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lib.rs
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lib.rs
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#![no_std]
use digest::{BlockInput, FixedOutput, Reset, Update};
use generic_array::{ArrayLength, GenericArray};
use hmac::{Hmac, Mac, NewMac};
pub struct HmacDRBG<D>
where
D: Update + BlockInput + FixedOutput + Default,
D::BlockSize: ArrayLength<u8>,
D::OutputSize: ArrayLength<u8>,
{
k: GenericArray<u8, D::OutputSize>,
v: GenericArray<u8, D::OutputSize>,
count: usize,
}
impl<D> HmacDRBG<D>
where
D: Update + FixedOutput + BlockInput + Reset + Clone + Default,
D::BlockSize: ArrayLength<u8>,
D::OutputSize: ArrayLength<u8>,
{
pub fn new(entropy: &[u8], nonce: &[u8], pers: &[u8]) -> Self {
let mut k = GenericArray::<u8, D::OutputSize>::default();
let mut v = GenericArray::<u8, D::OutputSize>::default();
for i in 0..k.as_slice().len() {
k[i] = 0x0;
}
for i in 0..v.as_slice().len() {
v[i] = 0x01;
}
let mut this = Self { k, v, count: 0 };
this.update(Some(&[entropy, nonce, pers]));
this.count = 1;
this
}
pub fn count(&self) -> usize {
self.count
}
pub fn reseed(&mut self, entropy: &[u8], add: Option<&[u8]>) {
self.update(Some(&[entropy, add.unwrap_or(&[])]))
}
pub fn generate<T: ArrayLength<u8>>(&mut self, add: Option<&[u8]>) -> GenericArray<u8, T> {
let mut result = GenericArray::default();
self.generate_to_slice(result.as_mut_slice(), add);
result
}
pub fn generate_to_slice(&mut self, result: &mut [u8], add: Option<&[u8]>) {
if let Some(add) = add {
self.update(Some(&[add]));
}
let mut i = 0;
while i < result.len() {
let mut vmac = self.hmac();
vmac.update(&self.v);
self.v = vmac.finalize().into_bytes();
for j in 0..self.v.len() {
result[i + j] = self.v[j];
}
i += self.v.len();
}
match add {
Some(add) => {
self.update(Some(&[add]));
}
None => {
self.update(None);
}
}
self.count += 1;
}
fn hmac(&self) -> Hmac<D> {
Hmac::new_varkey(&self.k).expect("Smaller and larger key size are handled by default")
}
fn update(&mut self, seeds: Option<&[&[u8]]>) {
let mut kmac = self.hmac();
kmac.update(&self.v);
kmac.update(&[0x00]);
if let Some(seeds) = seeds {
for seed in seeds {
kmac.update(seed);
}
}
self.k = kmac.finalize().into_bytes();
let mut vmac = self.hmac();
vmac.update(&self.v);
self.v = vmac.finalize().into_bytes();
if seeds.is_none() {
return;
}
let seeds = seeds.unwrap();
let mut kmac = self.hmac();
kmac.update(&self.v);
kmac.update(&[0x01]);
for seed in seeds {
kmac.update(seed);
}
self.k = kmac.finalize().into_bytes();
let mut vmac = self.hmac();
vmac.update(&self.v);
self.v = vmac.finalize().into_bytes();
}
}