282 lines
8.4 KiB
C#
282 lines
8.4 KiB
C#
/*
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Copyright (C) 2011-2012 de4dot@gmail.com
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This file is part of de4dot.
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de4dot 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 3 of the License, or
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(at your option) any later version.
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de4dot 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 de4dot. If not, see <http://www.gnu.org/licenses/>.
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*/
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using System;
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using System.IO;
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using Mono.Cecil;
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using Mono.Cecil.Cil;
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using Mono.MyStuff;
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using de4dot.blocks;
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using de4dot.PE;
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namespace de4dot.code.deobfuscators.Confuser {
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class MemoryMethodsDecrypter : MethodsDecrypterBase {
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ConfuserVersion version = ConfuserVersion.Unknown;
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enum ConfuserVersion {
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Unknown,
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v14_r57884,
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v14_r58004,
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vXX,
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}
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public MemoryMethodsDecrypter(ModuleDefinition module, ISimpleDeobfuscator simpleDeobfuscator)
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: base(module, simpleDeobfuscator) {
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}
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public MemoryMethodsDecrypter(ModuleDefinition module, MemoryMethodsDecrypter other)
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: base(module, other) {
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}
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protected override bool checkType(TypeDefinition type, MethodDefinition initMethod) {
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if (type == null)
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return false;
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if (type.Methods.Count != 3)
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return false;
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if (DotNetUtils.getPInvokeMethod(type, "kernel32", "VirtualProtect") == null)
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return false;
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if (!DotNetUtils.hasString(initMethod, "Broken file"))
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return false;
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if ((decryptMethod = findDecryptMethod(type)) == null)
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return false;
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if (!DotNetUtils.hasString(initMethod, "Module error"))
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version = ConfuserVersion.v14_r57884;
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else if (DotNetUtils.callsMethod(initMethod, "System.Void System.IO.FileStream::.ctor(System.String,System.IO.FileMode,System.IO.FileAccess,System.IO.FileShare)"))
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version = ConfuserVersion.v14_r58004;
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else
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version = ConfuserVersion.vXX;
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return true;
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}
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public void initialize() {
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if (initMethod == null)
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return;
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switch (version) {
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case ConfuserVersion.v14_r57884:
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case ConfuserVersion.v14_r58004:
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break;
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case ConfuserVersion.vXX:
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if (!initializeKeys_vXX())
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throw new ApplicationException("Could not find all decryption keys");
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break;
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default:
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throw new ApplicationException("Unknown version");
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}
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}
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bool initializeKeys_vXX() {
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simpleDeobfuscator.deobfuscate(initMethod);
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if (!findLKey0(initMethod, out lkey0))
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return false;
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if (!findKey0(initMethod, out key0))
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return false;
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if (!findKey1(initMethod, out key1))
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return false;
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if (!findKey2Key3(initMethod, out key2, out key3))
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return false;
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if (!findKey4(initMethod, out key4))
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return false;
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if (!findKey5(initMethod, out key5))
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return false;
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simpleDeobfuscator.deobfuscate(decryptMethod);
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if (!findKey6(decryptMethod, out key6))
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return false;
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return true;
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}
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static bool findKey4(MethodDefinition method, out uint key) {
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var instrs = method.Body.Instructions;
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for (int i = 0; i < instrs.Count; i++) {
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i = findCallvirtReadUInt32(instrs, i);
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if (i < 0)
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break;
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if (i >= 2) {
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if (instrs[i-2].OpCode.Code == Code.Pop)
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continue;
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}
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if (i + 4 >= instrs.Count)
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break;
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var ldci4 = instrs[i + 1];
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if (!DotNetUtils.isLdcI4(ldci4))
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continue;
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if (instrs[i + 2].OpCode.Code != Code.Xor)
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continue;
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var stloc = instrs[i + 3];
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if (!DotNetUtils.isStloc(stloc))
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continue;
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var ldloc = instrs[i + 4];
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if (!DotNetUtils.isLdloc(ldloc))
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continue;
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if (DotNetUtils.getLocalVar(method.Body.Variables, ldloc) != DotNetUtils.getLocalVar(method.Body.Variables, stloc))
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continue;
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key = (uint)DotNetUtils.getLdcI4Value(ldci4);
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return true;
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}
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key = 0;
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return false;
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}
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static bool findKey5(MethodDefinition method, out uint key) {
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var instrs = method.Body.Instructions;
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for (int i = 0; i < instrs.Count; i++) {
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i = findCallvirtReadUInt32(instrs, i);
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if (i < 0)
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break;
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int index2 = ConfuserUtils.findCallMethod(instrs, i, Code.Callvirt, "System.Int32 System.IO.BinaryReader::ReadInt32()");
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if (index2 < 0)
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break;
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if (index2 - i != 6)
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continue;
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var ldci4 = instrs[i + 1];
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if (!DotNetUtils.isLdcI4(ldci4))
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continue;
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if (instrs[i + 2].OpCode.Code != Code.Xor)
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continue;
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var stloc = instrs[i + 3];
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if (!DotNetUtils.isStloc(stloc))
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continue;
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var ldloc = instrs[i + 4];
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if (!DotNetUtils.isLdloc(ldloc))
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continue;
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if (DotNetUtils.getLocalVar(method.Body.Variables, ldloc) == DotNetUtils.getLocalVar(method.Body.Variables, stloc))
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continue;
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if (!DotNetUtils.isLdloc(instrs[i + 5]))
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continue;
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key = (uint)DotNetUtils.getLdcI4Value(ldci4);
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return true;
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}
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key = 0;
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return false;
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}
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public bool decrypt(PeImage peImage, byte[] fileData, ref DumpedMethods dumpedMethods) {
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if (initMethod == null)
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return false;
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switch (version) {
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case ConfuserVersion.v14_r57884: return decrypt_v14_r57884(peImage, fileData, ref dumpedMethods);
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case ConfuserVersion.v14_r58004: return decrypt_v14_r58004(peImage, fileData, ref dumpedMethods);
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case ConfuserVersion.vXX: return decrypt_vXX(peImage, fileData, ref dumpedMethods);
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default: throw new ApplicationException("Unknown version");
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}
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}
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bool decrypt_v14_r57884(PeImage peImage, byte[] fileData, ref DumpedMethods dumpedMethods) {
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methodsData = decryptMethodsData_v14_r57884(peImage);
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var reader = new BinaryReader(new MemoryStream(methodsData));
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reader.ReadInt16(); // sig
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var writer = new BinaryWriter(new MemoryStream(fileData));
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int numInfos = reader.ReadInt32();
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for (int i = 0; i < numInfos; i++) {
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uint rva = reader.ReadUInt32();
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if (rva == 0)
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continue;
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writer.BaseStream.Position = peImage.rvaToOffset(rva);
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writer.Write(reader.ReadBytes(reader.ReadInt32()));
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}
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return true;
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}
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byte[] decryptMethodsData_v14_r57884(PeImage peImage) {
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var reader = peImage.Reader;
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reader.BaseStream.Position = 0;
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var md5SumData = reader.ReadBytes((int)peImage.OptionalHeader.checkSum);
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int csOffs = (int)peImage.OptionalHeader.Offset + 0x40;
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md5SumData[csOffs] = 0;
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md5SumData[csOffs + 1] = 0;
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md5SumData[csOffs + 2] = 0;
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md5SumData[csOffs + 3] = 0;
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var md5Sum = DeobUtils.md5Sum(md5SumData);
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ulong checkSum = reader.ReadUInt64();
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if (checkSum != calcChecksum(md5SumData))
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throw new ApplicationException("Invalid checksum. File has been modified.");
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var iv = reader.ReadBytes(reader.ReadInt32());
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var encrypted = reader.ReadBytes(reader.ReadInt32());
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var decrypted = decrypt(encrypted, iv, md5SumData);
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if (BitConverter.ToInt16(decrypted, 0) != 0x6FD6)
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throw new ApplicationException("Invalid magic");
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return decrypted;
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}
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bool decrypt_v14_r58004(PeImage peImage, byte[] fileData, ref DumpedMethods dumpedMethods) {
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methodsData = decryptMethodsData_v14_r57884(peImage);
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var reader = new BinaryReader(new MemoryStream(methodsData));
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reader.ReadInt16(); // sig
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var writer = new BinaryWriter(new MemoryStream(fileData));
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int numInfos = reader.ReadInt32();
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for (int i = 0; i < numInfos; i++) {
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uint offs = reader.ReadUInt32();
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if (offs == 0)
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continue;
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uint rva = reader.ReadUInt32();
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if (peImage.rvaToOffset(rva) != offs)
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throw new ApplicationException("Invalid offs & rva");
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writer.BaseStream.Position = peImage.rvaToOffset(rva);
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writer.Write(reader.ReadBytes(reader.ReadInt32()));
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}
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return true;
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}
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bool decrypt_vXX(PeImage peImage, byte[] fileData, ref DumpedMethods dumpedMethods) {
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if (peImage.OptionalHeader.checkSum == 0)
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return false;
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methodsData = decryptMethodsData(peImage);
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return decrypt_vXX(peImage, fileData);
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}
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bool decrypt_vXX(PeImage peImage, byte[] fileData) {
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var reader = new BinaryReader(new MemoryStream(methodsData));
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reader.ReadInt16(); // sig
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int numInfos = reader.ReadInt32();
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for (int i = 0; i < numInfos; i++) {
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uint offs = reader.ReadUInt32() ^ key4;
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if (offs == 0)
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continue;
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uint rva = reader.ReadUInt32() ^ key5;
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if (peImage.rvaToOffset(rva) != offs)
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throw new ApplicationException("Invalid offs & rva");
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int len = reader.ReadInt32();
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for (int j = 0; j < len; j++)
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fileData[offs + j] = reader.ReadByte();
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}
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return true;
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}
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}
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}
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