262 lines
9.4 KiB
Python
262 lines
9.4 KiB
Python
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#
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# PublicKey/PKCS8.py : PKCS#8 functions
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#
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# ===================================================================
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#
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# Copyright (c) 2014, Legrandin <helderijs@gmail.com>
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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#
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# 1. Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in
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# the documentation and/or other materials provided with the
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# distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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# ===================================================================
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"""
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Module for handling private keys wrapped according to `PKCS#8`_.
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PKCS8 is a standard for storing and transferring private key information.
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The wrapped key can either be clear or encrypted.
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All encryption algorithms are based on passphrase-based key derivation.
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The following mechanisms are fully supported:
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* *PBKDF2WithHMAC-SHA1AndAES128-CBC*
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* *PBKDF2WithHMAC-SHA1AndAES192-CBC*
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* *PBKDF2WithHMAC-SHA1AndAES256-CBC*
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* *PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC*
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* *scryptAndAES128-CBC*
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* *scryptAndAES192-CBC*
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* *scryptAndAES256-CBC*
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The following mechanisms are only supported for importing keys.
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They are much weaker than the ones listed above, and they are provided
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for backward compatibility only:
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* *pbeWithMD5AndRC2-CBC*
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* *pbeWithMD5AndDES-CBC*
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* *pbeWithSHA1AndRC2-CBC*
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* *pbeWithSHA1AndDES-CBC*
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.. _`PKCS#8`: http://www.ietf.org/rfc/rfc5208.txt
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"""
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from Crypto.Util.py3compat import *
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from Crypto.Util.asn1 import (
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DerNull,
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DerSequence,
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DerObjectId,
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DerOctetString,
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)
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from Crypto.IO._PBES import PBES1, PBES2, PbesError
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__all__ = ['wrap', 'unwrap']
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def wrap(private_key, key_oid, passphrase=None, protection=None,
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prot_params=None, key_params=None, randfunc=None):
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"""Wrap a private key into a PKCS#8 blob (clear or encrypted).
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:Parameters:
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private_key : byte string
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The private key encoded in binary form. The actual encoding is
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algorithm specific. In most cases, it is DER.
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key_oid : string
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The object identifier (OID) of the private key to wrap.
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It is a dotted string, like "``1.2.840.113549.1.1.1``" (for RSA keys).
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passphrase : (binary) string
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The secret passphrase from which the wrapping key is derived.
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Set it only if encryption is required.
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protection : string
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The identifier of the algorithm to use for securely wrapping the key.
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The default value is '``PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC``'.
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prot_params : dictionary
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Parameters for the protection algorithm.
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+------------------+-----------------------------------------------+
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| Key | Description |
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+==================+===============================================+
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| iteration_count | The KDF algorithm is repeated several times to|
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| | slow down brute force attacks on passwords |
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| | (called *N* or CPU/memory cost in scrypt). |
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| | |
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| | The default value for PBKDF2 is 1 000. |
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| | The default value for scrypt is 16 384. |
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+------------------+-----------------------------------------------+
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| salt_size | Salt is used to thwart dictionary and rainbow |
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| | attacks on passwords. The default value is 8 |
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| | bytes. |
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+------------------+-----------------------------------------------+
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| block_size | *(scrypt only)* Memory-cost (r). The default |
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| | value is 8. |
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+------------------+-----------------------------------------------+
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| parallelization | *(scrypt only)* CPU-cost (p). The default |
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| | value is 1. |
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+------------------+-----------------------------------------------+
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key_params : DER object
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The algorithm parameters associated to the private key.
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It is required for algorithms like DSA, but not for others like RSA.
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randfunc : callable
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Random number generation function; it should accept a single integer
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N and return a string of random data, N bytes long.
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If not specified, a new RNG will be instantiated
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from ``Crypto.Random``.
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:Return:
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The PKCS#8-wrapped private key (possibly encrypted),
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as a binary string.
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"""
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if key_params is None:
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key_params = DerNull()
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#
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# PrivateKeyInfo ::= SEQUENCE {
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# version Version,
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# privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
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# privateKey PrivateKey,
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# attributes [0] IMPLICIT Attributes OPTIONAL
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# }
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#
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pk_info = DerSequence([
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0,
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DerSequence([
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DerObjectId(key_oid),
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key_params
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]),
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DerOctetString(private_key)
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])
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pk_info_der = pk_info.encode()
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if passphrase is None:
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return pk_info_der
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if not passphrase:
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raise ValueError("Empty passphrase")
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# Encryption with PBES2
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passphrase = tobytes(passphrase)
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if protection is None:
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protection = 'PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC'
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return PBES2.encrypt(pk_info_der, passphrase,
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protection, prot_params, randfunc)
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def unwrap(p8_private_key, passphrase=None):
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"""Unwrap a private key from a PKCS#8 blob (clear or encrypted).
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:Parameters:
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p8_private_key : byte string
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The private key wrapped into a PKCS#8 blob, DER encoded.
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passphrase : (byte) string
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The passphrase to use to decrypt the blob (if it is encrypted).
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:Return:
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A tuple containing:
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#. the algorithm identifier of the wrapped key (OID, dotted string)
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#. the private key (byte string, DER encoded)
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#. the associated parameters (byte string, DER encoded) or ``None``
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:Raises ValueError:
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If decoding fails
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"""
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if passphrase:
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passphrase = tobytes(passphrase)
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found = False
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try:
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p8_private_key = PBES1.decrypt(p8_private_key, passphrase)
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found = True
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except PbesError as e:
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error_str = "PBES1[%s]" % str(e)
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except ValueError:
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error_str = "PBES1[Invalid]"
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if not found:
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try:
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p8_private_key = PBES2.decrypt(p8_private_key, passphrase)
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found = True
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except PbesError as e:
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error_str += ",PBES2[%s]" % str(e)
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except ValueError:
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error_str += ",PBES2[Invalid]"
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if not found:
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raise ValueError("Error decoding PKCS#8 (%s)" % error_str)
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pk_info = DerSequence().decode(p8_private_key, nr_elements=(2, 3, 4))
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if len(pk_info) == 2 and not passphrase:
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raise ValueError("Not a valid clear PKCS#8 structure "
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"(maybe it is encrypted?)")
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#
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# PrivateKeyInfo ::= SEQUENCE {
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# version Version,
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# privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
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# privateKey PrivateKey,
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# attributes [0] IMPLICIT Attributes OPTIONAL
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# }
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# Version ::= INTEGER
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if pk_info[0] != 0:
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raise ValueError("Not a valid PrivateKeyInfo SEQUENCE")
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# PrivateKeyAlgorithmIdentifier ::= AlgorithmIdentifier
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#
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# EncryptedPrivateKeyInfo ::= SEQUENCE {
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# encryptionAlgorithm EncryptionAlgorithmIdentifier,
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# encryptedData EncryptedData
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# }
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# EncryptionAlgorithmIdentifier ::= AlgorithmIdentifier
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# AlgorithmIdentifier ::= SEQUENCE {
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# algorithm OBJECT IDENTIFIER,
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# parameters ANY DEFINED BY algorithm OPTIONAL
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# }
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algo = DerSequence().decode(pk_info[1], nr_elements=(1, 2))
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algo_oid = DerObjectId().decode(algo[0]).value
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if len(algo) == 1:
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algo_params = None
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else:
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try:
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DerNull().decode(algo[1])
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algo_params = None
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except:
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algo_params = algo[1]
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# EncryptedData ::= OCTET STRING
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private_key = DerOctetString().decode(pk_info[2]).payload
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return (algo_oid, private_key, algo_params)
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