Setup SFTP for a user to access restricted folder only on Ubuntu 14.04

Today I need to give my friend access to my server, so he can edit any files in that folder. My server is running OpenSSH and SFTP is enabled by default, actually I can create a new Linux user for him to access with SFTP. But I just want he accessing to the folder I gave him, so here I modify OpenSSH configuration to fit my need.

System details:

• Ubuntu 14.04
• Running OpenSSH

Steps:

1. Add a group called sftp.

   sudo addgroup sftp

2. Add new user with default home path, assign to sftp group and disable shell access.

   sudo useradd -m -g sftp -s /bin/false username

3. Give a new password for the user.

   sudo passwd username

4. Change home directory’s user and group to root.

   sudo chown root:root /home/username

5. Change home directory’s permission

   sudo chmod 755 /home/username

6. Go into the folder

   cd /home/username

7. Create a new folder named www.

   sudo mkdir www

8. Change www folder’s user and group to username.

   sudo chown username:username www

9. This step is the core. Edit to /etc/ssh/sshd_config with the editor you used to.

   sudo nano /etc/ssh/sshd_config

10. Add following lines to the end of  /etc/ssh/sshd_config.

    Match group sftp
    	ChrootDirectory %h
    	X11Forwarding no
    	AllowTcpForwarding no
    	ForceCommand internal-sftp
    	# PasswordAuthentication yes

    Enable PasswordAuthentication by uncomment it if you enabled PubkeyAuthentication for other users in sshd_config.

11. Restart ssh service. Done.

    sudo /etc/init.d/ssh restart