Introduce "Events" module

[people/stevee/guardian.git] / modules / Events.pm

package Guardian::Events;
use strict;
use warnings;

use Exporter qw(import);

our @EXPORT_OK = qw(Init CheckAction Update);

# Hash which stores all supported commands from the queue.
my %commands = (
	'count' => \&Counter,
	'block' => \&CallBlock,
	'unblock' => \&CallUnblock,
	'flush' => \&CallFlush,
);

# Hash to store addresses and their current count.
my %counthash = ();

# Hash to store all currentyl blocked addresses and a timestamp
# when the block for this address can be released.
my %blockhash = ();

# This object will contain the reference to the logger object after calling Init.
my $logger;

#
## The "Init" (Block) function.
#
## This function is responsible to initialize Block as a class based object.
## It has to be called once before any blocking event can be processed.
#
## The following arguments must be passed, during initialization:
## "BlockCount" and "BlockTime" which both have to be natural numbers.
#
sub Init (%) {
	my ( $class, %args ) = @_;
	my $self = \%args;

	# Fail, if some critical arguments are missing.
	unless ((exists($self->{BlockCount})) && (exists($self->{BlockTime}))) {
		die "Could not initialize Block: Too less arguments are given.\n";
	}

	# Use bless to make "$self" to an object of class "$class".
	bless($self, $class);

	# Assign logger object.
	$logger = $self->{Logger};

	# Log used firewall engine.
	$logger->Log("debug", "Using firewall engine: $self->{FirewallEngine}");

	# Try to load the specified firewall engine or die.
	my $module_name = "Guardian::" . $self->{FirewallEngine};
	eval "use $module_name; 1" or die "Could not load a module for firewall engine: $self->{FirewallEngine}!";

	# Return the class object.
	return $self;
}

#
## The main "CheckAction" function.
#
## This function is used to handle each recived event from the main event queue of guardian.
#
## It will check if the given command is valid and will pass it to the responsible function.
#
sub CheckAction ($$) {
	my $self = shift;
	my @event = split(/ /, $_[0], 4);
	my ($command, $address, $module, $message) = @event;

	# Check if we got an invalid command.
	unless(exists($commands{$command})) {
                $logger->Log("err", "The CheckAction function has been called with an unsupported command ($command)!");
                return;
        }

	# XXX
	# Check if the given address is valid.

	# Call required handler.
	my $error = $commands{$command}->($self, $address, $module, $message);

	# If we got any return code, something went wrong and should be logged.
	if ($error) {
		$logger->Log("err", "Got error: $error");
		return;
	}
}

#
## The main "Counter" function.
#
## This function is used to handle each count message + address, which has been sent by the main event
## loop of guardian.
#
## It stores the address and the current count into the counthash and increase the count each time when
## the same address should be counted again. When the current count reaches the configured BlockCount,
## the responsible function will be called to block the address.
#
sub Counter ($@) {
	my $self = shift;
	my ($address, $module, $message) = @_;

	# Log event.
	$logger->Log("debug", "$module reported $message for address: $address");

	# Increase existing count or start counting for new source addresses.
	if (exists($counthash{$address})) {
		# Skip already blocked addresses.
		if (exists($blockhash{$address})) {
			return undef;
		}

		# Increase count of the existing entry.
		$counthash{$address} = $counthash{$address} + 1;

		# Log altered count of the address.
		$logger->Log("debug", "Source $address now has count $counthash{$address}/$self->{BlockCount}...");
	} else {
		# Log that counting for the address has been started.
		$logger->Log("debug", "Start counting for $address...");

		# Set count to "1".
		$counthash{$address} = 1;
	}

	# Check if the address has reached the configured count limit.
	if ($counthash{$address} >= $self->{BlockCount}) {
		# Write out log message.
		$logger->Log("info", "Blocking $address for $self->{BlockTime} seconds...");

		# Call block subroutine to block the address.
		my $error = &CallBlock($self, $address, $module, $message);

		# Return the message if an error occurs.
		return $error;
	}

	# Everything worked well, return nothing.
	return undef;
}

#
## The RemoveBlocks function.
#
## This function periodly will be called and is responsible for releasing the block if the Blocktime
## on an address has expired.
#
## To do this, the code will loop through all entries of the blockhash and check
## if the estimiated BlockTime of each address has reached and so the block can be released.
#
sub RemoveBlocks () {
	my $self = shift;

	# Get the current time.
	my $time = time();

	# Loop through the blockhash.
	foreach my $address (keys %blockhash) {
		# Check if the blocktime for the address has expired.
		if ($blockhash{$address} <= $time) {
			# Call unblock subroutine.
			my $error = &CallUnblock($self, $address, "BlockTime", "has expired for $address");

			# Log error messages if returned.
			if ($error) {
				$logger->Log("err", "$error");
			}
		}
	}

	# Everything okay, return nothing.
	return undef;
}

#
## The CallBlock function.
#
## This function is called, if the BlockCount for an address is reached or a direct
## request for blocking an address has been recieved.
#
sub CallBlock ($@) {
	my $self = shift;
	my ($address, $module, $message) = @_;

	# Log the call for blocking an address.
	$logger->Log("info", "$module - $message");

	# Check if an entry for this address exists
	# in the blockhash. If not, the address has
	# not been blocked yet, call the responisible
	# function to do this now.
	unless (exists($blockhash{$address})) {
		# XXX
		# Add posibility to use a configure-able action.
		my $action;

		# Block the given address.
		my $error = &DoBlock($address, $action);

		# If we got back an error message something went wrong.
		if ($error) {
			# Exit function and return the error message.
			return $error;
		} else {
			# Address has been successfully blocked, print a log message.
			$logger->Log("debug", "Address $address successfully has been blocked...");
		}
	}

	# Generate time when the block will expire.
	my $expire = time() + $self->{BlockTime};

	# Store the blocked address and the expire time
	# in the blockhash.
	$blockhash{$address} = $expire;

	# Return nothing "undef" if everything is okay.
	return undef;
}

#
## CallUnblock function.
#
## This function is responsible for unblocking and deleting a given
## address from the blockhash.
#
sub CallUnblock ($) {
	my $self = shift;
	my ($address, $module, $message) = @_;

	# Log the call for unblocking an address.
	$logger->Log("info", "$module - $message");

	# Return an error if no entry for the given address
	# is present in the blockhash.
	unless (exists($blockhash{$address})) {
		return "Address $address was not blocked!";
	}

	# Unblock the address.
	my $error = &DoUnblock($address);

	# If an error message is returned, something went wrong.
	if ($error) {
		# Exit function and return the error message.
		return $error;
	} else {
		# Address successfully has been unblocked.
		$logger->Log("debug", "Address $address successfully has been unblocked...");
	}

	# Drop address from blockhash.
	delete ($blockhash{$address});

	# Everything worked well, return nothing.
	return undef;
}

1;