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# Very Secure FTP Daemon

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vsftpd (Very Secure FTP Daemon) is a lightweight, stable and secure FTP server for UNIX-like systems.

## Installation

Install vsftpd and start/enable the `vsftpd.service` daemon.

To use xinetd for monitoring and controlling vsftpd connections, see #Using xinetd.

## Configuration

Most of the settings in vsftpd are done by editing the file `/etc/vsftpd.conf`. The file itself is well-documented, so this section only highlights some important changes you may want to modify. For all available options and documentation, see the vsftpd.conf(5) man page. Files are served by default from `/srv/ftp`.

This article or section is out of date.

Reason: I believe this information is deprecated. libwrap/tcp-wrappers is not dependency of vsftpd and not installed by default. Better to configure firewall rules to limit access. (Discuss in Talk:Very Secure FTP Daemon)

Enable connections `/etc/hosts.allow`:

    # Allow all connections
    vsftpd: ALL
    # IP address range
    vsftpd: 10.0.0.0/255.255.255.0

### Enabling uploading

The `WRITE_ENABLE` flag must be set to YES in `/etc/vsftpd.conf` in order to allow changes to the filesystem, such as uploading:

    write_enable=YES

### Local user login

One must set the line `local_enable` in `/etc/vsftpd.conf` to `YES` in order to allow users in `/etc/passwd` to login:

    local_enable=YES

### Anonymous login

These lines controls whether anonymous users can login. By default, anonymous logins are enabled for download only from `/srv/ftp`:

    /etc/vsftpd.conf

    ...
    # Allow anonymous FTP? (Beware - allowed by default if you comment this out).
    anonymous_enable=YES
    ...
    # Uncomment this to allow the anonymous FTP user to upload files. This only
    # has an effect if the above global write enable is activated. Also, you will
    # obviously need to create a directory writable by the FTP user.
    #anon_upload_enable=YES
    #
    # Uncomment this if you want the anonymous FTP user to be able to create
    # new directories.
    #anon_mkdir_write_enable=YES
    ...

You may also add e.g. the following options (see vsftpd.conf(5) for more):

    /etc/vsftpd.conf

    # No password is required for an anonymous login
    no_anon_password=YES

    # Maximum transfer rate for an anonymous client in Bytes/second
    anon_max_rate=30000

    # Directory to be used for an anonymous login
    anon_root=/example/directory/

### Chroot jail

A chroot environment that prevents the user from leaving its home directory can be set up. To enable this, add the following lines to `/etc/vsftpd.conf`:

    chroot_list_enable=YES
    chroot_list_file=/etc/vsftpd.chroot_list

The `chroot_list_file` variable specifies the file which contains users that are jailed.

For a more restricted environment, specify the line:

    chroot_local_user=YES

This will make local users jailed by default. In this case, the file specified by `chroot_list_file` lists users that are not in a chroot jail.

### Limiting user login

It is possible to prevent users from logging into the FTP server by adding two lines to `/etc/vsftpd.conf`:

    userlist_enable=YES
    userlist_file=/etc/vsftpd.user_list

`userlist_file` now specifies the file which lists users that are not able to login.

If you only want to allow certain users to login, add the line:

    userlist_deny=NO

The file specified by `userlist_file` will now contain users that are able to login.

### Limiting connections

The data transfer rate, i.e. number of clients and connections per IP for local users can be limited by adding the information in `/etc/vsftpd.conf`:

    local_max_rate=1000000 # Maximum data transfer rate in bytes per second
    max_clients=50         # Maximum number of clients that may be connected
    max_per_ip=2           # Maximum connections per IP

### Using xinetd

Xinetd provides enhanced capabilities for monitoring and controlling connections. It is not necessary though for a basic good working vsftpd-server.

Installation of vsftpd will add a necessary service file, `/etc/xinetd.d/vsftpd`. By default services are disabled. Enable the ftp service:

    service ftp
    {
            socket_type             = stream
            wait                    = no
            user                    = root
            server                  = /usr/bin/vsftpd
            log_on_success  += HOST DURATION
            log_on_failure  += HOST
            disable                 = no
    }

If you have set the vsftpd daemon to run in standalone mode make the following change in `/etc/vsftpd.conf`:

    listen=NO

Otherwise connection will fail:

    500 OOPS: could not bind listening IPv4 socket

Instead of starting the vsftpd daemon start and enable `xinetd.service`.

### Using SSL/TLS to secure FTP

This article or section needs language, wiki syntax or style improvements. See Help:Style for reference.

Reason: Do not duplicate OpenSSL#Usage. (Discuss in Talk:Very Secure FTP Daemon)

First, you need a X.509 SSL/TLS certificate to use TLS. If you do not have one, you can easily generate a self-signed certificate as follows:

    # cd /etc/ssl/certs
    # openssl req -x509 -nodes -days 7300 -newkey rsa:2048 -keyout vsftpd.pem -out vsftpd.pem
    # chmod 600 vsftpd.pem

You will be asked questions about your company, etc. As your certificate is not a trusted one, it does not really matter what is filled in, it will just be used for encryption. To use a trusted certificate, you can get one from a certificate authority like Let's Encrypt.

Then, edit the configuration file:

    /etc/vsftpd.conf

    ssl_enable=YES

    # if you accept anonymous connections, you may want to enable this setting
    #allow_anon_ssl=NO

    # by default all non anonymous logins and forced to use SSL to send and receive password and data, set to NO to allow non secure connections
    force_local_logins_ssl=NO
    force_local_data_ssl=NO

    # TLS v1 protocol connections are preferred and this mode is enabled by default while SSL v2 and v3 are disabled
    # the settings below are the default ones and do not need to be changed unless you specifically need SSL
    #ssl_tlsv1=YES
    #ssl_sslv2=NO
    #ssl_sslv3=NO

    # provide the path of your certificate and of your private key
    # note that both can be contained in the same file or in different files
    rsa_cert_file=/etc/ssl/certs/vsftpd.pem
    rsa_private_key_file=/etc/ssl/certs/vsftpd.pem

    # this setting is set to YES by default and requires all data connections exhibit session reuse which proves they know the secret of the control channel.
    # this is more secure but is not supported by many FTP clients, set to NO for better compatibility
    require_ssl_reuse=NO

### Resolve hostname in passive mode

To override the IP address vsftpd advertises in passive mode by the hostname of your server and have it DNS resolved at startup, add the following two lines in `/etc/vsftpd.conf`:

    pasv_addr_resolve=YES
    pasv_address=yourdomain.org

Note

- For dynamic DNS, it is not necessary to periodically update pasv_address and restart the server as it can sometimes be read.
- You may not be able to connect in passive mode via LAN anymore, in this case try the active mode instead from the LAN clients.

### Port configurations

It may be necessary to adjust the default FTP listening port and the passive mode data ports. This is a way to resolve traffic when the server is behind a NAT:

- For FTP servers exposed to the web, to reduce the likelihood of the server being attacked, the listening port can be changed to something other than the standard port 21.
- To limit the passive mode ports to open ports, a range can be provided.

The ports can be defined in the configuration file as illustrated below:

    /etc/vsftpd.conf

    listen_port=2211

    pasv_min_port=5000
    pasv_max_port=5003

Tip Remember to modify your firewall to open these ports when behind a NAT.

### Configuring the firewall

This article or section needs expansion.

Reason: This section should explain the equivalent with nftables, possibly replacing all mentions of iptables. (Discuss in Talk:Very Secure FTP Daemon)

Often the server running the FTP daemon is protected by an iptables firewall. To allow access to the FTP server the corresponding port needs to be opened using something like

    # iptables -A INPUT -m state --state NEW -m tcp -p tcp --dport 21 -j ACCEPT

This article will not provide any instruction on how to set up iptables but here is an example: Simple stateful firewall.

There are some kernel modules needed for proper FTP connection handling by iptables that should be referenced here. Among those especially nf_conntrack_ftp. It is needed as FTP uses the given listen_port (21 by default) for commands only; all the data transfer is done over different ports. These ports are chosen by the FTP daemon at random and for each session (also depending on whether active or passive mode is used). To tell iptables that packets on ports should be accepted, nf_conntrack_ftp is required. You can explicitly load the module at boot.

If the kernel >= 4.7 you either need to set net.netfilter.nf_conntrack_helper=1 via sysctl e.g.

    # echo net.netfilter.nf_conntrack_helper=1 > /etc/sysctl.d/70-conntrack.conf

or use

    # iptables -A PREROUTING -t raw -p tcp --dport 21 -j CT --helper ftp

## Tips and tricks

### PAM with virtual users

Since PAM no longer provides `pam_userdb.so` another easy method is to use libpam_pwdfile. This section is however limited to explain how to configure a chroot environment and authentication by `pam_pwdfile.so`.

In this example we create the directory `vsftpd`:

    # mkdir /etc/vsftpd

One option to create and store user names and passwords is to use the Apache generator htpasswd:

    # htpasswd -c /etc/vsftpd/.passwd <username>

Replace the `<username>` with the user you want to create.

A problem with the above command is that vsftpd might not be able to read the generated MD5 hashed password. If running the same command with the -d switch, crypt() encryption, password become readable by vsftpd, but the downside of this is less security and a password limited to 8 characters. Openssl could be used to produce a MD5 based BSD password with algorithm 1:

    # openssl passwd -1

Whatever solution the produced `/etc/vsftpd/.passwd` should look like this:

    username1:hashed_password1
    username2:hashed_password2
    ...

Next you need to create a PAM service using `pam_pwdfile.so` and the generated `/etc/vsftpd/.passwd` file. In this example we create a PAM policy for vsftpd with the following content:

    /etc/pam.d/vsftpd

    auth required pam_pwdfile.so pwdfile /etc/vsftpd/.passwd
    account required pam_permit.so

Now it is time to create a home for the virtual users. In the example `/srv/ftp` is decided to host data for virtual users, which also reflects the default directory structure of Arch. First create the general user virtual and make `/srv/ftp` its home:

    # useradd -d /srv/ftp virtual

Make virtual the owner:

    # chown virtual:virtual /srv/ftp

A basic `/etc/vsftpd.conf` with no private folders configured, which will default to the home folder of the virtual user:

    listen=YES
    listen 21
    connect_from_port_20=YES    # sample config file enables it, ftp data
    dirmessage_enable=YES       # sample config data enables it
    xferlog_enable=YES          # sample config data enables it
    pam_service_name=vsftpd     # pointing to the correct PAM service file `/etc/pam.d/vsftpd` rather than `/etc/pam.d/ftp`

    anonymous_enable=NO         # we does not use anonymous mode
    local_enable=YES            # we config virtual user use local privileges, virtual_use_local_privs=YES

    write_enable=YES            # global config, write to filesystem
    hide_ids=YES                # in ftp client interactive console, ls -la: uid=1001 -> ftp

    chroot_local_user=YES       # we do not want user to get the real root(/) directory
    guest_enable=YES            # for virtual user
    guest_username=virtual      # virtual user name: virtual
    virtual_use_local_privs=YES # permission of virtual user=local user

For more detailed meaning of above options, see the vsftpd.conf(5) man page.

Some parameters might not be necessary for your own setup. If you want the chroot environment to be writable you will need to add the following to the configuration file:

    allow_writeable_chroot=YES

Otherwise vsftpd because of default security settings will complain if it detects that chroot is writable.

Start `vsftpd.service`.

You should now be able to login from a ftp-client with any of the users and passwords stored in `/etc/vsftpd/.passwd`.

#### Adding private folders for the virtual users

First create directories for users:

    # mkdir /srv/ftp/user1
    # mkdir /srv/ftp/user2
    # chown virtual:virtual /srv/ftp/user?/

Then, add the following lines to `/etc/vsftpd.conf`:

    local_root=/srv/ftp/$USER
    user_sub_token=$USER

#### Anonymous login as virtual users

We can modify the PAM policy for vsftpd to the following contents, to allow password-free login as virtual user:

    /etc/pam.d/vsftpd

    auth required pam_permit.so
    account required pam_permit.so

## Troubleshooting

### vsftpd: refusing to run with writable root inside chroot()

As of vsftpd 2.3.5, the chroot directory that users are locked to must not be writable. This is in order to prevent a security vulnerabilty.

The safe way to allow upload is to keep chroot enabled, and configure your FTP directories.

    local_root=/srv/ftp/user

    # mkdir -p /srv/ftp/user/upload
    # chmod 550 /srv/ftp/user
    # chmod 750 /srv/ftp/user/upload

If you must:

You can put this into your `/etc/vsftpd.conf` to workaround this security enhancement (since vsftpd 3.0.0; from Fixing 500 OOPS: vsftpd: refusing to run with writable root inside chroot ()):

    allow_writeable_chroot=YES

### FileZilla Client: GnuTLS error -8 -15 -110 when connecting via SSL

vsftpd tries to display plain-text error messages in the SSL session. In order to debug this, temporarily disable encryption and you will see the correct error message.[1]

Often these errors can be solved by adding[2]: `seccomp_sandbox=NO`

### vsftpd.service fails to run on boot

If you have enabled `vsftpd.service` and it fails to run on boot, edit it and make sure it is set to load after `network.target` in the service file:

    vsftpd.service

    [Unit]
    Description=vsftpd daemon
    After=network.target

### Passive mode replies with the local IP address to a remote connection

If vsftpd returns a local address to a remote connection, like:

    227 Entering Passive Mode (192,168,0,19,192,27).

It may be that the FTP server is behind a NAT router and while some devices monitor FTP connections and dynamically replace the local IP address specification by the external IP address for packets containing the PASV response, some do not.

Indicate the external IP address in the vsftpd configuration using:

     pasv_address=externalIPaddress

or alternatively:

    pasv_addr_resolve=YES
    pasv_address=my.domain.name

In case internal connection is not possible after this change, one may need to run 2 vsftpd, one for internal and one for external connections.

Tip To find out whether the NAT router intercepts the PASV response and replaces the internal IP with an external IP, one can check the server response from the client side in TLS mode. The enciphered packets cannot be identified by the router and are not modified.

### ipv6 only fails with: 500 OOPS: run two copies of vsftpd for IPv4 and IPv6

you most likely have commented out the line

    # When "listen" directive is enabled, vsftpd runs in standalone mode and
    # listens on IPv4 sockets. This directive cannot be used in conjunction
    # with the listen_ipv6 directive.
    #listen=YES
    #
    # This directive enables listening on IPv6 sockets. To listen on IPv4 and IPv6
    # sockets, you must run two copies of vsftpd with two configuration files.
    # Make sure, that one of the listen options is commented !!
    listen_ipv6=YES

instead of setting

    # When "listen" directive is enabled, vsftpd runs in standalone mode and
    # listens on IPv4 sockets. This directive cannot be used in conjunction
    # with the listen_ipv6 directive.
    listen=NO

### vsftpd connections fail on a machine using nis with: yp_bind_client_create_v2: RPC: Unable to send

as mentioned on the vsftpd faq page, "...built-in sandboxing uses network isolation on Linux. This may be interfering with any module that needs to use the network to perform operations or lookups"

add this undocumented line to your `/etc/vsftpd.conf`

    isolate_network=NO

### LIST command resets connection

Adding

    seccomp_sandbox=NO

in the `vsftpd.conf` file fixes this issue.

## Hardening

Just like any other service, VSFTPD can be hardened by modifying its systemd unit. Hardening is also called sandboxing in the literature. The following sandboxing options are an effective way to limit the exposure of the system towards the unit's processes.

Below is an example of a hardened drop-in file. Adjust the following file to your liking:

    /etc/systemd/system/vsftpd.service.d/harden.conf

    [Service]
    PrivateTmp = true
    ProtectSystem = strict
    ProtectHome = true
    ProtectKernelTunables = true
    ReadWritePaths=/srv/ftp /mnt/cctv /var/log/vsftpd.log
    ReadOnlyPaths = /mnt
    InaccessiblePaths = /mnt/mybackup

This will allow VSFTPD to only write to `/srv/ftp`, `/mnt/cctv` and to its own log file, and will restrict writing to the rest of the file system. It will also deny access to the entire `/home`. This also restrict any access to `/mnt/mybackup`. Multiple paths can be specified for this option.

More details on the systemd sandboxing options can be found at systemd.exec(5) § SANDBOXING.

## See also

- vsftpd official homepage
- vsftpd.conf(5)
- vsftpd FAQ

Category:

- FTP servers

Hidden categories:

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