def testEncode1(self):
# Empty sequence
der = DerOctetString()
self.assertEquals(der.encode(), b('\x04\x00'))
# Small payload
der.payload = b('\x01\x02')
self.assertEquals(der.encode(), b('\x04\x02\x01\x02'))
def testEncode1(self):
# Empty sequence
der = DerOctetString()
self.assertEquals(der.encode(), b('\x04\x00'))
# Small payload
der.payload = b('\x01\x02')
self.assertEquals(der.encode(), b('\x04\x02\x01\x02'))
def testDecode1(self):
# Empty sequence
der = DerOctetString()
der.decode(b('\x04\x00'))
self.assertEquals(der.payload, b(''))
# Small payload
der.decode(b('\x04\x02\x01\x02'))
self.assertEquals(der.payload, b('\x01\x02'))
def decrypt(data, passphrase):
"""Decrypt a piece of data using a passphrase and *PBES1*.
The algorithm to use is automatically detected.
:Parameters:
data : byte string
The piece of data to decrypt.
passphrase : byte string
The passphrase to use for decrypting the data.
:Returns:
The decrypted data, as a binary string.
"""
enc_private_key_info = DerSequence().decode(data)
encrypted_algorithm = DerSequence().decode(enc_private_key_info[0])
encrypted_data = DerOctetString().decode(
enc_private_key_info[1]).payload
pbe_oid = DerObjectId().decode(encrypted_algorithm[0]).value
cipher_params = {}
if pbe_oid == _OID_PBE_WITH_MD5_AND_DES_CBC:
# PBE_MD5_DES_CBC
hashmod = MD5
ciphermod = DES
elif pbe_oid == _OID_PBE_WITH_MD5_AND_RC2_CBC:
# PBE_MD5_RC2_CBC
hashmod = MD5
ciphermod = ARC2
cipher_params['effective_keylen'] = 64
elif pbe_oid == _OID_PBE_WITH_SHA1_AND_DES_CBC:
# PBE_SHA1_DES_CBC
hashmod = SHA1
ciphermod = DES
elif pbe_oid == _OID_PBE_WITH_SHA1_AND_RC2_CBC:
# PBE_SHA1_RC2_CBC
hashmod = SHA1
ciphermod = ARC2
cipher_params['effective_keylen'] = 64
else:
raise PbesError("Unknown OID for PBES1")
pbe_params = DerSequence().decode(encrypted_algorithm[1],
nr_elements=2)
salt = DerOctetString().decode(pbe_params[0]).payload
iterations = pbe_params[1]
key_iv = PBKDF1(passphrase, salt, 16, iterations, hashmod)
key, iv = key_iv[:8], key_iv[8:]
cipher = ciphermod.new(key, ciphermod.MODE_CBC, iv, **cipher_params)
pt = cipher.decrypt(encrypted_data)
return unpad(pt, cipher.block_size)
def _export_private_der(self, include_ec_params=True):
assert self.has_private()
# ECPrivateKey ::= SEQUENCE {
# version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
# privateKey OCTET STRING,
# parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
# publicKey [1] BIT STRING OPTIONAL
# }
# Public key - uncompressed form
order_bytes = _curve.order.size_in_bytes()
public_key = (b'\x04' + self.pointQ.x.to_bytes(order_bytes) +
self.pointQ.y.to_bytes(order_bytes))
seq = [
1,
DerOctetString(self.d.to_bytes(order_bytes)),
DerObjectId(_curve.oid, explicit=0),
DerBitString(public_key, explicit=1)
]
if not include_ec_params:
del seq[2]
return DerSequence(seq).encode()
def testDecode1(self):
# Empty sequence
der = DerOctetString()
der.decode(b('\x04\x00'))
self.assertEquals(der.payload, b(''))
# Small payload
der.decode(b('\x04\x02\x01\x02'))
self.assertEquals(der.payload, b('\x01\x02'))
def _import_private_der(encoded, passphrase, curve_oid=None):
# See RFC5915 https://tools.ietf.org/html/rfc5915
#
# ECPrivateKey ::= SEQUENCE {
# version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
# privateKey OCTET STRING,
# parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
# publicKey [1] BIT STRING OPTIONAL
# }
private_key = DerSequence().decode(encoded, nr_elements=(3, 4))
if private_key[0] != 1:
raise ValueError("Incorrect ECC private key version")
try:
parameters = DerObjectId(explicit=0).decode(private_key[2]).value
if curve_oid is not None and parameters != curve_oid:
raise ValueError("Curve mismatch")
curve_oid = parameters
except ValueError:
pass
if curve_oid is None:
raise ValueError("No curve found")
for curve_name, curve in _curves.items():
if curve.oid == curve_oid:
break
else:
raise UnsupportedEccFeature("Unsupported ECC curve (OID: %s)" %
curve_oid)
scalar_bytes = DerOctetString().decode(private_key[1]).payload
modulus_bytes = curve.p.size_in_bytes()
if len(scalar_bytes) != modulus_bytes:
raise ValueError("Private key is too small")
d = Integer.from_bytes(scalar_bytes)
# Decode public key (if any)
if len(private_key) == 4:
public_key_enc = DerBitString(explicit=1).decode(private_key[3]).value
public_key = _import_public_der(public_key_enc, curve_oid=curve_oid)
point_x = public_key.pointQ.x
point_y = public_key.pointQ.y
else:
point_x = point_y = None
return construct(curve=curve_name, d=d, point_x=point_x, point_y=point_y)
def _import_private_der(encoded, passphrase, curve_name=None):
# ECPrivateKey ::= SEQUENCE {
# version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
# privateKey OCTET STRING,
# parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
# publicKey [1] BIT STRING OPTIONAL
# }
private_key = DerSequence().decode(encoded, nr_elements=(3, 4))
if private_key[0] != 1:
raise ValueError("Incorrect ECC private key version")
try:
curve_name = DerObjectId(explicit=0).decode(private_key[2]).value
except ValueError:
pass
if curve_name != _curve.oid:
raise UnsupportedEccFeature("Unsupported ECC curve (OID: %s)" %
curve_name)
scalar_bytes = DerOctetString().decode(private_key[1]).payload
order_bytes = _curve.order.size_in_bytes()
if len(scalar_bytes) != order_bytes:
raise ValueError("Private key is too small")
d = Integer.from_bytes(scalar_bytes)
# Decode public key (if any, it must be P-256)
if len(private_key) == 4:
public_key_enc = DerBitString(explicit=1).decode(private_key[3]).value
public_key = _import_public_der(curve_name, public_key_enc)
point_x = public_key.pointQ.x
point_y = public_key.pointQ.y
else:
point_x = point_y = None
return construct(curve="P-256", d=d, point_x=point_x, point_y=point_y)
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))
if len(pk_info) == 2 and not passphrase:
raise ValueError("Not a valid clear PKCS#8 structure "
"(maybe it is encrypted?)")
#
# PrivateKeyInfo ::= SEQUENCE {
# version Version,
# privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
# privateKey PrivateKey,
# attributes [0] IMPLICIT Attributes OPTIONAL
# }
# Version ::= INTEGER
if pk_info[0] != 0:
raise ValueError("Not a valid PrivateKeyInfo SEQUENCE")
# PrivateKeyAlgorithmIdentifier ::= AlgorithmIdentifier
#
# EncryptedPrivateKeyInfo ::= SEQUENCE {
# encryptionAlgorithm EncryptionAlgorithmIdentifier,
# encryptedData EncryptedData
# }
# EncryptionAlgorithmIdentifier ::= AlgorithmIdentifier
# AlgorithmIdentifier ::= SEQUENCE {
# algorithm OBJECT IDENTIFIER,
# parameters ANY DEFINED BY algorithm OPTIONAL
# }
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]
# EncryptedData ::= OCTET STRING
private_key = DerOctetString().decode(pk_info[2]).payload
return (algo_oid, private_key, algo_params)
def _EMSA_PKCS1_V1_5_ENCODE(msg_hash, emLen, with_hash_parameters=True):
"""
Implement the ``EMSA-PKCS1-V1_5-ENCODE`` function, as defined
in PKCS#1 v2.1 (RFC3447, 9.2).
``_EMSA-PKCS1-V1_5-ENCODE`` actually accepts the message ``M`` as input,
and hash it internally. Here, we expect that the message has already
been hashed instead.
:Parameters:
msg_hash : hash object
The hash object that holds the digest of the message being signed.
emLen : int
The length the final encoding must have, in bytes.
with_hash_parameters : bool
If True (default), include NULL parameters for the hash
algorithm in the ``digestAlgorithm`` SEQUENCE.
:attention: the early standard (RFC2313) stated that ``DigestInfo``
had to be BER-encoded. This means that old signatures
might have length tags in indefinite form, which
is not supported in DER. Such encoding cannot be
reproduced by this function.
:Return: An ``emLen`` byte long string that encodes the hash.
"""
# First, build the ASN.1 DER object DigestInfo:
#
# DigestInfo ::= SEQUENCE {
# digestAlgorithm AlgorithmIdentifier,
# digest OCTET STRING
# }
#
# where digestAlgorithm identifies the hash function and shall be an
# algorithm ID with an OID in the set PKCS1-v1-5DigestAlgorithms.
#
# PKCS1-v1-5DigestAlgorithms ALGORITHM-IDENTIFIER ::= {
# { OID id-md2 PARAMETERS NULL }|
# { OID id-md5 PARAMETERS NULL }|
# { OID id-sha1 PARAMETERS NULL }|
# { OID id-sha256 PARAMETERS NULL }|
# { OID id-sha384 PARAMETERS NULL }|
# { OID id-sha512 PARAMETERS NULL }
# }
#
# Appendix B.1 also says that for SHA-1/-2 algorithms, the parameters
# should be omitted. They may be present, but when they are, they shall
# have NULL value.
digestAlgo = DerSequence([ DerObjectId(msg_hash.oid).encode() ])
if with_hash_parameters:
digestAlgo.append(DerNull().encode())
digest = DerOctetString(msg_hash.digest())
digestInfo = DerSequence([
digestAlgo.encode(),
digest.encode()
]).encode()
# We need at least 11 bytes for the remaining data: 3 fixed bytes and
# at least 8 bytes of padding).
if emLen<len(digestInfo)+11:
raise TypeError("Selected hash algorith has a too long digest (%d bytes)." % len(digest))
PS = bchr(0xFF) * (emLen - len(digestInfo) - 3)
return b("\x00\x01") + PS + bchr(0x00) + digestInfo
def encrypt(data, passphrase, protection, prot_params=None, randfunc=None):
"""Encrypt a piece of data using a passphrase and *PBES2*.
:Parameters:
data : byte string
The piece of data to encrypt.
passphrase : byte string
The passphrase to use for encrypting the data.
protection : string
The identifier of the encryption algorithm to use.
The default value is '``PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC``'.
prot_params : dictionary
Parameters of 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 1 000. |
| | The default value for scrypt is 16 384. |
+------------------+-----------------------------------------------+
| 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. |
+------------------+-----------------------------------------------+
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 ``Cryptodome.Random``.
:Returns:
The encrypted data, as a binary string.
"""
if prot_params is None:
prot_params = {}
if randfunc is None:
randfunc = Random.new().read
if protection == 'PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC':
key_size = 24
module = DES3
cipher_mode = DES3.MODE_CBC
enc_oid = _OID_DES_EDE3_CBC
elif protection in ('PBKDF2WithHMAC-SHA1AndAES128-CBC',
'scryptAndAES128-CBC'):
key_size = 16
module = AES
cipher_mode = AES.MODE_CBC
enc_oid = _OID_AES128_CBC
elif protection in ('PBKDF2WithHMAC-SHA1AndAES192-CBC',
'scryptAndAES192-CBC'):
key_size = 24
module = AES
cipher_mode = AES.MODE_CBC
enc_oid = _OID_AES192_CBC
elif protection in ('PBKDF2WithHMAC-SHA1AndAES256-CBC',
'scryptAndAES256-CBC'):
key_size = 32
module = AES
cipher_mode = AES.MODE_CBC
enc_oid = _OID_AES256_CBC
else:
raise ValueError("Unknown PBES2 mode")
# Get random data
iv = randfunc(module.block_size)
salt = randfunc(prot_params.get("salt_size", 8))
# Derive key from password
if protection.startswith('PBKDF2'):
count = prot_params.get("iteration_count", 1000)
key = PBKDF2(passphrase, salt, key_size, count)
kdf_info = DerSequence([
DerObjectId(_OID_PBKDF2), # PBKDF2
DerSequence([DerOctetString(salt),
DerInteger(count)])
])
else:
# It must be scrypt
count = prot_params.get("iteration_count", 16384)
scrypt_r = prot_params.get('block_size', 8)
scrypt_p = prot_params.get('parallelization', 1)
key = scrypt(passphrase, salt, key_size, count, scrypt_r, scrypt_p)
kdf_info = DerSequence([
DerObjectId(_OID_SCRYPT), # scrypt
DerSequence([
DerOctetString(salt),
DerInteger(count),
DerInteger(scrypt_r),
DerInteger(scrypt_p)
])
])
# Create cipher and use it
cipher = module.new(key, cipher_mode, iv)
encrypted_data = cipher.encrypt(pad(data, cipher.block_size))
enc_info = DerSequence([DerObjectId(enc_oid), DerOctetString(iv)])
# Result
enc_private_key_info = DerSequence([
# encryptionAlgorithm
DerSequence([
DerObjectId(_OID_PBES2),
DerSequence([kdf_info, enc_info]),
]),
DerOctetString(encrypted_data)
])
return enc_private_key_info.encode()
def decrypt(data, passphrase):
"""Decrypt a piece of data using a passphrase and *PBES2*.
The algorithm to use is automatically detected.
:Parameters:
data : byte string
The piece of data to decrypt.
passphrase : byte string
The passphrase to use for decrypting the data.
:Returns:
The decrypted data, as a binary string.
"""
enc_private_key_info = DerSequence().decode(data, nr_elements=2)
enc_algo = DerSequence().decode(enc_private_key_info[0])
encrypted_data = DerOctetString().decode(
enc_private_key_info[1]).payload
pbe_oid = DerObjectId().decode(enc_algo[0]).value
if pbe_oid != _OID_PBES2:
raise PbesError("Not a PBES2 object")
pbes2_params = DerSequence().decode(enc_algo[1], nr_elements=2)
### Key Derivation Function selection
kdf_info = DerSequence().decode(pbes2_params[0], nr_elements=2)
kdf_oid = DerObjectId().decode(kdf_info[0]).value
kdf_key_length = None
# We only support PBKDF2 or scrypt
if kdf_oid == _OID_PBKDF2:
pbkdf2_params = DerSequence().decode(kdf_info[1],
nr_elements=(2, 3, 4))
salt = DerOctetString().decode(pbkdf2_params[0]).payload
iteration_count = pbkdf2_params[1]
left = len(pbkdf2_params) - 2
idx = 2
if left > 0:
try:
kdf_key_length = pbkdf2_params[idx] - 0
left -= 1
idx += 1
except TypeError:
pass
# Default is HMAC-SHA1
pbkdf2_prf_oid = "1.2.840.113549.2.7"
if left > 0:
pbkdf2_prf_algo_id = DerSequence().decode(pbkdf2_params[idx])
pbkdf2_prf_oid = DerObjectId().decode(
pbkdf2_prf_algo_id[0]).value
elif kdf_oid == _OID_SCRYPT:
scrypt_params = DerSequence().decode(kdf_info[1],
nr_elements=(4, 5))
salt = DerOctetString().decode(scrypt_params[0]).payload
iteration_count, scrypt_r, scrypt_p = [
scrypt_params[x] for x in (1, 2, 3)
]
if len(scrypt_params) > 4:
kdf_key_length = scrypt_params[4]
else:
kdf_key_length = None
else:
raise PbesError("Unsupported PBES2 KDF")
### Cipher selection
enc_info = DerSequence().decode(pbes2_params[1])
enc_oid = DerObjectId().decode(enc_info[0]).value
if enc_oid == _OID_DES_EDE3_CBC:
# DES_EDE3_CBC
ciphermod = DES3
key_size = 24
elif enc_oid == _OID_AES128_CBC:
# AES128_CBC
ciphermod = AES
key_size = 16
elif enc_oid == _OID_AES192_CBC:
# AES192_CBC
ciphermod = AES
key_size = 24
elif enc_oid == _OID_AES256_CBC:
# AES256_CBC
ciphermod = AES
key_size = 32
else:
raise PbesError("Unsupported PBES2 cipher")
if kdf_key_length and kdf_key_length != key_size:
raise PbesError("Mismatch between PBES2 KDF parameters"
" and selected cipher")
IV = DerOctetString().decode(enc_info[1]).payload
# Create cipher
if kdf_oid == _OID_PBKDF2:
if pbkdf2_prf_oid == _OID_HMAC_SHA1:
hmac_hash_module = SHA1
elif pbkdf2_prf_oid == _OID_HMAC_SHA224:
hmac_hash_module = SHA224
elif pbkdf2_prf_oid == _OID_HMAC_SHA256:
hmac_hash_module = SHA256
elif pbkdf2_prf_oid == _OID_HMAC_SHA384:
hmac_hash_module = SHA384
elif pbkdf2_prf_oid == _OID_HMAC_SHA512:
hmac_hash_module = SHA512
else:
raise PbesError("Unsupported HMAC %s" % pbkdf2_prf_oid)
key = PBKDF2(passphrase,
salt,
key_size,
iteration_count,
hmac_hash_module=hmac_hash_module)
else:
key = scrypt(passphrase, salt, key_size, iteration_count, scrypt_r,
scrypt_p)
cipher = ciphermod.new(key, ciphermod.MODE_CBC, IV)
# Decrypt data
pt = cipher.decrypt(encrypted_data)
return unpad(pt, cipher.block_size)
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).
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):
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 :mod:`Cryptodome.Random`.
Return:
The PKCS#8-wrapped private key (possibly encrypted), as a byte string.
"""
if key_params is None:
key_params = DerNull()
#
# PrivateKeyInfo ::= SEQUENCE {
# version Version,
# privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
# privateKey PrivateKey,
# attributes [0] IMPLICIT Attributes OPTIONAL
# }
#
pk_info = DerSequence([
0,
DerSequence([DerObjectId(key_oid), key_params]),
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 _EMSA_PKCS1_V1_5_ENCODE(msg_hash, emLen, with_hash_parameters=True):
"""
Implement the ``EMSA-PKCS1-V1_5-ENCODE`` function, as defined
in PKCS#1 v2.1 (RFC3447, 9.2).
``_EMSA-PKCS1-V1_5-ENCODE`` actually accepts the message ``M`` as input,
and hash it internally. Here, we expect that the message has already
been hashed instead.
:Parameters:
msg_hash : hash object
The hash object that holds the digest of the message being signed.
emLen : int
The length the final encoding must have, in bytes.
with_hash_parameters : bool
If True (default), include NULL parameters for the hash
algorithm in the ``digestAlgorithm`` SEQUENCE.
:attention: the early standard (RFC2313) stated that ``DigestInfo``
had to be BER-encoded. This means that old signatures
might have length tags in indefinite form, which
is not supported in DER. Such encoding cannot be
reproduced by this function.
:Return: An ``emLen`` byte long string that encodes the hash.
"""
# First, build the ASN.1 DER object DigestInfo:
#
# DigestInfo ::= SEQUENCE {
# digestAlgorithm AlgorithmIdentifier,
# digest OCTET STRING
# }
#
# where digestAlgorithm identifies the hash function and shall be an
# algorithm ID with an OID in the set PKCS1-v1-5DigestAlgorithms.
#
# PKCS1-v1-5DigestAlgorithms ALGORITHM-IDENTIFIER ::= {
# { OID id-md2 PARAMETERS NULL }|
# { OID id-md5 PARAMETERS NULL }|
# { OID id-sha1 PARAMETERS NULL }|
# { OID id-sha256 PARAMETERS NULL }|
# { OID id-sha384 PARAMETERS NULL }|
# { OID id-sha512 PARAMETERS NULL }
# }
#
# Appendix B.1 also says that for SHA-1/-2 algorithms, the parameters
# should be omitted. They may be present, but when they are, they shall
# have NULL value.
digestAlgo = DerSequence([DerObjectId(msg_hash.oid).encode()])
if with_hash_parameters:
digestAlgo.append(DerNull().encode())
digest = DerOctetString(msg_hash.digest())
digestInfo = DerSequence([digestAlgo.encode(), digest.encode()]).encode()
# We need at least 11 bytes for the remaining data: 3 fixed bytes and
# at least 8 bytes of padding).
if emLen < len(digestInfo) + 11:
raise TypeError(
"Selected hash algorith has a too long digest (%d bytes)." %
len(digest))
PS = b'\xFF' * (emLen - len(digestInfo) - 3)
return b'\x00\x01' + PS + b'\x00' + digestInfo
def testErrDecode1(self):
# No leftovers allowed
der = DerOctetString()
self.assertRaises(ValueError, der.decode, b('\x04\x01\x01\xff'))
raise ValueError("Not a valid PrivateKeyInfo SEQUENCE")
# PrivateKeyAlgorithmIdentifier ::= AlgorithmIdentifier
#
# EncryptedPrivateKeyInfo ::= SEQUENCE {
# encryptionAlgorithm EncryptionAlgorithmIdentifier,
# encryptedData EncryptedData
# }
# EncryptionAlgorithmIdentifier ::= AlgorithmIdentifier
# AlgorithmIdentifier ::= SEQUENCE {
# algorithm OBJECT IDENTIFIER,
# parameters ANY DEFINED BY algorithm OPTIONAL
# }
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]
# EncryptedData ::= OCTET STRING
private_key = DerOctetString().decode(pk_info[2]).payload
return (algo_oid, private_key, algo_params)
def testDecode2(self):
# Verify that decode returns the object
der = DerOctetString()
self.assertEqual(der, der.decode(b('\x04\x00')))
def testInit1(self):
der = DerOctetString(b('\xFF'))
self.assertEquals(der.encode(), b('\x04\x01\xFF'))
def decrypt(data, passphrase):
"""Decrypt a piece of data using a passphrase and *PBES2*.
The algorithm to use is automatically detected.
:Parameters:
data : byte string
The piece of data to decrypt.
passphrase : byte string
The passphrase to use for decrypting the data.
:Returns:
The decrypted data, as a binary string.
"""
enc_private_key_info = DerSequence().decode(data, nr_elements=2)
enc_algo = DerSequence().decode(enc_private_key_info[0])
encrypted_data = DerOctetString().decode(
enc_private_key_info[1]).payload
pbe_oid = DerObjectId().decode(enc_algo[0]).value
if pbe_oid != "1.2.840.113549.1.5.13":
raise PbesError("Not a PBES2 object")
pbes2_params = DerSequence().decode(enc_algo[1], nr_elements=2)
### Key Derivation Function selection
kdf_info = DerSequence().decode(pbes2_params[0], nr_elements=2)
kdf_oid = DerObjectId().decode(kdf_info[0]).value
# We only support PBKDF2 or scrypt
if kdf_oid == "1.2.840.113549.1.5.12":
pbkdf2_params = DerSequence().decode(kdf_info[1],
nr_elements=(2, 3, 4))
salt = DerOctetString().decode(pbkdf2_params[0]).payload
iteration_count = pbkdf2_params[1]
if len(pbkdf2_params) > 2:
kdf_key_length = pbkdf2_params[2]
else:
kdf_key_length = None
if len(pbkdf2_params) > 3:
raise PbesError("Unsupported PRF for PBKDF2")
elif kdf_oid == "1.3.6.1.4.1.11591.4.11":
scrypt_params = DerSequence().decode(kdf_info[1],
nr_elements=(4, 5))
salt = DerOctetString().decode(scrypt_params[0]).payload
iteration_count, scrypt_r, scrypt_p = [
scrypt_params[x] for x in (1, 2, 3)
]
if len(scrypt_params) > 4:
kdf_key_length = scrypt_params[4]
else:
kdf_key_length = None
else:
raise PbesError("Unsupported PBES2 KDF")
### Cipher selection
enc_info = DerSequence().decode(pbes2_params[1])
enc_oid = DerObjectId().decode(enc_info[0]).value
if enc_oid == "1.2.840.113549.3.7":
# DES_EDE3_CBC
ciphermod = DES3
key_size = 24
elif enc_oid == "2.16.840.1.101.3.4.1.2":
# AES128_CBC
ciphermod = AES
key_size = 16
elif enc_oid == "2.16.840.1.101.3.4.1.22":
# AES192_CBC
ciphermod = AES
key_size = 24
elif enc_oid == "2.16.840.1.101.3.4.1.42":
# AES256_CBC
ciphermod = AES
key_size = 32
else:
raise PbesError("Unsupported PBES2 cipher")
if kdf_key_length and kdf_key_length != key_size:
raise PbesError("Mismatch between PBES2 KDF parameters"
" and selected cipher")
IV = DerOctetString().decode(enc_info[1]).payload
# Create cipher
if kdf_oid == "1.2.840.113549.1.5.12": # PBKDF2
key = PBKDF2(passphrase, salt, key_size, iteration_count)
else:
key = scrypt(passphrase, salt, key_size, iteration_count, scrypt_r,
scrypt_p)
cipher = ciphermod.new(key, ciphermod.MODE_CBC, IV)
# Decrypt data
pt = cipher.decrypt(encrypted_data)
return unpad(pt, cipher.block_size)
def testInit1(self):
der = DerOctetString(b('\xFF'))
self.assertEquals(der.encode(), b('\x04\x01\xFF'))
def testDecode2(self):
# Verify that decode returns the object
der = DerOctetString()
self.assertEqual(der, der.decode(b('\x04\x00')))
