151 lines
4.3 KiB
C#
151 lines
4.3 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using System.Security.Cryptography;
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namespace OTPNet
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{
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// Please see LICENSE.txt for information on what license this is released under
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public enum HashAlgorithm
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{
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SHA1
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}
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// This class was ported from this PHP library https://github.com/lelag/otphp which was ported from a Ruby library
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/**
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* One Time Password Generator
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*
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* The OTP class allow the generation of one-time
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* password that is described in rfc 4xxx.
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*
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* This is class is meant to be compatible with
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* Google Authenticator.
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*
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* This class was originally ported from the rotp
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* ruby library available at https://github.com/mdp/rotp
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*/
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public class OTP
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{
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/**
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* The base32 encoded secret key
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* @var string
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*/
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public string secret;
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/**
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* The algorithm used for the hmac hash function
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* @var string
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*/
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public HashAlgorithm digest;
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/**
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* The number of digits in the one-time password
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* @var integer
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*/
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public int digits;
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/**
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* Constructor for the OTP class
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* @param string $secret the secret key
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* @param array $opt options array can contain the
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* following keys :
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* @param integer digits : the number of digits in the one time password
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* Currently Google Authenticator only support 6. Defaults to 6.
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* @param string digest : the algorithm used for the hmac hash function
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* Google Authenticator only support sha1. Defaults to sha1
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*
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* @return new OTP class.
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*/
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public OTP(string secret)
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{
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this.secret = secret;
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this.digits = 6;
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this.digest = HashAlgorithm.SHA1;
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}
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public OTP(string secret, int digits)
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{
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// Issue reported by scox.nz
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// https://code.google.com/p/otpnet/issues/detail?id=2
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this.secret = secret;
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this.digits = digits;
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this.digest = HashAlgorithm.SHA1;
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}
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public OTP(string secret, int digits, HashAlgorithm digest)
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{
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this.secret = secret;
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this.digits = digits;
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this.digest = digest;
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}
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/**
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* Generate a one-time password
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*
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* @param integer $input : number used to seed the hmac hash function.
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* This number is usually a counter (HOTP) or calculated based on the current
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* timestamp (see TOTP class).
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* @return integer the one-time password
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*/
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public int generateOTP(Int64 input)
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{
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HMAC hashgenerator = null;
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switch (digest)
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{
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case HashAlgorithm.SHA1:
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hashgenerator = new HMACSHA1(Base32Encoding.ToBytes(secret));
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break;
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}
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hashgenerator.ComputeHash(intToByteString(input));
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string hash = "";
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foreach(byte b in hashgenerator.Hash)
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{
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hash += b.ToString("x2");
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}
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List<int> hmac = new List<int>();
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foreach (string s in hash.Split(2))
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{
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hmac.Add(Int32.Parse(s, System.Globalization.NumberStyles.HexNumber));
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}
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int offset = hmac[19] & 0xf;
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int code = (hmac[offset + 0] & 0x7F) << 24 |
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(hmac[offset + 1] & 0xFF) << 16 |
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(hmac[offset + 2] & 0xFF) << 8 |
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(hmac[offset + 3] & 0xFF);
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return code % (int)Math.Pow((double)10, (double)this.digits);
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}
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public byte[] intToByteString(Int64 i)
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{
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List<byte> res = new List<byte>();
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while (i != 0)
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{
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res.Add((byte)(i & 0xFF));
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i >>= 8;
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}
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int rcount = res.Count;
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for (int z = 0; z < 8 - rcount; z++)
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res.Add((byte)0);
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res.Reverse();
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return res.ToArray();
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}
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}
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}
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