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@ -4,261 +4,12 @@ namespace vm::locate
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{
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std::vector< vm_handler_table_info_t > all_handler_tables( std::uintptr_t module_base )
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{
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std::vector< vm_handler_table_info_t > result;
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auto module_info = reinterpret_cast< win::image_t<> * >( module_base );
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auto sections = module_info->get_nt_headers()->get_sections();
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auto num_sections = module_info->get_file_header()->num_sections;
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auto umtils = xtils::um_t::get_instance();
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static const auto lea_r12_validate = []( std::uintptr_t addr ) -> bool {
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ZydisDecodedInstruction instr;
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ZydisDecoder decoder;
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ZydisRegister jmp_reg = ZYDIS_REGISTER_NONE;
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ZydisDecoderInit( &decoder, ZYDIS_MACHINE_MODE_LONG_64, ZYDIS_ADDRESS_WIDTH_64 );
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unsigned instr_count = 0u;
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bool found_table_idx = false, found_valid_jmp = false;
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while ( ZYAN_SUCCESS(
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ZydisDecoderDecodeBuffer( &decoder, reinterpret_cast< void * >( addr ), 0x1000, &instr ) ) )
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{
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++instr_count;
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if ( instr_count >= 0x1000 ||
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instr.mnemonic == ZYDIS_MNEMONIC_INVALID ) // prevent run offs and misalignment...
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break;
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// determine if we are looking at a JMP RCX/JMP RDX...
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if ( vm::util::is_jmp( instr ) )
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{
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if ( instr.operands[ 0 ].type == ZYDIS_OPERAND_TYPE_REGISTER &&
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( instr.operands[ 0 ].reg.value == ZYDIS_REGISTER_RDX ||
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instr.operands[ 0 ].reg.value == ZYDIS_REGISTER_RCX ) )
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{
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if ( jmp_reg == ZYDIS_REGISTER_NONE || jmp_reg != instr.operands[ 0 ].reg.value )
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break;
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// else we set it to true and break...
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found_valid_jmp = true;
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break;
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}
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// take JCC branch no matter what...
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ZydisCalcAbsoluteAddress( &instr, &instr.operands[ 0 ], addr, &addr );
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// dont execute anymore address advancement code...
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continue;
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}
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// else if the instruction is a MOV RDX/RCX, [R12+RAX*0x8]... we know this is an index into
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// the vm handler table and thus this lea r12, xxxx is probably legit...
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else if ( instr.mnemonic == ZYDIS_MNEMONIC_MOV &&
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instr.operands[ 0 ].type == ZYDIS_OPERAND_TYPE_REGISTER &&
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( instr.operands[ 0 ].reg.value == ZYDIS_REGISTER_RDX ||
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instr.operands[ 0 ].reg.value == ZYDIS_REGISTER_RCX ) &&
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instr.operands[ 1 ].type == ZYDIS_OPERAND_TYPE_MEMORY &&
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instr.operands[ 1 ].mem.base == ZYDIS_REGISTER_R12 &&
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instr.operands[ 1 ].mem.index == ZYDIS_REGISTER_RAX && instr.operands[ 1 ].mem.scale == 0x8 )
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{
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found_table_idx = true;
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jmp_reg = instr.operands[ 0 ].reg.value;
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}
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else if ( instr.mnemonic == ZYDIS_MNEMONIC_RET || instr.mnemonic == ZYDIS_MNEMONIC_CALL )
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break;
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// advance the instruction address "addr"...
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addr += instr.length;
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}
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return found_table_idx && found_valid_jmp;
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};
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ZydisDecodedInstruction instr;
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ZydisDecoder decoder;
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ZydisDecoderInit( &decoder, ZYDIS_MACHINE_MODE_LONG_64, ZYDIS_ADDRESS_WIDTH_64 );
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for ( auto idx = 0u; idx < num_sections; ++idx )
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{
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// if the section is executable and not discardable... scan it for lea r12, xxxx and ensure its loading
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// a virtual machine handler table into r12...
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if ( sections[ idx ].characteristics.mem_execute && !sections[ idx ].characteristics.mem_discardable )
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{
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void *scan_result = reinterpret_cast< void * >( sections[ idx ].virtual_address + module_base );
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do
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{
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// compute how far away from the beginning of the section we are...
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auto section_size = reinterpret_cast< std::uintptr_t >( scan_result ) -
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( sections[ idx ].virtual_address + module_base );
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// scan from the last scans result to the end of the section for lea r12's...
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scan_result = umtils->sigscan( scan_result, sections[ idx ].virtual_size - section_size,
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LEA_R12_SIG, LEA_R12_MASK );
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if ( scan_result )
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{
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// check to see if we are looking at:
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// 1.) a legit "lea r12, xxxx" and not a misaligned instruction...
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// 2.) if the instruction stream is followed in zydis it ends with a jmp rcx/jmp rdx...
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if ( lea_r12_validate( reinterpret_cast< std::uintptr_t >( scan_result ) ) )
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{
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if ( ZYAN_SUCCESS( ZydisDecoderDecodeBuffer(
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&decoder, scan_result, sections[ idx ].virtual_size - section_size, &instr ) ) )
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{
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vm_handler_table_info_t vm_handler_table_info;
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vm_handler_table_info.rva =
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( instr.operands[ 1 ].mem.disp.value +
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reinterpret_cast< std::uintptr_t >( scan_result ) + instr.length ) -
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module_base;
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vm_handler_table_info.lea_r12_rva =
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reinterpret_cast< std::uintptr_t >( scan_result ) - module_base;
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vm_handler_table_info.lea_r12_instr = instr;
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result.push_back( vm_handler_table_info );
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}
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}
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scan_result = reinterpret_cast< void * >( reinterpret_cast< std::uintptr_t >( scan_result ) +
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sizeof LEA_R12_SIG );
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}
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} while ( scan_result );
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}
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}
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return result;
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return {};
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}
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std::vector< std::pair< std::uint32_t, std::uint32_t > > all_vm_enters(
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std::uintptr_t module_base, std::vector< vm_handler_table_info_t > &vm_handler_tables )
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{
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std::vector< std::pair< std::uint32_t, std::uint32_t > > result;
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auto module_info = reinterpret_cast< win::image_t<> * >( module_base );
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auto sections = module_info->get_nt_headers()->get_sections();
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auto num_sections = module_info->get_file_header()->num_sections;
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auto umtils = xtils::um_t::get_instance();
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auto module_end = module_base + module_info->get_nt_headers()->optional_header.size_image;
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static const auto validate_vm_enter = [ & ]( std::uintptr_t addr ) -> bool {
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ZydisDecodedInstruction instr;
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ZydisDecoder decoder;
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ZydisDecoderInit( &decoder, ZYDIS_MACHINE_MODE_LONG_64, ZYDIS_ADDRESS_WIDTH_64 );
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unsigned instr_count = 0u;
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bool found_valid_jmp = false;
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std::vector< ZydisDecodedInstruction > instr_stream;
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while ( addr >= module_base && addr < module_end &&
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ZYAN_SUCCESS(
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ZydisDecoderDecodeBuffer( &decoder, reinterpret_cast< void * >( addr ), 0x1000, &instr ) ) )
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{
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if ( !instr_count && instr.mnemonic != ZYDIS_MNEMONIC_PUSH )
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break;
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++instr_count; // handle run offs and misaligned instructions...
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if ( instr_count > 500 || instr.mnemonic == ZYDIS_MNEMONIC_INVALID ||
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instr.mnemonic == ZYDIS_MNEMONIC_RET || instr.mnemonic == ZYDIS_MNEMONIC_CALL )
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return false;
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// determine if we are looking at a JMP RCX/JMP RDX...
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if ( vm::util::is_jmp( instr ) )
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{
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if ( instr.operands[ 0 ].type == ZYDIS_OPERAND_TYPE_REGISTER &&
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( instr.operands[ 0 ].reg.value == ZYDIS_REGISTER_RDX ||
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instr.operands[ 0 ].reg.value == ZYDIS_REGISTER_RCX ) )
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{
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// else we set it to true and break...
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found_valid_jmp = true;
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instr_stream.push_back( instr );
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break;
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}
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// take JCC branch no matter what...
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ZydisCalcAbsoluteAddress( &instr, &instr.operands[ 0 ], addr, &addr );
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// dont execute anymore address advancement code...
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continue;
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}
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instr_stream.push_back( instr );
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addr += instr.length;
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}
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if ( !found_valid_jmp )
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return false;
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// second instruction in the flattened stream should be a push...
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// this is also an optimization so we dont have to hit that 0^2 std::find_if every time...
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if ( instr_stream[ 1 ].mnemonic != ZYDIS_MNEMONIC_PUSH )
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return false;
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if ( std::find_if( instr_stream.begin() + 1, instr_stream.end(),
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[ & ]( const ZydisDecodedInstruction &instr ) {
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return instr.mnemonic == ZYDIS_MNEMONIC_PUSH &&
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instr.operands[ 0 ].type == ZYDIS_OPERAND_TYPE_IMMEDIATE;
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} ) == instr_stream.end() )
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return false;
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// scan over the instruction stream to see if it contains an lea r12, xxxx which is a known vm handler table
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// load into r12... this is O^2 and very slow... whatever...
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return std::find_if(
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instr_stream.begin(), instr_stream.end(), [ & ]( const ZydisDecodedInstruction &instr ) {
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return instr.mnemonic == ZYDIS_MNEMONIC_LEA &&
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instr.operands[ 1 ].type == ZYDIS_OPERAND_TYPE_MEMORY &&
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std::find_if( vm_handler_tables.begin(), vm_handler_tables.end(),
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[ & ]( const vm_handler_table_info_t &table_info ) {
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return table_info.lea_r12_instr.operands[ 1 ].mem.disp.value ==
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instr.operands[ 1 ].mem.disp.value;
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} ) != vm_handler_tables.end();
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} ) != instr_stream.end();
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};
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ZydisDecodedInstruction instr;
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ZydisDecoder decoder;
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ZydisDecoderInit( &decoder, ZYDIS_MACHINE_MODE_LONG_64, ZYDIS_ADDRESS_WIDTH_64 );
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// for each section...
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for ( auto idx = 0u; idx < num_sections; ++idx )
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{
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// we are only interested in executable (non-discardable) sections...
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if ( sections[ idx ].characteristics.mem_execute && !sections[ idx ].characteristics.mem_discardable )
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{
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void *scan_result = reinterpret_cast< void * >( sections[ idx ].virtual_address + module_base );
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do
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{
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// compute how far away from the beginning of the section we are...
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auto section_size = reinterpret_cast< std::uintptr_t >( scan_result ) -
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( sections[ idx ].virtual_address + module_base );
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if ( section_size > sections[ idx ].virtual_size )
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break;
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scan_result = umtils->sigscan( scan_result, sections[ idx ].virtual_size - section_size,
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PUSH_4B_IMM, PUSH_4B_MASK );
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if ( scan_result )
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{
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if ( validate_vm_enter( reinterpret_cast< std::uintptr_t >( scan_result ) ) &&
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ZYAN_SUCCESS( ZydisDecoderDecodeBuffer( &decoder, scan_result, 0x1000, &instr ) ) )
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{
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if ( std::find_if( result.begin(), result.end(),
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[ & ]( const std::pair< std::uint32_t, std::uint32_t > &info ) {
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return info.second == instr.operands[ 0 ].imm.value.u;
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} ) == result.end() )
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{
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result.push_back( { reinterpret_cast< std::uintptr_t >( scan_result ) - module_base,
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instr.operands[ 0 ].imm.value.u } );
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}
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}
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scan_result = reinterpret_cast< void * >( reinterpret_cast< std::uintptr_t >( scan_result ) +
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sizeof PUSH_4B_IMM );
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}
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} while ( scan_result );
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}
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}
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return result;
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return {};
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}
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} // namespace vm::locate
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_xeroxz
3 years ago