iptables for FTP

[valiance]

I just bought a VDS and installed vsftpd, which works fine if I stop the iptables service.

FTP is required for the server bot (similar to BigBrotherBot) to remotely connect to the game server log files. (I do not want to host the bot locally, I have another VPS for it)

I have been trying for the last 3 hours to get this to work, I have read the sticky post about setting up FTP, searched the forum, searched google endlessly.

I have saved the iptables after I created them and then restarted the iptables service.

Iptables --list:

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Chain INPUT (policy ACCEPT)
target     prot opt source               destination
ACCEPT     tcp  --  anywhere             anywhere            tcp spts:1024:65535 dpts:1024:65535 state ESTABLISHED
ACCEPT     tcp  --  anywhere             anywhere            tcp spt:ftp-data state RELATED,ESTABLISHED
ACCEPT     tcp  --  anywhere             anywhere            tcp spt:ftp state ESTABLISHED
ACCEPT     all  --  anywhere             anywhere            state RELATED,ESTABLISHED
ACCEPT     icmp --  anywhere             anywhere
ACCEPT     all  --  anywhere             anywhere
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:ssh
REJECT     all  --  anywhere             anywhere            reject-with icmp-host-prohibited

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination
REJECT     all  --  anywhere             anywhere            reject-with icmp-host-prohibited

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
ACCEPT     tcp  --  anywhere             anywhere            tcp dpt:ftp state NEW,ESTABLISHED
ACCEPT     tcp  --  anywhere             anywhere            tcp dpt:ftp-data state ESTABLISHED
ACCEPT     tcp  --  anywhere             anywhere            tcp spts:1024:65535 dpts:1024:65535 state RELATED,ESTABLISHED

Iptables - Commands:

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From: http://www.cyberciti.biz/faq/iptables-passive-ftp-is-not-working/

# Allow FTP connections @ port 21
iptables -A INPUT  -p tcp --sport 21 -m state --state ESTABLISHED -j ACCEPT
iptables -A OUTPUT -p tcp --dport 21 -m state --state NEW,ESTABLISHED -j ACCEPT
 
# Allow Active FTP Connections
iptables -A INPUT -p tcp --sport 20 -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A OUTPUT -p tcp --dport 20 -m state --state ESTABLISHED -j ACCEPT
 
# Allow Passive FTP Connections
iptables -A INPUT -p tcp --sport 1024: --dport 1024:  -m state --state ESTABLISHED -j ACCEPT
iptables -A OUTPUT -p tcp --sport 1024: --dport 1024:  -m state --state ESTABLISHED,RELATED -j ACCEPT

/etc/vsftpd/vsftpd.conf:

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# Example config file /etc/vsftpd/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.
#
# Allow anonymous FTP? (Beware - allowed by default if you comment this out).
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
#
# The target log file can be vsftpd_log_file or xferlog_file.
# This depends on setting xferlog_std_format parameter
xferlog_enable=YES
#
# Make sure PORT transfer connections originate from port 20 (ftp-data).
connect_from_port_20=NO
# 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
#
# The name of log file when xferlog_enable=YES and xferlog_std_format=YES
# WARNING - changing this filename affects /etc/logrotate.d/vsftpd.log
xferlog_file=/var/log/xferlog
#
# Switches between logging into vsftpd_log_file and xferlog_file files.
# NO writes to vsftpd_log_file, YES to xferlog_file
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=nobody
#
# 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 UrtBot 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 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 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_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
#
# 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

pasv_enable=YES

pasv_promiscuous=YES
port_promiscuous=YES

pasv_min_port=60200
pasv_max_port=60300

pam_service_name=vsftpd
userlist_enable=YES
tcp_wrappers=YES

Thank you so much if you can help me

[Edge100x]

A few immediate notes --

- Why do you wish to run a firewall on your side with a default-block rule? This is not something that I generally recommend on a properly-secured server, for performance reasons.
- You should use -j DROP instead of -j REJECT. With the latter, a DDoS attack against you will be much more effective.
- Your default action on the outbound is ACCEPT, so you don't need any rules there with the same action. (Generally you also shouldn't need to create OUTPUT rules.)
- You don't need to create FORWARD rules unless you're using forwarding.
- You should restrict the inbound ports allowed much more than the range of 1024:65535, if you want the default-block rule to mean much. Specifically, you'll want to go with pasv_min_port:pasv_max_port.
- You're missing a rule to allow new connections to port 21 on the inbound, and the INPUT rule uses --sport instead of --dport. Modify your existing rule from this:

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

to this:

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

[valiance]

Thank you for your help! I can now connect to the FTP server.

But it will not enter passive mode, I am guessing there is something wrong with the iptable rule for it.

This is what I am using (I also tried this with NEW,ESTABLISHED and removing --sport 6200:6300):

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iptables -I INPUT -p tcp --sport 60200:60300 --dport 60200:60300  -m state --state ESTABLISHED -j ACCEPT

The server came with the other rules that are there, for REJECT instead of DROP, I have no idea how to recreate the REJECT rule to delete it, or how to create a DROP rule to replace it.

Sorry for knowing almost nothing about iptables, I am quite new to using them.

I also deleted all the output rules and the port 20 input rule (port 20 is turned off in vsftpd.conf)

[valiance]

I got passive mode working using:

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iptables -A INPUT -p tcp --dport 60200:60300 -j ACCEPT

Thanks again for your help!

[Edge100x]

For that rule, try removing the source port specification, as clients could be using any port across the ephemeral range.

iptables -I INPUT -p tcp --dport 60200:60300 -m state --state ESTABLISHED -j ACCEPT

Edit: You posted as I was writing my reply