mirror of
https://github.com/saymrwulf/risc0-curve25519-dalek-source.git
synced 2026-09-04 20:03:40 +00:00
248 lines
8.4 KiB
Rust
248 lines
8.4 KiB
Rust
// -*- mode: rust; -*-
|
|
//
|
|
// This file is part of x25519-dalek.
|
|
// Copyright (c) 2017-2019 isis lovecruft
|
|
// Copyright (c) 2019 DebugSteven
|
|
// See LICENSE for licensing information.
|
|
//
|
|
// Authors:
|
|
// - isis agora lovecruft <isis@patternsinthevoid.net>
|
|
// - DebugSteven <debugsteven@gmail.com>
|
|
|
|
//! x25519 Diffie-Hellman key exchange
|
|
//!
|
|
//! This implements x25519 key exchange as specified by Mike Hamburg
|
|
//! and Adam Langley in [RFC7748](https://tools.ietf.org/html/rfc7748).
|
|
|
|
use clear_on_drop::clear::Clear;
|
|
|
|
use curve25519_dalek::constants::ED25519_BASEPOINT_TABLE;
|
|
use curve25519_dalek::montgomery::MontgomeryPoint;
|
|
use curve25519_dalek::scalar::Scalar;
|
|
|
|
use rand_core::RngCore;
|
|
use rand_core::CryptoRng;
|
|
|
|
/// A DH ephemeral public key.
|
|
pub struct EphemeralPublic(pub (crate) MontgomeryPoint);
|
|
|
|
impl From<[u8; 32]> for EphemeralPublic {
|
|
/// Given a byte array, construct an x25519 `EphemeralPublic` key
|
|
fn from(bytes: [u8; 32]) -> EphemeralPublic {
|
|
EphemeralPublic(MontgomeryPoint(bytes))
|
|
}
|
|
|
|
}
|
|
|
|
/// A DH ephemeral secret key.
|
|
pub struct EphemeralSecret(pub (crate) Scalar);
|
|
|
|
/// Overwrite ephemeral secret key material with null bytes when it goes out of scope.
|
|
impl Drop for EphemeralSecret {
|
|
fn drop(&mut self) {
|
|
self.0.clear();
|
|
}
|
|
}
|
|
|
|
impl EphemeralSecret {
|
|
/// Utility function to make it easier to call `x25519()` with
|
|
/// an ephemeral secret key and montegomery point as input and
|
|
/// a shared secret as the output.
|
|
pub fn diffie_hellman(self, their_public: &EphemeralPublic) -> SharedSecret {
|
|
SharedSecret(self.0 * their_public.0)
|
|
}
|
|
|
|
/// Generate an x25519 `EphemeralSecret` key.
|
|
pub fn new<T>(csprng: &mut T) -> Self
|
|
where T: RngCore + CryptoRng
|
|
{
|
|
let mut bytes = [0u8; 32];
|
|
|
|
csprng.fill_bytes(&mut bytes);
|
|
|
|
EphemeralSecret(clamp_scalar(bytes))
|
|
}
|
|
|
|
}
|
|
|
|
impl<'a> From<&'a EphemeralSecret> for EphemeralPublic {
|
|
/// Given an x25519 `EphemeralSecret` key, compute its corresponding
|
|
/// `EphemeralPublic` key.
|
|
fn from(secret: &'a EphemeralSecret) -> EphemeralPublic {
|
|
EphemeralPublic((&ED25519_BASEPOINT_TABLE * &secret.0).to_montgomery())
|
|
}
|
|
|
|
}
|
|
|
|
/// A DH SharedSecret
|
|
pub struct SharedSecret(pub (crate) MontgomeryPoint);
|
|
|
|
/// Overwrite shared secret material with null bytes when it goes out of scope.
|
|
impl Drop for SharedSecret {
|
|
fn drop(&mut self) {
|
|
self.0.clear();
|
|
}
|
|
}
|
|
|
|
impl SharedSecret {
|
|
|
|
/// View this shared secret key as a byte array.
|
|
#[inline]
|
|
pub fn as_bytes(&self) -> &[u8; 32] {
|
|
&self.0.as_bytes()
|
|
}
|
|
}
|
|
|
|
/// "Decode" a scalar from a 32-byte array.
|
|
///
|
|
/// By "decode" here, what is really meant is applying key clamping by twiddling
|
|
/// some bits.
|
|
///
|
|
/// # Returns
|
|
///
|
|
/// A `Scalar`.
|
|
fn clamp_scalar(scalar: [u8; 32]) -> Scalar {
|
|
let mut s: [u8; 32] = scalar.clone();
|
|
|
|
s[0] &= 248;
|
|
s[31] &= 127;
|
|
s[31] |= 64;
|
|
|
|
Scalar::from_bits(s)
|
|
}
|
|
|
|
/// The bare, byte-oriented x25519 function, exactly as specified in RFC7748.
|
|
///
|
|
/// This can be used with [`X25519_BASEPOINT_BYTES`] for people who
|
|
/// cannot use the better, safer, and faster ephemeral DH API.
|
|
pub fn x25519(k: [u8; 32], u: [u8; 32]) -> [u8; 32] {
|
|
(clamp_scalar(k) * MontgomeryPoint(u)).to_bytes()
|
|
}
|
|
|
|
/// The X25519 basepoint, for use with the bare, byte-oriented x25519
|
|
/// function. This is provided for people who cannot use the typed
|
|
/// ephemeral DH API for some reason.
|
|
pub const X25519_BASEPOINT_BYTES: [u8; 32] = [
|
|
9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
|
|
];
|
|
|
|
#[cfg(test)]
|
|
mod test {
|
|
use super::*;
|
|
|
|
#[test]
|
|
fn byte_basepoint_matches_edwards_scalar_mul() {
|
|
let mut scalar_bytes = [0x37; 32];
|
|
|
|
for i in 0..32 {
|
|
scalar_bytes[i] += 2;
|
|
|
|
let result = x25519(scalar_bytes, X25519_BASEPOINT_BYTES);
|
|
|
|
let expected = (&ED25519_BASEPOINT_TABLE * &clamp_scalar(scalar_bytes))
|
|
.to_montgomery()
|
|
.to_bytes();
|
|
|
|
assert_eq!(result, expected);
|
|
}
|
|
}
|
|
|
|
fn do_rfc7748_ladder_test1(input_scalar: [u8; 32], input_point: [u8; 32], expected: [u8; 32]) {
|
|
let result = x25519(input_scalar, input_point);
|
|
|
|
assert_eq!(result, expected);
|
|
}
|
|
|
|
#[test]
|
|
fn rfc7748_ladder_test1_vectorset1() {
|
|
let input_scalar: [u8; 32] = [
|
|
0xa5, 0x46, 0xe3, 0x6b, 0xf0, 0x52, 0x7c, 0x9d,
|
|
0x3b, 0x16, 0x15, 0x4b, 0x82, 0x46, 0x5e, 0xdd,
|
|
0x62, 0x14, 0x4c, 0x0a, 0xc1, 0xfc, 0x5a, 0x18,
|
|
0x50, 0x6a, 0x22, 0x44, 0xba, 0x44, 0x9a, 0xc4, ];
|
|
let input_point: [u8; 32] = [
|
|
0xe6, 0xdb, 0x68, 0x67, 0x58, 0x30, 0x30, 0xdb,
|
|
0x35, 0x94, 0xc1, 0xa4, 0x24, 0xb1, 0x5f, 0x7c,
|
|
0x72, 0x66, 0x24, 0xec, 0x26, 0xb3, 0x35, 0x3b,
|
|
0x10, 0xa9, 0x03, 0xa6, 0xd0, 0xab, 0x1c, 0x4c, ];
|
|
let expected: [u8; 32] = [
|
|
0xc3, 0xda, 0x55, 0x37, 0x9d, 0xe9, 0xc6, 0x90,
|
|
0x8e, 0x94, 0xea, 0x4d, 0xf2, 0x8d, 0x08, 0x4f,
|
|
0x32, 0xec, 0xcf, 0x03, 0x49, 0x1c, 0x71, 0xf7,
|
|
0x54, 0xb4, 0x07, 0x55, 0x77, 0xa2, 0x85, 0x52, ];
|
|
|
|
do_rfc7748_ladder_test1(input_scalar, input_point, expected);
|
|
}
|
|
|
|
#[test]
|
|
fn rfc7748_ladder_test1_vectorset2() {
|
|
let input_scalar: [u8; 32] = [
|
|
0x4b, 0x66, 0xe9, 0xd4, 0xd1, 0xb4, 0x67, 0x3c,
|
|
0x5a, 0xd2, 0x26, 0x91, 0x95, 0x7d, 0x6a, 0xf5,
|
|
0xc1, 0x1b, 0x64, 0x21, 0xe0, 0xea, 0x01, 0xd4,
|
|
0x2c, 0xa4, 0x16, 0x9e, 0x79, 0x18, 0xba, 0x0d, ];
|
|
let input_point: [u8; 32] = [
|
|
0xe5, 0x21, 0x0f, 0x12, 0x78, 0x68, 0x11, 0xd3,
|
|
0xf4, 0xb7, 0x95, 0x9d, 0x05, 0x38, 0xae, 0x2c,
|
|
0x31, 0xdb, 0xe7, 0x10, 0x6f, 0xc0, 0x3c, 0x3e,
|
|
0xfc, 0x4c, 0xd5, 0x49, 0xc7, 0x15, 0xa4, 0x93, ];
|
|
let expected: [u8; 32] = [
|
|
0x95, 0xcb, 0xde, 0x94, 0x76, 0xe8, 0x90, 0x7d,
|
|
0x7a, 0xad, 0xe4, 0x5c, 0xb4, 0xb8, 0x73, 0xf8,
|
|
0x8b, 0x59, 0x5a, 0x68, 0x79, 0x9f, 0xa1, 0x52,
|
|
0xe6, 0xf8, 0xf7, 0x64, 0x7a, 0xac, 0x79, 0x57, ];
|
|
|
|
do_rfc7748_ladder_test1(input_scalar, input_point, expected);
|
|
}
|
|
|
|
#[test]
|
|
#[ignore] // Run only if you want to burn a lot of CPU doing 1,000,000 DH operations
|
|
fn rfc7748_ladder_test2() {
|
|
use curve25519_dalek::constants::X25519_BASEPOINT;
|
|
|
|
let mut k: [u8; 32] = X25519_BASEPOINT.0;
|
|
let mut u: [u8; 32] = X25519_BASEPOINT.0;
|
|
let mut result: [u8; 32];
|
|
|
|
macro_rules! do_iterations {
|
|
($n:expr) => (
|
|
for _ in 0..$n {
|
|
result = x25519(k, u);
|
|
// OBVIOUS THING THAT I'M GOING TO NOTE ANYWAY BECAUSE I'VE
|
|
// SEEN PEOPLE DO THIS WITH GOLANG'S STDLIB AND YOU SURE AS
|
|
// HELL SHOULDN'T DO HORRIBLY STUPID THINGS LIKE THIS WITH
|
|
// MY LIBRARY:
|
|
//
|
|
// NEVER EVER TREAT SCALARS AS POINTS AND/OR VICE VERSA.
|
|
//
|
|
// ↓↓ DON'T DO THIS ↓↓
|
|
u = k.clone();
|
|
k = result;
|
|
}
|
|
)
|
|
}
|
|
|
|
// After one iteration:
|
|
// 422c8e7a6227d7bca1350b3e2bb7279f7897b87bb6854b783c60e80311ae3079
|
|
// After 1,000 iterations:
|
|
// 684cf59ba83309552800ef566f2f4d3c1c3887c49360e3875f2eb94d99532c51
|
|
// After 1,000,000 iterations:
|
|
// 7c3911e0ab2586fd864497297e575e6f3bc601c0883c30df5f4dd2d24f665424
|
|
|
|
do_iterations!(1);
|
|
assert_eq!(k, [ 0x42, 0x2c, 0x8e, 0x7a, 0x62, 0x27, 0xd7, 0xbc,
|
|
0xa1, 0x35, 0x0b, 0x3e, 0x2b, 0xb7, 0x27, 0x9f,
|
|
0x78, 0x97, 0xb8, 0x7b, 0xb6, 0x85, 0x4b, 0x78,
|
|
0x3c, 0x60, 0xe8, 0x03, 0x11, 0xae, 0x30, 0x79, ]);
|
|
do_iterations!(999);
|
|
assert_eq!(k, [ 0x68, 0x4c, 0xf5, 0x9b, 0xa8, 0x33, 0x09, 0x55,
|
|
0x28, 0x00, 0xef, 0x56, 0x6f, 0x2f, 0x4d, 0x3c,
|
|
0x1c, 0x38, 0x87, 0xc4, 0x93, 0x60, 0xe3, 0x87,
|
|
0x5f, 0x2e, 0xb9, 0x4d, 0x99, 0x53, 0x2c, 0x51, ]);
|
|
do_iterations!(999_000);
|
|
assert_eq!(k, [ 0x7c, 0x39, 0x11, 0xe0, 0xab, 0x25, 0x86, 0xfd,
|
|
0x86, 0x44, 0x97, 0x29, 0x7e, 0x57, 0x5e, 0x6f,
|
|
0x3b, 0xc6, 0x01, 0xc0, 0x88, 0x3c, 0x30, 0xdf,
|
|
0x5f, 0x4d, 0xd2, 0xd2, 0x4f, 0x66, 0x54, 0x24, ]);
|
|
}
|
|
}
|