fn hkdf_expand_label_extracted()

in src/key_exchange/tripledh.rs [518:549]

• 29 lines of code
• 1 McCabe index (conditional complexity)

fn hkdf_expand_label_extracted<D: Hash>(
    hkdf: &Hkdf<D>,
    label: &[u8],
    context: &[u8],
) -> Result<Output<D>, ProtocolError>
where
    D::Core: ProxyHash,
    <D::Core as BlockSizeUser>::BlockSize: IsLess<U256>,
    Le<<D::Core as BlockSizeUser>::BlockSize, U256>: NonZero,
{
    let mut okm = GenericArray::default();

    let length_u16: u16 =
        u16::try_from(OutputSize::<D>::USIZE).map_err(|_| ProtocolError::SerializationError)?;
    let label = Serialize::<U1>::from_label(STR_OPAQUE, label)?;
    let label = label.to_array_3();
    let context = Serialize::<U1>::from(context)?;
    let context = context.to_array_2();

    let hkdf_label = [
        &length_u16.to_be_bytes(),
        label[0],
        label[1],
        label[2],
        context[0],
        context[1],
    ];

    hkdf.expand_multi_info(&hkdf_label, &mut okm)
        .map_err(|_| InternalError::HkdfError)?;
    Ok(okm)
}