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#include "HookSystem.hpp"
#define register
#include <udis86.h>
#undef register
#include <sys/mman.h>
#include <unistd.h>
#include <cstring>
CFunctionHook::CFunctionHook(HANDLE owner, void* source, void* destination) {
m_pSource = source;
m_pDestination = destination;
m_pOwner = owner;
}
CFunctionHook::~CFunctionHook() {
if (m_bActive) {
unhook();
}
}
size_t getInstructionLenAt(void* start) {
ud_t udis;
ud_init(&udis);
ud_set_mode(&udis, 64);
ud_set_syntax(&udis, UD_SYN_INTEL);
size_t curOffset = 1;
size_t insSize = 0;
while (true) {
ud_set_input_buffer(&udis, (uint8_t*)start, curOffset);
insSize = ud_disassemble(&udis);
if (insSize != curOffset)
break;
curOffset++;
}
return insSize;
}
size_t probeMinimumJumpSize(void* start, size_t min) {
size_t size = 0;
while (size <= min) {
// find info about this instruction
size_t insLen = getInstructionLenAt(start + size);
size += insLen;
}
return size;
}
bool CFunctionHook::hook() {
// check for unsupported platforms
#if !defined(__x86_64__)
return false;
#endif
// movabs $0,%rax | jmpq *%rax
static constexpr uint8_t ABSOLUTE_JMP_ADDRESS[] = {0x48, 0xB8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xE0};
// pushq %rax
static constexpr uint8_t PUSH_RAX[] = {0x50};
// popq %rax
static constexpr uint8_t POP_RAX[] = {0x58};
// nop
static constexpr uint8_t NOP = 0x90;
// get minimum size to overwrite
const auto HOOKSIZE = probeMinimumJumpSize(m_pSource, sizeof(ABSOLUTE_JMP_ADDRESS) + sizeof(PUSH_RAX) + sizeof(POP_RAX));
// alloc trampoline
m_pTrampolineAddr = mmap(NULL, sizeof(ABSOLUTE_JMP_ADDRESS) + HOOKSIZE + sizeof(PUSH_RAX), PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
// populate trampoline
memcpy(m_pTrampolineAddr, m_pSource, HOOKSIZE); // first, original func bytes
memcpy(m_pTrampolineAddr + HOOKSIZE, PUSH_RAX, sizeof(PUSH_RAX)); // then, pushq %rax
memcpy(m_pTrampolineAddr + HOOKSIZE + sizeof(PUSH_RAX), ABSOLUTE_JMP_ADDRESS, sizeof(ABSOLUTE_JMP_ADDRESS)); // then, jump to source
// fixup trampoline addr
*(uint64_t*)(m_pTrampolineAddr + HOOKSIZE + 2 + sizeof(PUSH_RAX)) = (uint64_t)(m_pSource + sizeof(ABSOLUTE_JMP_ADDRESS));
// make jump to hk
mprotect(m_pSource - ((uint64_t)m_pSource) % sysconf(_SC_PAGE_SIZE), sysconf(_SC_PAGE_SIZE), PROT_READ | PROT_WRITE | PROT_EXEC);
memcpy(m_pSource, ABSOLUTE_JMP_ADDRESS, sizeof(ABSOLUTE_JMP_ADDRESS));
// make popq %rax and NOP all remaining
memcpy(m_pSource + sizeof(ABSOLUTE_JMP_ADDRESS), POP_RAX, sizeof(POP_RAX));
size_t currentOp = sizeof(ABSOLUTE_JMP_ADDRESS) + sizeof(POP_RAX);
memset(m_pSource + currentOp, NOP, HOOKSIZE - currentOp);
// fixup jump addr
*(uint64_t*)(m_pSource + 2) = (uint64_t)(m_pDestination);
// revert mprot
mprotect(m_pSource - ((uint64_t)m_pSource) % sysconf(_SC_PAGE_SIZE), sysconf(_SC_PAGE_SIZE), PROT_READ | PROT_EXEC);
// set original addr to trampo addr
m_pOriginal = m_pTrampolineAddr;
m_bActive = true;
m_iHookLen = HOOKSIZE;
m_iTrampoLen = HOOKSIZE + sizeof(ABSOLUTE_JMP_ADDRESS);
return true;
}
bool CFunctionHook::unhook() {
// check for unsupported platforms
#if !defined(__x86_64__)
return false;
#endif
if (!m_bActive)
return false;
// allow write to src
mprotect(m_pSource - ((uint64_t)m_pSource) % sysconf(_SC_PAGE_SIZE), sysconf(_SC_PAGE_SIZE), PROT_READ | PROT_WRITE | PROT_EXEC);
// write back original bytes
memcpy(m_pSource, m_pTrampolineAddr, m_iHookLen);
// revert mprot
mprotect(m_pSource - ((uint64_t)m_pSource) % sysconf(_SC_PAGE_SIZE), sysconf(_SC_PAGE_SIZE), PROT_READ | PROT_EXEC);
// unmap
munmap(m_pTrampolineAddr, m_iTrampoLen);
// reset vars
m_bActive = false;
m_iHookLen = 0;
m_iTrampoLen = 0;
m_pTrampolineAddr = nullptr;
return true;
}
CFunctionHook* CHookSystem::initHook(HANDLE owner, void* source, void* destination) {
return m_vHooks.emplace_back(std::make_unique<CFunctionHook>(owner, source, destination)).get();
}
bool CHookSystem::removeHook(CFunctionHook* hook) {
std::erase_if(m_vHooks, [&](const auto& other) { return other.get() == hook; });
return true; // todo: make false if not found
}
void CHookSystem::removeAllHooksFrom(HANDLE handle) {
std::erase_if(m_vHooks, [&](const auto& other) { return other->m_pOwner == handle; });
}
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