Introducción
Vsftpd (Very Secure FTP Daemon) o demonio FTP muy seguro es un servidor FTP liviano, potente y altamente configurable. Se encuentra en los repositorios de todas las distribuciones Linux.
El uso más extendido de FTP es para acceder al servidor web para modificar, subir, eliminar o modificar permisos de archivos o directorios.
En este artículo vamos a ver cómo instalarlo y configurarlo con una instalación previa de apache.
Instalación de VSFTPD
Para instalar el servicio escribimos lo siguiente:
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# apt install -y vsftpd
Arranque, parada y estado de VSFTPD
Para arrancar el servicio VSFTPD escribimos lo siguiente:
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# service vsftpd start
Para parar el servicio VSFTPD escribimos lo siguiente:
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# service vsftpd stop
Para saber el estado del servicio VSTPD escribimos lo siguiente:
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# service vsftpd status
Fichero de configuración /etc/vsftpd.conf
Fichero de configuración general:
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# Example config file /etc/vsftpd.conf
#
# The default compiled in settings are fairly paranoid. This sample file
# loosens things up a bit, to make the ftp daemon more usable.
# Please see vsftpd.conf.5 for all compiled in defaults.
#
# READ THIS: This example file is NOT an exhaustive list of vsftpd options.
# Please read the vsftpd.conf.5 manual page to get a full idea of vsftpd's
# capabilities.
#
#
# Run standalone? vsftpd can run either from an inetd or as a standalone
# daemon started from an initscript.
listen=NO
#
# This directive enables listening on IPv6 sockets. By default, listening
# on the IPv6 "any" address (::) will accept connections from both IPv6
# and IPv4 clients. It is not necessary to listen on *both* IPv4 and IPv6
# sockets. If you want that (perhaps because you want to listen on specific
# addresses) then you must run two copies of vsftpd with two configuration
# files.
listen_ipv6=YES
#
# Allow anonymous FTP? (Disabled by default).
anonymous_enable=NO
#
# Uncomment this to allow local users to log in.
local_enable=YES
#
# Uncomment this to enable any form of FTP write command.
#write_enable=YES
#
# Default umask for local users is 077. You may wish to change this to 022,
# if your users expect that (022 is used by most other ftpd's)
#local_umask=022
#
# 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
#
# Activate directory messages - messages given to remote users when they
# go into a certain directory.
dirmessage_enable=YES
#
# If enabled, vsftpd will display directory listings with the time
# in your local time zone. The default is to display GMT. The
# times returned by the MDTM FTP command are also affected by this
# option.
use_localtime=YES
#
# Activate logging of uploads/downloads.
xferlog_enable=YES
#
# Make sure PORT transfer connections originate from port 20 (ftp-data).
connect_from_port_20=YES
#
# If you want, you can arrange for uploaded anonymous files to be owned by
# a different user. Note! Using "root" for uploaded files is not
# recommended!
#chown_uploads=YES
#chown_username=whoever
#
# You may override where the log file goes if you like. The default is shown
# below.
#xferlog_file=/var/log/vsftpd.log
#
# If you want, you can have your log file in standard ftpd xferlog format.
# Note that the default log file location is /var/log/xferlog in this case.
#xferlog_std_format=YES
#
# You may change the default value for timing out an idle session.
#idle_session_timeout=600
#
# You may change the default value for timing out a data connection.
#data_connection_timeout=120
#
# It is recommended that you define on your system a unique user which the
# ftp server can use as a totally isolated and unprivileged user.
#nopriv_user=ftpsecure
#
# Enable this and the server will recognise asynchronous ABOR requests. Not
# recommended for security (the code is non-trivial). Not enabling it,
# however, may confuse older FTP clients.
#async_abor_enable=YES
#
# By default the server will pretend to allow ASCII mode but in fact ignore
# the request. Turn on the below options to have the server actually do ASCII
# mangling on files when in ASCII mode.
# Beware that on some FTP servers, ASCII support allows a denial of service
# attack (DoS) via the command "SIZE /big/file" in ASCII mode. vsftpd
# predicted this attack and has always been safe, reporting the size of the
# raw file.
# ASCII mangling is a horrible feature of the protocol.
#ascii_upload_enable=YES
#ascii_download_enable=YES
#
# You may fully customise the login banner string:
#ftpd_banner=Welcome to blah FTP service.
#
# You may specify a file of disallowed anonymous e-mail addresses. Apparently
# useful for combatting certain DoS attacks.
#deny_email_enable=YES
# (default follows)
#banned_email_file=/etc/vsftpd.banned_emails
#
# You may restrict local users to their home directories. See the FAQ for
# the possible risks in this before using chroot_local_user or
# chroot_list_enable below.
#chroot_local_user=YES
#
# You may specify an explicit list of local users to chroot() to their home
# directory. If chroot_local_user is YES, then this list becomes a list of
# users to NOT chroot().
# (Warning! chroot'ing can be very dangerous. If using chroot, make sure that
# the user does not have write access to the top level directory within the
# chroot)
#chroot_local_user=YES
#chroot_list_enable=YES
# (default follows)
#chroot_list_file=/etc/vsftpd.chroot_list
#
# You may activate the "-R" option to the builtin ls. This is disabled by
# default to avoid remote users being able to cause excessive I/O on large
# sites. However, some broken FTP clients such as "ncftp" and "mirror" assume
# the presence of the "-R" option, so there is a strong case for enabling it.
#ls_recurse_enable=YES
#
# Customization
#
# Some of vsftpd's settings don't fit the filesystem layout by
# default.
#
# This option should be the name of a directory which is empty. Also, the
# directory should not be writable by the ftp user. This directory is used
# as a secure chroot() jail at times vsftpd does not require filesystem
# access.
secure_chroot_dir=/var/run/vsftpd/empty
#
# This string is the name of the PAM service vsftpd will use.
pam_service_name=vsftpd
#
# 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
ssl_enable=NO
#
# Uncomment this to indicate that vsftpd use a utf8 filesystem.
#utf8_filesystem=YES
Parámetros generales
A continuación se explican algunos parámetros generales de este fichero:
- Establecer un mensaje de bienvenida en el servidor FTP:
ftpd_banner. - Limitar el número de conexiones hacia el servidor FTP:
max_clients. - Limitar el número de conexiones por IP hacia el servidor FTP:
max_per_ip.
Parámetros para la gestión de usuarios
Los usuarios del servidor FTP son los usuarios del sistema. Crear usuarios en GNU Linux se hace de la siguiente forma:
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useradd -d carpeta/usuario
A continuación se explican algunos parámetros que hacen referencia a la gestión de usuarios:
- Habilitar o deshabilitar accesos anónimos al servidor FTP:
anonymous_enable. - Habilitar o deshabilitar autenticarse a los usuarios:
local_enable. - Habilitar o deshabilitar la escritura del servidor FTP:
write_enable. - Habilitar el usuario anónimo para subir contenido al servidor FTP:
anon_upload_enable. - Habilitar el usuario anónimo la función de crear carpetas en el servidor FTP:
anon_mkdir_write_enable.
Parámetros para enjaular usuarios (Chroot)
Parámetros para enjaular a determinados usuarios, es decir, evitar que anden por otros directorios que no sean los que nosotros indicamos:
- Enjaular a determinados usuarios:
chroot_local_user. - Habilitar o deshabilitar la lista de usuarios enjaulados:
chroot_list_enable. - Indicar el fichero donde están los usuarios enjaulados:
chroot_list_file. - Indicar que se permite escribir a los usuarios enjaulados:
allow_writeable_chroot.
En el fichero /etc/vsftpd.chroot_list introducimos la lista de usuarios del sistema que queremos enjaular. Es posible que sea necesario crear este fichero. Sólo tendremos que crear tantas líneas con usuarios del sistema que vayan a tener acceso al FTP como queramos. Los usuarios del servicio FTP serán los usuarios del sistema.
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usuario1
usuario2
Parámetros para gestionar los permisos
Parámetros para modificar los permisos de los ficheros que suban los usuarios al servidor FTP:
- Establecer permisos de creación y subida de ficheros y directorios:
local_umask.
Si no recuerdas que es el umask o como funcionan los permisos en GNU Linux te recomiendo leer el artículo Permisos en GNU Linux.
Parámetros para limitar el ancho de banda
Parámetros para limitar de ancho de banda del servidor FTP:
- Limitar la tasa de transferencia usamos:
anon_max_rate. - Limitar la tasa de los usuarios:
local_max_rate.