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#!/usr/bin/python3
# Module containing classes, variables, etc. for creating OVAL content
#
# Author: David Ries <ries@jovalcm.com>
# Copyright (C) 2015 Farnam Hall Ventures LLC
#
# This script is distributed under the terms and conditions of the GNU General
# Public License, Version 2 or later. See http://www.gnu.org/copyleft/gpl.html
# for details.
#
# NOTES / TODOs
# This script creates OVAL ids based on the related CVE ID but does not
# currently increment the version number of generated elements when they
# change.
import datetime
import os
import random
import re
import shutil
import sys
import tempfile
from xml.sax.saxutils import escape
def recursive_rm(dirPath):
'''recursively remove directory'''
names = os.listdir(dirPath)
for name in names:
path = os.path.join(dirPath, name)
if not os.path.isdir(path):
os.unlink(path)
else:
recursive_rm(path)
os.rmdir(dirPath)
class OvalGenerator:
supported_oval_elements = ('definition', 'test', 'object', 'state',
'variable')
generator_version = 1
oval_schema_version = '5.11.1'
def __init__(self, release_codename, warn_method=False, outdir='./'):
""" constructor, set defaults for instances """
self.release_codename = release_codename
self.warn = warn_method or self.warn
self.tmpdir = tempfile.mkdtemp(prefix='oval_lib-')
self.output_dir = outdir
self.output_filepath = \
'com.ubuntu.{0}.cve.oval.xml'.format(self.release_codename)
self.ns = 'oval:com.ubuntu.{0}'.format(self.release_codename)
def __del__(self):
""" deconstructor, clean up """
if os.path.exists(self.tmpdir):
recursive_rm(self.tmpdir)
def generate_cve_definition(self, cve):
""" generate an OVAL definition based on parsed CVE data """
header = cve['header']
id_base = int(re.sub('[^0-9]', '', header['Candidate'])) * 100
if not self.unique_id_base(id_base, header['Source-note']):
self.warn('Calculated id_base "{0}" based on candidate value "{1}" is not unique. Skipping CVE.'.format(id_base, header['Candidate']))
# make test(s) for each package
test_refs = []
packages = cve['packages']
for package in sorted(packages.keys()):
releases = packages[package]['Releases']
for release in sorted(releases.keys()):
if release == self.release_codename:
release_status = releases[release]
test_ref = self.get_oval_test_for_package({
'name': package,
'status': release_status['status'],
'note': release_status['note'],
'fix-version': release_status['fix-version'] if 'fix-version' in release_status else '',
'id_base': id_base + len(test_refs),
'source-note': header['Source-note']
})
if test_ref:
test_refs.append(test_ref)
# if no packages for this release, then we're done
if not len(test_refs):
return False
# convert CVE data to OVAL definition metadata
mapping = {
'ns': escape(self.ns),
'id_base': id_base,
'codename': escape(self.release_codename),
'release_version': escape(self.release_version),
'applicability_def_id': escape(
self.release_applicability_definition_id),
'cve_title': escape(header['Candidate']),
'description': escape('{0} {1}'.format(header['Description'],
header['Ubuntu-Description']).strip()),
'priority': escape(header['Priority']),
'criteria': '',
'references': '',
'notes': ''
}
# convert test_refs to criteria
if len(test_refs) == 1:
negation_attribute = 'negate = "true" ' \
if 'negate' in test_refs[0] and test_refs[0]['negate'] else ''
mapping['criteria'] = \
'<criterion test_ref="{0}" comment="{1}" {2}/>'.format(
test_refs[0]['id'], escape(test_refs[0]['comment']), negation_attribute)
else:
criteria = []
criteria.append('<criteria operator="OR">')
for test_ref in test_refs:
negation_attribute = 'negate = "true" ' \
if 'negate' in test_ref and test_ref['negate'] else ''
criteria.append(
' ' +
'<criterion test_ref="{0}" comment="{1}" {2}/>'.format(
test_ref['id'],
escape(test_ref['comment']), negation_attribute))
criteria.append('</criteria>')
mapping['criteria'] = '\n '.join(criteria)
# convert notes
if header['Notes']:
mapping['notes'] = '\n <oval:notes>' + \
'\n <oval:note>{0}</oval:note>'.format(escape(header['Notes'])) + \
'\n </oval:notes>'
# convert additional data <advisory> metadata elements
advisory = []
advisory.append('<severity>{0}</severity>'.format(
escape(header['Priority'].title())))
advisory.append(
'<rights>Copyright (C) {0}Canonical Ltd.</rights>'.format(escape(
header['PublicDate'].split('-', 1)[0] + ' '
if header['PublicDate'] else '')))
if header['PublicDate']:
advisory.append('<public_date>{0}</public_date>'.format(
escape(header['PublicDate'])))
if header['PublicDateAtUSN']:
advisory.append(
'<public_date_at_usn>{0}</public_date_at_usn>'.format(escape(
header['PublicDateAtUSN'])))
if header['Assigned-to']:
advisory.append('<assigned_to>{0}</assigned_to>'.format(escape(
header['Assigned-to'])))
if header['Discovered-by']:
advisory.append('<discovered_by>{0}</discovered_by>'.format(escape(
header['Discovered-by'])))
if header['CRD']:
advisory.append('<crd>{0}</crd>'.format(escape(header['CRD'])))
for bug in header['Bugs']:
advisory.append('<bug>{0}</bug>'.format(escape(bug)))
for ref in header['References']:
if ref.startswith('https://cve.mitre'):
cve_title = ref.split('=')[-1].strip()
if not cve_title:
continue
mapping['cve_title'] = escape(cve_title)
mapping['references'] = '\n <reference source="CVE" ref_id="{0}" ref_url="{1}" />'.format(mapping['cve_title'], escape(ref))
else:
advisory.append('<ref>{0}</ref>'.format(escape(ref)))
mapping['advisory_elements'] = '\n '.join(advisory)
self.queue_element('definition', """
<definition class="vulnerability" id="{ns}:def:{id_base}0" version="1">
<metadata>
<title>{cve_title} on Ubuntu {release_version} ({codename}) - {priority}.</title>
<description>{description}</description>
<affected family="unix">
<platform>Ubuntu {release_version}</platform>
</affected>{references}
<advisory>
{advisory_elements}
</advisory>
</metadata>{notes}
<criteria>
<extend_definition definition_ref="{applicability_def_id}" comment="Ubuntu {release_version} ({codename}) is installed." applicability_check="true" />
{criteria}
</criteria>
</definition>
""".format(**mapping))
def get_oval_test_for_package(self, package):
""" create OVAL test and dependent objects for this package status
@package = {
'name' : '<package name>',
'status' : '<not-applicable | unknown | vulnerable | fixed>',
'note' : '<a description of the status>',
'fix-version' : '<the version in which the issue was fixed, if applicable>',
'id_base' : a base for the integer section of the OVAL id,
'source-note' : a note about the datasource for debugging
}
"""
if package['status'] == 'fixed' and not package['fix-version']:
self.warn('"{0}" package in {1} is marked fixed, but missing a fix-version. Changing status to unknown.'.format(package['name'], package['source-note']))
package['status'] = 'unknown'
if package['status'] == 'not-applicable':
# if the package status is not-applicable, skip it!
return False
elif package['status'] == 'not-vulnerable':
object_id = self.get_package_object_id(package['name'],
package['id_base'], 1)
test_id = '{0}:tst:{1}0'.format(self.ns, package['id_base'])
self.queue_element('test', """
<linux-def:dpkginfo_test id="{0}" version="{1}" check_existence="any_exist" check="all" comment="Returns true whether or not the '{2}' package exists.">
<linux-def:object object_ref="{3}"/>
</linux-def:dpkginfo_test>
""".format(test_id, 1, package['name'], object_id))
return {'id': test_id, 'comment': package['note'], 'negate': True}
elif package['status'] == 'vulnerable':
object_id = self.get_package_object_id(package['name'],
package['id_base'], 1)
test_id = '{0}:tst:{1}0'.format(self.ns, package['id_base'])
self.queue_element('test', """
<linux-def:dpkginfo_test id="{0}" version="{1}" check_existence="at_least_one_exists" check="all" comment="Does the '{2}' package exist?">
<linux-def:object object_ref="{3}"/>
</linux-def:dpkginfo_test>
""".format(test_id, 1, package['name'], object_id))
return {'id': test_id, 'comment': package['note']}
elif package['status'] == 'fixed':
object_id = self.get_package_object_id(package['name'],
package['id_base'], 1)
state_id = '{0}:ste:{1}0'.format(self.ns, package['id_base'])
self.queue_element('state', """
<linux-def:dpkginfo_state id="{0}" version="{1}" comment="The package name is '{2}' and the version is less than '{3}'.">
<linux-def:name>{2}</linux-def:name>
<linux-def:evr datatype="debian_evr_string" operation="less than">{3}</linux-def:evr>
</linux-def:dpkginfo_state>
""".format(state_id, 1, package['name'], package['fix-version']))
test_id = '{0}:tst:{1}0'.format(self.ns, package['id_base'])
self.queue_element('test', """
<linux-def:dpkginfo_test id="{0}" version="{1}" check_existence="at_least_one_exists" check="all" comment="Does the '{2}' package exist and is the version less than '{3}'?">
<linux-def:object object_ref="{4}" />
<linux-def:state state_ref="{5}" />
</linux-def:dpkginfo_test>
""".format(test_id, 1, package['name'], package['fix-version'], object_id, state_id))
return {'id': test_id, 'comment': package['note']}
else:
if package['status'] != 'unknown':
self.warn('"{0}" is not a supported package status. Outputting for "unknown" status.'.format(package['status']))
if not hasattr(self, 'id_unknown_test'):
self.id_unknown_test = '{0}:tst:10'.format(self.ns)
self.queue_element('test', """
<ind-def:unknown_test id="{0}" check="all" comment="The result of this test is always UNKNOWN." version="1" />
""".format(self.id_unknown_test))
return {'id': self.id_unknown_test, 'comment': package['note']}
def add_release_applicability_definition(self, version,
kernel_version_pattern, id):
""" add platform/release applicability OVAL definition for codename """
mapping = {
'ns': self.ns,
'id_base': id,
'codename': self.release_codename,
'release_version': version,
'kernel_version_pattern': kernel_version_pattern
}
self.release_version = version
self.release_applicability_definition_id = \
'{ns}:def:{id_base}0'.format(**mapping)
self.queue_element('definition', """
<definition class="inventory" id="{ns}:def:{id_base}0" version="1">
<metadata>
<title>Check that Ubuntu {release_version} ({codename}) is installed.</title>
<description></description>
</metadata>
<criteria>
<criterion test_ref="{ns}:tst:{id_base}0" comment="The host is part of the unix family." />
<criterion test_ref="{ns}:tst:{id_base}1" comment="The host is running Ubuntu {codename}." />
</criteria>
</definition>
""".format(**mapping))
self.queue_element('test', """
<ind-def:family_test id="{ns}:tst:{id_base}0" check="at least one" check_existence="at_least_one_exists" version="1" comment="Is the host part of the unix family?">
<ind-def:object object_ref="{ns}:obj:{id_base}0"/>
<ind-def:state state_ref="{ns}:ste:{id_base}0"/>
</ind-def:family_test>
<unix-def:uname_test id="{ns}:tst:{id_base}1" check="at least one" check_existence="at_least_one_exists" version="1" comment="Is the host running Ubuntu {codename}?">
<unix-def:object object_ref="{ns}:obj:{id_base}1"/>
<unix-def:state state_ref="{ns}:ste:{id_base}1"/>
</unix-def:uname_test>
""".format(**mapping))
self.queue_element('object', """
<ind-def:family_object id="{ns}:obj:{id_base}0" version="1" comment="The singleton family object."/>
<unix-def:uname_object id="{ns}:obj:{id_base}1" version="1" comment="The singleton uname object."/>
""".format(**mapping))
self.queue_element('state', """
<ind-def:family_state id="{ns}:ste:{id_base}0" version="1" comment="The singleton family object.">
<ind-def:family>unix</ind-def:family>
</ind-def:family_state>
<unix-def:uname_state id="{ns}:ste:{id_base}1" version="1" comment="Ubuntu {release_version}">
<unix-def:os_name>Linux</unix-def:os_name>
<unix-def:os_release operation="pattern match">{kernel_version_pattern}</unix-def:os_release>
<unix-def:os_version operation="pattern match">Ubuntu</unix-def:os_version>
</unix-def:uname_state>
""".format(**mapping))
def get_package_object_id(self, name, id_base, version=1):
""" create unique objects for each package and return their OVAL id """
if not hasattr(self, 'package_objects'):
self.package_objects = {}
if name not in self.package_objects:
object_id = '{0}:obj:{1}0'.format(self.ns, id_base)
self.queue_element('object', """
<linux-def:dpkginfo_object id="{0}" version="{1}" comment="The '{2}' package.">
<linux-def:name>{2}</linux-def:name>
</linux-def:dpkginfo_object>
""".format(object_id, version, name))
self.package_objects[name] = object_id
return self.package_objects[name]
def _open(self, fn, mode, encoding='utf-8'):
""" open file """
fd = None
if sys.version_info[0] < 3:
fd = open(fn, mode=mode)
else:
fd = open(fn, mode=mode, encoding=encoding)
return fd
def queue_element(self, element, xml):
""" add an OVAL element to an output queue file """
if element not in OvalGenerator.supported_oval_elements:
self.warn('"{0}" is not a supported OVAL element.'.format(element))
return
if not hasattr(self, 'tmp'):
self.tmp = {}
self.tmp_n = random.randrange(1000000, 9999999)
if element not in self.tmp:
self.tmp[element] = self._open(os.path.join(self.tmpdir,
'./queue.{0}.{1}.xml'.format(
self.tmp_n, element)), 'wt')
# trim and fix indenting (assumes fragment is nicely indented internally)
xml = xml.strip('\n')
base_indent = re.match('\s*', xml).group(0)
xml = re.sub('^{0}'.format(base_indent), ' ', xml, 0,
re.MULTILINE)
self.tmp[element].write(xml + '\n')
def write_to_file(self):
""" dequeue all elements into one OVAL definitions file and clean up """
# close queue files for writing and then open for reading
for key in self.tmp:
self.tmp[key].close()
self.tmp[key] = self._open(self.tmp[key].name, 'rt')
tmp = os.path.join(self.tmpdir, self.output_filepath)
with self._open(tmp, 'wt') as f:
# add header
oval_timestamp = datetime.datetime.utcnow().strftime(
'%Y-%m-%dT%H:%M:%S')
f.write("""<oval_definitions
xmlns="http://oval.mitre.org/XMLSchema/oval-definitions-5"
xmlns:ind-def="http://oval.mitre.org/XMLSchema/oval-definitions-5#independent"
xmlns:oval="http://oval.mitre.org/XMLSchema/oval-common-5"
xmlns:unix-def="http://oval.mitre.org/XMLSchema/oval-definitions-5#unix"
xmlns:linux-def="http://oval.mitre.org/XMLSchema/oval-definitions-5#linux"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://oval.mitre.org/XMLSchema/oval-common-5 oval-common-schema.xsd http://oval.mitre.org/XMLSchema/oval-definitions-5 oval-definitions-schema.xsd http://oval.mitre.org/XMLSchema/oval-definitions-5#independent independent-definitions-schema.xsd http://oval.mitre.org/XMLSchema/oval-definitions-5#unix unix-definitions-schema.xsd http://oval.mitre.org/XMLSchema/oval-definitions-5#macos linux-definitions-schema.xsd">
<generator>
<oval:product_name>Canonical CVE OVAL Generator</oval:product_name>
<oval:product_version>{0}</oval:product_version>
<oval:schema_version>{1}</oval:schema_version>
<oval:timestamp>{2}</oval:timestamp>
</generator>
""".format(OvalGenerator.generator_version, OvalGenerator.oval_schema_version, oval_timestamp))
# add queued file content
for element in OvalGenerator.supported_oval_elements:
if element in self.tmp:
f.write("\n <{0}s>\n".format(element))
f.write(self.tmp[element].read().rstrip())
f.write("\n </{0}s>".format(element))
# add footer
f.write("\n</oval_definitions>")
# close and delete queue files
for key in self.tmp:
self.tmp[key].close()
os.remove(self.tmp[key].name)
# close self.output_filepath and move into place
f.close()
shutil.move(tmp, os.path.join(self.output_dir, self.output_filepath))
def unique_id_base(self, id_base, note):
""" queue a warning message """
if not hasattr(self, 'id_bases'):
self.id_bases = {}
is_unique = id_base not in self.id_bases.keys()
if not is_unique:
self.warn('ID Base collision {0} in {1} and {2}.'.format(
id_base, note, self.id_bases[id_base]))
self.id_bases[id_base] = note
return is_unique
def warn(self, message):
""" print a warning message """
print('WARNING: {0}'.format(message))
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