diff --git a/deps/vmprofiler b/deps/vmprofiler index 4e8c37d..322a8bc 160000 --- a/deps/vmprofiler +++ b/deps/vmprofiler @@ -1 +1 @@ -Subproject commit 4e8c37dbe0fa60018e543cbc47da2ee22e159efd +Subproject commit 322a8bcf97d47a6d792c97d803429303106958da diff --git a/include/vmemu_t.hpp b/include/vmemu_t.hpp index 3b63cf8..5dd40c4 100644 --- a/include/vmemu_t.hpp +++ b/include/vmemu_t.hpp @@ -25,6 +25,11 @@ class emu_t { const vm::vmctx_t* m_vm; zydis_reg_t vip, vsp; + /// + /// used in branch_pred_spec_exec to count legit SREG virtual instructions... + /// + std::uint8_t m_sreg_cnt; + /// /// current code trace... /// @@ -44,7 +49,7 @@ class emu_t { /// /// unicorn engine hook /// - uc_hook code_exec_hook, invalid_mem_hook, int_hook; + uc_hook code_exec_hook, invalid_mem_hook, int_hook, branch_pred_hook; /// /// code execution callback for executable memory ranges of the vmprotect'ed @@ -61,6 +66,21 @@ class emu_t { uint32_t size, emu_t* obj); + /// + /// branch predicition with speculative execution (emulation)... this callback + /// ensures there are at least 10 SREG's and that all of the imm values are + /// legit... + /// + /// + /// + /// + /// + /// + static bool branch_pred_spec_exec(uc_engine* uc, + uint64_t address, + uint32_t size, + emu_t* obj); + /// /// invalid memory access handler. no runtime values can possibly effect the /// decryption of virtual instructions. thus invalid memory accesses can be @@ -89,21 +109,21 @@ class emu_t { static void int_callback(uc_engine* uc, std::uint32_t intno, emu_t* obj); /// - /// determines if its possible that the virtual instruction stream contains a - /// virtual JCC... - /// - /// this simply checks to see if there are at least 3 LCONST that load 64bit - /// constant values... - /// - /// it also checks if the last 2 LCONST's load image based addresses which - /// land inside of executable sections... - /// - /// this function cannot be used to determine if there is a virtual branch or - /// not... it is only a useful/preliminary function... + /// determines if there *could* be a JCC in the virtual code block... its not + /// 100%... speculative execution is required to ensure that both branches + /// discovered are legit... + /// + /// + /// + std::optional> could_have_jcc( + std::vector& vinstrs); + + /// + /// determines if a branch is legit or not... /// - /// vector of virtual instructions... - /// returns true if there is at least 3 LCONST in the virtual - /// instruction stream that load 64bit values... - bool could_have_jcc(std::vector& vinstrs); + /// + /// + /// + bool legit_branch(vm::instrs::vblk_t& vblk, std::uintptr_t branch_addr); }; } // namespace vm diff --git a/src/vmemu_t.cpp b/src/vmemu_t.cpp index b14fa3b..cd56d41 100644 --- a/src/vmemu_t.cpp +++ b/src/vmemu_t.cpp @@ -2,7 +2,10 @@ namespace vm { emu_t::emu_t(vm::vmctx_t* vm_ctx) - : m_vm(vm_ctx), vip(vm_ctx->get_vip()), vsp(vm_ctx->get_vsp()) {} + : m_vm(vm_ctx), + vip(vm_ctx->get_vip()), + vsp(vm_ctx->get_vsp()), + m_sreg_cnt(0u) {} emu_t::~emu_t() { if (uc) @@ -81,6 +84,7 @@ bool emu_t::emulate(std::uint32_t vmenter_rva, vm::instrs::vrtn_t& vrtn) { vm::instrs::vblk_t blk; blk.m_vip = {0ull, 0ull}; + blk.m_vm = {vip, vsp}; cc_blk = &blk; cc_vrtn = &vrtn; @@ -91,9 +95,27 @@ bool emu_t::emulate(std::uint32_t vmenter_rva, vm::instrs::vrtn_t& vrtn) { return false; } - std::printf( - "> blk_%p, number of virtual instructions = %d, could have a jcc = %d\n", - blk.m_vip.img_base, blk.m_vinstrs.size(), could_have_jcc(blk.m_vinstrs)); + auto res = could_have_jcc(blk.m_vinstrs); + std::printf("> blk_%p, number of virtual instructions = %d\n", + blk.m_vip.img_base, blk.m_vinstrs.size()); + + if (res.has_value()) { + const auto [b1, b2] = res.value(); + auto b1_legit = + legit_branch(blk, (b1 - m_vm->m_image_base) + m_vm->m_module_base); + auto b2_legit = + legit_branch(blk, (b2 - m_vm->m_image_base) + m_vm->m_module_base); + + if (b1_legit && b2_legit) { + blk.branches.push_back(b1); + blk.branches.push_back(b2); + blk.branch_type = vm::instrs::vbranch_type::jcc; + std::printf("> code block has jcc, b1 = %p, b2 = %p\n", b1, b2); + } else { + blk.branch_type = vm::instrs::vbranch_type::absolute; + std::printf("> code block has absolute jmp...\n"); + } + } return true; } @@ -128,6 +150,92 @@ void emu_t::int_callback(uc_engine* uc, std::uint32_t intno, emu_t* obj) { } } +bool emu_t::branch_pred_spec_exec(uc_engine* uc, + uint64_t address, + uint32_t size, + emu_t* obj) { + uc_err err; + static thread_local zydis_decoded_instr_t instr; + if (!ZYAN_SUCCESS(ZydisDecoderDecodeBuffer(vm::utils::g_decoder.get(), + reinterpret_cast(address), + PAGE_4KB, &instr))) { + std::printf("> failed to decode instruction at = 0x%p\n", address); + if ((err = uc_emu_stop(uc))) { + std::printf("> failed to stop emulation, exiting... reason = %d\n", err); + exit(0); + } + return false; + } + + if (instr.mnemonic == ZYDIS_MNEMONIC_INVALID) + return false; + + uc_context* ctx; + uc_context_alloc(uc, &ctx); + uc_context_save(uc, ctx); + + // if this is the first instruction of this handler then save the stack... + if (!obj->cc_trace.m_instrs.size()) { + obj->cc_trace.m_stack = reinterpret_cast(malloc(STACK_SIZE)); + uc_mem_read(uc, STACK_BASE, obj->cc_trace.m_stack, STACK_SIZE); + } + + obj->cc_trace.m_instrs.push_back({instr, ctx}); + + // RET or JMP REG means the end of a vm handler... + if (instr.mnemonic == ZYDIS_MNEMONIC_RET || + (instr.mnemonic == ZYDIS_MNEMONIC_JMP && + instr.operands[0].type == ZYDIS_OPERAND_TYPE_REGISTER)) { + // deobfuscate the instruction stream before profiling... + // makes it easier for profiles to be correct... + vm::instrs::deobfuscate(obj->cc_trace); + + // find the last MOV REG, DWORD PTR [VIP] in the instruction stream, then + // remove any instructions from this instruction to the JMP/RET... + const auto rva_fetch = std::find_if( + obj->cc_trace.m_instrs.rbegin(), obj->cc_trace.m_instrs.rend(), + [&vip = obj->vip](const vm::instrs::emu_instr_t& instr) -> bool { + const auto& i = instr.m_instr; + return i.mnemonic == ZYDIS_MNEMONIC_MOV && + i.operands[0].type == ZYDIS_OPERAND_TYPE_REGISTER && + i.operands[1].type == ZYDIS_OPERAND_TYPE_MEMORY && + i.operands[1].mem.base == vip && i.operands[1].size == 32; + }); + + if (rva_fetch != obj->cc_trace.m_instrs.rend()) + obj->cc_trace.m_instrs.erase((rva_fetch + 1).base(), + obj->cc_trace.m_instrs.end()); + + const auto vinstr = + vm::instrs::determine(obj->vip, obj->vsp, obj->cc_trace); + + // -- free the trace since we will start a new one... + std::for_each(obj->cc_trace.m_instrs.begin(), obj->cc_trace.m_instrs.end(), + [&](const vm::instrs::emu_instr_t& instr) { + uc_context_free(instr.m_cpu); + }); + + free(obj->cc_trace.m_stack); + obj->cc_trace.m_instrs.clear(); + + if (vinstr.mnemonic != vm::instrs::mnemonic_t::jmp) { + if (vinstr.mnemonic != vm::instrs::mnemonic_t::sreg) + uc_emu_stop(uc); + + if (!vinstr.imm.has_imm) + uc_emu_stop(uc); + + if (vinstr.imm.size != 8 || + vinstr.imm.val > std::numeric_limits::max()) + uc_emu_stop(uc); + + // -- stop after 10 legit SREG's... + if (++obj->m_sreg_cnt == 10) + uc_emu_stop(uc); + } + } +} + bool emu_t::code_exec_callback(uc_engine* uc, uint64_t address, uint32_t size, @@ -154,7 +262,7 @@ bool emu_t::code_exec_callback(uc_engine* uc, // if this is the first instruction of this handler then save the stack... if (!obj->cc_trace.m_instrs.size()) { - obj->cc_trace.m_stack = reinterpret_cast(malloc(STACK_SIZE)); + obj->cc_trace.m_stack = new std::uint8_t[STACK_SIZE]; uc_mem_read(uc, STACK_BASE, obj->cc_trace.m_stack, STACK_SIZE); } @@ -197,7 +305,7 @@ bool emu_t::code_exec_callback(uc_engine* uc, uc_context* backup; uc_context_alloc(uc, &backup); uc_context_save(uc, backup); - uc_context_restore(uc, (vip_write - 1)->m_cpu); + uc_context_restore(uc, vip_write->m_cpu); auto uc_reg = vm::instrs::reg_map[vip_write->m_instr.operands[0].reg.value]; @@ -257,7 +365,8 @@ bool emu_t::code_exec_callback(uc_engine* uc, // set current code block virtual jmp instruction information... obj->cc_blk->m_jmp.ctx = copy; obj->cc_blk->m_jmp.stack = new std::uint8_t[STACK_SIZE]; - uc_mem_read(uc, STACK_BASE, obj->cc_blk->m_jmp.stack, STACK_SIZE); + std::memcpy(obj->cc_blk->m_jmp.stack, obj->cc_trace.m_stack, + STACK_SIZE); } if (vinstr.mnemonic == vm::instrs::mnemonic_t::jmp || @@ -316,7 +425,40 @@ void emu_t::invalid_mem(uc_engine* uc, } } -bool emu_t::could_have_jcc(std::vector& vinstrs) { +bool emu_t::legit_branch(vm::instrs::vblk_t& vblk, std::uintptr_t branch_addr) { + // remove normal execution callback... + uc_hook_del(uc, code_exec_hook); + + // add branch pred hook... + uc_hook_add(uc, &branch_pred_hook, UC_HOOK_CODE, + (void*)&vm::emu_t::branch_pred_spec_exec, this, + m_vm->m_module_base, m_vm->m_module_base + m_vm->m_image_size); + + // restore cpu and stack... + uc_context_restore(uc, vblk.m_jmp.ctx); + uc_mem_write(uc, STACK_BASE, vblk.m_jmp.stack, STACK_SIZE); + + std::uintptr_t vsp_ptr = 0ull, rip = 0ull; + uc_reg_read(uc, UC_X86_REG_RIP, &rip); + uc_reg_read(uc, vm::instrs::reg_map[vblk.m_vm.vsp], &vsp_ptr); + uc_mem_write(uc, vsp_ptr, &branch_addr, sizeof branch_addr); + + m_sreg_cnt = 0u; + uc_emu_start(uc, rip, 0ull, 0ull, 0ull); + + // add normal execution callback back... + uc_hook_add(uc, &code_exec_hook, UC_HOOK_CODE, + (void*)&vm::emu_t::code_exec_callback, this, m_vm->m_module_base, + m_vm->m_module_base + m_vm->m_image_size); + + return m_sreg_cnt == 10; +} + +std::optional> emu_t::could_have_jcc( + std::vector& vinstrs) { + if (vinstrs.back().mnemonic == vm::instrs::mnemonic_t::vmexit) + return {}; + // check to see if there is at least 3 LCONST %i64's if (std::accumulate( vinstrs.begin(), vinstrs.end(), 0u, @@ -326,7 +468,7 @@ bool emu_t::could_have_jcc(std::vector& vinstrs) { ? ++val : val; }) < 3) - return false; + return {}; // extract the lconst64's out of the virtual instruction stream... static const auto lconst64_chk = [&](vm::instrs::vinstr_t& v) -> bool { @@ -337,19 +479,19 @@ bool emu_t::could_have_jcc(std::vector& vinstrs) { std::find_if(vinstrs.rbegin(), vinstrs.rend(), lconst64_chk); if (lconst1 == vinstrs.rend()) - return false; + return {}; const auto lconst2 = std::find_if(lconst1 + 1, vinstrs.rend(), lconst64_chk); if (lconst2 == vinstrs.rend()) - return false; + return {}; // check to see if the imm val is inside of the image... if (lconst1->imm.val > m_vm->m_image_base + m_vm->m_image_size || lconst1->imm.val < m_vm->m_image_base || lconst2->imm.val > m_vm->m_image_base + m_vm->m_image_size || lconst2->imm.val < m_vm->m_image_base) - return false; + return {}; // check to see if the imm's points to something inside of an executable // section... @@ -359,8 +501,8 @@ bool emu_t::could_have_jcc(std::vector& vinstrs) { !vm::utils::scn::executable( m_vm->m_module_base, (lconst2->imm.val - m_vm->m_image_base) + m_vm->m_module_base)) - return false; + return {}; - return true; + return {{lconst1->imm.val, lconst2->imm.val}}; } } // namespace vm \ No newline at end of file