ring/aead/
block.rs

1// Copyright 2018 Brian Smith.
2//
3// Permission to use, copy, modify, and/or distribute this software for any
4// purpose with or without fee is hereby granted, provided that the above
5// copyright notice and this permission notice appear in all copies.
6//
7// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
8// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
10// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
14
15use crate::{endian::*, polyfill};
16
17/// An array of 16 bytes that can (in the x86_64 and AAarch64 ABIs, at least)
18/// be efficiently passed by value and returned by value (i.e. in registers),
19/// and which meets the alignment requirements of `u32` and `u64` (at least)
20/// for the target.
21#[repr(C)]
22#[derive(Copy, Clone)]
23pub struct Block {
24    subblocks: [u64; 2],
25}
26
27pub const BLOCK_LEN: usize = 16;
28
29impl Block {
30    #[inline]
31    pub fn zero() -> Self {
32        Self { subblocks: [0, 0] }
33    }
34
35    // TODO: Remove this.
36    #[inline]
37    pub fn from_u64_le(first: LittleEndian<u64>, second: LittleEndian<u64>) -> Self {
38        #[allow(deprecated)]
39        Self {
40            subblocks: [first.into_raw_value(), second.into_raw_value()],
41        }
42    }
43
44    // TODO: Remove this.
45    #[inline]
46    pub fn from_u64_be(first: BigEndian<u64>, second: BigEndian<u64>) -> Self {
47        #[allow(deprecated)]
48        Self {
49            subblocks: [first.into_raw_value(), second.into_raw_value()],
50        }
51    }
52
53    pub fn u64s_be_to_native(&self) -> [u64; 2] {
54        [
55            u64::from_be(self.subblocks[0]),
56            u64::from_be(self.subblocks[1]),
57        ]
58    }
59
60    #[inline]
61    pub fn overwrite_part_at(&mut self, index: usize, a: &[u8]) {
62        let mut tmp: [u8; BLOCK_LEN] = *self.as_ref();
63        tmp[index..][..a.len()].copy_from_slice(a);
64        *self = Self::from(&tmp)
65    }
66
67    #[inline]
68    pub fn zero_from(&mut self, index: usize) {
69        let mut tmp: [u8; BLOCK_LEN] = *self.as_ref();
70        polyfill::slice::fill(&mut tmp[index..], 0);
71        *self = Self::from(&tmp)
72    }
73
74    #[inline]
75    pub fn bitxor_assign(&mut self, a: Block) {
76        for (r, a) in self.subblocks.iter_mut().zip(a.subblocks.iter()) {
77            *r ^= *a;
78        }
79    }
80}
81
82impl From<&'_ [u8; BLOCK_LEN]> for Block {
83    #[inline]
84    fn from(bytes: &[u8; BLOCK_LEN]) -> Self {
85        unsafe { core::mem::transmute_copy(bytes) }
86    }
87}
88
89impl AsRef<[u8; BLOCK_LEN]> for Block {
90    #[allow(clippy::transmute_ptr_to_ptr)]
91    #[inline]
92    fn as_ref(&self) -> &[u8; BLOCK_LEN] {
93        unsafe { core::mem::transmute(self) }
94    }
95}
96
97#[cfg(test)]
98mod tests {
99    use super::*;
100
101    #[test]
102    fn test_bitxor_assign() {
103        const ONES: u64 = -1i64 as u64;
104        const TEST_CASES: &[([u64; 2], [u64; 2], [u64; 2])] = &[
105            ([0, 0], [0, 0], [0, 0]),
106            ([0, 0], [ONES, ONES], [ONES, ONES]),
107            ([0, ONES], [ONES, 0], [ONES, ONES]),
108            ([ONES, 0], [0, ONES], [ONES, ONES]),
109            ([ONES, ONES], [ONES, ONES], [0, 0]),
110        ];
111        for (expected_result, a, b) in TEST_CASES {
112            let mut r = Block::from_u64_le(a[0].into(), a[1].into());
113            r.bitxor_assign(Block::from_u64_le(b[0].into(), b[1].into()));
114            assert_eq!(*expected_result, r.subblocks);
115
116            // XOR is symmetric.
117            let mut r = Block::from_u64_le(b[0].into(), b[1].into());
118            r.bitxor_assign(Block::from_u64_le(a[0].into(), a[1].into()));
119            assert_eq!(*expected_result, r.subblocks);
120        }
121    }
122}
ring/aead/block.rs

ring/aead/
block.rs
