ssh-socks-cli 0.1.0

Cross-platform CLI that manages an SSH-based SOCKS5 tunnel so Firefox can bypass corporate VPNs (GlobalProtect, AnyConnect, Zscaler, ...)

ssh-socks-cli

Route Firefox traffic around your corporate VPN via an SSH SOCKS5 tunnel — without wrestling with ssh -D, autossh flags, or Firefox's proxy pane.

What problem does this solve?

You work on a corporate laptop with an always-on VPN — Palo Alto GlobalProtect, Cisco AnyConnect, Zscaler, or similar. Your employer routes every byte of traffic through their gateway, and you'd rather keep personal browsing (webmail, banking, social media, geo-restricted streaming) outside that tunnel. Or you're testing a service as an external user from the same machine. Or you just want separation between work and personal contexts.

The traditional workaround is:

1. SSH into a personal VPS or home server with ssh -D 1080 user@host
2. Open Firefox's network settings and manually configure SOCKS5 on 127.0.0.1:1080
3. Remember to enable "Proxy DNS when using SOCKS v5" (or leak your DNS through the corporate resolver)
4. Do it all over again every time you reboot

ssh-socks-cli automates all of that in one CLI.

⚠️ You need an SSH exit server

This tool is useless without one. ssh-socks-cli is a client — it manages the connection from your laptop to an SSH server you already own, and tunnels Firefox traffic through it. The server is the part that actually exits to the internet on your behalf. Your Firefox's public IP becomes whatever that server's public IP is.

Any of the following works, as long as it runs sshd and is reachable from your laptop:

• A VPS (DigitalOcean, Hetzner, Linode, OVH, Vultr, AWS Lightsail, Fly.io, …). $3–6/month is plenty. Most reliable option, works from anywhere you have internet.
• A Raspberry Pi running 24/7 at home. Requires your router to port-forward SSH (and ideally a dynamic-DNS service like DuckDNS or Cloudflare Tunnel if your ISP doesn't give you a static IP). An RPi Zero 2W is enough — this workload is tiny.
• A home server / NAS with SSH exposed (Synology, Unraid, TrueNAS, …).
• An old laptop or mini-PC left plugged in at home running Linux.
• A friend's server where you have an account — only if you trust them, because all your Firefox traffic will exit from there.

What the server needs:

• sshd running and reachable on some port (22 or custom).
• Your SSH public key in ~/.ssh/authorized_keys for the user you'll connect as.
• Outbound internet access.
• That's it. No extra software, no SOCKS5 daemon — OpenSSH's -D flag is a SOCKS5 server, built in.

What the server does NOT need:

• A public static IP (dynamic DNS works).
• A SOCKS5 server, Shadowsocks, V2Ray, or anything like that.
• Significant resources. An RPi Zero 2W or a $3/month VPS handles this trivially.

Before running ssh-socks init, verify you can already SSH in manually:

ssh [e-mail]
# If that works, you're ready. If it doesn't, fix your SSH access first —
# ssh-socks-cli cannot help you debug an unreachable server.

How it works

Before — corporate VPN captures everything

flowchart LR
    subgraph laptop["💻 Corporate laptop"]
        FF["Firefox"]
        Other["Chrome / Slack /<br/>Outlook / git / ..."]
    end
    VPN["🛡️ Corporate VPN<br/>(GlobalProtect / AnyConnect / Zscaler)"]
    Net["🌐 Internet"]

    FF --> VPN
    Other --> VPN
    VPN -->|"logs + DNS<br/>+ filters"| Net

Every byte your laptop sends goes through the corporate gateway. Your employer sees all DNS lookups, can block content, and logs connections.

After — Firefox exits through your own server

flowchart LR
    subgraph laptop["💻 Corporate laptop"]
        FF["Firefox"]
        CLI["ssh-socks-cli<br/>(autossh)<br/>127.0.0.1:1080"]
        Other["Chrome / Slack /<br/>Outlook / git / ..."]
    end
    VPS["🖥️ Your SSH server<br/>(VPS / RPi / home server)"]
    VPN["🛡️ Corporate VPN"]
    Personal["🌐 Personal internet"]
    Corp["🏢 Corporate resources"]

    FF -->|"SOCKS5"| CLI
    CLI ==>|"encrypted<br/>SSH tunnel"| VPS
    VPS --> Personal
    Other --> VPN
    VPN --> Corp

    style CLI fill:#2d5f2d,color:#fff,stroke:#4caf50
    style VPS fill:#1a3a5c,color:#fff,stroke:#2196f3

Only Firefox is re-routed. Every other app (Chrome, Slack, Outlook, git, your IDE) keeps using the corporate VPN exactly as before. The corporate VPN is not bypassed for those — this is a split-tunnel, not a full bypass.

What happens on a single Firefox request

sequenceDiagram
    autonumber
    participant FF as Firefox
    participant Tun as ssh-socks-cli<br/>(local SOCKS5<br/>127.0.0.1:1080)
    participant VPS as Your SSH server
    participant Site as reddit.com

    FF->>Tun: SOCKS5: connect to<br/>"reddit.com:443"<br/>(hostname, not IP)
    Note over Tun: Tunneled inside the<br/>encrypted SSH connection
    Tun->>VPS: forwarded SOCKS5 request
    VPS->>VPS: DNS resolve "reddit.com"<br/>(using VPS's resolver,<br/>NOT corporate DNS)
    VPS->>Site: TCP connect to<br/>151.101.1.140:443
    Site-->>VPS: TLS handshake
    VPS-->>Tun: bytes over SSH
    Tun-->>FF: bytes over SOCKS5
    Note over Site: Sees your VPS's IP,<br/>not your laptop's

Key point: the hostname is resolved at the VPS, not at your laptop. That's what network.proxy.socks_remote_dns = true buys you — without it, Firefox would ask the local OS resolver (= corporate DNS pushed by GlobalProtect) before sending the request through the tunnel, leaking every domain you visit to your employer.

Features

• One-command tunnel lifecycle — start, stop, status, restart, logs
• Firefox integration — writes the correct user.js preferences with DNS-leak protection and WebRTC hardening, automatically detecting your default profile
• Auto-reconnect via autossh when available, falling back to plain ssh with aggressive keep-alives
• doctor command — diagnoses missing binaries, key file permissions, host reachability, and best-effort corporate VPN detection
• XDG-compliant config — lives at ~/.config/ssh-socks-cli/config.toml (Linux/macOS) or %APPDATA%\ssh-socks-cli\ (Windows)
• Zero heavy dependencies — no paramiko, no cryptography. Shells out to system ssh/autossh
• Cross-platform — macOS, Linux, Windows (native OpenSSH client)

Prerequisites

On your laptop:

• Python 3.11+
• ssh (OpenSSH client) — any modern macOS, Linux, or Windows 10/11 already has it
• autossh (optional but strongly recommended) — for automatic reconnection when your network flaps
  • macOS: brew install autossh
  • Debian/Ubuntu: sudo apt install autossh
  • Fedora/RHEL: sudo dnf install autossh
  • Arch: sudo pacman -S autossh
• Firefox (obviously) — other browsers are out of scope for v0.1

On your exit server: see the SSH exit server section above. TL;DR: anything running sshd that you can SSH into manually — a VPS, a Raspberry Pi at home, a NAS, whatever.

Installation

pip install ssh-socks-cli

Or from source:

git clone https://github.com/sergioarojasm98/ssh-socks-cli.git
cd ssh-socks-cli
pip install -e .

Quick start

# 1. Interactive setup — writes ~/.config/ssh-socks-cli/config.toml
ssh-socks init

# 2. Verify your environment is ready
ssh-socks doctor

# 3. Start the tunnel in the background
ssh-socks start

# 4. Configure Firefox to use it (detects default profile automatically)
ssh-socks firefox apply

# 5. Restart Firefox — done. Your Firefox traffic now exits from your SSH server.

To verify it's working, visit a site like https://ifconfig.me in Firefox. The IP should match your SSH server, not your corporate gateway.

Command reference

Command	Description
ssh-socks init	Interactively create the config file
ssh-socks start	Start the SOCKS5 tunnel in the background
ssh-socks stop	Stop the running tunnel
ssh-socks restart	Stop + start
ssh-socks status	Show tunnel status (running/stopped, PID, endpoint)
ssh-socks logs [-f] [-n N]	Show tunnel log (tail or follow)
ssh-socks doctor	Run environment diagnostics
ssh-socks config show	Print current configuration
ssh-socks config path	Print config file path
ssh-socks firefox show	Print the user.js block to stdout
ssh-socks firefox apply	Inject the block into the default profile's user.js
ssh-socks firefox reset	Replace the apply block with a defaults-restoring block
ssh-socks firefox purge	Remove any ssh-socks-cli block from user.js entirely
ssh-socks firefox profiles	List detected Firefox profiles
ssh-socks --version	Show version

Configuration file

Example ~/.config/ssh-socks-cli/config.toml:

[tunnel]
host = "proxy.example.com"
user = "sergio"
port = 22
identity_file = "~/.ssh/id_ed25519"
local_port = 1080
bind_address = "127.0.0.1"
compression = true
server_alive_interval = 30
server_alive_count_max = 3
connect_timeout = 10
strict_host_key_checking = "accept-new"
# use_autossh = true   # omit to auto-detect

[firefox]
proxy_dns = true       # critical: prevents DNS leaks through corporate DNS
bypass_list = "localhost, 127.0.0.1"
disable_webrtc = true  # WebRTC can leak your real IP even through SOCKS5

What does the Firefox block actually do?

ssh-socks firefox apply injects a clearly-delimited block into your profile's user.js:

// BEGIN ssh-socks-cli managed block (do not edit manually)
user_pref("network.proxy.type", 1);
user_pref("network.proxy.socks", "127.0.0.1");
user_pref("network.proxy.socks_port", 1080);
user_pref("network.proxy.socks_version", 5);

// DNS leak prevention (both old and Firefox-128+ pref names)
user_pref("network.proxy.socks_remote_dns", true);
user_pref("network.proxy.socks5_remote_dns", true);
user_pref("network.dns.disablePrefetch", true);
user_pref("network.dns.disablePrefetchFromHTTPS", true);

// Force proxy, never fall back to direct (which would leak via the VPN)
user_pref("network.proxy.failover_direct", false);
user_pref("network.proxy.allow_bypass", false);

// Disable DoH (TRR) — would race the SOCKS tunnel and leak DNS
user_pref("network.trr.mode", 5);

// Disable speculative connections / prefetch (they bypass the proxy)
user_pref("network.http.speculative-parallel-limit", 0);
user_pref("network.predictor.enabled", false);
user_pref("network.prefetch-next", false);

// Disable captive portal / connectivity probes that hit Mozilla directly
user_pref("network.captive-portal-service.enabled", false);
user_pref("network.connectivity-service.enabled", false);

// WebRTC leak prevention
user_pref("media.peerconnection.enabled", false);
// END ssh-socks-cli managed block

Each block is there for a reason:

Pref	Why
network.proxy.type=1	Enable manual proxy mode
network.proxy.socks*	Point Firefox at 127.0.0.1:1080 as SOCKS v5
network.proxy.socks_remote_dns + socks5_remote_dns	Critical — DNS resolution happens at the SSH server, not through your corporate resolver. Firefox 128 introduced a new pref name; we set both.
network.trr.mode=5	Critical — disable DNS-over-HTTPS. Otherwise Firefox would race TRR against the SOCKS tunnel and leak DNS.
network.proxy.failover_direct=false + allow_bypass=false	If the tunnel drops, Firefox will NOT silently fall back to direct (i.e., the VPN).
network.http.speculative-parallel-limit=0, predictor.enabled=false, prefetch-next=false	Firefox opens speculative TCP connections before the proxy is consulted; disable them.
network.captive-portal-service.enabled=false	Firefox pings detectportal.firefox.com directly on startup, bypassing the proxy.
media.peerconnection.enabled=false	WebRTC can bypass the SOCKS proxy and leak your real LAN IP.

Reverting Firefox changes (two-step)

Firefox copies user_pref values into prefs.js at shutdown, so simply deleting the apply block from user.js is not enough to undo the previous session's changes. The rollback is therefore a two-step operation:

1. ssh-socks firefox reset — replaces the apply block with a defaults-restoring block that sets every touched pref back to its Firefox factory value. Restart Firefox once. On that restart, Firefox overwrites prefs.js with the defaults.
2. ssh-socks firefox purge — removes the block from user.js entirely, leaving the rest of your prefs intact.

Your existing user.js is backed up to user.js.sshsocks-backup-<timestamp> before every write.

Security notes

• This is not a VPN. It's a SOCKS5 proxy for Firefox only. Other apps on your machine still use the corporate VPN unless you configure them separately.
• You control the exit server. All Firefox traffic goes through your SSH host. Pick a host you trust.
• Corporate policy. Check whether your employer permits split-tunneling. This tool does not try to hide its existence — if your company runs DLP/EDR, they can likely see that you have an SSH session open. Use at your own discretion.
• Key file permissions. ssh-socks doctor will warn you if your private key has loose permissions. Fix with chmod 600 ~/.ssh/id_ed25519.
• Host key checking. Defaults to accept-new (TOFU on first connect, strict thereafter). You can tighten this in the config.

Troubleshooting

ssh-socks start exits immediately. Run ssh-socks logs — the SSH error is captured verbatim. The most common causes are wrong host/user, bad key, or the local port already in use.

Firefox still uses the corporate VPN.

1. Did you actually restart Firefox after ssh-socks firefox apply? user.js is only read on startup.
2. Go to about:preferences#general → Network Settings. It should show "Manual proxy configuration" with SOCKS host 127.0.0.1 and port 1080.
3. Visit about:config and search network.proxy.socks — confirm the values are what you expect.

DNS still resolves through my company. Confirm network.proxy.socks_remote_dns is true in about:config. Visit https://dnsleaktest.com in Firefox to confirm.

The tunnel drops every few minutes. Install autossh — it will automatically reconnect. Check ssh-socks doctor to confirm it was picked up.

Comparison with alternatives

Option	Pros	Cons
Manual ssh -D 1080	Zero install	Forget on reboot, no status, no Firefox help, no auto-reconnect
FoxyProxy extension	Rich per-URL routing	You still need to run the SSH tunnel yourself
ssh-socks-cli	Tunnel lifecycle + Firefox config + doctor in one tool	You need an SSH server
Commercial VPN	Any browser, any traffic	Monthly cost, another company in your traffic path

Development

git clone https://github.com/sergioarojasm98/ssh-socks-cli.git
cd ssh-socks-cli
pip install -e ".[dev]"
pytest
ruff check .
mypy src

License

MIT — see LICENSE.

Author

Built by Sergio Rojas — Senior Technical & AI Ops Engineer who got tired of typing ssh -D 1080 every morning.