问题描述

我正在开发一个允许用户上传不同文件格式的网站.我们需要限制用户上传受密码保护的文件.

I am working on a website, which allows users to upload different file formats. We need to restrict the user from uploading password protected files.

有没有办法在上传文件之前确定 Microsoft Office 文件(Word、Powerpoint 和 Excel)是否受密码保护?根据 http://social.msdn.microsoft.com/Forums/en/oxmlsdk/thread/34701a34-f1d4-4802-9ce4-133f15039c69，我已经实现了以下内容，但它在尝试打开时抛出错误文件包含损坏的数据"受密码保护的文件.

Is there a way to determine if a Microsoft Office file (Word, Powerpoint & Excel) is password protected before uploading the file? As per http://social.msdn.microsoft.com/Forums/en/oxmlsdk/thread/34701a34-f1d4-4802-9ce4-133f15039c69, I have implemented the following, but it throws an error saying "File contains corrupted data", while trying to open a password protected file.

 using (WordprocessingDocument wordDoc = WordprocessingDocument.Open(mem, false))
 {
     DocumentProtection dp =
         wordDoc.MainDocumentPart.DocumentSettingsPart.Settings.GetFirstChild<DocumentProtection>();
     if (dp != null && dp.Enforcement == DocumentFormat.OpenXml.OnOffValue.FromBoolean(true))
     {
         return true;
     }
 }

是否有其他方法可以确定这一点?

Are there any other ways to determine this?

推荐答案

试试这个代码:

public static Boolean IsProtected(String file)
{
    Byte[] bytes = File.ReadAllBytes(file);

    String prefix = Encoding.Default.GetString(bytes.Take(2).ToArray());

    // Zip and not password protected.
    if (prefix == "PK")
        return false;

    // Office format.
    if (prefix == "ÐÏ")
    {
        // XLS 2003
        if (bytes.Skip(0x208).Take(1).ToArray()[0] == 0xFE)
            return true;

        // XLS 2005
        if (bytes.Skip(0x214).Take(1).ToArray()[0] == 0x2F)
            return true;

        // DOC 2005
        if (bytes.Skip(0x20B).Take(1).ToArray()[0] == 0x13)
            return true;

        // Guessing
        if (bytes.Length < 2000)
            return false;

        // DOC/XLS 2007+
        String start = Encoding.Default.GetString(bytes.Take(2000).ToArray()).Replace("", " ");

        if (start.Contains("E n c r y p t e d P a c k a g e"))
            return true;

        return false;
    }

    // Unknown format.
    return false;
}

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