use super::{ops, scalar::SCALAR_LEN};
use crate::{agreement, c, constant_time, cpu, ec, error, rand};
static CURVE25519: ec::Curve = ec::Curve {
public_key_len: PUBLIC_KEY_LEN,
elem_scalar_seed_len: ELEM_AND_SCALAR_LEN,
id: ec::CurveID::Curve25519,
check_private_key_bytes: x25519_check_private_key_bytes,
generate_private_key: x25519_generate_private_key,
public_from_private: x25519_public_from_private,
};
pub static X25519: agreement::Algorithm = agreement::Algorithm {
curve: &CURVE25519,
ecdh: x25519_ecdh,
};
#[allow(clippy::unnecessary_wraps)]
fn x25519_check_private_key_bytes(bytes: &[u8]) -> Result<(), error::Unspecified> {
debug_assert_eq!(bytes.len(), PRIVATE_KEY_LEN);
Ok(())
}
fn x25519_generate_private_key(
rng: &dyn rand::SecureRandom,
out: &mut [u8],
) -> Result<(), error::Unspecified> {
rng.fill(out)
}
fn x25519_public_from_private(
public_out: &mut [u8],
private_key: &ec::Seed,
) -> Result<(), error::Unspecified> {
let public_out = public_out.try_into()?;
let cpu_features = private_key.cpu_features;
let private_key: &[u8; SCALAR_LEN] = private_key.bytes_less_safe().try_into()?;
let private_key = ops::MaskedScalar::from_bytes_masked(*private_key);
#[cfg(all(not(target_os = "ios"), target_arch = "arm"))]
{
if cpu::arm::NEON.available(cpu_features) {
static MONTGOMERY_BASE_POINT: [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,
];
x25519_neon(public_out, &private_key, &MONTGOMERY_BASE_POINT);
return Ok(());
}
}
prefixed_extern! {
fn x25519_public_from_private_generic_masked(
public_key_out: &mut PublicKey,
private_key: &PrivateKey,
use_adx: c::int,
);
}
unsafe {
x25519_public_from_private_generic_masked(
public_out,
&private_key,
ops::has_fe25519_adx(cpu_features).into(),
);
}
Ok(())
}
fn x25519_ecdh(
out: &mut [u8],
my_private_key: &ec::Seed,
peer_public_key: untrusted::Input,
) -> Result<(), error::Unspecified> {
let cpu_features = my_private_key.cpu_features;
let my_private_key: &[u8; SCALAR_LEN] = my_private_key.bytes_less_safe().try_into()?;
let my_private_key = ops::MaskedScalar::from_bytes_masked(*my_private_key);
let peer_public_key: &[u8; PUBLIC_KEY_LEN] = peer_public_key.as_slice_less_safe().try_into()?;
fn scalar_mult(
out: &mut ops::EncodedPoint,
scalar: &ops::MaskedScalar,
point: &ops::EncodedPoint,
#[allow(unused_variables)] cpu_features: cpu::Features,
) {
#[cfg(all(not(target_os = "ios"), target_arch = "arm"))]
{
if cpu::arm::NEON.available(cpu_features) {
return x25519_neon(out, scalar, point);
}
}
#[cfg(all(target_arch = "x86_64", not(target_os = "windows")))]
{
if ops::has_fe25519_adx(cpu_features) {
prefixed_extern! {
fn x25519_scalar_mult_adx(
out: &mut ops::EncodedPoint,
scalar: &ops::MaskedScalar,
point: &ops::EncodedPoint,
);
}
return unsafe { x25519_scalar_mult_adx(out, scalar, point) };
}
}
prefixed_extern! {
fn x25519_scalar_mult_generic_masked(
out: &mut ops::EncodedPoint,
scalar: &ops::MaskedScalar,
point: &ops::EncodedPoint,
);
}
unsafe {
x25519_scalar_mult_generic_masked(out, scalar, point);
}
}
scalar_mult(
out.try_into()?,
&my_private_key,
peer_public_key,
cpu_features,
);
let zeros: SharedSecret = [0; SHARED_SECRET_LEN];
if constant_time::verify_slices_are_equal(out, &zeros).is_ok() {
return Err(error::Unspecified);
}
Ok(())
}
#[cfg(all(not(target_os = "ios"), target_arch = "arm"))]
fn x25519_neon(out: &mut ops::EncodedPoint, scalar: &ops::MaskedScalar, point: &ops::EncodedPoint) {
prefixed_extern! {
fn x25519_NEON(
out: &mut ops::EncodedPoint,
scalar: &ops::MaskedScalar,
point: &ops::EncodedPoint,
);
}
unsafe { x25519_NEON(out, scalar, point) }
}
const ELEM_AND_SCALAR_LEN: usize = ops::ELEM_LEN;
type PrivateKey = ops::MaskedScalar;
const PRIVATE_KEY_LEN: usize = ELEM_AND_SCALAR_LEN;
type PublicKey = [u8; PUBLIC_KEY_LEN];
const PUBLIC_KEY_LEN: usize = ELEM_AND_SCALAR_LEN;
type SharedSecret = [u8; SHARED_SECRET_LEN];
const SHARED_SECRET_LEN: usize = ELEM_AND_SCALAR_LEN;
#[cfg(test)]
mod tests {
use super::*;
use crate::ec;
use untrusted::Input;
#[test]
fn test_x25519_public_from_private() {
struct TestVector {
private: [u8; 32],
public: [u8; 32],
}
static TEST_CASES: &[TestVector] = &[
TestVector {
private: [
0x77, 0x07, 0x6d, 0x0a, 0x73, 0x18, 0xa5, 0x7d, 0x3c, 0x16, 0xc1, 0x72, 0x51,
0xb2, 0x66, 0x45, 0xdf, 0x4c, 0x2f, 0x87, 0xeb, 0xc0, 0x99, 0x2a, 0xb1, 0x77,
0xfb, 0xa5, 0x1d, 0xb9, 0x2c, 0x2a,
],
public: [
0x85, 0x20, 0xf0, 0x09, 0x89, 0x30, 0xa7, 0x54, 0x74, 0x8b, 0x7d, 0xdc, 0xb4,
0x3e, 0xf7, 0x5a, 0x0d, 0xbf, 0x3a, 0x0d, 0x26, 0x38, 0x1a, 0xf4, 0xeb, 0xa4,
0xa9, 0x8e, 0xaa, 0x9b, 0x4e, 0x6a,
],
},
TestVector {
private: [
0x5d, 0xab, 0x08, 0x7e, 0x62, 0x4a, 0x8a, 0x4b, 0x79, 0xe1, 0x7f, 0x8b, 0x83,
0x80, 0x0e, 0xe6, 0x6f, 0x3b, 0xb1, 0x29, 0x26, 0x18, 0xb6, 0xfd, 0x1c, 0x2f,
0x8b, 0x27, 0xff, 0x88, 0xe0, 0xeb,
],
public: [
0xde, 0x9e, 0xdb, 0x7d, 0x7b, 0x7d, 0xc1, 0xb4, 0xd3, 0x5b, 0x61, 0xc2, 0xec,
0xe4, 0x35, 0x37, 0x3f, 0x83, 0x43, 0xc8, 0x5b, 0x78, 0x67, 0x4d, 0xad, 0xfc,
0x7e, 0x14, 0x6f, 0x88, 0x2b, 0x4f,
],
},
];
let cpu_features = cpu::features();
for test_case in TEST_CASES {
let seed =
ec::Seed::from_bytes(&CURVE25519, Input::from(&test_case.private), cpu_features)
.unwrap();
let mut output = [0u8; 32];
x25519_public_from_private(&mut output, &seed).unwrap();
assert_eq!(output, test_case.public);
}
}
}