BackTunnel/README.md at fcbd6514cc6394b524eb795ff8cc524f9c5118a1

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sysadminmatmoz fcbd6514cc Add accessor key authorization and enhance completion logic

Introduce `backtunnel-authorize` for managing restricted SFTP-only keys, and update `backtunnel-share` to support temporary accessor key authorization via `--allow-key` and `--allow-known`. Extend bash completion with profile, accessor, and SSH host suggestions. Revamp README sections to include updated workflows, quick starts, and key management details.

2025-09-20 17:17:26 +02:00

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BackTunnel is a lightweight toolkit to share and mount folders between Linux machines behind NAT or firewalls using reverse SSH tunnels.
No third-party relay, no cloud dependency – just peer-to-peer, temporary, SSH-based access.

⚡ Quick Start

1. Accessor: Prepare your key (one-time)

backtunnel-keys print

Send the printed public key to the sharer.

backtunnel-share ~/Documents with alice@remotehost for 2h -i --allow-key ./alice.pub

This injects a temporary, restricted SFTP-only key and prints an invite.

3. Accessor: Mount the shared folder

backtunnel-access '/home/sharer/Documents' from alice@remotehost -p 2222 -m ~/remote-rssh

Unmount with:

fusermount -u ~/remote-rssh

✨ Features

NAT/firewall friendly: works without port forwarding.
Temporary by design: shares auto-expire after a set duration.
Invite workflow: sharer sends a one-liner or QR code to accessor.
Restricted keys: accessor keys are usable only for SFTP via the tunnel and are auto-removed when the share ends.
Profiles: save defaults and common remotes in profiles.ini.
Desktop integration: Dolphin (KDE) service menus for GUI sharing and access.

🔑 Commands

backtunnel-share /path/to/folder with user@host for <duration> [options]

-p, --tunnel-port Remote bind port (default: 2222)
-l, --local-ssh-port Local sshd port to expose (default: 22)
-i, --invite Print invite line
--qr Show QR code (requires qrencode)
--allow-key FILE Authorize a provided public key
--allow-known NAME Authorize a stored key (~/.config/backtunnel/authorized/NAME.pub)

Accessing

backtunnel-access /path/to/folder from user@host [options]

-p, --port Tunnel port (default: 2222)
-m, --mount-point Local mount point (default: ~/remote-rssh)

📁 Profiles

~/.config/backtunnel/profiles.ini:

[default]
tunnel_port=2222
invite=true
invite_mount=$HOME/remote-rssh

[work]
user=alice
host=vps.example.com
tunnel_port=4422

Usage:

backtunnel-share ~/reports with @work for 6h -i --allow-known alice

🖥️ Dolphin Integration

Share via BackTunnel… – GUI dialog for sharer options.
Access via BackTunnel… – GUI dialog for accessor options.

Logs are written to:

~/.local/state/backtunnel/servicemenu.*.log

📦 Install

From source

sudo bash scripts/install.sh
make init   # copy example profiles.ini

Arch Linux

makepkg -si

Uninstall:

sudo bash scripts/uninstall.sh
# or with purge of defaults
sudo PURGE=1 bash scripts/uninstall.sh

📖 Documentation

man backtunnel

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BackTunnel – Secure Reverse SSH Folder Sharing Toolkit