Allow form-data with filename and filename*

[FuJa0815]

Bug Description

Currently this request cannot be parsed:

--1df6c75e-c5a7-486c-af47-67b632b19522
Content-Disposition: form-data; name="Abc"; filename="E 1962 029 1342-0003.JPG"; filename*=utf-8''E%201962%20029%201342-0003.JPG

Hello
--1df6c75e-c5a7-486c-af47-67b632b19522--

The error is TypeError: expected CRLF. Reading through the code passing a filename and a filename* is not supported. This is up to spec tho and something the C# implementation generates.

[KhafraDev]

Now that it seems to be fixed in undici, this is an issue in the C# implementation. According to RFC 7578:

NOTE: The encoding method described in [RFC5987], which would add a
"filename*" parameter to the Content-Disposition header field, MUST
NOT be used.

While receivers (such as undici) should still parse it correctly, senders shouldn't be adding it.

[FuJa0815]

I'm actually not sure on how to read this, this seems to be in conflict with https://datatracker.ietf.org/doc/html/rfc6266

Or is this a case of "well they must not do it but if somebody still does this should happen"?

[KhafraDev]

RFC 6266, I believe, is referring to content-disposition in http responses, not multipart/form-data bodies. At least, that's how I'm interpreting it.

[KhafraDev]

Before this closes, although from my limited testing it seems to be fixed, I would like to add a few tests.

• A test that explicitly ensures filename* is parsed correctly
• A test that ensures that without filename, there is an error parsing still succeeds
• A test that ensures filename* takes priority over filename when both are present

I've been busy and haven't gotten around to it