检测到该文件受 Microsoft Azure 信息保护保护

Question

Currently, our app doesn't support files that are protected by Azure/Microsoft Information Protection ( https://learn.microsoft.com/en-us/azure/information-protection/what-is-information-protection ). I want to inform the user that our app doesn't support these files or give them a warning that functionalities are more limited.

I have found one way to peek if the file is protected here: https://learn.microsoft.com/en-us/information-protection/develop/quick-app-initialization-csharp

Although this could work, it is too much overhead to configure this approach.

Is there a fast, simple clean way to know that a file is protected by Azure/Microsoft Information Protection?

For Word, Excel and PowerPoint documents, I could try to open these files as ZIP files (because Office document files are ZIP files) and look for an 'EncryptedPackage' file in the root folder. But maybe there is a more conventional way.

Answer 1

For Word, Excel and PowerPoint documents we can zip and unzip files using System.IO.Compression

Zip file:

Unzip Files:

Snippet for Encryption and Decryption of text

            string Path = @"C:\Static\";
            string zipPath = @"C:\Temp\Zip\result.zip";

            //To Zip the files
            ZipFile.CreateFromDirectory(Path, zipPath);

            //to Unzip the files
            ZipFile.ExtractToDirectory(zipPath, @"C:\UnZipped\");

Encryption Code:

           byte[] key_Array;
            byte[] Encrypt_Array = UTF8Encoding.UTF8.GetBytes(txtPlain.Text);

            string key = "Some Securty Key";
            if (true)
            {
                MD5CryptoServiceProvider hashingMd5 = new MD5CryptoServiceProvider();
                keyArray = hashingMd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
                hashingMd5.Clear();
            }
            TripleDESCryptoServiceProvider tdesSp = new TripleDESCryptoServiceProvider();
            tdesSp.Key = key_Array;
            tdesSp.Mode = CipherMode.ECB;
            tdesSp.Padding = PaddingMode.PKCS7;

            ICryptoTransform cTransform = tdesSp.CreateEncryptor();
            byte[] result_Array = cTransform.TransformFinalBlock(Encrypt_Array, 0, Encrypt_Array.Length);
            

For File protection need to use the below namespace

using Microsoft.Office.Interop.Excel- excel
using Microsoft.Office.Interop.Word - word

WorkbookObject.Password = password; WorkbookObject.SaveAs("FileName.xls")

for more information on file protection use this link

Answer 2

I was also looking for the solution to this. I found following links helpful:

https://learn.microsoft.com/en-us/information-protection/develop/concept-mip-metadata

https://learn.microsoft.com/en-us/information-protection/develop/concept-mip-metadata#contentbits

We use apache tika as parser, through OOXMLParser we get the metadata of the file.

As per the documentation:

When a file is labeled with MIP SDK, the only outcomes for contentBits will be 0x0 if the file is unprotected or 0x8 if the file is protected