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#
# PublicKey/PKCS8.py : PKCS#8 functions
#
# ===================================================================
#
# Copyright (c) 2014, Legrandin <helderijs@gmail.com>
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in
# the documentation and/or other materials provided with the
# distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# ===================================================================
from Crypto.Util.py3compat import *
from Crypto.Util.asn1 import (
DerNull,
DerSequence,
DerObjectId,
DerOctetString,
)
from Crypto.IO._PBES import PBES1, PBES2, PbesError
__all__ = ['wrap', 'unwrap']
def wrap(private_key, key_oid, passphrase=None, protection=None,
prot_params=None, key_params=DerNull(), randfunc=None):
"""Wrap a private key into a PKCS#8 blob (clear or encrypted).
Args:
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 (bytes string or 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 |
| | (called *N* or CPU/memory cost in scrypt). |
| | The default value for PBKDF2 is 1000. |
| | The default value for scrypt is 16384. |
+------------------+-----------------------------------------------+
| salt_size | Salt is used to thwart dictionary and rainbow |
| | attacks on passwords. The default value is 8 |
| | bytes. |
+------------------+-----------------------------------------------+
| block_size | *(scrypt only)* Memory-cost (r). The default |
| | value is 8. |
+------------------+-----------------------------------------------+
| parallelization | *(scrypt only)* CPU-cost (p). The default |
| | value is 1. |
+------------------+-----------------------------------------------+
key_params (DER object or None):
The ``parameters`` field to use in the ``AlgorithmIdentifier``
SEQUENCE. If ``None``, no ``parameters`` field will be added.
By default, the ASN.1 type ``NULL`` is used.
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 :mod:`Crypto.Random`.
Return:
The PKCS#8-wrapped private key (possibly encrypted), as a byte string.
"""
#
# PrivateKeyInfo ::= SEQUENCE {
# version Version,
# privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
# privateKey PrivateKey,
# attributes [0] IMPLICIT Attributes OPTIONAL
# }
#
if key_params is None:
algorithm = DerSequence([DerObjectId(key_oid)])
else:
algorithm = DerSequence([DerObjectId(key_oid), key_params])
pk_info = DerSequence([
0,
algorithm,
DerOctetString(private_key)
])
pk_info_der = pk_info.encode()
if passphrase is None:
return pk_info_der
if not passphrase:
raise ValueError("Empty passphrase")
# 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).
Args:
p8_private_key (byte string):
The private key wrapped into a PKCS#8 blob, DER encoded.
passphrase (byte string or 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
try:
p8_private_key = PBES1.decrypt(p8_private_key, passphrase)
found = True
except PbesError as e:
error_str = "PBES1[%s]" % str(e)
except ValueError:
error_str = "PBES1[Invalid]"
if not found:
try:
p8_private_key = PBES2.decrypt(p8_private_key, passphrase)
found = True
except PbesError as e:
error_str += ",PBES2[%s]" % str(e)
except ValueError:
error_str += ",PBES2[Invalid]"
if not found:
raise ValueError("Error decoding PKCS#8 (%s)" % error_str)
pk_info = DerSequence().decode(p8_private_key, nr_elements=(2, 3, 4, 5))
if len(pk_info) == 2 and not passphrase:
raise ValueError("Not a valid clear PKCS#8 structure "
"(maybe it is encrypted?)")
# RFC5208, PKCS#8, version is v1(0)
#
# PrivateKeyInfo ::= SEQUENCE {
# version Version,
# privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
# privateKey PrivateKey,
# attributes [0] IMPLICIT Attributes OPTIONAL
# }
#
# RFC5915, Asymmetric Key Package, version is v2(1)
#
# OneAsymmetricKey ::= SEQUENCE {
# version Version,
# privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
# privateKey PrivateKey,
# attributes [0] Attributes OPTIONAL,
# ...,
# [[2: publicKey [1] PublicKey OPTIONAL ]],
# ...
# }
if pk_info[0] == 0:
if len(pk_info) not in (3, 4):
raise ValueError("Not a valid PrivateKeyInfo SEQUENCE")
elif pk_info[0] == 1:
if len(pk_info) not in (3, 4, 5):
raise ValueError("Not a valid PrivateKeyInfo SEQUENCE")
else:
raise ValueError("Not a valid PrivateKeyInfo SEQUENCE")
algo = DerSequence().decode(pk_info[1], nr_elements=(1, 2))
algo_oid = DerObjectId().decode(algo[0]).value
if len(algo) == 1:
algo_params = None
else:
try:
DerNull().decode(algo[1])
algo_params = None
except:
algo_params = algo[1]
# PrivateKey ::= OCTET STRING
private_key = DerOctetString().decode(pk_info[2]).payload
# We ignore attributes and (for v2 only) publickey
return (algo_oid, private_key, algo_params)