#!/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 [-v2] [-p ConfigPassphrase] ') print('') print(' "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 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))