PFTPX(8)                FreeBSD System Manager's Manual               PFTPX(8)

NAME
	 pftpx -- FTP proxy

SYNOPSIS
	 pftpx [-6d] [-b address] [-c port] [-D level] [-f address] [-g port]
	       [-m maxsessions] [-p address] [-q queue] [-t timeout]

DESCRIPTION
	 pftpx is a proxy for the Internet File Transfer Protocol.  FTP control
	 connections should be redirected into the proxy using the pf(4) rdr com-
	 mand, 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 pftpx 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 log quick inet proto tcp \
	       from $server to $client port $port flags S/SAFR keep state

	 In case of passive mode (PASV or EPSV):

	   nat from $client to $server port $port -> $proxy
	   pass log quick inet proto tcp \
	       from $client to $server port $port flags S/SAFR keep state
	   pass log quick inet proto tcp \
	       from $proxy to $server port $port flags S/SAFR keep state

	 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.

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

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

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

	 -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.)

	 -f address
	         Fixed server address.  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.

	 -g port
	         Fixed server port.  Only used in combination with the previous
	         option.  The default is port 21.

	 -m maxsessions
	         Maximum number of concurrent FTP sessions.  When the proxy
	         reaches this limit, new connections are denied.  The default is
	         100.

	 -p address
	         Proxy source address.  The proxy will use this as the source
	         address to connect to servers.

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

	 -t timeout
	         Number of seconds that the control connection can be idle, before
	         the proxy will disconnect.  The default is 24 hours.  Do not set
	         this too low, because the control connection is usually idle when
	         large data transfers are taking place.

CONFIGURATION
	 To make use of the proxy, pf.conf(5) needs the following rules.  All
	 anchors are mandatory.  The rdr pass rule can be adjusted as needed.

	 In the NAT section:

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

	 In the rule section:

	   anchor "pftpx/*"

SECURITY
	 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.

	 pftpx chroots to "/var/empty" and changes to user "proxy" to drop privi-
	 leges.

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

FreeBSD 7.0                    November 28, 2004                   FreeBSD 7.0