lightning-security-module

# Lightning Security Module (Remote Signer) Set up an lnd remote signer container that holds private keys on a separate, secured machine. The signer never routes payments or opens channels — it only holds keys and signs when asked by a watch-only litd node. ## Architecture ``` Agent Machine Signer Machine (secure) ┌─────────────────┐ ┌─────────────────────┐ │ litd (watch-only)│◄──gRPC───►│ lnd (signer) │ │ - neutrino │ │ - holds seed │ │ - manages chans │ │ - signs commitments │ │ - routes pmts │ │ - signs on-chain txs │ │ - NO key material│ │ - no p2p networking │ └─────────────────┘ └─────────────────────┘ ``` The watch-only node handles all networking and channel management. The signer node holds the seed and performs cryptographic signing. Even if the agent machine is fully compromised, the attacker cannot extract private keys. See [references/architecture.md](references/architecture.md) for the full architecture explainer. ## Quick Start (Container — Recommended) ### On the Signer Machine ```bash # 1. Install lnd signer image skills/lightning-security-module/scripts/install.sh # 2. Start signer container skills/lightning-security-module/scripts/start-signer.sh # 3. Set up signer wallet and export credentials skills/lightning-security-module/scripts/setup-signer.sh # 4. Copy the credentials bundle to the agent machine # The setup script prints the bundle path and base64 string. ``` ### On the Agent Machine ```bash # 5. Import credentials bundle skills/lnd/scripts/import-credentials.sh --bundle <credentials-bundle> # 6. Start litd in watch-only mode skills/lnd/scripts/start-lnd.sh --watchonly # 7. Create watch-only wallet skills/lnd/scripts/create-wallet.sh # 8. Check status skills/lnd/scripts/lncli.sh getinfo ``` ### Two-Container Local Setup For testing both on the same machine: ```bash # Start litd + signer together skills/lnd/scripts/start-lnd.sh --watchonly # Set up signer wallet skills/lightning-security-module/scripts/setup-signer.sh --container litd-signer # Import credentials and create watch-only wallet skills/lnd/scripts/import-credentials.sh --bundle ~/.lnget/signer/credentials-bundle skills/lnd/scripts/create-wallet.sh --container litd ``` ## Installation Default: pulls the lnd Docker image for the signer. ```bash skills/lightning-security-module/scripts/install.sh ``` This pulls `lightninglabs/lnd:v0.20.0-beta` from Docker Hub. The signer only needs plain lnd (not litd) since it only holds keys and signs. ### Build from Source (Fallback) ```bash skills/lightning-security-module/scripts/install.sh --source ``` ## Native Mode For running the signer without Docker: ```bash # Set up signer natively skills/lightning-security-module/scripts/setup-signer.sh --native # Start signer natively skills/lightning-security-module/scripts/start-signer.sh --native # Stop signer natively skills/lightning-security-module/scripts/stop-signer.sh --native ``` ## Remote Nodes Export credentials from a remote signer: ```bash skills/lightning-security-module/scripts/export-credentials.sh \ --rpcserver signer-host:10012 \ --tlscertpath ~/signer-tls.cert \ --macaroonpath ~/signer-admin.macaroon ``` ## Credential Bundle Format The exported bundle (`~/.lnget/signer/credentials-bundle/`) contains: | File | Purpose | |------|---------| | `accounts.json` | Account xpubs for watch-only wallet import | | `tls.cert` | Signer's TLS certificate for authenticated gRPC | | `admin.macaroon` | Signer's admin macaroon for RPC authentication | The bundle is also available as a single base64-encoded tar.gz file (`credentials-bundle.tar.gz.b64`) for easy copy-paste transfer between machines. ## Scripts | Script | Purpose | |--------|---------| | `install.sh` | Pull lnd signer image (or build from source) | | `docker-start.sh` | Start signer container | | `docker-stop.sh` | Stop signer container | | `setup-signer.sh` | Create signer wallet and export credentials | | `start-signer.sh` | Start signer (delegates to Docker by default) | | `stop-signer.sh` | Stop signer (delegates to Docker by default) | | `export-credentials.sh` | Re-export credentials from running signer | ## Managing the Signer ### Start ```bash # Docker (default) skills/lightning-security-module/scripts/start-signer.sh # With network override skills/lightning-security-module/scripts/start-signer.sh --network mainnet ``` ### Stop ```bash # Docker stop (preserve data) skills/lightning-security-module/scripts/stop-signer.sh # Docker stop + remove volumes skills/lightning-security-module/scripts/stop-signer.sh --clean ``` ### Re-export Credentials If TLS certificates or macaroons have been regenerated: ```bash skills/lightning-security-module/scripts/export-credentials.sh ``` ## Configuration ### Container Config The signer compose template is at `skills/lightning-security-module/templates/docker-compose-signer.yml`. Config is passed via command-line arguments. ### Native Config The native signer config template is at `skills/lightning-security-module/templates/signer-lnd.conf.template`. Key differences from a standard lnd node: - **No P2P listening** (`--listen=`) — signer doesn't route - **RPC on 0.0.0.0:10012** — accepts connections from watch-only node - **REST on localhost:10013** — local only, for wallet creation - **TLS extra IP 0.0.0.0** — watch-only on a different machine can connect - **No autopilot, no routing fees** — signer is signing-only ## Security Model **What stays on the signer:** - 24-word seed mnemonic - All private keys (funding, revocation, HTLC) - Wallet database with key material **What gets exported:** - Account xpubs (public keys only — cannot spend) - TLS certificate (for authenticated connection) - Admin macaroon (for RPC auth — scope down for production) **Threat model:** - Compromised agent machine cannot sign transactions or extract keys - Attacker with agent access can see balances and channel state but not spend - Signer machine should have minimal attack surface **Production hardening:** - Replace admin macaroon with a signer-only macaroon (see `macaroon-bakery`) - Restrict signer RPC to specific IP addresses via firewall - Run signer on dedicated hardware or a hardened VM - Use Lightning Node Connect (LNC) via `lightning-mcp-server` for read-only agent access ## Macaroon Bakery for Signer For production, bake a signing-only macaroon: ```bash skills/macaroon-bakery/scripts/bake.sh --role signer-only \ --container litd-signer --rpc-port 10012 ``` Then re-export the credentials bundle with the scoped macaroon. ## Container & Ports | Container | Purpose | Ports | |-----------|---------|-------| | `litd-signer` | Remote signer (lnd) | 10012, 10013 | | Port | Service | Interface | Description | |-------|---------|-----------|-------------| | 10012 | gRPC | 0.0.0.0 | Signer RPC (watch-only connects here) | | 10013 | REST | 0.0.0.0 | REST for wallet creation | ## File Locations | Path | Purpose | |------|---------| | `~/.lnget/signer/wallet-password.txt` | Signer wallet passphrase (0600) | | `~/.lnget/signer/seed.txt` | Signer seed mnemonic (0600) | | `~/.lnget/signer/credentials-bundle/` | Exported credentials | | `~/.lnget/signer/signer-lnd.conf` | Signer config (native mode) | | `versions.env` | Pinned container image versions |