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Openswan XAUTH/PAM Buffer Overflow Vulnerability



Openswan is an open source implementation of IPSEC for the Linux
Operating System. Openswan is based on the discontinued FreeS/WAN

More information is available on the vendor's website:


Remote exploitation of a stack based buffer overflow vulnerability in
Xelerance Corp.'s Openswan could allow attackers to execute arbitrary

The vulnerability specifically exists due to a lack of bounds checking
in the pluto application when Openswan is compiled with XAUTH and PAM
support. The get_internal_addresses() function in
programs/pluto/xauth.c allocates a small character array and copies an
overly long user controlled buffer into the array as seen below. The
resulting stack overflow may be leveraged to execute arbitrary code
with permissions of the pluto process.

in programs/pluto/id.h:

47:  #define IDTOA_BUF 512

in programs/pluto/xauth.c:

148: #ifdef XAUTH_USEPAM
149: int retval;
150: char str[48];
151: #endif
169: if(retval == PAM_SUCCESS)
170: {
171:  char buf[IDTOA_BUF];
185:  sprintf(str,"ID=%s", buf);


Successful exploitation of the vulnerability can allow remote attackers
to execute code with privileges of the pluto process. Exploitation in
the wild will be limited due to the fact that Openswan would need to be
compiled with XAUTH and PAM options enabled which are both disabled by
default. In addition, exploitation occurs after an IKE Phase-1 Security
Association (SA) has been established which requires authentication of
a shared key and the supplied client certificate, further reducing the
impact of this vulnerability.


iDEFENSE has confirmed that Openswan 2.2.0 is vulnerable. All previous
versions of Openswan also contain the vulnerable code.


The XAUTH and PAM configuration options can be found in Makefile.inc in
the Openswan source tree. Disable both configuration options or apply
the following vendor-supplied patch:

Index: xauth.c
RCS file: /xelerance/master/openswan-2/programs/pluto/xauth.c,v
retrieving revision 1.35
diff -u -p -u -r1.35 xauth.c
- --- xauth.c 30 Nov 2004 15:30:24 -0000 1.35
+++ xauth.c 8 Jan 2005 02:25:35 -0000
@@ -187,7 +187,7 @@ int get_internal_addresses(struct connec  { 
     int retval;
- -    char str[48];
+    char str[IDTOA_BUF+sizeof("ID=")+2];

 #ifdef NAT_TRAVERSAL /* only NAT-T code lets us do virtual ends */
@@ -222,7 +222,7 @@ int get_internal_addresses(struct connec
          memmove(buf, c1+3,
strlen(c1) + 1 - 3);
- -       sprintf(str,"ID=%s", buf);
+       snprintf(str, sizeof(str), "ID=%s", buf);


The vendor has addressed this vulnerability in newly released Openswan
packages. Users should upgrade to Openswan 1.0.9 or Openswan 2.3.0
depending on their current configuration. New packages are available
from the following link:



 The Common Vulnerabilities and Exposures (CVE) project has assigned the
names CAN-2005-0162 to these issues. This is a candidate for inclusion
in the CVE list (http://cve.mitre.org), which standardizes names for
security problems.


01/06/2005   Initial vendor notification
01/06/2005   Initial vendor response
01/26/2005   Public disclosure


The discoverer of this vulnerability wishes to remain anonymous.

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Copyright © 2005 Verisign, Inc.

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at the time of publishing based on currently available information. Use
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