This article explains how to restrict sFTP with Chroot on Ubuntu Linux.
Configuring the sFTP protocol allows for a more secure transfer of files between the SFTP host and client machines. An even more secure implementation will be to enable chroot. A chroot isolates applications from the rest of your computer by putting them in jail.
The reason to restrict SFTP with Chroot on Ubuntu Linux is to enhance file transfer security between server and client machines. FTP is inherently insecure, so SFTP is a more secure option for file transfer.
However, enabling chroot on top of SFTP adds an extra layer of security. Chroot isolates the user’s account and restricts access to only their directory and files within the directory.
This ensures that users can only access what they are authorized to and nothing else on the system.
To get started, continue with the steps below
Install Open SSH Server
If you haven’t installed the Open SSH server, run the commands below to install it.
sudo apt update sudo apt install openssh-server
After installing, the commands below can stop, start, and enable the service to start when the server boots.
sudo systemctl stop ssh.service sudo systemctl start ssh.service sudo systemctl enable ssh.service
Configure SFTP
Now that OpenSSH Server is installed open its default configuration file by running the commands below.
sudo nano /etc/ssh/sshd_config
Then, edit the file and change the highlighted line below. Add the # before the first line, then add the highlighted line below to enable SFTP. This will change the subsystem to internal-sftp only.
# override default of no subsystems #Subsystem sftp /usr/lib/openssh/sftp-server Subsystem sftp internal-sftp
Next, add the lines below at the end of the file or just below the highlighted line above.
# Example of overriding settings on a per-user basis
#Match User anoncvs
# X11Forwarding no
# AllowTcpForwarding no
# PermitTTY no
# ForceCommand cvs server
Match Group sftp_users
X11Forwarding no
AllowTcpForwarding no
ChrootDirectory /home
ForceCommand internal-sftp
Save the file and exit.
After editing the file, run the commands below to restart OpenSSH Server.
sudo systemctl restart ssh.service
Create SFTP Group
Now that you have defined your SFTP settings and set them to match the sftp_users. Create a sftp_users group, then add users you want to restrict via chroot. To create the group, run the commands below.
sudo groupadd sftp_users
Now, add any user to the group by running the commands below.
sudo usermod -aG sftp_users richard
Replace user richard with your Ubuntu account name. This will add the user to the sftp_users group you created above.
That’s it! Your system should be configured for secure SFTP for your users.
Users can securely use their favorite FTP client, Filezilla, to connect to the server via SFTP protocol. Users will be restricted to their directories and nowhere else.
Make sure to select SFTP connection in Filezilla.
When you connect, you’ll be prompted to accept the server key. Accept it and continue.
Connect and use the SFTP service.
Enjoy!
Leave a Reply to Student Cancel reply