[UNIX] AWHTTPd Local DoS

From: support@securiteam.com
Date: 01/05/02 

From: support@securiteam.com
To: list@securiteam.com
Date: Sat,  5 Jan 2002 20:38:56 +0100 (CET)

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  AWHTTPd Local DoS
------------------------------------------------------------------------

SUMMARY

 <http://hardcoresoftware.cjb.net/awhttpd/> AWHTTPd is a small web server
application.
Local users with access to the HTTP directory can cause a denial of
service attack against the product.

DETAILS

Vulnerable systems:
AWHTTPd 2.2 and earlier versions

Any local user with write access to awhttpd's html directory can crash the
daemon by crafting a special script which is parsed by awhttpd's scripting
engine (this is enabled by default). The offending code exists on line 29
of misc.c:

      if (filefd[i]!= (FILE *) -1) fclose(filefd[i]);

Example:
A sample awhttpd script follows:
# test.cgi
--AWHTTPD SCRIPT--
echo "this is a test"
F:test.html

If test.html doesn't exist in the html directory, awhttpd will crash on
the fclose().

Fix:
Apply the patches below or disable the scripting engine by editing
config.h in the root source directory of awhttpd.

=====[ begin cut here ]=====
--- misc.c.orig Wed Jan 2 16:22:24 2002
+++ misc.c Wed Jan 2 16:26:37 2002
@@ -26,7 +26,7 @@
 
 void discon(int i) {
   close(infd[i]);
- if (filefd[i]!= (FILE *) -1) fclose(filefd[i]);
+ if (filefd[i]!= NULL) fclose(filefd[i]);
   if (sending[i]>0) numofusers--;
   sending[i]=0;
   getreqs[i][0]=0;
=====[ end of misc.c patch ]=====

=====[ begin cut here ]=====
--- procscrpt.c.orig Wed Jan 2 16:27:33 2002
+++ procscrpt.c Wed Jan 2 16:51:47 2002
@@ -38,6 +38,12 @@
   sending[i]=1;
   strcpy(getreqs[i],tpbuf+2);
   stripcrlf(getreqs[i]);
+ if(doesfileexist(getreqs[i]) == 0) {
+ strcpy(tpbuf, "Error: cannot locate ");
+ strncat(tpbuf, getreqs[i], 256);
+ strcat(tpbuf, " for reading!\n");
+ logthis(3, tpbuf);
+ }
   fclose(filefd[i]);
 } else if (tpbuf[0]==0) {
   discon(i);
=====[ end of procscrpt.c patch ]=====

ADDITIONAL INFORMATION

The information has been provided by
<mailto:methodic@slartibartfast.angrypacket.com> methodic.

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