#!/usr/bin/env python3
#
# ex:ts=4:sw=4:sts=4:et
# -*- tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*-
#
# Security Response Tool Implementation
#
# Copyright (C) 2017       Wind River Systems
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.
#
# 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 Street, Fifth Floor, Boston, MA 02110-1301 USA.

#
# Theory of operation
#
#  * This script manages the Mitre based CVE data
#

import os
import sys
import re
import xml.etree.ElementTree as ET
import argparse
import shutil
import sqlite3
from datetime import datetime, date, timedelta
import pytz

from urllib.request import urlopen, URLError, Request
from urllib.parse import urlparse

# load the srt.sqlite schema indexes
dir_path = os.path.dirname(os.path.dirname(os.path.realpath(__file__)))
sys.path.insert(0, dir_path)
from common.srt_schema import ORM

# Constants

srtDbName = 'srt.sqlite'
srtErrorLog = 'srt_errors.txt'

mitre_cvrf_url = 'https://cve.mitre.org/data/downloads'
mitre_cvrf_xml = 'data/allitems-cvrf-year-2018.xml'
mitre_cache_dir = 'data/cache/mitre'

#################################
# Helper methods
#

# Debugging support
verbose = False

# Development support
overrides = {}
def set_override(key,value=None):
    if not value is None:
        overrides[key] = value
    elif key in os.environ.keys():
        overrides[key] = 'yes' if os.environ[key].startswith('1') else 'no'
    else:
        overrides[key] = 'no'
    if 'yes' == overrides[key]:
        print("OVERRIDE:%s=%s" % (key,overrides[key]))

def get_override(key):
    if key in overrides.keys():
        return 'yes' == overrides[key]
    return False

def get_name_sort(cve_name):
    try:
        a = cve_name.split('-')
        cve_name_sort = '%s-%s-%07d' % (a[0],a[1],int(a[2]))
    except:
        cve_name_sort = cve_name
    return cve_name_sort

def srt_error_log(msg):
    f1=open(srtErrorLog, 'a')
    f1.write("|" + msg + "|\n" )
    f1.close()


# Newly discovered or updated CVEs default to NEW for triage
# Inited CVEs default to HISTORICAL, unless they are within the courtesy CVE_INIT_NEW_DELTA
init_new_date = None
def get_cve_default_status(is_init,publishedDate):
    global init_new_date

    if None == init_new_date:
        # Precalculate and cache the relative 'new' date for efficiency
        conn = sqlite3.connect(srtDbName)
        cur = conn.cursor()
        sql = '''SELECT * FROM orm_srtsetting WHERE name=?'''
        CVE_INIT_NEW_DELTA = cur.execute(sql, ('CVE_INIT_NEW_DELTA',)).fetchone()
        if CVE_INIT_NEW_DELTA is None:
            cve_init_new_delta = 30
        else:
            cve_init_new_delta = int(CVE_INIT_NEW_DELTA[ORM.SRTSETTING_VALUE])

        date_delta = timedelta(days=cve_init_new_delta)
        init_new_date = datetime.now(pytz.utc) - date_delta
        #print("\nPreset new data = %s" % init_new_date.strftime("%Y%m%d"))
        init_new_date = init_new_date.strftime("%Y-%m-%d")

    if is_init:
        # Note: the NIST 'published date' is in the format "2017-05-11", so do a simple string compare
        #print("INIT status: %s versus %s" % (init_new_date,publishedDate))
        if not publishedDate or (publishedDate > init_new_date):
            return ORM.STATUS_NEW
        else:
            return ORM.STATUS_HISTORICAL
    else:
        return ORM.STATUS_NEW

#################################
# Fetch a CVRF record from Mitre
#    REST API, cache the results
#

def _extract_text(elem):
    summary = {}
    summary['Title'] = ''
    summary['CVE'] = ''
    summary['Description'] = ''
    summary['Published'] = ''
    summary['Modified'] = ''
    for child_v in elem:
        #print("child_v=%s" % child_v)
        if 'Title' in child_v.tag:
            summary['Title'] = child_v.text
        elif 'CVE' in child_v.tag:
            summary['CVE'] = child_v.text
        elif 'Notes' in child_v.tag:
            for child_n in child_v:
                if 'Note' in child_n.tag:
                    if 'Description' == child_n.attrib['Type']:
                        summary['Description'] = child_n.text.replace('\n','\\r')
                    elif 'Other' == child_n.attrib['Type']:
                        summary[child_n.attrib['Title']] = child_n.text
        elif 'References' in child_v.tag:
            for i,child_r in enumerate(child_v):
                description = ''
                url = ''
                for child_re in child_r:
                    if 'Description' in child_re.tag:
                        description = child_re.text
                    elif 'URL' in child_re.tag:
                        url = child_re.text
                summary['Reference[%d]' % i] = "%s|%s" % (description,url)
    return summary

def extract_content_to_text(elem):
    msg = ''
    summary = _extract_text(elem)
    for key in summary.keys():
        msg += '%s=%s\n' % (key,summary[key])
    return msg

def fetch_cve(cve_name,cvrf_xml_file):
    datasource_xml = os.path.join(srtool_basepath,cvrf_xml_file)
    cache_file = os.path.join(srtool_basepath,mitre_cache_dir,"%s.txt" % cve_name)

    # Insure the cache dir exists
    cache_dir = os.path.join(srtool_basepath,mitre_cache_dir)
    if not os.path.isdir(cache_dir):
        try:
            os.makedirs(cache_dir)
        except:
            pass

    if not os.path.isfile(cache_file):
        if verbose: print("MITRE:FILEOPEN:%s" % datasource_xml)

        tree = ET.parse(datasource_xml)
        root = tree.getroot()
        found = None
        for child in root:
            if 'Vulnerability' in child.tag:
                for child_v in child:
                    if 'CVE' in child_v.tag:
                        if cve_name == child_v.text:
                            # Found the CVE!
                            found = child
                            break
        if found:
            # Extract the record
            msg = extract_content_to_text(found)
            with open(cache_file, 'w') as fp:
                fp.writelines(msg)
        else:
            print("description=There is no CVE record for %s in the loaded Mitre public CVE database." % cve_name)
            return

    # Read cached CVE file
    # NOTE: read by line to avoid accidental type conversions by readlines()
    if verbose: print("MITRE:CACHE:%s" % cache_file)
    results = {}
    results['description'] = ''
    with open(cache_file, 'r') as fp:
        for line in fp:
            line = line.strip()
            if line.startswith('Description'): results['description'] = '%s[EOL]%s' % (line.replace('Description=','').replace('\\n','').replace('\\r',' '),results['description'])
            elif line.startswith('Published'): results['publishedDate'] = line.replace('Published=','')
            elif line.startswith('Modified'): results['lastModifiedDate'] = line.replace('Modified=','')
            else:
                results['description'] += '[EOL]%s' % line

    # Print the results
    for key in results.keys():
        print("%s=%s" % (key,results[key]))

#Reference[4]=MS:MS15-027|http://technet.microsoft.com/security/bulletin/MS15-027
#CVE=CVE-2015-0005
#Reference[0]=FULLDISC:20150310 [CORE-2015-0005] - Windows Pass-Through Authentication Methods Improper Validation|http://seclists.org/fulldisclosure/2015/Mar/60
#Modified=2016-11-29
#Reference[5]=SECTRACK:1031891|http://www.securitytracker.com/id/1031891
#Reference[2]=MISC:http://www.coresecurity.com/advisories/windows-pass-through-authentication-methods-improper-validation|http://www.coresecurity.com/advisories/windows-pass-through-authentication-methods-improper-validation
#Title=CVE-2015-0005
#Published=2015-03-11
#Reference[3]=CONFIRM:https://www.samba.org/samba/history/samba-4.2.10.html|https://www.samba.org/samba/history/samba-4.2.10.html
#Description=The NETLOGON service in Microsoft Windows Server 2003 SP2, Windows\rServer 2008 SP2 and R2 SP1, and Windows Server 2012 Gold and R2, when\ra Domain Controller is configured, allows remote attackers to spoof\rthe computer name of a secure channel's endpoint, and obtain sensitive\rsession information, by running a crafted application and leveraging\rthe ability to sniff network traffic, aka "NETLOGON Spoofing\rVulnerability."\r
#Reference[1]=MISC:http://packetstormsecurity.com/files/130773/Windows-Pass-Through-Authentication-Methods-Improper-Validation.html|http://packetstormsecurity.com/files/130773/Windows-Pass-Through-Authentication-Methods-Improper-Validation.html


#################################
# Initialize Mitre source CVE file
#

def init_mitre_file(source,url_file,datasource_file,force_update):
    datasource_url = '%s/%s' % (mitre_cvrf_url,url_file)
    datasource_xml = os.path.join(srtool_basepath,datasource_file)

    ### TODO: sync time stamps with datasource
    if os.path.isfile(datasource_xml) and not force_update:
        print("MITRE File already downloaded:%s" % datasource_xml)
        return

    response = urlopen(datasource_url)
    print("MITRE downloading '%s' as '%s'" % (datasource_url,datasource_xml))
    with open(datasource_xml, 'wb') as file:
        file.write(response.read())

    # Clear out any cached files
    cache_dir = os.path.join(srtool_basepath,mitre_cache_dir)
    if os.path.isdir(cache_dir):
        shutil.rmtree(cache_dir)

#################################
# append_cve_database
#
# Create new CVE record if not already added by NIST scan
# so that non-public CVEs can be tracked

def append_cve_database(is_init,file_xml):
    tree = ET.parse(file_xml)
    root = tree.getroot()

    # Max count for development cycle
    cmd_count = 20 if get_override('SRTDBG_MINIMAL_DB') else 0;

    conn = sqlite3.connect(srtDbName)
    cur = conn.cursor()
    cur_write = conn.cursor()
    cur_ds = conn.cursor()
    datasource_id = 0

    for i,child in enumerate(root):
        if not 'Vulnerability' in child.tag:
            continue
        summary = _extract_text(child)
        cve_name = summary['CVE']

        # Progress indicator support
        if 0 == i % 10:
            print('%04d: %20s \r' % (i,cve_name), end='')
        if (0 == i % 200):
            conn.commit()
            print('')
        if cmd_count and (i > cmd_count):
            break

        # Find the datasource matching these CVE prefixes
        if 0 == datasource_id:
            sql = "SELECT * FROM orm_datasource WHERE data = ? AND source = ?"
            cur_ds.execute(sql, ('cve','mitre',))
            for ds in cur_ds:
                if ds[ORM.DATASOURCE_CVE_FILTER] and cve_name.startswith(ds[ORM.DATASOURCE_CVE_FILTER]):
                    datasource_id = ds[ORM.DATASOURCE_ID]
                    print("*CVE source %s for %s " % (ds[ORM.DATASOURCE_ID],cve_name))
                    break
            else:
                srt_error_log("ERROR:Missing Mitre data source for '%s'" % cve_name)
                pass

        # Define the CVE (if not already there - e.g. not defined by NIST)
        sql = ''' SELECT * FROM orm_cve WHERE name = ?'''
        cve = cur_write.execute(sql, (cve_name,)).fetchone()
        if cve:
            cve_id = cve[ORM.CVE_ID]
            print("MITRE:FOUND %20s\r" % cve_name, end='')
        else:
            # Get the default CVE status
            status = get_cve_default_status(is_init,summary['Published'])

            sql = ''' INSERT into orm_cve (name, name_sort, priority, status, comments, comments_private, cve_data_type, cve_data_format, cve_data_version, public, publish_state, publish_date, description, publishedDate, lastModifiedDate, recommend, recommend_list, cvssV3_baseScore, cvssV3_baseSeverity, cvssV2_baseScore, cvssV2_severity, srt_updated, packages)
            VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)'''
            cur.execute(sql, (cve_name, get_name_sort(cve_name), ORM.PRIORITY_UNDEFINED, status, '', '', '', '', '', 1, ORM.PUBLISH_UNPUBLISHED, '', summary['Description'], summary['Published'], summary['Modified'],'', '', '', '', '', '', datetime.now(),''))
            cve_id = cur.lastrowid
            print("MITRE:ADDED %20s\r" % cve_name)

        # Add this data source to the CVE
        sql = '''SELECT * FROM orm_cvesource WHERE cve_id=? AND datasource_id=? '''
        if not cur_ds.execute(sql, (cve_id,datasource_id)).fetchone():
            sql = ''' INSERT into orm_cvesource (cve_id, datasource_id) VALUES (?, ?)'''
            cur_ds.execute(sql, (cve_id,datasource_id))

    conn.commit()
    print("\nTotal = %5d\n" % i)

#################################
# test dump
#

def dump(file_xml):
    tree = ET.parse(file_xml)
    root = tree.getroot()

    # Set this true to only print unexpected tags
    test_other_tags = True

    i = 1
    for child in root:
        if 'Vulnerability' in child.tag:
            for child_v in child:
                #print("child_v=%s" % child_v)
                if 'Title' in child_v.tag:
                    if not test_other_tags: print("V_Title=%s" % child_v.text)
                elif 'CVE' in child_v.tag:
                    if not test_other_tags: print("V_CVE=%s" % child_v.text)
                elif 'Notes' in child_v.tag:
                    for child_n in child_v:
                        #print("child_n=%s" % child_n)
                        if 'Note' in child_n.tag:
                            if 'Description' == child_n.attrib['Type']:
                                if not test_other_tags: print("V_N_Description:%s" % (child_n.text))
                            elif 'Other' == child_n.attrib['Type']:
                                if not test_other_tags: print("V_N_Note:%s:%s" % (child_n.attrib['Title'],child_n.text))
                            else:
                                print("OTHER NOTE TAG=%s" % child_n.tag)
                        else:
                            print("OTHER NOTES TAG=%s" % child_n.tag)

                elif 'References' in child_v.tag:
                    #print("Found REFERENCES")
                    for child_r in child_v:
                        for child_re in child_r:
                            if 'Description' in child_re.tag:
                                if not test_other_tags: print("V_R_Description=%s" % child_re.text)
                            elif 'URL' in child_re.tag:
                                if not test_other_tags: print("V_R_URL=%s" % child_re.text)
                            else:
                                print("OTHER REFS TAG=%s" % child_re.tag)
                else:
                    print("OTHER VULN TAG=%s" % child_v.tag)
        elif 'DocumentTitle' in child.tag:
            pass
        elif 'DocumentType' in child.tag:
            pass
        elif 'DocumentPublisher' in child.tag:
            pass
        elif 'DocumentTracking' in child.tag:
            pass
        elif 'DocumentNotes' in child.tag:
            pass
        else:
            print("OTHER TOP TAG=%s" % child.tag)

        i += 1
        if (0 == (i % 20)):
            print("%5d\r" % i,end = '')
    print("\nTotal = %5d\n" % i)

#################################
# main loop
#

def main(argv):
    global verbose

    # setup

    parser = argparse.ArgumentParser(description='srtool_mitre.py: manage Mitre CVE data')
    parser.add_argument('--initialize', '-I', action='store_const', const='init_mitre', dest='command', help='Download the Mitre source CVE file')
    parser.add_argument('--update', '-u', action='store_const', const='update_mitre', dest='command', help='Update the Mitre source CVE file')
    parser.add_argument('--source', dest='source', help='Local CVE source file')
    parser.add_argument('--url-file', dest='url_file', help='CVE URL extension')
    parser.add_argument('--cve-detail', '-d', dest='cve_detail', help='Fetch CVE detail')
    parser.add_argument('--file', dest='cve_file', help='Local CVE source file')
    parser.add_argument('--force-update', '-f', action='store_true', dest='force_update', help='Force update')
    parser.add_argument('--verbose', '-v', action='store_true', dest='is_verbose', help='Enable verbose debugging output')
    parser.add_argument('--dump', '-D', action='store_const', const='dump', dest='command', help='test dump data')
    parser.add_argument('--dump2', '-2', action='store_const', const='dump2', dest='command', help='test dump data')

    args = parser.parse_args()

    if args.is_verbose:
        verbose = True

    if 'dump' == args.command:
        dump(mitre_cvrf_xml)
        return
    if 'dump2' == args.command:
        dump('data/cache/mitre/CVE-2018-0005.xml')
        return

    # Required parameters to continue
    if not args.cve_file:
        print("ERROR: missing --cve_file parameter")
        exit(1)

    # Return a CVE detail record
    if None != args.cve_detail:
        fetch_cve(args.cve_detail,args.cve_file)
        return

    # fetch any environment overrides
    set_override('SRTDBG_MINIMAL_DB')

    # Required parameters to continue
    if not args.source:
        print("ERROR: missing --source parameter")
        exit(1)
    if not args.url_file:
        print("ERROR: missing --url_file parameter")
        exit(1)

    if 'init_mitre' == args.command:
        init_mitre_file(args.source,args.url_file,args.cve_file,args.force_update)
        append_cve_database(True,args.cve_file)
    elif 'update_mitre' == args.command:
        init_mitre_file(args.source,args.url_file,args.cve_file,args.force_update)
        append_cve_database(False,args.cve_file)
    else:
        print("Command not found")

if __name__ == '__main__':
    global srtool_basepath
    srtool_basepath = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(sys.argv[0]))))
    main(sys.argv[1:])