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250 lines
8.3 KiB
250 lines
8.3 KiB
#include <vmemu_t.hpp>
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namespace vm {
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emu_t::emu_t(vm::vmctx_t* vm_ctx,
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std::map<std::uint32_t, vm::instrs::profiler_t*>* known_hndlrs)
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: m_vm(vm_ctx),
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vip(vm_ctx->get_vip()),
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vsp(vm_ctx->get_vsp()),
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cc_trace(nullptr),
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m_known_hndlrs(known_hndlrs) {}
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emu_t::~emu_t() {
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if (uc)
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uc_close(uc);
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}
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bool emu_t::init() {
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uc_err err;
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if ((err = uc_open(UC_ARCH_X86, UC_MODE_64, &uc))) {
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std::printf("> uc_open err = %d\n", err);
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return false;
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}
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if ((err = uc_mem_map(uc, STACK_BASE, STACK_SIZE, UC_PROT_ALL))) {
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std::printf("> uc_mem_map stack err, reason = %d\n", err);
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return false;
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}
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if ((err = uc_mem_map(uc, m_vm->m_module_base, m_vm->m_image_size,
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UC_PROT_ALL))) {
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std::printf("> map memory failed, reason = %d\n", err);
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return false;
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}
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if ((err = uc_mem_write(uc, m_vm->m_module_base,
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reinterpret_cast<void*>(m_vm->m_module_base),
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m_vm->m_image_size))) {
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std::printf("> failed to write memory... reason = %d\n", err);
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return false;
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}
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if ((err = uc_hook_add(uc, &code_exec_hook, UC_HOOK_CODE,
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(void*)&vm::emu_t::code_exec_callback, this,
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m_vm->m_module_base,
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m_vm->m_module_base + m_vm->m_image_size))) {
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std::printf("> uc_hook_add error, reason = %d\n", err);
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return false;
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}
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if ((err = uc_hook_add(uc, &int_hook, UC_HOOK_INTR,
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(void*)&vm::emu_t::int_callback, this, 0ull, 0ull))) {
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std::printf("> uc_hook_add error, reason = %d\n", err);
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return false;
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}
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if ((err =
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uc_hook_add(uc, &invalid_mem_hook,
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UC_HOOK_MEM_READ_UNMAPPED | UC_HOOK_MEM_WRITE_UNMAPPED |
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UC_HOOK_MEM_FETCH_UNMAPPED,
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(void*)&vm::emu_t::invalid_mem, this, true, false))) {
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std::printf("> uc_hook_add error, reason = %d\n", err);
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return false;
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}
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return true;
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}
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void emu_t::emulate() {
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uc_err err;
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std::uintptr_t rip = m_vm->m_vm_entry_rva + m_vm->m_module_base,
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rsp = STACK_BASE + STACK_SIZE - PAGE_4KB;
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if ((err = uc_reg_write(uc, UC_X86_REG_RSP, &rsp))) {
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std::printf("> uc_reg_write error, reason = %d\n", err);
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return;
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}
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if ((err = uc_reg_write(uc, UC_X86_REG_RIP, &rip))) {
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std::printf("> uc_reg_write error, reason = %d\n", err);
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return;
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}
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cc_trace = std::make_unique<vm::instrs::hndlr_trace_t>();
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cc_trace->m_vip = vip;
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cc_trace->m_vsp = vsp;
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std::printf("> beginning execution at = %p\n", rip);
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if ((err = uc_emu_start(uc, rip, 0ull, 0ull, 0ull))) {
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std::printf("> error starting emu... reason = %d\n", err);
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return;
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}
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}
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void emu_t::int_callback(uc_engine* uc, std::uint32_t intno, emu_t* obj) {
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uc_err err;
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std::uintptr_t rip = 0ull;
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static thread_local zydis_decoded_instr_t instr;
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if ((err = uc_reg_read(uc, UC_X86_REG_RIP, &rip))) {
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std::printf("> failed to read rip... reason = %d\n", err);
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return;
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}
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if (!ZYAN_SUCCESS(ZydisDecoderDecodeBuffer(vm::utils::g_decoder.get(),
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reinterpret_cast<void*>(rip),
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PAGE_4KB, &instr))) {
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std::printf("> failed to decode instruction at = 0x%p\n", rip);
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if ((err = uc_emu_stop(uc))) {
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std::printf("> failed to stop emulation, exiting... reason = %d\n", err);
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exit(0);
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}
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return;
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}
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// advance rip over the instruction that caused the exception... this is
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// usually a division by 0...
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rip += instr.length;
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if ((err = uc_reg_write(uc, UC_X86_REG_RIP, &rip))) {
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std::printf("> failed to write rip... reason = %d\n", err);
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return;
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}
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}
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bool emu_t::code_exec_callback(uc_engine* uc,
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uint64_t address,
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uint32_t size,
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emu_t* obj) {
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uc_err err;
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static thread_local zydis_decoded_instr_t instr;
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if (!ZYAN_SUCCESS(ZydisDecoderDecodeBuffer(vm::utils::g_decoder.get(),
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reinterpret_cast<void*>(address),
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PAGE_4KB, &instr))) {
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std::printf("> failed to decode instruction at = 0x%p\n", address);
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if ((err = uc_emu_stop(uc))) {
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std::printf("> failed to stop emulation, exiting... reason = %d\n", err);
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exit(0);
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}
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return false;
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}
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if (instr.mnemonic == ZYDIS_MNEMONIC_INVALID)
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return false;
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// save the current cpu's context (all register values and such)...
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// create a new emu_instr_t with this information... this info will be used by
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// profiles to grab decrypted values and such...
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uc_context* cpu_ctx;
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uc_context_alloc(obj->uc, &cpu_ctx);
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vm::instrs::emu_instr_t emu_instr{instr, cpu_ctx};
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obj->cc_trace->m_instrs.push_back(emu_instr);
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// RET or JMP REG means the end of a vm handler...
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if (instr.mnemonic == ZYDIS_MNEMONIC_RET ||
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(instr.mnemonic == ZYDIS_MNEMONIC_JMP &&
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instr.operands[0].type == ZYDIS_OPERAND_TYPE_REGISTER)) {
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// deobfuscate the instruction stream before profiling...
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// makes it easier for profiles to be correct...
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vm::instrs::deobfuscate(*obj->cc_trace);
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// find the last MOV REG, DWORD PTR [VIP] in the instruction stream, then
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// remove any instructions from this instruction to the JMP/RET...
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const auto rva_fetch = std::find_if(
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obj->cc_trace->m_instrs.rbegin(), obj->cc_trace->m_instrs.rend(),
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[&vip = obj->vip](const vm::instrs::emu_instr_t& instr) -> bool {
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const auto& i = instr.m_instr;
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return i.mnemonic == ZYDIS_MNEMONIC_MOV &&
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i.operands[0].type == ZYDIS_OPERAND_TYPE_REGISTER &&
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i.operands[1].type == ZYDIS_OPERAND_TYPE_MEMORY &&
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i.operands[1].mem.base == vip && i.operands[1].size == 32;
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});
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if (rva_fetch != obj->cc_trace->m_instrs.rend())
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obj->cc_trace->m_instrs.erase((rva_fetch + 1).base(),
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obj->cc_trace->m_instrs.end());
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const auto vinstr =
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vm::instrs::determine(obj->vip, obj->vsp, *obj->cc_trace);
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if (vinstr.mnemonic == vm::instrs::mnemonic_t::unknown) {
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zydis_rtn_t inst_stream;
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std::for_each(obj->cc_trace->m_instrs.begin(),
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obj->cc_trace->m_instrs.end(),
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[&](vm::instrs::emu_instr_t& instr) {
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inst_stream.push_back({instr.m_instr});
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});
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vm::utils::print(inst_stream);
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std::printf("========\n");
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std::getchar();
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} else {
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std::printf("> %s\n",
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vm::instrs::get_profile(vinstr.mnemonic)->name.c_str());
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}
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if (vinstr.mnemonic == vm::instrs::mnemonic_t::jmp) {
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obj->cc_trace->m_vip = obj->vip;
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obj->cc_trace->m_vsp = obj->vsp;
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}
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// free the trace since we will start a new one...
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std::for_each(obj->cc_trace->m_instrs.begin(),
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obj->cc_trace->m_instrs.end(),
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[&](const vm::instrs::emu_instr_t& instr) {
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uc_context_free(instr.m_cpu);
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});
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obj->cc_trace->m_instrs.clear();
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}
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return true;
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}
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void emu_t::invalid_mem(uc_engine* uc,
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uc_mem_type type,
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uint64_t address,
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int size,
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int64_t value,
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emu_t* obj) {
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switch (type) {
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case UC_MEM_READ_UNMAPPED: {
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uc_mem_map(uc, address & ~0xFFFull, PAGE_4KB, UC_PROT_ALL);
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std::printf(">>> reading invalid memory at address = %p, size = 0x%x\n",
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address, size);
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break;
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}
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case UC_MEM_WRITE_UNMAPPED: {
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uc_mem_map(uc, address & ~0xFFFull, PAGE_4KB, UC_PROT_ALL);
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std::printf(
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">>> writing invalid memory at address = %p, size = 0x%x, val = "
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"0x%x\n",
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address, size, value);
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break;
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}
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case UC_MEM_FETCH_UNMAPPED: {
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std::printf(">>> fetching invalid instructions at address = %p\n",
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address);
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std::uintptr_t rip, rsp;
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uc_reg_read(uc, UC_X86_REG_RSP, &rsp);
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uc_mem_read(uc, rsp, &rip, sizeof rip);
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rsp += 8;
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uc_reg_write(uc, UC_X86_REG_RSP, &rsp);
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uc_reg_write(uc, UC_X86_REG_RIP, &rip);
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std::printf(">>> injecting return to try and recover... rip = %p\n", rip);
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break;
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}
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default:
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break;
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}
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}
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} // namespace vm
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