🛡️ hARMless

An ARM64 ELF Packer/Loader for AArch64 Linux Binaries

A comprehensive security research tool that encrypts ARM64 ELF executables using multi-layer encryption and provides runtime in-memory execution without writing the original binary to disk.

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Features

• ARM64 ELF Support: Specifically designed for AArch64 Linux binaries
• Multi-Layer Encryption: Triple encryption using AES-256, ChaCha20, and RC4
• Memory Execution: Runtime decryption and execution entirely in memory using memfd_create
• Code Obfuscation: Advanced obfuscation techniques for anti-analysis
• CRC32 Verification: Integrity checking to detect tampering
• Self-Contained: Packed binaries are completely standalone
• Core Dump Prevention: Prevents memory dumps using setrlimit
• Secure Memory Wiping: Multi-pass memory erasure for sensitive data
• Direct Syscalls: Bypasses userland hooks for enhanced stealth
• Polymorphic Loader: Every packed binary is bytewise unique — randomized magic, filler, padding, and symbol table scrubbing at stub-generation time

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🚀 Quick Start

# Clone the repository
git clone https://github.com/litemars/hARMless.git
cd hARMless

# Build everything
make all

# Pack a binary
make pack INPUT=/bin/ls OUTPUT=packed_ls

# Run the packed binary
./packed_ls

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📦 Installation

Prerequisites

• ARM64/AArch64 Linux system or cross-compilation toolchain
• GCC for ARM64 (aarch64-linux-gnu-gcc or native)
• Make
• OpenSSL (libssl-dev) — required for AES-256 and ChaCha20 via the EVP API
• Standard development tools (git, build-essential)

Build Steps

# 1. Clone the repository
git clone https://github.com/litemars/hARMless.git
cd hARMless

# 2. Build all components
make all

# This creates:
# - build/packer    : Binary packer
# - build/loader    : Stub loader
# - build/stubgen   : Stub generator

Cross-Compilation (x86_64 → ARM64)

# Install ARM64 cross-compiler and OpenSSL
sudo apt-get install gcc-aarch64-linux-gnu libssl-dev

# Build with cross-compiler
make CC=aarch64-linux-gnu-gcc all

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📖 Usage

Basic Packing

# Pack an ARM64 binary
make pack INPUT=your_arm64_binary OUTPUT=packed_binary

# Alternative: Use tools directly
./build/packer your_arm64_binary packed_data
./build/stubgen ./build/loader packed_data packed_binary

Running Packed Binaries

# Simply execute the packed binary
./packed_binary

# The packed binary will:
# 1. Run anti-debug and anti-sandbox checks
# 2. Read its own embedded encrypted data
# 3. Decrypt the original ELF in memory
# 4. Verify integrity with CRC32
# 5. Create a masqueraded memfd and write the ELF into it
# 6. Delete itself from disk (unlink)
# 7. Execute directly from memory via /proc/self/fd/<memfd>

Test

# Testing using /bin/ls

make test
# Output: packed_binary: packed_ls

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Technical Details

Encryption Pipeline

The packer uses a triple-layer encryption approach:

1. AES-256-ECB: First encryption pass (OpenSSL EVP)
2. ChaCha20: Modern stream cipher for additional security (OpenSSL EVP)
3. RC4 Stream Cipher: Final obfuscation layer

Original Binary → AES-256 → ChaCha20 → RC4 → Packed Data

Key Generation: Cryptographically secure random keys from /dev/urandom (256 bits per layer)

In-Memory Write Paths

Three selectable methods for writing the decrypted ELF into the memfd (chosen at compile time):

Method	Flag	Kernel Requirement
io_uring (default)	-DCOPY_WITH_IO_URING	≥ 5.1
mmap	-DCOPY_WITH_MMAP	Any
write(2)	(neither flag)	Any

Polymorphic Engine

Every invocation of stubgen produces a bytewise-unique packed binary, even when packing the same input:

Mutation	Mechanism
Random magic	32-bit g_packed_magic patched to a fresh value from /dev/urandom; packed header is synchronized
Random filler	256-byte g_pack_polymorph array in .data overwritten with random bytes
Random padding	0–4095 bytes of random junk inserted between loader stub and payload
SC table re-keying	hARMless_sc[] re-encoded with a fresh random g_sc_xor_key so syscall numbers differ in every binary
String block re-keying	All 241 obfuscated string bytes in g_obf_str_block re-encoded with a fresh random g_str_xor_key
Header OTP blinding	Pack header body (140 bytes) XOR'd with the first 140 bytes of g_pack_polymorph as a one-time pad
Symbol scrub	.symtab/.strtab sections overwritten with random data; ELF section header fields zeroed

The result: no two packed outputs share the same byte pattern, defeating static hash-based signatures.

XOR-Obfuscated Syscall Table

Syscall numbers are stored in a volatile array (hARMless_sc[]) XOR-encoded with the key 0xDEADBEEF at compile time. At stub-generation time, stubgen re-encodes the entire table with a fresh random key written into g_sc_xor_key, so syscall numbers differ in every packed binary. They are decoded inline at each call site via hARMless_sc[i] ^ g_sc_xor_key, preventing static analysis tools from recovering syscall identifiers.

XOR-Obfuscated String Block

All anti-debug and process-masquerade strings (tool names, hypervisor signatures, env var names, process titles) are stored in a single contiguous g_obf_str_block[] array, XOR-encoded with g_str_xor_key. At stub-generation time, stubgen re-encodes the entire block with a fresh random byte key, making every binary's string patterns unique and independent of one another.

Memory Safety

• Secure Wiping: 3-pass overwrite (zeros, ones, random) with volatile access to prevent compiler optimization
• No Disk Writes: Original binary never touches filesystem
• Self-Deletion: Loader calls unlink() on itself before executing the payload
• ASLR Compatible: Position-independent code; random address slot reserved via mmap(NULL) before execution

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Security Features

Core Dump Prevention

setrlimit(RLIMIT_CORE, &(struct rlimit){0, 0});

Ensures sensitive memory is never written to disk, even during crashes.

Integrity Verification

CRC32 checksums detect any tampering with:

• Encrypted payload
• Decryption keys
• Loader code

Anti-Analysis

• No debug symbols: Stripped binaries; section header table zeroed at stub-generation time
• Obfuscated control flow: Reduces reverse engineering surface
• Obfuscated syscall numbers: Stored XOR'd with 0xDEADBEEF, decoded at each call site
• Direct syscalls: Evades LD_PRELOAD and EDR hooks
• Noise delays: CPU-bound xorshift loops seeded from the ASLR stack address; cannot be skipped by sandbox time-acceleration and emit no recognizable timing syscall
• Process context probes: getpid, getppid, and prctl(PR_GET_NAME) woven between critical operations; results used in a runtime condition to avoid trivial dead-code elimination by an analyst
• In-memory execution: No /tmp artifacts

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Architecture

┌─────────────────────────────────────────────────────────┐
│                    Original Binary                      │
└────────────────────┬────────────────────────────────────┘
                     │
                     ▼
         ┌───────────────────────┐
         │   Packer (packer.c)   │
         │  - Read ELF           │
         │  - Generate keys      │
         │  - Triple encrypt     │
         │  - Compute CRC32      │
         └───────────┬───────────┘
                     │
                     ▼
         ┌───────────────────────┐
         │  Packed Data File     │
         │  [encrypted payload]  │
         └───────────┬───────────┘
                     │
                     ▼
         ┌───────────────────────┐
         │ Stub Generator        │
         │ (stubgen.c)           │
         │  - Patch magic/filler │
         │  - Scrub symbols      │
         │  - Insert padding     │
         │  - Append payload     │
         └───────────┬───────────┘
                     │
                     ▼
┌────────────────────────────────────────────────────────┐
│              Packed Binary (Output)                    │
│  ┌──────────────────────────────────────────────┐      │
│  │ Loader Stub (loader.c)                       │      │
│  │  - Anti-debug / anti-sandbox checks          │      │
│  │  - Decrypt (RC4 → ChaCha20 → AES-256)        │      │
│  │  - Verify CRC32                              │      │
│  │  - Create masqueraded memfd                  │      │
│  │  - Unlink self                               │      │
│  │  - Execute via /proc/self/fd/<N>             │      │
│  └──────────────────────────────────────────────┘      │
│  ┌──────────────────────────────────────────────┐      │
│  │ [random padding] Encrypted Payload + Header  │      │
│  └──────────────────────────────────────────────┘      │
└────────────────────────────────────────────────────────┘
                     │
                     ▼
         ┌───────────────────────┐
         │   Runtime Execution   │
         │  (in-memory only)     │
         └───────────────────────┘

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🤝 Contributing

Contributions are welcome! Please see CONTRIBUTING.md for guidelines.

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⚠️ Legal Notice: This tool is intended for:

• Authorized penetration testing
• Security research and education
• Red team operations
• Malware analysis

Unauthorized use is prohibited and may be illegal.

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📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

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