再看SecureCRT密码解密

2019年12月27日 发表评论 阅读评论

在《python3解密SecureCRT的密码》篇中提到了利用python进行SecureCRT加密后的密文进行解密的方法。但在不同版本的SecureCRT中%APPDATA%\VanDyke\Config\Sessions\example.com.ini配置中对应的password可能是不一样的,有些密码存储在password项,有些存储的是Password V2项,具体类似如下:

S:"Password"=u17cf50e394ecc2a06fa8919e1bd67cf0f37da34c78e7eb87a3a9a787a9785e802dd0eae4e8039c3ce234d34bfe28bbdc
S:"Password V2"=02:7b9f594a1f39bb36bbaa0d9688ee38b3d233c67b338e20e2113f2ba4d328b6fc8c804e3c02324b1eaad57a5b96ac1fc5cc1ae0ee2930e6af2e5e644a28ebe3fc

这两者之间的加解密方法是有区别的。具体一般以SecureCRT 7.3.3版本进行分界。之前的版本一般会使用password加密算法,之后的一般使用password v2算法。

一、Password算法

这个也是开篇链接中我之前的博文中提到的,其使用的是2次Blowfish-CBC加密,这里记录为cipher1和cipher2。两者使用的初始公共因子是8位的16进制的0,具体表示如下:

uint8_t IV[8] = {
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
}

cipher1 使用的key是:

uint8_t Key1[16] = {
    0x24, 0xa6, 0x3d, 0xde, 0x5b, 0xd3, 0xb3, 0x82,
    0x9c, 0x7e, 0x06, 0xf4, 0x08, 0x16, 0xaa, 0x07
}

cipher2 使用的key是:

uint8_t Key2[16] = {
    0x5f, 0xb0, 0x45, 0xa2, 0x94, 0x17, 0xd9, 0x16,
    0xc6, 0xc6, 0xa2, 0xff, 0x06, 0x41, 0x82, 0xb7
}

其加密过程如下:

scrt-password-encrypt

同样对应的其解密过程如下:

scrt-password-decry

二、password v2算法

password v2使用的是AES256-CBC 算法,其初始因子是16位16进制的0,具体如下:

uint8_t IV[16] = {
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
}

其使用的32位key是:

uint8_t Key[32] = {
    0xe3, 0xb0, 0xc4, 0x42, 0x98, 0xfc, 0x1c, 0x14,
    0x9a, 0xfb, 0xf4, 0xc8, 0x99, 0x6f, 0xb9, 0x24,
    0x27, 0xae, 0x41, 0xe4, 0x64, 0x9b, 0x93, 0x4c,
    0xa4, 0x95, 0x99, 0x1b, 0x78, 0x52, 0xb8, 0x55
}

对应的加密过程是:

passwordv2-encryption

对应的解密过程如下:

passwordv2-decryption

三、解密代码

这里还是以python为例,对应的即可以解密password也可以解密password v2的代码如下:

#!/usr/bin/env python3
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:
            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:
            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))

该脚本需要依赖pycryptodome模块,该模块是一个加解密算法的模块包,该模块是pyCyrpto模块的延续。由于pyCyrpto在python3.4已停止更新。后面新的版本就变成了pycryptodome。




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