Ignore RFC 2231 extended parameters in parse_options_header#291
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Replace `email.message.Message` with a small vendored `_parseparam` splitter and ignore the RFC 5987/2231 extended syntax (`name*`, `filename*`, and their continuations), keeping the plain parameter authoritative per RFC 7578 §4.2.
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parse_options_headerparsed Content-Type/Content-Disposition headers withemail.message.Message, which transparently applies RFC 2231/5987 decoding: afilename*=utf-8''valueparameter is percent-decoded and surfaced under the barefilenamekey,name*likewise, andfilename*0/filename*1continuations are reassembled. RFC 7578 §4.2 states this extended syntax MUST NOT be used inmultipart/form-data.This replaces
email.message.Messagewith a small vendored copy of the stdlib'semail.message._parseparamto split the header into its;-separated parts (correctly ignoring;inside quoted strings), and then ignores any*-suffixed parameter. The plainname/filenameis now authoritative, matchingurllib.parse, browsers, and other compliant parsers - none of which emit the extended form.Beyond ignoring the extended parameters, behaviour is unchanged: content-type casing, quoted values, backslash unquoting, the IE6 path fix, and parameter casing all match the previous implementation. Dropping
Messagealso removes the fuzz-driventry/exceptaroundget_params()and its Python 3.12-only special case.AI Disclaimer
This PR was developed with the assistance of either Claude or Codex. I've reviewed and verified the changes.