cts/
ecb_cs1.rs

1use core::marker::PhantomData;
2
3use crate::{Decrypt, Encrypt, Error, ecb_dec, ecb_enc};
4use cipher::{
5    Block, BlockCipherDecBackend, BlockCipherDecClosure, BlockCipherDecrypt, BlockCipherEncBackend,
6    BlockCipherEncClosure, BlockCipherEncrypt, BlockSizeUser, IvSizeUser,
7    array::ArraySize,
8    common::{InnerInit, InnerUser},
9    inout::InOutBuf,
10    typenum::Unsigned,
11};
12
13/// The ECB-CS-1 ciphertext stealing mode.
14#[derive(Debug)]
15pub struct EcbCs1<C: BlockSizeUser> {
16    cipher: C,
17}
18
19impl<C: BlockSizeUser> InnerUser for EcbCs1<C> {
20    type Inner = C;
21}
22
23impl<C: BlockSizeUser> IvSizeUser for EcbCs1<C> {
24    type IvSize = C::BlockSize;
25}
26
27impl<C: BlockSizeUser> InnerInit for EcbCs1<C> {
28    fn inner_init(cipher: Self::Inner) -> Self {
29        Self { cipher }
30    }
31}
32
33impl<C: BlockCipherEncrypt> Encrypt for EcbCs1<C> {
34    fn encrypt_inout(self, buf: InOutBuf<'_, '_, u8>) -> Result<(), Error> {
35        if buf.len() < C::BlockSize::USIZE {
36            return Err(Error);
37        }
38        self.cipher.encrypt_with_backend(Closure {
39            buf,
40            _pd: PhantomData,
41        });
42        Ok(())
43    }
44}
45
46impl<C: BlockCipherDecrypt> Decrypt for EcbCs1<C> {
47    fn decrypt_inout(self, buf: InOutBuf<'_, '_, u8>) -> Result<(), Error> {
48        if buf.len() < C::BlockSize::USIZE {
49            return Err(Error);
50        }
51        self.cipher.decrypt_with_backend(Closure {
52            buf,
53            _pd: PhantomData,
54        });
55        Ok(())
56    }
57}
58
59struct Closure<'a, BS: ArraySize> {
60    buf: InOutBuf<'a, 'a, u8>,
61    _pd: PhantomData<BS>,
62}
63
64impl<BS: ArraySize> BlockSizeUser for Closure<'_, BS> {
65    type BlockSize = BS;
66}
67
68impl<BS: ArraySize> BlockCipherEncClosure for Closure<'_, BS> {
69    fn call<B: BlockCipherEncBackend<BlockSize = BS>>(self, cipher: &B) {
70        let mut buf = self.buf;
71        let (mut blocks, tail) = buf.reborrow().into_chunks();
72
73        ecb_enc(cipher, blocks.reborrow());
74
75        if tail.is_empty() {
76            return;
77        }
78
79        let last_block = blocks.get_out().last_mut().unwrap();
80        let mut block = Block::<B>::default();
81
82        let n = tail.len();
83
84        block[..n].copy_from_slice(tail.get_in());
85        block[n..].copy_from_slice(&last_block[n..]);
86        cipher.encrypt_block_inplace(&mut block);
87
88        let pos = buf.len() - block.len();
89        buf.get_out()[pos..].copy_from_slice(&block);
90    }
91}
92
93impl<BS: ArraySize> BlockCipherDecClosure for Closure<'_, BS> {
94    fn call<B: BlockCipherDecBackend<BlockSize = BS>>(self, cipher: &B) {
95        let mut buf = self.buf;
96        let (mut blocks, tail) = buf.reborrow().into_chunks();
97
98        if !tail.is_empty() {
99            let mid = blocks.len() - 1;
100            blocks = blocks.split_at(mid).0;
101        };
102
103        ecb_dec(cipher, blocks);
104
105        if tail.is_empty() {
106            return;
107        }
108
109        let tail_len = tail.len();
110        let bs = B::BlockSize::USIZE;
111        let mid = buf.len() - (bs + tail_len);
112        let mut rem = buf.split_at(mid).1;
113
114        let n = rem.len() - bs;
115        let mut block1: Block<B> = rem.get_in()[..bs].try_into().unwrap();
116        let mut block2: Block<B> = rem.get_in()[n..].try_into().unwrap();
117
118        cipher.decrypt_block_inplace(&mut block2);
119        block1[n..].copy_from_slice(&block2[n..]);
120
121        cipher.decrypt_block_inplace(&mut block1);
122
123        rem.get_out()[..bs].copy_from_slice(&block1);
124        rem.get_out()[bs..].copy_from_slice(&block2[..n]);
125    }
126}
cts/ecb_cs1.rs

cts/
ecb_cs1.rs
