Difference between revisions of "Very Secure FTP Daemon"

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(Troubleshooting: seccomp_sandbox=NO may still be required)
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Line 8: Line 8:
  
 
== Installation ==
 
== Installation ==
Vsftpd is included in the official repository. Simply install it with pacman:
+
Simply install {{pkg|vsftpd}} from the [[Official Repositories]].
# pacman -S vsftpd
+
  
The server can be started by using the script below:
+
To start the server:
  # /etc/rc.d/vsftpd start
+
  # systemctl start vsftpd.service
  
You can also add vsftpd to your daemon array in {{ic|/etc/rc.conf}} if you want it to be started automatically at boot.
+
If you want it to be started automatically at boot:
 +
# systemctl enable vsftpd.service
  
 
See the xinetd section below for procedures to use vsftpd with xinetd.
 
See the xinetd section below for procedures to use vsftpd with xinetd.
Line 25: Line 25:
 
  write_enable=YES
 
  write_enable=YES
  
=== Local user logging ===
+
=== Local user login ===
 
One must set the line to {{ic|/etc/vsftpd.conf}} to allow users in {{ic|/etc/passwd}} to login:
 
One must set the line to {{ic|/etc/vsftpd.conf}} to allow users in {{ic|/etc/passwd}} to login:
 
  local_enable=YES
 
  local_enable=YES
Line 31: Line 31:
 
=== Anonymous login ===
 
=== Anonymous login ===
 
The line in {{ic|/etc/vsftpd.conf}} controls whether anonymous users can login:
 
The line in {{ic|/etc/vsftpd.conf}} controls whether anonymous users can login:
  anonymous_enable=YES # Allow anonymous login
+
  # Allow anonymous login
  no_anon_password=YES # No password is required for an anonymous login
+
  anonymous_enable=YES
  anon_max_rate=30000 # Maximum transfer rate for an anonymous client in bytes per second
+
# 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 ===
 
=== Chroot jail ===
Line 62: Line 67:
  
 
=== Using xinetd ===
 
=== Using xinetd ===
 +
{{Out of date|Contains reference to rc.conf, which does not exist anymore.}}
 
If you want to use vsftpd with xinetd, add the following lines to {{ic|/etc/xinetd.d/vsftpd}}:
 
If you want to use vsftpd with xinetd, add the following lines to {{ic|/etc/xinetd.d/vsftpd}}:
 
<pre>
 
<pre>
Line 69: Line 75:
 
         wait                    = no
 
         wait                    = no
 
         user                    = root
 
         user                    = root
         server                  = /usr/sbin/vsftpd
+
         server                  = /usr/bin/vsftpd
 
         log_on_success  += HOST DURATION
 
         log_on_success  += HOST DURATION
 
         log_on_failure  += HOST
 
         log_on_failure  += HOST
Line 100: Line 106:
 
  # openssl req -x509 -nodes -days 7300 -newkey rsa:2048 -keyout /etc/ssl/certs/vsftpd.pem -out /etc/ssl/certs/vsftpd.pem
 
  # openssl req -x509 -nodes -days 7300 -newkey rsa:2048 -keyout /etc/ssl/certs/vsftpd.pem -out /etc/ssl/certs/vsftpd.pem
 
  # chmod 600 /etc/ssl/certs/vsftpd.pem
 
  # chmod 600 /etc/ssl/certs/vsftpd.pem
You will be asked alot of Questions about your Company etc., as your Certificate is not a trusted one it doesn't really matter what you fill in. You will use this for encryption! If you plan to use this in a matter of trust get one from a CA like thawte, verisign etc.  
+
You will be asked a lot of Questions about your Company etc., as your Certificate is not a trusted one it doesn't really matter what you fill in. You will use this for encryption! If you plan to use this in a matter of trust get one from a CA like thawte, verisign etc.  
  
 
edit your configuration {{ic|/etc/vsftpd.conf}}
 
edit your configuration {{ic|/etc/vsftpd.conf}}
Line 129: Line 135:
 
rsa_private_key_file=/etc/ssl/certs/vsftpd.pem
 
rsa_private_key_file=/etc/ssl/certs/vsftpd.pem
 
</pre>
 
</pre>
 +
 +
=== Dynamic DNS ===
 +
Make sure you put the following two lines in {{ic|/etc/vsftpd.conf}}:
 +
pasv_addr_resolve=YES
 +
pasv_address=yourdomain.noip.info
 +
It is '''not''' necessary to use a script that updates pasv_address periodically and restarts the server, as it can be found elsewhere!
 +
{{Note|You won't be able to connect in passive mode via LAN anymore. Try the active mode on your LAN PC's FTP client.}}
 +
 +
 +
=== Port configurations ===
 +
Especially for private FTP servers that are exposed to the web it's recommended to change the listening port to something other that the standard port 21. This can be done using the following lines in {{ic|/etc/vsftpd.conf}}:
 +
listen_port=2211
 +
Furthermore a custom passive port range can be given by:
 +
pasv_min_port=49152
 +
pasv_max_port=65534
 +
 +
=== Configuring iptables ===
 +
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 2211 -j ACCEPT
 +
This article won't 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 ''ip_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, ''ip_conntrack_ftp'' is required. To load it automatically on boot create a new file in {{ic|/etc/modules-load.d}} e.g.:
 +
# echo ip_conntrack_ftp > /etc/modules-load.d/ip_conntrack_ftp.conf
 +
 +
If you changed the ''listen_port'' you also need to configure the conntrack module accordingly:
 +
{{hc|/etc/modprobe.d/ip_conntrack_ftp.conf|<nowiki>
 +
options nf_conntrack_ftp ports=2211
 +
options ip_conntrack_ftp ports=2211</nowiki>}}
  
 
== Tips and tricks ==
 
== Tips and tricks ==
Line 152: Line 186:
 
Make virtual the owner:
 
Make virtual the owner:
 
  # chown virtual:virtual /srv/ftp
 
  # chown virtual:virtual /srv/ftp
Configure vsftpd to use the created environment by editing /etc/vsftpd.conf. These are the necessary settings to make vsftpd restrict access to virtual users, by user-name and password, and restrict their access to the specified area {{ic|/srv/ftp}}:
+
Configure vsftpd to use the created environment by editing {{ic|/etc/vsftpd.conf}}. These are the necessary settings to make vsftpd restrict access to virtual users, by user-name and password, and restrict their access to the specified area {{ic|/srv/ftp}}:
 
  anonymous_enable=NO
 
  anonymous_enable=NO
 
  local_enable=YES
 
  local_enable=YES
Line 172: Line 206:
  
 
== Troubleshooting ==
 
== Troubleshooting ==
 +
 +
=== vsftpd: no connection (Error 500) with recent kernels (3.5 and newer) and .service ===
 +
add this to your /etc/vsftpd.conf
 +
seccomp_sandbox=NO
  
 
=== vsftpd: refusing to run with writable root inside chroot() ===
 
=== vsftpd: refusing to run with writable root inside chroot() ===
Line 185: Line 223:
 
Install vsftpd-ext from AUR and set in the conf file allow_writable_root=YES
 
Install vsftpd-ext from AUR and set in the conf file allow_writable_root=YES
  
== More resources ==
+
=== FileZilla Client: GnuTLS error -8 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.[http://ramblings.linkerror.com/?p=45]
 +
 
 +
=== vsftpd.service fails to run on boot ===
 +
If you have enabled the vsftpd service and it fails to run on boot, make sure it is set to load after network.target in the service file:
 +
 
 +
{{hc|/usr/lib/systemd/system/vsftpd.service|2=
 +
[Unit]
 +
Description=vsftpd daemon
 +
After=network.target
 +
}}
 +
 
 +
== See also ==
 
* [http://vsftpd.beasts.org/ vsftpd official homepage]
 
* [http://vsftpd.beasts.org/ vsftpd official homepage]
 
* [http://vsftpd.beasts.org/vsftpd_conf.html vsftpd.conf man page]
 
* [http://vsftpd.beasts.org/vsftpd_conf.html vsftpd.conf man page]

Revision as of 16:53, 2 September 2013

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

Installation

Simply install vsftpd from the Official Repositories.

To start the server:

# systemctl start vsftpd.service

If you want it to be started automatically at boot:

# systemctl enable vsftpd.service

See the xinetd section below for procedures to use vsftpd with 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, one can man vsftpd.conf (5). Files are served by default from /srv/ftp.

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 to /etc/vsftpd.conf to allow users in /etc/passwd to login:

local_enable=YES

Anonymous login

The line in /etc/vsftpd.conf controls whether anonymous users can login:

# Allow anonymous login
anonymous_enable=YES
# 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

One can set up a chroot environment which prevents the user from leaving its home directory. 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, one can 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's 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

One can limit the data transfer rate, number of clients and connections per IP for local users 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

Tango-view-refresh-red.pngThis article or section is out of date.Tango-view-refresh-red.png

Reason: Contains reference to rc.conf, which does not exist anymore. (Discuss in Talk:Very Secure FTP Daemon#)

If you want to use vsftpd with xinetd, add the following lines to /etc/xinetd.d/vsftpd:

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

The option below should be set in /etc/vsftpd.conf:

pam_service_name=ftp

Finally, add xinetd to your daemons line in /etc/rc.conf. You do not need to add vsftpd, as it will be called by xinetd whenever necessary.

If you get errors like this while connecting to the server:

500 OOPS: cap_set_proc

You need to add capability in MODULES= line in /etc/rc.conf.

While upgrading to version 2.1.0 you might get an error like this when connecting to the server from a client:

500 OOPS: could not bind listening IPv4 socket

In earlier versions it has been enough to leave the following lines commented:

# Use this to use vsftpd in standalone mode, otherwise it runs through (x)inetd
# listen=YES

In this newer version, and maybe future releases, it is necessary however to explicitly configure it to not run in a standalone mode, like this:

# Use this to use vsftpd in standalone mode, otherwise it runs through (x)inetd
listen=NO

Using SSL to Secure FTP

Generate an SSL Cert, e.g. like that:

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

You will be asked a lot of Questions about your Company etc., as your Certificate is not a trusted one it doesn't really matter what you fill in. You will use this for encryption! If you plan to use this in a matter of trust get one from a CA like thawte, verisign etc.

edit your configuration /etc/vsftpd.conf

#this is important
ssl_enable=YES

#choose what you like, if you accept anon-connections
# you may want to enable this
# allow_anon_ssl=NO

#choose what you like,
# it's a matter of performance i guess
# force_local_data_ssl=NO

#choose what you like
force_local_logins_ssl=YES

#you should at least enable this if you enable ssl...
ssl_tlsv1=YES
#choose what you like
ssl_sslv2=YES
#choose what you like
ssl_sslv3=YES
#give the correct path to your currently generated *.pem file
rsa_cert_file=/etc/ssl/certs/vsftpd.pem
#the *.pem file contains both the key and cert
rsa_private_key_file=/etc/ssl/certs/vsftpd.pem

Dynamic DNS

Make sure you put the following two lines in /etc/vsftpd.conf:

pasv_addr_resolve=YES
pasv_address=yourdomain.noip.info

It is not necessary to use a script that updates pasv_address periodically and restarts the server, as it can be found elsewhere!

Note: You won't be able to connect in passive mode via LAN anymore. Try the active mode on your LAN PC's FTP client.


Port configurations

Especially for private FTP servers that are exposed to the web it's recommended to change the listening port to something other that the standard port 21. This can be done using the following lines in /etc/vsftpd.conf:

listen_port=2211

Furthermore a custom passive port range can be given by:

pasv_min_port=49152
pasv_max_port=65534

Configuring iptables

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 2211 -j ACCEPT

This article won't 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 ip_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, ip_conntrack_ftp is required. To load it automatically on boot create a new file in /etc/modules-load.d e.g.:

# echo ip_conntrack_ftp > /etc/modules-load.d/ip_conntrack_ftp.conf

If you changed the listen_port you also need to configure the conntrack module accordingly:

/etc/modprobe.d/ip_conntrack_ftp.conf
options nf_conntrack_ftp ports=2211
options ip_conntrack_ftp ports=2211

Tips and tricks

PAM with virtual users

Using virtual users has the advantage of not requiring a real login account on the system. Keeping the environment in a container is of course a more secure option.

A virtual users database has to be created by first making a simple text file like this:

user1
password1
user2
password2

Include as many virtual users as you wish according to the structure in the example. Save it as logins.txt; the file name does not have any significance. Next step depends on Berkeley database system, which is included in the core system of Arch. As root create the actual database with the help of the logins.txt file, or what you chose to call it:

# db_load -T -t hash -f logins.txt /etc/vsftpd_login.db

It is recommended to restrict permissions for the now created vsftpd_login.db file:

# chmod 600 /etc/vsftpd_login.db
Warning: Be aware that stocking passwords in plain text is not safe. Don't forget to remove your temporary file with rm logins.txt.

PAM should now be set to make use of vsftpd_login.db. To make PAM check for user authentication create a file named ftp in the /etc/pam.d/ directory with the following information:

auth required pam_userdb.so db=/etc/vsftpd_login crypt=hash 
account required pam_userdb.so db=/etc/vsftpd_login crypt=hash
Note: We use /etc/vsftpd_login without .db extension in PAM-config!

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

Configure vsftpd to use the created environment by editing /etc/vsftpd.conf. These are the necessary settings to make vsftpd restrict access to virtual users, by user-name and password, and restrict their access to the specified area /srv/ftp:

anonymous_enable=NO
local_enable=YES
chroot_local_user=YES
guest_enable=YES
guest_username=virtual
virtual_use_local_privs=YES

If the xinetd method is used start the service. You should now only be allowed to login by user-name and password according to the made database.

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

Troubleshooting

vsftpd: no connection (Error 500) with recent kernels (3.5 and newer) and .service

add this to your /etc/vsftpd.conf

seccomp_sandbox=NO

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. To do this:

# chmod a-w /home/user

Workaround: 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

or alternative:

Install vsftpd-ext from AUR and set in the conf file allow_writable_root=YES

FileZilla Client: GnuTLS error -8 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]

vsftpd.service fails to run on boot

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

/usr/lib/systemd/system/vsftpd.service
[Unit]
Description=vsftpd daemon
After=network.target

See also