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Old 10-10-2008, 07:44 PM   #1
Shwick
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Registered: Jun 2008
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vsftpd PASV + putty port forwarding


I'm trying to set up a secure ftp transfer between my linux machine and my internet gateway running ubuntu 8.04.

I have vsftpd installed but I can't get PASV connection to work with putty. My ubuntu firewall blocks everything except ssh.

From my windows XP machine I establish a connection with putty to my ubuntu machine. I have putty forward local port 21(windows machine) to 127.0.0.1:21(ubuntu machine).

This works sort of. I use the ftp client from windows command line to connect to 127.0.0.1 21, which forwards me to port 21 on the ubuntu machine and allows me to connect/login.

Then after I enter "quote PASV" and try a "dir" command it hangs. In vsftpd.conf I had added lines pasv_max_port=21 and pasv_min_port=21 so that the ftp server would tell the windows ftp client to use port 21 for data transfers.

I then added "pasv_address=127.0.0.1" to vsftpd.conf, thinking vsftp was telling the windows ftp client to try and connect to something other than localhost, and vsftpd wouldn't start, it said I had to edit 2 files.

I already have sftp working with psftp.exe, but I'd like one entry point into my system and psftp doesn't load bash.bashrc, so I want ftp through ssh to work.

See this site for PASV ftp: http://www.slacksite.com/other/ftp.html

Code:
# 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=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
pasv_max_port=21
pasv_min_port=21
pasv_address="127.0.0.1"
#
# 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
log_ftp_protocol=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().
#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
 
Old 10-11-2008, 01:46 AM   #2
checkmate3001
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Registered: Sep 2007
Location: Folsom, California
Distribution: Ubuntu, Mint, Debian, Suse
Posts: 307

Rep: Reputation: 32
I'm nearly 100% sure this:
Code:
pasv_address="127.0.0.1"
Is NOT right. I would remove (comment) that line.

I would edit the firewall to open some very high ports (ie: 55000 to 55500) and change the pasv min and max to those limits. Then if everything works, change it back to 21 and 21. I have a feeling that when using pasv it is conflicting when you tell it to only use port 21. So it may not be possible to use port 21 for pasv. If I remember correctly ftp in pasv wants many (at least a handful) of ports to send data back and forth. I could be wrong.
 
Old 10-11-2008, 01:56 AM   #3
checkmate3001
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Registered: Sep 2007
Location: Folsom, California
Distribution: Ubuntu, Mint, Debian, Suse
Posts: 307

Rep: Reputation: 32
strange... I just tried my vsftp and it was communicating on port 21 just fine. I have my pasv set to the higher ports. If I remember correctly port 21 is just for commands?? data is sent via the pasv ports?
 
Old 10-14-2008, 07:15 PM   #4
Shwick
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Registered: Jun 2008
Posts: 111

Original Poster
Rep: Reputation: 15
Ok I decided to ditch the port forwarding and just get it working normally first. I got it working by opening my local interface through iptables.

In vsftpd.conf I specified a port range of 55000 to 55100 for PASV ports, but vsftpd doesn't use that range.

Using wireshark I captured ftp packets and saw vsftpd sent PASV ports 62237 and 58847 for two different ftp sessions.

Why is it not using the specified range?


Here is a non-commented copy of vsftpd.conf.

listen=YES
anonymous_enable=NO
local_enable=YES
write_enable=YES
pasv_max_port=55000
pasv_min_port=55100
dirmessage_enable=YES
xferlog_enable=YES
connect_from_port_20=YES
log_ftp_protocol=YES
secure_chroot_dir=/var/run/vsftpd
pam_service_name=vsftpd
rsa_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
rsa_private_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
 
Old 10-15-2008, 10:19 PM   #5
Shwick
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Registered: Jun 2008
Posts: 111

Original Poster
Rep: Reputation: 15
I had pasv_max_port=55000 and pasv_min_port=55100 mixed up. Min was higher than max. It's working now.
 
Old 10-18-2008, 04:33 AM   #6
checkmate3001
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Registered: Sep 2007
Location: Folsom, California
Distribution: Ubuntu, Mint, Debian, Suse
Posts: 307

Rep: Reputation: 32
alright! sweet. Good to hear you got it working. Sorry, I've been away for a little while.
 
  


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