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vmemu
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slow as all fuck, need to create a new method to use speculative

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execution to determine if a branch address is valid or not... fucking
cunt
master
John Doe 3 years ago
parent 3251b6e475
commit c35a646f64
3 changed files with 130 additions and 101 deletions
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23
include/vmemu_t.hpp
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@ -18,32 +18,19 @@ class emu_t {
explicit emu_t(vm::vmctx_t* vm_ctx);
~emu_t();
bool init();
void emulate();
/// <summary>
/// emulates a single virtual instruction and returns it... this function is
/// used internally to determine if virtual JCC addresses are legit...
/// </summary>
/// <returns>returns the single virtual instruction that was
/// emulated...</returns>
vm::instrs::vinstr_t step();
bool emulate(std::uint32_t vmenter_rva, vm::instrs::vrtn_t& vrtn);
private:
uc_engine* uc;
const vm::vmctx_t* m_vm;
zydis_reg_t vip, vsp;
vm::instrs::hndlr_trace_t cc_trace;
vm::instrs::vblk_t* cc_blk;
/// <summary>
/// single step structure information...
/// set to true when emulating the vm enter...
/// </summary>
struct {
bool m_toggle;
uc_context* cpu_context;
std::uint8_t stack[STACK_SIZE];
} m_single_step;
std::vector<vm::instrs::vinstr_t> vinstrs;
vm::instrs::hndlr_trace_t cc_trace;
bool m_vm_enter;
/// <summary>
/// unicorn engine hook

3
src/main.cpp
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@ -135,6 +135,7 @@ int __cdecl main(int argc, const char* argv[]) {
}
// TODO: rewrite this... using it to define profiles atm...
emu.emulate();
vm::instrs::vrtn_t virt_rtn;
emu.emulate(vm_entry_rva, virt_rtn);
}
}

173
src/vmemu_t.cpp
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@ -59,81 +59,42 @@ bool emu_t::init() {
return true;
}
vm::instrs::vinstr_t emu_t::step() {
m_single_step.m_toggle = true;
bool emu_t::emulate(std::uint32_t vmenter_rva, vm::instrs::vrtn_t& vrtn) {
uc_err err;
std::uintptr_t rip = m_vm->m_vm_entry_rva + m_vm->m_module_base,
std::uintptr_t rip = vmenter_rva + m_vm->m_module_base,
rsp = STACK_BASE + STACK_SIZE - PAGE_4KB;
if ((err = uc_reg_write(uc, UC_X86_REG_RSP, &rsp))) {
std::printf("> uc_reg_write error, reason = %d\n", err);
return;
return false;
}
if ((err = uc_reg_write(uc, UC_X86_REG_RIP, &rip))) {
std::printf("> uc_reg_write error, reason = %d\n", err);
return;
return false;
}
cc_trace.m_uc = uc;
cc_trace.m_vip = vip;
cc_trace.m_vsp = vsp;
vrtn.m_rva = vmenter_rva;
m_vm_enter = true;
// -- if there is already exists a cpu context back up then restore from it...
if (m_single_step.cpu_context) {
uc_context_restore(uc, m_single_step.cpu_context);
uc_mem_write(uc, STACK_BASE, m_single_step.stack, STACK_SIZE);
}
// -- single step emulate...
std::printf("> beginning execution at = %p\n", rip);
if ((err = uc_emu_start(uc, rip, 0ull, 0ull, 0ull))) {
std::printf("> error starting emu... reason = %d\n", err);
return;
}
// -- allocate new memory context...
if (!m_single_step.cpu_context) {
uc_context* ctx;
uc_context_alloc(uc, &ctx);
m_single_step.cpu_context = ctx;
}
// -- save cpu and stack...
uc_context_save(uc, m_single_step.cpu_context);
uc_mem_read(uc, STACK_BASE, m_single_step.stack, STACK_SIZE);
m_single_step.m_toggle = false;
return vinstrs.back();
}
void emu_t::emulate() {
uc_err err;
std::uintptr_t rip = m_vm->m_vm_entry_rva + m_vm->m_module_base,
rsp = STACK_BASE + STACK_SIZE - PAGE_4KB;
if ((err = uc_reg_write(uc, UC_X86_REG_RSP, &rsp))) {
std::printf("> uc_reg_write error, reason = %d\n", err);
return;
}
if ((err = uc_reg_write(uc, UC_X86_REG_RIP, &rip))) {
std::printf("> uc_reg_write error, reason = %d\n", err);
return;
}
cc_trace.m_uc = uc;
cc_trace.m_vip = vip;
cc_trace.m_vsp = vsp;
vm::instrs::vblk_t blk;
blk.m_vip = {0ull, 0ull};
blk.m_cpu = {nullptr, nullptr};
cc_blk = &blk;
std::printf("> beginning execution at = %p\n", rip);
if ((err = uc_emu_start(uc, rip, 0ull, 0ull, 0ull))) {
std::printf("> error starting emu... reason = %d\n", err);
return;
return false;
}
const auto jcc_result = has_jcc(vinstrs);
std::printf("> blk address = %p\n", blk.m_vip.img_base);
const auto jcc_result = has_jcc(blk.m_vinstrs);
std::printf("> jcc result = %d\n", jcc_result.has_value());
return true;
}
void emu_t::int_callback(uc_engine* uc, std::uint32_t intno, emu_t* obj) {
@ -194,7 +155,10 @@ bool emu_t::code_exec_callback(uc_engine* uc,
uc_context_alloc(obj->uc, &cpu_ctx);
uc_context_save(obj->uc, cpu_ctx);
vm::instrs::emu_instr_t emu_instr{instr, cpu_ctx};
std::uint8_t* stack = reinterpret_cast<std::uint8_t*>(malloc(STACK_SIZE));
uc_mem_read(uc, STACK_BASE, stack, STACK_SIZE);
vm::instrs::emu_instr_t emu_instr{instr, cpu_ctx, stack};
obj->cc_trace.m_instrs.push_back(emu_instr);
// RET or JMP REG means the end of a vm handler...
@ -221,15 +185,37 @@ bool emu_t::code_exec_callback(uc_engine* uc,
obj->cc_trace.m_instrs.erase((rva_fetch + 1).base(),
obj->cc_trace.m_instrs.end());
// extract vip address out of the vm enter trace...
if (obj->m_vm_enter) {
auto vip_addr_set = std::find_if(
obj->cc_trace.m_instrs.rbegin(), obj->cc_trace.m_instrs.rend(),
[&vip = obj->vip](vm::instrs::emu_instr_t& emu_instr) -> bool {
const auto& i = emu_instr.m_instr;
return i.operands[0].type == ZYDIS_OPERAND_TYPE_REGISTER &&
i.operands[0].reg.value == vip;
});
// get the cpu context from the instruction after the instruction that
// writes to vip...
--vip_addr_set;
uc_context* backup;
uc_context_alloc(uc, &backup);
uc_context_save(uc, backup);
uc_context_restore(uc, vip_addr_set->m_cpu);
std::uintptr_t vip_addr = 0ull;
uc_reg_read(uc, vm::instrs::reg_map[obj->vip], &vip_addr);
obj->cc_blk->m_vip.rva = vip_addr -= obj->m_vm->m_module_base;
obj->cc_blk->m_vip.img_base = vip_addr += obj->m_vm->m_image_base;
uc_context_restore(uc, backup);
uc_context_free(backup);
obj->m_vm_enter = false;
} else {
const auto vinstr =
vm::instrs::determine(obj->vip, obj->vsp, obj->cc_trace);
zydis_rtn_t inst_stream;
std::for_each(obj->cc_trace.m_instrs.begin(), obj->cc_trace.m_instrs.end(),
[&](vm::instrs::emu_instr_t& instr) {
inst_stream.push_back({instr.m_instr});
});
if (vinstr.mnemonic != vm::instrs::mnemonic_t::unknown) {
if (vinstr.imm.has_imm)
std::printf("> %s %p\n",
@ -239,25 +225,52 @@ bool emu_t::code_exec_callback(uc_engine* uc,
std::printf("> %s\n",
vm::instrs::get_profile(vinstr.mnemonic)->name.c_str());
} else {
zydis_rtn_t inst_stream;
std::for_each(obj->cc_trace.m_instrs.begin(),
obj->cc_trace.m_instrs.end(),
[&](vm::instrs::emu_instr_t& instr) {
inst_stream.push_back({instr.m_instr});
});
vm::utils::print(inst_stream);
std::getchar();
}
obj->cc_trace.m_vip = obj->vip;
obj->cc_trace.m_vsp = obj->vsp;
obj->vinstrs.push_back(vinstr);
obj->cc_blk->m_vinstrs.push_back(vinstr);
if (vinstr.mnemonic == vm::instrs::mnemonic_t::jmp) {
uc_context *b1, *b2;
uc_context_alloc(uc, &b1);
uc_context_alloc(uc, &b2);
uc_context_save(uc, b1);
uc_context_restore(uc, obj->cc_trace.m_instrs.begin()->m_cpu);
uc_context_save(uc, b2);
uc_context_restore(uc, b1);
std::uint8_t* stack =
reinterpret_cast<std::uint8_t*>(malloc(STACK_SIZE));
std::memcpy(stack, obj->cc_trace.m_instrs.begin()->stack, STACK_SIZE);
obj->cc_blk->m_cpu.ctx = b2;
obj->cc_blk->m_cpu.stack = stack;
}
if (vinstr.mnemonic == vm::instrs::mnemonic_t::jmp ||
vinstr.mnemonic == vm::instrs::mnemonic_t::vmexit)
uc_emu_stop(obj->uc);
}
// -- 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(instr.stack);
});
obj->cc_trace.m_instrs.clear();
if (vinstr.mnemonic == vm::instrs::mnemonic_t::jmp ||
vinstr.mnemonic == vm::instrs::mnemonic_t::vmexit ||
obj->m_single_step.m_toggle)
uc_emu_stop(obj->uc);
}
return true;
}
@ -315,7 +328,35 @@ std::optional<std::pair<std::uintptr_t, std::uintptr_t>> emu_t::has_jcc(
: val;
});
std::printf("> number of LCONST = %d\n", lconst_num);
if (lconst_num < 3)
return {};
const auto lconst1 = std::find_if(
vinstrs.rbegin(), vinstrs.rend(), [&](vm::instrs::vinstr_t& v) -> bool {
return v.mnemonic == vm::instrs::mnemonic_t::lconst && v.imm.size == 64;
});
const auto lconst2 = std::find_if(
lconst1 + 1, vinstrs.rend(), [&](vm::instrs::vinstr_t& v) -> bool {
return v.mnemonic == vm::instrs::mnemonic_t::lconst && v.imm.size == 64;
});
static const auto exec_callbk = [&](uc_engine* uc, uint64_t address,
uint32_t size, emu_t* obj) {};
uc_context *backup, *br1, *br2;
uc_context_alloc(uc, &backup);
uc_context_alloc(uc, &br1);
uc_context_alloc(uc, &br2);
uc_context_save(uc, backup);
uc_context_restore(uc, cc_blk->m_cpu.ctx);
uc_mem_write(uc, STACK_BASE, cc_blk->m_cpu.stack, STACK_SIZE);
uc_context_restore(uc, backup);
uc_context_free(backup);
uc_context_free(br1);
uc_context_free(br2);
return {};
}
} // namespace vm
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