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# -*- coding: utf-8 -*-
#
# PublicKey/PKCS8.py : PKCS#8 functions
#
# ===================================================================
# The contents of this file are dedicated to the public domain. To
# the extent that dedication to the public domain is not available,
# everyone is granted a worldwide, perpetual, royalty-free,
# non-exclusive license to exercise all rights associated with the
# contents of this file for any purpose whatsoever.
# No rights are reserved.
#
# 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.
# ===================================================================
"""
Module for handling private keys wrapped according to `PKCS#8`_.
PKCS8 is a standard for storing and transferring private key information.
The wrapped key can either be clear or encrypted.
All encryption algorithms are based on passphrase-based key derivation.
The following mechanisms are fully supported:
* *PBKDF2WithHMAC-SHA1AndAES128-CBC*
* *PBKDF2WithHMAC-SHA1AndAES192-CBC*
* *PBKDF2WithHMAC-SHA1AndAES256-CBC*
* *PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC*
The following mechanisms are only supported for importing keys.
They are much weaker than the ones listed above, and they are provided
for backward compatibility only:
* *pbeWithMD5AndRC2-CBC*
* *pbeWithMD5AndDES-CBC*
* *pbeWithSHA1AndRC2-CBC*
* *pbeWithSHA1AndDES-CBC*
.. _`PKCS#8`: http://www.ietf.org/rfc/rfc5208.txt
"""
import sys
if sys.version_info[0] == 2 and sys.version_info[1] == 1:
from Crypto.Util.py21compat import *
from Crypto.Util.py3compat import *
from Crypto.Util.asn1 import *
from Crypto.IO._PBES import PBES1, PBES2
__all__ = ['wrap', 'unwrap']
def decode_der(obj_class, binstr):
"""Instantiate a DER object class, decode a DER binary string in it, and
return the object."""
der = obj_class()
der.decode(binstr)
return der
def wrap(private_key, key_oid, passphrase=None, protection=None,
prot_params=None, key_params=None, randfunc=None):
"""Wrap a private key into a PKCS#8 blob (clear or encrypted).
:Parameters:
private_key : byte string
The private key encoded in binary form. The actual encoding is
algorithm specific. In most cases, it is DER.
key_oid : string
The object identifier (OID) of the private key to wrap.
It is a dotted string, like "``1.2.840.113549.1.1.1``" (for RSA keys).
passphrase : (binary) string
The secret passphrase from which the wrapping key is derived.
Set it only if encryption is required.
protection : string
The identifier of the algorithm to use for securely wrapping the key.
The default value is '``PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC``'.
prot_params : dictionary
Parameters for the protection algorithm.
+------------------+-----------------------------------------------+
| Key | Description |
+==================+===============================================+
| iteration_count | The KDF algorithm is repeated several times to|
| | slow down brute force attacks on passwords. |
| | The default value is 1 000. |
+------------------+-----------------------------------------------+
| salt_size | Salt is used to thwart dictionary and rainbow |
| | attacks on passwords. The default value is 8 |
| | bytes. |
+------------------+-----------------------------------------------+
key_params : DER object
The algorithm parameters associated to the private key.
It is required for algorithms like DSA, but not for others like RSA.
randfunc : callable
Random number generation function; it should accept a single integer
N and return a string of random data, N bytes long.
If not specified, a new RNG will be instantiated
from ``Crypto.Random``.
:Return:
The PKCS#8-wrapped private key (possibly encrypted),
as a binary string.
"""
if key_params is None:
key_params = DerNull()
#
# PrivateKeyInfo ::= SEQUENCE {
# version Version,
# privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
# privateKey PrivateKey,
# attributes [0] IMPLICIT Attributes OPTIONAL
# }
#
pk_info = newDerSequence(
0,
newDerSequence(
DerObjectId(key_oid),
key_params
),
newDerOctetString(private_key)
)
pk_info_der = pk_info.encode()
if not passphrase:
return pk_info_der
# Encryption with PBES2
passphrase = tobytes(passphrase)
if protection is None:
protection = 'PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC'
return PBES2.encrypt(pk_info_der, passphrase,
protection, prot_params, randfunc)
def unwrap(p8_private_key, passphrase=None):
"""Unwrap a private key from a PKCS#8 blob (clear or encrypted).
:Parameters:
p8_private_key : byte string
The private key wrapped into a PKCS#8 blob
passphrase : (byte) string
The passphrase to use to decrypt the blob (if it is encrypted).
:Return:
A tuple containing:
#. the algorithm identifier of the wrapped key (OID, dotted string)
#. the private key (byte string, DER encoded)
#. the associated parameters (byte string, DER encoded) or ``None``
:Raises ValueError:
If decoding fails
"""
if passphrase:
passphrase = tobytes(passphrase)
found = False
for pbes in PBES1, PBES2:
try:
p8_private_key = pbes.decrypt(p8_private_key, passphrase)
except ValueError:
pass
else:
found = True
break
if not found:
raise ValueError("Unsupported PKCS#5 Object ID ")
pk_info = decode_der(DerSequence, p8_private_key)
if len(pk_info) == 2 and not passphrase:
raise ValueError("Not a valid clear PKCS#8 structure "
"(maybe it is encrypted?)")
if not 3 <= len(pk_info) <= 4 or pk_info[0] != 0:
raise ValueError("Not a valid PrivateKeyInfo SEQUENCE")
#
# AlgorithmIdentifier ::= SEQUENCE {
# algorithm OBJECT IDENTIFIER,
# parameters ANY DEFINED BY algorithm OPTIONAL
# }
#
algo_id = decode_der(DerSequence, pk_info[1])
if not 1 <= len(algo_id) <= 2:
raise ValueError("Not a valid AlgorithmIdentifier SEQUENCE")
algo = decode_der(DerObjectId, algo_id[0]).value
private_key = decode_der(DerOctetString, pk_info[2]).payload
if len(algo_id) == 2 and algo_id[1] != b('\x05\x00'):
params = algo_id[1]
else:
params = None
return (algo, private_key, params)
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