125 lines
3.2 KiB
C#
125 lines
3.2 KiB
C#
/*
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Copyright (C) 2011 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.Text;
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using Mono.Cecil;
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using de4dot.blocks;
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namespace de4dot.deobfuscators.CryptoObfuscator {
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class StringDecrypter {
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ModuleDefinition module;
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EmbeddedResource stringResource;
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TypeDefinition stringDecrypterType;
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MethodDefinition stringDecrypterMethod;
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byte[] decryptedData;
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public bool Detected {
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get { return stringDecrypterType != null; }
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}
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public MethodDefinition StringDecrypterMethod {
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get { return stringDecrypterMethod; }
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}
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public EmbeddedResource StringResource {
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get { return stringResource; }
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}
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public StringDecrypter(ModuleDefinition module) {
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this.module = module;
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}
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public void find() {
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TypeDefinition type;
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MethodDefinition method;
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if (!findStringDecrypterType(out type, out method))
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return;
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stringDecrypterType = type;
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stringDecrypterMethod = method;
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}
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public void init(ResourceDecrypter resourceDecrypter) {
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if (decryptedData != null)
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return;
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var resourceName = module.Assembly.Name.Name + module.Assembly.Name.Name;
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stringResource = DotNetUtils.getResource(module, resourceName) as EmbeddedResource;
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if (stringResource == null)
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return;
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decryptedData = resourceDecrypter.decrypt(stringResource.GetResourceStream());
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}
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public string decrypt(int index) {
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int len;
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byte b = decryptedData[index++];
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if ((b & 0x80) == 0)
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len = b;
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else if ((b & 0x40) == 0)
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len = ((b & 0x3F) << 8) + decryptedData[index++];
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else {
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len = ((b & 0x3F) << 24) +
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((int)decryptedData[index++] << 16) +
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((int)decryptedData[index++] << 8) +
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decryptedData[index++];
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}
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return Encoding.Unicode.GetString(decryptedData, index, len);
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}
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bool findStringDecrypterType(out TypeDefinition theType, out MethodDefinition theMethod) {
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theType = null;
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theMethod = null;
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foreach (var type in module.Types) {
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if (type.IsPublic)
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continue;
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if (type.Fields.Count != 1)
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continue;
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if (DotNetUtils.findFieldType(type, "System.Byte[]", true) == null)
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continue;
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if (type.Methods.Count != 3)
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continue;
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if (type.HasEvents || type.HasProperties)
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continue;
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MethodDefinition method = null;
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foreach (var m in type.Methods) {
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if (m.Name == ".ctor" || m.Name == ".cctor")
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continue;
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if (DotNetUtils.isMethod(m, "System.String", "(System.Int32)")) {
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method = m;
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continue;
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}
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break;
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}
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if (method == null)
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continue;
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theType = type;
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theMethod = method;
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return true;
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}
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return false;
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}
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}
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}
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