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212 lines
18 KiB
Markdown
212 lines
18 KiB
Markdown
# Windows Credentials Protections
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{{#include ../../banners/hacktricks-training.md}}
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## WDigest
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The [WDigest](<https://technet.microsoft.com/pt-pt/library/cc778868(v=ws.10).aspx?f=255&MSPPError=-2147217396>) protocol, introduced with Windows XP, is designed for authentication via the HTTP Protocol and is **enabled by default on Windows XP through Windows 8.0 and Windows Server 2003 to Windows Server 2012**. This default setting results in **plain-text password storage in LSASS** (Local Security Authority Subsystem Service). An attacker can use Mimikatz to **extract these credentials** by executing:
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```bash
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sekurlsa::wdigest
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```
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To **toggle this feature off or on**, the _**UseLogonCredential**_ and _**Negotiate**_ registry keys within _**HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\SecurityProviders\WDigest**_ must be set to "1". If these keys are **absent or set to "0"**, WDigest is **disabled**:
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```bash
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reg query HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\WDigest /v UseLogonCredential
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```
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## LSA Protection (PP & PPL protected processes)
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**Protected Process (PP)** and **Protected Process Light (PPL)** are **Windows kernel-level protections** designed to prevent unauthorized access to sensitive processes like **LSASS**. Introduced in **Windows Vista**, the **PP model** was originally created for **DRM** enforcement and only allowed binaries signed with a **special media certificate** to be protected. A process marked as **PP** can only be accessed by other processes that are **also PP** and have an **equal or higher protection level**, and even then, **only with limited access rights** unless specifically allowed.
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**PPL**, introduced in **Windows 8.1**, is a more flexible version of PP. It allows **broader use cases** (e.g., LSASS, Defender) by introducing **"protection levels"** based on the **digital signature’s EKU (Enhanced Key Usage)** field. The protection level is stored in the `EPROCESS.Protection` field, which is a `PS_PROTECTION` structure with:
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- **Type** (`Protected` or `ProtectedLight`)
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- **Signer** (e.g., `WinTcb`, `Lsa`, `Antimalware`, etc.)
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This structure is packed into a single byte and determines **who can access whom**:
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- **Higher signer values can access lower ones**
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- **PPLs can’t access PPs**
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- **Unprotected processes can't access any PPL/PP**
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### What you need to know from an offensive perspective
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- When **LSASS runs as a PPL**, attempts to open it using `OpenProcess(PROCESS_VM_READ | QUERY_INFORMATION)` from a normal admin context **fail with `0x5 (Access Denied)`**, even if `SeDebugPrivilege` is enabled.
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- You can **check LSASS protection level** using tools like Process Hacker or programmatically by reading the `EPROCESS.Protection` value.
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- LSASS will typically have `PsProtectedSignerLsa-Light` (`0x41`), which can be accessed **only by processes signed with a higher-level signer**, such as `WinTcb` (`0x61` or `0x62`).
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- PPL is a **Userland-only restriction**; **kernel-level code can fully bypass it**.
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- LSASS being PPL does **not prevent credential dumping if you can execute kernel shellcode** or **leverage a high-privileged process with proper access**.
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- **Setting or removing PPL** requires reboot or **Secure Boot/UEFI settings**, which can persist the PPL setting even after registry changes are reversed.
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### Create a PPL process at launch (documented API)
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Windows exposes a documented way to request a Protected Process Light level for a child process during creation using the extended startup attribute list. This does not bypass signing requirements — the target image must be signed for the requested signer class.
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Minimal flow in C/C++:
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```c
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// Request a PPL protection level for the child process at creation time
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// Requires Windows 8.1+ and a properly signed image for the selected level
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#include <windows.h>
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int wmain(int argc, wchar_t **argv) {
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STARTUPINFOEXW si = {0};
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PROCESS_INFORMATION pi = {0};
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si.StartupInfo.cb = sizeof(si);
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SIZE_T attrSize = 0;
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InitializeProcThreadAttributeList(NULL, 1, 0, &attrSize);
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si.lpAttributeList = (PPROC_THREAD_ATTRIBUTE_LIST)HeapAlloc(GetProcessHeap(), 0, attrSize);
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if (!si.lpAttributeList) return 1;
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if (!InitializeProcThreadAttributeList(si.lpAttributeList, 1, 0, &attrSize)) return 1;
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DWORD level = PROTECTION_LEVEL_ANTIMALWARE_LIGHT; // or WINDOWS_LIGHT/LSA_LIGHT/WINTCB_LIGHT
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if (!UpdateProcThreadAttribute(
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si.lpAttributeList, 0,
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PROC_THREAD_ATTRIBUTE_PROTECTION_LEVEL,
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&level, sizeof(level), NULL, NULL)) {
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return 1;
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}
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DWORD flags = EXTENDED_STARTUPINFO_PRESENT;
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if (!CreateProcessW(L"C\\Windows\\System32\\notepad.exe", NULL, NULL, NULL, FALSE,
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flags, NULL, NULL, &si.StartupInfo, &pi)) {
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// If the image isn't signed appropriately for the requested level,
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// CreateProcess will fail with ERROR_INVALID_IMAGE_HASH (577).
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return 1;
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}
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// cleanup
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DeleteProcThreadAttributeList(si.lpAttributeList);
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HeapFree(GetProcessHeap(), 0, si.lpAttributeList);
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CloseHandle(pi.hThread);
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CloseHandle(pi.hProcess);
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return 0;
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}
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```
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Notes and constraints:
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- Use `STARTUPINFOEX` with `InitializeProcThreadAttributeList` and `UpdateProcThreadAttribute(PROC_THREAD_ATTRIBUTE_PROTECTION_LEVEL, ...)`, then pass `EXTENDED_STARTUPINFO_PRESENT` to `CreateProcess*`.
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- The protection `DWORD` can be set to constants such as `PROTECTION_LEVEL_WINTCB_LIGHT`, `PROTECTION_LEVEL_WINDOWS`, `PROTECTION_LEVEL_WINDOWS_LIGHT`, `PROTECTION_LEVEL_ANTIMALWARE_LIGHT`, or `PROTECTION_LEVEL_LSA_LIGHT`.
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- The child only starts as PPL if its image is signed for that signer class; otherwise process creation fails, commonly with `ERROR_INVALID_IMAGE_HASH (577)` / `STATUS_INVALID_IMAGE_HASH (0xC0000428)`.
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- This is not a bypass — it’s a supported API meant for appropriately signed images. Useful to harden tools or validate PPL-protected configurations.
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Example CLI using a minimal loader:
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- Antimalware signer: `CreateProcessAsPPL.exe 3 C:\Tools\agent.exe --svc`
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- LSA-light signer: `CreateProcessAsPPL.exe 4 C:\Windows\System32\notepad.exe`
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**Bypass PPL protections options:**
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If you want to dump LSASS despite PPL, you have 3 main options:
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1. **Use a signed kernel driver (e.g., Mimikatz + mimidrv.sys)** to **remove LSASS’s protection flag**:
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2. **Bring Your Own Vulnerable Driver (BYOVD)** to run custom kernel code and disable the protection. Tools like **PPLKiller**, **gdrv-loader**, or **kdmapper** make this feasible.
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3. **Steal an existing LSASS handle** from another process that has it open (e.g., an AV process), then **duplicate it** into your process. This is the basis of the `pypykatz live lsa --method handledup` technique.
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4. **Abuse some privileged process** that will allow you to load arbitrary code into its address space or inside another privileged process, effectively bypassing the PPL restrictions. You can check an example of this in [bypassing-lsa-protection-in-userland](https://blog.scrt.ch/2021/04/22/bypassing-lsa-protection-in-userland/) or [https://github.com/itm4n/PPLdump](https://github.com/itm4n/PPLdump).
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**Check current status of LSA protection (PPL/PP) for LSASS**:
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```bash
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reg query HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\LSA /v RunAsPPL
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```
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When you running **`mimikatz privilege::debug sekurlsa::logonpasswords`** it'll probably fail with the error code `0x00000005` becasue of this.
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- For more information about this check [https://itm4n.github.io/lsass-runasppl/](https://itm4n.github.io/lsass-runasppl/)
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## Credential Guard
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**Credential Guard**, a feature exclusive to **Windows 10 (Enterprise and Education editions)**, enhances the security of machine credentials using **Virtual Secure Mode (VSM)** and **Virtualization Based Security (VBS)**. It leverages CPU virtualization extensions to isolate key processes within a protected memory space, away from the main operating system's reach. This isolation ensures that even the kernel cannot access the memory in VSM, effectively safeguarding credentials from attacks like **pass-the-hash**. The **Local Security Authority (LSA)** operates within this secure environment as a trustlet, while the **LSASS** process in the main OS acts merely as a communicator with the VSM's LSA.
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By default, **Credential Guard** is not active and requires manual activation within an organization. It's critical for enhancing security against tools like **Mimikatz**, which are hindered in their ability to extract credentials. However, vulnerabilities can still be exploited through the addition of custom **Security Support Providers (SSP)** to capture credentials in clear text during login attempts.
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To verify **Credential Guard**'s activation status, the registry key _**LsaCfgFlags**_ under _**HKLM\System\CurrentControlSet\Control\LSA**_ can be inspected. A value of "**1**" indicates activation with **UEFI lock**, "**2**" without lock, and "**0**" denotes it is not enabled. This registry check, while a strong indicator, is not the sole step for enabling Credential Guard. Detailed guidance and a PowerShell script for enabling this feature are available online.
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```bash
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reg query HKLM\System\CurrentControlSet\Control\LSA /v LsaCfgFlags
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```
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For a comprehensive understanding and instructions on enabling **Credential Guard** in Windows 10 and its automatic activation in compatible systems of **Windows 11 Enterprise and Education (version 22H2)**, visit [Microsoft's documentation](https://docs.microsoft.com/en-us/windows/security/identity-protection/credential-guard/credential-guard-manage).
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Further details on implementing custom SSPs for credential capture are provided in [this guide](../active-directory-methodology/custom-ssp.md).
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## RDP RestrictedAdmin Mode
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**Windows 8.1 and Windows Server 2012 R2** introduced several new security features, including the _**Restricted Admin mode for RDP**_. This mode was designed to enhance security by mitigating the risks associated with [**pass the hash**](https://blog.ahasayen.com/pass-the-hash/) attacks.
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Traditionally, when connecting to a remote computer via RDP, your credentials are stored on the target machine. This poses a significant security risk, especially when using accounts with elevated privileges. However, with the introduction of _**Restricted Admin mode**_, this risk is substantially reduced.
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When initiating an RDP connection using the command **mstsc.exe /RestrictedAdmin**, authentication to the remote computer is performed without storing your credentials on it. This approach ensures that, in the event of a malware infection or if a malicious user gains access to the remote server, your credentials are not compromised, as they are not stored on the server.
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It's important to note that in **Restricted Admin mode**, attempts to access network resources from the RDP session will not use your personal credentials; instead, the **machine's identity** is used.
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This feature marks a significant step forward in securing remote desktop connections and protecting sensitive information from being exposed in case of a security breach.
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For more detailed information on visit [this resource](https://blog.ahasayen.com/restricted-admin-mode-for-rdp/).
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## Cached Credentials
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Windows secures **domain credentials** through the **Local Security Authority (LSA)**, supporting logon processes with security protocols like **Kerberos** and **NTLM**. A key feature of Windows is its capability to cache the **last ten domain logins** to ensure users can still access their computers even if the **domain controller is offline**—a boon for laptop users often away from their company's network.
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The number of cached logins is adjustable via a specific **registry key or group policy**. To view or change this setting, the following command is utilized:
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```bash
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reg query "HKEY_LOCAL_MACHINE\SOFTWARE\MICROSOFT\WINDOWS NT\CURRENTVERSION\WINLOGON" /v CACHEDLOGONSCOUNT
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```
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Access to these cached credentials is tightly controlled, with only the **SYSTEM** account having the necessary permissions to view them. Administrators needing to access this information must do so with SYSTEM user privileges. The credentials are stored at: `HKEY_LOCAL_MACHINE\SECURITY\Cache`
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**Mimikatz** can be employed to extract these cached credentials using the command `lsadump::cache`.
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For further details, the original [source](http://juggernaut.wikidot.com/cached-credentials) provides comprehensive information.
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## Protected Users
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Membership in the **Protected Users group** introduces several security enhancements for users, ensuring higher levels of protection against credential theft and misuse:
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- **Credential Delegation (CredSSP)**: Even if the Group Policy setting for **Allow delegating default credentials** is enabled, plain text credentials of Protected Users will not be cached.
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- **Windows Digest**: Starting from **Windows 8.1 and Windows Server 2012 R2**, the system will not cache plain text credentials of Protected Users, regardless of the Windows Digest status.
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- **NTLM**: The system will not cache Protected Users' plain text credentials or NT one-way functions (NTOWF).
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- **Kerberos**: For Protected Users, Kerberos authentication will not generate **DES** or **RC4 keys**, nor will it cache plain text credentials or long-term keys beyond the initial Ticket-Granting Ticket (TGT) acquisition.
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- **Offline Sign-In**: Protected Users will not have a cached verifier created at sign-in or unlock, meaning offline sign-in is not supported for these accounts.
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These protections are activated the moment a user, who is a member of the **Protected Users group**, signs into the device. This ensures that critical security measures are in place to safeguard against various methods of credential compromise.
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For more detailed information, consult the official [documentation](https://docs.microsoft.com/en-us/windows-server/security/credentials-protection-and-management/protected-users-security-group).
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**Table from** [**the docs**](https://docs.microsoft.com/en-us/windows-server/identity/ad-ds/plan/security-best-practices/appendix-c--protected-accounts-and-groups-in-active-directory)**.**
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| Windows Server 2003 RTM | Windows Server 2003 SP1+ | <p>Windows Server 2012,<br>Windows Server 2008 R2,<br>Windows Server 2008</p> | Windows Server 2016 |
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| ----------------------- | ------------------------ | ----------------------------------------------------------------------------- | ---------------------------- |
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| Account Operators | Account Operators | Account Operators | Account Operators |
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| Administrator | Administrator | Administrator | Administrator |
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| Administrators | Administrators | Administrators | Administrators |
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| Backup Operators | Backup Operators | Backup Operators | Backup Operators |
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| Cert Publishers | | | |
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| Domain Admins | Domain Admins | Domain Admins | Domain Admins |
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| Domain Controllers | Domain Controllers | Domain Controllers | Domain Controllers |
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| Enterprise Admins | Enterprise Admins | Enterprise Admins | Enterprise Admins |
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| | | | Enterprise Key Admins |
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| | | | Key Admins |
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| Krbtgt | Krbtgt | Krbtgt | Krbtgt |
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| Print Operators | Print Operators | Print Operators | Print Operators |
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| | | Read-only Domain Controllers | Read-only Domain Controllers |
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| Replicator | Replicator | Replicator | Replicator |
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| Schema Admins | Schema Admins | Schema Admins | Schema Admins |
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| Server Operators | Server Operators | Server Operators | Server Operators |
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## References
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- [CreateProcessAsPPL – minimal PPL process launcher](https://github.com/2x7EQ13/CreateProcessAsPPL)
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- [STARTUPINFOEX structure (Win32 API)](https://learn.microsoft.com/en-us/windows/win32/api/winbase/ns-winbase-startupinfoexw)
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- [InitializeProcThreadAttributeList (Win32 API)](https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-initializeprocthreadattributelist)
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- [UpdateProcThreadAttribute (Win32 API)](https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-updateprocthreadattribute)
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- [LSASS RunAsPPL – background and internals](https://itm4n.github.io/lsass-runasppl/)
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