Python's email
module provides a set of parsers for email messages, among them:
bytes
sequence and produces an EmailMessage
, with all of its data and meta-data kept in memory;
The problem with the first approach is that if we choose to encrypt an EmailMessage
, its contents is serialised by an appropriate email.generator implementation, instead of producing the original content. This is OK for payloads like text in pure ASCII or Unicode with Latin scripts, but things get tricky when we want to transfer non-Latin scripts (e.g. Japanese, Chinese, or any of the Cyrillic alphabets). (This is mostly caused by different Content-Transfer-Encoding
being chosen by email.generator
.)
BytesHeaderParser
and its string counterpart let us only parse the headers and keep original message body in memory. The drawback is that we can't process multipart messages as sequences of MIME entities, which we need for one of the Lacre's modes of operation. (There are two: PGP/MIME with whole body encrypted and PGP/Inline with each part of multipart message encrypted separately.) We could use BytesHeaderParser
with PGP/MIME only, because a multipart message would be impossible to handle in PGP/Inline mode.
It turns out that we can avoid some of the transformations:
To achieve that, we'd need to adjust the flow and:
Envelope
initially to identify identities and prepare for encryption.lacre.core
, function delivery_plan
).