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how-does-Xmanager-encrypt-password.md

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How does Xmanager encrypt password?

After disassembling Xmanager by IDA, I found Xmanager uses a stream cipher to encrypt password. The stream cipher is an RC4 stream cipher. The following will tell you what Xmanager did:

1. Generate key.

Based on the version of session files, the key is generated by different algorithms.

1.1 For session file version < 5.1

Both Xshell and Xftp use MD5 algorithm to generate the key that is used in RC4 cipher.

  1. Xshell use the MD5 digest, 16 bytes long, of an ASCII string, "!X@s#h$e%l^l&", as RC4 cipher key. The value is

    // Key = MD5("!X@s#h$e%l^l&");
unsigned char Key[16] = {
    0xba, 0x2d, 0x9b, 0x7e, 0x9c, 0xca, 0x73, 0xd1, 
    0x52, 0xb2, 0x67, 0x72, 0x66, 0x2d, 0xf5, 0x5e
};

  2. Xftp use the MD5 digest, 16 bytes long, of an ASCII string, "!X@s#c$e%l^l&" which only has one different char with the string in Xshell, as RC4 cipher key. The value is

    // Key = MD5("!X@s#c$e%l^l&");
unsigned char Key[16] = {
    0x30, 0x6e, 0x98, 0x35, 0xde, 0x92, 0x91, 0xd2, 
    0x27, 0xbb, 0x28, 0xb2, 0xf7, 0x2d, 0xca, 0x33
};

1.2 For session file version == 5.1 or 5.2

Both XShell and XFtp use SHA-256 algorithm to generate key.

The key is the SHA-256 digest, 32 bytes long, of current OS account's SID string. You can use whoami /user in Command Prompt to check your current OS account's SID string.

For example, if your current OS account's SID string is

S-1-5-21-917267712-1342860078-1792151419-512

the 32-bytes-long SHA-256 digest would be

unsigned char Key[32] = {
    0xCE, 0x97, 0xBE, 0xA9, 0x0C, 0x2A, 0x40, 0xB9,
    0x5C, 0xC0, 0x79, 0x74, 0x1D, 0xDC, 0x03, 0xCB,
    0x39, 0xAB, 0x3D, 0xE5, 0x26, 0x7A, 0x3B, 0x11,
    0x05, 0x4B, 0x96, 0x3C, 0x93, 0x6F, 0x9C, 0xD4
};

1.3 For session file version > 5.2

This situation is similar with the former one (version 5.1 or 5.2).

The key is the SHA-256 digest of the combination of current OS account's name(case sensitive) and current OS account's SID string.

For example, if your current OS account's name and SID are

Administrator
S-1-5-21-917267712-1342860078-1792151419-512

the key is the 32-bytes-long SHA-256 digest of a string "AdministratorS-1-5-21-917267712-1342860078-1792151419-512":

unsigned char Key[32] = {
    0x8E, 0x12, 0x29, 0xDC, 0x1F, 0x34, 0x56, 0xB9,
    0xBB, 0xCD, 0x94, 0xC2, 0xAB, 0x0A, 0xF3, 0xB9,
    0x95, 0x96, 0x6F, 0x06, 0xE3, 0x9D, 0x24, 0x80,
    0x6A, 0x74, 0xCD, 0x7E, 0x0B, 0x69, 0xB3, 0x78
};

1.4 For the case where user has set a master password

The key is the SHA-256 digest of the master key set by user.

For example, if I set master password with "123123", the key that is used in RC4 cipher is

unsigned char Key[32] = {
    0x96, 0xca, 0xe3, 0x5c, 0xe8, 0xa9, 0xb0, 0x24, 
    0x41, 0x78, 0xbf, 0x28, 0xe4, 0x96, 0x6c, 0x2c, 
    0xe1, 0xb8, 0x38, 0x57, 0x23, 0xa9, 0x6a, 0x6b, 
    0x83, 0x88, 0x58, 0xcd, 0xd6, 0xca, 0x0a, 0x1e
};

2. Calculate SHA-256 digest of original password.

This step will be executed for session file version >= 5.1 only.

If your original password is "This is a test", the SHA-256 digest would be:

unsigned char Checksum[32] = {
    0xC7, 0xBE, 0x1E, 0xD9, 0x02, 0xFB, 0x8D, 0xD4,
    0xD4, 0x89, 0x97, 0xC6, 0x45, 0x2F, 0x5D, 0x7E,
    0x50, 0x9F, 0xBC, 0xDB, 0xE2, 0x80, 0x8B, 0x16,
    0xBC, 0xF4, 0xED, 0xCE, 0x4C, 0x07, 0xD1, 0x4E
};

This 32-bytes-long data will be regarded as the checksum and appended to the encrypted password.

3. Initialize cipher.

Xmanager use the key generated to initialize RC4 cipher.

4. Encrypt password.

Xmanager use the initialized RC4 cipher encrypt original password.

If original password is "This is a test", the result would be

4.1 For session file version < 5.1

  1. Encrypted by XShell

    unsigned char EncryptedPassword[] = {
    0xff, 0xa2, 0x9a, 0x4e, 0xb2, 0xb0, 0x9b, 0x47, 
    0x26, 0x86, 0xbd, 0x32, 0x01, 0x64
};

  2. Encrypted by XFtp

    unsigned char EncryptedPassword[] = {
    0x4c, 0xf2, 0x92, 0x83, 0x44, 0x10, 0xea, 0x8e, 
    0xfd, 0xe6, 0xf9, 0xcf, 0x20, 0xcb
};

4.2 For session file version == 5.1 OR 5.2

unsigned char EncryptedPassword[] = {
    0x84, 0x83, 0x31, 0x23, 0x24, 0x37, 0x1D, 0xB2,
    0x6C, 0x54, 0x87, 0x5B, 0x6E, 0xE9
};

4.3 For session file version > 5.2

unsigned char EncryptedPassword[] = {
    0xCE, 0xFD, 0xB5, 0x3B, 0x5C, 0x78, 0xDE, 0xA4,
    0x6C, 0xDD, 0xCE, 0x4D, 0x72, 0x40
};

4.4 For the case where user has set a master password

unsigned char EncryptedPassword[] = {
    0x46, 0xb9, 0xb7, 0x3f, 0x70, 0x0b, 0xd2, 0x20, 
    0xd5, 0xee, 0x70, 0x5b, 0x4b, 0x66
};

5. Append checksum to encrypted password.

This step will be executed for session file version >= 5.1 only.

5.1 For session file version == 5.1 or 5.2

unsigned char FinalResult[] = {
    0x84, 0x83, 0x31, 0x23, 0x24, 0x37, 0x1D, 0xB2,
    0x6C, 0x54, 0x87, 0x5B, 0x6E, 0xE9, 0xC7, 0xBE,
    0x1E, 0xD9, 0x02, 0xFB, 0x8D, 0xD4, 0xD4, 0x89,
    0x97, 0xC6, 0x45, 0x2F, 0x5D, 0x7E, 0x50, 0x9F,
    0xBC, 0xDB, 0xE2, 0x80, 0x8B, 0x16, 0xBC, 0xF4,
    0xED, 0xCE, 0x4C, 0x07, 0xD1, 0x4E
};

5.2 For session file version > 5.2

unsigned char FinalResult[] = {
    0xCE, 0xFD, 0xB5, 0x3B, 0x5C, 0x78, 0xDE, 0xA4,
    0x6C, 0xDD, 0xCE, 0x4D, 0x72, 0x40, 0xC7, 0xBE,
    0x1E, 0xD9, 0x02, 0xFB, 0x8D, 0xD4, 0xD4, 0x89,
    0x97, 0xC6, 0x45, 0x2F, 0x5D, 0x7E, 0x50, 0x9F,
    0xBC, 0xDB, 0xE2, 0x80, 0x8B, 0x16, 0xBC, 0xF4,
    0xED, 0xCE, 0x4C, 0x07, 0xD1, 0x4E
};

5.3 For the case where user has set a master password

unsigned char FinalResult[] = {
    0x46, 0xb9, 0xb7, 0x3f, 0x70, 0x0b, 0xd2, 0x20, 
    0xd5, 0xee, 0x70, 0x5b, 0x4b, 0x66, 0xC7, 0xBE,
    0x1E, 0xD9, 0x02, 0xFB, 0x8D, 0xD4, 0xD4, 0x89,
    0x97, 0xC6, 0x45, 0x2F, 0x5D, 0x7E, 0x50, 0x9F,
    0xBC, 0xDB, 0xE2, 0x80, 0x8B, 0x16, 0xBC, 0xF4,
    0xED, 0xCE, 0x4C, 0x07, 0xD1, 0x4E
};

6. Convert final result to Base64 format.

Convert final result to Base64 format. Then the base64 string will be stored into session file.

6.1 For session file version < 5.1

  1. XShell

    /6KaTrKwm0cmhr0yAWQ=

  2. XFtp

    TPKSg0QQ6o795vnPIMs=

6.2 For session file version == 5.1 or 5.2

hIMxIyQ3HbJsVIdbbunHvh7ZAvuN1NSJl8ZFL11+UJ+82+KAixa89O3OTAfRTg==

6.3 For session file version > 5.2

zv21O1x43qRs3c5NckDHvh7ZAvuN1NSJl8ZFL11+UJ+82+KAixa89O3OTAfRTg==

6.4 For the case where user has set a master password

Rrm3P3AL0iDV7nBbS2bHvh7ZAvuN1NSJl8ZFL11+UJ+82+KAixa89O3OTAfRTg==