busboy reads the Content-Disposition filename="..." header value as
latin1 by default - even with defParamCharset:'utf8' set, that option
only applies to RFC 5987 encoded filename*=... params, which most
clients (browsers, curl, programmatic HTTP) don't send. Modern clients
send raw UTF-8 bytes for non-ASCII filenames; busboy interprets those
bytes one-byte-per-char as latin1, producing a JS string like 'A-tilde
+ quarter-mark' for 'u-umlaut'. JS then re-encodes that string as UTF-8
on the way to SQLite, yielding 4 bytes (c3 83 c2 bc) for what should be
2 bytes (c3 bc). Classic double-encoding mojibake - shows up in the UI
as 'BegrA-tilde...' instead of 'Begru-umlaut...'.
Fix: in the multer filename callback, re-decode file.originalname from
latin1 to utf8 to recover the original byte sequence. Mutating
originalname here propagates to every route handler reading
req.file.originalname (POST /, PUT /:id/replace, and any future upload
route using the same middleware).
This is the actual visible-mojibake bug semetra22 reported. The prior
commit b677752 (NFC normalize in safeFilename) handles a separate but
related case (macOS NFD clients sending decomposed forms); both fixes
compose correctly - latin1->utf8 first restores the byte sequence,
then NFC normalize collapses NFD into composed form.
Smoke verified by sending raw UTF-8 multipart from a Node https client
(no shell escaping). NFC input 'Begru-umlaut-essungsscreens.jpg' with
bytes c3bc c39f arrives clean (was c383c2bc c383c29f before). NFD input
'u + combining diaeresis' arrives as composed NFC c3bc after both fixes.
multer/busboy decode multipart filename headers as latin1 by default,
which mangled umlauts and other non-ASCII characters end-to-end
(Größe.jpg arrived as Größe.jpg and was stored that way). Setting
defParamCharset: 'utf8' on the multer options makes the entire
upload pipeline consistent UTF-8.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
ScreenTinker - open source digital signage management software.
MIT License, all features included, no license gates.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
