MIME类型检查无用于文件上传？ （特别是使用Javascript File API）？ [英] MIME type check useless for file upload? (in particular, using the Javascript File API)?

问题描述

客户端，使用文件 W3C File API ）和类似于这一行的代码：



  if（file.type.indexOf（text）== 0）{...} 
  

可以执行文件类型的检查。显然，这使用 MIME类型（它返回这些字符串）。

在我的旅途中，我冒险通过这个有价值的贡献者，他认为MIME类型是无用的。

在文件上传的情况下，MIME类型确实基本没用，因此任何类型的检查都应该发生在服务器端？

解决方案

贡献者是正确的。您不能仅仅依靠MIME类型检查来真正验证文件。这仅用于快速查找。例如，在客户端，可以在发送到服务器之前检查文件的MIME类型，以防用户选择错误的文件类型，从而节省时间和带宽。道歉自由使用逗号！

I've got a server script receiving an uploaded file from Javascript.

Client-side, using a File object (from the W3C File API) and code similar to this line:

if (file.type.indexOf("text") == 0) { ... }

one can perform a check of the file type. Apparently, this uses a MIME type (which returns these strings).

In my journeys here through SO, I ventured across this worthy contributor, who maintains that MIME types are useless.

Are MIME types indeed basically useless in a file upload situation, and any type checking should therefore occur server-side?

解决方案

The contributer is correct. You can't rely merely on MIME type checking to truly validate a file. It's only useful for quick lookups. For instance, on the client side, you can check the MIME type of a file before it is sent to the server, just in case the user chose the wrong file type, saving time and bandwidth. Apologies for the liberal use of commas!

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