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vmemu
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virtual branching is supported now...

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master
_xeroxz 3 years ago
parent f505253502
commit 4d3bb60489
2 changed files with 80 additions and 76 deletions
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5
include/vmemu_t.hpp
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@ -124,5 +124,10 @@ class emu_t {
/// <param name="branch_addr"></param>
/// <returns></returns>
bool legit_branch(vm::instrs::vblk_t& vblk, std::uintptr_t branch_addr);
/// <summary>
/// extracts the current code blocks branch data...
/// </summary>
void extract_branch_data();
};
} // namespace vm

119
src/vmemu_t.cpp
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@ -92,38 +92,8 @@ bool emu_t::emulate(std::uint32_t vmenter_rva, vm::instrs::vrtn_t& vrtn) {
return false;
}
auto br_info = could_have_jcc(cc_blk->m_vinstrs);
if (br_info.has_value()) {
auto [br1, br2] = br_info.value();
// convert to absolute addresses...
br1 -= m_vm->m_image_base;
br2 -= m_vm->m_image_base;
br1 += m_vm->m_module_base;
br2 += m_vm->m_module_base;
auto br1_legit = legit_branch(*cc_blk, br1);
auto br2_legit = legit_branch(*cc_blk, br2);
std::printf("> br1 legit: %d, br2 legit: %d\n", br1_legit, br2_legit);
if (br1_legit && br2_legit) {
std::printf("> virtual jcc uncovered... br1 = %p, br2 = %p\n", br1, br2);
cc_blk->branch_type = vm::instrs::vbranch_type::jcc;
cc_blk->branches.push_back(br1);
cc_blk->branches.push_back(br2);
} else if (br1_legit || br2_legit) {
std::printf("> absolute virtual jmp uncovered... branch = %p\n",
br1_legit ? br1 : br2);
cc_blk->branch_type = vm::instrs::vbranch_type::absolute;
cc_blk->branches.push_back(br1_legit ? br1 : br2);
} else {
std::printf("> unknown branch type...\n");
return false;
}
} else if (cc_blk->m_vinstrs.back().mnemonic ==
vm::instrs::mnemonic_t::vmexit) {
cc_blk->branch_type = vm::instrs::vbranch_type::none;
}
extract_branch_data();
std::printf("> emulated blk_%p\n\n", cc_blk->m_vip.img_base);
// keep track of the emulated blocks... by their addresses...
std::vector<std::uintptr_t> blk_addrs;
@ -134,11 +104,6 @@ bool emu_t::emulate(std::uint32_t vmenter_rva, vm::instrs::vrtn_t& vrtn) {
for (auto idx = 0u; idx < cc_vrtn->m_blks.size(); ++idx) {
vm::instrs::vblk_t blk = cc_vrtn->m_blks[idx];
if (blk.branch_type != vm::instrs::vbranch_type::none) {
std::uintptr_t vsp = 0ull;
uc_context_restore(uc, blk.m_jmp.ctx);
uc_mem_write(uc, STACK_BASE, blk.m_jmp.stack, STACK_SIZE);
uc_reg_read(uc, vm::instrs::reg_map[blk.m_vm.vsp], &vsp);
// force the emulation of all branches...
for (const auto br : blk.branches) {
// only emulate blocks that havent been emulated before...
@ -146,6 +111,11 @@ bool emu_t::emulate(std::uint32_t vmenter_rva, vm::instrs::vrtn_t& vrtn) {
blk_addrs.end())
continue;
std::uintptr_t vsp = 0ull;
uc_context_restore(uc, blk.m_jmp.ctx);
uc_mem_write(uc, STACK_BASE, blk.m_jmp.stack, STACK_SIZE);
uc_reg_read(uc, vm::instrs::reg_map[blk.m_vm.vsp], &vsp);
// setup new cc_blk...
auto& new_blk = vrtn.m_blks.emplace_back();
new_blk.m_vip = {0ull, 0ull};
@ -154,12 +124,35 @@ bool emu_t::emulate(std::uint32_t vmenter_rva, vm::instrs::vrtn_t& vrtn) {
// emulate the branch...
uc_mem_write(uc, vsp, &br, sizeof br);
uc_emu_start(uc, blk.m_jmp.rip, 0ull, 0ull, 0ull);
std::printf("> beginning execution at = %p\n", blk.m_jmp.rip);
if ((err = uc_emu_start(uc, blk.m_jmp.rip, 0ull, 0ull, 0ull))) {
std::printf("> error starting emu... reason = %d\n", err);
return false;
}
extract_branch_data();
std::printf("> emulated blk_%p\n", cc_blk->m_vip.img_base);
}
}
}
// free all virtual code block virtual jmp information...
std::for_each(vrtn.m_blks.begin(), vrtn.m_blks.end(),
[&](vm::instrs::vblk_t& blk) {
if (blk.m_jmp.ctx)
uc_context_free(blk.m_jmp.ctx);
if (blk.m_jmp.stack)
delete[] blk.m_jmp.stack;
});
return true;
}
void emu_t::extract_branch_data() {
auto br_info = could_have_jcc(cc_blk->m_vinstrs);
if (br_info.has_value()) {
auto [br1, br2] = br_info.value();
// convert to absolute addresses...
br1 -= m_vm->m_image_base;
br2 -= m_vm->m_image_base;
@ -171,8 +164,7 @@ bool emu_t::emulate(std::uint32_t vmenter_rva, vm::instrs::vrtn_t& vrtn) {
std::printf("> br1 legit: %d, br2 legit: %d\n", br1_legit, br2_legit);
if (br1_legit && br2_legit) {
std::printf("> virtual jcc uncovered... br1 = %p, br2 = %p\n", br1,
br2);
std::printf("> virtual jcc uncovered... br1 = %p, br2 = %p\n", br1, br2);
cc_blk->branch_type = vm::instrs::vbranch_type::jcc;
cc_blk->branches.push_back(br1);
cc_blk->branches.push_back(br2);
@ -183,27 +175,37 @@ bool emu_t::emulate(std::uint32_t vmenter_rva, vm::instrs::vrtn_t& vrtn) {
cc_blk->branches.push_back(br1_legit ? br1 : br2);
} else {
std::printf("> unknown branch type...\n");
return false;
}
} else if (cc_blk->m_vinstrs.back().mnemonic ==
vm::instrs::mnemonic_t::vmexit) {
cc_blk->branch_type = vm::instrs::vbranch_type::none;
} else if (cc_blk->m_vinstrs.back().mnemonic == vm::instrs::mnemonic_t::jmp) {
// see if there is 1 lconst...
if (auto last_lconst = std::find_if(
cc_blk->m_vinstrs.rbegin(), cc_blk->m_vinstrs.rend(),
[&](vm::instrs::vinstr_t& vinstr) -> bool {
return vinstr.mnemonic == vm::instrs::mnemonic_t::lconst &&
vinstr.imm.size == 64;
});
last_lconst != cc_blk->m_vinstrs.rend()) {
const auto imm_img_based = last_lconst->imm.val;
const auto imm_mod_based =
(imm_img_based - m_vm->m_image_base) + m_vm->m_module_base;
// check to see if the imm is inside of the module... and if the ptr lands
// inside of an executable section... then lastly check to see if its a
// legit branch or not...
if (imm_img_based >= m_vm->m_image_base &&
imm_img_based < m_vm->m_image_base + m_vm->m_image_size &&
vm::utils::scn::executable(m_vm->m_module_base, imm_mod_based)) {
cc_blk->branches.push_back(imm_mod_based);
cc_blk->branch_type = vm::instrs::vbranch_type::absolute;
}
} else {
std::printf("> jump table detected... review instruction stream...\n");
uc_emu_stop(uc);
}
}
}
// free all virtual code block virtual jmp information...
std::for_each(vrtn.m_blks.begin(), vrtn.m_blks.end(),
[&](vm::instrs::vblk_t& blk) {
if (blk.m_jmp.ctx)
uc_context_free(blk.m_jmp.ctx);
if (blk.m_jmp.stack)
delete[] blk.m_jmp.stack;
});
return true;
}
void emu_t::int_callback(uc_engine* uc, std::uint32_t intno, emu_t* obj) {
@ -395,13 +397,10 @@ 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->m_cpu);
auto uc_reg =
vm::instrs::reg_map[vip_write->m_instr.operands[0].reg.value];
uc_context_restore(uc, (--vip_write)->m_cpu);
std::uintptr_t vip_addr = 0ull;
uc_reg_read(uc, uc_reg, &vip_addr);
uc_reg_read(uc, vm::instrs::reg_map[obj->cc_trace.m_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;

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