openpgp: Add optional parameters to unknown S2K variants.

  - This mirrors how we handle other unknown variants.  However, since
    we do not know the length of the parameters for unknown S2K
    variants, we cannot parse them back.  To work around that, the
    parameter field is optional, and will be `None` when an unknown
    S2K is parsed.  The data is not lost, but stored in the packet
    containing the S2K object, so that we can serialize it again.

  - Carefully preserve the invariant that we can parse any packet we
    can serialize by comparing the serialized form of the packet
    fragments containing the S2K and any fields the parameters of
    unknown variants bleed into on parsing.

  - Unfortunately, this means that S2K on its own no longer
    roundtrips.  Remove that test accordingly.

0 files changed, 0 insertions, 0 deletions