basic functionalty
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modules/Crypto/IO/_PBES.py
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348
modules/Crypto/IO/_PBES.py
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#
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# PublicKey/_PBES.py : Password-Based Encryption functions
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#
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# ===================================================================
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# The contents of this file are dedicated to the public domain. To
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# the extent that dedication to the public domain is not available,
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# everyone is granted a worldwide, perpetual, royalty-free,
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# non-exclusive license to exercise all rights associated with the
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# contents of this file for any purpose whatsoever.
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# No rights are reserved.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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# ===================================================================
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import sys
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if sys.version_info[0] == 2 and sys.version_info[1] == 1:
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from Crypto.Util.py21compat import *
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from Crypto.Util.py3compat import *
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from Crypto import Random
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from Crypto.Util.asn1 import *
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from Crypto.Util.Padding import pad, unpad
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from Crypto.Hash import MD5, SHA1
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from Crypto.Cipher import DES, ARC2, DES3, AES
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from Crypto.Protocol.KDF import PBKDF1, PBKDF2
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# These are the ASN.1 definitions used by the PBES1/2 logic:
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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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#
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# EncryptionAlgorithmIdentifier ::= AlgorithmIdentifier
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#
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# EncryptedData ::= OCTET STRING
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#
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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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#
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# PBEParameter ::= SEQUENCE {
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# salt OCTET STRING (SIZE(8)),
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# iterationCount INTEGER
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# }
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#
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# PBES2-params ::= SEQUENCE {
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# keyDerivationFunc AlgorithmIdentifier {{PBES2-KDFs}},
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# encryptionScheme AlgorithmIdentifier {{PBES2-Encs}}
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# }
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#
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# PBKDF2-params ::= SEQUENCE {
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# salt CHOICE {
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# specified OCTET STRING,
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# otherSource AlgorithmIdentifier {{PBKDF2-SaltSources}}
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# },
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# iterationCount INTEGER (1..MAX),
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# keyLength INTEGER (1..MAX) OPTIONAL,
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# prf AlgorithmIdentifier {{PBKDF2-PRFs}} DEFAULT algid-hmacWithSHA1
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# }
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#
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def decode_der(obj_class, binstr):
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"""Instantiate a DER object class, decode a DER binary string in it, and
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return the object."""
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der = obj_class()
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der.decode(binstr)
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return der
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class PBES1(object):
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"""Deprecated encryption scheme with password-based key derivation
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(originally defined in PKCS#5 v1.5, but still present in `v2.0`__).
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.. __: http://www.ietf.org/rfc/rfc2898.txt
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"""
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def decrypt(data, passphrase):
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"""Decrypt a piece of data using a passphrase and *PBES1*.
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The algorithm to use is automatically detected.
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:Parameters:
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data : byte string
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The piece of data to decrypt.
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passphrase : byte string
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The passphrase to use for decrypting the data.
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:Returns:
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The decrypted data, as a binary string.
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"""
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encrypted_private_key_info = decode_der(DerSequence, data)
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encrypted_algorithm = decode_der(
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DerSequence,
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encrypted_private_key_info[0]
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)
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encrypted_data = decode_der(
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DerOctetString,
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encrypted_private_key_info[1]
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).payload
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pbe_oid = decode_der(DerObjectId, encrypted_algorithm[0]).value
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cipher_params = {}
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if pbe_oid == "1.2.840.113549.1.5.3":
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# PBE_MD5_DES_CBC
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hashmod = MD5
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ciphermod = DES
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elif pbe_oid == "1.2.840.113549.1.5.6":
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# PBE_MD5_RC2_CBC
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hashmod = MD5
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ciphermod = ARC2
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cipher_params['effective_keylen'] = 64
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elif pbe_oid == "1.2.840.113549.1.5.10":
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# PBE_SHA1_DES_CBC
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hashmod = SHA1
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ciphermod = DES
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elif pbe_oid == "1.2.840.113549.1.5.11":
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# PBE_SHA1_RC2_CBC
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hashmod = SHA1
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ciphermod = ARC2
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cipher_params['effective_keylen'] = 64
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else:
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raise ValueError("Unknown OID")
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pbe_params = decode_der(DerSequence, encrypted_algorithm[1])
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salt = decode_der(DerOctetString, pbe_params[0]).payload
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iterations = pbe_params[1]
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key_iv = PBKDF1(passphrase, salt, 16, iterations, hashmod)
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key, iv = key_iv[:8], key_iv[8:]
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cipher = ciphermod.new(key, ciphermod.MODE_CBC, iv, **cipher_params)
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pt = cipher.decrypt(encrypted_data)
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return unpad(pt, cipher.block_size)
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decrypt = staticmethod(decrypt)
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class PBES2(object):
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"""Encryption scheme with password-based key derivation
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(defined in `PKCS#5 v2.0`__).
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.. __: http://www.ietf.org/rfc/rfc2898.txt."""
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def encrypt(data, passphrase, protection, prot_params=None, randfunc=None):
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"""Encrypt a piece of data using a passphrase and *PBES2*.
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:Parameters:
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data : byte string
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The piece of data to encrypt.
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passphrase : byte string
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The passphrase to use for encrypting the data.
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protection : string
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The identifier of the encryption algorithm to use.
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The default value is '``PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC``'.
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prot_params : dictionary
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Parameters of 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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| | The default value is 1 000. |
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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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randfunc : callable
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Random number generation function; it should accept
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a single integer N and return a string of random data,
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N bytes long. If not specified, a new RNG will be
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instantiated from ``Crypto.Random``.
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:Returns:
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The encrypted data, as a binary string.
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"""
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if prot_params is None:
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prot_params = {}
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if randfunc is None:
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randfunc = Random.new().read
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if protection == 'PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC':
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key_size = 24
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module = DES3
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protection = DES3.MODE_CBC
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enc_oid = "1.2.840.113549.3.7"
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elif protection == 'PBKDF2WithHMAC-SHA1AndAES128-CBC':
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key_size = 16
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module = AES
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protection = AES.MODE_CBC
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enc_oid = "2.16.840.1.101.3.4.1.2"
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elif protection == 'PBKDF2WithHMAC-SHA1AndAES192-CBC':
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key_size = 24
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module = AES
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protection = AES.MODE_CBC
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enc_oid = "2.16.840.1.101.3.4.1.22"
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elif protection == 'PBKDF2WithHMAC-SHA1AndAES256-CBC':
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key_size = 32
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module = AES
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protection = AES.MODE_CBC
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enc_oid = "2.16.840.1.101.3.4.1.42"
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else:
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raise ValueError("Unknown mode")
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# Get random data
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iv = randfunc(module.block_size)
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salt = randfunc(prot_params.get("salt_size", 8))
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# Derive key from password
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count = prot_params.get("iteration_count", 1000)
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key = PBKDF2(passphrase, salt, key_size, count)
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key_derivation_func = newDerSequence(
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DerObjectId("1.2.840.113549.1.5.12"), # PBKDF2
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newDerSequence(
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DerOctetString(salt),
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DerInteger(count)
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)
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)
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# Create cipher and use it
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cipher = module.new(key, protection, iv)
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encrypted_data = cipher.encrypt(pad(data, cipher.block_size))
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encryption_scheme = newDerSequence(
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DerObjectId(enc_oid),
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DerOctetString(iv)
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)
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# Result
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encrypted_private_key_info = newDerSequence(
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# encryptionAlgorithm
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newDerSequence(
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DerObjectId("1.2.840.113549.1.5.13"), # PBES2
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newDerSequence(
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key_derivation_func,
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encryption_scheme
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),
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),
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DerOctetString(encrypted_data)
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)
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return encrypted_private_key_info.encode()
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encrypt = staticmethod(encrypt)
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def decrypt(data, passphrase):
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"""Decrypt a piece of data using a passphrase and *PBES2*.
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The algorithm to use is automatically detected.
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:Parameters:
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data : byte string
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The piece of data to decrypt.
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passphrase : byte string
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The passphrase to use for decrypting the data.
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:Returns:
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The decrypted data, as a binary string.
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"""
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encrypted_private_key_info = decode_der(DerSequence, data)
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encryption_algorithm = decode_der(
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DerSequence,
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encrypted_private_key_info[0]
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)
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encrypted_data = decode_der(
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DerOctetString,
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encrypted_private_key_info[1]
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).payload
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pbe_oid = decode_der(DerObjectId, encryption_algorithm[0]).value
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if pbe_oid != "1.2.840.113549.1.5.13":
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raise ValueError("Not a PBES2 object")
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pbes2_params = decode_der(DerSequence, encryption_algorithm[1])
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### Key Derivation Function selection
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key_derivation_func = decode_der(DerSequence, pbes2_params[0])
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key_derivation_oid = decode_der(
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DerObjectId,
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key_derivation_func[0]
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).value
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# For now, we only support PBKDF2
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if key_derivation_oid != "1.2.840.113549.1.5.12":
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raise ValueError("Unknown KDF")
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pbkdf2_params = decode_der(DerSequence, key_derivation_func[1])
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salt = decode_der(DerOctetString, pbkdf2_params[0]).payload
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iteration_count = pbkdf2_params[1]
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if len(pbkdf2_params) > 2:
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pbkdf2_key_length = pbkdf2_params[2]
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else:
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pbkdf2_key_length = None
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if len(pbkdf2_params) > 3:
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raise ValueError("Unsupported PRF for PBKDF2")
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### Cipher selection
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encryption_scheme = decode_der(DerSequence, pbes2_params[1])
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encryption_oid = decode_der(
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DerObjectId,
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encryption_scheme[0]
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).value
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if encryption_oid == "1.2.840.113549.3.7":
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# DES_EDE3_CBC
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ciphermod = DES3
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key_size = 24
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elif encryption_oid == "2.16.840.1.101.3.4.1.2":
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# AES128_CBC
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ciphermod = AES
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key_size = 16
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elif encryption_oid == "2.16.840.1.101.3.4.1.22":
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# AES192_CBC
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ciphermod = AES
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key_size = 24
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elif encryption_oid == "2.16.840.1.101.3.4.1.42":
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# AES256_CBC
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ciphermod = AES
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key_size = 32
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else:
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raise ValueError("Unsupported cipher")
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if pbkdf2_key_length and pbkdf2_key_length != key_size:
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raise ValueError("Mismatch between PBKDF2 parameters"
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" and selected cipher")
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IV = decode_der(DerOctetString, encryption_scheme[1]).payload
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# Create cipher
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key = PBKDF2(passphrase, salt, key_size, iteration_count)
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cipher = ciphermod.new(key, ciphermod.MODE_CBC, IV)
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# Decrypt data
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pt = cipher.decrypt(encrypted_data)
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return unpad(pt, cipher.block_size)
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decrypt = staticmethod(decrypt)
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