Security Fix
ebcc17ae3c
c33457fput an address check (sovran_lan_only) on the Hub, RTL and Mempool sites. It was written for ports 80/443 being forwarded and a Host header selecting a site, and that only ever applied to the Hub. RTL and Mempool are sites on ports of their own (:3051, :60847): a request on 80/443 cannot select them, whatever Host it carries. Checked with Caddy 2.9.1 and the Caddyfile this module generates for Server + Desktop with every domain configured, serving the public sites on a stand-in port: Host: sovransystemsos.local, localhost:8937, 127.0.0.1 and x:3051 all get an empty 200, and Host: matrix.example.org gets the Synapse stand-in. With the Hub off Caddy the guard has nothing left to guard, and it could not be made right for the two sites that remain: - IPv6. A laptop's global address on the LAN looks exactly like a stranger's. The choice was between letting all of 2000::/3 through, which is the whole IPv6 internet and is whatc33457fdoes, and refusing every LAN device that connects over a global address unless the operator copies the ISP's prefix into a Nix option. - They do not need it. RTL has a random 20-character password (pwgen -s 20, about 119 bits) and, since 0.15.12, which Sovran_Bitcoin pins, a 30-minute lockout keyed on the client address. Mempool shows public chain data. If someone forwards 3051 or 60847 that is the same exposure as any other port on the machine, and SECURITY.md says not to. Remove the snippet and its two imports, and tests/test_caddy_lan_only.py with them. What is still worth pinning moves to test_hub_direct.py: no address filter anywhere in caddy.nix, the two sites are plain proxies to their loopback ports, and no option for a declared prefix is left half-wired. Behaviour change: RTL and Mempool answer any client that can reach :3051 or :60847, as they did beforec33457f. In practice that is the local network, because nothing asks you to forward those ports. Checked with the real generator and Caddy 2.9.1: Node Only generates `auto_https off` and the two plain sites and validates. Run live next to the real Hub, a LAN client gets the Hub, RTL and Mempool; a stranger's address gets RTL and Mempool (by design) and a 403 from the Hub; port 80 is not listening on Node Only.
7.4 KiB
Security Policy
Supported versions
| Release | Supported |
|---|---|
| Latest stable release | Yes |
main / staging-dev |
Development only |
Older than 1.0.0 |
No |
Install the newest stable point release to receive security fixes.
Report a vulnerability
Do not open a public issue or pull request. Report privately through:
Include the affected version, impact, reproduction steps, and a minimal proof of concept. Never send wallet recovery words, private keys, or live credentials.
We aim to acknowledge reports within two business days. Please allow reasonable time for a fix and coordinated disclosure.
Security model
Local-first operation
The Hub and core data run on operator-owned hardware. The Hub is intended for a trusted local network and must not be port-forwarded to the internet. Public services, DDNS, software updates, and optional third-party relays require external networks and are outside a “fully offline” model.
The local Hub currently uses HTTP. Authentication does not encrypt local network traffic, so use a trusted LAN and avoid public or guest Wi-Fi.
The Hub is served on port 8937, on its own: Caddy does not front it. Server +
Desktop and Bitcoin Node Only open that port in the firewall, so other devices
on your local network reach the Hub at http://sovransystemsos.local:8937.
Forwarding ports 80 and 443 for public services does not put the Hub in front of
the internet, because the only thing Caddy answers on those ports is the public
sites.
On Desktop Only the Hub is not published at all. It is reachable only from the
machine itself, through the desktop application window on localhost. Desktop
Only is the role most likely to be used away from home, and a root-capable admin
UI has no business listening on a coffee-shop network.
sovran_systemsOS.hub.directPort = true in custom.nix opens port 8937 if you
do want to reach a Desktop Only Hub from another device.
The Hub also checks every client itself, before it shows a login page. It runs
as root, so it answers only this computer and the local network (loopback,
private, VPN and link-local addresses) and turns everyone else away, however
they reached it. The Hub listens on IPv4 only, so IPv6 clients do not reach it
at all; if that ever changes, global IPv6 addresses would be turned away,
because a laptop on your network and a stranger on the internet look the same
by address alone. If your devices use addresses outside the local ranges, list
their networks in sovran_systemsOS.hub.extraLanNetworks in custom.nix;
sovran_systemsOS.hub.lanOnly = false turns the check off.
The check goes by the address a connection comes from. A router that rewrites that address when it forwards a port makes an outsider look local, so the check is a second lock and not a reason to forward port 8937: don't.
Ride The Lightning (port 3051) and Mempool (port 60847) listen on loopback only, and Caddy is how your local network reaches them. Caddy does not filter them by client address: forwarding ports 80 and 443 for public services does not reach them, because they answer on ports of their own, which nothing asks you to forward. Do not forward 3051 or 60847. If you do, Ride The Lightning still asks for its own random password and locks out repeated failures, and Mempool shows public blockchain data, but neither should face the internet.
Public services and your home IP address
Server + Desktop publishes services under your own domain. The Dynamic DNS record at Njal.la then points at your home's public IP address, which anyone can look up (domain privacy does not hide it), and ports 80 and 443 are open to the whole internet. Public HTTPS certificates also list your service hostnames in Certificate Transparency logs. Desktop publishes nothing. Node publishes nothing unless Put BTCPay Server Online or Lightning Wallet Connections is on. See Server + Desktop and your home IP address for what this means and the alternatives.
Sovran_SystemsOS does not ask a STUN server, public DNS resolver, or “what is my IP” service for your address. The DDNS update asks Njal.la to use the address the request came from, and the address Njal.la reports back is the one Element calling and the Hub use.
Bitcoin stack
Bitcoin and Lightning modules are maintained in the standalone
Sovran_Bitcoin repository
and consumed as a flake input. OS-specific customizations (Second_Drive paths,
operator user, Hub integration) are bridged by
modules/sovran-bitcoin-integration.nix. The nix-bitcoin.* option namespace
and /etc/nix-bitcoin-secrets path remain only for upgrade compatibility.
Supply chain and integrity
flake.lock pins flake inputs, and fetched source archives use fixed hashes.
Builds still depend on pinned Nixpkgs, NixVim, btc-clients-nix, upstream source
archives, and any configured binary cache. Keeping the Bitcoin modules in this
repository reduces an external dependency; it does not remove supply-chain
risk.
The Hub integrity check verifies Nix store contents and compares the running
system with a build from local /etc/nixos. It does not authenticate the release
publisher or protect against an attacker who already controls root and can
change both the system and local configuration.
Access and service isolation
- Firewall enabled by default
- Public SSH and remote desktop disabled by default
- Separate service users and systemd sandboxing where supported
- Administrative service ports bound to loopback where practical
- Tor enforced for supported Bitcoin traffic and onion services
- Public web services exposed only when enabled by the operator (this makes your home IP address public)
Tor reduces network exposure for configured Bitcoin services. It is not a guarantee against every IP leak, application bug, or traffic-analysis attack.
Restricted support access
Support uses a per-session SSH key on the non-root sovran-support account.
Sessions expire after 24 hours and have a small allowlist of sudo commands.
Wallet paths receive deny ACLs unless the operator explicitly removes them.
Disabling support removes the key and reapplies the ACLs.
Support events are written to /var/log/sovran-support-audit.log. This is a
local audit log, not a cryptographically tamper-evident record.
Out of scope
Sovran_SystemsOS cannot protect against:
- Compromised root or administrator credentials
- Stolen recovery words, private keys, or backups
- Malicious or compromised hardware, firmware, or build infrastructure
- Services the operator deliberately exposes or weakens
- Physical access without appropriate disk and firmware protections
Operator basics
- Verify downloads and stop if the checksum does not match.
- Apply stable security updates promptly.
- Use unique passwords and keep SSH/RDP off when not needed.
- Prefer a well-reviewed hardware signer for meaningful Bitcoin balances.
- Keep tested, offline backups in separate secure locations.
- Never share recovery words or private keys with support.
- Disable support access when the session ends and review the audit log.
No software can provide absolute security. Review your configuration and threat model before storing important funds or data.