#!/usr/bin/env python

''' This runs netstat on a local or remote server. It calculates some simple
statistical information on the number of external inet connections. It groups
by IP address. This can be used to detect if one IP address is taking up an
excessive number of connections. It can also send an email alert if a given IP
address exceeds a threshold between runs of the script. This script can be used
as a drop-in Munin plugin or it can be used stand-alone from cron. I used this
on a busy web server that would sometimes get hit with denial of service
attacks. This made it easy to see if a script was opening many multiple
connections. A typical browser would open fewer than 10 connections at once.
A script might open over 100 simultaneous connections.

./topip.py [-s server_hostname] [-u username] [-p password]
        {-a from_addr,to_addr} {-n N} {-v} {--ipv6}

    -s : hostname of the remote server to login to.
    -u : username to user for login.
    -p : password to user for login.
    -n : print stddev for the the number of the top 'N' ipaddresses.
    -v : verbose - print stats and list of top ipaddresses.
    -a : send alert if stddev goes over 20.
    -l : to log message to /var/log/topip.log
    --ipv6 : this parses netstat output that includes ipv6 format.
        Note that this actually only works with ipv4 addresses, but for
        versions of netstat that print in ipv6 format.
    --stdev=N : Where N is an integer. This sets the trigger point
        for alerts and logs. Default is to trigger if the
        max value is over 5 standard deviations.

Example:

    This will print stats for the top IP addresses connected to the given host:

        ./topip.py -s www.example.com -u mylogin -p mypassword -n 10 -v

    This will send an alert email if the maxip goes over the stddev trigger
    value and the the current top ip is the same as the last top ip
    (/tmp/topip.last):

        ./topip.py -s www.example.com -u mylogin -p mypassword \\
                -n 10 -v -a alert@example.com,user@example.com

    This will print the connection stats for the localhost in Munin format:

        ./topip.py

PEXPECT LICENSE

    This license is approved by the OSI and FSF as GPL-compatible.
        http://opensource.org/licenses/isc-license.txt

    Copyright (c) 2012, Noah Spurrier <noah@noah.org>
    PERMISSION TO USE, COPY, MODIFY, AND/OR DISTRIBUTE THIS SOFTWARE FOR ANY
    PURPOSE WITH OR WITHOUT FEE IS HEREBY GRANTED, PROVIDED THAT THE ABOVE
    COPYRIGHT NOTICE AND THIS PERMISSION NOTICE APPEAR IN ALL COPIES.
    THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
    MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

'''

from __future__ import absolute_import
from __future__ import print_function
from __future__ import unicode_literals

# See http://pexpect.sourceforge.net/
import pexpect
import pxssh
import os
import sys
import time
import getopt
import pickle
import getpass
import smtplib
from pprint import pprint


try:
    raw_input
except NameError:
    raw_input = input


TOPIP_LOG_FILE = '/var/log/topip.log'
TOPIP_LAST_RUN_STATS = '/var/run/topip.last'

def exit_with_usage():

    print(globals()['__doc__'])
    os._exit(1)

def stats(r):

    '''This returns a dict of the median, average, standard deviation,
    min and max of the given sequence.

    >>> from topip import stats
    >>> print stats([5,6,8,9])
    {'med': 8, 'max': 9, 'avg': 7.0, 'stddev': 1.5811388300841898, 'min': 5}
    >>> print stats([1000,1006,1008,1014])
    {'med': 1008, 'max': 1014, 'avg': 1007.0, 'stddev': 5.0, 'min': 1000}
    >>> print stats([1,3,4,5,18,16,4,3,3,5,13])
    {'med': 4, 'max': 18, 'avg': 6.8181818181818183, 'stddev': 5.6216817577237475, 'min': 1}
    >>> print stats([1,3,4,5,18,16,4,3,3,5,13,14,5,6,7,8,7,6,6,7,5,6,4,14,7])
    {'med': 6, 'max': 18, 'avg': 7.0800000000000001, 'stddev': 4.3259218670706474, 'min': 1}
    '''

    total = sum(r)
    avg = float(total)/float(len(r))
    sdsq = sum([(i-avg)**2 for i in r])
    s = sorted(list(r))
    return dict(list(zip(['med', 'avg', 'stddev', 'min', 'max'],
        (s[len(s)//2], avg, (sdsq/len(r))**.5, min(r), max(r)))))

def send_alert (message, subject, addr_from, addr_to, smtp_server='localhost'):

    '''This sends an email alert.
    '''

    message = ( 'From: %s\r\nTo: %s\r\nSubject: %s\r\n\r\n'
            % (addr_from, addr_to, subject) + message )
    server = smtplib.SMTP(smtp_server)
    server.sendmail(addr_from, addr_to, message)
    server.quit()

def main():

    # Parse the options, arguments, etc.
    try:
        optlist, args = getopt.getopt(sys.argv[1:],
                'h?valqs:u:p:n:', ['help','h','?','ipv6','stddev='])
    except Exception as e:
        print(str(e))
        exit_with_usage()
    options = dict(optlist)

    munin_flag = False
    if len(args) > 0:
        if args[0] == 'config':
            print('graph_title Netstat Connections per IP')
            print('graph_vlabel Socket connections per IP')
            print('connections_max.label max')
            print('connections_max.info Maximum number of connections per IP')
            print('connections_avg.label avg')
            print('connections_avg.info Average number of connections per IP')
            print('connections_stddev.label stddev')
            print('connections_stddev.info Standard deviation')
            return 0
        elif args[0] != '':
            print(args, len(args))
            return 0
            exit_with_usage()
    if [elem for elem in options if elem in ['-h','--h','-?','--?','--help']]:
        print('Help:')
        exit_with_usage()
    if '-s' in options:
        hostname = options['-s']
    else:
        # if host was not specified then assume localhost munin plugin.
        munin_flag = True
        hostname = 'localhost'
    # If localhost then don't ask for username/password.
    if hostname != 'localhost' and hostname != '127.0.0.1':
        if '-u' in options:
            username = options['-u']
        else:
            username = raw_input('username: ')
        if '-p' in options:
            password = options['-p']
        else:
            password = getpass.getpass('password: ')
        use_localhost = False
    else:
        use_localhost = True

    if '-l' in options:
        log_flag = True
    else:
        log_flag = False
    if '-n' in options:
        average_n = int(options['-n'])
    else:
        average_n = None
    if '-v' in options:
        verbose = True
    else:
        verbose = False
    if '-a' in options:
        alert_flag = True
        (alert_addr_from, alert_addr_to) = tuple(options['-a'].split(','))
    else:
        alert_flag = False
    if '--ipv6' in options:
        ipv6_flag = True
    else:
        ipv6_flag = False
    if '--stddev' in options:
        stddev_trigger = float(options['--stddev'])
    else:
        stddev_trigger = 5

    if ipv6_flag:
        netstat_pattern = r'(\S+)\s+(\S+)\s+(\S+)\s+(\S+)\s+::ffff:(\S+):(\S+)\s+.*?\r'
    else:
        netstat_pattern = r'(\S+)\s+(\S+)\s+(\S+)\s+(\S+)\s+(?:::ffff:)*(\S+):(\S+)\s+.*?\r'
        #netstat_pattern = r'(\S+)\s+(\S+)\s+(\S+)\s+(\S+)\s+(\S+):(\S+)\s+.*?\r'

    # run netstat (either locally or via SSH).
    if use_localhost:
        p = pexpect.spawn('netstat -n -t')
        PROMPT = pexpect.TIMEOUT
    else:
        p = pxssh.pxssh()
        p.login(hostname, username, password)
        p.sendline('netstat -n -t')
        PROMPT = p.PROMPT

    # For each matching netstat_pattern put the ip address in the list.
    ip_list = {}
    try:
        while 1:
            i = p.expect([PROMPT, netstat_pattern])
            if i == 0:
                break
            k = p.match.groups()[4].decode('utf-8')
            if k in ip_list:
                ip_list[k] = ip_list[k] + 1
            else:
                ip_list[k] = 1
    except:
        pass

    # remove a few common, uninteresting addresses from the dictionary.
    ip_list = dict([ (key,value) for key,value in ip_list.items() if '192.168.' not in key])
    ip_list = dict([ (key,value) for key,value in ip_list.items() if '127.0.0.1' not in key])

    ip_list = list(ip_list.items())
    if len(ip_list) < 1:
        if verbose: print('Warning: no networks connections worth looking at.')
        return 0
    ip_list.sort(key=lambda x:x[1])

    # generate some stats for the ip addresses found.
    if average_n is not None and average_n <= 1:
        average_n = None
    # Reminder: the * unary operator treats the list elements as arguments.
    zipped = zip(*ip_list[0:average_n])
    s = stats(list(zipped)[1])
    s['maxip'] = ip_list[0]

    # print munin-style or verbose results for the stats.
    if munin_flag:
        print('connections_max.value', s['max'])
        print('connections_avg.value', s['avg'])
        print('connections_stddev.value', s['stddev'])
        return 0
    if verbose:
        pprint (s)
        print()
        pprint (ip_list[0:average_n])

    # load the stats from the last run.
    try:
        last_stats = pickle.load(file(TOPIP_LAST_RUN_STATS))
    except:
        last_stats = {'maxip':None}

    if ( s['maxip'][1] > (s['stddev'] * stddev_trigger)
            and s['maxip']==last_stats['maxip'] ):
        if verbose: print('The maxip has been above trigger for two consecutive samples.')
        if alert_flag:
            if verbose: print('SENDING ALERT EMAIL')
            send_alert(str(s), 'ALERT on %s'
                    % hostname, alert_addr_from, alert_addr_to)
        if log_flag:
            if verbose: print('LOGGING THIS EVENT')
            fout = file(TOPIP_LOG_FILE,'a')
            #dts = time.strftime('%Y:%m:%d:%H:%M:%S', time.localtime())
            dts = time.asctime()
            fout.write ('%s - %d connections from %s\n'
                    % (dts,s['maxip'][1],str(s['maxip'][0])))
            fout.close()

    # save state to TOPIP_LAST_RUN_STATS
    try:
        pickle.dump(s, file(TOPIP_LAST_RUN_STATS,'w'))
        os.chmod (TOPIP_LAST_RUN_STATS, 0o664)
    except:
        pass
    # p.logout()

if __name__ == '__main__':
    main()