saymrwulf/risc0-curve25519-dalek-source
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change impl Drop for SharedSecret to use clear directly

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DebugSteven 2018-11-16 12:48:49 -05:00
parent cb18af7c1b
commit 4c6498ec69
1 changed files with 6 additions and 10 deletions
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16
src/x25519.rs
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@ -12,7 +12,6 @@
//! This implements x25519 key exchange as specified by Mike Hamburg //! This implements x25519 key exchange as specified by Mike Hamburg
//! and Adam Langley in [RFC7748](https://tools.ietf.org/html/rfc7748). //! and Adam Langley in [RFC7748](https://tools.ietf.org/html/rfc7748).
use core::mem;
use core::ops::Mul; use core::ops::Mul;
use clear_on_drop::clear::Clear; use clear_on_drop::clear::Clear;
@ -72,7 +71,7 @@ impl Ephemeral {
let mut bytes = [0u8; 32]; let mut bytes = [0u8; 32];
csprng.fill_bytes(&mut bytes); csprng.fill_bytes(&mut bytes);
Ephemeral(decode_scalar(&bytes)) Ephemeral(decode_scalar(&bytes))
} }
@ -83,18 +82,15 @@ impl Ephemeral {
} }
#[repr(C)]
/// A DH SharedSecret /// A DH SharedSecret
#[repr(C)]
#[derive(Default)] // we derive Default in order to use the clear() method in Drop
pub struct SharedSecret(pub (crate) MontgomeryPoint); pub struct SharedSecret(pub (crate) MontgomeryPoint);
/// Overwrite shared secret material with null bytes when it goes out of scope. /// Overwrite shared secret material with null bytes when it goes out of scope.
impl Drop for SharedSecret { impl Drop for SharedSecret {
fn drop(&mut self) { fn drop(&mut self) {
let bytes: &mut [u8; 32] = unsafe { self.0.clear();
mem::transmute::<&mut MontgomeryPoint, &mut [u8; 32]>
(&mut self.0)
};
bytes.clear();
} }
} }
@ -131,7 +127,7 @@ mod test {
input_point: &MontgomeryPoint, input_point: &MontgomeryPoint,
expected: &[u8; 32]) { expected: &[u8; 32]) {
let result = x25519(&input_scalar, &input_point); let result = x25519(&input_scalar, &input_point);
assert_eq!(result.0, *expected); assert_eq!(result.0, *expected);
} }
@ -210,7 +206,7 @@ mod test {
// 684cf59ba83309552800ef566f2f4d3c1c3887c49360e3875f2eb94d99532c51 // 684cf59ba83309552800ef566f2f4d3c1c3887c49360e3875f2eb94d99532c51
// After 1,000,000 iterations: // After 1,000,000 iterations:
// 7c3911e0ab2586fd864497297e575e6f3bc601c0883c30df5f4dd2d24f665424 // 7c3911e0ab2586fd864497297e575e6f3bc601c0883c30df5f4dd2d24f665424
do_iterations!(1); do_iterations!(1);
assert_eq!(k.as_bytes(), &[ 0x42, 0x2c, 0x8e, 0x7a, 0x62, 0x27, 0xd7, 0xbc, assert_eq!(k.as_bytes(), &[ 0x42, 0x2c, 0x8e, 0x7a, 0x62, 0x27, 0xd7, 0xbc,
0xa1, 0x35, 0x0b, 0x3e, 0x2b, 0xb7, 0x27, 0x9f, 0xa1, 0x35, 0x0b, 0x3e, 0x2b, 0xb7, 0x27, 0x9f,