FTP is a very insecure protocol because all passwords and all data are transferred in clear text. By using TLS, the whole communication can be encrypted, thus making FTP much more secure. This article explains how to set up ProFTPd with TLS on an Ubuntu 8.10 server.

1 Preliminary Note

In this tutorial I use the hostname server1.example.com with the IP address 192.168.0.100. These settings might differ for you, so you have to replace them where appropriate.

Because we must run all the steps from this tutorial with root privileges, we can either prepend all commands in this tutorial with the string sudo, or we become root right now by typing

sudo su

2 Installing ProFTPd And OpenSSL

OpenSSL is needed by TLS; to install ProFTPd and OpenSSL, we simply run:

apt-get install proftpd openssl

You will be asked a question:

Run proftpd: <– standalone

For security reasons you can add the following lines to /etc/proftpd/proftpd.conf (thanks to Reinaldo Carvalho; more information can be found here: http://proftpd.org/localsite/Userguide/linked/userguide.html):

vi /etc/proftpd/proftpd.conf

[...]
DefaultRoot ~
IdentLookups off
ServerIdent on "FTP Server ready."
[...]

3 Creating The SSL Certificate For TLS

In order to use TLS, we must create an SSL certificate. I create it in /etc/proftpd/ssl, therefore I create that directory first:

mkdir /etc/proftpd/ssl

Afterwards, we can generate the SSL certificate as follows:

openssl req -new -x509 -days 365 -nodes -out /etc/proftpd/ssl/proftpd.cert.pem -keyout /etc/proftpd/ssl/proftpd.key.pem

Country Name (2 letter code) [AU]: <– Enter your Country Name (e.g., “DE”).
State or Province Name (full name) [Some-State]: <– Enter your State or Province Name.
Locality Name (eg, city) []: <– Enter your City.
Organization Name (eg, company) [Internet Widgits Pty Ltd]: <– Enter your Organization Name (e.g., the name of your company).
Organizational Unit Name (eg, section) []: <– Enter your Organizational Unit Name (e.g. “IT Department”).
Common Name (eg, YOUR name) []: <– Enter the Fully Qualified Domain Name of the system (e.g. “server1.example.com”).
Email Address []: <– Enter your Email Address.

4 Enabling TLS In ProFTPd

In order to enable TLS in ProFTPd, open /etc/proftpd/proftpd.conf…

vi /etc/proftpd/proftpd.conf

… and uncomment the Include /etc/proftpd/tls.conf line:

[...]
#

# This is used for FTPS connections
#
Include /etc/proftpd/tls.conf
[...]

Then open /etc/proftpd/tls.conf and make it look as follows:

<IfModule mod_tls.c>
TLSEngine                  on
TLSLog                     /var/log/proftpd/tls.log
TLSProtocol                SSLv23
TLSOptions                 NoCertRequest
TLSRSACertificateFile      /etc/proftpd/ssl/proftpd.cert.pem
TLSRSACertificateKeyFile   /etc/proftpd/ssl/proftpd.key.pem
TLSVerifyClient            off
TLSRequired                on
</IfModule>

If you use TLSRequired on, then only TLS connections are allowed (this locks out any users with old FTP clients that don’t have TLS support); by commenting out that line or using TLSRequired off both TLS and non-TLS connections are allowed, depending on what the FTP client supports.

Restart ProFTPd afterwards:

/etc/init.d/proftpd restart

That’s it. You can now try to connect using your FTP client; however, you should configure your FTP client to use TLS (this is a must if you use TLSRequired on) – see the next chapter how to do this with FileZilla.

If you’re having problems with TLS, you can take a look at the TLS log file /var/log/proftpd/tls.log.

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