Tutorial

How To Set Up vsftpd for a User's Directory on Ubuntu 20.04

Linux BasicsUbuntuSecurityUbuntu 20.04
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Introduction

FTP, which is short for File Transfer Protocol, is a network protocol that was once widely used for moving files between a client and server. FTP is still used to support legacy applications and workflows with very specific needs. If you have a choice on protocol, consider modern options that are more efficient, secure, and convenient for delivering files. For example, Internet users who download directly from their web browser with https, and command line users who use secure protocols such as the scp or SFTP.

vsftpd, very secure FTP daemon, is an FTP server for many Unix-like systems, including Linux, and is often the default FTP server for many Linux distributions as well. vsftpd is beneficial for optimizing security, performance, and stability. It also provides strong protection against security problems found in other FTP servers. vsftpd can handle virtual IPD configurations, encryption support with SSL integration, and more.

In this tutorial, you’ll configure vsftpd to allow a user to upload files to their home directory using FTP with login credentials secured by SSL/TLS. You’ll also connect your server using FileZilla, an open-source FTP client, to test the TLS encryption.

Prerequisites

To follow along with this tutorial you will need:

  • The first thing you need is an Ubuntu 20.04 server, a non-root user with sudo privileges, and an enabled firewall. You can learn more about how to do this in our Initial Server Setup with Ubuntu 20.04 guide.

  • The second thing you need is FileZilla, an open-source FTP client, installed and configured on your local machine. This will allow you to test whether the client can connect to your server over TLS. You can find instructions for installing FileZilla on Debian and Ubuntu systems from this tutorial, along with links to instructions for installing it on other systems.

Step 1 — Installing vsftpd

Start by updating your package list:

  • sudo apt update

Next, install the vsftpd daemon:

  • sudo apt install vsftpd

When the installation is complete, copy the configuration file so you can start with a blank configuration, while also saving the original as a backup:

  • sudo cp /etc/vsftpd.conf /etc/vsftpd.conf.orig

With a backup of the configuration in place, you’re ready to configure the firewall.

Step 2 — Opening the Firewall

First, check the firewall status to see if it’s enabled. If it is, then you’ll make adjustments to ensure that FTP traffic is permitted so firewall rules don’t block the tests.

Check the firewall status:

  • sudo ufw status

This output reveals that the firewall is active and only SSH is allowed through:

Output
Status: active To Action From -- ------ ---- OpenSSH ALLOW Anywhere OpenSSH (v6) ALLOW Anywhere (v6)

You may have other rules in place or no firewall rules at all. Since only SSH traffic is permitted, you’ll need to add rules for FTP traffic.

Start by opening ports 20, 21, and 990 so they’re ready when you enable TLS:

  • sudo ufw allow 20,21,990/tcp

Next, open ports 40000-50000 for the range of passive ports you will be setting in the configuration file:

  • sudo ufw allow 40000:50000/tcp

Check the status of your firewall:

  • sudo ufw status

The output of your firewall rules should now appear as the following:

Output
Status: active To Action From -- ------ ---- OpenSSH ALLOW Anywhere 20,21,990/tcp ALLOW Anywhere 40000:50000/tcp ALLOW Anywhere OpenSSH (v6) ALLOW Anywhere (v6) 20,21,990/tcp (v6) ALLOW Anywhere (v6) 40000:50000/tcp (v6) ALLOW Anywhere (v6)

With vsftpd installed and the necessary ports open, now it’s time to create a dedicated FTP user.

Step 3 — Preparing the User Directory

In this step, you will create a dedicated FTP user. However, you may already have a user in need of FTP access. This guide outlines how to preserve an existing user’s access to their data, but, even so, we recommend that you start with a new dedicated FTP user until you’ve configured and tested your setup before reconfiguring any existing users.

Start by adding a test user:

  • sudo adduser sammy

Assign a password when prompted. Feel free to press ENTER to skip through the following prompts, as those details aren’t important for the purposes of this step.

FTP is generally more secure when users are restricted to a specific directory. vsftpd accomplishes this with chroot jails. When chroot is enabled for local users, they are restricted to their home directory by default. Since vsftpd secures the directory in a specific way, it must not be writable by the user. This is fine for a new user who should only connect via FTP, but an existing user may need to write to their home folder if they also have shell access.

In this example, rather than removing write privileges from the home directory, create an ftp directory to serve as the chroot and a writable files directory to hold the actual files.

Create the ftp folder:

  • sudo mkdir /home/sammy/ftp

Set its ownership:

  • sudo chown nobody:nogroup /home/sammy/ftp

Remove write permissions:

  • sudo chmod a-w /home/sammy/ftp

Verify the permissions:

  • sudo ls -la /home/sammy/ftp
Output
total 8 dr-xr-xr-x 2 nobody nogroup 4096 Sep 14 20:28 . drwxr-xr-x 3 sammy sammy 4096 Sep 14 20:28 ..

Next, create the directory for file uploads:

  • sudo mkdir /home/sammy/ftp/files

Then assign ownership to the user:

  • sudo chown sammy:sammy /home/sammy/ftp/files

A permissions check on the ftp directory should return the following output:

  • sudo ls -la /home/sammy/ftp
Output
total 12 dr-xr-xr-x 3 nobody nogroup 4096 Sep 14 20:30 . drwxr-xr-x 3 sammy sammy 4096 Sep 14 20:28 .. drwxr-xr-x 2 sammy sammy 4096 Sep 14 20:30 files

Finally, add a test.txt file to use for testing:

  • echo "vsftpd test file" | sudo tee /home/sammy/ftp/files/test.txt
Output
vsftpd test file

Now that you’ve secured the ftp directory and allowed the user access to the files directory, next you will modify our configuration.

Step 4 — Configuring FTP Access

In this step, you will allow a single user with a local shell account to connect with FTP. The two key settings for this are already set in vsftpd.conf. Open this file using your preferred text editor. Here, we’ll use nano:

  • sudo nano /etc/vsftpd.conf

Once you’ve opened the file, confirm that the anonymous_enable directive is set to NO and the local_enable directive is set to YES:

/etc/vsftpd.conf
. . .
# Allow anonymous FTP? (Disabled by default).
anonymous_enable=NO
#
# Uncomment this to allow local users to log in.
local_enable=YES
. . .

These settings prevent anonymous logins and permit local logins, respectively. Keep in mind that enabling local logins means that any normal user listed in the /etc/passwd file can be used to log in.

Some FTP commands allow users to add, change, or remove files and directories on the filesystem. Enable these commands by uncommenting the write_enable setting. You can do this by removing the pound sign (#) preceding this directive:

/etc/vsftpd.conf
. . .
write_enable=YES
. . .

Uncomment the chroot to prevent the FTP-connected user from accessing any files or commands outside the directory tree:

/etc/vsftpd.conf
. . .
chroot_local_user=YES
. . .

Next, add a user_sub_token directive whose value is the $USER environment variable. Then add a local_root directive and set it to the path shown, which also includes the $USER environment variable. This setup ensures that the configuration will allow for this user and future users to be routed to the appropriate user’s home directory when logging in. Add these settings anywhere in the file:

/etc/vsftpd.conf
. . .
user_sub_token=$USER
local_root=/home/$USER/ftp

Limit the range of ports that can be used for passive FTP to ensure enough connections are available:

/etc/vsftpd.conf
. . .
pasv_min_port=40000
pasv_max_port=50000

Note: In Step 2, you opened the ports that are set here for the passive port range. If you change these values, be sure to update your firewall settings.

To allow FTP access on a case-by-case basis, set the configuration so that users have access only when they are explicitly added to a list, rather than by default:

/etc/vsftpd.conf
. . .
userlist_enable=YES
userlist_file=/etc/vsftpd.userlist
userlist_deny=NO

userlist_deny toggles the logic: when it is set to YES, users on the list are denied FTP access; when it is set to NO, only users on the list are allowed access.

When you’re done making the changes, save the file and exit the editor. If you used nano to edit the file, you can do so by pressing CTRL + X, Y, then ENTER.

Finally, add your user to /etc/vsftpd.userlist. Use the -a flag to append to the file:

  • echo "sammy" | sudo tee -a /etc/vsftpd.userlist

Check that it was added as you expected:

  • cat /etc/vsftpd.userlist
Output
sammy

Restart the daemon to load the configuration changes:

  • sudo systemctl restart vsftpd

With the configuration in place, now you can test FTP access.

Step 5 — Testing FTP Access

We’ve configured the server to allow only the user sammy to connect via FTP. Now we will make sure that this works as expected.

Since you’ve disabled anonymous access, you can test it by trying to connect anonymously. If the configuration is set up properly, anonymous users should be denied permission. Open another terminal window and run the following command. Be sure to replace 203.0.113.0 with your server’s public IP address:

  • ftp -p 203.0.113.0

When prompted for a username, try logging in as a nonexistent user such as anonymous and you will receive the following output:

Output
Connected to 203.0.113.0. 220 (vsFTPd 3.0.3) Name (203.0.113.0:default): anonymous 530 Permission denied. ftp: Login failed. ftp>

Close the connection:

  • bye

Users other than sammy should also fail to connect. Try connecting as your sudo user. They should also be denied access, and it should happen before they’re allowed to enter their password:

  • ftp -p 203.0.113.0
Output
Connected to 203.0.113.0. 220 (vsFTPd 3.0.3) Name (203.0.113.0:default): sudo_user 530 Permission denied. ftp: Login failed. ftp>

Close the connection:

  • bye

The user sammy, on the other hand, should be able to connect, read, and write files. Make sure that your designated FTP user can connect:

  • ftp -p 203.0.113.0
Output
Connected to 203.0.113.0. 220 (vsFTPd 3.0.3) Name (203.0.113.0:default): sammy 331 Please specify the password. Password: your_user's_password 230 Login successful. Remote system type is UNIX. Using binary mode to transfer files. ftp>

Now change into the files directory:

  • cd files
Output
250 Directory successfully changed.

Next, run get to transfer the test file you created earlier to your local machine:

  • get test.txt
Output
227 Entering Passive Mode (203,0,113,0,169,12). 150 Opening BINARY mode data connection for test.txt (17 bytes). 226 Transfer complete. 17 bytes received in 0.00 secs (4.5496 kB/s) ftp>

Next, upload the file with a new name to test write permissions:

  • put test.txt upload.txt
Output
227 Entering Passive Mode (203,0,113,0,164,71). 150 Ok to send data. 226 Transfer complete. 17 bytes sent in 0.00 secs (5.3227 kB/s)

Close the connection:

  • bye

Now that you’ve tested your configuration, next you’ll take steps to further secure your server.

Step 6 — Securing Transactions

Since FTP does not encrypt any data in transit, including user credentials, you can enable TLS/SSL to provide that encryption. The first step is to create the SSL certificates for use with vsftpd.

Use openssl to create a new certificate and use the -days flag to make it valid for one year. In the same command, add a private 2048-bit RSA key. By setting both the -keyout and -out flags to the same value, the private key and the certificate will be located in the same file:

  • sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /etc/ssl/private/vsftpd.pem -out /etc/ssl/private/vsftpd.pem

You’ll be prompted to provide address information for your certificate. Substitute your own information for the highlighted values:

Output
Generating a 2048 bit RSA private key ............................................................................+++ ...........+++ writing new private key to '/etc/ssl/private/vsftpd.pem' ----- You are about to be asked to enter information that will be incorporated into your certificate request. What you are about to enter is what is called a Distinguished Name or a DN. There are quite a few fields but you can leave some blank For some fields there will be a default value, If you enter '.', the field will be left blank. ----- Country Name (2 letter code) [AU]:US State or Province Name (full name) [Some-State]:NY Locality Name (eg, city) []:New York City Organization Name (eg, company) [Internet Widgits Pty Ltd]:DigitalOcean Organizational Unit Name (eg, section) []: Common Name (e.g. server FQDN or YOUR name) []: your_server_ip Email Address []:

For more detailed information about the certificate flags, read OpenSSL Essentials: Working with SSL Certificates, Private Keys and CSRs.

Once you’ve created the certificates, open the vsftpd configuration file again:

  • sudo nano /etc/vsftpd.conf

Toward the bottom of the file, there will be two lines that begin with rsa_. Comment them out by preceding each line with a pound sign (#):

/etc/vsftpd.conf
. . .
# rsa_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
# rsa_private_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
. . .

After those lines, add the following lines that point to the certificate and private key you created:

/etc/vsftpd.conf
. . .
rsa_cert_file=/etc/ssl/private/vsftpd.pem
rsa_private_key_file=/etc/ssl/private/vsftpd.pem
. . .

Now you will force the use of SSL, which will prevent clients that can’t handle TLS from connecting. This is necessary to ensure that all traffic is encrypted, but it may force your FTP user to change clients. Change ssl_enable to YES:

/etc/vsftpd.conf
. . .
ssl_enable=YES
. . .

Next, add the following lines to explicitly deny anonymous connections over SSL and require SSL for both data transfer and logins:

/etc/vsftpd.conf
. . .
allow_anon_ssl=NO
force_local_data_ssl=YES
force_local_logins_ssl=YES
. . .

Then configure the server to use TLS, the preferred successor to SSL, by adding the following lines:

/etc/vsftpd.conf
. . .
ssl_tlsv1=YES
ssl_sslv2=NO
ssl_sslv3=NO
. . .

Lastly, add two final options. The first will not require SSL reuse because it can break many FTP clients. The second will require “high” encryption cipher suites, which currently means key lengths equal to or greater than 128 bits:

/etc/vsftpd.conf
. . .
require_ssl_reuse=NO
ssl_ciphers=HIGH
. . .

Here is how this section of the file should appear after all of these changes have been made:

/etc/vsftpd.conf
# This option specifies the location of the RSA certificate to use for SSL
# encrypted connections.
#rsa_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
#rsa_private_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
rsa_cert_file=/etc/ssl/private/vsftpd.pem
rsa_private_key_file=/etc/ssl/private/vsftpd.pem
ssl_enable=YES
allow_anon_ssl=NO
force_local_data_ssl=YES
force_local_logins_ssl=YES
ssl_tlsv1=YES
ssl_sslv2=NO
ssl_sslv3=NO
require_ssl_reuse=NO
ssl_ciphers=HIGH

When you’re done, save and close the file. If you used nano, you can exit by pressing CTRL + X, Y, then ENTER.

Restart the server for the changes to take effect:

  • sudo systemctl restart vsftpd

At this point, you’ll no longer be able to connect with an insecure command line client. If you tried, you’d get the following message:

Output
ftp -p 203.0.113.0 Connected to 203.0.113.0. 220 (vsFTPd 3.0.3) Name (203.0.113.0:default): sammy 530 Non-anonymous sessions must use encryption. ftp: Login failed. 421 Service not available, remote server has closed connection ftp>

Next, verify that you can connect using a client that supports TLS, such as FileZilla.

Step 7 — Testing TLS with FileZilla

Most modern FTP clients can be configured to use TLS encryption. For our purposes, we will demonstrate how to connect with FileZilla because of its cross-platform support. Consult the documentation for other clients.

When you first open FileZilla, find the Site Manager icon located above the word Host, the leftmost icon on the top row. Click this button:

Site Manager Screen Shot

A new window will open. Click the New Site button in the bottom right corner:

New Site Button

Under My Sites a new icon with the words New Site will appear. You can name it now or return later and use the Rename button.

Fill out the Host field with the name or IP address. Under the Encryption drop-down menu, select Require explicit FTP over TLS.

For Logon Type, select Ask for password. Fill in your FTP user in the User field:

General Settings Tab

Click the Connect button at the bottom of the interface. You will be asked for the user’s password:

Password Dialogue

Select OK to connect. You should now be connected to your server with TLS/SSL encryption.

Next, you will be presented with a server certificate that looks like the following:

Site Certificate Dialogue

When you’ve accepted the certificate, double-click the files folder and drag upload.txt to the left to confirm that you’re able to download files:

Download test.txt

When you’ve done that, right-click on the local copy, rename it to upload-tls.txt and drag it back to the server to confirm that you can upload files:

Rename and Upload

You’ve now confirmed that you can securely and successfully transfer files with SSL/TLS enabled.

Step 8 — Disabling Shell Access (Optional)

If you’re unable to use TLS because of client requirements, you can gain some security by disabling the FTP user’s ability to log in any other way. One way to prevent it is by creating a custom shell. Although this will not provide any encryption, it may be worth doing so as to limit the access of a compromised account to files accessible by FTP.

First, open a file called ftponly in the bin directory:

  • sudo nano /bin/ftponly

Add a message telling the user why they are unable to log in:

/bin/ftponly
#!/bin/sh
echo "This account is limited to FTP access only."

Save the file and exit your editor. If you used nano, you can exit by pressing CTRL + X, Y, then ENTER.

Then, change the permissions to make the file executable:

  • sudo chmod a+x /bin/ftponly

Open the list of valid shells:

  • sudo nano /etc/shells

At the bottom add:

/etc/shells
. . .
/bin/ftponly

Update the user’s shell with the following command:

  • sudo usermod sammy -s /bin/ftponly

Now, try logging into your server as sammy:

  • ssh sammy@your_server_ip

You will receive the following message :

Output
This account is limited to FTP access only. Connection to 203.0.113.0 closed.

This confirms that the user can no longer ssh to the server and is limited to FTP access only. Please note, if you received an error message when logging into your server, this could mean that your server does not accept password authentication. Using password-based authentication can leave your server vulnerable to attacks, and this is why you may want to consider disabling password authentication. If you’ve already configured SSH-key-based authentication, you can learn more about how to disable password authentication on your server on Step 4 of this tutorial.

Conclusion

In this tutorial, we explained how to set up FTP for users with a local account. If you need to use an external authentication source, you might want to explore vsftpd’s support of virtual users. This offers a rich set of options through the use of PAM, the Pluggable Authentication Modules, and is a good choice if you manage users in another system such as LDAP or Kerberos. You can also read about vsftpd features, latest releases, and updates to learn more.

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