LSS Security Advisory #LSS-2005-03-04
             http://security.lss.hr

---

Title      :  Ethereal remote buffer overflow
Advisory ID    :  LSS-2005-03-04
Date      :  08.03.2005 
Advisory URL:    :  http://security.lss.hr/en/index.php?page=exp 
Impact      :  Stack overflow and possible code execution
Risk level    :  High 
Vulnerability type  :  Remote 
Vendors contacted  :  Yes

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===[ Overview 

Ethereal is used by network professionals around the world for troubleshooting, 
analysis, software and protocol development, and education. It has all of the 
standard features  you would expect in a protocol analyzer, and several 
features not seen in any other product. Its open source license allows talented 
experts in the networking community to add enhancements. It runs on all popular 
computing platforms, including Unix, Linux, and Windows.



===[ Vulnerability

There is remote buffer overflow vulnerability in Ethereal dissector for 
CDMA2000 A11 packets. Vulnerability is located in dissect_a11_radius() function 
in packet-3g-a11.c used for RADIUS authentication dissection. Number of bytes 
that will be copied from packet to buffer in stack is taken from packet itself. 
16 bytes are reserved for that buffer, and string length can be up to 256 bytes 
(unsigned char), so is possible to overflow local variables and return address. 


packet-3g-a11.c:
----------------
#define MAX_STRVAL 16
...
dissect_a11_radius( tvbuff_t *tvb, int offset, proto_tree *tree, int app_len)
{
...
  size_t     radius_len;
  ...
  guchar     str_val[MAX_STRVAL]; 
  ...
  radius_len = tvb_get_guint8(tvb, offset + 1);
  ...
  strncpy(str_val, tvb_get_ptr(tvb,offset+2,radius_len-2), radius_len-2); 
...
}
----------------

A similar vulnerability was also found in same function few lines below where 
RADIUS attributes are copied to stack.

packet-3g-a11.c:
----------------
#define MAX_STRVAL 16
...
dissect_a11_radius( tvbuff_t *tvb, int offset, proto_tree *tree, int app_len)
{
...
  guint      attribute_len;
  ...
  guchar     str_val[MAX_STRVAL];
  ...
  attribute_len = tvb_get_guint8(tvb, offset + radius_offset + 1);
  ...
  case ATTR_TYPE_STR:
  strncpy(str_val,tvb_get_ptr(tvb,offset+radius_offset+2,attribute_len - 2),
         attribute_len - 2); 

...
}
----------------



===[ Affected versions

All versions after 3G-A11 dissector was added to CVS including latest 0.10.9.
Vulnerability was tested with latest Ethereal on Linux and Windows.



===[ Fix

It seems that that they have fixed that vulnerability just few days ago, 
and new version will probably be available soon from http://www.ethereal.com.



===[ PoC Exploit

Exploit is in attachment, and URL http://security.lss.hr/en/PoC/ 



===[ Credits

Credits for this vulnerability goes to Leon Juranic. 



===[ LSS Security Contact
 
 LSS Security Team, <eXposed by LSS>
 
 WWW    : http://security.lss.hr
 E-mail : security@LSS.hr
 Tel  : +385 1 6129 775