absolutebi/serai
1
0
Fork 0
mirror of https://github.com/serai-dex/serai.git synced 2025-12-08 12:19:24 +00:00
Code Issues Packages Projects Releases Wiki Activity

\#242 Expand usage of black_box/zeroize

Browse Source 
This commit greatly expands the usage of black_box/zeroize on bits, as it
originally should have. It is likely overkill, leading to less efficient
code generation, yet does its best to be comprehensive where comprehensiveness
is extremely annoying to achieve.

In the future, this usage of black_box may be desirable to move to its own
crate.

Credit to @AaronFeickert for identifying the original commit was incomplete.
This commit is contained in:
Luke Parker
2023-03-10 06:27:44 -05:00
parent 62dfc63532
commit ad470bc969
10 changed files with 163 additions and 47 deletions
Download Patch File Download Diff File Expand all files Collapse all files

37
crypto/ed448/src/backend.rs
View File

@@ -1,12 +1,36 @@
use zeroize::Zeroize;
// Feature gated due to MSRV requirements
#[cfg(feature = "black_box")]
pub(crate) fn black_box<T>(val: T) -> T {
core::hint::black_box(val)
}
#[cfg(not(feature = "black_box"))]
pub(crate) fn black_box<T>(val: T) -> T {
val
}
pub(crate) fn u8_from_bool(bit_ref: &mut bool) -> u8 {
let bit_ref = black_box(bit_ref);
let mut bit = black_box(*bit_ref);
let res = black_box(bit as u8);
bit.zeroize();
debug_assert!((res | 1) == 1);
bit_ref.zeroize();
res
}
#[doc(hidden)]
#[macro_export]
macro_rules! field {
($FieldName: ident, $MODULUS: ident, $WIDE_MODULUS: ident, $NUM_BITS: literal) => {
use core::ops::{Add, AddAssign, Neg, Sub, SubAssign, Mul, MulAssign};
use rand_core::RngCore;
use core::ops::{DerefMut, Add, AddAssign, Neg, Sub, SubAssign, Mul, MulAssign};
use subtle::{Choice, CtOption, ConstantTimeEq, ConstantTimeLess, ConditionallySelectable};
use rand_core::RngCore;
use generic_array::{typenum::U57, GenericArray};
use crypto_bigint::{Integer, Encoding};
@@ -18,6 +42,8 @@ macro_rules! field {
use dalek_ff_group::{from_wrapper, math_op};
use dalek_ff_group::{constant_time, from_uint, math};
use $crate::backend::u8_from_bool;
fn reduce(x: U1024) -> U512 {
U512::from_le_slice(&x.reduce(&$WIDE_MODULUS).unwrap().to_le_bytes()[.. 64])
}
@@ -59,10 +85,11 @@ macro_rules! field {
let mut res = Self(U512::ONE);
let mut bits = 0;
for (i, bit) in other.to_le_bits().iter().rev().enumerate() {
for (i, mut bit) in other.to_le_bits().iter_mut().rev().enumerate() {
bits <<= 1;
let bit = u8::from(*bit);
let mut bit = u8_from_bool(bit.deref_mut());
bits |= bit;
bit.zeroize();
if ((i + 1) % 4) == 0 {
if i != 3 {