Thin wrapper around OTP's :CryptographicMessageSyntax-2009 ASN.1 codec for CMS structures.

The OTP codec returns {:error, {:asn1, reason}} with deeply nested internal stack frames on failure. This module flattens those into flat {:error, {:cms_codec, type, reason}} tuples that compose with the rest of pkcs11ex's with chains.

Encoding shape

The codec accepts Elixir tuples shaped after the ASN.1 type definitions in OTP's CryptographicMessageSyntax-2009.asn1. Some shape rules:

• Records are represented as tagged tuples with the type name as first element. E.g., ContentInfo is {:ContentInfo, oid, content}.
• OPTIONAL fields use the atom :asn1_NOVALUE when absent.
• For ContentInfo, the content field is parameterised by contentType via the information-object-class table — pass the inner term directly (not wrapped as {:asn1_OPENTYPE, der}). The codec recurses.
• For genuinely opaque fields (Attribute.values SET OF ANY), wrap bytes as {:asn1_OPENTYPE, der_bytes} — the codec emits them verbatim.

Examples

iex> oid_signed_data = SignCore.CMS.OIDs.id_signed_data()
iex> oid_data = SignCore.CMS.OIDs.id_data()
iex> oid_sha256 = SignCore.CMS.OIDs.id_sha256()
iex> inner = {
...>   :SignedData, 1,
...>   [{:DigestAlgorithmIdentifier, oid_sha256, :asn1_NOVALUE}],
...>   {:EncapsulatedContentInfo, oid_data, :asn1_NOVALUE},
...>   :asn1_NOVALUE, :asn1_NOVALUE, []
...> }
iex> ci = {:ContentInfo, oid_signed_data, inner}
iex> {:ok, der} = SignCore.CMS.Codec.encode(:ContentInfo, ci)
iex> {:ok, decoded} = SignCore.CMS.Codec.decode(:ContentInfo, der)
iex> match?({:ContentInfo, ^oid_signed_data, _}, decoded)
true