PyCrypto : AssertionError("PID check failed. RNG must be re-initialized after fork(). Hint: Try Random.atfork()")

Question

I am creating various processes that do different tasks. One of them and only one of them, has a security module that creates the PyCrypto objects. So my program starts, creates the various processes, the process that handles messages uses the security module to decrypt and I get the following errors:

   firstSymKeybin = self.cipher.decrypt(encFirstSymKeybin, '')
  File "/usr/local/lib/python2.7/dist-packages/Crypto/Cipher/PKCS1_v1_5.py", line 206, in decrypt
    m = self._key.decrypt(ct)
  File "/usr/local/lib/python2.7/dist-packages/Crypto/PublicKey/RSA.py", line 174, in decrypt
    return pubkey.pubkey.decrypt(self, ciphertext)
  File "/usr/local/lib/python2.7/dist-packages/Crypto/PublicKey/pubkey.py", line 93, in decrypt
    plaintext=self._decrypt(ciphertext)
  File "/usr/local/lib/python2.7/dist-packages/Crypto/PublicKey/RSA.py", line 235, in _decrypt
    r = getRandomRange(1, self.key.n-1, randfunc=self._randfunc)
  File "/usr/local/lib/python2.7/dist-packages/Crypto/Util/number.py", line 123, in getRandomRange
    value = getRandomInteger(bits, randfunc)
  File "/usr/local/lib/python2.7/dist-packages/Crypto/Util/number.py", line 104, in getRandomInteger
    S = randfunc(N>>3)
  File "/usr/local/lib/python2.7/dist-packages/Crypto/Random/_UserFriendlyRNG.py", line 187, in read
    return self._singleton.read(bytes)
  File "/usr/local/lib/python2.7/dist-packages/Crypto/Random/_UserFriendlyRNG.py", line 163, in read
    return _UserFriendlyRNG.read(self, bytes)
  File "/usr/local/lib/python2.7/dist-packages/Crypto/Random/_UserFriendlyRNG.py", line 122, in read
    self._check_pid()
  File "/usr/local/lib/python2.7/dist-packages/Crypto/Random/_UserFriendlyRNG.py", line 138, in _check_pid
    raise AssertionError("PID check failed. RNG must be re-initialized after fork(). Hint: Try Random.atfork()")
AssertionError: PID check failed. RNG must be re-initialized after fork(). Hint: Try Random.atfork()

Decrypting works well on interactive, when not called from a process.

My security module looks like this:

'''
Created on 25 Apr 2013

@author: max
'''

import base64, ast, binascii
from Crypto.Cipher import AES
from Crypto.Cipher import PKCS1_v1_5
from Crypto.PublicKey import RSA
import br_consts

class SecurityMod(object):
    '''
    classdocs
    '''

    def __init__(self):
        '''
        Constructor
        '''
        super(SecurityMod,self).__init__()
        self.privkey = RSA.importKey(open('./privkeyBR.pem', 'r').read())
        self.cipher = PKCS1_v1_5.new(self.privkey)
        self.ridToKeySalt = {}

    #depending on the type of message, encryption format is different 
    def encrypt(self, msg, rqId, rid):
        ##code
        return encMsg

    #return string of object so it can be parse by JSON
    def decrypt(self, encMsg, rqId, rid):

       #code
        return msgObjStr



    def pad_data(self,data):
        if len(data) == 0:
            return data
        if len(data) % 16 == 0:
            padding_required = 15
        else:
            padding_required = 15 - (len(data) % 16)
        data = '%s\x80' % data
        data = '%s%s' % (data, '\x00' * padding_required)
        return data


    def unpad_data(self,data):
        if not data:
            return data
        data = data.rstrip('\x00')
        if data[-1] == '\x80': 
            return data[:-1]
        else:
            return data

Answer 1

You need to call Crypto.Random.atfork() after os.fork()

I just put the __init__() in the security module before the other ones