Hack the ROP Primer: 1.0.1 (CTF Challenge)

Hello friends! Today we are going to take another CTF challenge known as ROP Primer. The credit for making this vm machine goes to “Bas” and it is another capture the flag challenge in which our goal is to capture all the flags to complete the challenge. You can download this VM here.

We have 3 levels available here and we are given the login credentials of all of 3 machines which are as follow:

Levels Username Password
Level 0 level0 warmup
Level 1 level1 shodan
Level 2 level2 tryharder

We had one binary per level, which we have to exploit each one to successfully extract flags from them.

You can download all the exploit used from here.

Let’s Breach!!!

Let us start form getting to know the IP of VM (Here, I have it at 192.168.199.139 but you will have to find your own

LEVEL 0:

Now we use the given credentials to login through ssh as user level0. After logging in we find 2 files one executable file called level0 and another file called flag. Both files are owned by level1 user, but the binary file has suid bit set so we can execute it. When we run it we find that it takes a string as input and then outputs a message along with the string.

GDB-peda is provided by the author in the lab so we can directly analyse the binary in the target machine itself. Opening the binary in gdb we find that there is a gets function. Now gets is vulnerable to buffer overflow so we try to exploit it.

We created a 500 bytes long pattern using gdb-peda and used it as input for the binary.

As soon as we passed the string we get a segmentation fault error, we use pattern offset function of gdb-peda to find the EIP offset and find that after 44 bytes we can completely overwrite EIP register.

Now we check for security and find that there is no ASLR but NX is enabled so we cannot execute shellcode on the stack.

As NX is enabled we can still use ret2libc attack to spawn a shell. But when we try to print the memory address of system we find that there is no system so we cannot execute /bin/sh to spawn a shell.

In the description we are given a hint that we can use mprotect to solve this problem.

When we take a look at the man page for mprotect we find that it used to change protection of portions of memory by making it readable, writeable and executable. We also find it takes 3 parameters address, length of the memory that needs to be changes and protection level.

As we can make portions of memory readable, writeable and executable, we are going to use memcpy function to insert our shellcode into the block of memory.

Now need to select which section of the memory we are going to change, so we use gdb to see how the memory is mapped.

We are going to take 0x080ca000 as target memory and we are going to mark 4KB of memory starting from 0x080ca000 as readable, writeable and executable. We create an exploit to this for us.

We save the output of this program in a file called input, we are going to use this as our input for the binary file.

When run the binary in gdb with using the input from our exploit, we take a look at the mapped memory and find that the memory block we selected was marked as readable, writeable and executable.

Now we need to remove mprotect’s parameter from the stack so that we can redirect the flow of execution, mprotect function uses 3 parameters so we need to pop 3 values off the stack so we use ropgadget function in gdb and find a gadget pop3ret at 0x8048882.

Now we create the exploit to get an elevated shell. We use cat to keep the shell alive, we run the exploit and now we can access the flag. We take a look at the content of the file and find our first flag.

LEVEL 1:

After completing level0, we login as level1 using the given credentials. We find a file called flag, bleh and a binary file called level1 with suid bit set. When we run the binary it says that error binding.

We check the listening ports on the target machine and find that port 8888 is open. We check processes with uid 1002 and find it is level1.

We connect it it and find it is an application that can be used to store and read files.

We open the binary in gdb and take a look at the assembly code for further analysis.

We setup a breakpoint on the main function. At main+115 we found that port 8888 is stored on the stack. We changed the value stored in the memory address to port 8889 so that we can run the program.

We create a 128 bytes long pattern using pattern_create.rb script in our system. So that we can pass the string as the name of the file.

After changing the port number, we connected to it and stored a file with 128-byte size.

After mentioning the size of the file, it asks for the file name. We passed the 128 bytes long pattern as the file name.

When we switch to gdb we find that we get a segmentation fault.

We now use the patten_offset.rb script to find the EIP offset.

We are given a hint in the description of this challenge that we can use read, write and open function to open the flag and read it.

We are now going to need ropgadget, we need pop2ret for gadget for open function and pop3ret gadget for read function.

Now if we can get the address of the ‘flag’ string, then we can just read the flag and output it to the connected socket.

We create an exploit to get the flag. We run it and find the flag.

LEVEL 2:

After completing level1, we login as level2 using the given credentials. We find a file called flag and a binary file called level2 with suid bit set. When we run the binary, we find that it takes a string as an argument and then prints it.

We open the file in gdb for further analysis and find that at main+46 it calls strcpy function. As strcpy function is vulnerable to buffer overflow we exploit it.

On further analysis we find that it is similar to level0 binary file, we create a 500 bytes string and pass its argument and find the EIP offset to be 44 bytes.

This binary file has strcpy function instead of gets we cannot use “\x00”. So we use gadgets to do our work. We use ropshell.com to find all the gadgets used in this exploit.

We modified the exploit we created for level0 and inserted our gadgets. We use read function instead of memcpy function in this exploit. (Gadgets are explained in the exploit code).

As soon as we run our exploit we spawn a shell as root user. We open the flag file and get our final flag.

Author: Sayantan Bera is a technical writer at hacking articles and cyber security enthusiast. Contact Here

Hack the Box: Fulcrum Walkthrough

Hello friends!! Today we are going to solve another CTF challenge “Fulcrum” which is available online for those who want to increase their skill in penetration testing and black box testing. Fulcrum is retired vulnerable lab presented by Hack the Box for making online penetration practices according to your experience level; they have the collection of vulnerable labs as challenges from beginners to Expert level.

Level: Expert

Task: find user.txt and root.txt file on victim’s machine.

Since these labs are online available therefore they have static IP and IP of Fulcrum is 10.10.10.62 so let’s begin with nmap port enumeration.

We need to do a nmap version scan so that we can get a better information about the open ports.

From given below image, you can observe that we find ports 4, 22, 80, 88, 9999, 56423 are open.

As port 4 is running nginx server, the nginx server hosts the webpage to view it we will open it in our browser to find a page that says it is under maintenance along with a link that says try again.

We will click on the link and find that there is a page parameter that we found to be vulnerable to LFI.

Back to the nmap scan we also saw that port 80 is running nginx server, we open it in our browser and find a server error This was proved to be a dead end

Let’s try our lock on Port 88 which i also running nginx server, we open the ip address in our browser on port 88 and find a phpmyadmin page. As we don’t have any hint or clue for the credentials, we will have to try another port.

Port 9999 is running nginx server, we open the ip address on port 9999 in our browser and find a pfsense login page.

Port 56423 is running nginx, so visiting the service on Port 56423 brings us to what appears to be some sort of “API” endpoint as we receive a JSON response.

It is possible that this page is vulnerable to XXE, so we create a shell so that can upload and execute it on the target machine.

After creating a shell, we start HTTP server on our system using python.

After creating the shell, we setup our listener using metasploit-framework.

Using BurpSuite, we will capture the request, and upload the php shell. But we are unable to get a reverse shell.

We then try to exploit the page we find on port 4 using RFI and were able to successfully get a reverse shell.

We get the reverse shell, but it was not a proper shell. We will spawn a tty shell using python.

After spawning a tty shell, we find a file called ‘Fulcrum_Upload_to_Corp.ps1’ we open and find it is a powershell script to encrypt the password it goes through some functions.

Now we copy the content of the script, and paste it in a site called https://tio.run/powershell We do this in hope to extract the logon credentials on the server.

Enumerating further into the system we find a file that contains an interesting internal IP address:192.168.122.228. Further what to do is that we will divert our attention to enumerate this IP address.

We scan the port of the IP address using netcat. After completion of the scan we find that port 5986 is open.

We download socat into the target machine. Socat is a very useful tool which helps us to pivot our way into another network.

We relay the connection to port 60217 on 10.10.10.62 using socat.

We will now use powershell on our windows machine to connect to the kali machine that will allow us to directly connect to the target machine. After connecting we take a look at the content of the default directory we are in and find a few files called “CheckFileServer.ps1”, “Invoke-PsExec.ps1” and “user.txt”.

Enumerating through the directories inside default IIS directory, we open web.config file and find LDAP login credentials.

Let’s create a LDAP query, and find two CNs: DC and File. We create a query about these CN’s and find some credentials.

We create a script to get a the user.txt and were successfully able to get the first flag. We do not have permission to get multiple PS hop.

We setup our listener using netcat and get our reverse shell. We check for the available files and find a file called user.txt. We open it and find the first flag.

Now as we have shell on the file server. We will use the credentials we found earlier to get access on the DC server.

When we will connect to DC server we find multiple ps1 scripts that contains credentials which will further help us to get the access on the server.

We create a script to check all right credentials in the file.

Now we create a script to get shell on the domain controller server.

When we run the script, we get a pop on the windows screen that asks for password. We use the password we find earlier with the help of script.

We setup the listener and wait for the reverse shell. After getting the reverse shell in c:\Users\Administrator\Desktop we find a file called root.txt, we take a look at the content of the file and find our 2nd flag.

Author: Sayantan Bera is a technical writer at hacking articles and cyber security enthusiast. Contact Here

Multiple Ways to Bypass UAC using Metasploit

Hello friends!! Today we are shading light on User Account Control shortly known as UAC. We will also look how it can potentially protect you from malicious software and ignoring UAC prompt can trouble your system.

Table of content

Introduction to UAC

What is UAC?

Working of UAC

5 ways to Bypass UAC

  1. Windows Escalate UAC Protection Bypass
  2. Windows Escalate UAC Protection Bypass (In Memory Injection)
  3. Windows UAC Protection Bypass (Via FodHelper Registry Key)
  4. Windows Escalate UAC Protection Bypass (Via Eventvwr Registry Key)
  5. Windows Escalate UAC Protection Bypass (Via COM Handler Hijack)

Introduction to User Account Control

What is User Account Control?

A well-structured User Account Control introduced with Microsoft’s Windows Vista and Windows Server 2008 operating systems to prevent unwanted system-wide changes in a way that is foreseen and requires minimal effort.

In other words it is a security feature of Windows which supports I preventing unauthorized modifications to the operating system UAC makes sure that the certain changes are made only with authorization from the administrator. If the changes are not permitted by the administrator, they are not executed, and Windows remains unchanged.

How does UAC work?

UAC works by preventing a program from carrying out any tasks which involve system changes/specific tasks. The operations which will not work unless the process attempting to carry them out is running with administrator rights. If you run a program as administrator, it will have more privileges since it would be “elevated”, compared to the programs running which are not running as administrator.

Some things which cannot be done without administrator rights:

  • Registry modifications (if the registry key is under e.g. HKEY_LOCAL_MACHINE (since it affects more than one user) it will be read-only)
  • Loading a device driver
  • DLL injection
  • Modifying system time (clock)
  • Modifying User Account Control settings (via Registry, it can be enabled/disabled but you need the correct privileges to do this)
  • Modify protected directories (e.g. Windows folder, Program Files)
  • Scheduled tasks (e.g. to auto-start with administrator privileges)

UAC won’t just automatically block malicious software, the purpose wasn’t to determine if a program is malicious or not. It’s down to the user just as much. If a program is going to be executed with administrator privileges, the user will be alerted and will need to provide confirmation. 

https://malwaretips.com/threads/why-uac-is-important-and-how-it-can-protect-you.47157/

5 Ways to Bypass UAC

Firstly exploit the target machine to obtain the meterpreter. Once you get the meterpreter session 1 then type following command to check system authority and privileges.

getsystem

getuid

If you don’t have system/admin authorities and privileges. Then you should go for bypass UAC Protection of targeted system.

Windows Escalate UAC Protection Bypass

This module will bypass Windows UAC by utilizing the trusted publisher certificate through process injection. It will spawn a second shell that has the UAC flag turned off.

From given image you can observe that meterpreter session 2 opened, now type the following command to determine the system authority privileges.

Great!! Here we got NT AUTHORITY\SYSTEM Privilege, now if you will type “shell” command, you will get access of command prompt with administrator privilege.

Windows Escalate UAC Protection Bypass (In Memory Injection)

This module will bypass Windows UAC by utilizing the trusted publisher certificate through process injection. It will spawn a second shell that has the UAC flag turned off. This module uses the Reflective DLL Injection technique to drop only the DLL payload binary instead of three separate binaries in the standard technique. However, it requires the correct architecture to be selected, (use x64 for SYSWOW64 systems also). If specifying EXE::Custom your DLL should call ExitProcess() after starting your payload in a separate process.

From given image you can observe that meterpreter session 2 opened, now type the following command to determine the system authority privileges.

Ultimately you will get NT AUTHORITY\SYSTEM Privilege, now if you will run “shell” command, you will get access of command prompt with administrator privilege.

Windows UAC Protection Bypass (Via FodHelper Registry Key)

This module will bypass Windows 10 UAC by hijacking a special key in the Registry under the current user hive, and inserting a custom command that will get invoked when the Windows fodhelper.exe application is launched. It will spawn a second shell that has the UAC flag turned off. This module modifies a registry key, but cleans up the key once the payload has been invoked. The module does not require the architecture of the payload to match the OS. If specifying EXE::Custom your DLL should call ExitProcess() after starting your payload in a separate process.

From given image you can observe that meterpreter session 2 opened, now type the following command to determine the system authority privileges.

Great!! Here we got NT AUTHORITY\SYSTEM Privilege, now if you will type “shell” command,  you will get access of command prompt with administrator privilege.

Windows Escalate UAC Protection Bypass (Via Eventvwr Registry Key)

This module will bypass Windows UAC by hijacking a special key in the Registry under the current user hive, and inserting a custom command that will get invoked when the Windows Event Viewer is launched. It will spawn a second shell that has the UAC flag turned off. This module modifies a registry key, but cleans up the key once the payload has been invoked. The module does not require the architecture of the payload to match the OS. If specifying EXE::Custom your DLL should call ExitProcess() after starting your payload in a separate process.

From given image you can observe that meterpreter session 2 opened, now type the following command to determine the system authority privileges.

And again you will get NT AUTHORITY\SYSTEM Privilege.

Windows Escalate UAC Protection Bypass (Via COM Handler Hijack)

This module will bypass Windows UAC by creating COM handler registry entries in the HKCU hive. When certain high integrity processes are loaded, these registry entries are referenced resulting in the process loading user-controlled DLLs. These DLLs contain the payloads that result in elevated sessions. Registry key modifications are cleaned up after payload invocation. This module requires the architecture of the payload to match the OS, but the current low-privilege Meterpreter session architecture can be different. If specifying EXE::Custom your DLL should call ExitProcess() after starting your payload in a separate process. This module invokes the target binary via cmd.exe on the target. Therefore if cmd.exe access is restricted, this module will not run correctly.

From given image you can observe that meterpreter session 2 opened, now type the following command to determine the system authority privileges.

Finally you will get NT AUTHORITY\SYSTEM Privilege, now if you will again run “shell” command then you will get access of command prompt with administrator privilege and this way we can help of Metasploit post exploit to bypass UAC protection.

Author: AArti Singh is a Researcher and Technical Writer at Hacking Articles an Information Security Consultant Social Media Lover and Gadgets. Contact here

Windows Kernel Exploit Privilege Escalation

Hello Friends!! In our previous article we had discussed “Vectors of Windows Privilege Escalation using automated script” and today we are demonstrating the Windows privilege escalation via Kernel exploitation methodologies. For this purpose, we will utilize an in-built Metasploit module known as Local Exploit Suggester. The objective of this suggester is to just identify what parts of a system can be exploitable and to give us an insight on the best matching possible exploits available ,which can be further utilized to elevate the privileges .

Table of content

  • Windows-Exploit-suggester
  • Windows ClientCopyImage Win32k Exploit
  • Windows TrackPopupMenu Win32k NULL Pointer Dereference
  • Windows SYSTEM Escalation via KiTrap0D
  • Windows Escalate Task Scheduler XML Privilege Escalation
  • MS16-016 mrxdav.sys WebDav Local Privilege Escalation
  • EPATHOBJ::pprFlattenRec Local Privilege Escalation
  • MS13-053 : NTUserMessageCall Win32k Kernel Pool Overflow
  • MS16-032 Secondary Logon Handle Privilege Escalation
  • RottenPotato

Windows-Exploit-suggester

The Metasploit in-built module suggests various local exploits that can be used to perform Privilege escalation and provides a suggestion based on the architecture, platform (i.e the operating system it’s being run on), session type and required default options. It saves our time as we don’t have to manually search around for local exploits, until none of the option provided works.

It is also significant to note that , not ALL of these listed local exploits will be fired.

Usage

Note : For using the local exploit suggester, we must already have a Meterpreter session opened for our target machine. However, before running the Local Exploit suggester we need to put our existing active Meterpreter session to background (CTRL + Z)

Below is the example of the same, let’s say our existing active Meterpreter session is 1

As you can observe it has suggested some post exploits against which the target is vulnerable and that can provide higher-privilege shell.

Windows ClientCopyImage Win32k Exploit

Vulnerabilities in Windows Kernel-Mode Drivers could allow elevation of privilege. This module exploits improper object handling in the win32k.sys kernel mode driver.

This module has been tested on vulnerable builds of Windows 7 x64 and x86, Windows 2008 R2 SP1 x64.

Let’s navigate to MSF console and execute this exploit

Another Meterpreter session gets opened, once the selected exploit has been executed

As we can see that we are logged into the system as Windows privileged user NT AUTHORITY\SYSTEM

 

Windows TrackPopupMenu Win32k NULL Pointer Dereference

This module exploits a NULL Pointer Dereference in win32k.sys, the vulnerability can be triggered through the use of TrackPopupMenu. Under special conditions, the NULL pointer dereference can be abused on xxxSendMessageTimeout to achieve arbitrary code execution.

This module has been tested on Windows XP SP3, Windows Server 2003 SP2, Windows 7 SP1 Windows Server 2008 32bits and Windows Server 2008 R2 SP1 64 bits.

Let’s navigate to MSF console and execute this exploit

Another Meterpreter session gets opened ,once the selected exploit has been executed

As we can see that we are logged into the system as Windows privileged user NT AUTHORITY\SYSTEM

 

Windows SYSTEM Escalation via KiTrap0D

This module will create a new session with SYSTEM privileges via the KiTrap0D exploit If the session in use is already elevated then the exploit will not run. The module relies on kitrap0d.x86.dll, and is not supported on x64 editions of Windows.

This module has been tested on vulnerable builds of Windows Server 2003, Windows Server 2008, Windows 7, XP for 32-bit Systems.

Let’s navigate to MSF console and execute this exploit

 Another Meterpreter session gets opened, once the selected exploit has been executed

As we can see that we are logged into the system as Windows privileged user NT AUTHORITY\SYSTEM

Windows Escalate Task Scheduler XML Privilege Escalation

This Vulnerability in Task Scheduler could allow elevation of privileges

This security update resolves a publicly disclosed vulnerability in Windows Task Scheduler. The vulnerability could allow elevation of privilege if an attacker logged on to an affected system and ran a specially crafted application. An attacker must have valid logon credentials and be able to log on locally to exploit this vulnerability. The vulnerability could not be exploited remotely or by anonymous users.

This module has been tested on vulnerable builds of Windows Vista , Windows 7 , Windows Server 2008 x64 and x86

Let’s navigate to MSF console and execute this exploit

Another Meterpreter session gets opened, once the selected exploit has been executed

As we can see that we are logged into the system as Windows privileged user NT AUTHORITY\SYSTEM

 

MS16-016 mrxdav.sys WebDav Local Privilege Escalation

This module exploits the vulnerability in mrxdav.sys described by MS16-016. The module will spawn a process on the target system and elevate its privileges to NT AUTHORITY\SYSTEM before executing the specified payload within the context of the elevated process.

This module has been tested on vulnerable build of Windows 7 SP1 ,x86 architecture

Let’s navigate to MSF console and execute this exploit

Another Meterpreter session gets opened ,once the selected exploit has been executed

As we can see that we are logged into the system as Windows privileged user NT AUTHORITY\SYSTEM

EPATHOBJ::pprFlattenRec Local Privilege Escalation

This module exploits a vulnerability on EPATHOBJ::pprFlattenRec due to the usage of uninitialized data which allows to corrupt memory.

At the moment, the module has been tested successfully on Windows XP SP3, Windows 2003 SP1, and Windows 7 SP1.

Let’s navigate to MSF console and execute this exploit

Another Meterpreter session gets opened, once the selected exploit has been executed

As we can see that we are logged into the system as Windows privileged user NT AUTHORITY\SYSTEM

MS13-053 : NTUserMessageCall Win32k Kernel Pool Overflow

A kernel pool overflow in Win32k which allows local privilege escalation. The kernel shellcode nulls the ACL for the winlogon.exe process (a SYSTEM process). This allows any unprivileged process to freely migrate to winlogon.exe, achieving privilege escalation. Used in pwn2own 2013 by MWR to break out of chrome’s sandbox. NOTE: when you exit the meterpreter session, winlogon.exe is likely to crash.

At the moment, the module has been tested successfully on Windows 7 SP1 x86

Let’s navigate to MSF console and execute this exploit

Another Meterpreter session gets opened, once the selected exploit has been executed

As we can see that we are logged into the system as Windows privileged user NT AUTHORITY\SYSTEM

MS16-032 Secondary Logon Handle Privilege Escalation

This module exploits the lack of sanitization of standard handles in Windows’ Secondary Logon Service. The vulnerability is known to affect versions of Windows 7-10 and 2k8-2k12 32 and 64 bit. This module will only work against those versions of Windows with Powershell 2.0 or later and systems with two or more CPU cores.

Another Meterpreter session gets opened, once the selected exploit has been executed

As we can see that we are logged into the system as Windows privileged user NT AUTHORITY\SYSTEM

RottenPotato

RottenPotato local privilege escalation from service account to SYSTEM.

It is important to impersonate the token (or run list_tokens -u) quickly after runnning the binary. With the current implementation, the token seems to disappear shortly after the binary is run. It is also important to follow the order of the steps. Make sure you “use incognito” before running the binary.

Incognito option in meterpreter session was originally a stand-alone application that permitted you to impersonate user tokens when successfully compromising a system. And then we need to do first is identify if there are any valid tokens on this system.

If we talk related to impersonate token then you can see currently there is no token available.

Now downloads Rottenpotato from github for privilege escalation.

After downloading it will give rottenpotato.exe file.

Upload the exe file into victim’s machine

Now type below command for executing exe file and then add SYSTEM token under impersonate user tokens.

As we can see that we are logged into the system as Windows privileged user NT AUTHORITY\SYSTEM

Author: Ankur Sachdev is Information Security consultant and researcher in the field of Network & WebApp Penetration Testing . Contact Here

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