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#!/usr/bin/python
# Authors:
# Ade Lee <alee@redhat.com>
#
# 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; version 2 of the License.
#
# 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.
#
# Copyright (C) 2013 Red Hat, Inc.
# All rights reserved.
#
'''
Module containing crypto classes.
'''
import abc
import base64
import nss.nss as nss
class CryptoUtil(object):
'''
Abstract class containing methods to do cryptographic operations.
'''
__metaclass__ = abc.ABCMeta
def __init__(self):
''' Constructor '''
pass
@abc.abstractmethod
def generate_symmetric_key(self, mechanism=None):
''' Generate and return a symmetric key '''
pass
@abc.abstractmethod
def symmetric_wrap(self, data, wrapping_key, mechanism=None, nonce_iv=None):
''' encrypt data using a symmetric key (wrapping key)'''
pass
@abc.abstractmethod
def symmetric_unwrap(self, data, wrapping_key, mechanism=None, nonce_iv=None):
''' decrypt data originally encrypted with symmetric key (wrapping key)
We expect the data and nonce_iv values to be base64 encoded.
The mechanism is the type of key used to do the wrapping. It defaults
to a 56 bit DES3 key.
'''
pass
@abc.abstractmethod
def asymmetric_wrap(self, data, wrapping_cert, mechanism=None):
''' encrypt a symmetric key with the public key of a transport cert.
The mechanism is the type of symmetric key, which defaults to a 56 bit
DES3 key.
'''
pass
#abc.abstractmethod
def get_cert(self, cert_nick):
''' Get the certificate for the specified cert_nick. '''
pass
class NSSCryptoUtil(CryptoUtil):
'''
Class that defines NSS implementation of CryptoUtil.
Requires an NSS database to have been set up and initialized.
'''
def __init__(self, certdb_dir, certdb_password):
''' Initialize nss and nss related parameters
This method expects a NSS database to have already been created at
certdb_dir with password certdb_password.
'''
CryptoUtil.__init__(self)
self.certdb_dir = certdb_dir
self.certdb_password = certdb_password
nss.nss_init(certdb_dir)
self.nonce_iv = "e4:bb:3b:d3:c3:71:2e:58"
@staticmethod
def setup_contexts(mechanism, sym_key, nonce_iv):
''' Set up contexts to do wrapping/unwrapping by symmetric keys. '''
# Get a PK11 slot based on the cipher
slot = nss.get_best_slot(mechanism)
if sym_key == None:
sym_key = slot.key_gen(mechanism, None, slot.get_best_key_length(mechanism))
# If initialization vector was supplied use it, otherwise set it to None
if nonce_iv:
iv_data = nss.read_hex(nonce_iv)
iv_si = nss.SecItem(iv_data)
iv_param = nss.param_from_iv(mechanism, iv_si)
else:
iv_length = nss.get_iv_length(mechanism)
if iv_length > 0:
iv_data = nss.generate_random(iv_length)
iv_si = nss.SecItem(iv_data)
iv_param = nss.param_from_iv(mechanism, iv_si)
else:
iv_param = None
# Create an encoding context
encoding_ctx = nss.create_context_by_sym_key(mechanism, nss.CKA_ENCRYPT,
sym_key, iv_param)
# Create a decoding context
decoding_ctx = nss.create_context_by_sym_key(mechanism, nss.CKA_DECRYPT,
sym_key, iv_param)
return encoding_ctx, decoding_ctx
def generate_symmetric_key(self, mechanism=nss.CKM_DES3_CBC_PAD):
''' Returns a symmetric key.'''
slot = nss.get_best_slot(mechanism)
return slot.key_gen(mechanism, None, slot.get_best_key_length(mechanism))
def symmetric_wrap(self, data, wrapping_key, mechanism=nss.CKM_DES3_CBC_PAD, nonce_iv=None):
'''
:param data: Data to be wrapped
:param wrapping_key Symmetric key to wrap data
Wrap (encrypt) data using the supplied symmetric key
'''
encoding_ctx, _decoding_ctx = self.setup_contexts(mechanism, wrapping_key, nonce_iv)
wrapped_data = encoding_ctx.cipher_op(data) + encoding_ctx.digest_final()
return wrapped_data
def symmetric_unwrap(self, data, wrapping_key, mechanism=nss.CKM_DES3_CBC_PAD, nonce_iv=None):
'''
:param data: Data to be unwrapped (base 64 encoded)
:param wrapping_key Symmetric key to unwrap data
:param nonce_iv Base 64 encoded iv data
Unwrap (decrypt) data using the supplied symmetric key
'''
if nonce_iv == None:
nonce_iv = self.nonce_iv
else:
nonce_iv = nss.data_to_hex(base64.decodestring(nonce_iv))
_encoding_ctx, decoding_ctx = self.setup_contexts(mechanism, wrapping_key, nonce_iv)
unwrapped_data = decoding_ctx.cipher_op(base64.decodestring(data)) \
+ decoding_ctx.digest_final()
return unwrapped_data
def asymmetric_wrap(self, data, wrapping_cert, mechanism=nss.CKM_DES3_CBC_PAD):
'''
:param data: Data to be wrapped
:param wrapping_cert Public key to wrap data
:param mechanism algorithm of symmetric key to be wrapped
Wrap (encrypt) data using the supplied asymmetric key
'''
public_key = wrapping_cert.subject_public_key_info.public_key
return base64.b64encode(nss.pub_wrap_sym_key(mechanism, public_key, data))
def get_cert(self, cert_nick):
'''
:param cert_nick Nickname for the certificate to be returned
Searches NSS database and returns SecItem object for this certificate.
'''
return nss.find_cert_from_nickname(cert_nick)
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