fcn

free connect your private network from anywhere

1. What is fcn

fcn[free connect] is a foolproof one-click tool for accessing private networks, consisting of the server side and the client side

fcn uses fcn public data servers and data encryption technology to virtually connect user clients to the server's private network

fcn = fcn_server + fcn_client

Note: Versions prior to FCN V3.0 have a BUG when switching servers. FCN recently changed server IPs, which may cause failure to connect to the server. Please restart the server or update the server version

• FCN QQ discussion group: 592512533 FCN forum http://bbs.xfconnect.com

• download FCN V3.0 FULL Baidu Netdisk https://pan.baidu.com/s/1pLsonhh

• download FCN V3.0 binary https://github.com/boywhp/fcn/releases/download/V3.0/FCN_V3.0.zip

• download FCN V3.0 embedded version https://github.com/boywhp/fcn/releases/download/V3.0/linux-embeded.zip

• FCN supported operating system platforms

Tested and verified on Linux openwrt/lede WR703N, Asus N14U, Phicomm K2/K2P Openwrt/Padavan; openwrt/lede requires manual installation of the libopenssl package

Tested and verified on Linux arm/armbian Raspberry Pi 3, Orange Pi

• fcn access principle diagram

• fcn access Phicomm PSG1218/K2 router operation demo

2. Common fcn use cases

FCN's design philosophy is to provide a complete network access solution with the simplest interface operations. See the PPT for use case introductions

http://pan.baidu.com/s/1o8r2w7g

FCN Lan2Lan introduction

http://weibo.com/ttarticle/p/show?id=2309404124768579250283

3. Using fcn

3.1 Running the server

First configure the fcn.conf configuration file. Note that the current test accounts are FCN_0000-FCN_9999, each account is rate-limited to 100KB/s [no limit once peer-to-peer communication succeeds]

Please randomly pick a test account and set your own unique server name to prevent account conflicts

tun driver mode NAT requires ROOT privileges to run; in application-layer NAT mode, ping packets cannot be sent or received without ROOT privileges

./fcn_x64     # 应用层NAT模式
sudo ./fcn_x64    # tun驱动NAT模式

Note: The FCN server can only run one instance per configuration. After changing the configuration, you need to kill the old process, otherwise an error will be reported

3.2 Auto-start on boot [Thanks to 榭寄生], debian linux environment

• Create a startup script fcn.sh with the following content:

#!/bin/sh
/home/pi/fcn-arm

• Add execute permission: chmod +x fcn.sh

• Create a symbolic link: ln -s /home/pi/your_fcn_dir/fcn.sh /etc/init.d/fcn

• Add to auto-start: update-rc.d fcn defaults 99

3.3 Running the windows client

Add a server on the main interface, fill in the corresponding connection parameters, and connect. Once successful, the windows client is connected to the server's corresponding LAN. The client/server parameter correspondence is as follows

Note: The virtual NIC driver will be installed automatically on first connection, and user confirmation is required

3.4 Running the Linux client

The Linux client and server functions are integrated into the same executable. The program decides whether to start client or server functions via command-line arguments. The most common client parameters are as follows:

sudo ./fcn --uid FCN_0001 --svr SVR0001 --psk 'PASSWORD'

The Linux command-line client supports the following parameters:

4. Is fcn secure?

fcn uses digital certificates, TLS and data encryption technology, and peer-to-peer communication technology. User network data is encrypted throughout the entire session, and the session key is automatically updated every 30 minutes or so, ensuring that user data cannot be intercepted, decrypted, or subjected to man-in-the-middle attacks.

fcn public servers do not collect any user network data and also support forced peer-to-peer communication of user network data. In the future, we plan to open user encryption interfaces so that users can implement custom end-to-end private encryption.

4.1 fcn security mechanisms

• Mutual TLS certificate authentication between the fcn public server and fcn client ensures channel security
• The fcn user server requests a random number from the fcn public server every 30 minutes
• The fcn public server generates random numbers using a true random number generator and securely delivers them to users over a TLS connection
• The fcn client/server computes a session key from the random code + UID + PSK
• The fcn client/server uses the session key to aes256-encrypt communication data packets for the entire session