Function verify_token

nodedb-cluster/src/auth/join_token.rs:100–125

Verify a hex-encoded token against `secret`. Returns the bound `(for_node, expiry_unix_secs)` on success. The HMAC comparison is constant-time (via `hmac::Mac::verify_slice` which uses the `subtle` crate internally).

(token_hex: &str, secret: &[u8; 32])

/// The HMAC comparison is constant-time (via `hmac::Mac::verify_slice`
/// which uses the `subtle` crate internally).
pub fn verify_token(token_hex: &str, secret: &[u8; 32]) -> Result<(u64, u64), TokenError> {
    if token_hex.len() != TOKEN_HEX_LEN {
        return Err(TokenError::WrongLength);
    }
    let bytes = hex_decode(token_hex)?;
    let (body, tag) = bytes.split_at(TOKEN_HEADER_LEN);
    let mut mac = <Hmac<Sha256>>::new_from_slice(secret).map_err(|_| TokenError::HmacKeyLength)?;
    mac.update(body);
    mac.verify_slice(tag).map_err(|_| TokenError::InvalidMac)?;
    let for_node = u64::from_le_bytes(body[..8].try_into().expect("slice is 8 bytes"));
    let expiry = u64::from_le_bytes(body[8..].try_into().expect("slice is 8 bytes"));
    let now = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|d| d.as_secs())
        .unwrap_or_else(|_| {
            tracing::error!(
                "system clock is before UNIX_EPOCH during token verification; \
                 using 0 (epoch) — check NTP/RTC configuration"
            );
            0
        });
    if now > expiry {
        return Err(TokenError::Expired);
    }
    Ok((for_node, expiry))
}

fn hex_decode(s: &str) -> Result<Vec<u8>, TokenError> {
    let mut out = Vec::with_capacity(s.len() / 2);