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//! HMAC algorithms backed by wolfCrypt's native wc_Hmac* API.
//!
//! Each type implements the RustCrypto [`hmac`](hmac_trait) 0.12 traits
//! (`OutputSizeUser`, `KeySizeUser`, `KeyInit`, `Update`, `FixedOutput`,
//! `MacMarker`) so they satisfy the blanket `Mac` impl automatically.
//!
//! Callers should `use hmac_trait::Mac` for the full API:
//! `new_from_slice()`, `update()`, `finalize()`, `verify_slice()`.
use digest_trait::{FixedOutput, KeyInit, OutputSizeUser, Update};
use generic_array::GenericArray;
use typenum::*;
/// Internal macro that stamps out a complete HMAC wrapper for one algorithm.
///
/// The generated struct holds a heap-allocated wolfCrypt `Hmac` context
/// and delegates all operations through `wolfcrypt_hmac_*` C shims.
macro_rules! impl_hmac {
(
$name:ident,
$new_fn:path,
$output_size:ty,
$key_size:ty,
$cfg_gate:meta
) => {
#[$cfg_gate]
pub struct $name {
ctx: *mut core::ffi::c_void,
}
// SAFETY: The Hmac context is heap-allocated and only accessed through
// &self / &mut self. wolfCrypt's HMAC API is thread-safe when a
// context is used from a single thread, which Rust's ownership rules enforce.
#[$cfg_gate]
unsafe impl Send for $name {}
#[$cfg_gate]
impl Drop for $name {
fn drop(&mut self) {
if !self.ctx.is_null() {
// SAFETY: ctx was allocated by wolfcrypt_hmac_*_new.
unsafe { wolfcrypt_rs::wolfcrypt_hmac_free(self.ctx) };
}
}
}
#[$cfg_gate]
impl OutputSizeUser for $name {
type OutputSize = $output_size;
}
#[$cfg_gate]
impl crypto_common::KeySizeUser for $name {
type KeySize = $key_size;
}
#[$cfg_gate]
impl $name {
fn init_with_key(key: &[u8]) -> Self {
// SAFETY: key pointer and length are correct from the slice reference.
let ctx = unsafe { $new_fn(key.as_ptr(), key.len() as u32) };
assert!(
!ctx.is_null(),
concat!(stringify!($name), ": wolfcrypt_hmac_*_new returned NULL")
);
Self { ctx }
}
}
#[$cfg_gate]
impl KeyInit for $name {
fn new(key: &GenericArray<u8, <Self as crypto_common::KeySizeUser>::KeySize>) -> Self {
Self::init_with_key(key.as_slice())
}
fn new_from_slice(key: &[u8]) -> Result<Self, crypto_common::InvalidLength> {
Ok(Self::init_with_key(key))
}
}
#[$cfg_gate]
impl Update for $name {
fn update(&mut self, data: &[u8]) {
// SAFETY: ctx is valid; data pointer and length are correct.
let rc = unsafe {
wolfcrypt_rs::wolfcrypt_hmac_update(self.ctx, data.as_ptr(), data.len() as u32)
};
assert_eq!(
rc, 0,
concat!(stringify!($name), ": wolfcrypt_hmac_update failed")
);
}
}
#[$cfg_gate]
impl FixedOutput for $name {
fn finalize_into(mut self, out: &mut GenericArray<u8, Self::OutputSize>) {
// SAFETY: out is exactly OutputSize bytes; ctx is valid.
let rc = unsafe { wolfcrypt_rs::wolfcrypt_hmac_final(self.ctx, out.as_mut_ptr()) };
assert_eq!(
rc, 0,
concat!(stringify!($name), ": wolfcrypt_hmac_final failed")
);
// Prevent Drop from double-freeing.
let ctx = self.ctx;
self.ctx = core::ptr::null_mut();
unsafe { wolfcrypt_rs::wolfcrypt_hmac_free(ctx) };
}
}
#[$cfg_gate]
impl digest_trait::MacMarker for $name {}
};
}
impl_hmac!(
WolfHmacSha1,
wolfcrypt_rs::wolfcrypt_hmac_sha1_new,
U20,
U20,
cfg(wolfssl_hmac)
);
impl_hmac!(
WolfHmacSha256,
wolfcrypt_rs::wolfcrypt_hmac_sha256_new,
U32,
U32,
cfg(wolfssl_hmac)
);
impl_hmac!(
WolfHmacSha384,
wolfcrypt_rs::wolfcrypt_hmac_sha384_new,
U48,
U48,
cfg(all(wolfssl_hmac, wolfssl_sha384))
);
impl_hmac!(
WolfHmacSha512,
wolfcrypt_rs::wolfcrypt_hmac_sha512_new,
U64,
U64,
cfg(all(wolfssl_hmac, wolfssl_sha512))
);