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FTP-PROXY(8)		FreeBSD	System Manager's Manual		  FTP-PROXY(8)

NAME
     ftp-proxy -- Internet File	Transfer Protocol proxy	daemon

SYNOPSIS
     ftp-proxy [-6Adrv]	[-a address] [-b address] [-D level] [-m maxsessions]
	       [-P port] [-p port] [-q queue] [-R address] [-T tag]
	       [-t timeout]

DESCRIPTION
     ftp-proxy is a proxy for the Internet File	Transfer Protocol.  FTP	con-
     trol connections should be	redirected into	the proxy using	the pf(4) rdr
     command, after which the proxy connects to	the server on behalf of	the
     client.

     The proxy allows data connections to pass,	rewriting and redirecting them
     so	that the right addresses are used.  All	connections from the client to
     the server	have their source address rewritten so they appear to come
     from the proxy.  Consequently, all	connections from the server to the
     proxy have	their destination address rewritten, so	they are redirected to
     the client.  The proxy uses the pf(4) anchor facility for this.

     Assuming the FTP control connection is from $client to $server, the proxy
     connected to the server using the $proxy source address, and $port	is
     negotiated, then ftp-proxy	adds the following rules to the	various
     anchors.  (These example rules use	inet, but the proxy also supports
     inet6.)

     In	case of	active mode (PORT or EPRT):

       rdr from	$server	to $proxy port $port ->	$client
       pass quick inet proto tcp \
	   from	$server	to $client port	$port

     In	case of	passive	mode (PASV or EPSV):

       nat from	$client	to $server port	$port -> $proxy
       pass in quick inet proto	tcp \
	   from	$client	to $server port	$port
       pass out	quick inet proto tcp \
	   from	$proxy to $server port $port

     The options are as	follows:

     -6	     IPv6 mode.	 The proxy will	expect and use IPv6 addresses for all
	     communication.  Only the extended FTP modes EPSV and EPRT are
	     allowed with IPv6.	 The proxy is in IPv4 mode by default.

     -A	     Only permit anonymous FTP connections.  Either user "ftp" or user
	     "anonymous" is allowed.

     -a	address
	     The proxy will use	this as	the source address for the control
	     connection	to a server.

     -b	address
	     Address where the proxy will listen for redirected	control	con-
	     nections.	The default is 127.0.0.1, or ::1 in IPv6 mode.

     -D	level
	     Debug level, ranging from 0 to 7.	Higher is more verbose.	 The
	     default is	5.  (These levels correspond to	the syslog(3) levels.)

     -d	     Do	not daemonize.	The process will stay in the foreground, log-
	     ging to standard error.

     -m	maxsessions
	     Maximum number of concurrent FTP sessions.	 When the proxy
	     reaches this limit, new connections are denied.  The default is
	     100 sessions.  The	limit can be lowered to	a minimum of 1,	or
	     raised to a maximum of 500.

     -P	port
	     Fixed server port.	 Only used in combination with -R.  The
	     default is	port 21.

     -p	port
	     Port where	the proxy will listen for redirected connections.  The
	     default is	port 8021.

     -q	queue
	     Create rules with queue queue appended, so	that data connections
	     can be queued.

     -R	address
	     Fixed server address, also	known as reverse mode.	The proxy will
	     always connect to the same	server,	regardless of where the	client
	     wanted to connect to (before it was redirected).  Use this	option
	     to	proxy for a server behind NAT, or to forward all connections
	     to	another	proxy.

     -r	     Rewrite sourceport	to 20 in active	mode to	suit ancient clients
	     that insist on this RFC property.

     -T	tag  The filter	rules will add tag tag to data connections, and	not
	     match quick.  This	way alternative	rules that use the tagged key-
	     word can be implemented following the ftp-proxy anchor.  These
	     rules can use special pf(4) features like route-to, reply-to,
	     label, rtable, overload, etc. that	ftp-proxy does not implement
	     itself.

     -t	timeout
	     Number of seconds that the	control	connection can be idle,	before
	     the proxy will disconnect.	 The maximum is	86400 seconds, which
	     is	also the default.  Do not set this too low, because the	con-
	     trol connection is	usually	idle when large	data transfers are
	     taking place.

     -v	     Set the 'log' flag	on pf rules committed by ftp-proxy.  Use twice
	     to	set the	'log-all' flag.	 The pf	rules do not log by default.

CONFIGURATION
     To	make use of the	proxy, pf.conf(5) needs	the following rules.  All
     anchors are mandatory.  Adjust the	rules as needed.

     In	the NAT	section:

       nat-anchor "ftp-proxy/*"
       rdr-anchor "ftp-proxy/*"
       rdr pass	on $int_if proto tcp from $lan to any port 21 -> \
	   127.0.0.1 port 8021

     In	the rule section:

       anchor "ftp-proxy/*"
       pass out	proto tcp from $proxy to any port 21

SEE ALSO
     ftp(1), pf(4), pf.conf(5)

CAVEATS
     pf(4) does	not allow the ruleset to be modified if	the system is running
     at	a securelevel(7) higher	than 1.	 At that level ftp-proxy cannot	add
     rules to the anchors and FTP data connections may get blocked.

     Negotiated	data connection	ports below 1024 are not allowed.

     The negotiated IP address for active modes	is ignored for security	rea-
     sons.  This makes third party file	transfers impossible.

     ftp-proxy chroots to "/var/empty" and changes to user "proxy" to drop
     privileges.

FreeBSD	10.1		       February	26, 2008		  FreeBSD 10.1

NAME | SYNOPSIS | DESCRIPTION | CONFIGURATION | SEE ALSO | CAVEATS

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