Octopus

Huge thanks to QuoScient for having sponsored this project.

Octopus is a security analysis framework for WebAssembly module and Blockchain Smart Contract.

The purpose of Octopus is to provide an easy way to analyze closed-source WebAssembly module and smart contracts bytecode to understand deeper their internal behaviours.

Features

Explorer: Octopus JSON-RPC client implementation to communicate with blockchain platforms
Disassembler: Octopus can translate bytecode into assembly representation
Control Flow Analysis: Octopus can generate a Control Flow Graph (CFG)
Call Flow Analysis: Octopus can generate a Call Flow Graph (function level)
IR conversion (SSA): Octopus can simplify assembly into Static Single Assignment (SSA) representation
Symbolic Execution: Octopus use symbolic execution to find new paths into a program

Platforms / Architectures

Octopus support the following types of programs/smart contracts:

WebAssembly module (WASM)
Bitcoin script (BTC script)
Ethereum smart contracts (EVM bytecode & Ewasm)
EOS smart contracts (WASM)
NEO smart contracts (AVM bytecode)

	BTC	ETH (EVM)	ETH (WASM)	EOS	NEO	WASM
Explorer	✔️	✔️	✔️	✔️	✔️	⭕
Disassembler	✔️	✔️	✔️	✔️	✔️	✔️
Control Flow Analysis	✖️	✔️	✔️	✔️	✔️	✔️
Call Flow Analysis	✖️	➕	✔️	✔️	➕	✔️
IR conversion (SSA)	✖️	✔️	➕	➕	✖️	✔️
Symbolic Execution	✖️	➕	➕	➕	✖️	➕

PyPI package ✔️
Docker ✔️

✔️ DONE / ➕ WIP / ✖️ TODO / ⭕ N/A

Requirements

Octopus is supported on Linux (ideally Ubuntu 16.04) and requires Python >=3.5 (ideally 3.6).

Dependencies:

Graph generation: graphviz
Explorer: requests
Symbolic Execution: z3-solver
Wasm: wasm

Quick Start

Install system dependencies

# Install system dependencies
sudo apt-get update && sudo apt-get install python-pip graphviz xdg-utils -y

Install Octopus:

# Download Octopus
git clone https://github.com/pventuzelo/octopus
cd octopus

# Install Octopus library/CLI and its dependencies
python3 setup.py install

# but prefer the first way to install if possible
pip3 install octopus

Run tests

# Run tests for all platforms (disassembly, CFG, ...)
./run_tests.sh
# Run tests that require internet access (explorer tests)
./run_explorer_tests.sh

# Run tests for only one platforms
# {btc, eth, eos, neo, wasm}_run_tests.sh
cd octopus/tests/
./wasm_run_tests.sh

Docker container

A docker container providing the toolset is available at docker hub. In a terminal, run the following commands:

docker pull smartbugs/octopus
docker run -it smartbugs/octopus
cd octopus
python3 octopus_eth_evm.py -s -f examples/ETH/evm_bytecode/61EDCDf5bb737ADffE5043706e7C5bb1f1a56eEA.bytecode

Command-line tools

WebAssembly: octopus_wasm.py
Ethereum (EVM): octopus_eth_evm.py

In-depth Examples using APIs

WebAssembly

Disassembler

Disassembly of a Wasm module:

from octopus.arch.wasm.disassembler import WasmDisassembler

FILE = "examples/wasm/samples/helloworld.wasm"

with open(FILE, 'rb') as f:
    module_bytecode = f.read()

disasm = WasmDisassembler()
# return list of functions instructions (list)
print(disasm.disassemble_module(module_bytecode))
#[[<octopus.arch.wasm.instruction.WasmInstruction at 0x7f85e4904278>,<octopus.arch.wasm.instruction.WasmInstruction at 0x7f85e4904f60>,<octopus.arch.wasm.instruction.WasmInstruction at 0x7f85e4904ef0>]]

print()
# return text of functions code
print(disasm.disassemble_module(module_bytecode, r_format='text'))
# func 0
# i32.const 0
# call 0
# end

Disassembly of wasm bytecode:

from octopus.arch.wasm.disassembler import WasmDisassembler

# bytecode in WebAssembly is the function code (i.e. function body)
bytecode = b'\x02\x7fA\x18\x10\x1cA\x00\x0f\x0b'
# create a WasmDisassembler object
disasm = WasmDisassembler(bytecode)

# disassemble bytecode into a list of WasmInstruction
# attributes r_format='list' by default
print(disasm.disassemble())

#[<octopus.arch.wasm.instruction.WasmInstruction object at 0x7f85e4904eb8>, <octopus.arch.wasm.instruction.WasmInstruction object at 0x7f85e4904278>, <octopus.arch.wasm.instruction.WasmInstruction object at 0x7f85e4904390>, <octopus.arch.wasm.instruction.WasmInstruction object at 0x7f85e4904ef0>, <octopus.arch.wasm.instruction.WasmInstruction object at 0x7f85e4904f60>, <octopus.arch.wasm.instruction.WasmInstruction object at 0x7f85e4901048>]
print()
print(disasm.disassemble(r_format='reverse'))

#{0: <octopus.arch.wasm.instruction.WasmInstruction object at 0x7f85e4901048>, 1: <octopus.arch.wasm.instruction.WasmInstruction object at 0x7f85e4904240>, 2: <octopus.arch.wasm.instruction.WasmInstruction object at 0x7f85e4904f60>, 3: <octopus.arch.wasm.instruction.WasmInstruction object at 0x7f85e4904ef0>, 4: <octopus.arch.wasm.instruction.WasmInstruction object at 0x7f85e4904278>, 5: <octopus.arch.wasm.instruction.WasmInstruction object at 0x7f85e4904390>}
print()
print(disasm.disassemble(r_format='text'))
# block -1
# i32.const 24
# call 28
# i32.const 0
# return
# end

ModuleAnalyzer

from octopus.arch.wasm.analyzer import WasmModuleAnalyzer

FILE = "examples/wasm/samples/hello_wasm_studio.wasm"

with open(FILE, 'rb') as f:
    module_bytecode = f.read()

# return list of functions instructions (list)
# attributes analysis=True by default
analyzer = WasmModuleAnalyzer(module_bytecode)

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