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MIMEDEFANG(8)		    System Manager's Manual		 MIMEDEFANG(8)

NAME
       mimedefang - Sendmail MIME mail filter

SYNOPSIS
       mimedefang prcap

       mimedefang -p connection	-m mx_socket_name -U user [options]

DESCRIPTION
       mimedefang is a filter built around Sendmail 8.11's milter API for mail
       filters.	 It collects each incoming message and runs a  filter  on  the
       message.	  This is useful for deleting attachments which	may be a secu-
       rity risk on poorly-designed systems like Microsoft Windows.

       mimedefang does not actually run	the Perl filter; instead, it  communi-
       cates  with  mimedefang-multiplexor(8), which manages a pool of persis-
       tent Perl processes.  See the mimedefang-multiplexor man	page for addi-
       tional information.

OPTIONS
       If  you invoke mimedefang with the single argument prcap, it prints in-
       formation about the version of Milter it	is linked against  and	exits.
       Otherwise,  you should invoke mimedefang	as shown in the	second line of
       the SYNOPSIS.

       -U user
	      Runs mimedefang as user rather than  root.   The	user  argument
	      must match the argument to mimedefang-multiplexor's -U option as
	      well.

       -y     If the -y	command-line option is	given,	MIMEDefang  will  call
	      smfi_setsymlist  to set the list of macros it wants.  This func-
	      tion leaked memory in versions of	Sendmail prior to 8.14.4 so by
	      default  we do not call it.  If you are running an older version
	      of sendmail, you should explicitly set the list  of  macros  you
	      want in the Sendmail configuration file.

       -z spooldir
	      Set the spool directory to spooldir.  If this option is omitted,
	      the spool	directory defaults to /var/spool/MIMEDefang.

       -p connection
	      The -p switch is required	and specifies  the  milter  connection
	      type.  Typically,	you should run mimedefang on the same computer
	      as sendmail.  Therefore, you should use a	UNIX-domain socket for
	      the  connection  type.  The suggested value for the -p switch is
	      mimedefang.sock under the	spool directory.

       -m mx_socket_name
	      Specifies	the socket for	communicating  with  mimedefang-multi-
	      plexor(8).   The	mx_socket_name specifies the path of the UNIX-
	      domain socket.  See mimedefang-multiplexor(8) for	details.

       -b backlog
	      Sets the "backlog" argument to  the  listen(2)  system  call  to
	      backlog.	 If  this option is omitted, then the operating-system
	      default backlog is used.

       -G     Normally,	mimedefang uses	a umask	of 077 when creating the  mil-
	      ter  socket and files.  If you would like	the socket to be read-
	      able and writeable by the	group and files	to be  group-readable,
	      supply  the -G option.  This causes the umask to be 007 whenever
	      UNIX-domain sockets are created and 027 whenever files are  cre-
	      ated.   Note:  if	 your  milter  library	is too old to have the
	      smfi_opensocket()	function, the -G option	causes	mimedefang  to
	      use a umask of 007 throughout its	execution.

	      Note that	by default, /var/spool/MIMEDefang is created with mode
	      0700.  If	you use	the -G option, you probably should change  the
	      mode to 0750.

       -d     The  -d  switch  causes  mimedefang  not to delete the temporary
	      spool files it creates for incoming messages.  This is  for  de-
	      bugging  purposes	 only and should never be used on a production
	      mail server.

       -r     Causes mimedefang	to perform a relay check before	processing any
	      messages.	  It  calls  into a user-supplied Perl function	called
	      filter_relay with	the IP address and host	name  of  the  sending
	      relay.  (See mimedefang-filter(5)	for details.)

       -H     Causes  mimedefang to perform a HELO check before	processing any
	      messages.	 It calls into a user-supplied	Perl  function	called
	      filter_helo with the IP address and host name of the sending re-
	      lay, and the HELO	argument.  (See	mimedefang-filter(5)  for  de-
	      tails.)

       -s     Causes  mimedefang  to  perform a	sender check before processing
	      the message body.	 It calls into a user-supplied	Perl  function
	      called  filter_sender  with  the envelope	address	of the sender.
	      (See mimedefang-filter(5)	for details.)

       -t     Causes mimedefang	to perform recipient checks before  processing
	      the  message  body.  It calls into a user-supplied Perl function
	      called filter_recipient with the envelope	address	of each	recip-
	      ient.  (See mimedefang-filter(5) for details.)

       -q     Permits  the multiplexor to queue	new connections.  See the sec-
	      tion QUEUEING REQUESTS in	the mimedefang-multiplexor  man	 page.
	      Note  that this option and the -R	option are mutually-exclusive.
	      If you supply -q,	then -R	is ignored.

       -k     Causes mimedefang	not to delete working directories if a	filter
	      fails.  This lets	you obtain the message which caused the	filter
	      to fail and determine what went wrong.  mimedefang logs the  di-
	      rectory containing the failed message using syslog.

       -P fileName
	      Causes mimedefang	to write its process-ID	(after becoming	a dae-
	      mon) to the specified file.  The file will be owned by root.

       -o fileName
	      Causes mimedefang	to use fileName	as a lock file to avoid	multi-
	      ple  instances  from running.  If	you supply -P but not -o, then
	      mimedefang constructs a lock file	by appending  ".lock"  to  the
	      pid file.	 However, this is less secure than having a root-owned
	      pid file in a root-owned directory and a lock file  writable  by
	      the  user	 named	by  the	 -U  option.   (The  lock file must be
	      writable by the -U user.)

       -R num Normally,	mimedefang tempfails a new SMTP	 connection  if	 there
	      are  no free workers.  Supplying the -R num option makes mimede-
	      fang tempfail new	connections if there are fewer than  num  free
	      workers, unless the connection is	from the local host.  This al-
	      lows you to favour connections from localhost  so	 your  client-
	      mqueue  doesn't  build  up.   Note that supplying	-R 0 is	subtly
	      different	from omitting the option;  in  this  case,  mimedefang
	      permits new connections from localhost to	queue, but not connec-
	      tions from other hosts (unless you also supply the -q option.)

	      The purpose of the -R option is to reserve resources for client-
	      mqueue  runs.   Otherwise,  on  a	very busy mail server, client-
	      mqueue runs can starve for a long	time, leading  to  delays  for
	      locally-generated	 or streamed mail.  We recommend using a small
	      number for num; probably no more than 3 or 10% of	the total num-
	      ber of workers (whichever	is smaller.)

	      Note  that this option and the -q	option are mutually-exclusive.
	      If you supply -q,	then -R	is ignored.

       -C     Conserve file descriptors	by opening and closing disk files more
	      often.   (Disk  files  are  never	 held open across Milter call-
	      backs.)  While this shortens the length of time a	file  descrip-
	      tor  is  open, it	also leaves more opportunities for the open to
	      fail.  We	do not recommend the use of this flag except  on  very
	      busy systems that	exhibit	failures due to	a shortage of file de-
	      scriptors.

       -T     Causes mimedefang	to log the run-time of the Perl	 filter	 using
	      syslog.

       -x string
	      Add  string  as the content of the X-Scanned-By: header.	If you
	      set string to the	empty string (i.e. -x ""), then	no  X-Scanned-
	      By: header will be added.

       -X     Do not add an X-Scanned-By: header.  Specifying -X is equivalent
	      to specifying -x "".

       -D     Do not fork into the background and become a  daemon.   Instead,
	      stay  in	the foreground.	 Useful	mainly for debugging or	if you
	      have a supervisory process managing mimedefang.

       -M     This option is obsolete; it is accepted for backward-compatibil-
	      ity, but is ignored.

       -N     Normally,	 mimedefang  sees  all	envelope recipients, even ones
	      that Sendmail knows to be	invalid.  If you don't	want  Sendmail
	      to  perform  a milter callback for recipients it knows to	be in-
	      valid, invoke mimedefang with the	-N  flag.   Please  note  that
	      this  flag only works with Sendmail and Milter 8.14.0 and	newer.
	      It has no	effect if you're running an older version of  Sendmail
	      or Milter.

       -S facility
	      Specifies	 the syslog facility for log messages.	The default is
	      mail.  See openlog(3) for	a list of valid	facilities.   You  can
	      use either the short name	("mail") or long name ("LOG_MAIL") for
	      the facility name.

       -a macro
	      Pass the value of	the specified Sendmail macro  through  to  the
	      Perl  filter.  You can repeat the	-a option to write more	macros
	      than the built-in	defaults.  Note	that  in  addition  to	asking
	      mimedefang  to pass the macro value to the filter, you must con-
	      figure Sendmail to pass the macro	through	 to  mimedefang	 using
	      the  confMILTER_MACROS_ENVFROM  definition in Sendmail's m4 con-
	      figuration file.

       -c     Strip "bare" carriage-returns (CR) characters from  the  message
	      body.   A	 bare  CR  should  never  appear in an e-mail message.
	      Older versions of	mimedefang used	to strip  them	out  automati-
	      cally,  but  now they are	left in	by default.  The -c option en-
	      ables the	older behavior.

       -h     Print usage information and exit.

OPERATION
       When mimedefang starts, it connects to sendmail using the  milter  API.
       (See  the  Sendmail  8.11  documentation.)   For	each incoming message,
       mimedefang creates a temporary directory	and saves information  in  the
       directory.   At various phases during the SMTP conversation, mimedefang
       communicates with mimedefang-multiplexor	to perform various operations.
       mimedefang-multiplexor manages a	pool of	persistent Perl	processes that
       actually	perform	the mail scanning operations.

       When a Perl process scans an e-mail, the	temporary spool	directory con-
       tains  certain  files;  details	of  the	communication protocol between
       mimedefang and the Perl script are in mimedefang-protocol(7).

WARNINGS
       mimedefang does violence	to the flow of e-mail.	 The  Perl  filter  is
       quite  picky  and  assumes  that	 MIME e-mail messages are well-formed.
       While I have tried to make the script safe, I  take  no	responsibility
       for  lost  or mangled e-mail messages or	any security holes this	script
       may introduce.

AUTHOR
       mimedefang was written by Dianne	Skoll  <dfs@roaringpenguin.com>.   The
       mimedefang home page is http://www.mimedefang.org/.

SEE ALSO
       mimedefang.pl(8),    mimedefang-filter(5),   mimedefang-multiplexor(8),
       mimedefang-protocol(7)

4th Berkeley Distribution	8 February 2005			 MIMEDEFANG(8)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERATION | WARNINGS | AUTHOR | SEE ALSO

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