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TUCoPS :: Unix :: General :: unix4936.htm

exim pipe



19th Dec 2001 [SBWID-4936]
COMMAND

	exim pipe

SYSTEMS AFFECTED

	3.33 and previous

PROBLEM

	Philip Hazel reported following :
	

	The problem exists only in the case of a run  time  configuration  which
	directs or routes an address to a pipe transport  without  checking  the
	local part of the address in any way. This does not apply, for  example,
	to pipes run from alias or forward files,  because  the  local  part  is
	checked to ensure that it is the name of an alias or of a local user.
	

	One kind of  configuration  where  this  may  apply  is  one  where  all
	incoming mail is sent straight to a virus checker by means  of  a  pipe,
	without  inspecting  the  local  parts   of   addresses.   However,   if
	receiver_verify is turned on, and the director/router that is  used  for
	the pipe has no_verify set, there may not be an  exposure,  because  the
	local parts are  probably  checked  by  the  verification  process  even
	though they are not checked at delivery time before being  sent  to  the
	pipe.
	

	The bug is provoked by routing/directing an  address  whose  local  part
	begins with a pipe symbol (vertical bar) to a pipe  transport.  That  is
	why any configuration in which local parts are  first  checked  in  some
	way is not normally vulnerable  (a  local  part  starting  with  a  pipe
	symbol is normally invalid). The Exim  4  default  configuration  blocks
	local parts that contain any of the characters @%!/| at  SMTP  time,  as
	it happens.
	

	The bug\'s effect is that, instead of obeying the correct pipe  command,
	a broken Exim runs the command encoded in the local part.
	

	

SOLUTION

	Upgrade to exim 3.34, or apply following patches :
	

	

	----------------------------------------------------------------------------

	This patch is for version 3.33. It should also work on all previous versions

	back to 3.20.

	

	*** exim-3.33/src/transports/pipe.c Wed Aug 15 12:09:13 2001

	--- transports/pipe.c	Thu Dec 13 10:25:21 2001

	***************

	*** 487,493 ****

	  pointed to by addr->local_part; it starts with the pipe symbol. In other cases,

	  the command is supplied as one of the pipe transport\'s options. */

	

	! if (addr->local_part[0] == \'|\')

	    {

	    cmd = addr->local_part + 1;

	    while (isspace((uschar)*cmd)) cmd++;

	--- 487,493 ----

	  pointed to by addr->local_part; it starts with the pipe symbol. In other cases,

	  the command is supplied as one of the pipe transport\'s options. */

	

	! if (testflag(addr,af_pfr) && addr->local_part[0] == \'|\')

	    {

	    cmd = addr->local_part + 1;

	    while (isspace((uschar)*cmd)) cmd++;

	----------------------------------------------------------------------------

	

	

	----------------------------------------------------------------------------

	This patch is for versions before 3.20. It should work at least as far back as

	release 3.12 (which was release on December 8, 1999). It may work on earlier

	releases - if not, it is such a simple patch that you should be able to figure

	out what to change by hand.

	

	*** src/transports/pipe.c Wed Aug 15 12:09:13 2001

	--- transports/pipe.c	Thu Dec 13 10:25:21 2001

	***************

	*** 487,493 ****

	  pointed to by addr->local_part; it starts with the pipe symbol. In other cases,

	  the command is supplied as one of the pipe transport\'s options. */

	

	! if (addr->local_part[0] == \'|\')

	    {

	    cmd = addr->local_part + 1;

	    while (isspace((uschar)*cmd)) cmd++;

	--- 487,493 ----

	  pointed to by addr->local_part; it starts with the pipe symbol. In other cases,

	  the command is supplied as one of the pipe transport\'s options. */

	

	! if (addr->pfr && addr->local_part[0] == \'|\')

	    {

	    cmd = addr->local_part + 1;

	    while (isspace((uschar)*cmd)) cmd++;

	----------------------------------------------------------------------------

	

	

	


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