# Shadow Credentials Attack

### Overview

A **Shadow Attack** (Shadow Credentials abuse) is an Active Directory privilege escalation technique where an attacker adds a malicious public key to a target account’s `msDS-KeyCredentialLink` attribute.

This allows the attacker to authenticate as that account using **certificate-based authentication**, without knowing the password.

Instead of resetting the password or stealing NTLM hashes, the attacker:

* Modifies the target’s `msDS-KeyCredentialLink`
* Adds their own certificate public key
* Uses PKINIT to request a Kerberos TGT
* Authenticates as the victim account

### Why this Works

Modern Active Directory environments support:

* **Windows Hello for Business**
* Certificate-based authentication
* PKINIT (Public Key Cryptography for Initial Authentication)

The attribute:

```
msDS-KeyCredentialLink
```

Stores public key information for certificate-based logon.

If an attacker has **write access** to this attribute for a user or computer object, they can:

1. Add their own certificate
2. Authenticate using that certificate
3. Obtain a TGT as that account
4. Escalate privileges

It works because AD trusts any valid key stored in that attribute.

### Prerequsites

* Domain user credentials
* Write access to target’s `msDS-KeyCredentialLink`\
  (via GenericWrite, GenericAll, WriteProperty, etc.)
* AD domain functional level supporting PKINIT
* Domain Controller with certificate services (or PKINIT support)

### Steps

1. Use BloodHound to identify:
   * GenericWrite
   * GenericAll
   * WriteProperty on `msDS-KeyCredentialLink` 
2. Perform Shadow Credentials Attack:

   ```bash
   certipy-ad shadow auto -u lowuser@domain.local -p Password123! -account targetuser -dc-ip 10.10.11.51
   ```

      What this does:

* Generates a key pair
* Adds the public key to target’s `msDS-KeyCredentialLink`
* Requests a TGT
* Extracts NT hash automatically

### References

1. <https://www.ired.team/offensive-security-experiments/active-directory-kerberos-abuse/shadow-credentials> (If you need more details)


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