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3.7.1 Deduplicate flattening/zeroize code

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While the prior intent was to avoid zeroizing for vartime verification, which
is assumed to not have any private data, this simplifies the code and promotes
safety.
This commit is contained in:
Luke Parker 2023-03-02 01:13:07 -05:00
parent 2fd5cd8161
commit 15d6be1678
No known key found for this signature in database
1 changed files with 31 additions and 28 deletions
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59
crypto/multiexp/src/batch.rs
View file

@ -1,16 +1,32 @@
use rand_core::{RngCore, CryptoRng};
use zeroize::Zeroize;
use zeroize::{Zeroize, Zeroizing};
use ff::{Field, PrimeFieldBits};
use group::Group;
use crate::{multiexp, multiexp_vartime};
// Flatten the contained statements to a single Vec.
// Wrapped in Zeroizing in case any of the included statements contain private values.
#[allow(clippy::type_complexity)]
fn flat<Id: Copy + Zeroize, G: Group + Zeroize>(
slice: &[(Id, Vec<(G::Scalar, G)>)],
) -> Zeroizing<Vec<(G::Scalar, G)>>
where
<G as Group>::Scalar: PrimeFieldBits + Zeroize,
{
Zeroizing::new(slice.iter().flat_map(|pairs| pairs.1.iter()).cloned().collect::<Vec<_>>())
}
/// A batch verifier intended to verify a series of statements are each equivalent to zero.
#[allow(clippy::type_complexity)]
#[derive(Clone, Zeroize)]
pub struct BatchVerifier<Id: Copy + Zeroize, G: Group + Zeroize>(Vec<(Id, Vec<(G::Scalar, G)>)>);
pub struct BatchVerifier<Id: Copy + Zeroize, G: Group + Zeroize>(
Zeroizing<Vec<(Id, Vec<(G::Scalar, G)>)>>,
)
where
<G as Group>::Scalar: PrimeFieldBits + Zeroize;
impl<Id: Copy + Zeroize, G: Group + Zeroize> BatchVerifier<Id, G>
where
@ -19,7 +35,7 @@ where
/// Create a new batch verifier, expected to verify the following amount of statements.
/// This is a size hint and is not required to be accurate.
pub fn new(capacity: usize) -> BatchVerifier<Id, G> {
BatchVerifier(Vec::with_capacity(capacity))
BatchVerifier(Zeroizing::new(Vec::with_capacity(capacity)))
}
/// Queue a statement for batch verification.
@ -71,31 +87,20 @@ where
} {}
weight
};
self.0.push((id, pairs.into_iter().map(|(scalar, point)| (scalar * u, point)).collect()));
}
/// Perform batch verification, returning a boolean of if the statements equaled zero.
#[must_use]
pub fn verify_core(&self) -> bool {
let mut flat = self.0.iter().flat_map(|pairs| pairs.1.iter()).cloned().collect::<Vec<_>>();
let res = multiexp(&flat).is_identity().into();
flat.zeroize();
res
}
/// Perform batch verification, zeroizing the statements verified.
pub fn verify(mut self) -> bool {
let res = self.verify_core();
self.zeroize();
res
pub fn verify(&self) -> bool {
multiexp(&flat(&self.0)).is_identity().into()
}
/// Perform batch verification in variable time.
#[must_use]
pub fn verify_vartime(&self) -> bool {
multiexp_vartime(&self.0.iter().flat_map(|pairs| pairs.1.iter()).cloned().collect::<Vec<_>>())
.is_identity()
.into()
multiexp_vartime(&flat(&self.0)).is_identity().into()
}
/// Perform a binary search to identify which statement does not equal 0, returning None if all
@ -106,12 +111,8 @@ where
let mut slice = self.0.as_slice();
while slice.len() > 1 {
let split = slice.len() / 2;
if multiexp_vartime(
&slice[.. split].iter().flat_map(|pairs| pairs.1.iter()).cloned().collect::<Vec<_>>(),
)
.is_identity()
.into()
{
if multiexp_vartime(&flat(&slice[.. split])).is_identity().into() {
slice = &slice[split ..];
} else {
slice = &slice[.. split];
@ -126,10 +127,12 @@ where
/// Perform constant time batch verification, and if verification fails, identify one faulty
/// statement in variable time.
pub fn verify_with_vartime_blame(mut self) -> Result<(), Id> {
let res = if self.verify_core() { Ok(()) } else { Err(self.blame_vartime().unwrap()) };
self.zeroize();
res
pub fn verify_with_vartime_blame(&self) -> Result<(), Id> {
if self.verify() {
Ok(())
} else {
Err(self.blame_vartime().unwrap())
}
}
/// Perform variable time batch verification, and if verification fails, identify one faulty