rust-web-server 18.8.2

Single-binary web server and reverse proxy: automatic HTTPS (Let's Encrypt), HTTP/1.1, HTTP/2 and HTTP/3, load balancing, auth and rate limiting, configured in one TOML file. Also a Rust library: routing, middleware, MCP server, ORM, background jobs. No hyper, no Tower; HTTP/2 and HTTP/3 framing via h2 and quinn.
Documentation 
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//! SHA-256 (FIPS 180-4) and HMAC-SHA256 (RFC 2104), for code that must sign
//! or verify without an optional crypto dependency — e.g. the MCP server's
//! `requestState` (MCP 2026-07-28). Not constant-time beyond [`verify`]'s
//! comparison; not for secrets that a timing side channel would expose.

#[cfg(test)]
mod tests;

const K: [u32; 64] = [
    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
];

/// SHA-256 of `data`.
pub fn sha256(data: &[u8]) -> [u8; 32] {
    let mut h: [u32; 8] = [0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19];
    let mut message = data.to_vec();
    message.push(0x80);
    while message.len() % 64 != 56 {
        message.push(0);
    }
    message.extend_from_slice(&((data.len() as u64).wrapping_mul(8)).to_be_bytes());
    for block in message.chunks(64) {
        let mut w = [0u32; 64];
        for (i, word) in block.chunks(4).enumerate() {
            w[i] = u32::from_be_bytes([word[0], word[1], word[2], word[3]]);
        }
        for i in 16..64 {
            let s0 = w[i - 15].rotate_right(7) ^ w[i - 15].rotate_right(18) ^ (w[i - 15] >> 3);
            let s1 = w[i - 2].rotate_right(17) ^ w[i - 2].rotate_right(19) ^ (w[i - 2] >> 10);
            w[i] = w[i - 16].wrapping_add(s0).wrapping_add(w[i - 7]).wrapping_add(s1);
        }
        let [mut a, mut b, mut c, mut d, mut e, mut f, mut g, mut hh] = h;
        for i in 0..64 {
            let s1 = e.rotate_right(6) ^ e.rotate_right(11) ^ e.rotate_right(25);
            let ch = (e & f) ^ (!e & g);
            let t1 = hh.wrapping_add(s1).wrapping_add(ch).wrapping_add(K[i]).wrapping_add(w[i]);
            let s0 = a.rotate_right(2) ^ a.rotate_right(13) ^ a.rotate_right(22);
            let maj = (a & b) ^ (a & c) ^ (b & c);
            let t2 = s0.wrapping_add(maj);
            hh = g;
            g = f;
            f = e;
            e = d.wrapping_add(t1);
            d = c;
            c = b;
            b = a;
            a = t1.wrapping_add(t2);
        }
        for (state, value) in h.iter_mut().zip([a, b, c, d, e, f, g, hh]) {
            *state = state.wrapping_add(value);
        }
    }
    let mut out = [0u8; 32];
    for (i, word) in h.iter().enumerate() {
        out[i * 4..i * 4 + 4].copy_from_slice(&word.to_be_bytes());
    }
    out
}

/// HMAC-SHA256 of `message` under `key`.
pub fn hmac_sha256(key: &[u8], message: &[u8]) -> [u8; 32] {
    let mut block = [0u8; 64];
    if key.len() > 64 {
        block[..32].copy_from_slice(&sha256(key));
    } else {
        block[..key.len()].copy_from_slice(key);
    }
    let mut inner: Vec<u8> = block.iter().map(|b| b ^ 0x36).collect();
    inner.extend_from_slice(message);
    let mut outer: Vec<u8> = block.iter().map(|b| b ^ 0x5c).collect();
    outer.extend_from_slice(&sha256(&inner));
    sha256(&outer)
}

/// Whether `mac` is the HMAC-SHA256 of `message` under `key`, compared in
/// constant time.
pub fn verify(key: &[u8], message: &[u8], mac: &[u8]) -> bool {
    let expected = hmac_sha256(key, message);
    mac.len() == expected.len() && mac.iter().zip(expected).fold(0u8, |diff, (a, b)| diff | (a ^ b)) == 0
}