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#!/usr/bin/env python3
## Adapted from https://github.com/DoubleLabyrinth/how-does-SecureCRT-encrypt-password
import os
from Crypto.Hash import SHA256
from Crypto.Cipher import AES, Blowfish
class SecureCRTCrypto:
def __init__(self):
'''
Initialize SecureCRTCrypto object.
'''
self.IV = b'\x00' * Blowfish.block_size
self.Key1 = b'\x24\xA6\x3D\xDE\x5B\xD3\xB3\x82\x9C\x7E\x06\xF4\x08\x16\xAA\x07'
self.Key2 = b'\x5F\xB0\x45\xA2\x94\x17\xD9\x16\xC6\xC6\xA2\xFF\x06\x41\x82\xB7'
def Encrypt(self, Plaintext : str):
'''
Encrypt plaintext and return corresponding ciphertext.
Args:
Plaintext: A string that will be encrypted.
Returns:
Hexlified ciphertext string.
'''
plain_bytes = Plaintext.encode('utf-16-le')
plain_bytes += b'\x00\x00'
padded_plain_bytes = plain_bytes + os.urandom(Blowfish.block_size - len(plain_bytes) % Blowfish.block_size)
cipher1 = Blowfish.new(self.Key1, Blowfish.MODE_CBC, IV = self.IV)
cipher2 = Blowfish.new(self.Key2, Blowfish.MODE_CBC, IV = self.IV)
return cipher1.encrypt(os.urandom(4) + cipher2.encrypt(padded_plain_bytes) + os.urandom(4)).hex()
def Decrypt(self, Ciphertext : str):
'''
Decrypt ciphertext and return corresponding plaintext.
Args:
Ciphertext: A hex string that will be decrypted.
Returns:
Plaintext string.
'''
cipher1 = Blowfish.new(self.Key1, Blowfish.MODE_CBC, IV = self.IV)
cipher2 = Blowfish.new(self.Key2, Blowfish.MODE_CBC, IV = self.IV)
ciphered_bytes = bytes.fromhex(Ciphertext)
if len(ciphered_bytes) <= 8:
raise ValueError('Invalid Ciphertext.')
padded_plain_bytes = cipher2.decrypt(cipher1.decrypt(ciphered_bytes)[4:-4])
i = 0
for i in range(0, len(padded_plain_bytes), 2):
if padded_plain_bytes[i] == 0 and padded_plain_bytes[i + 1] == 0:
break
plain_bytes = padded_plain_bytes[0:i]
try:
return plain_bytes.decode('utf-16-le')
except UnicodeDecodeError:
raise(ValueError('Invalid Ciphertext.'))
class SecureCRTCryptoV2:
def __init__(self, ConfigPassphrase : str = ''):
'''
Initialize SecureCRTCryptoV2 object.
Args:
ConfigPassphrase: The config passphrase that SecureCRT uses. Leave it empty if config passphrase is not set.
'''
self.IV = b'\x00' * AES.block_size
self.Key = SHA256.new(ConfigPassphrase.encode('utf-8')).digest()
def Encrypt(self, Plaintext : str):
'''
Encrypt plaintext and return corresponding ciphertext.
Args:
Plaintext: A string that will be encrypted.
Returns:
Hexlified ciphertext string.
'''
plain_bytes = Plaintext.encode('utf-8')
if len(plain_bytes) > 0xffffffff:
raise OverflowError('Plaintext is too long.')
plain_bytes = \
len(plain_bytes).to_bytes(4, 'little') + \
plain_bytes + \
SHA256.new(plain_bytes).digest()
padded_plain_bytes = \
plain_bytes + \
os.urandom(AES.block_size - len(plain_bytes) % AES.block_size)
cipher = AES.new(self.Key, AES.MODE_CBC, IV = self.IV)
return cipher.encrypt(padded_plain_bytes).hex()
def Decrypt(self, Ciphertext : str):
'''
Decrypt ciphertext and return corresponding plaintext.
Args:
Ciphertext: A hex string that will be decrypted.
Returns:
Plaintext string.
'''
cipher = AES.new(self.Key, AES.MODE_CBC, IV = self.IV)
padded_plain_bytes = cipher.decrypt(bytes.fromhex(Ciphertext))
plain_bytes_length = int.from_bytes(padded_plain_bytes[0:4], 'little')
plain_bytes = padded_plain_bytes[4:4 + plain_bytes_length]
if len(plain_bytes) != plain_bytes_length:
raise ValueError('Invalid Ciphertext.')
plain_bytes_digest = padded_plain_bytes[4 + plain_bytes_length:4 + plain_bytes_length + SHA256.digest_size]
if len(plain_bytes_digest) != SHA256.digest_size:
raise ValueError('Invalid Ciphertext.')
if SHA256.new(plain_bytes).digest() != plain_bytes_digest:
raise ValueError('Invalid Ciphertext.')
return plain_bytes.decode('utf-8')
if __name__ == '__main__':
import sys
def Help():
print('Usage:')
print(' SecureCRTCipher.py <enc|dec> [-v2] [-p ConfigPassphrase] <plaintext|ciphertext>')
print('')
print(' <enc|dec> "enc" for encryption, "dec" for decryption.')
print(' This parameter must be specified.')
print('')
print(' [-v2] Encrypt/Decrypt with "Password V2" algorithm.')
print(' This parameter is optional.')
print('')
print(' [-p ConfigPassphrase] The config passphrase that SecureCRT uses.')
print(' This parameter is optional.')
print('')
print(' <plaintext|ciphertext> Plaintext string or ciphertext string.')
print(' NOTICE: Ciphertext string must be a hex string.')
print(' This parameter must be specified.')
print('')
def EncryptionRoutine(UseV2 : bool, ConfigPassphrase : str, Plaintext : str):
try:
if UseV2:
print(SecureCRTCryptoV2(ConfigPassphrase).Encrypt(Plaintext))
else:
print(SecureCRTCrypto().Encrypt(Plaintext))
return True
except:
raise
print('Error: Failed to encrypt.')
return False
def DecryptionRoutine(UseV2 : bool, ConfigPassphrase : str, Ciphertext : str):
try:
if UseV2:
print(SecureCRTCryptoV2(ConfigPassphrase).Decrypt(Ciphertext))
else:
print(SecureCRTCrypto().Decrypt(Ciphertext))
return True
except:
raise
print('Error: Failed to decrypt.')
return False
def Main(argc : int, argv : list):
if 3 <= argc and argc <= 6:
bUseV2 = False
ConfigPassphrase = ''
if argv[1].lower() == 'enc':
bEncrypt = True
elif argv[1].lower() == 'dec':
bEncrypt = False
else:
Help()
return -1
i = 2
while i < argc - 1:
if argv[i].lower() == '-v2':
bUseV2 = True
i += 1
elif argv[i].lower() == '-p' and i + 1 < argc - 1:
ConfigPassphrase = argv[i + 1]
i += 2
else:
Help()
return -1
if bUseV2 == False and len(ConfigPassphrase) != 0:
print('Error: ConfigPassphrase is not supported if "-v2" is not specified')
return -1
if bEncrypt:
return 0 if EncryptionRoutine(bUseV2, ConfigPassphrase, argv[-1]) else -1
else:
return 0 if DecryptionRoutine(bUseV2, ConfigPassphrase, argv[-1]) else -1
else:
Help()
exit(Main(len(sys.argv), sys.argv))