fix(upload): derive R2 key extension from content type, not filename - #77
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royalpinto007 merged 2 commits intoAug 8, 2026
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getPresignedUploadUrl trusted the extension off the user-supplied filename even though contentType is already validated against ALLOWED_TYPES in the presign route. A hostile filename could put an arbitrary extension on a public object key. Map the validated content type to an extension instead, and keep the original filename only as sanitized object metadata.
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Nice work @waterlemonnn, this is merged. Genuinely helpful change for agentpostmortem. If this project helps you out, a star helps others find it too. Happy to see more from you whenever you have the time. |
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Fixes #44
getPresignedUploadUrlwas building the object key fromfilename.split(".").pop(), so the extension came straight from user input even thoughcontentTypeis already validated againstALLOWED_TYPESin the presign route. A request withcontentType: "image/png"andfilename: "x.html"produced a key ending in.html.Extension is now derived from a
contentType -> extensionmap, falling back tobinfor anything unrecognized. The original filename is no longer used for the key at all — kept only as sanitized metadata on the object (Metadata["original-filename"]) in case it's useful later.Tests in
lib/r2/upload.test.tscover each allowed content type, an unrecognized type, a hostile filename that shouldn't be able to influence the key, and the metadata sanitization.npx vitest run(105/105),npx tsc --noEmit, andnpx eslintall clean.