c# - 音频的Base64验证

Question

实际上，我想在API中接收base64，但我想允许仅包含音频的base64 ，下面是我验证base64的功能，但是在Convert.FromBase64String(base64String);之前，我想验证该base64是音频。

public static int CheckAudio(string base64String)
        {

            if (string.IsNullOrEmpty(base64String) || base64String.Length % 4 != 0
               || base64String.Contains(" ") || base64String.Contains("\t") || base64String.Contains("\r") || base64String.Contains("\n"))
                return (int)ConfezzStatusCode.InValidParamter;

            try
            {
                 Convert.FromBase64String(base64String);
                    return (int)HttpStatusCode.OK;
            }
            catch
            {
                // Handle the exception
                return (int)ConfezzStatusCode.InValidParamter;
            }
        }

注意:我只允许音频文件。

Answer 1

您可以使用file signatures来检测它是否是已知的音频格式。像这样:

// Decode the whole string to make sure it is a valid Base64
byte[] data = Convert.FromBase64String(base64String);

// Just for readability store it as HEX
// You might want to store only the file header (eg, 64 bytes)
string hex = BitConverter.ToString(data);

if (hex.StartsWith("49-44-33"))
{
  Console.WriteLine("mp3");
}
else if (hex.StartsWith("66-4C-61-43"))
{
  Console.WriteLine("flac");
}
else {
  Console.WriteLine("unknown:" + hex);
}

有关更多想法，请检查:

Using .NET, how can you find the mime type of a file based on the file signature not the extension

In C#, how can I know the file type from a byte[]?