ospd.ospd

Complexity

Total Complexity

212

Size/Duplication

Total Lines	1053
Duplicated Lines	0 %

Importance

Changes

0

62 Methods

Rating	Name	Duplication	Size	Complexity
A	OSPDaemon.get_scanner_name()	0	3	1
A	OSPDError.as_xml()	0	3	1
A	OSPDaemon.finish_scan()	0	4	1
F	OSPDaemon._preprocess_scan_params()	0	32	15
A	OSPDaemon.get_protocol_version()	0	3	1
A	OSPDaemon.get_scanner_param_mandatory()	0	7	3
A	OSPDaemon.get_scanner_description()	0	3	1
A	OSPDaemon.command_exists()	0	3	1
A	OSPDaemon.get_scanner_param_default()	0	7	3
A	OSPDaemon.get_daemon_name()	0	3	1
F	OSPDaemon.handle_start_scan_command()	0	38	9
A	OSPDError.__init__()	0	5	1
A	OSPDaemon.get_scanner_param_type()	0	7	3
B	OSPDaemon.handle_stop_scan_command()	0	23	5
A	OSPDaemon.exec_scan()	0	3	1
B	OSPDaemon.__init__()	0	29	2
A	OSPDaemon.add_scanner_param()	0	10	4
A	OSPDaemon.set_command_attributes()	0	5	2
A	OSPDaemon.get_server_version()	0	4	2
A	OSPDaemon.get_scanner_params_xml()	0	15	4
B	OSPDaemon.add_vt()	0	21	5
A	OSPDaemon.get_scanner_version()	0	3	1
A	OSPDaemon.process_scan_params()	0	4	1
A	OSPDaemon.get_daemon_version()	0	3	1
B	OSPDaemon.new_client_stream()	0	24	3
A	OSPDaemon.get_scan_options()	0	3	1
A	OSPDaemon.create_scan()	0	9	1
B	OSPDaemon.get_xml_str()	0	21	6
A	OSPDaemon.handle_get_version_command()	0	21	4
B	OSPDaemon.elements_as_text()	0	16	6
A	OSPDaemon.scan_exists()	0	6	1
A	OSPDaemon.get_custom_vt_as_xml_str()	0	12	1
A	OSPDaemon.add_scan_error()	0	4	1
A	OSPDaemon.get_scan_start_time()	0	3	1
A	OSPDaemon.add_scan_alarm()	0	5	1
A	OSPDaemon.handle_delete_scan_command()	0	17	4
A	OSPDaemon.dry_run_scan()	0	14	3
A	OSPDaemon.get_scan_progress()	0	3	1
A	OSPDaemon.get_vts_xml()	0	17	3
B	OSPDaemon.get_scan_xml()	0	22	4
C	OSPDaemon.handle_get_scans_command()	0	27	7
A	OSPDaemon.check()	0	3	1
A	OSPDaemon.set_scan_option()	0	3	1
A	OSPDaemon.handle_help_command()	0	14	4
A	OSPDaemon.add_scan_log()	0	5	1
D	OSPDaemon.start_scan()	0	33	8
A	OSPDaemon.get_scan_target()	0	3	1
A	OSPDaemon.get_scan_ports()	0	3	1
A	OSPDaemon.check_scan_process()	0	11	4
B	OSPDaemon.get_vt_xml()	0	23	4
A	OSPDaemon.delete_scan()	0	10	2
A	OSPDaemon.get_scan_end_time()	0	3	1
A	OSPDaemon.add_scan_host_detail()	0	4	1
B	OSPDaemon.handle_get_vts_command()	0	22	4
B	OSPDaemon.get_help_text()	0	16	5
A	OSPDaemon.set_scan_progress()	0	3	1
F	OSPDaemon.handle_client_stream()	0	42	12
A	OSPDaemon.handle_timeout()	0	5	1
A	OSPDaemon.get_scan_results_xml()	0	11	2
F	OSPDaemon.handle_command()	0	32	13
D	OSPDaemon.run()	0	30	8
A	OSPDaemon.handle_get_scanner_details()	0	12	1

# -*- coding: utf-8 -*-
# $Id$
# Description:
# OSP Daemon core class.
#
# Authors:
# Hani Benhabiles <hani.benhabiles@greenbone.net>
# Benoît Allard <benoit.allard@greenbone.net>
# Jan-Oliver Wahmer <jan-oliver.wagner@greenbone.net>
#
# Copyright:
# Copyright (C) 2014, 2015, 2018 Greenbone Networks GmbH
#
# 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 2
# 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, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

""" OSP Daemon core class. """

# This is needed for older pythons as our current module is called the same
# as the package we are in ...
# Another solution would be to rename that file.
from __future__ import absolute_import

import logging
import socket
import ssl
import multiprocessing
import xml.etree.ElementTree as ET
import os

from ospd import __version__
from ospd.misc import ScanCollection, ResultType, target_str_to_list
from ospd.misc import resolve_hostname, valid_uuid

logger = logging.getLogger(__name__)

PROTOCOL_VERSION = "1.2"

BASE_SCANNER_PARAMS = {
    'debug_mode': {
        'type': 'boolean',
        'name': 'Debug Mode',
        'default': 0,
        'mandatory': 0,
        'description': 'Whether to get extra scan debug information.',
    },
    'dry_run': {
        'type': 'boolean',
        'name': 'Dry Run',
        'default': 0,
        'mandatory': 0,
        'description': 'Whether to dry run scan.',
    },
}

COMMANDS_TABLE = {
    'start_scan': {
        'description': 'Start a new scan.',
        'attributes': {
            'target': 'Target host to scan',
            'ports': 'Ports list to scan',
            'scan_id': 'Optional UUID value to use as scan ID',
        },
        'elements': None
    },
    'stop_scan': {
        'description': 'Stop a currently running scan.',
        'attributes': {
            'scan_id': 'ID of scan to stop.'
        },
        'elements': None
    },
    'help': {
        'description': 'Print the commands help.',
        'attributes': {
            'format': 'Help format. Could be text or xml.'
        },
        'elements': None
    },
    'get_scans': {
        'description': 'List the scans in buffer.',
        'attributes': {
            'scan_id': 'ID of a specific scan to get.',
            'details': 'Whether to return the full scan report.'
        },
        'elements': None
    },
    'get_vts': {
        'description': 'List of available vulnerability tests.',
        'attributes': {
            'vt_id': 'ID of a specific vulnerability test to get.'
        },
        'elements': None
    },
    'delete_scan': {
        'description': 'Delete a finished scan.',
        'attributes': {
            'scan_id': 'ID of scan to delete.'
        },
        'elements': None
    },
    'get_version': {
        'description': 'Return various versions.',
        'attributes': None,
        'elements': None
    },
    'get_scanner_details': {
        'description': 'Return scanner description and parameters',
        'attributes': None,
        'elements': None
    }
}


def get_result_xml(result):
    """ Formats a scan result to XML format. """
    result_xml = ET.Element('result')
    for name, value in [('name', result['name']),
                        ('type', ResultType.get_str(result['type'])),
                        ('severity', result['severity']),
                        ('host', result['host']),
                        ('test_id', result['test_id']),
                        ('port', result['port']),
                        ('qod', result['qod'])]:
        result_xml.set(name, str(value))
    result_xml.text = result['value']
    return result_xml


def simple_response_str(command, status, status_text, content=""):
    """ Creates an OSP response XML string.

    @param: OSP Command to respond to.
    @param: Status of the response.
    @param: Status text of the response.
    @param: Text part of the response XML element.

    @return: String of response in xml format.
    """
    response = ET.Element('%s_response' % command)
    for name, value in [('status', str(status)), ('status_text', status_text)]:
        response.set(name, str(value))
    if isinstance(content, list):
        for elem in content:
            response.append(elem)
    elif isinstance(content, ET.Element):
        response.append(content)
    else:
        response.text = content
    return ET.tostring(response)


class OSPDError(Exception):

    """ This is an exception that will result in an error message to the
    client """

    def __init__(self, message, command='osp', status=400):
        super(OSPDError, self).__init__()
        self.message = message
        self.command = command
        self.status = status

    def as_xml(self):
        """ Return the error in xml format. """
        return simple_response_str(self.command, self.status, self.message)


def bind_socket(address, port):
    """ Returns a socket bound on (address:port). """

    assert address
    assert port
    bindsocket = socket.socket()
    try:
        bindsocket.bind((address, port))
    except socket.error:
        logger.error("Couldn't bind socket on {0}:{1}"
                     .format(address, port))
        return None

    logger.info('Listening on {0}:{1}'.format(address, port))
    bindsocket.listen(0)
    return bindsocket

def bind_unix_socket(path):
    """ Returns a unix file socket bound on (path). """

    assert path
    bindsocket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
    try:
        os.unlink(path)
    except OSError:
        if os.path.exists(path):
            raise
    try:
        bindsocket.bind(path)
    except socket.error:
        logger.error("Couldn't bind socket on {0}".format(path))
        return None

    logger.info('Listening on {0}'.format(path))
    bindsocket.listen(0)
    return bindsocket


def close_client_stream(client_stream, unix_path):
    """ Closes provided client stream """
    try:
        client_stream.shutdown(socket.SHUT_RDWR)
        if unix_path:
            logger.debug('{0}: Connection closed'.format(unix_path))
        else:
            peer = client_stream.getpeername()
            logger.debug('{0}:{1}: Connection closed'.format(peer[0], peer[1]))
    except (socket.error, OSError) as exception:
        logger.debug('Connection closing error: {0}'.format(exception))
    client_stream.close()


class OSPDaemon(object):

    """ Daemon class for OSP traffic handling.

    Every scanner wrapper should subclass it and make necessary additions and
    changes.
    * Add any needed parameters in __init__.
    * Implement check() method which verifies scanner availability and other
      environment related conditions.
    * Implement process_scan_params and exec_scan methods which are
      specific to handling the <start_scan> command, executing the wrapped
      scanner and storing the results.
    * exec_scan() should return 0 if host is dead or not reached, 1 if host is
      alive and 2 if scan error or status is unknown.
    * Implement other methods that assert to False such as get_scanner_name,
      get_scanner_version.
    * Use Call set_command_attributes at init time to add scanner command
      specific options eg. the w3af profile for w3af wrapper.
    """

    def __init__(self, certfile, keyfile, cafile):
        """ Initializes the daemon's internal data. """
        # @todo: Actually it makes sense to move the certificate params to
        #        a separate function because it is not mandatory anymore to
        #        use a TLS setup (unix file socket is an alternative).
        #        However, changing this makes it mandatory for any ospd scanner
        #        to change the function calls as well. So this breaks the API
        #        and should only be done with a major release.
        self.certs = dict()
        self.certs['cert_file'] = certfile
        self.certs['key_file'] = keyfile
        self.certs['ca_file'] = cafile
        self.scan_collection = ScanCollection()
        self.scan_processes = dict()
        self.daemon_info = dict()
        self.daemon_info['name'] = "OSPd"
        self.daemon_info['version'] = __version__
        self.daemon_info['description'] = "No description"
        self.scanner_info = dict()
        self.scanner_info['name'] = 'No name'
        self.scanner_info['version'] = 'No version'
        self.scanner_info['description'] = 'No description'
        self.server_version = None  # Set by the subclass.
        self.protocol_version = PROTOCOL_VERSION
        self.commands = COMMANDS_TABLE
        self.scanner_params = dict()
        self.vts = dict()
        for name, param in BASE_SCANNER_PARAMS.items():
            self.add_scanner_param(name, param)

    def set_command_attributes(self, name, attributes):
        """ Sets the xml attributes of a specified command. """
        if self.command_exists(name):
            command = self.commands.get(name)
            command['attributes'] = attributes

    def add_scanner_param(self, name, scanner_param):
        """ Add a scanner parameter. """

        assert name
        assert scanner_param
        self.scanner_params[name] = scanner_param
        command = self.commands.get('start_scan')
        command['elements'] = {
            'scanner_params':
                {k: v['name'] for k, v in self.scanner_params.items()}}

    def add_vt(self, vt_id, name='', custom=None):
        """ Add a vulnerability test information.

        Returns: The new number of stored VTs.
        -1 in case the VT ID was already present and thus the
        new VT was not considered.
        -2 in case the vt_id was invalid.
        """

        if not vt_id:
            return -2 # no valid vt_id

        if vt_id in self.vts:
            return -1 # The VT was already in the list.

        if vt_id and custom is not None:
            self.vts[vt_id] = { 'name': name, 'custom': custom }
        else:
            self.vts[vt_id] = { 'name': name }

        return len(self.vts)

    def command_exists(self, name):
        """ Checks if a commands exists. """
        return name in self.commands.keys()

    def get_scanner_name(self):
        """ Gives the wrapped scanner's name. """
        return self.scanner_info['name']

    def get_scanner_version(self):
        """ Gives the wrapped scanner's version. """
        return self.scanner_info['version']

    def get_scanner_description(self):
        """ Gives the wrapped scanner's description. """
        return self.scanner_info['description']

    def get_server_version(self):
        """ Gives the specific OSP server's version. """
        assert self.server_version
        return self.server_version

    def get_protocol_version(self):
        """ Gives the OSP's version. """
        return self.protocol_version

    def _preprocess_scan_params(self, xml_params):
        """ Processes the scan parameters. """
        params = {}
        for param in xml_params:
            params[param.tag] = param.text or ''
        # Set default values.
        for key in self.scanner_params:
            if key not in params:
                params[key] = self.get_scanner_param_default(key)
                if self.get_scanner_param_type(key) == 'selection':
                    params[key] = params[key].split('|')[0]
        # Validate values.
        for key in params:
            param_type = self.get_scanner_param_type(key)
            if not param_type:
                continue
            if param_type in ['integer', 'boolean']:
                try:
                    params[key] = int(params[key])
                except ValueError:
                    raise OSPDError('Invalid %s value' % key, 'start_scan')
            if param_type == 'boolean':
                if params[key] not in [0, 1]:
                    raise OSPDError('Invalid %s value' % key, 'start_scan')
            elif param_type == 'selection':
                selection = self.get_scanner_param_default(key).split('|')
                if params[key] not in selection:
                    raise OSPDError('Invalid %s value' % key, 'start_scan')
            if self.get_scanner_param_mandatory(key) and params[key] == '':
                    raise OSPDError('Mandatory %s value is missing' % key,
                                    'start_scan')
        return params

    def process_scan_params(self, params):
        """ This method is to be overridden by the child classes if necessary
        """
        return params

    def handle_start_scan_command(self, scan_et):
        """ Handles <start_scan> command.

        @return: Response string for <start_scan> command.
        """

        target_str = scan_et.attrib.get('target')
        if target_str is None:
            raise OSPDError('No target attribute', 'start_scan')
        ports_str = scan_et.attrib.get('ports')
        if ports_str is None:
            raise OSPDError('No ports attribute', 'start_scan')
        scan_id = scan_et.attrib.get('scan_id')
        if scan_id is not None and scan_id != '' and not valid_uuid(scan_id):
            raise OSPDError('Invalid scan_id UUID', 'start_scan')

        scanner_params = scan_et.find('scanner_params')
        if scanner_params is None:
            raise OSPDError('No scanner_params element', 'start_scan')

        params = self._preprocess_scan_params(scanner_params)

        # Dry run case.
        if 'dry_run' in params and int(params['dry_run']):
            scan_func = self.dry_run_scan
            scan_params = None
        else:
            scan_func = self.start_scan
            scan_params = self.process_scan_params(params)

        scan_id = self.create_scan(scan_id, target_str, ports_str, scan_params)
        scan_process = multiprocessing.Process(target=scan_func,
                                               args=(scan_id, target_str))
        self.scan_processes[scan_id] = scan_process
        scan_process.start()
        id_ = ET.Element('id')
        id_.text = scan_id
        return simple_response_str('start_scan', 200, 'OK', id_)

    def handle_stop_scan_command(self, scan_et):
        """ Handles <stop_scan> command.

        @return: Response string for <stop_scan> command.
        """

        scan_id = scan_et.attrib.get('scan_id')
        if scan_id is None or scan_id == '':
            raise OSPDError('No scan_id attribute', 'stop_scan')
        scan_process = self.scan_processes.get(scan_id)
        if not scan_process:
            raise OSPDError('Scan not found {0}.'.format(scan_id), 'stop_scan')
        if not scan_process.is_alive():
            raise OSPDError('Scan already stopped or finished.', 'stop_scan')

        logger.info('{0}: Scan stopping {1}.'.format(scan_id, scan_process.ident))
        scan_process.terminate()
        os.killpg(os.getpgid(scan_process.ident), 15)
        scan_process.join()
        self.set_scan_progress(scan_id, 100)
        self.add_scan_log(scan_id, name='', host='', value='Scan stopped.')
        logger.info('{0}: Scan stopped.'.format(scan_id))
        return simple_response_str('stop_scan', 200, 'OK')

    def exec_scan(self, scan_id, target):
        """ Asserts to False. Should be implemented by subclass. """
        raise NotImplementedError

    def finish_scan(self, scan_id):
        """ Sets a scan as finished. """
        self.set_scan_progress(scan_id, 100)
        logger.info("{0}: Scan finished.".format(scan_id))

    def get_daemon_name(self):
        """ Gives osp daemon's name. """
        return self.daemon_info['name']

    def get_daemon_version(self):
        """ Gives osp daemon's version. """
        return self.daemon_info['version']

    def get_scanner_param_type(self, param):
        """ Returns type of a scanner parameter. """
        assert isinstance(param, str)
        entry = self.scanner_params.get(param)
        if not entry:
            return None
        return entry.get('type')

    def get_scanner_param_mandatory(self, param):
        """ Returns if a scanner parameter is mandatory. """
        assert isinstance(param, str)
        entry = self.scanner_params.get(param)
        if not entry:
            return False
        return entry.get('mandatory')

    def get_scanner_param_default(self, param):
        """ Returns default value of a scanner parameter. """
        assert isinstance(param, str)
        entry = self.scanner_params.get(param)
        if not entry:
            return None
        return entry.get('default')

    def get_scanner_params_xml(self):
        """ Returns the OSP Daemon's scanner params in xml format. """
        scanner_params = ET.Element('scanner_params')
        for param_id, param in self.scanner_params.items():
            param_xml = ET.SubElement(scanner_params, 'scanner_param')
            for name, value in [('id', param_id),
                                ('type', param['type'])]:
                param_xml.set(name, value)
            for name, value in [('name', param['name']),
                                ('description', param['description']),
                                ('default', param['default']),
                                ('mandatory', param['mandatory'])]:
                elem = ET.SubElement(param_xml, name)
                elem.text = str(value)
        return scanner_params

    def new_client_stream(self, sock):
        """ Returns a new ssl client stream from bind_socket. """

        assert sock
        newsocket, fromaddr = sock.accept()
        logger.debug("New connection from"
                     " {0}:{1}".format(fromaddr[0], fromaddr[1]))
        # NB: Despite the name, ssl.PROTOCOL_SSLv23 selects the highest
        # protocol version that both the client and server support. In modern
        # Python versions (>= 3.4) it suppports TLS >= 1.0 with SSLv2 and SSLv3
        # being disabled. For Python >=3.5, PROTOCOL_SSLv23 is an alias for
        # PROTOCOL_TLS which should be used once compatibility with Python 3.4
        # is no longer desired.
        try:
            ssl_socket = ssl.wrap_socket(newsocket, cert_reqs=ssl.CERT_REQUIRED,
                                         server_side=True,
                                         certfile=self.certs['cert_file'],
                                         keyfile=self.certs['key_file'],
                                         ca_certs=self.certs['ca_file'],
                                         ssl_version=ssl.PROTOCOL_SSLv23)
        except (ssl.SSLError, socket.error) as message:
            logger.error(message)
            return None
        return ssl_socket

    def handle_client_stream(self, stream, is_unix=False):
        """ Handles stream of data received from client. """

        assert stream
        data = []
        stream.settimeout(2)
        while True:
            try:
                if is_unix:
                    data.append(stream.recv(1024))
                else:
                    data.append(stream.read(1024))
                if len(data) == 0:
                    logger.warning(
                        "Empty client stream (Connection unexpectedly closed)")
                    return
            except (AttributeError, ValueError) as message:
                logger.error(message)
                return
            except (ssl.SSLError) as exception:
                logger.debug('Error: {0}'.format(exception[0]))
                break
            except (socket.timeout) as exception:
                logger.debug('Error: {0}'.format(exception))
                break
        data = b''.join(data)
        if len(data) <= 0:
            logger.debug("Empty client stream")
            return
        try:
            response = self.handle_command(data)
        except OSPDError as exception:
            response = exception.as_xml()
            logger.debug('Command error: {0}'.format(exception.message))
        except Exception:
            logger.exception('While handling client command:')
            exception = OSPDError('Fatal error', 'error')
            response = exception.as_xml()
        if is_unix:
            stream.sendall(response)
        else:
            stream.write(response)

    def start_scan(self, scan_id, target_str):
        """ Starts the scan with scan_id. """

        os.setsid()
        logger.info("{0}: Scan started.".format(scan_id))
        target_list = target_str_to_list(target_str)
        if target_list is None:
            raise OSPDError('Erroneous targets list', 'start_scan')
        for index, target in enumerate(target_list):
            progress = float(index) * 100 / len(target_list)
            self.set_scan_progress(scan_id, int(progress))
            logger.info("{0}: Host scan started.".format(target))
            try:
                ret = self.exec_scan(scan_id, target)
                if ret == 0:
                    self.add_scan_host_detail(scan_id, name='host_status',
                                              host=target, value='0')
                elif ret == 1:
                    self.add_scan_host_detail(scan_id, name='host_status',
                                              host=target, value='1')
                elif ret == 2:
                    self.add_scan_host_detail(scan_id, name='host_status',
                                              host=target, value='2')
                else:
                    logger.debug('{0}: No host status returned'.format(target))
            except Exception as e:
                self.add_scan_error(scan_id, name='', host=target,
                                    value='Host process failure (%s).' % e)
                logger.exception('While scanning {0}:'.format(target))
            else:
                logger.info("{0}: Host scan finished.".format(target))

        self.finish_scan(scan_id)

    def dry_run_scan(self, scan_id, target_str):
        """ Dry runs a scan. """

        os.setsid()
        target_list = target_str_to_list(target_str)
        for _, target in enumerate(target_list):
            host = resolve_hostname(target)
            if host is None:
                logger.info("Couldn't resolve {0}.".format(target))
                continue
            logger.info("{0}: Dry run mode.".format(host))
            self.add_scan_log(scan_id, name='', host=host,
                              value='Dry run result')
        self.finish_scan(scan_id)

    def handle_timeout(self, scan_id, host):
        """ Handles scanner reaching timeout error. """
        self.add_scan_error(scan_id, host=host, name="Timeout",
                            value="{0} exec timeout."
                            .format(self.get_scanner_name()))

    def set_scan_progress(self, scan_id, progress):
        """ Sets scan_id scan's progress which is a number between 0 and 100. """
        self.scan_collection.set_progress(scan_id, progress)

    def scan_exists(self, scan_id):
        """ Checks if a scan with ID scan_id is in collection.

        @return: 1 if scan exists, 0 otherwise.
        """
        return self.scan_collection.id_exists(scan_id)

    def handle_get_scans_command(self, scan_et):
        """ Handles <get_scans> command.

        @return: Response string for <get_scans> command.
        """

        scan_id = scan_et.attrib.get('scan_id')
        details = scan_et.attrib.get('details')
        if details and details == '0':
            details = False
        else:
            details = True

        responses = []
        if scan_id and scan_id in self.scan_collection.ids_iterator():
            self.check_scan_process(scan_id)
            scan = self.get_scan_xml(scan_id, details)
            responses.append(scan)
        elif scan_id:
            text = "Failed to find scan '{0}'".format(scan_id)
            return simple_response_str('get_scans', 404, text)
        else:
            for scan_id in self.scan_collection.ids_iterator():
                self.check_scan_process(scan_id)
                scan = self.get_scan_xml(scan_id, details)
                responses.append(scan)
        return simple_response_str('get_scans', 200, 'OK', responses)

    def handle_get_vts_command(self, vt_et):
        """ Handles <get_vts> command.

        @return: Response string for <get_vts> command.
        """

        vt_id = vt_et.attrib.get('vt_id')

        if vt_id and vt_id not in self.vts:
            text = "Failed to find vulnerability test '{0}'".format(vt_id)
            return simple_response_str('get_vts', 404, text)

        responses = []

        if vt_id:
            vts_xml = self.get_vts_xml(vt_id)
        else:
            vts_xml = self.get_vts_xml()

        responses.append(vts_xml)

        return simple_response_str('get_vts', 200, 'OK', responses)

    def handle_help_command(self, scan_et):
        """ Handles <help> command.

        @return: Response string for <help> command.
        """
        help_format = scan_et.attrib.get('format')
        if help_format is None or help_format == "text":
            # Default help format is text.
            return simple_response_str('help', 200, 'OK',
                                       self.get_help_text())
        elif help_format == "xml":
            text = self.get_xml_str(self.commands)
            return simple_response_str('help', 200, 'OK', text)
        raise OSPDError('Bogus help format', 'help')

    def get_help_text(self):
        """ Returns the help output in plain text format."""

        txt = str('\n')
        for name, info in self.commands.items():
            command_txt = "\t{0: <22} {1}\n".format(name, info['description'])
            if info['attributes']:
                command_txt = ''.join([command_txt, "\t Attributes:\n"])
                for attrname, attrdesc in info['attributes'].items():
                    attr_txt = "\t  {0: <22} {1}\n".format(attrname, attrdesc)
                    command_txt = ''.join([command_txt, attr_txt])
            if info['elements']:
                command_txt = ''.join([command_txt, "\t Elements:\n",
                                       self.elements_as_text(info['elements'])])
            txt = ''.join([txt, command_txt])
        return txt

    def elements_as_text(self, elems, indent=2):
        """ Returns the elems dictionary as formatted plain text. """
        assert elems
        text = ""
        for elename, eledesc in elems.items():
            if isinstance(eledesc, dict):
                desc_txt = self.elements_as_text(eledesc, indent + 2)
                desc_txt = ''.join(['\n', desc_txt])
            elif isinstance(eledesc, str):
                desc_txt = ''.join([eledesc, '\n'])
            else:
                assert False, "Only string or dictionary"
            ele_txt = "\t{0}{1: <22} {2}".format(' ' * indent, elename,
                                                 desc_txt)

The variable desc_txt does not seem to be defined for all execution paths.

            text = ''.join([text, ele_txt])
        return text

    def handle_delete_scan_command(self, scan_et):
        """ Handles <delete_scan> command.

        @return: Response string for <delete_scan> command.
        """
        scan_id = scan_et.attrib.get('scan_id')
        if scan_id is None:
            return simple_response_str('delete_scan', 404,
                                       'No scan_id attribute')

        if not self.scan_exists(scan_id):
            text = "Failed to find scan '{0}'".format(scan_id)
            return simple_response_str('delete_scan', 404, text)
        self.check_scan_process(scan_id)
        if self.delete_scan(scan_id):
            return simple_response_str('delete_scan', 200, 'OK')
        raise OSPDError('Scan in progress', 'delete_scan')

    def delete_scan(self, scan_id):
        """ Deletes scan_id scan from collection.

        @return: 1 if scan deleted, 0 otherwise.
        """
        try:
            del self.scan_processes[scan_id]
        except KeyError:
            logger.debug('Scan process for {0} not found'.format(scan_id))
        return self.scan_collection.delete_scan(scan_id)

    def get_scan_results_xml(self, scan_id):
        """ Gets scan_id scan's results in XML format.

        @return: String of scan results in xml.
        """
        results = ET.Element('results')
        for result in self.scan_collection.results_iterator(scan_id):
            results.append(get_result_xml(result))

        logger.info('Returning %d results', len(results))
        return results

    def get_xml_str(self, data):
        """ Creates a string in XML Format using the provided data structure.

        @param: Dictionary of xml tags and their elements.

        @return: String of data in xml format.
        """

        responses = []
        for tag, value in data.items():
            elem = ET.Element(tag)
            if isinstance(value, dict):
                for value in self.get_xml_str(value):
                    elem.append(value)
            elif isinstance(value, list):
                value = ', '.join([m for m in value])
                elem.text = value
            else:
                elem.text = value
            responses.append(elem)
        return responses

    def get_scan_xml(self, scan_id, detailed=True):
        """ Gets scan in XML format.

        @return: String of scan in XML format.
        """
        if not scan_id:
            return ET.Element('scan')

        target = self.get_scan_target(scan_id)
        progress = self.get_scan_progress(scan_id)
        start_time = self.get_scan_start_time(scan_id)
        end_time = self.get_scan_end_time(scan_id)
        response = ET.Element('scan')
        for name, value in [('id', scan_id),
                            ('target', target),
                            ('progress', progress),
                            ('start_time', start_time),
                            ('end_time', end_time)]:
            response.set(name, str(value))
        if detailed:
            response.append(self.get_scan_results_xml(scan_id))
        return response

    def get_custom_vt_as_xml_str(self, custom):
        """ Create a string representation of the XML object from the
        custom data object.
        This needs to be implemented by each ospd wrapper, in case
        custom elements for VTs are used.

        The custom XML object which is returned will be embedded
        into a <custom></custom> element.

        @return: XML object as string for custom data.
        """
        return ''

    def get_vt_xml(self, vt_id):
        """ Gets a single vulnerability test information in XML format.

        @return: String of single vulnerability test information in XML format.
        """
        if not vt_id:
            return ET.Element('vt')

        vt = self.vts.get(vt_id)

        name = vt.get('name')
        vt_xml = ET.Element('vt')
        vt_xml.set('id', vt_id)

        for name, value in [('name', name)]:
            elem = ET.SubElement(vt_xml, name)
            elem.text = str(value)

        if vt.get('custom'):
            custom_xml_str = '<custom>%s</custom>' % self.get_custom_vt_as_xml_str(vt.get('custom'))
            vt_xml.append(ET.fromstring(custom_xml_str))

        return vt_xml

    def get_vts_xml(self, vt_id=''):
        """ Gets collection of vulnerability test information in XML format.
        If vt_id is specified, the collection will contain only this vt, of found.
        If no vt_id is specified, the collection will contain all vts.

        @return: String of collection of vulnerability test information in XML format.
        """

        vts_xml = ET.Element('vts')

        if vt_id != '':
            vts_xml.append(self.get_vt_xml(vt_id))
        else:
            for vt_id in self.vts:
                vts_xml.append(self.get_vt_xml(vt_id))

        return vts_xml

    def handle_get_scanner_details(self):
        """ Handles <get_scanner_details> command.

        @return: Response string for <get_scanner_details> command.
        """
        desc_xml = ET.Element('description')
        desc_xml.text = self.get_scanner_description()
        details = [
            desc_xml,
            self.get_scanner_params_xml()
        ]
        return simple_response_str('get_scanner_details', 200, 'OK', details)

    def handle_get_version_command(self):
        """ Handles <get_version> command.

        @return: Response string for <get_version> command.
        """
        protocol = ET.Element('protocol')
        for name, value in [('name', 'OSP'), ('version', self.get_protocol_version())]:
            elem = ET.SubElement(protocol, name)
            elem.text = value

        daemon = ET.Element('daemon')
        for name, value in [('name', self.get_daemon_name()), ('version', self.get_daemon_version())]:
            elem = ET.SubElement(daemon, name)
            elem.text = value

        scanner = ET.Element('scanner')
        for name, value in [('name', self.get_scanner_name()), ('version', self.get_scanner_version())]:
            elem = ET.SubElement(scanner, name)
            elem.text = value

        return simple_response_str('get_version', 200, 'OK', [protocol, daemon, scanner])

    def handle_command(self, command):
        """ Handles an osp command in a string.

        @return: OSP Response to command.
        """
        try:
            tree = ET.fromstring(command)
        except ET.ParseError:
            logger.debug("Erroneous client input: {0}".format(command))
            raise OSPDError('Invalid data')

        if not self.command_exists(tree.tag) and tree.tag != "authenticate":
            raise OSPDError('Bogus command name')

        if tree.tag == "get_version":
            return self.handle_get_version_command()
        elif tree.tag == "start_scan":
            return self.handle_start_scan_command(tree)
        elif tree.tag == "stop_scan":
            return self.handle_stop_scan_command(tree)
        elif tree.tag == "get_scans":
            return self.handle_get_scans_command(tree)
        elif tree.tag == "get_vts":
            return self.handle_get_vts_command(tree)
        elif tree.tag == "delete_scan":
            return self.handle_delete_scan_command(tree)
        elif tree.tag == "help":
            return self.handle_help_command(tree)
        elif tree.tag == "get_scanner_details":
            return self.handle_get_scanner_details()
        else:
            assert False, "Unhandled command: {0}".format(tree.tag)

    def check(self):
        """ Asserts to False. Should be implemented by subclass. """
        raise NotImplementedError

    def run(self, address, port, unix_path):
        """ Starts the Daemon, handling commands until interrupted.

        @return False if error. Runs indefinitely otherwise.
        """
        assert address or unix_path
        if unix_path:
            sock = bind_unix_socket(unix_path)
        else:
            sock = bind_socket(address, port)
        if sock is None:
            return False

        try:
            while True:
                if unix_path:
                    client_stream, _ = sock.accept()
                    logger.debug("New connection from {0}".format(unix_path))
                    self.handle_client_stream(client_stream, True)
                else:
                    client_stream = self.new_client_stream(sock)
                    if client_stream is None:
                        continue
                    self.handle_client_stream(client_stream, False)
                close_client_stream(client_stream, unix_path)
        except KeyboardInterrupt:
            logger.info("Received Ctrl-C shutting-down ...")
        finally:
            sock.shutdown(socket.SHUT_RDWR)
            sock.close()

    def create_scan(self, scan_id, target, ports, options):
        """ Creates a new scan.

        @target: Target to scan.
        @options: Miscellaneous scan options.

        @return: New scan's ID.
        """
        return self.scan_collection.create_scan(scan_id, target, ports, options)

    def get_scan_options(self, scan_id):
        """ Gives a scan's list of options. """
        return self.scan_collection.get_options(scan_id)

    def set_scan_option(self, scan_id, name, value):
        """ Sets a scan's option to a provided value. """
        return self.scan_collection.set_option(scan_id, name, value)

    def check_scan_process(self, scan_id):
        """ Check the scan's process, and terminate the scan if not alive. """
        scan_process = self.scan_processes[scan_id]
        progress = self.get_scan_progress(scan_id)
        if progress < 100 and not scan_process.is_alive():
            self.set_scan_progress(scan_id, 100)
            self.add_scan_error(scan_id, name="", host="",
                                value="Scan process failure.")
            logger.info("{0}: Scan terminated.".format(scan_id))
        elif progress == 100:
            scan_process.join()

    def get_scan_progress(self, scan_id):
        """ Gives a scan's current progress value. """
        return self.scan_collection.get_progress(scan_id)

    def get_scan_target(self, scan_id):
        """ Gives a scan's target. """
        return self.scan_collection.get_target(scan_id)

    def get_scan_ports(self, scan_id):
        """ Gives a scan's ports list. """
        return self.scan_collection.get_ports(scan_id)

    def get_scan_start_time(self, scan_id):
        """ Gives a scan's start time. """
        return self.scan_collection.get_start_time(scan_id)

    def get_scan_end_time(self, scan_id):
        """ Gives a scan's end time. """
        return self.scan_collection.get_end_time(scan_id)

    def add_scan_log(self, scan_id, host='', name='', value='', port='',
                     test_id='', qod=''):
        """ Adds a log result to scan_id scan. """
        self.scan_collection.add_result(scan_id, ResultType.LOG, host, name,
                                        value, port, test_id, 0.0, qod)

    def add_scan_error(self, scan_id, host='', name='', value='', port=''):
        """ Adds an error result to scan_id scan. """
        self.scan_collection.add_result(scan_id, ResultType.ERROR, host, name,
                                        value, port)

    def add_scan_host_detail(self, scan_id, host='', name='', value=''):
        """ Adds a host detail result to scan_id scan. """
        self.scan_collection.add_result(scan_id, ResultType.HOST_DETAIL, host,
                                        name, value)

    def add_scan_alarm(self, scan_id, host='', name='', value='', port='',
                       test_id='', severity='', qod=''):
        """ Adds an alarm result to scan_id scan. """
        self.scan_collection.add_result(scan_id, ResultType.ALARM, host, name,
                                        value, port, test_id, severity, qod)