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/*
KeePass Password Safe - The Open-Source Password Manager
Copyright (C) 2003-2021 Dominik Reichl <dominik.reichl@t-online.de>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Diagnostics;
namespace KeePass.Util.SendInputExt
{
internal static class SiObf
{
public static void Obfuscate(List<SiEvent> l)
{
if(l == null) { Debug.Assert(false); return; }
int n = l.Count;
if(n <= 1) return;
bool[] vValid = new bool[n];
Keys kMod = Keys.None;
for(int i = 0; i < n; ++i)
{
SiEvent si = l[i];
if(si.Type == SiEventType.KeyModifier)
{
if(si.Down.HasValue)
{
if(si.Down.Value)
{
Debug.Assert((kMod & si.KeyModifier) == Keys.None);
kMod |= si.KeyModifier;
}
else
{
Debug.Assert((kMod & si.KeyModifier) == si.KeyModifier);
kMod &= ~si.KeyModifier;
}
}
else { Debug.Assert(false); }
}
else if((si.Type == SiEventType.Char) && (kMod == Keys.None))
vValid[i] = true;
}
int c = 0;
for(int i = n - 1; i >= -1; --i)
{
if((i == -1) || !vValid[i])
{
if(c > 0)
{
ReplaceByMixedTransfer(l, i + 1, c);
c = 0;
}
}
else ++c;
}
}
private static void ReplaceByMixedTransfer(List<SiEvent> l, int iOffset,
int nCount)
{
List<SiEvent> lNew = new List<SiEvent>();
StringBuilder sbClip = new StringBuilder();
// The string should be split randomly, but the same each
// time this function is called. Otherwise an attacker could
// get information by observing different splittings each
// time auto-type is performed. Therefore, compute the random
// seed based on the string to be auto-typed.
Random r = new Random(GetRandomSeed(l, iOffset, nCount));
for(int i = 0; i < nCount; ++i)
{
char ch = l[iOffset + i].Char;
SiEvent si = new SiEvent();
if(r.Next(0, 2) == 0)
{
sbClip.Append(ch);
si.Type = SiEventType.Key;
si.VKey = (int)Keys.Right;
}
else
{
si.Type = SiEventType.Char;
si.Char = ch;
}
lNew.Add(si);
}
string strClip = sbClip.ToString();
if(strClip.Length > 0)
{
SiEvent si = new SiEvent();
si.Type = SiEventType.ClipboardCopy;
si.Text = strClip;
lNew.Insert(0, si);
// Mixed transfer occurs only for text without any modifiers,
// thus we can press Ctrl+V for pasting here
si = new SiEvent();
si.Type = SiEventType.KeyModifier;
si.KeyModifier = Keys.Control;
si.Down = true;
lNew.Insert(1, si);
// Send the 'v' using a virtual key code, not as char;
// sending it as char (translated to a keypress) doesn't
// work with all keyboard layouts (e.g. Russian);
// https://sourceforge.net/p/keepass/discussion/329220/thread/938d06a7/
si = new SiEvent();
si.Type = SiEventType.Key;
si.VKey = (int)Keys.V;
lNew.Insert(2, si);
si = new SiEvent();
si.Type = SiEventType.KeyModifier;
si.KeyModifier = Keys.Control;
si.Down = false;
lNew.Insert(3, si);
for(int i = 0; i < strClip.Length; ++i)
{
si = new SiEvent();
si.Type = SiEventType.Key;
si.VKey = (int)Keys.Left;
lNew.Insert(4, si);
}
}
l.RemoveRange(iOffset, nCount);
l.InsertRange(iOffset, lNew);
}
private static int GetRandomSeed(List<SiEvent> l, int iOffset, int nCount)
{
int nSeed = 3;
unchecked
{
for(int i = 0; i < nCount; ++i)
nSeed = nSeed * 13 + l[iOffset + i].Char;
}
// Prevent overflow (see .NET 2.0 Random class constructor)
if(nSeed == int.MinValue) nSeed = 13;
return nSeed;
}
}
}
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