SymmetricImportExportExtensions.cs

Go to the documentation of this file.

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
 
namespace Internal.Cryptography;
 
internal static class SymmetricImportExportExtensions
{
    private static readonly CngKeyBlobFormat s_cipherKeyBlobFormat = new CngKeyBlobFormat("CipherKeyBlob");
 
    public static byte[] GetSymmetricKeyDataIfExportable(this CngKey cngKey, string algorithm)
    {
        byte[] buffer = cngKey.Export(s_cipherKeyBlobFormat);
        using MemoryStream input = new MemoryStream(buffer);
        using BinaryReader binaryReader = new BinaryReader(input, Encoding.Unicode);
        int num = binaryReader.ReadInt32();
        if (num != 16)
        {
            throw new CryptographicException(System.SR.Cryptography_KeyBlobParsingError);
        }
        int num2 = binaryReader.ReadInt32();
        if (num2 != 1380470851)
        {
            throw new CryptographicException(System.SR.Cryptography_KeyBlobParsingError);
        }
        int num3 = binaryReader.ReadInt32();
        binaryReader.ReadInt32();
        string text = new string(binaryReader.ReadChars(num3 / 2 - 1));
        if (text != algorithm)
        {
            throw new CryptographicException(System.SR.Format(System.SR.Cryptography_CngKeyWrongAlgorithm, text, algorithm));
        }
        if (binaryReader.ReadChar() != 0)
        {
            throw new CryptographicException(System.SR.Cryptography_KeyBlobParsingError);
        }
        int num4 = binaryReader.ReadInt32();
        if (num4 != 1296188491)
        {
            throw new CryptographicException(System.SR.Cryptography_KeyBlobParsingError);
        }
        int num5 = binaryReader.ReadInt32();
        if (num5 != 1)
        {
            throw new CryptographicException(System.SR.Cryptography_KeyBlobParsingError);
        }
        int count = binaryReader.ReadInt32();
        return binaryReader.ReadBytes(count);
    }
}