如何检查上传文件的内容，而不依赖于它的扩展？ [英] How to check the content of an uploaded file without relying on its extension?

问题描述

你如何去验证一个上传文件的类型，可靠不使用扩展？我猜，你必须检查页眉/读取一些字节，但我真的不知道如何去做。 IM使用C＃和asp.net。

How do you go about verifying the type of an uploaded file reliably without using the extension? I'm guessing that you have to examine the header / read some of the bytes, but I really have no idea how to go about it. Im using c# and asp.net.

感谢您的任何建议。

好了，从上面的链接我现在知道，我找'FF FF D8 E0'来正确识别，例如.jpg文件。

ok, so from the above links I now know that I am looking for 'ff d8 ff e0' to positively identify a .jpg file for example.

在我的code我可以读头二字节没有问题：

In my code I can read the first twenty bytes no problem:

                FileStream fs = File.Open(filePath, FileMode.Open);
                Byte[] b = new byte[20];
                fs.Read(b, 0, 20);

左右（并请在此处原谅我经验不足总量），但我要如何检查的字节数组是否包含FF FF D8 E0'？

so (and please excuse my total inexperience here) but how do I check whether the byte array contains 'ff d8 ff e0'?

推荐答案

下面对你张贴的后续问题的快速和肮脏的响应：

Here's a quick-and-dirty response to the followup question you posted:

byte[] jpg = new byte[] { 0xFF, 0xD8, 0xFF, 0xE0 };
bool match = true;
for (int i = 0; i < jpg.Length; i++)
{
    if (jpg[i] != b[i])
    {
        match = false;
        break;
    }
}

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