[NEWS] Silc Server and Toolkit Symlink Attack

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  Silc Server and Toolkit Symlink Attack
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SUMMARY

" <http://silcnet.org/> SILC Server enables system administrators to set 
up their own SILC networks. SILC Toolkit is full implementation of the 
SILC protocol and is intended for software and application developers who 
want to integrate SILC support in their products."

Insecure temporary file usage allows local attackers to perform a symlink 
attack on Silc server and toolkit.

DETAILS

Vulnerable Systems:
 * silc-server version 1.0 and prior
 * silc toolkit version 0.9.12-r3 and prior

The vulnerability is caused due to temporary file being created 
insecurely. This can be exploited via symlink attacks in combination to 
create and overwrite arbitrary files with the privileges of the user 
running the affected script.

Vulnerable code:
silcd/silcd.c:
258 /* Dump server statistics into a file into /tmp directory */
259
260 SILC_TASK_CALLBACK(dump_stats)
261 {
262   FILE *fdd;
263   char filename[256];
264
265   memset(filename, 0, sizeof(filename));
266   snprintf(filename, sizeof(filename) - 1, "/tmp/silcd.%d.stats", 
getpid());
267   fdd = fopen(filename, "w+");
268   if (!fdd)
269     return;
270
271 #define STAT_OUTPUT(fmt, stat) fprintf(fdd, fmt "\n", (int)stat);
272
273   fprintf(fdd, "SILC Server %s Statistics\n\n", silcd->server_name);
274   fprintf(fdd, "Local Stats:\n");

Disclosure Timeline:
Discovered : 2005-05-31
Vendor notified : 2005-06-15
Vendor response : none
Vendor fix : none
Disclosure : 2005-09-01


ADDITIONAL INFORMATION

The information has been provided by  <mailto:[email protected]> Eric 
Romang.
The original article can be found at:  
<http://www.zataz.net/adviso/silc-server-toolkit-06152005.txt> 
http://www.zataz.net/adviso/silc-server-toolkit-06152005.txt



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