After compromising a Windows host and having obtained local administrator privileges, secrets extraction is usually the first step performed to elevate privileges in the context of an Active Directory domain or to perform lateral movements inside an internal network.

As such, the following type of secrets can be retrieved:

• Secrets in LSASS process.
• Secrets in registry such as LSA secrets.
• DPAPI secrets.

This article will describe each of them, the information they contain, available tools to recover them and the existing detection risks. While no new technique will be introduced here, this summary should still help in future internal network or red team assessments. Finally, even if this listing tries to be exhaustive, some techniques or tools might be missing.

LSASS

Recovering LSASS memory is probably the most known technique to retrieve sensitive secrets. Indeed, this process is responsible for handling authentication on Windows and can contain the following elements:

• User / Machine hashes.
• Cleartext credentials (if wdigest is enabled).
• Kerberos tickets (TGT and ST).
• DPAPI cached keys.

As such, successfully recovering these elements is often the best way to elevate privileges from a first compromise to Domain Administrator in an Active Directory environment. As this process is highly sensitive, attackers and defenders are battling, antivirus are getting better and new techniques are regularly discovered to bypass them.

Moreover, Microsoft has introduced different protections over the years to protect against these attacks such as RunAsPPL and Credential Guards.

As this article is focused on the offensive side, let's talk about the different techniques one can use to retrieve LSASS secrets.

Userland techniques

While many tools have been published over the years, two of them, that are actively maintained, are enough to cover most credential recovery methods: lsassy and nanodump.

Lsassy

Lsassy has been released in 2019 and is still maintained by its creator hackndo. This Python tool mainly focuses on performing dumping and parsing operations remotely.

Dumping is implemented by interfacing with various external tools:

• comsvcs
• comsvcs_stealth
• dllinject
• procdump
• procdump_embedded
• dumpert
• dumpertdll
• ppldump
• ppldump_embedded
• mirrordump
• mirrordump_embedded
• wer
• EDRSandBlast
• nanodump
• rdrleakdiag
• silentprocessexit
• sqldumper

Memory parsing relies on the pypykatz project.

However nowadays, using lsassy is not advised if discretion is needed. Indeed, code execution is performed using impacket implementations such as scheduled tasks, wmi or smb, which are often detected by antiviruses.

Nanodump

Nanodump was released in 2021 and is developed in C by S4ntiagoP. The compiled binary can be executed using lsassy or the traditional RDP, WinRM, etc. It supports the following dumping methods:

• Duplicate a high privileged existing LSASS handle.
• Duplicate a low privileged existing LSASS handle and then elevate it.
• Leak an LSASS handle into nanodump via seclogon.
• Leak an LSASS handle into another process via seclogon and duplicate it.
• Make seclogon open a handle to LSASS and duplicate it.
• Open a handle to LSASS using a fake calling stack.
• Force WerFault.exe to dump LSASS via SilentProcessExit.
• Force WerFault.exe to dump LSASS via Shtinkering.

The tool supports creating an invalid memory dump to prevent antiviruses from deleting it. However, it seems the implemented techniques are nowadays blocked by most detection software. Indeed, the functions of the Windows API used to perform userland memory dumps are heavily monitored by AV products, using hooks or Event Tracing for Windows (ETW).

Using kernel drivers

As the previously described tools are frequently blocked or detected by antivirus products, other tools have been developed to leverage known vulnerable drivers signed by Microsoft in order to gain read/write primitives in the Windows kernel. A website lists known vulnerable drivers that can be used for such tools: https://www.loldrivers.io/.

It is however important to note that loading drivers on Windows is usually done using a service, which might raise flags or alerts when you are in the context of a red team.

Physmem2profit

Physmem2profit is a tool developed in C# and Python released in 2020 by WithSecureLabs. It has a client / server architecture where the client is Python-based (but Python 3.7 and later is not supported), and the server is run on the compromised host and is built in C#. The client connects to the server and mounts the WinpMem driver, offering direct physical memory access. The server will then try to find the LSASS process using rekall and reconstruct a dump.

Because the dump is constructed on the attacker's machine, it does not touch the compromised host, avoiding potential antivirus detection.

Even if this tool works properly, there are some drawbacks:

• The rekall framework is deprecated, making the discovery of the LSASS process not reliable on recent Windows versions and builds.
• Dumping an LSASS process is usually pretty long (~10 minutes) because of the architecture of the tool.
• Reconstructed dumps are also not reliable, and it may be necessary to restart the client in order to retrieve credentials of a connected user.

EDRSandblast

EDRSandblast is a tool developed in C and released in 2021 by Wavestone. It compiles as an executable that has to be run on the victim's machine using RDP, WinRM or other methods. It currently supports two drivers: RTCore64 and DBUtils_2_3 but can be extended with other vulnerable drivers.

This tool uses the driver's read and write primitives to temporarily disable all antivirus hooks and/or detection mechanisms before creating a memory dump of the LSASS process. It is very reliable even if some dumps are not usable and antivirus might still catch the dump being written to the disk. Writing the dump on a network share might help preventing such detection. The tool's GitHub page details how these actions are performed if you are interested in the technical implementation.

The tool requires offsets in ntoskrnl.exe to properly work, either by providing a CSV file or using the --internet switch. This option is not advised when stealth is required. Therefore, it will be necessary to update the offsets before the tool can work.

Moreover, EDRSandblast offers the possibility to enable the wdigest feature on a live system without requiring a reboot to retrieve credentials of new interactive connections. This feature also requires offsets for wdigest.dll.

DumpIt

DumpIt is a closed source tool developed by Comae and mainly used for forensic analysis, that uses a driver to dump all the physical memory into a file. Because the dumps size depends on the amount of memory available, retrieving one from a remote system is usually slow. To ease this process, MemProcFS allows mounting memory dumps, then, the minidump folder of the LSASS contains a dump that is compatible with mimikatz or pypykatz.

Moreover, such dumps can be used by the volatility framework to retrieve various information such as registry secrets. However, at the time of writing, there exists no plugin on the latest version of the framework to reconstruct a minidump or retrieve information from the LSASS process.

Registry secrets

Windows registry hives also contain different secrets and retrieving them can often yield privileged accounts within an Active Directory environment. The following secrets are stored in this base:

• SAM secrets.
• LSA secrets (Local Security Authority).
• Software secrets.

SAM

The SAM base (Security Account Manager) holds secrets related to local accounts. Querying information on this hive requires SYSTEM authority or to have the SeBackupPrivilege to make a backup of the hive.

Moreover, such sensitive information is stored encrypted with the bootkey. The latter is unique to each computer and is computed from information inside the HKLM\SYSTEM\CurrentControlSet\Control\Lsa registry key.

LSA secrets

LSA secrets are stored in the SECURITY\Policy\Secrets key and are encrypted using the LsaKey which itself is derived from the bootkey. Here as well, SYSTEM privileges are required to query the necessary keys. The following secrets can be found, among others:

• DPAPI_SYSTEM which contains the DPAPI machine and user key for local DPAPI.
• NL$KM which contains an encryption key for the MsCache also stored in the SECURITY hive (SECURITY\Cache). MsCache are the latest hashed credentials for domain users.
• $MACHINE.ACC contains the computer account credentials when joined to an Active Directory domain.
• DEFAULTPASSWORD is the default password when the auto-logon feature is configured.
• Keys starting with _SC_ corresponds to non-interactive service account credentials that could be local or for a domain user.

Tooling

To recover the hives of an online system, two native utilities can be used: reg and vssadmin (shadow copy):

> reg save HKLM\SAM sam
> vssadmin create shadow /for=C:
> copy \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy1\Windows\System32\config\SAM SAM

Their use is however often detected and blocked by commonly used security products.

Secretsdump.py can then be used to extract the secrets stored within the hives:

$ secretsdump.py -sam sam -security security -system system local

This tool can also be used remotely to perform all operations automatically on a live system, by performing the following actions:

• Starting the SvcRegistry service, if not already started.
• Using the previous service to perform a reg save.
• Retrieving the extracted hives over SMB.
• Parsing the files locally.

As for most Impacket tools, its use is often detected and blocked. For this reason, we developed SharpSecretsdump, a C# version to perform these actions on a live system. It has the following advantages:

• Runs natively on Windows.
• Does not have any dependence.
• Can be used easily from PowerShell with reflection.

DPAPI

DPAPI is an acronym for Data Protection API and has been integrated to Windows 2000. This mechanism, allowing data protection by encryption, is widely used by Microsoft and other software such as Chrome, Edge or SCCM. When a software offers a "remember me" or "save credentials" feature, DPAPI is probably used to encrypt credentials before storing them.

The API is very simple and makes its usage straightforward and not error-prone:

DPAPI_IMP BOOL CryptProtectData(
  [in]           DATA_BLOB                 *pDataIn,
  [in, optional] LPCWSTR                   szDataDescr,
  [in, optional] DATA_BLOB                 *pOptionalEntropy,
  [in]           PVOID                     pvReserved,
  [in, optional] CRYPTPROTECT_PROMPTSTRUCT *pPromptStruct,
  [in]           DWORD                     dwFlags,
  [out]          DATA_BLOB                 *pDataOut
);

Each parameter is self-explanatory and the pOtionalEntropy is almost always null. The interesting parameter is dwFlags:

[in] dwFlags

This parameter can be one of the following flags.

Value	Meaning
CRYPTPROTECT_LOCAL_MACHINE	When this flag is set, it associates the data encrypted with the current computer instead of with an individual user. Any user on the computer on which CryptProtectData is called can use CryptUnprotectData to decrypt the data.
CRYPTPROTECT_UI_FORBIDDEN	This flag is used for remote situations where presenting a user interface (UI) is not an option. When this flag is set and a UI is specified for either the protect or unprotect operation, the operation fails and GetLastError returns the ERROR_PASSWORD_RESTRICTION code.
CRYPTPROTECT_AUDIT	This flag generates an audit on protect and unprotect operations. Audit log entries are recorded only if szDataDescr is not NULL and not empty.

Except CRYPTPROTECT_LOCAL_MACHINE, the other flags will make the data encrypted using user credentials rather than the system DPAPI keys. A .NET version of this API is also available.

Decryption is then performed using the CryptUnprotectData function and is very similar.

Let's talk briefly about the implementation of DPAPI. Its encryption mechanism relies on masterkeys (MK), used to encrypt the data. Masterkeys are encrypted with a derivative from the user's password or the DPAPI system key. The following diagram is a high level view of DPAPI's inner working:

• A masterkey's filename is a lowercase GUID, e.g. 4f31fb52-7d53-45be-b531-9f82a0682a43.
• A masterkey file can contain two different masterkeys, when joined to a domain, one is encrypted with derivated user password while the other is encrypted with the DPAPI domain backup key. The domain backup key can be recovered with Domain Admin privileges, this key is never changed.
• They are rotated every 3 months or when the user's password is changed.
• They are cached decrypted in LSASS.
• They are considered "System files" and not displayed by default with commands or inside an explorer. For them to be shown in the explorer, the "Hide protected operating system files" option must be unchecked. In PowerShell, the -Hidden option can be specified when using Get-ChildItem.

Other files related to masterkeys exist. The Preferred file inside the same folder contains the GUID of the currently used masterkey whereas the CREDHIST file, one folder above, contains information to decrypt older masterkeys.

The masterkey decryption will have different prerequisites depending on the context, as shown in the previous diagram:

• Domain user: its password or NT hash, or the domain backup key.
• Local user: its password or SHA1 hash.
• Local DPAPI: both systemand security hives to compute the key.

Different types of secrets are encrypted using DPAPI:

• Credentials
• Vault
• DPAPI blob
• RSA / NGC

Credentials

Credentials is a type of secrets that uses DPAPI and is handled by Windows. An interface is available in the Control Panel under Credential Manager where users can add credentials manually. Windows will also store user-specific credentials there, such as One Drive and Skype tokens, or RDP credentials. A credential named didlogical is also present on most systems and stores information about Windows Live applications.

Machine credentials also exist. For example, when creating a scheduled task with non-interactive logon, the user credentials are encrypted in such format. They are usually interesting in the context of a penetration test because privileged account credentials can be discovered.

Each credential is saved as a file, in C:/Users/User/AppData/Local/Microsoft/Credentials/ for users and in C:/Windows/System32/config/systemprofile/AppData/Local/Microsoft/Credentials/ for the system. As for masterkeys, they are considered "system files". They all have a 32 hexadecimal characters filename.

Vault

The vault is also accessible through the Credential Manager, but its use is rare. Indeed, it is mainly used when saving credentials in Internet Explorer and for Edge versions before December 2020 (Edge has switched to a Chromium base now).

Each credential is stored in a file that matches the following path: AppData/*/Microsoft/Vault/[0-9a-fA-F-]+/[0-9a-fA-F]{40}/*.vcrd.

Other files are related to the vault such as vpol and vsch. The vpol file associated to a vault is required to recover credentials as it contains the vault schema.

As for masterkeys, they are considered "system files".

DPAPI blob

A DPAPI blob is the output of the CryptProtectData function. Its structure is not officially documented but has been reversed:

typedef struct _KULL_M_DPAPI_BLOB {
	DWORD	dwVersion;
	GUID	guidProvider;
	DWORD	dwMasterKeyVersion;
	GUID	guidMasterKey;
	DWORD	dwFlags;
	
	DWORD	dwDescriptionLen;
	PWSTR	szDescription;
	
	ALG_ID	algCrypt;
	DWORD	dwAlgCryptLen;
	
	DWORD	dwSaltLen;
	PBYTE	pbSalt;
	
	DWORD	dwHmacKeyLen;
	PBYTE	pbHmackKey;
	
	ALG_ID	algHash;
	DWORD	dwAlgHashLen;

	DWORD	dwHmac2KeyLen;
	PBYTE	pbHmack2Key;
	
	DWORD	dwDataLen;
	PBYTE	pbData;
	
	DWORD	dwSignLen;
	PBYTE	pbSign;
} KULL_M_DPAPI_BLOB, *PKULL_M_DPAPI_BLOB;

As of today, dwVersion is always 1 and, guidProvider is DF9D8CD0-1501-11D1-8C7A-00C04FC297EB and dwMasterKeyVersion is also 1. DPAPI blobs are stored differently for each software implementation but are usually stored as files or base64-encoded strings in a database. Therefore, knowing the previous information, it is easy to fingerprint a blob when encountering binary data:

$ hd blob1 
00000000  01 00 00 00 d0 8c 9d df  01 15 d1 11 8c 7a 00 c0  |.............z..|
00000010  4f c2 97 eb 01 00 00 00  b0 4f 23 6c 66 19 43 4b  |O........O#lf.CK|
00000020  a3 17 23 4c 19 10 73 61  00 00 00 00 02 00 00 00  |..#L..sa........|
[...]

For example, Wi-Fi credentials are stored as DPAPI blobs inside the following files: C:\ProgramData\Microsoft\Wlansvc\Profiles\Interfaces\*.xml. They are encrypted with machine's user masterkeys.

Chrome also uses this feature. The JSON file C:\Users\<user>\AppData\Local\Google\Chrome\User Data\Local State contains a key named encrypted_key with a DPAPI blob prefixed with the string DPAPI. This secret is used to encrypt and decrypt all saved passwords and cookie values.

Other examples include:

• rdg file generated from RDP connection files with credentials.
• Azure CLI credentials.
• SCCM NAA.

RSA / NGC

NGC is an acronym for Next Generation Cryptography which is basically DPAPI with different crypto providers such as "Microsoft Software Key Storage Provider" which uses RSA. Its usage is also rare, and we never needed to decrypt any information that was encrypted this way.

If you are interested in DPAPI, a detailed article goes into more details regarding the cryptographic implementation.

Tooling

There are not many native tools to perform DPAPI operations. The cmdkey /list command can be used to list credentials when executed in the context of a user. Moreover, Wi-Fi passwords can also be recovered with netsh:

> netsh wlan show profile

> netsh wlan show profile SSID key=clear

To decrypt DPAPI blobs, PowerShell can be used directly on the targeted system. The following example uses the LocalMachine context:

PS C:\Users\user> $a = [System.Convert]::FromBase64String("AQAAANCMnd[...]")
PS C:\Users\user> $b = [System.Security.Cryptography.ProtectedData]::Unprotect($a, $null, [System.Security.Cryptography.DataProtectionScope]::LocalMachine)
PS C:\Users\user> [System.Text.Encoding]::ASCII.GetString($b)
Hello World

On the other hand, many custom tools exist with some of them usable on a live system:

• LaZagne
• pypykatz - dpapi module
• mimikatz
• SharpDPAPI

Others can be used offline after recovering the necessary files:

• pypykatz - dpapi module
• dpapi.py - impacket
• mimikatz
• SharpDPAPI
• dpapilab-ng
• diana

Moreover, recent tools have been released to automate everything:

• DonPAPI
• dploot

Because these tools do not necessarily cover every case, it is important to know how to perform decryption manually. The dpapi.py script from Impacket is perfect for this.

When decrypting a DPAPI secret, there are always 3 steps to be performed:

1. Identify the required masterkey.
2. Decrypt it.
3. Decrypt the secret.

Dpapi.py allows decrypting the majority of DPAPI secrets such as: credentials, vaults and DPAPI blobs (unprotect). The following example shows the offline decryption of a DPAPI blob retrieved with a call to CryptProtectData, in the context of a user:

$ dpapi.py unprotect -file blob
[BLOB]
Version          :        1 (1)
Guid Credential  : DF9D8CD0-1501-11D1-8C7A-00C04FC297EB
MasterKeyVersion :        1 (1)
Guid MasterKey   : 1F2A5BF7-4F38-4F61-B1AE-7B5731032A90
Flags            :        0 ()
Description      : 
CryptAlgo        : 00006610 (26128) (CALG_AES_256)
Salt             : b'fdefe12ca5255e4ee432d38211ae02e7bd0618313fc2f27680ea64579fbcb93e'
HMacKey          : b''
HashAlgo         : 0000800e (32782) (CALG_SHA_512)
HMac             : b'101e04a3c5215d75f6c39c4f2df80f65d6ec4bdfe8b1f57470c5aa4f5fafb678'
Data             : b'61ce6366feed014a0465a965e2efc78a'
Sign             : b'44a66903b3c08b748dd17f7105147b9144343e88f1d04ef63ae1ec3e4b83482fd50313dcec533fa575f93ffc16af9fda31a1bf72484602fee6667450625f2f0a'

Cannot decrypt (specify -key or -sid whenever applicable) 

The 1F2A5BF7-4F38-4F61-B1AE-7B5731032A90 masterkey is required, let's decrypt it:

$ dpapi.py masterkey -file 1f2a5bf7-4f38-4f61-b1ae-7b5731032a90 -password password -sid S-1-5-21-3258530061-3600341354-3570646120-1000
[MASTERKEYFILE]
Version     :        2 (2)
Guid        : 1f2a5bf7-4f38-4f61-b1ae-7b5731032a90
Flags       :        5 (5)
Policy      :       15 (21)
MasterKeyLen: 000000b0 (176)
BackupKeyLen: 00000090 (144)
CredHistLen : 00000014 (20)
DomainKeyLen: 00000000 (0)

Decrypted key with User Key (SHA1)
Decrypted key: 0x6de4c0044f613034cf73a764d89311e33ca29955c9f32bac77992d0417edeb5e19da8d6fea7a969be92521afc0ba1c77701fd7573498e0b4a26d8242c9e2ba36

The SID of the user can be recovered in the path containing masterkeys: C:\users\user\appdata\roaming\microsoft\protect\S-1-5-21-3258530061-3600341354-3570646120-1000\. The masterkey can also be decrypted differently depending on the context: SHA1 for local users or NT hash for domain users. The -pvk option can be used with the domain backup key, while the -key argument should be used for system DPAPI in conjunction with the retrieved keys (from secretsdump.py for example) or by specifying the -system and -security switches.

And now the final step:

$ dpapi.py unprotect -file blob -key 0x6de4c0044f613034cf73a764d89311e33ca29955c9f32bac77992d0417edeb5e19da8d6fea7a969be92521afc0ba1c77701fd7573498e0b4a26d8242c9e2ba36
Successfully decrypted data
0000  48 65 6C 6C 6F 20 57 6F  72 6C 64  Hello World

For automated offline approaches and more complex use cases not covered by dpapi.py, diana and dpapilab-ng also contain many helpful scripts.

Side notes

The update of masterkeys is performed when a user is changing its password through the Windows GUI, therefore, some actions changing the password of a user might desynchronize masterkeys and make them undecryptable with the latest password (e.g. RPC calls, net user, etc.).

Moreover, masterkeys can also be used to perform offline brute force of a user's password using John The Ripper:

$ DPAPImk2john.py -S S-1-5-21-3258530061-3600341354-3570646120-1000 -c local -mk 1f2a5bf7-4f38-4f61-b1ae-7b5731032a90 
$DPAPImk$2*1*S-1-5-21-3258530061-3600341354-3570646120-1000*aes256*sha512*8000*46717b1fd50eb3d12559ed19016bd2dc*288*a897faef12ebdc3bf0721a938d3de72f348f51b6e0236782f664f0d3a21b1c0bf49da1f3671014f636aad84a5d5aa9946a5a240028e3d5e35cbcca03902f035e2d21ccbbbcbdb65a8316595d3da821cc0858a48e5f34275b742be30859c57b0742984f7692f3eced795c39a58d2fc6a9e7b88031aad8020f11695981edc6c06e69863c775ee325523d74ebcbb9a3e052

Conclusion

Windows secrets extraction is an essential step, especially in red team assessments where trophies may be outside an Active Directory environment. As such, it is important to understand where to find sensitive information and how to decrypt it. This article only talked about specific Windows secrets, but other software (Firefox, mRemoteNG, etc.) may also store their secrets differently, and should not be omitted.