Setup FTP Server

By Sompan Chsilp
30 October 2010

FTP Server คือโปรแกรมที่ใช้สำหรับช่วยในการอัพโหลดและดาวน์โหลดไฟล์ไปมาระหว่างเครื่องเซิร์ฟเวอร์และเครื่องไคลเอ็นท์ สำหรับเครื่องเเซิร์ฟเวอร์นี้ได้ทำการติดตั้งและคอนฟิก FTP Server ไว้ให้แล้ว เพียงแต่เปิดไฟล์วอลล์และสั่งรันโปรแกรมทุกอย่างก็จะพร้อมใช้

FTP server is a server to provide upload/download files between client computer and the server computer.
On this server, it has been pre configured.  You need to run it and setup firewall for it to function properly.

ต่อไปนี้คือขั้นตอนการเซ็ตอัพ FTP Server
Below are steps if you want to know how to set up FTP server.

1. การติดตั้ง(Installation)
ถ้ายังไม่ติดตั้งโปรแกรมสามารถติดตั้งได้ด้วยคำสั่งในเทอร์มินัลดังนี้
If the server has not been install, install it by using command:

sut@main:~$ sudo apt-get install vsftpd



2. ทำการแก้ไขคอนฟิกไฟล์ /etc/vsftpd.conf
   edit configure file /etc/vsftpd.conf

   อาจใช้คำสั่ง(using command): sudo gedit  /etc/vsftpd.conf

# 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=YES
#
# Run standalone with IPv6?
# Like the listen parameter, except vsftpd will listen on an IPv6 socket
# instead of an IPv4 one. This parameter and the listen parameter are mutually
# exclusive.
#listen_ipv6=YES
#
# Allow anonymous FTP? (Beware - allowed by default if you comment this out).
anonymous_enable=YES
#
# 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
#
# 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
#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 SUTinsServer 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().
#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
#
#
# Debian customization
#
# Some of vsftpd's settings don't fit the Debian filesystem layout by
# default.  These settings are more Debian-friendly.
#
# 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
#
# 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
# This option specifies the location of the RSA key to use for SSL
# encrypted connections.
rsa_private_key_file=/etc/ssl/private/ssl-cert-snakeoil.key


จากคอนฟิกไฟล์ดังกล่าว บรรทัดที่น่าสนใจคือ
From above configure file, interesting lines are:

local_enable=YES
write_enable=YES
สองบรรทัดนี้จะอนุญาตให้ผู้ใช้ที่ได้เพิ่มในระบบเข้าใช้งาน ftp และสามารถอัพโหลดไฟล์ได้
These two line will allow user on the system ftp to this server and can upload files.

chroot_local_user=YES
บรรทัดนี้จะป้องกันให้ผู้ใช้แต่ละคนเห็นแต่ข้อมูลส่วนตัว ไม่เห็นข้อมูลของคนใช้อื่นๆ
This line will prevent a user to see other users' data.

3. ทำการปิดไฟล์วอลล์ชั่วคราว(Disable firewall temporary)
Use command:
sut@main:~$ sudo ufw disable
Firewall stopped and disabled on system startup
sut@main:~$ sudo ufw status
Status: inactive


4. สั่งรัน FTP Server(Start FTP server)

เริ่มรันใช้คำสั่ง( Run with command)
sut@server:~$ sudo service vsftpd start
vsftpd start/running, process 8569

ดูสถานะการทำงาน(To see status)
sut@server:~$ sudo service vsftpd status
vsftpd start/running, process 8569

หรืออาจลองวิธีนี้(Try this)
sut@server:~$ netstat -l -t -n | grep ':21 ' | grep LISTEN
If you see a line as below, it is running
tcp        0      0 0.0.0.0:21              0.0.0.0:*               LISTEN    

และทุกครั้งหลังเปลี่ยนข้อมูลใไฟล์คองฟิก /etc/vsftpd.conf ต้องรันโปรแกรมใหม่ด้วยคำสั่ง
After you change any configure, restart it with command:

sut@server:~$ sudo service vsftpd restart
 * Stopping FTP server: vsftpd                                           [ OK ]
 * Starting FTP server: vsftpd                                           [ OK ]



5. More advanced configure style
Read on the terminal:

man vsftpd
man vsftpd.conf
During viewing manual, to exit press q



6. ถ้าต้องการรัน FTP Server ทุกครั้งพร้อมการบูตคอมพิวเตอร์ให้ใช้คำสั่ง
    To enable ftp server with computer boot use command
sut@server:~$ sudo update-rc.d  vsftpd defaults
แล้วที่จอจะแสดง
update-rc.d: warning: /etc/init.d/vsftpd missing LSB information
update-rc.d: see <http://wiki.debian.org/LSBInitScripts>
 Adding system startup for /etc/init.d/vsftpd ...
   /etc/rc0.d/K20vsftpd -> ../init.d/vsftpd
   /etc/rc1.d/K20vsftpd -> ../init.d/vsftpd
   /etc/rc6.d/K20vsftpd -> ../init.d/vsftpd
   /etc/rc2.d/S20vsftpd -> ../init.d/vsftpd
   /etc/rc3.d/S20vsftpd -> ../init.d/vsftpd
   /etc/rc4.d/S20vsftpd -> ../init.d/vsftpd
   /etc/rc5.d/S20vsftpd -> ../init.d/vsftpd

ถ้าต้องการหยุดการรันทุกครั้งพร้อมการบูตคอมพิวเตอร์ให้ใช้คำสั่ง
sut@server:~$ sudo update-rc.d -f vsftpd remove
แล้วที่จอจะแสดง
 Removing any system startup links for /etc/init.d/vsftpd ...
   /etc/rc0.d/K20vsftpd
   /etc/rc1.d/K20vsftpd
   /etc/rc2.d/S20vsftpd
   /etc/rc3.d/S20vsftpd
   /etc/rc4.d/S20vsftpd
   /etc/rc5.d/S20vsftpd
   /etc/rc6.d/K20vsftpd



7. Fine tune firewall setting for FTP server
คำสั่งให้ไฟล์วอลล์ทำงาน
To allow firewall to be active now and enabled on system boot, use command:

sut@server:~$ sudo ufw enable

Firewall is active and enabled on system startup


เพื่อดูกฏต่างๆ(To see rules:)

sut@server:~$ sudo ufw status


Status: active

To                         Action  From
--                         ------  ----
80/tcp                     ALLOW   Anywhere
443                        ALLOW   Anywhere

แสดงลิสต์ของโปรแกรมต่างๆ
Display known list of application:

sut@server:~$ sudo ufw app list
Available applications:
  Apache
  Apache Full
  Apache Secure
  Bind9
  Dovecot IMAP
  Dovecot POP3
  Dovecot Secure IMAP
  Dovecot Secure POP3
  Lighttpd Full
  Lighttpd HTTP
  Lighttpd HTTPS
  OpenSSH
  Postfix
  Postfix Submission

โชคไม่ดี ที่ไม่มีชื่อ FTP Server แสดงในลิสต์รายชื่อ
Unfortunately, no FTP server on the list.

เราต้องกำหนดพอร์ทขึ้นเอง
We have to add rules by specify ports

กำหนดให้เปิดพอร์ท 20
sut@server:~$ sudo ufw allow 20
Rule added
กำหนดให้เปิดพอร์ท 21
sut@server:~$ sudo ufw allow 21
Rule added

แสดงกฏอีกครั้ง(See rules again)
sut@server:~$ sudo ufw status
Status: active

To                         Action  From
--                         ------  ----
80/tcp                     ALLOW   Anywhere
443                        ALLOW   Anywhere
20                         ALLOW   Anywhere
21                         ALLOW   Anywhere

Note:
 21 is the port that the server listens on.
 20 is the port to use for the server to send/receive data to/from the client.
      It is used for passive mode FTP.

Seucrity concern:
FTP is not a secure protocol.  Data is not encripted so username and password may be sniffed. Security is better if network switch is used in stead of a hub.


More advanced firewall setup, read firewall manual.



FTP Security note
Using FTP to upload/download is rissky. Someone may sniff your username and password.
To perform more secure upload/dowload file to/from server, better to use  SSH.

On the server:
Run SSH server on the server.
User command: sudo service ssh start

Set firewall to allow port 22. 
Use command: sudo ufw allow ssh

Enable firewall
Use command: sudo ufw enable

Display firewall rules:
Use command: sudo ufw status

On the client:
Make sure that firewall not prevent you to connect to outside.
Run program gftp.  Accessing by Applications --> Internet --> gFTP


ftp_server/ftp.png

Note that port 22 and ssh2 are specified.  Using this method will save from password sniffing and no need to run FTP server.