Source code for sshMaxArg

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
#    Copyright (C) 2015-2017 Germar Reitze
#    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
#    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.

import random
import string
import subprocess
import socket
import argparse

[docs]def randomId(size=6, chars=string.ascii_uppercase + string.digits): return ''.join(random.choice(chars) for x in range(size))
[docs]def maxArgLength(config, mid = 1048320): r = round(mid / 2) while r > 0: ssh = config.sshCommand(cmd = ['printf', randomId(mid)], nice = False, ionice = False, prefix = False) try: proc = subprocess.Popen(ssh, stdout = subprocess.PIPE, stderr = subprocess.PIPE, universal_newlines = True) out, err = proc.communicate() except OSError as e: if e.errno == 7: reportTest(mid, 'python exception: %s' % e.strerror) mid -= r else: raise else: l = len(out) if l == mid: reportTest(mid, 'can be longer') mid += r else: reportTest(mid, 'is to long') mid -= r r = round(r / 2) return mid + 6
[docs]def reportTest(mid, msg): print('Check length %s:\t%s' % (mid, msg))
[docs]def reportResult(host, mid): print('Maximum SSH argument length between "%s" and "%s" is %s' % (socket.gethostname(), host, mid))
if __name__ == '__main__': parser = argparse.ArgumentParser(description = 'Check maximal argument length on SSH connection', formatter_class=argparse.ArgumentDefaultsHelpFormatter) parser.add_argument('MID', type = int, nargs = '?', default = 1048320, help = 'Start checking with MID arg length') args = parser.parse_args() import config cfg = config.Config() mid = maxArgLength(cfg, args.MID) reportResult(cfg.sshHost(), mid)