c# 使用谷歌身份验证GoogleAuthenticator的示例

public class GoogleAuthenticator
  {
    private readonly static DateTime _epoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
    private TimeSpan DefaultClockDriftTolerance { get; set; }

    public GoogleAuthenticator()
    {
      DefaultClockDriftTolerance = TimeSpan.FromMinutes(5);
    }

    /// <summary>
    /// Generate a setup code for a Google Authenticator user to scan
    /// </summary>
    /// <param name="issuer">Issuer ID (the name of the system, i.e. 'MyApp'), can be omitted but not recommended https://github.com/google/google-authenticator/wiki/Key-Uri-Format </param>
    /// <param name="accountTitleNoSpaces">Account Title (no spaces)</param>
    /// <param name="accountSecretKey">Account Secret Key</param>
    /// <param name="QRPixelsPerModule">Number of pixels per QR Module (2 pixels give ~ 100x100px QRCode)</param>
    /// <returns>SetupCode object</returns>
    public SetupCode GenerateSetupCode(string issuer, string accountTitleNoSpaces, string accountSecretKey, int QRPixelsPerModule)
    {
      byte[] key = Encoding.UTF8.GetBytes(accountSecretKey);
      return GenerateSetupCode(issuer, accountTitleNoSpaces, key, QRPixelsPerModule);
    }

    /// <summary>
    /// Generate a setup code for a Google Authenticator user to scan
    /// </summary>
    /// <param name="issuer">Issuer ID (the name of the system, i.e. 'MyApp'), can be omitted but not recommended https://github.com/google/google-authenticator/wiki/Key-Uri-Format </param>
    /// <param name="accountTitleNoSpaces">Account Title (no spaces)</param>
    /// <param name="accountSecretKey">Account Secret Key as byte[]</param>
    /// <param name="QRPixelsPerModule">Number of pixels per QR Module (2 = ~120x120px QRCode)</param>
    /// <returns>SetupCode object</returns>
    public SetupCode GenerateSetupCode(string issuer, string accountTitleNoSpaces, byte[] accountSecretKey, int QRPixelsPerModule)
    {
      if (accountTitleNoSpaces == null) { throw new NullReferenceException("Account Title is null"); }
      accountTitleNoSpaces = RemoveWhitespace(accountTitleNoSpaces);
      string encodedSecretKey = Base32Encoding.ToString(accountSecretKey);
      string provisionUrl = null;
      provisionUrl = String.Format("otpauth://totp/{2}:{0}?secret={1}&issuer={2}", accountTitleNoSpaces, encodedSecretKey.Replace("=",""), UrlEncode(issuer));



      using (QRCodeGenerator qrGenerator = new QRCodeGenerator())
      using (QRCodeData qrCodeData = qrGenerator.CreateQrCode(provisionUrl, QRCodeGenerator.ECCLevel.M))
      using (QRCode qrCode = new QRCode(qrCodeData))
      using (Bitmap qrCodeImage = qrCode.GetGraphic(QRPixelsPerModule))
      using (MemoryStream ms = new MemoryStream())
      {
        qrCodeImage.Save(ms, System.Drawing.Imaging.ImageFormat.Png);

        return new SetupCode(accountTitleNoSpaces, encodedSecretKey, String.Format("data:image/png;base64,{0}", Convert.ToBase64String(ms.ToArray())));
      }

    }

    private static string RemoveWhitespace(string str)
    {
      return new string(str.Where(c => !Char.IsWhiteSpace(c)).ToArray());
    }

    private string UrlEncode(string value)
    {
      StringBuilder result = new StringBuilder();
      string validChars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_.~";

      foreach (char symbol in value)
      {
        if (validChars.IndexOf(symbol) != -1)
        {
          result.Append(symbol);
        }
        else
        {
          result.Append('%' + String.Format("{0:X2}", (int)symbol));
        }
      }

      return result.ToString().Replace(" ", "%20");
    }

    public string GeneratePINAtInterval(string accountSecretKey, long counter, int digits = 6)
    {
      return GenerateHashedCode(accountSecretKey, counter, digits);
    }

    internal string GenerateHashedCode(string secret, long iterationNumber, int digits = 6)
    {
      byte[] key = Encoding.UTF8.GetBytes(secret);
      return GenerateHashedCode(key, iterationNumber, digits);
    }

    internal string GenerateHashedCode(byte[] key, long iterationNumber, int digits = 6)
    {
      byte[] counter = BitConverter.GetBytes(iterationNumber);

      if (BitConverter.IsLittleEndian)
      {
        Array.Reverse(counter);
      }

      HMACSHA1 hmac = new HMACSHA1(key);

      byte[] hash = hmac.ComputeHash(counter);

      int offset = hash[hash.Length - 1] & 0xf;

      // Convert the 4 bytes into an integer, ignoring the sign.
      int binary =
        ((hash[offset] & 0x7f) << 24)
        | (hash[offset + 1] << 16)
        | (hash[offset + 2] << 8)
        | (hash[offset + 3]);

      int password = binary % (int)Math.Pow(10, digits);
      return password.ToString(new string('0', digits));
    }

    private long GetCurrentCounter()
    {
      return GetCurrentCounter(DateTime.UtcNow, _epoch, 30);
    }

    private long GetCurrentCounter(DateTime now, DateTime epoch, int timeStep)
    {
      return (long)(now - epoch).TotalSeconds / timeStep;
    }

    public bool ValidateTwoFactorPIN(string accountSecretKey, string twoFactorCodeFromClient)
    {
      return ValidateTwoFactorPIN(accountSecretKey, twoFactorCodeFromClient, DefaultClockDriftTolerance);
    }

    public bool ValidateTwoFactorPIN(string accountSecretKey, string twoFactorCodeFromClient, TimeSpan timeTolerance)
    {
      var codes = GetCurrentPINs(accountSecretKey, timeTolerance);
      return codes.Any(c => c == twoFactorCodeFromClient);
    }

    public string[] GetCurrentPINs(string accountSecretKey, TimeSpan timeTolerance)
    {
      List<string> codes = new List<string>();
      long iterationCounter = GetCurrentCounter();
      int iterationOffset = 0;

      if (timeTolerance.TotalSeconds > 30)
      {
        iterationOffset = Convert.ToInt32(timeTolerance.TotalSeconds / 30.00);
      }

      long iterationStart = iterationCounter - iterationOffset;
      long iterationEnd = iterationCounter + iterationOffset;

      for (long counter = iterationStart; counter <= iterationEnd; counter++)
      {
        codes.Add(GeneratePINAtInterval(accountSecretKey, counter));
      }

      return codes.ToArray();
    }
  }

其中GenerateSetupCode 这个方法是用于把绑定的密钥直接转成二维码图片，然后再转成base64图片 输出再页面上，这样在APP上直接用扫一扫即可绑定。

二丶由于生成的密钥不可以直接使用，需要进行Base32进行编码。下面是Base32Encoding类

public class Base32Encoding
  {
    /// <summary>
    /// Base32 encoded string to byte[]
    /// </summary>
    /// <param name="input">Base32 encoded string</param>
    /// <returns>byte[]</returns>
    public static byte[] ToBytes(string input)
    {
      if (string.IsNullOrEmpty(input))
      {
        throw new ArgumentNullException("input");
      }

      input = input.TrimEnd('='); //remove padding characters
      int byteCount = input.Length * 5 / 8; //this must be TRUNCATED
      byte[] returnArray = new byte[byteCount];

      byte curByte = 0, bitsRemaining = 8;
      int mask = 0, arrayIndex = 0;

      foreach (char c in input)
      {
        int cValue = CharToValue(c);

        if (bitsRemaining > 5)
        {
          mask = cValue << (bitsRemaining - 5);
          curByte = (byte)(curByte | mask);
          bitsRemaining -= 5;
        }
        else
        {
          mask = cValue >> (5 - bitsRemaining);
          curByte = (byte)(curByte | mask);
          returnArray[arrayIndex++] = curByte;
          curByte = (byte)(cValue << (3 + bitsRemaining));
          bitsRemaining += 3;
        }
      }

      //if we didn't end with a full byte
      if (arrayIndex != byteCount)
      {
        returnArray[arrayIndex] = curByte;
      }

      return returnArray;
    }

    /// <summary>
    /// byte[] to Base32 string, if starting from an ordinary string use Encoding.UTF8.GetBytes() to convert it to a byte[]
    /// </summary>
    /// <param name="input">byte[] of data to be Base32 encoded</param>
    /// <returns>Base32 String</returns>
    public static string ToString(byte[] input)
    {
      if (input == null || input.Length == 0)
      {
        throw new ArgumentNullException("input");
      }

      int charCount = (int)Math.Ceiling(input.Length / 5d) * 8;
      char[] returnArray = new char[charCount];

      byte nextChar = 0, bitsRemaining = 5;
      int arrayIndex = 0;

      foreach (byte b in input)
      {
        nextChar = (byte)(nextChar | (b >> (8 - bitsRemaining)));
        returnArray[arrayIndex++] = ValueToChar(nextChar);

        if (bitsRemaining < 4)
        {
          nextChar = (byte)((b >> (3 - bitsRemaining)) & 31);
          returnArray[arrayIndex++] = ValueToChar(nextChar);
          bitsRemaining += 5;
        }

        bitsRemaining -= 3;
        nextChar = (byte)((b << bitsRemaining) & 31);
      }

      //if we didn't end with a full char
      if (arrayIndex != charCount)
      {
        returnArray[arrayIndex++] = ValueToChar(nextChar);
        while (arrayIndex != charCount) returnArray[arrayIndex++] = '='; //padding
      }

      return new string(returnArray);
    }

    private static int CharToValue(char c)
    {
      int value = (int)c;

      //65-90 == uppercase letters
      if (value < 91 && value > 64)
      {
        return value - 65;
      }
      //50-55 == numbers 2-7
      if (value < 56 && value > 49)
      {
        return value - 24;
      }
      //97-122 == lowercase letters
      if (value < 123 && value > 96)
      {
        return value - 97;
      }

      throw new ArgumentException("Character is not a Base32 character.", "c");
    }

    private static char ValueToChar(byte b)
    {
      if (b < 26)
      {
        return (char)(b + 65);
      }

      if (b < 32)
      {
        return (char)(b + 24);
      }

      throw new ArgumentException("Byte is not a value Base32 value.", "b");
    }
  }

三丶主程序里面直接调用方法

 private SetupCode Google(string key, string Guids)
 {
   GoogleAuthenticator gat = new GoogleAuthenticator();
   return gat.GenerateSetupCode("Supported Giving", key, Guids, 5);
 }

//key系统的账号，Guid是进行加密的字符串，要求唯一，不然密钥会重复，所以这里使用Guid.   2为二维码的大小约120x120px。

SetupCode结果类为

public class SetupCode
  {
    public string Account { get; internal set; }
    public string AccountSecretKey { get; internal set; }
    public string ManualEntryKey { get; internal set; }
    /// <summary>
    /// Base64-encoded PNG image
    /// </summary>
    public string QrCodeSetupImageUrl { get; internal set; }
}

ManualEntryKey 是手机绑定的密钥。如果想手动输入密钥绑定就使用此字符串。
QrCodeSetupImageUrl 是将密钥转成的二维码图片

下载这个APP

GoogleAuthenticator gat = new GoogleAuthenticator();
var result = gat.ValidateTwoFactorPIN(parameters["Guids"].ToString(), parameters["CheckCode"].ToString());
if (result)
{
return "True";
}
else
{
return "False";
}