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-- Gemeinschaft 5 module: perimeter class
-- (c) AMOOMA GmbH 2013
--
module(...,package.seeall)
Perimeter = {}
function Perimeter.new(self, arg)
arg = arg or {}
object = arg.object or {}
setmetatable(object, self);
self.__index = self;
self.log = arg.log;
self.class = 'perimeter'
self.database = arg.database;
self.domain = arg.domain;
self.sources = {};
self.checks_available = {
check_frequency = self.check_frequency,
check_username_scan = self.check_username_scan,
check_bad_headers = self.check_bad_headers,
};
return object;
end
function Perimeter.setup(self, event)
require 'common.configuration_table';
local config = common.configuration_table.get(self.database, 'perimeter');
self.contact_count_threshold = 10;
self.contact_span_threshold = 2;
self.name_changes_threshold = 2;
self.blacklist_file = '/var/opt/gemeinschaft/firewall/blacklist';
self.blacklist_file_comment = '# PERIMETER_BAN - points: {points}, generated: {date}';
self.blacklist_file_entry = '{received_ip} udp 5060';
self.ban_command = 'sudo /sbin/service shorewall refresh';
self.ban_threshold = 20;
self.ban_tries = 1;
if config and config.general then
for key, value in pairs(config.general) do
self[key] = value;
end
end
self.checks = config.checks;
self.bad_headers = config.bad_headers;
self.log:info('[perimeter] PERIMETER - setup perimeter defense');
end
function Perimeter.record_load(self, event)
if not self.sources[event.key] then
self.sources[event.key] = {
contact_first = event.timestamp,
contact_last = event.timestamp,
contact_count = 0,
span_contact_count = 0,
span_start = event.timestamp,
points = 0,
banned = 0,
}
end
return self.sources[event.key];
end
function Perimeter.format_date(self, value)
local epoch = tonumber(tostring(value/1000000):match('^(%d-)%.'));
return os.date('%Y-%m-%d %X', tonumber(epoch)) .. '.' .. (value-(epoch*1000000));
end
function Perimeter.record_update(self, event)
event.record.contact_last = event.timestamp;
event.record.contact_count = event.record.contact_count + 1;
event.record.points = event.points or event.record.points;
event.record.span_start = event.span_start or event.record.span_start;
event.record.span_contact_count = (event.span_contact_count or event.record.span_contact_count) + 1;
event.record.users = event.users or event.record.users;
end
function Perimeter.check(self, event)
event.record = self:record_load(event);
-- self.log:debug('[', event.key, '/', event.sequence, '] PERIMETER_CHECK - received: ', event.received_ip, ':', event.received_port, ', contacts: ', event.record.contact_count, ', since: ', self:format_date(event.record.contact_first), ', points: ', event.record.points);
if event.record.banned <= self.ban_tries then
for check_name, check_points in pairs(self.checks) do
if self.checks_available[check_name] then
local result = self.checks_available[check_name](self, event);
if tonumber(result) then
event.points = (event.points or event.record.points) + result * check_points;
end
end
end
end
if (event.points or event.record.points) > self.ban_threshold and event.record.banned <= self.ban_tries then
if event.record.banned > 0 and event.record.banned == self.ban_tries then
self.log:warning('[', event.key, '/', event.sequence, '] PERIMETER_BAN_FUTILE - points: ', event.points,', event: ', event.class, ', from: ', event.from_user, '@', event.from_host, ', to: ', event.to_user, '@', event.to_host);
else
self.log:notice('[', event.key, '/', event.sequence, '] PERIMETER_BAN - threshold reached: ', event.points,', event: ', event.class, ', from: ', event.from_user, '@', event.from_host, ', to: ', event.to_user, '@', event.to_host);
if event.record.banned == 0 then
self:append_blacklist_file(event);
end
self:execute_ban(event);
end
event.record.banned = event.record.banned + 1;
event.span_start = event.timestamp;
event.span_contact_count = 0;
event.points = 0;
end
self:record_update(event);
end
function Perimeter.check_frequency(self, event)
if event.record.span_contact_count >= self.contact_count_threshold then
self.log:info('[', event.key, '/', event.sequence, '] PERIMETER_FREQUENCY_CHECK - contacts: ', event.record.span_contact_count, ' in < ', (event.timestamp - event.record.span_start)/1000000, ' sec, threshold: ', self.contact_count_threshold, ' in ', self.contact_span_threshold, ' sec');
event.span_contact_count = 0;
event.span_start = event.timestamp;
return 1;
elseif (event.timestamp - event.record.span_start) > (self.contact_span_threshold * 1000000) then
event.span_contact_count = 0;
event.span_start = event.timestamp;
end
end
function Perimeter.check_username_scan(self, event)
if not event.to_user then
return;
end
if not event.record.users then
event.users = { event.to_user };
return;
end
if #event.record.users >= self.name_changes_threshold then
self.log:info('[', event.key, '/', event.sequence, '] PERIMETER_USER_SCAN - user names: ', #event.record.users, ', threshold: ', self.name_changes_threshold);
event.users = {};
return 1;
else
for index=1, #event.record.users do
if event.record.users[index] == tostring(event.to_user) then
return
end
end
if not event.users then
event.users = event.record.users or {};
end
table.insert(event.users, tostring(event.to_user));
end
end
function Perimeter.check_bad_headers(self, event)
local points = nil;
for name, pattern in pairs(self.bad_headers) do
local success, result = pcall(string.find, event[name], pattern);
if success and result then
self.log:info('[', event.key, '/', event.sequence, '] PERIMETER_BAD_HEADERS - ', name, '=', event[name], ' ~= ', pattern);
points = (points or 0) + 1;
end
end
return points;
end
function Perimeter.append_blacklist_file(self, event)
local blacklist = io.open(self.blacklist_file, 'a');
if not blacklist then
self.log:error('[', event.key, '/', event.sequence, '] PERIMETER_APPEND_BLACKLIST - could not open file: ', self.blacklist_file);
return false;
end
event.date = self:format_date(event.timestamp);
if self.blacklist_file_comment then
blacklist:write(self:expand_variables(self.blacklist_file_comment, event), '\n');
end
self.log:debug('[', event.key, '/', event.sequence, '] PERIMETER_APPEND_BLACKLIST - file: ', self.blacklist_file);
blacklist:write(self:expand_variables(self.blacklist_file_entry, event), '\n');
blacklist:close();
end
function Perimeter.execute_ban(self, event)
local command = self:expand_variables(self.ban_command, event);
self.log:debug('[', event.key, '/', event.sequence, '] PERIMETER_EXECUTE_BAN - command: ', command);
local result = os.execute(command);
end
function Perimeter.expand_variables(self, line, variables)
return (line:gsub('{([%a%d%._]+)}', function(captured)
return variables[captured] or '';
end))
end
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