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This example shows how to set up vsftpd / PAM with "virtual users".
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A virtual user is a user login which does not exist as a real login on the
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system. Virtual users can therefore be more secure than real users, beacuse
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a compromised account can only use the FTP server.
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Virtual users are often used to serve content that should be accessible to
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untrusted users, but not generally accessible to the public.
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Step 1) Create the virtual users database.
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We are going to use pam_userdb to authenticate the virtual users. This needs
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a username / password file in "db" format - a common database format.
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To create a "db" format file, first create a plain text files with the
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usernames and password on alternating lines.
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See example file "logins.txt" - this specifies "tom" with password "foo" and
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"fred" with password "bar".
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Whilst logged in as root, create the actual database file like this:
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db_load -T -t hash -f logins.txt /etc/vsftpd_login.db
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(Requires the Berkeley db program installed).
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NOTE: Many systems have multiple versions of "db" installed, so you may
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need to use e.g. db3_load for correct operation. This is known to affect
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some Debian systems. The core issue is that pam_userdb expects its login
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database to be a specific db version (often db3, whereas db4 may be installed
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This will create /etc/vsftpd_login.db. Obviously, you may want to make sure
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the permissions are restricted:
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chmod 600 /etc/vsftpd_login.db
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For more information on maintaing your login database, look around for
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documentation on "Berkeley DB", e.g.
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http://www.sleepycat.com/docs/utility/index.html
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Step 2) Create a PAM file which uses your new database.
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See the example file vsftpd.pam. It contains two lines:
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auth required /lib/security/pam_userdb.so db=/etc/vsftpd_login
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account required /lib/security/pam_userdb.so db=/etc/vsftpd_login
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This tells PAM to authenticate users using our new database. Copy this PAM
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file to the PAM directory - typically /etc/pam.d/
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cp vsftpd.pam /etc/pam.d/ftp
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(Note - if you set pam_service_name to e.g. vsftpd instead, you'll need to copy
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to /etc/pam.d/vsftpd).
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Step 3) Set up the location of the files for the virtual users.
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useradd -d /home/ftpsite virtual
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drwx------ 3 virtual virtual 4096 Jul 30 00:39 /home/ftpsite
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We have created a user called "virtual" with a home directory "/home/ftpsite".
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Let's add some content to this download area:
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cp /etc/hosts /home/ftpsite
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chown virtual.virtual /home/ftpsite/hosts
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Step 4) Create your vsftpd.conf config file.
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See the example in this directory. Let's go through it line by line:
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This disables anonymous FTP for security, and enables non-anonymous FTP (which
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is what virtual users use).
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anon_mkdir_write_enable=NO
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anon_other_write_enable=NO
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These ensure that for security purposes, no write commands are allowed.
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This makes sure that the virtual user is restricted to the virtual FTP area
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/home/ftpsite we set up above.
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guest_username=virtual
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The guest_enable is very important - it activates virtual users! And
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guest_username says that all virtual users are mapped to the real user
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"virtual" that we set up above. This will also determine where on the
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filesystem the virtual users end up - the home directory of the user
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"virtual", /home/ftpsite.
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This puts vsftpd in "standalone" mode - i.e. not running from an inetd. This
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means you just run the vsftpd executable and it will start up. This also
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makes vsftpd listen for FTP requests on the non-standard port of 10021 (FTP
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These put a port range on passive FTP incoming requests - very useful if
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you are configuring a firewall.
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Copy the example vsftpd.conf file to /etc:
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Step 5) Start up vsftpd.
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Go to the directory with the vsftpd binary in it, and:
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If all is well, the command will sit there. If all is not well, you will
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likely see some error message.
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Launch another shell session (or background vsftpd with CTRL-Z and then "bg").
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Here is an example of an FTP session:
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Connected to localhost (127.0.0.1).
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220 ready, dude (vsFTPd 1.1.0: beat me, break me)
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Name (localhost:chris): tom
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331 Please specify the password.
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230 Login successful. Have fun.
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Remote system type is UNIX.
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Using binary mode to transfer files.
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227 Entering Passive Mode (127,0,0,1,117,135)
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150 Here comes the directory listing.
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226 Transfer done (but failed to open directory).
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The password we gave was "foo".
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Do not be alarmed by the "failed to open directory". That is because the
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directory /home/ftpsite is not world readable (we could change this
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behaviour if we wanted using anon_world_readable_only=NO but maybe we want
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it this way for security.
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We can see that we have access to the "hosts" file we copied into the virtual
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FTP area, via the size command.
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.pc/03-db-doc.patch/EXAMPLE/VIRTUAL_USERS/README
