如何使用C＃验证文件是受密码保护的ZIP文件

Question

Given a path to a file, how can I validate that the file is a password-protected zip file?

ie, how would I implement this function?

bool IsPasswordProtectedZipFile(string pathToFile)

I don't need to unzip the file -- I just need to verify that it's a ZIP and has been protected with some password.

Thanks

Answer 1

Using SharpZipLib , the following code works. And by works I mean entry.IsCrypted returns true or false based on whether or not there is a password for the first entry in the zip file.

var file = @"c:\testfile.zip";
FileStream fileStreamIn = new FileStream(file, FileMode.Open, FileAccess.Read);
ZipInputStream zipInStream = new ZipInputStream(fileStreamIn);
ZipEntry entry = zipInStream.GetNextEntry();
Console.WriteLine("IsCrypted: " + entry.IsCrypted);

There's a simple tutorial on using SharpZipLib on CodeProject .

Thus a simple implementation looks something like:

public static bool IsPasswordProtectedZipFile(string path)
{
    using (FileStream fileStreamIn = new FileStream(path, FileMode.Open, FileAccess.Read))
    using (ZipInputStream zipInStream = new ZipInputStream(fileStreamIn))
    {
        ZipEntry entry = zipInStream.GetNextEntry();
        return entry.IsCrypted;
    }
}

Note there's no real error handling or anything...

Answer 2

In ZIP archives, the password is not placed on the file, but on the individual entries within the file. A zip can contain some entries encrypted and some not. Here's some example code to check for encryption on entries in DotNetZip:

int encryptedEntries = 0;
using (var zip = ZipFile.Read(nameOfZipFile)) 
{
    // check a specific, named entry: 
    if (zip["nameOfEntry.doc"].UsesEncryption)
       Console.WriteLine("Entry 'nameOfEntry.doc' uses encryption"); 

    // check all entries: 
    foreach (var e in zip)
    {
       if (e.UsesEncryption)
       {
           Console.WriteLine("Entry {0} uses encryption", e.FileName); 
           encryptedEntries++; 
       }
    }
}

if (encryptedEntries > 0) 
    Console.WriteLine("That zip file uses encryption on {0} entrie(s)", encryptedEntries); 

If you'd prefer, you can use LINQ:

private bool ZipUsesEncryption(string archiveToRead)
{
    using (var zip = ZipFile.Read(archiveToRead))
    {
        var selection = from e in zip.Entries
            where e.UsesEncryption
            select e;

        return selection.Count > 0;
    }
}

Answer 3

At this point in the .NET Framework maturity you will need to use a 3rd party tool. There are many commercial libraries that can be Googled. I'm suggesting one free one from Microsoft's Codeplex website DotNetZip . The front page states " the library supports zip passwords ".

Answer 4

There is no 100% correct way to check if all zip entries is encrypted. every entry in a zipfile is independent and could has its own password/encrypted method.

for most cases, zipfile is zipped by some software, these software will ensure every entry in a zipfile has a common password and encrypted method.

So, using the first zipentry(not a directory) to check if that zipfile is encrypted can cover most cases.