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//! HMAC algorithms backed by wolfCrypt's HMAC_CTX 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 core::ffi::c_void;
use digest_trait::{FixedOutput, KeyInit, OutputSizeUser, Update};
use generic_array::GenericArray;
use typenum::*;
use crate::error::len_as_c_int;
/// Internal macro that stamps out a complete HMAC wrapper for one algorithm.
///
/// The generated struct holds a heap-allocated `HMAC_CTX` and delegates
/// all operations to wolfCrypt through the OpenSSL-compat HMAC layer.
macro_rules! impl_hmac {
(
$name:ident,
$evp_fn:path,
$output_size:ty,
$key_size:ty,
$cfg_gate:meta
) => {
#[$cfg_gate]
pub struct $name {
ctx: *mut wolfcrypt_rs::HMAC_CTX,
}
// SAFETY: HMAC_CTX is heap-allocated and only accessed through
// &self / &mut self. wolfCrypt's HMAC layer is thread-safe when a
// context is used from a single thread, which Rust's ownership
// rules enforce.
#[$cfg_gate]
unsafe impl Send for $name {}
#[$cfg_gate]
impl $name {
/// Return the algorithm descriptor pointer for this HMAC's hash.
#[inline]
fn evp_md() -> *const wolfcrypt_rs::EVP_MD {
// SAFETY: EVP_sha* functions return a static const pointer.
unsafe { $evp_fn() }
}
}
// ------------------------------------------------------------------
// core / RustCrypto trait impls
// ------------------------------------------------------------------
#[$cfg_gate]
impl Drop for $name {
fn drop(&mut self) {
// SAFETY: self.ctx was allocated via HMAC_CTX_new and
// is only freed once here.
unsafe {
wolfcrypt_rs::HMAC_CTX_free(self.ctx);
}
}
}
#[$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 $name {
/// Shared initialisation: allocate an HMAC_CTX and key it.
fn init_with_key(key: &[u8]) -> Self {
// SAFETY: HMAC_CTX_new returns a heap-allocated context
// or NULL on OOM.
let ctx = unsafe { wolfcrypt_rs::HMAC_CTX_new() };
assert!(!ctx.is_null(), "HMAC_CTX_new returned NULL");
// SAFETY: ctx is non-null and freshly allocated. key pointer
// and length are guaranteed correct by the slice reference.
// HMAC_Init_ex with a non-null key sets the key and algorithm.
unsafe {
let rc = wolfcrypt_rs::HMAC_Init_ex(
ctx,
key.as_ptr() as *const c_void,
len_as_c_int(key.len()),
Self::evp_md(),
core::ptr::null_mut(),
);
assert_eq!(rc, 1, "HMAC_Init_ex failed (OOM or invalid algorithm)");
}
Self { ctx }
}
}
#[$cfg_gate]
impl KeyInit for $name {
/// Create from a fixed-size key (KeySize bytes).
fn new(key: &GenericArray<u8, <Self as crypto_common::KeySizeUser>::KeySize>) -> Self {
Self::init_with_key(key.as_slice())
}
/// Create from a variable-length key. HMAC accepts any key size
/// per RFC 2104, so this never returns `InvalidLength`.
fn new_from_slice(key: &[u8]) -> Result<Self, crypto_common::InvalidLength> {
Ok(Self::init_with_key(key))
}
}
#[$cfg_gate]
impl Update for $name {
fn update(&mut self, data: &[u8]) {
// SAFETY: self.ctx is valid. data pointer and length are
// guaranteed correct by the slice reference.
unsafe {
let rc = wolfcrypt_rs::HMAC_Update(
self.ctx,
data.as_ptr(),
data.len(),
);
assert_eq!(rc, 1, "HMAC_Update failed (context not initialized)");
}
}
}
#[$cfg_gate]
impl FixedOutput for $name {
fn finalize_into(self, out: &mut GenericArray<u8, Self::OutputSize>) {
let mut len: u32 = 0;
// SAFETY: out is exactly OutputSize bytes. self.ctx is
// valid. After this call, Drop will free the context.
unsafe {
let rc = wolfcrypt_rs::HMAC_Final(
self.ctx,
out.as_mut_ptr(),
&mut len,
);
assert_eq!(rc, 1, "HMAC_Final failed (context not initialized)");
}
// Drop runs after this and frees self.ctx.
}
}
#[$cfg_gate]
impl digest_trait::MacMarker for $name {}
};
}
// ======================================================================
// Stamp out HMAC types
// ======================================================================
impl_hmac!(
WolfHmacSha1,
wolfcrypt_rs::EVP_sha1,
U20,
U20,
cfg(all(wolfssl_openssl_extra, wolfssl_hmac))
);
impl_hmac!(
WolfHmacSha256,
wolfcrypt_rs::EVP_sha256,
U32,
U32,
cfg(all(wolfssl_openssl_extra, wolfssl_hmac))
);
impl_hmac!(
WolfHmacSha384,
wolfcrypt_rs::EVP_sha384,
U48,
U48,
cfg(all(wolfssl_openssl_extra, wolfssl_hmac, wolfssl_sha384))
);
impl_hmac!(
WolfHmacSha512,
wolfcrypt_rs::EVP_sha512,
U64,
U64,
cfg(all(wolfssl_openssl_extra, wolfssl_hmac, wolfssl_sha512))
);