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TUCoPS :: Unix :: General :: unix5586.htm

Sun RPC type services remote overflow



1st Aug 2002 [SBWID-5586]
COMMAND

	Sun RPC type services remote overflow

SYSTEMS AFFECTED

	All ?

PROBLEM

	 Editor's note : Would you think the SUN RPC code is found solely on unix, eh ?

	 =============

	

	ISS X-Force has releases a Security Advisory, where they state to  exist
	a buffer overflow in the 'xdr_array' primitive of the Sun RPC code :
	

	http://bvlive01.iss.net/issEn/delivery/xforce/alertdetail.jsp?oid=20823

	

	

	 Update (02 August 2002)

	 ======

	

	Charles Hannum further analyses :
	

	The scope of this bug is somewhat limited. It depends  on  a  particular
	multiplication overflowing:
	

	        nodesize = c * elsize;

	

	In    order    for     this     to     happen,     you     must     have
	maxsize>max(nodesize)*elsize; otherwise the c>maxsize check  will  catch
	it.  Hence the patch:
	

	-       if ((c > maxsize) && (xdrs->x_op != XDR_FREE)) {

	+       if ((c > maxsize || UINT_MAX/elsize < c) &&

	+           (xdrs->x_op != XDR_FREE)) {

	

	In practice, there are only two ways that this constraint is violated:
	

	1) An application explicitly passes in a large maxsize.  I generally
	   consider this an application bug, in the same vain as sending bogus

	   arguments to calloc(), fread()/fwrite() or qsort().  However, amd

	   and various amd utilities -- amd, amq, pawd, and probably others --

	   pass in a maxsize ~0 (i.e. all-1s) and are therefore susceptible.

	

	2) A program uses rpcgen with unbounded arrays; e.g. in rex.x:
	

	        rexstring rst_cmd<>;    /* list of command and args */

	        rexstring rst_env<>;    /* list of environment */

	

	(Note that nothing in our source tree actually  *uses*  rex.x,  but  the
	same problems occurs in rusers.x.)
	

	There are only a few  things  in  our  source  tree  that  actually  use
	xdr_array():
	

	/usr/src/dist/am-utils/amd/amq_subr.c

	/usr/src/dist/am-utils/amq/amq_xdr.c

	/usr/src/dist/am-utils/libamu/xdr_func.c

	/usr/src/gnu/dist/toolchain/gdb/vx-share/xdr_ld.c

	/usr/src/gnu/dist/toolchain/gdb/vx-share/xdr_rdb.c

	/usr/src/lib/libc/rpc/authunix_prot.c

	/usr/src/lib/librpcsvc/rnusers.x 

	/usr/obj.i386/lib/librpcsvc/rex.c

	/usr/obj.i386/lib/librpcsvc/rnusers.c

	/usr/obj.i386/lib/librpcsvc/rusers.c 

	/usr/obj.i386/usr.sbin/rpc.pcnfsd/pcnfsd_xdr.c

	

	The GDB stuff and rex.c are not actually linked into anything. The  uses
	in authunix_prot.c, rnusers.c  and  pcnfsd_xdr.c  are  all  sufficiently
	bounded. Ergo, the only vulnerable programs are amd/amq/etc. and  rusers
	(the client, not the server).
	

	 Update (05 August 2002)

	 ======

	

	david evlis reign found that the kerberos code is vulnerable too :
	

	

	/usr/home/dreign/useless/krb5-1.1-current/src/lib/rpc/xdr_array.c :

	

	/*

	* XDR an array of arbitrary elements

	* *addrp is a pointer to the array, *sizep is the number of elements.

	* If addrp is NULL (*sizep * elsize) bytes are allocated.

	* elsize is the size (in bytes) of each element, and elproc is the

	* xdr procedure to call to handle each element of the array.

	*/

	

	

	Further on, in MIT krb5 security advisory :
	

	There is an integer overflow bug in the SUNRPC-derived RPC library  used
	by the Kerberos 5 administration system that could be exploited to  gain
	unauthorized root access  to  a  KDC  host.  It  is  believed  that  the
	attacker needs to be able to authenticate to the kadmin daemon for  this
	attack to be successful.
	

	-Also-
	

	Ricardo Quesada suspects (all?) releases of libc to be affectecd :
	

	glibc-2.2.5/sunrpc/xdr_array.c

	

	

	 Update (07 August 2002)

	 ======

	

	FreeBSD advisory [FreeBSD-SA-02:36.nfs] informs that the NFS service  is
	based on SUN RPC, and is also affected by the bug.
	

	A part of the  NFS  server  code  charged  with  handling  incoming  RPC
	messages had an error which, when the server received a message  with  a
	zero-length payload, would cause it to reference the  payload  from  the
	previous message, creating a loop  in  the  message  chain.  This  would
	later cause an infinite loop in a different part of the NFS server  code
	which tried to traverse the chain.
	

	

	 Update (13 August 2002)

	 ======

	

	From                         Entercept                          Ricochet
	[http://www.entercept.com/news/uspr/08-12-02.asp]  we  learn  that   the
	Tooltalk RPC service found on most mainframe Unix is vulnerable via  the
	_TT_CREATE_FILE procedure.
	

	

	 Update (14 August 2002)

	 ======

	

	Martin   Schulze   in   Debian    Security    advisory    [DSA    149-1]
	[http://www.debian.org/security/] informs us that libc  also  holds  the
	bad code :
	

	An integer overflow bug has been discovered in the RPC library  used  by
	GNU libc, which is derived from the SunRPC library. This  bug  could  be
	exploited to gain unauthorized root access to software linking  to  this
	code. The packages below also fix integer overflows in the malloc  code.
	They also contain a fix from Andreas  Schwab  to  reduce  linebuflen  in
	parallel to bumping up the buffer pointer in the NSS DNS code.

SOLUTION

	FreeBSD :
	

	# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-02:34/rpc.patch

	# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-02:34/rpc.patch.asc

	

	

	NetBSD patch is out check :
	

	http://www.NetBSD.ORG/Security/

	

	

	Kerberos :
	

	Apply the following patch to src/lib/rpc/xdr_array.c:
	

	Index: xdr_array.c

	===================================================================

	RCS file: /cvs/krbdev/krb5/src/lib/rpc/xdr_array.c,v

	retrieving revision 1.5

	diff -c -r1.5 xdr_array.c

	*** xdr_array.c	1998/02/14 02:27:23	1.5

	- --- xdr_array.c	2002/08/02 17:25:05

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

	*** 75,81 ****

	  		return (FALSE);

	  	}

	  	c = *sizep;

	! 	if ((c > maxsize) && (xdrs->x_op != XDR_FREE)) {

	  		return (FALSE);

	  	}

	  	nodesize = c * elsize;

	- --- 75,82 ----

	  		return (FALSE);

	  	}

	  	c = *sizep;

	! 	if ((c > maxsize || c > LASTUNSIGNED / elsize)

	! 	    && (xdrs->x_op != XDR_FREE)) {

	  		return (FALSE);

	  	}

	  	nodesize = c * elsize;

	

	and rebuild your tree.  The  patch  was  generated  against  krb5-1.2.5;
	patches to other releases may apply with some offset.
	

	This patch may also be found at:
	

	http://web.mit.edu/kerberos/www/advisories/2002-001-xdr_array_patch.txt

	

	

	 Update (06 August 2002)

	 ======

	

	OpenAFS is vulerable, here's the patch :
	

	The OpenAFS project recommends that all users upgrade to  OpenAFS  1.2.6
	or newer. The latest stable OpenAFS release  is  always  available  from
	http://www.openafs.org/release/latest.html.
	

	No update is presently available for the OpenAFS-unstable series.
	

	For those who are unable  to  upgrade,  apply  the  following  patch  to
	correct the XDR vulnerability, and rebuild your tree.
	

	===================================================================

	RCS file: /cvs/openafs/src/rx/Makefile.in,v

	retrieving revision 1.4.2.1

	retrieving revision 1.4.2.2

	diff -u -r1.4.2.1 -r1.4.2.2

	- --- openafs/src/rx/Makefile.in	2002/01/20 08:38:38	1.4.2.1

	+++ openafs/src/rx/Makefile.in	2002/08/02 02:45:14	1.4.2.2

	@@ -38,7 +38,7 @@

	 # Generic xdr objects (or, at least, xdr stuff that's not newly defined for rx).

	 # Really the xdr stuff should be in its own directory.

	 #

	- -XDROBJS = xdr_arrayn.o xdr_rx.o xdr_afsuuid.o

	+XDROBJS = xdr.o xdr_array.o xdr_arrayn.o xdr_rx.o xdr_afsuuid.o

	 

	 RXOBJS = rx_clock.o rx_event.o rx_user.o rx_lwp.o rx.o rx_null.o rx_globals.o 

	 	rx_getaddr.o rx_misc.o rx_packet.o rx_rdwr.o  rx_trace.o rx_conncache.o 

	===================================================================

	RCS file: /cvs/openafs/src/rx/xdr.c,v

	retrieving revision 1.4

	retrieving revision 1.5

	diff -u -r1.4 -r1.5

	- --- openafs/src/rx/xdr.c	2002/06/08 04:43:38	1.4

	+++ openafs/src/rx/xdr.c	2002/07/31 23:13:09	1.5

	@@ -558,6 +558,8 @@

	 	u_int size;

	 	u_int nodesize;

	 

	+        if (maxsize > ((~0) >> 1) - 1) maxsize = ((~0) >> 1) - 1;

	+

	 	/*

	 	 * first deal with the length since xdr strings are counted-strings

	 	 */

	===================================================================

	RCS file: /cvs/openafs/src/rx/xdr_array.c,v

	retrieving revision 1.4

	retrieving revision 1.5

	diff -u -r1.4 -r1.5

	- --- openafs/src/rx/xdr_array.c	2001/08/08 00:03:57	1.4

	+++ openafs/src/rx/xdr_array.c	2002/07/31 23:13:09	1.5

	@@ -84,7 +84,10 @@

	 	register caddr_t target = *addrp;

	 	register u_int c;  /* the actual element count */

	 	register bool_t stat = TRUE;

	- -	register int nodesize;

	+	register u_int nodesize;

	+

	+        i = ((~0) >> 1) / elsize;

	+        if (maxsize > i) maxsize = i;

	 

	 	/* like strings, arrays are really counted arrays */

	 	if (! xdr_u_int(xdrs, sizep)) {

	===================================================================

	RCS file: /cvs/openafs/src/rx/xdr_arrayn.c,v

	retrieving revision 1.4

	retrieving revision 1.5

	diff -u -r1.4 -r1.5

	- --- openafs/src/rx/xdr_arrayn.c	2001/08/08 00:03:57	1.4

	+++ openafs/src/rx/xdr_arrayn.c	2002/07/31 23:13:09	1.5

	@@ -89,7 +89,10 @@

	 	register caddr_t target = *addrp;

	 	register u_int c;  /* the actual element count */

	 	register bool_t stat = TRUE;

	- -	register int nodesize;

	+	register u_int nodesize;

	+

	+        i = ((~0) >> 1) / elsize;

	+        if (maxsize > i) maxsize = i;

	 

	 	/* like strings, arrays are really counted arrays */

	 	if (! xdr_u_int(xdrs, sizep)) {

	===================================================================

	

	This patch may also be found at:
	

	    http://www.openafs.org/security/xdr-updates-20020731.delta

	

	

	 Update (13 August 2002)

	 ======

	

	As          for          the          Tooltalk          RPC          see
	http://www.cert.org/advisories/CA-2002-26.html
	

	 Update (14 Auguts 2002)

	 ======

	

	Get glibc version 2.1.3-23 see the diff below :
	

	http://security.debian.org/pool/updates/main/g/glibc/glibc_2.1.3-23.diff.gz

	


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