#!/usr/bin/env python
# kernel-check -- Gentoo Kernel Security
# Copyright 2009-2009 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2

import mmap
import os
import portage
import re
import xml.etree.cElementTree


ARCHES = [
    'all', 'alpha', 'amd64', 'amd64-fbsd', 'arm', 'hppa', 'ia64', 'm68k',
    'mips', 'ppc', 'ppc64', 's390', 'sh', 'sparc', 'sparc-fbsd', 'x86',
    'x86-fbsd'
]

REGEX = {
    'argument'   : re.compile(r'(CVE-(\d{4})-(\d{4}))|(\d{5,7})'),
    'gp_version' : re.compile(r'(?<=K_GENPATCHES_VER\=\").+(?=\")'),
    'gp_want'    : re.compile(r'(?<=K_WANT_GENPATCHES\=\").+(?=\")'),
    'k_version'  : re.compile(r'^((?:\d{1,2}\.){0,4}\d{1,2})(-.*)?$'),
    'rc_kernel'  : re.compile(r'^rc\d{1,3}$'),
    'git_kernel' : re.compile(r'^git(\d{1,3})$'),
    'r_kernel'   : re.compile(r'^r\d{1,3}$')
}

SUPPORTED = ['gentoo', 'vanilla', 'hardened']

KERNEL_TYPES = [
    'aa', 'acpi', 'ac', 'alpha', 'arm', 'as', 'cell', 'ck', 'compaq', 'crypto',
    'development', 'gaming','gentoo-dev', 'gentoo', 'gentoo-test', 'gfs',
    'git', 'grsec', 'gs', 'hardened-dev', 'hardened', 'hppa-dev', 'hppa',
    'ia64', 'kurobox', 'linux', 'lolo', 'mips-prepatch', 'mips', 'mjc', 'mm',
    'mosix', 'openblocks', 'openmosix','openvz', 'pac', 'pegasos-dev',
    'pegasos', 'pfeifer', 'planet-ccrma', 'ppc64', 'ppc-development',
    'ppc-dev', 'ppc', 'redhat', 'rsbac-dev', 'rsbac', 'selinux', 'sh',
    'sparc-dev', 'sparc', 'suspend2', 'systrace', 'tuxonice', 'uclinux',
    'usermode', 'vanilla-prepatch', 'vanilla', 'vanilla-tiny', 'vserver-dev',
    'vserver', 'win4lin', 'wolk-dev', 'wolk', 'xbox', 'xen', 'xfs'
]

VERSION = '0.3.14'
DEBUG = False
FILEPATH = os.path.dirname(os.path.realpath(__file__))
PORTDIR = portage.settings['PORTDIR']
DIR = {
    'tmp' : os.path.join(FILEPATH, 'tmp'),
    'out' : os.path.join(PORTDIR, 'metadata', 'kernel'),
    'bug' : os.path.join(FILEPATH, 'tmp', 'bug'),
    'nvd' : os.path.join(FILEPATH, 'tmp', 'nvd')
}

def BUG_ON(msg, e):
    if DEBUG:
        print('[DEBUG] line %s in %s(): %s -> %s' % (inspect.stack()[1][2],
              inspect.stack()[1][3], msg, e))


class Evaluation:
    """Evaluation class

    Provides information about the vulnerability of a kernel.
    """

    read = int()
    arch = int()
    affected = list()
    unaffected = list()
    avg_cvss = float()
    low = int()
    medium = int()
    high = int()

    def __init__(self):
        self.affected = list()
        self.unaffected = list()

    def __repr__(self):
        severity = str()
        if self.high is not 0:
            severity += '%s high' % self.high
        if self.medium is not 0:
            if self.high is not 0:
                severity += ', '
            severity += '%s medium' % self.medium
        if self.low is not 0:
            if self.high is not 0 or self.medium is not 0:
                severity += ', '
            severity += '%s low' % self.low

        return severity


class Comparison: #TODO Check if deprecated
    """Comparison class
    """

    fixed = int()
    new = list()
    #TODO add more information

    def __init__(self):
        self.fixed = list()
        self.new = list()


class Cve:
    """Common vulnerabilities and exposures class

    Contains all important information about a cve.

    Attributes:
    cve: a string represeting the cve number of the class.
    desc: a string providing a detailed description for the cve.
    published: a string representing the original cve release date.
    refs: a list of external references.
    severity: a string representing the cve severity.
    score: a floating point representing cvss base score.
    vector: a string providing the cve access vector.
    """

    cve = str()
    desc = str()
    published = str()
    refs = list()
    severity = str()
    score = float()
    vector = str()

    def __init__(self, cve):
        self.cve = cve

    def __eq__(self, diff):
        return (self.cve == diff.cve) #FIXME is this enough?

    def __ne__(self, diff):
        return not self.__eq__(diff)


class Genpatch:
    'Genpatch class'

    base = bool()
    extras = bool()
    kernel = None
    version = str()

    def __init__(self, version):
        self.version = version


    def __repr__(self):
        if self.base and self.extras:
            return 'base extras'
        if self.base:
            return 'base'
        if self.extras:
            return 'extras'


    def __eq__(self, diff):
        if self.kernel == diff.kernel:
            return (''.join((str(self.base), str(self.extras), self.version))
                 == ''.join((str(diff.base), str(diff.extras), diff.version)))
        else:
            return False


    def __ne__(self, diff):
        return not self.__eq__(diff)


class Kernel:
    'Kernel class'

    revision = str()
    source = str()
    version = str()
    genpatch = None

    def __init__(self, source):
        self.source = source


    def __repr__(self):
        return str(self.version + '-' + self.source + '-' + self.revision)


    def __eq__(self, diff):
        return (''.join((self.revision, self.source,
                         self.version, str(self.genpatch)))
             == ''.join((diff.revision, diff.source,
                         diff.version, str(diff.genpatch))))


    def __ne__(self, diff):
        return not self.__eq__(diff)


class Vulnerability:
    'Vulnerability class'

    arch = str()
    bugid = int()
    cvelist  = list()
    cves = list()
    affected = list()
    reported = str()
    reporter = str()
    status = str()

    def __init__(self, bugid):
        self.bugid = bugid

    def __eq__(self, diff):
        return (self.bugid == diff.bugid) #FIXME is this enough?

    def __ne__(self, diff):
        return not self.__eq__(diff)


class Interval:
    """Interval class

    Provides one interval entry for a vulnerability

    Attributes:
    name: a string representing the name of the kernel release
    lower: a string representing the lower boundary of the interval
    upper: a string representing the upper boundary of the interval
    lower_i: a boolean indicating if the lower boundary is inclusive
    upper_i: a boolean indicating if the upper boundary is inclusive
    """

    name = str()
    lower = str()
    upper = str()
    lower_i = bool()
    upper_i = bool()

    def __init__(self, name, lower, upper, lower_i, upper_i):
        if name == 'linux' or name == 'genpatches':
            pass
        elif name == 'gp':
            name = 'genpatches'

        name = name.replace('-sources', '')

        self.name = name
        self.lower_i = lower_i
        self.upper_i = upper_i
        if name == 'genpatches':
            if lower:
                self.lower = lower.replace('-','.')
            else:
                self.lower = lower
            if upper:
                self.upper = upper.replace('-','.')
            else:
                self.upper = upper
        else:
            self.lower = lower
            self.upper = upper


    def __repr__(self):
        interval = str(self.name)
        interval += ' '
        if self.lower and self.lower_i:
            interval += '>=%s ' % self.lower
        if self.lower and not self.lower_i:
            interval += '>%s ' % self.lower
        if self.upper and self.upper_i:
            interval += '<=%s' % self.upper
        if self.upper and not self.upper_i:
            interval += '<%s' % self.upper

        return interval


def interval_from_xml(root):
    'Returns an interval from xml'

    name = root.get('source')

    lower = ''
    upper = ''
    lower_i = False
    upper_i = False

    if root.find('lower') is not None:
        lower = root.find('lower').text
        lower_i = (root.find('lower').get('inclusive') == 'true')

    if root.find('upper') is not None:
        upper = root.find('upper').text
        upper_i = (root.find('upper').get('inclusive') == 'true')

    return Interval(name, lower, upper, lower_i, upper_i)


#TODO Add more kernel
def is_in_interval(interval, kernel, bugid=None):
    'Returns True if the given version is inside our specified interval'

    version = str()

    if interval.name == 'linux':
        version = kernel.version

    elif interval.name == 'genpatches':
        version = kernel.version.replace('-', '.')

    elif interval.name == 'hardened':
        version = kernel.version #TODO is this correct?

    elif interval.name == 'xen':
        version = kernel.version #TODO is this correct?

    elif interval.name == 'vserver':
        return False

    else:
        BUG_ON(interval.name, bugid.bugid)
        return False

    for item in ['lower', 'upper']:
        if getattr(interval, item):
            result = portage.versions.vercmp(version, getattr(interval, item))

            if result == None:
                BUG_ON('Could not compare %s and %s' %
                       (getattr(interval, item),version), bugid)

            if result == 0 and not getattr(interval, item + '_i'):
                return False

            if result == 0 and getattr(interval, item + '_i'):
                return True

            if item == 'lower' and result < 0:
                    return False

            if item == 'upper' and result > 0:
                    return False

    return True


def get_genpatch(directory, kernel):
    'Returns a list containing all genpatches from portage'

    patches = list()
    directory = os.path.join(directory, 'sys-kernel')

    for sources in os.listdir(directory):
        if '-sources' in sources:
            for ebuild in os.listdir(os.path.join(directory, sources)):
                if '.ebuild' in ebuild:
                    genpatch = extract_genpatch(ebuild, directory, sources)

                    if genpatch is not None:
                        if genpatch.kernel == kernel:
                            return genpatch

    return None


def extract_genpatch(ebuild, directory, sources):
    'Returns a genpatch from an ebuild'

    pkg = portage.versions.catpkgsplit('sys-kernel/%s' % ebuild[:-7])

    with open(os.path.join(directory, sources, ebuild), 'r') as ebuild_file:
        content = ebuild_file.read()

    try:
        genpatch_v = REGEX['gp_version'].findall(content)[0]
        genpatch_w = REGEX['gp_want'].findall(content)[0]
    except: #FIXME
        return None

    kernel = Kernel(pkg[1].replace('-sources', ''))
    kernel.version = pkg[2]
    kernel.revision = pkg[3]

    genpatch = Genpatch(pkg[2] + '-' + genpatch_v)
    genpatch.kernel = kernel
    genpatch.base = ('base' in genpatch_w)
    genpatch.extras = ('extras' in genpatch_w)

    return genpatch


def parse_cve_files(directory):
    'Returns all bug files as list'

    files = list()

    if (os.path.exists(directory)):
        for item in os.listdir(directory):
            try:
                cve_file = read_cve_file(directory, item[:-4])
                if cve_file is not None:
                    files.append(cve_file)

            except AttributeError, e:
                BUG_ON(item, e)

    return files


def find_cve(cve, directory):
    'Returns a bug containing the cve'

    for item in parse_cve_files(directory):
        for cves in item.cves:
            if cve == cves.cve:
                return item

    return None


def eval_cve_files(directory, kernel, arch, spin=None):
    'Returns a vulnerabilty evaluation'

    files = parse_cve_files(directory)

    if not files:
        return None

    cve_amount = int()
    cvss_score = int()
    evaluation = Evaluation()

    for item in files:
        if spin: #TODO migh be useful in future release (e.g. framework)
            spin.update()
        evaluation.read += 1

        if item.arch not in ARCHES:
            BUG_ON('[Error] Wrong architecture %s' % item.arch, item.bugid)

        if item.arch != arch and item.arch != 'all':
            evaluation.unaffected.append(item)
        else:
            evaluation.arch += 1

            if is_affected(item.affected, kernel, item):
                evaluation.affected.append(item)
                for cve in item.cves:
                    if cve.severity == 'Low':
                        evaluation.low += 1
                    if cve.severity == 'Medium':
                        evaluation.medium += 1
                    if cve.severity == 'High':
                        evaluation.high += 1
                    cve_amount += 1
                    cvss_score += float(cve.score)
            else:
                evaluation.unaffected.append(item)

    if cve_amount is 0:
        evaluation.avg_cvss = 0
    else:
        evaluation.avg_cvss = cvss_score / cve_amount

    return evaluation

#TODO Remove item
def is_affected(interval_list, kernel, item):
    'Returns true if a kernel is affected'

    kernel_gentoo = (kernel.source == 'gentoo' and kernel.genpatch is not None)
    kernel_affected = False
    kernel_linux_affected = False
    kernel_gp_affected  = False
    linux_interval = False
    gentoo_interval = False

    for interval in interval_list:
        if interval.name == 'genpatches':
            gentoo_interval = True
            if kernel_gentoo:
                if is_in_interval(interval, kernel.genpatch, item):
                    kernel_gp_affected = True

        elif interval.name == 'linux':
            linux_interval = True
            if is_in_interval(interval, kernel, item):
               kernel_linux_affected = True

        else:
            pass #TODO

    if linux_interval:
        if kernel_linux_affected:
            if gentoo_interval and kernel_gentoo:
                if kernel_gp_affected:
                    kernel_affected = True
                else:
                    kernel_affected = False
            else:
                kernel_affected = True
        else:
            kernel_affected = False
    else:
        if kernel_gentoo and gentoo_interval:
            if kernel_gp_affected:
                kernel_affected = True
            else:
                kernel_affected = False
        #TODO Implement else for hardend/xen/expand

    return kernel_affected


def compare_evaluation(kernel, compare):
    'Creates a comparison out of two evaluation instances'

    comparison = Comparison()

    if kernel.read != compare.read or kernel.arch != compare.arch:
        BUG_ON('Kernels do not match: %s' % kernel.read, compare.read)
        return

    for item in kernel.affected:
        if item not in compare.affected:
            comparison.fixed.append(item)

    for item in compare.affected:
        if item not in kernel.affected:
            comparison.new.append(item)

    return comparison


def read_cve_file(directory, bugid):
    'Read a bug file created by collector'

    cves = list()
    affected = list()

    filename = os.path.join(directory, bugid + '.xml')

    try:
        with open(filename, 'r+') as xml_data:
                memory_map = mmap.mmap(xml_data.fileno(), 0)
                root = xml.etree.cElementTree.parse(memory_map).getroot()
    except IOError, e:
        BUG_ON(filename, e)
        return None

    bugroot = root.find('bug')

    vul = Vulnerability(bugroot.find('bugid').text)

    for elem in ['arch', 'reported', 'reporter', 'status']:
        setattr(vul, elem, bugroot.find(elem).text)

    affectedroot = bugroot.find('affected')
    for item in affectedroot:
        interval = interval_from_xml(item)
        affected.append(interval)

    vul.affected = affected

    for item in root:
        if item.tag == 'cve':
            cve = Cve(item.find('cve').text)
            if cve is None:
                return None

            for elem in ['desc', 'published', 'refs',
                         'severity', 'score', 'vector']:
                element = item.find(elem)
                if element is not None:
                    setattr(cve, elem, element.text)
                else:
                    BUG_ON(filename, '(%s, \'No such element\')' % elem)

            cves.append(cve)
    vul.cves = cves

    return vul

#TODO Use Exceptions
def extract_version(release):
    'Extracts revision, source and version out of a release tag'

    match = REGEX['k_version'].match(release)
    if not match:
        BUG_ON('[Error] Release %s contains no valid information' % release)
        return None

    version, rest = match.groups()

    kernel = Kernel('vanilla')
    kernel.revision = 'r0'
    kernel.version = version

    for elem in (rest or '').split('-'):
        if elem == 'sources':
            pass
        elif REGEX['rc_kernel'].match(elem):
            kernel.version += '_' + elem
        elif REGEX['git_kernel'].match(elem):
            kernel.source = 'git'
            kernel.revision = 'r' + REGEX['gitd'].match(elem).groups()[0]
        elif REGEX['r_kernel'].match(elem):
            kernel.revision = elem
        elif elem in KERNEL_TYPES:
            kernel.source = elem
        elif elem != '':
            BUG_ON('Dropping unknown version component', elem)

    return kernel


def all_version(source):
    """ Given a kernel source name (e.g. vanilla), returns a Kernel object
        for the latest revision in the tree, or None if none exists. """

    versions = list()

    porttree = portage.db[portage.root]['porttree']
    matches = porttree.dbapi.xmatch('match-all',
                                    'sys-kernel/%s-sources' % source)

    for item in matches:
        best = portage.versions.catpkgsplit(item)
        if not best:
            continue

        kernel = Kernel(best[1].replace('-sources', ''))
        kernel.version = best[2]
        kernel.revision = best[3]

        versions.append(kernel)

    return versions

def gather_configuration():
    ""

    config = dict()
    mmap_min_addr = str()
    modules = str()

    try:
        mmap_min_addr = open('/proc/sys/vm/mmap_min_addr').read().strip()
    except: #FIXME
        mmap_min_addr = '?'
    config['Mmap_min_addr'] = mmap_min_addr

    try:
        for line in open('/proc/modules').readlines():
            modules += '%s ' % line.split(' ')[0]
    except: #FIXME
        modules = '?'
    config['Loaded modules'] = modules

    return config