libs.nfc_rs/src/crypto/cipher_key.rs

use crate::crypto::cipher_type::CipherType;
use crate::crypto::cipher_type::CipherType::*;
use crate::crypto::cipher::{aes, tdes, tdes_2k, tdes_3k};
use crate::error::Error;
use crate::error::Result;

use simple_error::simple_error;

#[derive(Debug, Clone)]
struct CipherKey {
    /// Key as Array
    key: Box<[u8]>,

    /// CipherType of Key
    cipher: CipherType,

    /// KeyVersion of Key
    key_version: u8
}

impl CipherKey {
    pub fn new(key: &[u8], cipher: CipherType, key_version: u8) -> Result<CipherKey> {
        if cipher == AES && key_version < 0x10 {
            return Err(Error::Boxed(Box::new(simple_error!("KeyVersion is to low for AES Key (Minimum = 0x10)"))))
        }

        if !check_key(key, cipher.clone()) {
            return Err(Error::Boxed(Box::new(simple_error!("Key is not valid for CipherType"))))
        }

        let mut key: Box<[u8]> = Box::from(key);
        if cipher == TDES || cipher == TDES2K || cipher == TDES3K {
            key = set_key_version(key.as_ref(), key_version);
        }

        Ok(CipherKey {
            cipher,
            key_version,
            key
        })
    }

    pub fn new_from_str(key: &str, cipher: CipherType, key_version: u8) -> Result<CipherKey> {
        CipherKey::new(&*hex::decode(key)?, cipher, key_version)
    }

    pub fn new_empty(cipher: CipherType) -> Result<CipherKey> {
        Ok(CipherKey{
            key: generate_empty_key(cipher.clone()),
            key_version: if cipher == AES { 0x10u8 } else { 0x00u8 },
            cipher
        })
    }
}

/// Generate Empty Key for CipherType
pub fn generate_empty_key(cipher: CipherType) -> Box<[u8]> {
    let size = get_key_size(cipher);

    vec![0u8; size].into_boxed_slice()
}

/// Get KeySize for CipherType
pub fn get_key_size(cipher: CipherType) -> usize {
    match cipher {
        TDES => tdes::KEY_LEN,
        TDES2K => tdes_2k::KEY_LEN,
        TDES3K => tdes_3k::KEY_LEN,
        AES => aes::KEY_LEN
    }
}

/// Check Key Slice
pub fn check_key(key: &[u8], cipher: CipherType) -> bool {
    if key.len() != get_key_size(cipher) { false } else { true }
}

/// Set Key Version for DES/TDES Keys
/// KeyVersion is stored in the LSBits of the first 8 Bytes
/// Parity Bits are not used from DESFire Cars

pub fn set_key_version(key: &[u8], version: u8) -> Box<[u8]> {
    let pow2 = [0x01u8, 0x02u8, 0x04u8, 0x08u8, 0x10u8, 0x20u8, 0x40u8, 0x80u8];

    let mut new_key = key.to_vec();

    for i in 0..8 {
        if (version & pow2[i]) > 0 {
            new_key[i] = (new_key[5] | 0x01u8) as u8;
        } else {
            new_key[i] = (new_key[5] & 0x7fu8) as u8;
        }
    }
    new_key.into_boxed_slice()
}