Decrypt V5 encrypted methods
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@ -28,12 +28,11 @@ using de4dot.blocks;
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using de4dot.code.PE;
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namespace de4dot.code.deobfuscators.CodeVeil {
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// The code isn't currently encrypted at all! But let's keep this class name.
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class MethodsDecrypter {
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ModuleDefinition module;
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TypeDefinition methodsType;
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List<int> rvas; // _stub and _executive
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TypeVersion typeVersion = TypeVersion.Unknown;
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IDecrypter decrypter;
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enum TypeVersion {
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Unknown,
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@ -42,6 +41,113 @@ namespace de4dot.code.deobfuscators.CodeVeil {
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V5,
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}
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interface IDecrypter {
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TypeVersion TypeVersion { get; }
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void initialize(byte[] methodsData);
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bool decrypt(BinaryReader fileDataReader, DumpedMethod dm);
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}
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class Decrypter : IDecrypter {
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TypeVersion typeVersion;
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BinaryReader methodsDataReader;
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public TypeVersion TypeVersion {
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get { return typeVersion; }
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}
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public Decrypter(TypeVersion typeVersion) {
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this.typeVersion = typeVersion;
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}
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public virtual void initialize(byte[] methodsData) {
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methodsDataReader = new BinaryReader(new MemoryStream(methodsData));
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}
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public virtual bool decrypt(BinaryReader fileDataReader, DumpedMethod dm) {
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if (fileDataReader.ReadByte() != 0x2A)
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return false; // Not a RET
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int methodsDataOffset = DeobUtils.readVariableLengthInt32(fileDataReader);
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methodsDataReader.BaseStream.Position = methodsDataOffset;
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dm.mhCodeSize = (uint)DeobUtils.readVariableLengthInt32(methodsDataReader);
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dm.code = methodsDataReader.ReadBytes((int)dm.mhCodeSize);
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if ((dm.mhFlags & 8) != 0)
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dm.extraSections = readExtraSections(methodsDataReader);
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if (!decryptCode(dm))
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return false;
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return true;
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}
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protected virtual bool decryptCode(DumpedMethod dm) {
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return true;
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}
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static void align(BinaryReader reader, int alignment) {
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reader.BaseStream.Position = (reader.BaseStream.Position + alignment - 1) & ~(alignment - 1);
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}
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static byte[] readExtraSections(BinaryReader reader) {
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align(reader, 4);
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int startPos = (int)reader.BaseStream.Position;
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parseSection(reader);
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int size = (int)reader.BaseStream.Position - startPos;
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reader.BaseStream.Position = startPos;
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return reader.ReadBytes(size);
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}
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static void parseSection(BinaryReader reader) {
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byte flags;
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do {
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align(reader, 4);
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flags = reader.ReadByte();
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if ((flags & 1) == 0)
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throw new ApplicationException("Not an exception section");
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if ((flags & 0x3E) != 0)
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throw new ApplicationException("Invalid bits set");
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if ((flags & 0x40) != 0) {
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reader.BaseStream.Position--;
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int num = (int)(reader.ReadUInt32() >> 8) / 24;
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reader.BaseStream.Position += num * 24;
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}
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else {
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int num = reader.ReadByte() / 12;
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reader.BaseStream.Position += 2 + num * 12;
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}
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} while ((flags & 0x80) != 0);
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}
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}
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class DecrypterV5 : Decrypter {
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byte[] decryptKey;
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public DecrypterV5()
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: base(TypeVersion.V5) {
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}
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public override void initialize(byte[] methodsData) {
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var data = DeobUtils.inflate(methodsData, true);
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decryptKey = BitConverter.GetBytes(BitConverter.ToUInt32(data, 0));
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var newMethodsData = new byte[data.Length - 4];
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Array.Copy(data, 4, newMethodsData, 0, newMethodsData.Length);
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base.initialize(newMethodsData);
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}
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protected override bool decryptCode(DumpedMethod dm) {
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var code = dm.code;
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for (int i = 0; i < code.Length; i++) {
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for (int j = 0; j < 4 && i + j < code.Length; j++)
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code[i + j] ^= decryptKey[j];
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}
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return true;
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}
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}
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public bool Detected {
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get { return methodsType != null; }
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}
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@ -105,11 +211,11 @@ namespace de4dot.code.deobfuscators.CodeVeil {
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return false;
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if (hasCodeString(initMethod, "E_FullTrust"))
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typeVersion = TypeVersion.V4;
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decrypter = new Decrypter(TypeVersion.V4);
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else if (hasCodeString(initMethod, "Full Trust Required"))
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typeVersion = TypeVersion.V3;
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decrypter = new Decrypter(TypeVersion.V3);
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else if (initMethod.DeclaringType.HasNestedTypes && new FieldTypes(initMethod.DeclaringType).all(fieldTypesV5))
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typeVersion = TypeVersion.V5;
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decrypter = new DecrypterV5();
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else
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return false;
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@ -160,10 +266,7 @@ namespace de4dot.code.deobfuscators.CodeVeil {
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if (methodsData == null)
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return false;
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if (typeVersion == TypeVersion.V5) {
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methodsData = DeobUtils.inflate(methodsData, true);
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throw new NotImplementedException(); //TODO:
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}
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decrypter.initialize(methodsData);
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dumpedMethods = createDumpedMethods(peImage, fileData, methodsData);
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if (dumpedMethods == null)
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@ -216,15 +319,9 @@ namespace de4dot.code.deobfuscators.CodeVeil {
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codeOffset = bodyOffset + (uint)(dm.mhFlags >> 12) * 4;
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}
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fileDataReader.BaseStream.Position = codeOffset;
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if (fileDataReader.ReadByte() != 0x2A)
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continue; // Not a RET
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int methodsDataOffset = DeobUtils.readVariableLengthInt32(fileDataReader);
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methodsDataReader.BaseStream.Position = methodsDataOffset;
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dm.mhCodeSize = (uint)DeobUtils.readVariableLengthInt32(methodsDataReader);
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dm.code = methodsDataReader.ReadBytes((int)dm.mhCodeSize);
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if ((dm.mhFlags & 8) != 0)
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dm.extraSections = readExtraSections(methodsDataReader);
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if (!decrypter.decrypt(fileDataReader, dm))
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continue;
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dumpedMethods[dm.token] = dm;
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}
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@ -232,42 +329,6 @@ namespace de4dot.code.deobfuscators.CodeVeil {
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return dumpedMethods;
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}
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static void align(BinaryReader reader, int alignment) {
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reader.BaseStream.Position = (reader.BaseStream.Position + alignment - 1) & ~(alignment - 1);
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}
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static byte[] readExtraSections(BinaryReader reader) {
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align(reader, 4);
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int startPos = (int)reader.BaseStream.Position;
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parseSection(reader);
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int size = (int)reader.BaseStream.Position - startPos;
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reader.BaseStream.Position = startPos;
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return reader.ReadBytes(size);
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}
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static void parseSection(BinaryReader reader) {
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byte flags;
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do {
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align(reader, 4);
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flags = reader.ReadByte();
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if ((flags & 1) == 0)
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throw new ApplicationException("Not an exception section");
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if ((flags & 0x3E) != 0)
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throw new ApplicationException("Invalid bits set");
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if ((flags & 0x40) != 0) {
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reader.BaseStream.Position--;
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int num = (int)(reader.ReadUInt32() >> 8) / 24;
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reader.BaseStream.Position += num * 24;
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}
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else {
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int num = reader.ReadByte() / 12;
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reader.BaseStream.Position += 2 + num * 12;
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}
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} while ((flags & 0x80) != 0);
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}
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// xor eax, eax / inc eax / pop esi edi edx ecx ebx / leave / ret 0Ch or 10h
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static byte[] initializeMethodEnd = new byte[] {
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0x33, 0xC0, 0x40, 0x5E, 0x5F, 0x5A, 0x59, 0x5B, 0xC9, 0xC2,
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