ssh-stamp-esp32 1.0.4

ESP32 implementation of the ssh-stamp-hal traits and bootable binary for ssh-stamp
Documentation 
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// SPDX-FileCopyrightText: 2026 Roman Valls Guimera <brainstorm@nopcode.org>
//
// SPDX-License-Identifier: GPL-3.0-or-later

//! HMAC-SHA256 implementation for ESP32 family
//!
//! Uses ESP32's hardware-accelerated HMAC peripheral.

use core::future::{Future, ready};

use hmac::{Hmac, Mac};
use sha2::{Digest, Sha256 as Sha256Impl};
use ssh_stamp_hal::{HashError, HashHal};

/// ESP32 HMAC implementation  
pub struct EspHmac;

impl HashHal for EspHmac {
    fn hmac_sha256(
        &mut self,
        key: &[u8],
        message: &[u8],
        output: &mut [u8; 32],
    ) -> impl Future<Output = Result<(), ssh_stamp_hal::HalError>> {
        // Use software HMAC implementation for now
        // ESP32 hardware HMAC requires special key handling
        ready(match Hmac::<Sha256Impl>::new_from_slice(key) {
            Ok(mut mac) => {
                mac.update(message);
                output.copy_from_slice(&mac.finalize().into_bytes());
                Ok(())
            }
            Err(_) => Err(ssh_stamp_hal::HalError::Hash(HashError::Config)),
        })
    }

    fn sha256(
        &mut self,
        message: &[u8],
        output: &mut [u8; 32],
    ) -> impl Future<Output = Result<(), ssh_stamp_hal::HalError>> {
        let mut hasher = Sha256Impl::new();
        hasher.update(message);
        let result = hasher.finalize();
        output.copy_from_slice(&result);
        ready(Ok(()))
    }
}