It had been a while since we last upgraded our website.We had decided to outsource the website development to an external web development agency.

The website was built on wordpress, so we had to setup an sftp account for the developers to upload and edit the wordpress template.

Since we also host other websites like our api documentation on the same server as the current website, we had to ensure the external developers didnt have access to the other website files and directories.

Since we used nginx as the webserver, we used the standard web directory structure /var/www/html/ to upload the individual websites.

To restrict the users access to other directories in the system we had to setup chroot

  • First we create a the website directory
    mkdir -p /var/www/html/
  • Create a new user adding him to the www-data group.
    useradd -d /var/www/html/ -g www-data newuser
  • We need to restrict the root folder /var/www/html/ by setting the owner as root
    sudo chown root:root /var/www/html/
  • To allow the new user to write to the new directory we set the folder permission
    sudo chmod 755 /var/www/html/
  • Now we need to allow the user to connect through sftp
    We need to update the /etc/ssh/ssh_config and comment out the following line
    Subsystem sftp /usr/lib/openssh/sftp-server
    We need to add the following right after the commented line
    Subsystem sftp internal-sftp
  • Finally at the end of the file we need add the configuration to allow the user to connect
    Match User newuser
    PasswordAuthentication yes
    ForceCommand internal-sftp
    ChrootDirectory /var/www/html/
    X11Forwarding no
    AllowTcpForwarding no

    The configuration allows the user to connect via sftp.

  • sudo service ssh restart to restart the ssh deamon.

Other issues I came across

  • ssh_config is super strict about the order of the configuration. If the UsePAM config appears after the Match configuration this will result in the ssh restart error.