rs-matter/matter/src/secure_channel/crypto_mbedtls.rs

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/*
*
* Copyright (c) 2020-2022 Project CHIP Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
use alloc::sync::Arc;
use core::ops::{Mul, Sub};
use crate::error::Error;
use byteorder::{ByteOrder, LittleEndian};
use log::error;
use mbedtls::{
bignum::Mpi,
ecp::EcPoint,
hash::Md,
pk::{EcGroup, EcGroupId, Pk},
rng::{CtrDrbg, OsEntropy},
};
extern crate alloc;
const MATTER_M_BIN: [u8; 65] = [
0x04, 0x88, 0x6e, 0x2f, 0x97, 0xac, 0xe4, 0x6e, 0x55, 0xba, 0x9d, 0xd7, 0x24, 0x25, 0x79, 0xf2,
0x99, 0x3b, 0x64, 0xe1, 0x6e, 0xf3, 0xdc, 0xab, 0x95, 0xaf, 0xd4, 0x97, 0x33, 0x3d, 0x8f, 0xa1,
0x2f, 0x5f, 0xf3, 0x55, 0x16, 0x3e, 0x43, 0xce, 0x22, 0x4e, 0x0b, 0x0e, 0x65, 0xff, 0x02, 0xac,
0x8e, 0x5c, 0x7b, 0xe0, 0x94, 0x19, 0xc7, 0x85, 0xe0, 0xca, 0x54, 0x7d, 0x55, 0xa1, 0x2e, 0x2d,
0x20,
];
const MATTER_N_BIN: [u8; 65] = [
0x04, 0xd8, 0xbb, 0xd6, 0xc6, 0x39, 0xc6, 0x29, 0x37, 0xb0, 0x4d, 0x99, 0x7f, 0x38, 0xc3, 0x77,
0x07, 0x19, 0xc6, 0x29, 0xd7, 0x01, 0x4d, 0x49, 0xa2, 0x4b, 0x4f, 0x98, 0xba, 0xa1, 0x29, 0x2b,
0x49, 0x07, 0xd6, 0x0a, 0xa6, 0xbf, 0xad, 0xe4, 0x50, 0x08, 0xa6, 0x36, 0x33, 0x7f, 0x51, 0x68,
0xc6, 0x4d, 0x9b, 0xd3, 0x60, 0x34, 0x80, 0x8c, 0xd5, 0x64, 0x49, 0x0b, 0x1e, 0x65, 0x6e, 0xdb,
0xe7,
];
#[allow(non_snake_case)]
pub struct CryptoSpake2 {
group: EcGroup,
order: Mpi,
xy: Mpi,
w0: Mpi,
w1: Mpi,
M: EcPoint,
N: EcPoint,
L: EcPoint,
pB: EcPoint,
}
impl CryptoSpake2 {
#[allow(non_snake_case)]
pub fn new() -> Result<Self, Error> {
let group = EcGroup::new(mbedtls::pk::EcGroupId::SecP256R1)?;
let order = group.order()?;
let M = EcPoint::from_binary(&group, &MATTER_M_BIN)?;
let N = EcPoint::from_binary(&group, &MATTER_N_BIN)?;
Ok(Self {
group,
order,
xy: Mpi::new(0)?,
M,
N,
w0: Mpi::new(0)?,
w1: Mpi::new(0)?,
L: EcPoint::new()?,
pB: EcPoint::new()?,
})
}
// Computes w0 from w0s respectively
pub fn set_w0_from_w0s(&mut self, w0s: &[u8]) -> Result<(), Error> {
// From the Matter Spec,
// w0 = w0s mod p
// where p is the order of the curve
self.w0 = Mpi::from_binary(w0s)?;
self.w0 = self.w0.modulo(&self.order)?;
Ok(())
}
pub fn set_w1_from_w1s(&mut self, w1s: &[u8]) -> Result<(), Error> {
// From the Matter Spec,
// w1 = w1s mod p
// where p is the order of the curve
self.w1 = Mpi::from_binary(w1s)?;
self.w1 = self.w1.modulo(&self.order)?;
Ok(())
}
pub fn set_w0(&mut self, w0: &[u8]) -> Result<(), Error> {
self.w0 = Mpi::from_binary(w0)?;
Ok(())
}
pub fn set_w1(&mut self, w1: &[u8]) -> Result<(), Error> {
self.w1 = Mpi::from_binary(w1)?;
Ok(())
}
#[allow(non_snake_case)]
pub fn set_L(&mut self, l: &[u8]) -> Result<(), Error> {
2023-01-11 13:35:25 +01:00
self.L = EcPoint::from_binary(&self.group, l)?;
Ok(())
}
#[allow(non_snake_case)]
#[allow(dead_code)]
pub fn set_L_from_w1s(&mut self, w1s: &[u8]) -> Result<(), Error> {
// From the Matter spec,
// L = w1 * P
// where P is the generator of the underlying elliptic curve
self.set_w1_from_w1s(w1s)?;
// TODO: rust-mbedtls doesn't yet accept the DRBG parameter
self.L = self.group.generator()?.mul(&mut self.group, &self.w1)?;
Ok(())
}
#[allow(non_snake_case)]
pub fn get_pB(&mut self, pB: &mut [u8]) -> Result<(), Error> {
// From the SPAKE2+ spec (https://datatracker.ietf.org/doc/draft-bar-cfrg-spake2plus/)
// for y
// - select random y between 0 to p
// - Y = y*P + w0*N
// - pB = Y
// A private key on this curve is a random number between 0 to p
let mut ctr_drbg = CtrDrbg::new(Arc::new(OsEntropy::new()), None)?;
self.xy = Pk::generate_ec(&mut ctr_drbg, EcGroupId::SecP256R1)?.ec_private()?;
let P = self.group.generator()?;
self.pB = EcPoint::muladd(&mut self.group, &P, &self.xy, &self.N, &self.w0)?;
let pB_internal = self.pB.to_binary(&self.group, false)?;
let pB_internal = pB_internal.as_slice();
if pB_internal.len() != pB.len() {
error!("pB length mismatch");
return Err(Error::Invalid);
}
pB.copy_from_slice(pB_internal);
Ok(())
}
#[allow(non_snake_case)]
pub fn get_TT_as_verifier(
&mut self,
context: &[u8],
pA: &[u8],
pB: &[u8],
out: &mut [u8],
) -> Result<(), Error> {
let mut TT = Md::new(mbedtls::hash::Type::Sha256)?;
// context
Self::add_to_tt(&mut TT, context)?;
// 2 empty identifiers
Self::add_to_tt(&mut TT, &[])?;
Self::add_to_tt(&mut TT, &[])?;
// M
Self::add_to_tt(&mut TT, &MATTER_M_BIN)?;
// N
Self::add_to_tt(&mut TT, &MATTER_N_BIN)?;
// X = pA
Self::add_to_tt(&mut TT, pA)?;
// Y = pB
Self::add_to_tt(&mut TT, pB)?;
let X = EcPoint::from_binary(&self.group, pA)?;
let (Z, V) = Self::get_ZV_as_verifier(
&self.w0,
&self.L,
&mut self.M,
&X,
&self.xy,
&self.order,
&mut self.group,
)?;
// Z
let tmp = Z.to_binary(&self.group, false)?;
let tmp = tmp.as_slice();
Self::add_to_tt(&mut TT, tmp)?;
// V
let tmp = V.to_binary(&self.group, false)?;
let tmp = tmp.as_slice();
Self::add_to_tt(&mut TT, tmp)?;
// w0
let tmp = self.w0.to_binary()?;
let tmp = tmp.as_slice();
Self::add_to_tt(&mut TT, tmp)?;
TT.finish(out)?;
Ok(())
}
fn add_to_tt(tt: &mut Md, buf: &[u8]) -> Result<(), Error> {
let mut len_buf: [u8; 8] = [0; 8];
LittleEndian::write_u64(&mut len_buf, buf.len() as u64);
tt.update(&len_buf)?;
if !buf.is_empty() {
tt.update(buf)?;
}
Ok(())
}
#[inline(always)]
#[allow(non_snake_case)]
#[allow(dead_code)]
fn get_ZV_as_prover(
w0: &Mpi,
w1: &Mpi,
N: &mut EcPoint,
Y: &EcPoint,
x: &Mpi,
order: &Mpi,
group: &mut EcGroup,
) -> Result<(EcPoint, EcPoint), Error> {
// As per the RFC, the operation here is:
// Z = h*x*(Y - w0*N)
// V = h*w1*(Y - w0*N)
// We will follow the same sequence as in C++ SDK, under the assumption
// that the same sequence works for all embedded platforms. So the step
// of operations is:
// tmp = x*w0
// Z = x*Y + tmp*N (N is inverted to get the 'negative' effect)
// Z = h*Z (cofactor Mul)
let mut tmp = x.mul(w0)?;
tmp = tmp.modulo(order)?;
let inverted_N = Self::invert(group, N)?;
let Z = EcPoint::muladd(group, Y, x, &inverted_N, &tmp)?;
// Cofactor for P256 is 1, so that is a No-Op
let mut tmp = w0.mul(w1)?;
tmp = tmp.modulo(order)?;
let V = EcPoint::muladd(group, Y, w1, &inverted_N, &tmp)?;
Ok((Z, V))
}
#[inline(always)]
#[allow(non_snake_case)]
#[allow(dead_code)]
fn get_ZV_as_verifier(
w0: &Mpi,
L: &EcPoint,
M: &mut EcPoint,
X: &EcPoint,
y: &Mpi,
order: &Mpi,
group: &mut EcGroup,
) -> Result<(EcPoint, EcPoint), Error> {
// As per the RFC, the operation here is:
// Z = h*y*(X - w0*M)
// V = h*y*L
// We will follow the same sequence as in C++ SDK, under the assumption
// that the same sequence works for all embedded platforms. So the step
// of operations is:
// tmp = y*w0
// Z = y*X + tmp*M (M is inverted to get the 'negative' effect)
// Z = h*Z (cofactor Mul)
let mut tmp = y.mul(w0)?;
tmp = tmp.modulo(order)?;
let inverted_M = Self::invert(group, M)?;
let Z = EcPoint::muladd(group, X, y, &inverted_M, &tmp)?;
// Cofactor for P256 is 1, so that is a No-Op
let V = L.mul(group, y)?;
Ok((Z, V))
}
fn invert(group: &mut EcGroup, num: &EcPoint) -> Result<EcPoint, mbedtls::Error> {
let p = group.p()?;
let num_y = num.y()?;
let inverted_num_y = p.sub(&num_y)?;
EcPoint::from_components(num.x()?, inverted_num_y)
}
}
#[cfg(test)]
mod tests {
use super::CryptoSpake2;
use crate::secure_channel::spake2p_test_vectors::test_vectors::*;
use mbedtls::bignum::Mpi;
use mbedtls::ecp::EcPoint;
#[test]
#[allow(non_snake_case)]
fn test_get_X() {
for t in RFC_T {
let mut c = CryptoSpake2::new().unwrap();
let x = Mpi::from_binary(&t.x).unwrap();
c.set_w0(&t.w0).unwrap();
let P = c.group.generator().unwrap();
let r = EcPoint::muladd(&mut c.group, &P, &x, &c.M, &c.w0).unwrap();
assert_eq!(t.X, r.to_binary(&c.group, false).unwrap().as_slice());
}
}
#[test]
#[allow(non_snake_case)]
fn test_get_Y() {
for t in RFC_T {
let mut c = CryptoSpake2::new().unwrap();
let y = Mpi::from_binary(&t.y).unwrap();
c.set_w0(&t.w0).unwrap();
let P = c.group.generator().unwrap();
let r = EcPoint::muladd(&mut c.group, &P, &y, &c.N, &c.w0).unwrap();
assert_eq!(t.Y, r.to_binary(&c.group, false).unwrap().as_slice());
}
}
#[test]
#[allow(non_snake_case)]
fn test_get_ZV_as_prover() {
for t in RFC_T {
let mut c = CryptoSpake2::new().unwrap();
let x = Mpi::from_binary(&t.x).unwrap();
c.set_w0(&t.w0).unwrap();
c.set_w1(&t.w1).unwrap();
let Y = EcPoint::from_binary(&c.group, &t.Y).unwrap();
let (Z, V) = CryptoSpake2::get_ZV_as_prover(
&c.w0,
&c.w1,
&mut c.N,
&Y,
&x,
&c.order,
&mut c.group,
)
.unwrap();
assert_eq!(t.Z, Z.to_binary(&c.group, false).unwrap().as_slice());
assert_eq!(t.V, V.to_binary(&c.group, false).unwrap().as_slice());
}
}
#[test]
#[allow(non_snake_case)]
fn test_get_ZV_as_verifier() {
for t in RFC_T {
let mut c = CryptoSpake2::new().unwrap();
let y = Mpi::from_binary(&t.y).unwrap();
c.set_w0(&t.w0).unwrap();
let X = EcPoint::from_binary(&c.group, &t.X).unwrap();
let L = EcPoint::from_binary(&c.group, &t.L).unwrap();
let (Z, V) = CryptoSpake2::get_ZV_as_verifier(
&c.w0,
&L,
&mut c.M,
&X,
&y,
&c.order,
&mut c.group,
)
.unwrap();
assert_eq!(t.Z, Z.to_binary(&c.group, false).unwrap().as_slice());
assert_eq!(t.V, V.to_binary(&c.group, false).unwrap().as_slice());
}
}
}