Function write_envelope

nodedb-cluster/src/rpc_codec/auth_envelope.rs:62–93

Wrap `inner_frame` in an authenticated envelope, appending to `out`. MAC covers `[env_ver, from_node_id, seq, inner_len, inner_frame]`.

(
    from_node_id: u64,
    seq: u64,
    inner_frame: &[u8],
    key: &MacKey,
    out: &mut Vec<u8>,
)

///
/// MAC covers `[env_ver, from_node_id, seq, inner_len, inner_frame]`.
pub fn write_envelope(
    from_node_id: u64,
    seq: u64,
    inner_frame: &[u8],
    key: &MacKey,
    out: &mut Vec<u8>,
) -> Result<()> {
    let inner_len: u32 = inner_frame
        .len()
        .try_into()
        .map_err(|_| ClusterError::Codec {
            detail: format!("inner frame too large: {} bytes", inner_frame.len()),
        })?;
    if inner_len > MAX_RPC_PAYLOAD_SIZE {
        return Err(ClusterError::Codec {
            detail: format!(
                "inner frame length {inner_len} exceeds maximum {MAX_RPC_PAYLOAD_SIZE}"
            ),
        });
    }

    let start = out.len();
    out.reserve(ENVELOPE_OVERHEAD + inner_frame.len());
    out.push(ENVELOPE_VERSION);
    out.extend_from_slice(&from_node_id.to_le_bytes());
    out.extend_from_slice(&seq.to_le_bytes());
    out.extend_from_slice(&inner_len.to_le_bytes());
    out.extend_from_slice(inner_frame);
    let tag = compute_hmac(key, &out[start..]);
    out.extend_from_slice(&tag);
    Ok(())
}

/// Validate the envelope + MAC and return `(fields, inner_frame)`.
///