#!/usr/bin/python

# Copyright 2011 Peter Palfrader
# Copyright 2014 Hendrik Koehler
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

import sys
import os
import time
import optparse

AVAIL = '/proc/sys/kernel/random/entropy_avail'

parser = optparse.OptionParser()
parser.add_option("-r", "--retries", dest="retries", metavar="NUM",
  type="int", default=10,
  help="Max number of retries [10].")
parser.add_option("-s", "--sleep", dest="sleep", metavar="MSECS",
  type="int", default=250,
  help="Amount of time to wait between reads [250msec].")
parser.add_option("-w", "--watermark", dest="watermark", metavar="BYTES",
  type="int", default=800,
  help="Minimum number of expected bytes in the entropy pool [800].")
(options, args) = parser.parse_args()

if len(args) != 0:
    parser.print_help()
    sys.exit(4)

if not os.path.exists(AVAIL):
    print "File %s does not exist."%(AVAIL)
    sys.exit(4)

tries = 0
values = []
while tries <= options.retries:
    f = open('/proc/sys/kernel/random/entropy_avail')
    avail = f.readline().rstrip()
    if len(avail) == 0:
        print "Could not read anything from %s"%(AVAIL)
        sys.exit(4)
    try:
        avail = int(avail)
    except ValueError:
        print "Did not read a number from %s, got '%s' instead"%(AVAIL, avail)
        sys.exit(4)

    if avail >= options.watermark:
        if tries > 0:
            print "OK: %d bytes in the pool after %d attempts.|entropy=%d bytes"%(avail, tries, avail)
        else:
            print "OK: %d bytes in the pool.|entropy=%d bytes"%(avail, avail)
        sys.exit(0)

    values.append(avail)
    time.sleep(1.0 * options.sleep / 1000)
    tries += 1

print "WARNING: Too little entropy in the pool (min: %d, max: %d in %d reads)|entropy=%d bytes"%(min(values), max(values), tries-1, avail)
sys.exit(1)

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