Security Fix
b79a6fd7f2
sshd-localhost.nix turns sshd on for every role so that "ssh root@localhost"
works, and binds it to 127.0.0.1 only ("zero network exposure", as its
own comment says, and as sshd.nix expects: the sshd feature "extends this
to 0.0.0.0 and opens port 22 on the firewall when the user enables remote
SSH").
It never turned off services.openssh.openFirewall, which NixOS defaults
to true and applies whether or not sshd listens on the ports. So port 22
was open in the firewall on every role, Desktop Only included, with
nothing behind it. No listener means no live exposure today; it does mean
the firewall was not saying what the documentation says, and the day
something does bind 22 on a wider address (a listenAddresses change, a
second daemon) it would be reachable without anyone having opened it.
openFirewall is now mkDefault false there. Nothing that wants SSH
published loses it: sshd.nix (feature sshd) and remote-deploy.nix both
add 22 explicitly, and only when enabled. Found by evaluating the real
module set; grepping for allowedTCPPorts does not see a NixOS default.
Evaluated with nix eval, TCP firewall ports:
before after
Server + Desktop 22 80 443 3051 8937 80 443 3051 8937
Bitcoin Node Only 22 3051 8937 60847 3051 8937 60847
Desktop Only 22 (none)
Desktop + features.sshd 22 22
Desktop + deploy.enable 22 3389 22 3389
and sshd's listen addresses are unchanged: 127.0.0.1 by default,
127.0.0.1 and 0.0.0.0 with the sshd feature. Desktop Only now opens no
TCP port at all; UDP 5353 (mDNS) is the only port open there, and
SECURITY.md says so.
Add tests/test_ssh_exposure.py.
159 lines
7.5 KiB
Markdown
159 lines
7.5 KiB
Markdown
# Security Policy
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## Supported versions
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| Release | Supported |
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| Latest stable release | Yes |
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| `main` / `staging-dev` | Development only |
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| Older than `1.0.0` | No |
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Install the newest stable point release to receive security fixes.
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## Report a vulnerability
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**Do not open a public issue or pull request.** Report privately through:
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- [GitHub Private Vulnerability Reporting](https://github.com/naturallaw777/Sovran_SystemsOS/security/advisories/new)
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- Email: [support@sovransystems.com](mailto:support@sovransystems.com)
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Include the affected version, impact, reproduction steps, and a minimal proof of
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concept. Never send wallet recovery words, private keys, or live credentials.
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We aim to acknowledge reports within two business days. Please allow reasonable
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time for a fix and coordinated disclosure.
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## Security model
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### Local-first operation
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The Hub and core data run on operator-owned hardware. The Hub is intended for a
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trusted local network and must not be port-forwarded to the internet. Public
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services, DDNS, software updates, and optional third-party relays require
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external networks and are outside a “fully offline” model.
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The local Hub currently uses HTTP. Authentication does not encrypt local network
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traffic, so use a trusted LAN and avoid public or guest Wi-Fi.
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The Hub is served on port 8937, on its own: Caddy does not front it. Server +
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Desktop and Bitcoin Node Only open that port in the firewall, so other devices
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on your local network reach the Hub at `http://sovransystemsos.local:8937`.
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Forwarding ports 80 and 443 for public services does not put the Hub in front of
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the internet, because the only thing Caddy answers on those ports is the public
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sites.
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On Desktop Only the Hub is not published at all. It is reachable only from the
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machine itself, through the desktop application window on localhost. Desktop
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Only is the role most likely to be used away from home, and a root-capable admin
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UI has no business listening on a coffee-shop network. The firewall there opens
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no TCP port at all; the only port open is UDP 5353, for mDNS.
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`sovran_systemsOS.hub.directPort = true` in `custom.nix` opens port 8937 if you
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do want to reach a Desktop Only Hub from another device.
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The Hub also checks every client itself, before it shows a login page. It runs
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as root, so it answers only this computer and the local network (loopback,
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private, VPN and link-local addresses) and turns everyone else away, however
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they reached it. The Hub listens on IPv4 only, so IPv6 clients do not reach it
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at all; if that ever changes, global IPv6 addresses would be turned away,
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because a laptop on your network and a stranger on the internet look the same
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by address alone. If your devices use addresses outside the local ranges, list
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their networks in `sovran_systemsOS.hub.extraLanNetworks` in `custom.nix`;
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`sovran_systemsOS.hub.lanOnly = false` turns the check off.
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The check goes by the address a connection comes from. A router that rewrites
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that address when it forwards a port makes an outsider look local, so the check
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is a second lock and not a reason to forward port 8937: don't.
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Ride The Lightning (port 3051) and Mempool (port 60847) listen on loopback only,
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and Caddy is how your local network reaches them. Caddy does not filter them by
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client address: forwarding ports 80 and 443 for public services does not reach
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them, because they answer on ports of their own, which nothing asks you to
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forward. Do not forward 3051 or 60847. If you do, Ride The Lightning still asks
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for its own random password and locks out repeated failures, and Mempool shows
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public blockchain data, but neither should face the internet.
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### Public services and your home IP address
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Server + Desktop publishes services under your own domain. The Dynamic DNS
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record at Njal.la then points at your home's public IP address, which anyone
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can look up (domain privacy does not hide it), and ports 80 and 443 are open
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to the whole internet. Public HTTPS certificates also list your service
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hostnames in Certificate Transparency logs. Desktop publishes nothing. Node
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publishes nothing unless *Put BTCPay Server Online* or *Lightning Wallet
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Connections* is on. See
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[Server + Desktop and your home IP address](README.md#server--desktop-and-your-home-ip-address)
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for what this means and the alternatives.
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Sovran_SystemsOS does not ask a STUN server, public DNS resolver, or “what is
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my IP” service for your address. The DDNS update asks Njal.la to use the
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address the request came from, and the address Njal.la reports back is the one
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Element calling and the Hub use.
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### Bitcoin stack
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Bitcoin and Lightning modules are maintained in the standalone
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[Sovran_Bitcoin](https://github.com/naturallaw777/Sovran_Bitcoin) repository
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and consumed as a flake input. OS-specific customizations (Second_Drive paths,
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operator user, Hub integration) are bridged by
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`modules/sovran-bitcoin-integration.nix`. The `nix-bitcoin.*` option namespace
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and `/etc/nix-bitcoin-secrets` path remain only for upgrade compatibility.
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### Supply chain and integrity
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`flake.lock` pins flake inputs, and fetched source archives use fixed hashes.
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Builds still depend on pinned Nixpkgs, NixVim, btc-clients-nix, upstream source
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archives, and any configured binary cache. Keeping the Bitcoin modules in this
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repository reduces an external dependency; it does not remove supply-chain
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risk.
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The Hub integrity check verifies Nix store contents and compares the running
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system with a build from local `/etc/nixos`. It does not authenticate the release
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publisher or protect against an attacker who already controls root and can
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change both the system and local configuration.
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### Access and service isolation
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- Firewall enabled by default
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- Public SSH and remote desktop disabled by default
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- Separate service users and systemd sandboxing where supported
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- Administrative service ports bound to loopback where practical
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- Tor enforced for supported Bitcoin traffic and onion services
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- Public web services exposed only when enabled by the operator (this makes
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your home IP address public)
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Tor reduces network exposure for configured Bitcoin services. It is not a
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guarantee against every IP leak, application bug, or traffic-analysis attack.
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### Restricted support access
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Support uses a per-session SSH key on the non-root `sovran-support` account.
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Sessions expire after 24 hours and have a small allowlist of `sudo` commands.
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Wallet paths receive deny ACLs unless the operator explicitly removes them.
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Disabling support removes the key and reapplies the ACLs.
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Support events are written to `/var/log/sovran-support-audit.log`. This is a
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local audit log, not a cryptographically tamper-evident record.
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## Out of scope
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Sovran_SystemsOS cannot protect against:
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- Compromised root or administrator credentials
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- Stolen recovery words, private keys, or backups
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- Malicious or compromised hardware, firmware, or build infrastructure
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- Services the operator deliberately exposes or weakens
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- Physical access without appropriate disk and firmware protections
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## Operator basics
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- Verify downloads and stop if the checksum does not match.
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- Apply stable security updates promptly.
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- Use unique passwords and keep SSH/RDP off when not needed.
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- Prefer a well-reviewed hardware signer for meaningful Bitcoin balances.
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- Keep tested, offline backups in separate secure locations.
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- Never share recovery words or private keys with support.
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- Disable support access when the session ends and review the audit log.
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No software can provide absolute security. Review your configuration and threat
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model before storing important funds or data.
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