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Jeremy Daer
3a140f65b2
Uploaded files come from this origin, so one served with a JavaScript
type could run as one of the app's own scripts. Browsers accept sixteen
spellings of that type, and Disk URLs sign the type they were minted
with, so refusing a list of types at upload can't cover links already
out there. Instead, a middleware rewrites the type of anything Active
Storage reads out that isn't plainly media, a PDF or plain text to
application/octet-stream, whatever the URL says.
(cherry picked from commit cad2d7211d)
32 lines
1.4 KiB
Ruby
32 lines
1.4 KiB
Ruby
# Uploaded files are served from this origin, so under script-src 'self' an
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# upload served with any JavaScript MIME type would run as one of our scripts.
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# Browsers accept sixteen spellings of that type, and Disk URLs sign the type
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# they were minted with, so a list of types to refuse can't cover old links.
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# Instead, anything Active Storage serves that isn't plainly media goes out as
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# a download, whatever its URL says. Only reads are touched: uploading
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# (direct upload JSON, Disk PUT) answers in its own types.
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#
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# Accepted on upgrade: a browser that cached an upload under a script type
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# before this guard shipped can still run it from that cache until the entry
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# expires, up to an hour after it was fetched (config/initializers/active_storage.rb).
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# Revalidation doesn't help, since a 304 carries no content type.
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class UploadedScriptGuard
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SERVABLE = %r{\A(image|video|audio)/|\A(application/pdf|application/octet-stream|text/plain)\z}
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def initialize(app)
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@app = app
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end
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def call(env)
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status, headers, body = @app.call(env)
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if env["REQUEST_METHOD"].in?(%w[ GET HEAD ]) && env["PATH_INFO"].start_with?("#{ActiveStorage.routes_prefix}/") && (type = headers["content-type"])
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headers["content-type"] = ActiveStorage.binary_content_type unless type.split(";").first.strip.downcase.match?(SERVABLE)
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end
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[ status, headers, body ]
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end
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end
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Rails.application.config.middleware.use UploadedScriptGuard
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