cbc 0.2.0

Cipher Block Chaining (CBC) block cipher mode of operation
Documentation 
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use crate::xor;
use cipher::{
    AlgorithmName, Array, Block, BlockCipherEncBackend, BlockCipherEncClosure, BlockCipherEncrypt,
    BlockModeEncBackend, BlockModeEncClosure, BlockModeEncrypt, BlockSizeUser, InOut, InnerIvInit,
    Iv, IvSizeUser, IvState, ParBlocksSizeUser, array::ArraySize, common::InnerUser, consts::U1,
};
use core::fmt;

#[cfg(feature = "zeroize")]
use cipher::zeroize::{Zeroize, ZeroizeOnDrop};

/// CBC mode encryptor.
pub struct Encryptor<C>
where
    C: BlockCipherEncrypt,
{
    cipher: C,
    iv: Block<C>,
}

impl<C> BlockSizeUser for Encryptor<C>
where
    C: BlockCipherEncrypt,
{
    type BlockSize = C::BlockSize;
}

impl<C> InnerUser for Encryptor<C>
where
    C: BlockCipherEncrypt,
{
    type Inner = C;
}

impl<C> IvSizeUser for Encryptor<C>
where
    C: BlockCipherEncrypt,
{
    type IvSize = C::BlockSize;
}

impl<C> InnerIvInit for Encryptor<C>
where
    C: BlockCipherEncrypt,
{
    #[inline]
    fn inner_iv_init(cipher: C, iv: &Iv<Self>) -> Self {
        Self {
            cipher,
            iv: iv.clone(),
        }
    }
}

impl<C> IvState for Encryptor<C>
where
    C: BlockCipherEncrypt,
{
    #[inline]
    fn iv_state(&self) -> Iv<Self> {
        self.iv.clone()
    }
}

impl<C> BlockModeEncrypt for Encryptor<C>
where
    C: BlockCipherEncrypt,
{
    fn encrypt_with_backend(&mut self, f: impl BlockModeEncClosure<BlockSize = Self::BlockSize>) {
        struct Closure<'a, BS, BC>
        where
            BS: ArraySize,
            BC: BlockModeEncClosure<BlockSize = BS>,
        {
            iv: &'a mut Array<u8, BS>,
            f: BC,
        }

        impl<BS, BC> BlockSizeUser for Closure<'_, BS, BC>
        where
            BS: ArraySize,
            BC: BlockModeEncClosure<BlockSize = BS>,
        {
            type BlockSize = BS;
        }

        impl<BS, BC> BlockCipherEncClosure for Closure<'_, BS, BC>
        where
            BS: ArraySize,
            BC: BlockModeEncClosure<BlockSize = BS>,
        {
            #[inline(always)]
            fn call<B: BlockCipherEncBackend<BlockSize = Self::BlockSize>>(
                self,
                cipher_backend: &B,
            ) {
                let Self { iv, f } = self;
                f.call(&mut Backend { iv, cipher_backend });
            }
        }

        let Self { cipher, iv } = self;
        cipher.encrypt_with_backend(Closure { iv, f });
    }
}

impl<C> AlgorithmName for Encryptor<C>
where
    C: BlockCipherEncrypt + AlgorithmName,
{
    fn write_alg_name(f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("cbc::Encryptor<")?;
        <C as AlgorithmName>::write_alg_name(f)?;
        f.write_str(">")
    }
}

impl<C> fmt::Debug for Encryptor<C>
where
    C: BlockCipherEncrypt + AlgorithmName,
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("cbc::Encryptor<")?;
        <C as AlgorithmName>::write_alg_name(f)?;
        f.write_str("> { ... }")
    }
}

impl<C: BlockCipherEncrypt> Drop for Encryptor<C> {
    fn drop(&mut self) {
        #[cfg(feature = "zeroize")]
        self.iv.zeroize();
    }
}

#[cfg(feature = "zeroize")]
impl<C: BlockCipherEncrypt + ZeroizeOnDrop> ZeroizeOnDrop for Encryptor<C> {}

struct Backend<'a, BS, BK>
where
    BS: ArraySize,
    BK: BlockCipherEncBackend<BlockSize = BS>,
{
    iv: &'a mut Array<u8, BS>,
    cipher_backend: &'a BK,
}

impl<BS, BK> BlockSizeUser for Backend<'_, BS, BK>
where
    BS: ArraySize,
    BK: BlockCipherEncBackend<BlockSize = BS>,
{
    type BlockSize = BS;
}

impl<BS, BK> ParBlocksSizeUser for Backend<'_, BS, BK>
where
    BS: ArraySize,
    BK: BlockCipherEncBackend<BlockSize = BS>,
{
    type ParBlocksSize = U1;
}

impl<BS, BK> BlockModeEncBackend for Backend<'_, BS, BK>
where
    BS: ArraySize,
    BK: BlockCipherEncBackend<BlockSize = BS>,
{
    #[inline(always)]
    fn encrypt_block(&mut self, mut block: InOut<'_, '_, Block<Self>>) {
        let mut t = block.clone_in();
        xor(&mut t, self.iv);
        self.cipher_backend.encrypt_block((&mut t).into());
        *self.iv = t.clone();
        *block.get_out() = t;
    }
}