ctr/flavors/
ctr32.rs

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1//! 32-bit counter falvors.
2use super::CtrFlavor;
3use cipher::{
4    generic_array::{ArrayLength, GenericArray},
5    typenum::{PartialDiv, PartialQuot, Unsigned, U4},
6};
7
8#[cfg(feature = "zeroize")]
9use cipher::zeroize::{Zeroize, ZeroizeOnDrop};
10
11type ChunkSize = U4;
12type Chunks<B> = PartialQuot<B, ChunkSize>;
13const CS: usize = ChunkSize::USIZE;
14
15#[derive(Clone)]
16pub struct CtrNonce32<N: ArrayLength<u32>> {
17    ctr: u32,
18    nonce: GenericArray<u32, N>,
19}
20
21#[cfg(feature = "zeroize")]
22impl<N: ArrayLength<u32>> Drop for CtrNonce32<N> {
23    fn drop(&mut self) {
24        self.ctr.zeroize();
25        self.nonce.zeroize();
26    }
27}
28
29#[cfg(feature = "zeroize")]
30impl<N: ArrayLength<u32>> ZeroizeOnDrop for CtrNonce32<N> {}
31
32/// 32-bit big endian counter flavor.
33pub enum Ctr32BE {}
34
35impl<B> CtrFlavor<B> for Ctr32BE
36where
37    B: ArrayLength<u8> + PartialDiv<ChunkSize>,
38    Chunks<B>: ArrayLength<u32>,
39{
40    type CtrNonce = CtrNonce32<Chunks<B>>;
41    type Backend = u32;
42    const NAME: &'static str = "32BE";
43
44    #[inline]
45    fn remaining(cn: &Self::CtrNonce) -> Option<usize> {
46        (core::u32::MAX - cn.ctr).try_into().ok()
47    }
48
49    #[inline(always)]
50    fn current_block(cn: &Self::CtrNonce) -> GenericArray<u8, B> {
51        let mut block = GenericArray::<u8, B>::default();
52        for i in 0..Chunks::<B>::USIZE {
53            let t = if i == Chunks::<B>::USIZE - 1 {
54                cn.ctr.wrapping_add(cn.nonce[i]).to_be_bytes()
55            } else {
56                cn.nonce[i].to_ne_bytes()
57            };
58            block[CS * i..][..CS].copy_from_slice(&t);
59        }
60        block
61    }
62
63    #[inline]
64    fn next_block(cn: &mut Self::CtrNonce) -> GenericArray<u8, B> {
65        let block = Self::current_block(cn);
66        cn.ctr = cn.ctr.wrapping_add(1);
67        block
68    }
69
70    #[inline]
71    fn from_nonce(block: &GenericArray<u8, B>) -> Self::CtrNonce {
72        let mut nonce = GenericArray::<u32, Chunks<B>>::default();
73        for i in 0..Chunks::<B>::USIZE {
74            let chunk = block[CS * i..][..CS].try_into().unwrap();
75            nonce[i] = if i == Chunks::<B>::USIZE - 1 {
76                u32::from_be_bytes(chunk)
77            } else {
78                u32::from_ne_bytes(chunk)
79            }
80        }
81        let ctr = 0;
82        Self::CtrNonce { ctr, nonce }
83    }
84
85    #[inline]
86    fn as_backend(cn: &Self::CtrNonce) -> Self::Backend {
87        cn.ctr
88    }
89
90    #[inline]
91    fn set_from_backend(cn: &mut Self::CtrNonce, v: Self::Backend) {
92        cn.ctr = v;
93    }
94}
95
96/// 32-bit big endian counter flavor.
97pub enum Ctr32LE {}
98
99impl<B> CtrFlavor<B> for Ctr32LE
100where
101    B: ArrayLength<u8> + PartialDiv<ChunkSize>,
102    Chunks<B>: ArrayLength<u32>,
103{
104    type CtrNonce = CtrNonce32<Chunks<B>>;
105    type Backend = u32;
106    const NAME: &'static str = "32LE";
107
108    #[inline]
109    fn remaining(cn: &Self::CtrNonce) -> Option<usize> {
110        (core::u32::MAX - cn.ctr).try_into().ok()
111    }
112
113    #[inline(always)]
114    fn current_block(cn: &Self::CtrNonce) -> GenericArray<u8, B> {
115        let mut block = GenericArray::<u8, B>::default();
116        for i in 0..Chunks::<B>::USIZE {
117            let t = if i == 0 {
118                cn.ctr.wrapping_add(cn.nonce[i]).to_le_bytes()
119            } else {
120                cn.nonce[i].to_ne_bytes()
121            };
122            block[CS * i..][..CS].copy_from_slice(&t);
123        }
124        block
125    }
126
127    #[inline]
128    fn next_block(cn: &mut Self::CtrNonce) -> GenericArray<u8, B> {
129        let block = Self::current_block(cn);
130        cn.ctr = cn.ctr.wrapping_add(1);
131        block
132    }
133
134    #[inline]
135    fn from_nonce(block: &GenericArray<u8, B>) -> Self::CtrNonce {
136        let mut nonce = GenericArray::<u32, Chunks<B>>::default();
137        for i in 0..Chunks::<B>::USIZE {
138            let chunk = block[CS * i..][..CS].try_into().unwrap();
139            nonce[i] = if i == 0 {
140                u32::from_le_bytes(chunk)
141            } else {
142                u32::from_ne_bytes(chunk)
143            }
144        }
145        let ctr = 0;
146        Self::CtrNonce { ctr, nonce }
147    }
148
149    #[inline]
150    fn as_backend(cn: &Self::CtrNonce) -> Self::Backend {
151        cn.ctr
152    }
153
154    #[inline]
155    fn set_from_backend(cn: &mut Self::CtrNonce, v: Self::Backend) {
156        cn.ctr = v;
157    }
158}
ctr/flavors/ctr32.rs

ctr/flavors/
ctr32.rs
