Function parse_envelope

nodedb-cluster/src/rpc_codec/auth_envelope.rs:99–144

Validate the envelope + MAC and return `(fields, inner_frame)`. `data` must be the entire envelope — nothing before the version byte, nothing after the MAC tag.

(data: &'a [u8], key: &MacKey)

/// `data` must be the entire envelope — nothing before the version byte,
/// nothing after the MAC tag.
pub fn parse_envelope<'a>(data: &'a [u8], key: &MacKey) -> Result<(EnvelopeFields, &'a [u8])> {
    if data.len() < ENVELOPE_OVERHEAD {
        return Err(ClusterError::Codec {
            detail: format!(
                "envelope too short: {} bytes, need at least {ENVELOPE_OVERHEAD}",
                data.len()
            ),
        });
    }

    let version = data[OFF_VERSION];
    if version != ENVELOPE_VERSION {
        return Err(ClusterError::Codec {
            detail: format!("unsupported envelope version {version}, expected {ENVELOPE_VERSION}"),
        });
    }

    let from_node_id = u64::from_le_bytes(data[OFF_FROM_NODE..OFF_SEQ].try_into().expect("invariant: ENVELOPE_OVERHEAD/total-length checks above guarantee field bytes within bounds"));
    let seq = u64::from_le_bytes(data[OFF_SEQ..OFF_INNER_LEN].try_into().expect("invariant: ENVELOPE_OVERHEAD/total-length checks above guarantee field bytes within bounds"));
    let inner_len = u32::from_le_bytes(data[OFF_INNER_LEN..ENV_HEADER_LEN].try_into().expect("invariant: ENVELOPE_OVERHEAD/total-length checks above guarantee field bytes within bounds"));

    if inner_len > MAX_RPC_PAYLOAD_SIZE {
        return Err(ClusterError::Codec {
            detail: format!(
                "envelope inner length {inner_len} exceeds maximum {MAX_RPC_PAYLOAD_SIZE}"
            ),
        });
    }

    let inner_end = ENV_HEADER_LEN + inner_len as usize;
    let expected_total = inner_end + MAC_LEN;
    if data.len() != expected_total {
        return Err(ClusterError::Codec {
            detail: format!(
                "envelope length mismatch: got {} bytes, expected {expected_total}",
                data.len()
            ),
        });
    }

    let tag: &[u8; MAC_LEN] = data[inner_end..].try_into().expect("invariant: ENVELOPE_OVERHEAD/total-length checks above guarantee field bytes within bounds");
    verify_hmac(key, &data[..inner_end], tag)?;

    let inner_frame = &data[ENV_HEADER_LEN..inner_end];
    Ok((EnvelopeFields { from_node_id, seq }, inner_frame))
}

#[cfg(test)]
mod tests {