Rack Middleware to automatically unzip gzipped/deflated POST data

compress_requests.rb

class CompressedRequests
  def initialize(app)
    @app = app
  end

  def method_handled?(env)
    !!(env['REQUEST_METHOD'] =~ /(POST|PUT)/)
  end

  def encoding_handled?(env)
    ['gzip', 'deflate'].include? env['HTTP_CONTENT_ENCODING']
  end
  
  def call(env)
    if method_handled?(env) && encoding_handled?(env)
      extracted = decode(env['rack.input'], env['HTTP_CONTENT_ENCODING'])

      env.delete('HTTP_CONTENT_ENCODING')
      env['CONTENT_LENGTH'] = extracted.bytesize
      env['rack.input'] = StringIO.new(extracted)
    end

    status, headers, response = @app.call(env)
    return [status, headers, response]
  end
  
  def decode(input, content_encoding)
    case content_encoding
      when 'gzip' then Zlib::GzipReader.new(input).read
      when 'deflate' then Zlib::Inflate.inflate(input.read)
    end
  end
end

I found that for a payload that uses multibyte strings, the content length was not getting set correctly. The solution is to use .bytesize instead of .length.

env['CONTENT_LENGTH'] = extracted.bytesize

Here's my fork with the fix: https://gist.github.com/mbrictson/9106778

It looks like the account name above moved, the updated location is:

https://gist.github.com/mattbrictson/9106778

config.middleware.insert_before ActionDispatch::ParamsParser, "CompressedRequests"

this does not work with rails 5.

This is fixed for the CONTENT_LENGTH issue now. I don't know Rails 5 @plentz, so if you knew what needs to go there instead, please post that here.

It's working for me in rails 6 with config.middleware.insert_after ::Rack::Sendfile, ::CompressedRequests

-    status, headers, response = @app.call(env)
-    return [status, headers, response]
+    @app.call(env)

had a similar effect 💚

Used an index in insert_before which worked in rails 5 in all envs.

    config.middleware.insert_before 0, CompressedRequests