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path: root/loader/client/syscall.cpp
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#include "syscall.hpp"
#include <vector>
#include <fstream>

//fuck balloon head
namespace syscall {
	uint8_t *c_syscall_mgr::load_ntdll() {
		//load ntdll from disk
		char path[MAX_PATH];
		GetSystemDirectoryA(path, MAX_PATH);

		std::string ntdll_path(path);
		ntdll_path += xors("\\ntdll.dll");

		FILE* file;
		if (fopen_s(&file, ntdll_path.c_str(), "rb") != 0)
			return nullptr;

		fseek(file, 0, SEEK_END);
		size_t ntdll_size = ftell(file);
		rewind(file);

		uint8_t* ntdll = new uint8_t[ntdll_size];
		fread(ntdll, ntdll_size, 1, file);
		fclose(file);

		return ntdll;
	}

	bool c_syscall_mgr::start() {
		uint8_t* ntdll = load_ntdll();
		if (!ntdll)
			return false;

		IMAGE_DOS_HEADER*     dos_header = (IMAGE_DOS_HEADER*)(&ntdll[0]);
		IMAGE_NT_HEADERS*     nt_header = (IMAGE_NT_HEADERS*)(&ntdll[dos_header->e_lfanew]);

		if (dos_header->e_magic != IMAGE_DOS_SIGNATURE) {
			delete[] ntdll;
			return false;
		}

		if (nt_header->Signature != IMAGE_NT_SIGNATURE) {
			delete[] ntdll;
			return false;
		}

		IMAGE_SECTION_HEADER* section_header = (IMAGE_SECTION_HEADER*)(&ntdll[dos_header->e_lfanew + sizeof(IMAGE_NT_HEADERS)]);
		uintptr_t export_rva = nt_header->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress;

		uint32_t delta = 0;
		for (size_t i = 0; i < nt_header->FileHeader.NumberOfSections; i++) {
			if (export_rva > section_header[i].VirtualAddress)
				delta = section_header[i].VirtualAddress - section_header[i].PointerToRawData;
		}

		//exports
		IMAGE_EXPORT_DIRECTORY* export_directory = (IMAGE_EXPORT_DIRECTORY*)(&ntdll[export_rva - delta]);

		size_t number_of_functions = export_directory->NumberOfFunctions;
		uintptr_t names = export_directory->AddressOfNames - delta;
		uintptr_t funcs = export_directory->AddressOfFunctions - delta;
		uintptr_t ords = export_directory->AddressOfNameOrdinals - delta;

		for (size_t i = 0; i < number_of_functions; i++) {
			uint32_t name_rva = *(uint32_t*)(&ntdll[names + i * sizeof(uint32_t)]) - delta;
			char* name = (char*)(&ntdll[name_rva]);

			uint16_t ordinal = *(uint16_t*)(&ntdll[ords + i * sizeof(uint16_t)]);
			uint32_t func_rva = *(uint32_t*)(&ntdll[funcs + ordinal * sizeof(uint32_t)]);

			uint32_t func_delta = 0;
			for (size_t j = 0; j < nt_header->FileHeader.NumberOfSections; j++) {
				if (func_rva > section_header[j].VirtualAddress)
					func_delta = section_header[j].VirtualAddress - section_header[j].PointerToRawData;
			}

			func_rva -= func_delta;

			uint32_t code = *(uint32_t*)(&ntdll[func_rva + 0]);//crashes here?
			uint32_t index = *(uint32_t*)(&ntdll[func_rva + 4]);

			//syscall
			if (code == 0xB8D18B4C)
			{
				m_syscalls[hash::fnv1a(name)].set_index(index);
			}
		}

		delete[] ntdll;

		// check if we succesfully got the syscalls
		hash_t hash = fnv("ZwWriteVirtualMemory");
		if (m_syscalls.find(hash) != m_syscalls.end())
			return m_syscalls[hash].validate();

		return false;
	}
}