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/// HKDF Errors.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Error {
/// The requested output key material in expand was too large for the used
/// hash function.
OkmTooLarge,
/// At least one function argument has been too large to process.
ArgumentsTooLarge,
}
macro_rules! impl_hkdf {
($name:ident,$extract:ident,$expand:ident,$tag_len:literal) => {
pub mod $name {
use super::Error;
/// HKDF extract using the `salt`, and the input key material `ikm`.
/// Returns the pre-key material in an array of tag length.
///
/// Note that this function panics if `salt` or `ikm` is larger than 2**32 bytes.
pub fn extract(salt: &[u8], ikm: &[u8]) -> [u8; $tag_len] {
let mut prk = [0u8; $tag_len];
unsafe {
hacl_sys::$extract(
prk.as_mut_ptr(),
salt.as_ptr() as _,
salt.len().try_into().unwrap(),
ikm.as_ptr() as _,
ikm.len().try_into().unwrap(),
);
}
prk
}
/// HKDF expand using the pre-key material `prk` and `info`. The output length
/// is defined through the result type.
/// Returns the key material in an array of length `okm_len` or
/// [`Error::OkmTooLarge`] if the requested `okm_len` is too large.
///
/// Note that this function returns an [`Error::ArgumentsTooLarge`]
/// if `salt`, `ikm`, or `OKM_LEN` is larger than 2**32 bytes.
pub fn expand<const OKM_LEN: usize>(
prk: &[u8],
info: &[u8],
) -> Result<[u8; OKM_LEN], Error> {
if OKM_LEN > 255 * $tag_len {
// Output size is too large. HACL doesn't catch this.
return Err(Error::OkmTooLarge);
}
let mut okm = [0u8; OKM_LEN];
unsafe {
hacl_sys::$expand(
okm.as_mut_ptr(),
prk.as_ptr() as _,
prk.len().try_into().map_err(|_| Error::ArgumentsTooLarge)?,
info.as_ptr() as _,
info.len()
.try_into()
.map_err(|_| Error::ArgumentsTooLarge)?,
OKM_LEN.try_into().map_err(|_| Error::ArgumentsTooLarge)?,
);
}
Ok(okm)
}
/// HKDF using the `salt`, input key material `ikm`, `info`. The output length
/// is defined through the result type.
/// Calls `extract` and `expand` with the given input.
///
/// Returns the key material in an array of length `okm_len`.
pub fn hkdf<const OKM_LEN: usize>(
salt: &[u8],
ikm: &[u8],
info: &[u8],
) -> Result<[u8; OKM_LEN], Error> {
let prk = extract(salt, ikm);
expand(&prk, info)
}
/// This module uses heap allocated vectors for cases where the output
/// length is not const.
pub mod vec {
use super::super::Error;
/// HKDF expand using the pre-key material `prk` and `info`. The output length
/// is defined through the result type.
/// Returns the key material in an array of length `okm_len` or
/// [`Error::OkmTooLarge`] if the requested `okm_len` is too large.
///
/// Note that this function returns an [`Error::ArgumentsTooLarge`]
/// if `salt`, `ikm`, or `OKM_LEN` is larger than 2**32 bytes.
pub fn expand(prk: &[u8], info: &[u8], okm_len: usize) -> Result<Vec<u8>, Error> {
if okm_len > 255 * $tag_len {
// Output size is too large. HACL doesn't catch this.
return Err(Error::OkmTooLarge);
}
let mut okm = vec![0u8; okm_len];
unsafe {
hacl_sys::$expand(
okm.as_mut_ptr(),
prk.as_ptr() as _,
prk.len().try_into().map_err(|_| Error::ArgumentsTooLarge)?,
info.as_ptr() as _,
info.len()
.try_into()
.map_err(|_| Error::ArgumentsTooLarge)?,
okm_len.try_into().map_err(|_| Error::ArgumentsTooLarge)?,
);
}
Ok(okm)
}
/// HKDF using the `salt`, input key material `ikm`, `info`. The output length
/// is defined through the result type.
/// Calls `extract` and `expand` with the given input.
///
/// Returns the key material in an array of length `okm_len`.
pub fn hkdf(
salt: &[u8],
ikm: &[u8],
info: &[u8],
okm_len: usize,
) -> Result<Vec<u8>, Error> {
let prk = super::extract(salt, ikm);
expand(&prk, info, okm_len)
}
}
}
};
}
impl_hkdf!(
sha2_256,
Hacl_HKDF_extract_sha2_256,
Hacl_HKDF_expand_sha2_256,
32
);
impl_hkdf!(
sha2_384,
Hacl_HKDF_extract_sha2_384,
Hacl_HKDF_expand_sha2_384,
48
);
impl_hkdf!(
sha2_512,
Hacl_HKDF_extract_sha2_512,
Hacl_HKDF_expand_sha2_512,
64
);