Repository files navigation

A tool to check Domain Controllers for LDAP server protections regarding the relay of NTLM authentication. If you're interested in the specifics of the error-based enumeration, seebelow. For details regarding what can be done when you identify a lack of LDAP protections, see thereferences section.

There are a couple server-side protections when attempting to relay NTLM authentication LDAP on Domain Controllers. The LDAP protections this tools attempts to enumerate include:

• LDAPS -channel binding
• LDAP -server signing requirements

The enforcement of channel binding for LDAP over SSL/TLS can be determined from anunauthenticated perspective. This is because the error associated with an LDAP client lacking the ability to conduct channel binding properly will occur before credentials are validated during the LDAP bind process.

However, to determine if the server-side protection of standard LDAP is enforced (server signing integrity requirements) the clients credential's must first be validated during the LDAP bind. The potential error identifying the enforcement of this protection is identified from anauthenticated perspective.

It is recommended to use either Docker or a Python virtual environment when running this project.

1. Ensuredocker is installed on your machine
2. Clone the repository and change directory
   • git clone https://github.com/zyn3rgy/LdapRelayScan.git && cd LdapRelayScan
3. Build the Docker container
   • docker build -f docker/Dockerfile -t ldaprelayscan .
4. [optionally] Ensure the script executes properly
   • docker run ldaprelayscan -h

1. Ensurepython virtualenv is installed on your machine
2. Clone the repository and change directory
   • git clone https://github.com/zyn3rgy/LdapRelayScan.git && cd LdapRelayScan
3. Create a Python virtual environment for the project
   • virtualenv env
4. Activate the Python virtual environment
   • source venv/bin/activate
5. Install exact requirement version dependencies
   • python3 -m pip install -r requirements_exact.txt
6. [optionally] Ensure the script executes properly
   • python3 LdapRelayScan.py -h

NOTE: DNS needs to resolve properly. If you are routing through SOCKS or running on a non-domain-joined host, ensure this is working.

The tool has two methods,LDAPS (the default), andBOTH. LDAPS only requires a domain controller IP address, because this check can be preformed unauthenticated. The BOTH method will require a username and password or NT hash. The Active Directory domain is not required, it will be determine via anonymous LDAP bind.

arguments:  -h, --help        show this help message and exit  -method method    LDAPS or BOTH - LDAPS checks for channel binding, BOTH checks for LDAP signing and LDAP channel binding [authentication required]  -dc-ip DC_IP      DNS Nameserver on network. Any DC's IPv4 address should work.  -u username       Domain username value.  -timeout timeout  The timeout for MSLDAP client connection.  -p password       Domain username value.  -nthash nthash    NT hash of password

python3 LdapRelayScan.py -method LDAPS -dc-ip 10.0.0.20python3 LdapRelayScan.py -method BOTH -dc-ip 10.0.0.20 -u domainuser1 python3 LdapRelayScan.py -method BOTH -dc-ip 10.0.0.20 -u domainuser1 -p badpassword2python3 LdapRelayScan.py -method BOTH -dc-ip 10.0.0.20 -u domainuser1 -nthash e6ee750a1feb2c7ee50d46819a6e4d25

NOTE: The ability to use SOCKS is passed in using aPROXY_CONFIG environment variable. If SOCKS is required, the--network=host flag will also need to be used to correctly route traffic. See examples below.

docker run ldaprelayscan -hdocker run ldaprelayscan -dc-ip 10.0.0.20docker run ldaprelayscan -dc-ip 10.0.0.20 -method BOTH -u domainuser1 -p secretpassdocker run -e PROXY_CONFIG='socks5 127.0.0.1 9050' --network=host ldaprelayscan -dc-ip 10.0.0.20 -method BOTH -u domainuser1 -p secretpass

On a Domain Controller that has been patched sinceCVE-2017-8563, the capability to enforce LDAPS channel binding has existed. The specific policy is calledDomain Controller: LDAP server channel binding token requirements and can be set to eitherNever,When supported, orAlways. This is alsonot required by default (at the time of writing this).

Decrypting and monitoring LDAP over SSL/TLS traffic on a Domain Controller allowed for the identification of a difference in errors during bind attempts when channel binding is enforced versus when it's not. When attempting a bind to LDAP over SSL/TLS using invalid credentials, you will recieve the expectedresultCode 49, and in the error message contents you will seedata 52e. However, when channel binding is enforced and the LDAP client does not calculate and include the Channel Binding Token (CBT), the resultCode will still be 49, but the error message contents will containdata 80090346 meaningSEC_E_BAD_BINDINGS or thatthe client's Supplied Support Provider Interface (SSPI) channel bindings were incorrect.

NOTE: Mentions of thedata 8009034 error during LDAP over SSL/TLS binding[1][2][3][4][5]

This specific error makes it easy enough to account for when theDomain Controller: LDAP server channel binding token requirements policy is set toAlways. Simply attempt an NTLM-based LDAPS bind using a client that does not support channel binding and look for thedata 80090346 within the error in response. But what about when the policy is not set toAlways, what about when it's set toWhen supported? The answer is: bind to LDAPS with NTLM-based authentication and purposefully miscalculate the channel binding information.

First, we need an LDAP client that supports channel binding.SkelSec's implementation of this inmsldap will be used to implement a PoC. Channel binding appears as anAV_PAIR value during the NTLM challenge/response process, specifically within the Type 3 orAUTHENTICATE_MESSAGE. Here's another look at some decrypted LDAPS traffic on a Domain Controller to see what a bind attempt from a client supporting channel binding will look like:

Intentionally miscalculating this value, when the policy in question is set toWhen supported, will produce the samedata 80090346 error. This gives us the ability to differentiate between all possible settings for this policy as it currently exists, from an unauthenticated perspective. How this value is purposefully miscalculated is important, because just manually replacing the value during challenge/response will invalidate theMIC.

On a Domain Controller, the policy calledDomain Controller: LDAP server signing requirements is set toNone,Require signing, or it's just not defined. When not defined, it defaults to not requiring signing (at the time of writing this). The error which identifies this protection as required is when asicily NTLM orsimple bind attempt responds with aresultCode of 8, signifyingstrongerAuthRequired. This will only occur if credentials during the LDAP bind are validated.

A few invaluable resources for contextualization of this material and how it fits into common attack scenarios.

• @HackAndDo -NTLM relay
• @_nwodtuhs -NTLM relay mindmap
• @_dirkjan -PrivExchange, theADCS ESC8 write up, theNTLM relay for RBCD write up, and more
• @domchell - implementation ofFarmer andexplanation
• @elad_shamir - thoroughexplanations of abusing RBCD inmultiple scenarios, andshadow credentials
• @tifkin_ &@topotam77 - NTLM authentication coercion methods
• @skelsec -msldap w/ support for channel binding