
	announce("Initial connection made (no action specified)");
	ask_for_id();
}
elsif ($action eq 'Log in') {
	authenticate() and open_firewalls();
}
elsif ($action eq 'change_password') {
	authenticate() and change_password();
}
else {
	perish("Invalid form action attempted: $action");
}


# Return HTML page

my $page_title = 'End Point Firewall';
my $msg = join '', @msg;

print "Content-Type: text/html; charset=UTF-8\r\n";
print "Cache-Control: private, no-store, no-cache\r\n";
print "X-UA-Compatible: IE=edge,chrome=1\r\n";
print "\r\n";

print <<END;
<!doctype html>
<!-- paulirish.com/2008/conditional-stylesheets-vs-css-hacks-answer-neither/ -->
<!--[if lt IE 7]> <html class="no-js lt-ie9 lt-ie8 lt-ie7" lang="en"> <![endif]-->
<!--[if IE 7]>    <html class="no-js lt-ie9 lt-ie8" lang="en"> <![endif]-->
<!--[if IE 8]>    <html class="no-js lt-ie9" lang="en"> <![endif]-->
<!--[if gt IE 8]><!--> <html class="no-js" lang="en"> <!--<![endif]-->

<head>
	<title>$page_title</title>
	<style type="text/css">
html { font-size: 100%; -webkit-text-size-adjust: 100%; -ms-text-size-adjust: 100%; }
html, button, input, select, textarea { font-family: sans-serif; color: #222; }
body { margin: 1em; font-size: 1em; line-height: 1.4; }
::-moz-selection { background: #fe57a1; color: #fff; text-shadow: none; }
::selection { background: #fe57a1; color: #fff; text-shadow: none; }
a { color: #00e; }
a:visited { color: #551a8b; }
a:hover { color: #06e; }
a:focus { outline: thin dotted; }
a:hover, a:active { outline: 0; }
abbr[title] { border-bottom: 1px dotted; }
b, strong { font-weight: bold; }
blockquote { margin: 1em 40px; }
dfn { font-style: italic; }
hr { display: block; height: 1px; border: 0; border-top: 1px solid #ccc; margin: 1em 0; padding: 0; }
ins { background: #ff9; color: #000; text-decoration: none; }
mark { background: #ff0; color: #000; font-style: italic; font-weight: bold; }
pre, code, kbd, samp { font-family: monospace, serif; _font-family: 'courier new', monospace; font-size: 1em; }
pre { white-space: pre; white-space: pre-wrap; word-wrap: break-word; }
q { quotes: none; }
q:before, q:after { content: ""; content: none; }
small { font-size: 85%; }
sub, sup { font-size: 75%; line-height: 0; position: relative; vertical-align: baseline; }
sup { top: -0.5em; }
sub { bottom: -0.25em; }
ul, ol { margin: 1em 0; padding: 0 0 0 40px; }
dd { margin: 0 0 0 40px; }
nav ul, nav ol { list-style: none; list-style-image: none; margin: 0; padding: 0; }
img { border: 0; -ms-interpolation-mode: bicubic; vertical-align: middle; }
svg:not(:root) { overflow: hidden; }
figure { margin: 0; }
form { margin: 0; }
fieldset { border: 0; margin: 0; padding: 0; }
label { cursor: pointer; }
legend { border: 0; *margin-left: -7px; padding: 0; white-space: normal; }
button, input, select, textarea { font-size: 100%; margin: 0; vertical-align: baseline; *vertical-align: middle; }
button, input { line-height: normal; }
button, input[type="button"], input[type="reset"], input[type="submit"] { cursor: pointer; -webkit-appearance: button; *overflow: visible; }
button[disabled], input[disabled] { cursor: default; }
input[type="checkbox"], input[type="radio"] { box-sizing: border-box; padding: 0; *width: 13px; *height: 13px; }
input[type="search"] { -webkit-appearance: textfield; -moz-box-sizing: content-box; -webkit-box-sizing: content-box; box-sizing: content-box; }
input[type="search"]::-webkit-search-decoration, input[type="search"]::-webkit-search-cancel-button { -webkit-appearance: none; }
button::-moz-focus-inner, input::-moz-focus-inner { border: 0; padding: 0; }
textarea { overflow: auto; vertical-align: top; resize: vertical; }
input:valid, textarea:valid {  }
input:invalid, textarea:invalid { background-color: #f0dddd; }
table { border-collapse: collapse; border-spacing: 0; }
td { vertical-align: top; }
	</style>
</head>

<body$onload>
	<h1>$page_title</h1>
	$msg
</body>
</html>
END


# Done!

untie %user_attempts
	or perish("Error untie-ing file $user_attempts_file!");

announce("HTML response sent and all done");
closelog;
exit;


# Utility routines

sub announce {
	syslog 'LOG_NOTICE', '%s', $_[0];
	return;
}

sub error {
	syslog 'LOG_ERR', '%s', $_[0];
	return;
}

sub perish {
	syslog 'LOG_ERR', '%s', $_[0];
	closelog;
	die @_;
}


# Authenticate the user

sub authenticate {
	# make sure user's not failed too many times
	my $attempts = ++$user_attempts{$user};
	if ($attempts > $max_failed_attempts) {
		push @msg, qq{<p>Your account is locked due to too many failed login attempts. <b>It will be automatically unlocked within 30 minutes. Please wait and try again.</b> If you are still unable to log in, contact your manager.</p>};
		announce("Refused user '$user' because $attempts attempts have been made (limit of $max_failed_attempts allowed).");
		$problems = ' to have your account unlocked';
		return;
	}

	# check user + password
	my $valid;
	eval {
		$valid = $pwfile->check_user_password($user, $pass);
	};
	undef $valid if $@;
	unless ($valid) {
		my $lockout = ($attempts >= $max_failed_attempts);
		my $m = 'The username and password you provided are incorrect.';
		$m .= ' Your account has now been locked due to too many failed login attempts. <b>Your account will be automatically unlocked after 30 minutes. Please wait 30 minutes and try again.</b> If you are still unable to log in, '
			if $lockout;
		push @msg, qq{<p>$m</p>};
		ask_for_id() unless $lockout;
		$problems = ' to have your account unlocked';
		announce(
			"Authentication for user '$user' failed"
			. ($lockout
				? " and account is now locked because the limit of"
					. " $max_failed_attempts failed attempts has been reached"
				: '')
			. '.'
		);
		return;
	}

	announce("User '$user' authenticated.");

	# reset failed attempt counter
	$user_attempts{$user} = 0;

	return 1;
}


# Open the firewall(s)

sub open_firewalls {

	perish("open_firewalls called with no user specified!")
		unless $user;


	# Find out which groups the user is in

	my %in_group;
	{
		local @ARGV = $groups_file;
		while (<>) {
			next if /^\s*$/ or /^\s*#/;
			my ($group, $users) = /^\s*(\w+)\s*:\s*(.*)/
				or perish("Invalid groups file");
			$in_group{$group} = 1 if $users =~ /\b$user\b/;
		}
	}


	# Define the various hosts and firewall rules

	my @iptables_base = ($iptables, '-A', 'dynamic_ip', '-s', $ip);

	my $user = $1 if $user =~ /^(\w+)$/; # untaint
	my $iptables_comment = '-m comment --comment "whitelist-' . $user . '-' . $now_time . '"';
	my %host_rules = (
		bastion => [
			[
				'iptables', 'localhost',
				"-p tcp --dport 22 $iptables_comment -j ACCEPT",
			],
		],
		intranet => [
			[
				'iptables', 'intranet.yourdomain.tld',
				"-p tcp -m multiport --dports 22,80,443 $iptables_comment -j ACCEPT",
			],
		],
	);


	# Open the appropriate firewall(s) for this user

	my (%success, %errors);

	for my $group (keys %in_group) {
		my $argset = $host_rules{$group} or die "Missing rules for host $group?\n";
		for my $args (@$argset) {
			my $fw   = shift @$args;
			my $host = shift @$args;

			my (@cmd, $ret, $errmsg);

			if ($fw eq 'pf') {
				@cmd = ($pfctl, '-q', '-t', $group, '-T', 'add', $ip);
			}
			elsif ($fw eq 'iptables') {
				@cmd = join('; ', map { join ' ', @iptables_base, $_ } @$args);
			}
			else {
				die "Unknown firewall type in host_rules: $fw\n";
			}

			undef $ret;
			undef $errmsg;
			if ($host eq 'localhost') {
				$ret = system(@cmd);
			}
			else {
				my $pid = fork;
				if (! defined $pid) {
					die "Couldn't fork: $!\n";
				}
				elsif (! $pid) {
					# child
					exec(
						$ssh,
						'-axqT',
						'-o', 'BatchMode=yes',
						'-i', $ssh_key,
						'-l', 'root',
						$host,
						join(' ', @cmd),
					);
				}
				# parent
				$ret = $?;
				eval {
					local $SIG{ALRM} = sub { kill 15, $pid; die "timeout\n" };
					alarm $command_timeout_seconds;
					waitpid $pid, 0;
					alarm 0;
				};
				$errmsg = $@ if $@;
			}

			if ($ret) {
				my $errstr;
				if ($ret == -1) {
					$errstr = "failed to execute: $!";
				}
				elsif ($ret & 127) {
					$errstr = sprintf "child died with signal %d, %s coredump",
						($ret & 127), ($ret & 128) ? 'with' : 'without';
				}
				else {
					my $real = $ret >> 8;
					if ($real != 0) {
						$errstr = sprintf "child exited with value %d", $real;
					}
				}

				if ($errstr) {
					error("Error with $host: $errstr");
					++$errors{$group};
				}
			}
			elsif ($errmsg) {
				error("Error with $host: $errmsg");
				++$errors{$group};
			}
			else {
				++$success{$group};
				my $logmsg = "IP has been added to $host";
				$logmsg .= '/' . $group if $host eq 'localhost';
				$logmsg .= ' whitelist';
				announce($logmsg);
			}
		}
	}

	if (%success) {
		push @msg, "<p>Your IP address, $ip, has been added to the firewall whitelist of servers in these groups:</p>\n";
		push @msg, "<ul>\n";
		my %sites = (
			intranet => {
				Wiki => 'https://wiki.yourdomain.tld/',
			},
		);
		for my $group (sort keys %success) {
			push @msg, "<li>$group: ";
			my $set = $sites{$group};
			my @items;
			for my $item (sort keys %$set) {
				$item = qq{<a href="$set->{$item}">$item</a>} if $set->{$item};
				push @items, $item;
			}
			push @msg, join(', ', @items);
			push @msg, "</li>\n";
		}
		push @msg, "</ul>\n";

		if (%errors) {
			push @msg, "<p>But there were errors for these: " . join(', ', sort keys %errors) . ".</p>";
			$problems = ' about this problem';
		}
	}
	else {
		if (%errors) {
			push @msg, "<p>There was a problem adding your IP address, $ip, to the firewall whitelist.</p>";
		}
		push @msg, "<p>You are not part of any access groups. Please contact your manager so you can be added as appropriate.</p>";
	}

	return;

}


sub ask_for_id {
	push @msg, qq{<form name="auth" method="post" action="" enctype="multipart/form-data">\n};
	push @msg, qq{<table>\n};

	push @msg, qq{<tr>\n};
	push @msg, qq{<td>Username:</td>\n};
	push @msg, qq{<td><input type="text" name="firewall_user" autocomplete="off" size="20"></td>\n};
	push @msg, qq{</tr>\n};

	push @msg, qq{<tr>\n};
	push @msg, qq{<td>Password:</td>\n};
	push @msg, qq{<td><input type="password" name="firewall_pass" autocomplete="off" size="20"></td>\n};
	push @msg, qq{</tr>\n};

	push @msg, qq{<tr colspan="2">\n};
	push @msg, qq{<td><input type="submit" name="firewall_action" value="Log in"></td>\n};
	push @msg, qq{</tr>\n};

	push @msg, qq{</table>\n};
	push @msg, qq{</form>\n};

	$onload = qq{ onLoad="document.auth.firewall_user.focus()"};
	return;
}