96 lines
2.8 KiB
C#
96 lines
2.8 KiB
C#
/*
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KeePass Password Safe - The Open-Source Password Manager
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Copyright (C) 2003-2016 Dominik Reichl <dominik.reichl@t-online.de>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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using System;
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using System.Collections.Generic;
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using System.Globalization;
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using System.Text;
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#if !KeePassUAP
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using System.Security.Cryptography;
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#endif
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using KeePassLib.Utility;
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#if !KeePassLibSD
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namespace KeePassLib.Cryptography
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{
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/// <summary>
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/// Generate HMAC-based one-time passwords as specified in RFC 4226.
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/// </summary>
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public static class HmacOtp
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{
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private static readonly uint[] vDigitsPower = new uint[]{ 1, 10, 100,
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1000, 10000, 100000, 1000000, 10000000, 100000000 };
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public static string Generate(byte[] pbSecret, ulong uFactor,
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uint uCodeDigits, bool bAddChecksum, int iTruncationOffset)
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{
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byte[] pbText = MemUtil.UInt64ToBytes(uFactor);
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Array.Reverse(pbText); // To big-endian
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HMACSHA1 hsha1 = new HMACSHA1(pbSecret);
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byte[] pbHash = hsha1.ComputeHash(pbText);
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uint uOffset = (uint)(pbHash[pbHash.Length - 1] & 0xF);
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if((iTruncationOffset >= 0) && (iTruncationOffset < (pbHash.Length - 4)))
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uOffset = (uint)iTruncationOffset;
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uint uBinary = (uint)(((pbHash[uOffset] & 0x7F) << 24) |
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((pbHash[uOffset + 1] & 0xFF) << 16) |
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((pbHash[uOffset + 2] & 0xFF) << 8) |
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(pbHash[uOffset + 3] & 0xFF));
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uint uOtp = (uBinary % vDigitsPower[uCodeDigits]);
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if(bAddChecksum)
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uOtp = ((uOtp * 10) + CalculateChecksum(uOtp, uCodeDigits));
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uint uDigits = (bAddChecksum ? (uCodeDigits + 1) : uCodeDigits);
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return uOtp.ToString(NumberFormatInfo.InvariantInfo).PadLeft(
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(int)uDigits, '0');
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}
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private static readonly uint[] vDoubleDigits = new uint[]{ 0, 2, 4, 6, 8,
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1, 3, 5, 7, 9 };
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private static uint CalculateChecksum(uint uNum, uint uDigits)
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{
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bool bDoubleDigit = true;
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uint uTotal = 0;
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while(0 < uDigits--)
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{
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uint uDigit = (uNum % 10);
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uNum /= 10;
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if(bDoubleDigit) uDigit = vDoubleDigits[uDigit];
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uTotal += uDigit;
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bDoubleDigit = !bDoubleDigit;
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}
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uint uResult = (uTotal % 10);
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if(uResult != 0) uResult = 10 - uResult;
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return uResult;
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}
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}
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}
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#endif
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