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Abusing Tokens

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Tokens

If you don't know what are Windows Access Tokens read this page before continuing:
Maybe you could be able to escalate privileges abusing the tokens you already have

SeImpersonatePrivilege

This is privilege that is held by any process allows the impersonation (but not creation) of any token, given that a handle to it can be obtained. A privileged token can be acquired from a Windows service (DCOM) by inducing it to perform NTLM authentication against an exploit, subsequently enabling the execution of a process with SYSTEM privileges. This vulnerability can be exploited using various tools, such as juicy-potato, RogueWinRM (which requires winrm to be disabled), SweetPotato, and PrintSpoofer.

SeAssignPrimaryPrivilege

It is very similar to SeImpersonatePrivilege, it will use the same method to get a privileged token. Then, this privilege allows to assign a primary token to a new/suspended process. With the privileged impersonation token you can derivate a primary token (DuplicateTokenEx). With the token, you can create a new process with 'CreateProcessAsUser' or create a process suspended and set the token (in general, you cannot modify the primary token of a running process).

SeTcbPrivilege

If you have enabled this token you can use KERB_S4U_LOGON to get an impersonation token for any other user without knowing the credentials, add an arbitrary group (admins) to the token, set the integrity level of the token to "medium", and assign this token to the current thread (SetThreadToken).

SeBackupPrivilege

The system is caused to grant all read access control to any file (limited to read operations) by this privilege. It is utilized for reading the password hashes of local Administrator accounts from the registry, following which, tools like "psexec" or "wmicexec" can be used with the hash (Pass-the-Hash technique). However, this technique fails under two conditions: when the Local Administrator account is disabled, or when a policy is in place that removes administrative rights from Local Administrators connecting remotely. You can abuse this privilege with:

SeRestorePrivilege

Permission for write access to any system file, irrespective of the file's Access Control List (ACL), is provided by this privilege. It opens up numerous possibilities for escalation, including the ability to modify services, perform DLL Hijacking, and set debuggers via Image File Execution Options among various other techniques.

SeCreateTokenPrivilege

SeCreateTokenPrivilege is a powerful permission, especially useful when a user possesses the ability to impersonate tokens, but also in the absence of SeImpersonatePrivilege. This capability hinges on the ability to impersonate a token that represents the same user and whose integrity level does not exceed that of the current process.
Key Points:
  • Impersonation without SeImpersonatePrivilege: It's possible to leverage SeCreateTokenPrivilege for EoP by impersonating tokens under specific conditions.
  • Conditions for Token Impersonation: Successful impersonation requires the target token to belong to the same user and have an integrity level that is less or equal to the integrity level of the process attempting impersonation.
  • Creation and Modification of Impersonation Tokens: Users can create an impersonation token and enhance it by adding a privileged group's SID (Security Identifier).

SeLoadDriverPrivilege

Thi privilege allows to load and unload device drivers with the creation of a registry entry with specific values for ImagePath and Type. Since direct write access to HKLM (HKEY_LOCAL_MACHINE) is restricted, HKCU (HKEY_CURRENT_USER) must be utilized instead. However, to make HKCU recognizable to the kernel for driver configuration, a specific path must be followed.
This path is \Registry\User\<RID>\System\CurrentControlSet\Services\DriverName, where <RID> is the Relative Identifier of the current user. Inside HKCU, this entire path must be created, and two values need to be set:
  • ImagePath, which is the path to the binary to be executed
  • Type, with a value of SERVICE_KERNEL_DRIVER (0x00000001).
Steps to Follow:
  1. 1.
    Access HKCU instead of HKLM due to restricted write access.
  2. 2.
    Create the path \Registry\User\<RID>\System\CurrentControlSet\Services\DriverName within HKCU, where <RID> represents the current user's Relative Identifier.
  3. 3.
    Set the ImagePath to the binary's execution path.
  4. 4.
    Assign the Type as SERVICE_KERNEL_DRIVER (0x00000001).
# Example Python code to set the registry values
import winreg as reg
# Define the path and values
path = r'Software\YourPath\System\CurrentControlSet\Services\DriverName' # Adjust 'YourPath' as needed
key = reg.OpenKey(reg.HKEY_CURRENT_USER, path, 0, reg.KEY_WRITE)
reg.SetValueEx(key, "ImagePath", 0, reg.REG_SZ, "path_to_binary")
reg.SetValueEx(key, "Type", 0, reg.REG_DWORD, 0x00000001)
reg.CloseKey(key)

SeTakeOwnershipPrivilege

This is similar to to SeRestorePrivilege. Its primary function allows a process to assume ownership of an object, circumventing the requirement for explicit discretionary access through the provision of WRITE_OWNER access rights. The process involves first securing ownership of the intended registry key for writing purposes, then altering the DACL to enable write operations.
takeown /f 'C:\some\file.txt' #Now the file is owned by you
icacls 'C:\some\file.txt' /grant <your_username>:F #Now you have full access
# Use this with files that might contain credentials such as
%WINDIR%\repair\sam
%WINDIR%\repair\system
%WINDIR%\repair\software
%WINDIR%\repair\security
%WINDIR%\system32\config\security.sav
%WINDIR%\system32\config\software.sav
%WINDIR%\system32\config\system.sav
%WINDIR%\system32\config\SecEvent.Evt
%WINDIR%\system32\config\default.sav
c:\inetpub\wwwwroot\web.config

SeDebugPrivilege

This privilege permits the debug other processes, including to read and write in the memore. Various strategies for memory injection, capable of evading most antivirus and host intrusion prevention solutions, can be employed with this privilege.

Dump memory

You could use ProcDump from the SysInternals Suite to capture the memory of a process. Specifically, this can apply to the Local Security Authority Subsystem Service (LSASS) process, which is responsible for storing user credentials once a user has successfully logged into a system.
You can then load this dump in mimikatz to obtain passwords:
mimikatz.exe
mimikatz # log
mimikatz # sekurlsa::minidump lsass.dmp
mimikatz # sekurlsa::logonpasswords

RCE

If you want to get a NT SYSTEM shell you could use:
# Get the PID of a process running as NT SYSTEM
import-module psgetsys.ps1; [MyProcess]::CreateProcessFromParent(<system_pid>,<command_to_execute>)

Check privileges

whoami /priv
The tokens that appear as Disabled can be enable, you you actually can abuse Enabled and Disabled tokens.

Enable All the tokens

If you have tokens disables, you can use the script EnableAllTokenPrivs.ps1 to enable all the tokens:
.\EnableAllTokenPrivs.ps1
whoami /priv
Or the script embed in this post.

Table

Full token privileges cheatsheet at https://github.com/gtworek/Priv2Admin, summary below will only list direct ways to exploit the privilege to obtain an admin session or read sensitive files.
Privilege
Impact
Tool
Execution path
Remarks
SeAssignPrimaryToken
Admin
3rd party tool
"It would allow a user to impersonate tokens and privesc to nt system using tools such as potato.exe, rottenpotato.exe and juicypotato.exe"
Thank you Aurélien Chalot for the update. I will try to re-phrase it to something more recipe-like soon.
SeBackup
Threat
Built-in commands
Read sensitve files with robocopy /b
- May be more interesting if you can read %WINDIR%\MEMORY.DMP - SeBackupPrivilege (and robocopy) is not helpful when it comes to open files. - Robocopy requires both SeBackup and SeRestore to work with /b parameter.
SeCreateToken
Admin
3rd party tool
Create arbitrary token including local admin rights with NtCreateToken.
SeDebug
Admin
PowerShell
Duplicate the lsass.exe token.
Script to be found at FuzzySecurity
SeLoadDriver
Admin
3rd party tool
1. Load buggy kernel driver such as szkg64.sys 2. Exploit the driver vulnerability Alternatively, the privilege may be used to unload security-related drivers with ftlMC builtin command. i.e.: fltMC sysmondrv
1. The szkg64 vulnerability is listed as CVE-2018-15732 2. The szkg64 exploit code was created by Parvez Anwar
SeRestore
Admin
PowerShell
1. Launch PowerShell/ISE with the SeRestore privilege present. 2. Enable the privilege with Enable-SeRestorePrivilege). 3. Rename utilman.exe to utilman.old 4. Rename cmd.exe to utilman.exe 5. Lock the console and press Win+U
Attack may be detected by some AV software.
Alternative method relies on replacing service binaries stored in "Program Files" using the same privilege
SeTakeOwnership
Admin
Built-in commands
1. takeown.exe /f "%windir%\system32" 2. icalcs.exe "%windir%\system32" /grant "%username%":F 3. Rename cmd.exe to utilman.exe 4. Lock the console and press Win+U
Attack may be detected by some AV software.
Alternative method relies on replacing service binaries stored in "Program Files" using the same privilege.
SeTcb
Admin
3rd party tool
Manipulate tokens to have local admin rights included. May require SeImpersonate.
To be verified.

Reference

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