143 lines
3.6 KiB
C#
143 lines
3.6 KiB
C#
/*
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KeePass Password Safe - The Open-Source Password Manager
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Copyright (C) 2003-2017 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.Diagnostics;
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using System.Text;
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namespace KeePassLib.Cryptography.KeyDerivation
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{
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public abstract class KdfEngine
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{
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public abstract PwUuid Uuid
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{
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get;
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}
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public abstract string Name
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{
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get;
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}
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public virtual KdfParameters GetDefaultParameters()
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{
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return new KdfParameters(this.Uuid);
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}
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/// <summary>
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/// Generate random seeds and store them in <paramref name="p" />.
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/// </summary>
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public virtual void Randomize(KdfParameters p)
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{
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Debug.Assert(p != null);
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Debug.Assert(p.KdfUuid.Equals(this.Uuid));
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}
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public abstract byte[] Transform(byte[] pbMsg, KdfParameters p);
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public virtual KdfParameters GetBestParameters(uint uMilliseconds)
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{
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throw new NotImplementedException();
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}
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protected void MaximizeParamUInt64(KdfParameters p, string strName,
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ulong uMin, ulong uMax, uint uMilliseconds, bool bInterpSearch)
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{
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if(p == null) { Debug.Assert(false); return; }
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if(string.IsNullOrEmpty(strName)) { Debug.Assert(false); return; }
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if(uMin > uMax) { Debug.Assert(false); return; }
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if(uMax > (ulong.MaxValue >> 1))
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{
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Debug.Assert(false);
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uMax = ulong.MaxValue >> 1;
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if(uMin > uMax) { p.SetUInt64(strName, uMin); return; }
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}
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byte[] pbMsg = new byte[32];
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for(int i = 0; i < pbMsg.Length; ++i) pbMsg[i] = (byte)i;
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ulong uLow = uMin;
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ulong uHigh = uMin + 1UL;
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long tLow = 0;
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long tHigh = 0;
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long tTarget = (long)uMilliseconds;
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// Determine range
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while(uHigh <= uMax)
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{
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p.SetUInt64(strName, uHigh);
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// GC.Collect();
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Stopwatch sw = Stopwatch.StartNew();
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Transform(pbMsg, p);
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sw.Stop();
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tHigh = sw.ElapsedMilliseconds;
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if(tHigh > tTarget) break;
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uLow = uHigh;
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tLow = tHigh;
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uHigh <<= 1;
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}
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if(uHigh > uMax) { uHigh = uMax; tHigh = 0; }
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if(uLow > uHigh) uLow = uHigh; // Skips to end
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// Find optimal number of iterations
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while((uHigh - uLow) >= 2UL)
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{
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ulong u = (uHigh + uLow) >> 1; // Binary search
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// Interpolation search, if possible
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if(bInterpSearch && (tLow > 0) && (tHigh > tTarget) &&
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(tLow <= tTarget))
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{
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u = uLow + (((uHigh - uLow) * (ulong)(tTarget - tLow)) /
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(ulong)(tHigh - tLow));
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if((u >= uLow) && (u <= uHigh))
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{
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u = Math.Max(u, uLow + 1UL);
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u = Math.Min(u, uHigh - 1UL);
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}
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else
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{
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Debug.Assert(false);
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u = (uHigh + uLow) >> 1;
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}
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}
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p.SetUInt64(strName, u);
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// GC.Collect();
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Stopwatch sw = Stopwatch.StartNew();
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Transform(pbMsg, p);
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sw.Stop();
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long t = sw.ElapsedMilliseconds;
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if(t == tTarget) { uLow = u; break; }
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else if(t > tTarget) { uHigh = u; tHigh = t; }
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else { uLow = u; tLow = t; }
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}
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p.SetUInt64(strName, uLow);
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}
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}
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}
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