/
rsa.py
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/
rsa.py
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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
from ... import arg, Unit
from ....lib.tools import splitchunks
from ....lib.mscrypto import BCRYPT_RSAKEY_BLOB, CRYPTOKEY, TYPES
from ....lib.xml import ForgivingParse
from base64 import b64decode
from contextlib import suppress
from enum import IntEnum
from Crypto.Random import get_random_bytes
from Crypto.Cipher import PKCS1_OAEP
from Crypto.PublicKey import RSA
from Crypto.Util import number
def normalize_rsa_key(key):
try:
dom = ForgivingParse(key)
except ValueError:
pass
else:
data = {child.tag.upper(): number.bytes_to_long(b64decode(child.text)) for child in dom.getroot()}
components = (data['MODULUS'], data['EXPONENT'])
if 'D' in data:
components += data['D'],
if 'P' in data and 'Q' in data:
components += data['P'], data['Q']
return RSA.construct(components)
try:
blob = CRYPTOKEY(key)
except ValueError:
pass
else:
if blob.header.type not in {TYPES.PUBLICKEYBLOB, TYPES.PRIVATEKEYBLOB}:
raise ValueError(F'The provided key is of invalid type {blob.header.type!s}, the algorithm is {blob.header.algorithm!s}.')
return blob.key.convert()
try:
blob = BCRYPT_RSAKEY_BLOB(key)
except ValueError:
return RSA.import_key(key)
else:
return blob.convert()
class PAD(IntEnum):
AUTO = 0
NONE = 1
OAEP = 2
PKCS15 = 3
PKCS10 = 4
class rsa(Unit):
"""
Implements single block RSA encryption and decryption. This unit can be used to encrypt
and decrypt blocks generated by openssl's `rsautl` tool when using the mode `-verify`.
When it is executed with a public key for decryption or with a private key for encryption,
it will perform a raw RSA operation. The result of these operations are (un)padded using
EMSA-PKCS1-v1_5.
"""
def __init__(
self,
key: arg(help='RSA key in PEM, DER, or Microsoft BLOB format.'),
swapkeys: arg.switch('-s', help='Swap public and private exponent.') = False,
textbook: arg.switch('-t', group='PAD', help='Equivalent to --padding=NONE.') = False,
padding : arg.option('-p', group='PAD', choices=PAD,
help='Choose one of the following padding modes: {choices}. The default is AUTO.') = PAD.AUTO,
rsautl : arg.switch('-r', group='PAD',
help='Act as rsautl from OpenSSH; This is equivalent to --swapkeys --padding=PKCS10') = False,
):
padding = arg.as_option(padding, PAD)
if textbook:
if padding != PAD.AUTO:
raise ValueError('Conflicting padding options!')
padding = padding.NONE
if rsautl:
if padding and padding != PAD.PKCS10:
raise ValueError('Conflicting padding options!')
swapkeys = True
padding = PAD.PKCS10
super().__init__(key=key, textbook=textbook, padding=padding, swapkeys=swapkeys)
self._key_hash = None
self._key_data = None
@property
def blocksize(self) -> int:
return self.key.size_in_bytes()
@property
def _blocksize_plain(self) -> int:
# PKCS#1 v1.5 padding is at least 11 bytes.
return self.blocksize - 11
@property
def pub(self):
return self.key.d if self.args.swapkeys else self.key.e
@property
def prv(self):
return self.key.e if self.args.swapkeys else self.key.d
def _get_msg(self, data):
msg = int.from_bytes(data, byteorder='big')
if msg > self.key.n:
raise ValueError(F'This key can only handle messages of size {self.blocksize}.')
return msg
def _encrypt_raw(self, data):
return pow(
self._get_msg(data),
self.pub,
self.key.n
).to_bytes(self.blocksize, byteorder='big')
def _decrypt_raw(self, data):
return pow(
self._get_msg(data),
self.prv,
self.key.n
).to_bytes(self.blocksize, byteorder='big')
def _unpad(self, data, head, padbyte=None):
if len(data) > self.blocksize:
raise ValueError(F'This key can only handle messages of size {self.blocksize}.')
if data.startswith(head):
pos = data.find(B'\0', 2)
if pos > 0:
pad = data[2:pos]
if padbyte is None or all(b == padbyte for b in pad):
return data[pos + 1:]
raise ValueError('Incorrect padding')
def _pad(self, data, head, padbyte=None):
if len(data) > self._blocksize_plain:
raise ValueError(F'This key can only encrypt messages of size at most {self._blocksize_plain}.')
pad = self.blocksize - len(data) - len(head) - 1
if padbyte is not None:
padding = pad * bytes((padbyte,))
else:
padding = bytearray(1)
while not all(padding):
padding = bytearray(filter(None, padding))
padding.extend(get_random_bytes(pad - len(padding)))
return head + padding + B'\0' + data
def _unpad_pkcs10(self, data):
return self._unpad(data, B'\x00\x01', 0xFF)
def _unpad_pkcs15(self, data):
return self._unpad(data, B'\x00\x02', None)
def _pad_pkcs10(self, data):
return self._pad(data, B'\x00\x01', 0xFF)
def _pad_pkcs15(self, data):
return self._pad(data, B'\x00\x02', None)
def _decrypt_block_OAEP(self, data):
self.log_debug('Attempting decryption with PyCrypto PKCS1 OAEP.')
result = PKCS1_OAEP.new(self.key).decrypt(data)
if result is not None:
return result
raise ValueError('OAEP decryption was unsuccessful.')
def _encrypt_block_OAEP(self, data):
self.log_debug('Attempting encryption with PyCrypto PKCS1 OAEP.')
result = PKCS1_OAEP.new(self.key).encrypt(data)
if result is None:
return result
raise ValueError('OAEP encryption was unsuccessful.')
def _decrypt_block(self, data):
if self._oaep and self._pads in {PAD.AUTO, PAD.OAEP}:
try:
return self._decrypt_block_OAEP(data)
except ValueError:
if self._pads: raise
self.log_debug('PyCrypto primitives failed, no longer attempting OAEP.')
self._oaep = False
result = self._decrypt_raw(data)
if self._pads == PAD.NONE:
return result
elif self._pads == PAD.PKCS10:
return self._unpad_pkcs10(result)
elif self._pads == PAD.PKCS15:
return self._unpad_pkcs15(result)
elif self._pads == PAD.AUTO:
with suppress(ValueError):
data = self._unpad_pkcs10(result)
self.log_info('Detected PKCS1.0 padding.')
self._pads = PAD.PKCS10
return data
with suppress(ValueError):
data = self._unpad_pkcs15(result)
self.log_info('Detected PKCS1.5 padding.')
self._pads = PAD.PKCS15
return data
self.log_warn('No padding worked, returning raw decrypted blocks.')
self._pads = PAD.NONE
return result
else:
raise ValueError(F'Invalid padding value: {self._pads!r}')
def _encrypt_block(self, data):
if self._pads in {PAD.AUTO, PAD.OAEP}:
try:
return self._encrypt_block_OAEP(data)
except ValueError:
if self._pads: raise
self.log_debug('PyCrypto primitives for OAEP failed, falling back to PKCS1.5.')
self._pads = PAD.PKCS15
if self._pads == PAD.PKCS15:
data = self._pad_pkcs15(data)
elif self._pads == PAD.PKCS10:
data = self._pad_pkcs10(data)
return self._encrypt_raw(data)
@property
def key(self) -> RSA.RsaKey:
key_blob = self.args.key
key_hash = hash(key_blob)
if key_hash != self._key_hash:
self._key_hash = key_hash
self._key_data = normalize_rsa_key(key_blob)
return self._key_data
def process(self, data):
if not self.key.has_private():
try:
return self._unpad_pkcs10(self._encrypt_raw(data))
except Exception as E:
raise ValueError('A public key was given for decryption and rsautl mode resulted in an error.') from E
self._oaep = True
self._pads = self.args.padding
return B''.join(self._decrypt_block(block) for block in splitchunks(data, self.blocksize))
def reverse(self, data):
self._pads = self.args.padding
return B''.join(self._encrypt_block(block) for block in splitchunks(data, self._blocksize_plain))