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@ -2,7 +2,10 @@
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namespace vm {
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namespace vm {
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emu_t::emu_t(vm::vmctx_t* vm_ctx)
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emu_t::emu_t(vm::vmctx_t* vm_ctx)
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: m_vm(vm_ctx), vip(vm_ctx->get_vip()), vsp(vm_ctx->get_vsp()) {}
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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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m_sreg_cnt(0u) {}
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emu_t::~emu_t() {
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emu_t::~emu_t() {
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if (uc)
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if (uc)
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@ -81,6 +84,7 @@ bool emu_t::emulate(std::uint32_t vmenter_rva, vm::instrs::vrtn_t& vrtn) {
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vm::instrs::vblk_t blk;
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vm::instrs::vblk_t blk;
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blk.m_vip = {0ull, 0ull};
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blk.m_vip = {0ull, 0ull};
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blk.m_vm = {vip, vsp};
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cc_blk = &blk;
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cc_blk = &blk;
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cc_vrtn = &vrtn;
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cc_vrtn = &vrtn;
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@ -91,9 +95,27 @@ bool emu_t::emulate(std::uint32_t vmenter_rva, vm::instrs::vrtn_t& vrtn) {
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return false;
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return false;
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}
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}
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std::printf(
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auto res = could_have_jcc(blk.m_vinstrs);
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"> blk_%p, number of virtual instructions = %d, could have a jcc = %d\n",
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std::printf("> blk_%p, number of virtual instructions = %d\n",
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blk.m_vip.img_base, blk.m_vinstrs.size(), could_have_jcc(blk.m_vinstrs));
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blk.m_vip.img_base, blk.m_vinstrs.size());
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if (res.has_value()) {
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const auto [b1, b2] = res.value();
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auto b1_legit =
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legit_branch(blk, (b1 - m_vm->m_image_base) + m_vm->m_module_base);
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auto b2_legit =
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legit_branch(blk, (b2 - m_vm->m_image_base) + m_vm->m_module_base);
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if (b1_legit && b2_legit) {
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blk.branches.push_back(b1);
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blk.branches.push_back(b2);
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blk.branch_type = vm::instrs::vbranch_type::jcc;
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std::printf("> code block has jcc, b1 = %p, b2 = %p\n", b1, b2);
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} else {
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blk.branch_type = vm::instrs::vbranch_type::absolute;
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std::printf("> code block has absolute jmp...\n");
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}
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}
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return true;
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return true;
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}
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}
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@ -128,6 +150,92 @@ void emu_t::int_callback(uc_engine* uc, std::uint32_t intno, emu_t* obj) {
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}
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}
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}
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}
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bool emu_t::branch_pred_spec_exec(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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uc_context* ctx;
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uc_context_alloc(uc, &ctx);
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uc_context_save(uc, ctx);
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// if this is the first instruction of this handler then save the stack...
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if (!obj->cc_trace.m_instrs.size()) {
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obj->cc_trace.m_stack = reinterpret_cast<std::uint8_t*>(malloc(STACK_SIZE));
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uc_mem_read(uc, STACK_BASE, obj->cc_trace.m_stack, STACK_SIZE);
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}
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obj->cc_trace.m_instrs.push_back({instr, ctx});
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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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// -- free the trace since we will start a new one...
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std::for_each(obj->cc_trace.m_instrs.begin(), 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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free(obj->cc_trace.m_stack);
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obj->cc_trace.m_instrs.clear();
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if (vinstr.mnemonic != vm::instrs::mnemonic_t::jmp) {
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if (vinstr.mnemonic != vm::instrs::mnemonic_t::sreg)
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uc_emu_stop(uc);
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if (!vinstr.imm.has_imm)
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uc_emu_stop(uc);
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if (vinstr.imm.size != 8 ||
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vinstr.imm.val > std::numeric_limits<std::uint8_t>::max())
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uc_emu_stop(uc);
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// -- stop after 10 legit SREG's...
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if (++obj->m_sreg_cnt == 10)
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uc_emu_stop(uc);
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}
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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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bool emu_t::code_exec_callback(uc_engine* uc,
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uint64_t address,
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uint64_t address,
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uint32_t size,
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uint32_t size,
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@ -154,7 +262,7 @@ bool emu_t::code_exec_callback(uc_engine* uc,
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// if this is the first instruction of this handler then save the stack...
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// if this is the first instruction of this handler then save the stack...
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if (!obj->cc_trace.m_instrs.size()) {
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if (!obj->cc_trace.m_instrs.size()) {
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obj->cc_trace.m_stack = reinterpret_cast<std::uint8_t*>(malloc(STACK_SIZE));
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obj->cc_trace.m_stack = new std::uint8_t[STACK_SIZE];
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uc_mem_read(uc, STACK_BASE, obj->cc_trace.m_stack, STACK_SIZE);
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uc_mem_read(uc, STACK_BASE, obj->cc_trace.m_stack, STACK_SIZE);
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}
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}
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@ -197,7 +305,7 @@ bool emu_t::code_exec_callback(uc_engine* uc,
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uc_context* backup;
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uc_context* backup;
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uc_context_alloc(uc, &backup);
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uc_context_alloc(uc, &backup);
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uc_context_save(uc, backup);
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uc_context_save(uc, backup);
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uc_context_restore(uc, (vip_write - 1)->m_cpu);
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uc_context_restore(uc, vip_write->m_cpu);
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auto uc_reg =
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auto uc_reg =
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vm::instrs::reg_map[vip_write->m_instr.operands[0].reg.value];
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vm::instrs::reg_map[vip_write->m_instr.operands[0].reg.value];
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@ -257,7 +365,8 @@ bool emu_t::code_exec_callback(uc_engine* uc,
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// set current code block virtual jmp instruction information...
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// set current code block virtual jmp instruction information...
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obj->cc_blk->m_jmp.ctx = copy;
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obj->cc_blk->m_jmp.ctx = copy;
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obj->cc_blk->m_jmp.stack = new std::uint8_t[STACK_SIZE];
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obj->cc_blk->m_jmp.stack = new std::uint8_t[STACK_SIZE];
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uc_mem_read(uc, STACK_BASE, obj->cc_blk->m_jmp.stack, STACK_SIZE);
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std::memcpy(obj->cc_blk->m_jmp.stack, obj->cc_trace.m_stack,
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STACK_SIZE);
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}
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}
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if (vinstr.mnemonic == vm::instrs::mnemonic_t::jmp ||
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if (vinstr.mnemonic == vm::instrs::mnemonic_t::jmp ||
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@ -316,7 +425,40 @@ void emu_t::invalid_mem(uc_engine* uc,
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}
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}
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}
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}
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bool emu_t::could_have_jcc(std::vector<vm::instrs::vinstr_t>& vinstrs) {
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bool emu_t::legit_branch(vm::instrs::vblk_t& vblk, std::uintptr_t branch_addr) {
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// remove normal execution callback...
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uc_hook_del(uc, code_exec_hook);
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// add branch pred hook...
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uc_hook_add(uc, &branch_pred_hook, UC_HOOK_CODE,
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(void*)&vm::emu_t::branch_pred_spec_exec, this,
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m_vm->m_module_base, m_vm->m_module_base + m_vm->m_image_size);
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// restore cpu and stack...
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uc_context_restore(uc, vblk.m_jmp.ctx);
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uc_mem_write(uc, STACK_BASE, vblk.m_jmp.stack, STACK_SIZE);
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std::uintptr_t vsp_ptr = 0ull, rip = 0ull;
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uc_reg_read(uc, UC_X86_REG_RIP, &rip);
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uc_reg_read(uc, vm::instrs::reg_map[vblk.m_vm.vsp], &vsp_ptr);
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uc_mem_write(uc, vsp_ptr, &branch_addr, sizeof branch_addr);
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m_sreg_cnt = 0u;
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uc_emu_start(uc, rip, 0ull, 0ull, 0ull);
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// add normal execution callback back...
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uc_hook_add(uc, &code_exec_hook, UC_HOOK_CODE,
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(void*)&vm::emu_t::code_exec_callback, this, m_vm->m_module_base,
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m_vm->m_module_base + m_vm->m_image_size);
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return m_sreg_cnt == 10;
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}
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std::optional<std::pair<std::uintptr_t, std::uintptr_t>> emu_t::could_have_jcc(
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std::vector<vm::instrs::vinstr_t>& vinstrs) {
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if (vinstrs.back().mnemonic == vm::instrs::mnemonic_t::vmexit)
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return {};
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// check to see if there is at least 3 LCONST %i64's
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// check to see if there is at least 3 LCONST %i64's
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if (std::accumulate(
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if (std::accumulate(
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vinstrs.begin(), vinstrs.end(), 0u,
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vinstrs.begin(), vinstrs.end(), 0u,
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@ -326,7 +468,7 @@ bool emu_t::could_have_jcc(std::vector<vm::instrs::vinstr_t>& vinstrs) {
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? ++val
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? ++val
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: val;
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: val;
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}) < 3)
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}) < 3)
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return false;
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return {};
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// extract the lconst64's out of the virtual instruction stream...
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// extract the lconst64's out of the virtual instruction stream...
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static const auto lconst64_chk = [&](vm::instrs::vinstr_t& v) -> bool {
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static const auto lconst64_chk = [&](vm::instrs::vinstr_t& v) -> bool {
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@ -337,19 +479,19 @@ bool emu_t::could_have_jcc(std::vector<vm::instrs::vinstr_t>& vinstrs) {
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std::find_if(vinstrs.rbegin(), vinstrs.rend(), lconst64_chk);
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std::find_if(vinstrs.rbegin(), vinstrs.rend(), lconst64_chk);
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if (lconst1 == vinstrs.rend())
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if (lconst1 == vinstrs.rend())
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return false;
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return {};
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const auto lconst2 = std::find_if(lconst1 + 1, vinstrs.rend(), lconst64_chk);
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const auto lconst2 = std::find_if(lconst1 + 1, vinstrs.rend(), lconst64_chk);
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if (lconst2 == vinstrs.rend())
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if (lconst2 == vinstrs.rend())
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return false;
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return {};
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// check to see if the imm val is inside of the image...
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// check to see if the imm val is inside of the image...
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if (lconst1->imm.val > m_vm->m_image_base + m_vm->m_image_size ||
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if (lconst1->imm.val > m_vm->m_image_base + m_vm->m_image_size ||
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lconst1->imm.val < m_vm->m_image_base ||
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lconst1->imm.val < m_vm->m_image_base ||
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lconst2->imm.val > m_vm->m_image_base + m_vm->m_image_size ||
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lconst2->imm.val > m_vm->m_image_base + m_vm->m_image_size ||
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lconst2->imm.val < m_vm->m_image_base)
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lconst2->imm.val < m_vm->m_image_base)
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return false;
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return {};
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// check to see if the imm's points to something inside of an executable
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// check to see if the imm's points to something inside of an executable
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// section...
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// section...
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@ -359,8 +501,8 @@ bool emu_t::could_have_jcc(std::vector<vm::instrs::vinstr_t>& vinstrs) {
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!vm::utils::scn::executable(
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!vm::utils::scn::executable(
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m_vm->m_module_base,
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m_vm->m_module_base,
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(lconst2->imm.val - m_vm->m_image_base) + m_vm->m_module_base))
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(lconst2->imm.val - m_vm->m_image_base) + m_vm->m_module_base))
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return false;
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return {};
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return true;
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|
return {{lconst1->imm.val, lconst2->imm.val}};
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}
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}
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} // namespace vm
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} // namespace vm
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