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Active Directory Methodology
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Active Directory allows network administrators to create and manage domains, users, and objects within a network. For example, an admin can create a group of users and give them specific access privileges to certain directories on the server. As a network grows, Active Directory provides a way to organize a large number of users into logical groups and subgroups, while providing access control at each level.
The Active Directory structure includes three main tiers: 1) domains, 2) trees, and 3) forests. Several objects (users or devices) that all use the same database may be grouped in to a single domain. Multiple domains can be combined into a single group called a tree. Multiple trees may be grouped into a collection called a forest. Each one of these levels can be assigned specific access rights and communication privileges.
Main concepts of an Active Directory:
- 1.Directory – Contains all the information about the objects of the Active directory
- 2.Object – An object references almost anything inside the directory (a user, group, shared folder...)
- 3.Domain – The objects of the directory are contained inside the domain. Inside a "forest" more than one domain can exist and each of them will have their own objects collection.
- 4.Tree – Group of domains with the same root. Example: dom.local, email.dom.local, www.dom.local
- 5.Forest – The forest is the highest level of the organization hierarchy and is composed by a group of trees. The trees are connected by trust relationships.
Active Directory provides several different services, which fall under the umbrella of "Active Directory Domain Services," or AD DS. These services include:
- 1.Domain Services – stores centralized data and manages communication between users and domains; includes login authentication and search functionality
- 2.Certificate Services – creates, distributes, and manages secure certificates
- 3.Lightweight Directory Services – supports directory-enabled applications using the open (LDAP) protocol
- 4.Directory Federation Services – provides single-sign-on (SSO) to authenticate a user in multiple web applications in a single session
- 5.Rights Management – protects copyrighted information by preventing unauthorized use and distribution of digital content
- 6.DNS Service – Used to resolve domain names.
AD DS is included with Windows Server (including Windows Server 10) and is designed to manage client systems. While systems running the regular version of Windows do not have the administrative features of AD DS, they do support Active Directory. This means any Windows computer can connect to a Windows workgroup, provided the user has the correct login credentials.
From: https://techterms.com/definition/active_directory
To learn how to attack an AD you need to understand really good the Kerberos authentication process.
Read this page if you still don't know how it works.
You can take a lot to https://wadcoms.github.io/ to have a quick view of which commands you can run to enumerate/exploit an AD.
If you just have access to an AD environment but you don't have any credentials/sessions you could:
- Pentest the network:
- Scan the network, find machines and open ports and try to exploit vulnerabilities or extract credentials from them (for example, printers could be very interesting targets.
- Enumerating DNS could give information about key servers in the domain as web, printers, shares, vpn, media, etc.
gobuster dns -d domain.local -t 25 -w /opt/Seclist/Discovery/DNS/subdomain-top2000.txt
- Check for null and Guest access on smb services (this won't work on modern Windows versions):
enum4linux -a -u "" -p "" <DC IP> && enum4linux -a -u "guest" -p "" <DC IP>smbmap -u "" -p "" -P 445 -H <DC IP> && smbmap -u "guest" -p "" -P 445 -H <DC IP>smbclient -U '%' -L //<DC IP> && smbclient -U 'guest%' -L //- A more detailed guide on how to enumerate a SMB server can be found here:
- Enumerate Ldap
nmap -n -sV --script "ldap* and not brute" -p 389 <DC IP>- A more detailed guide on how to enumerate LDAP can be found here (pay special attention to the anonymous access):
- Poison the network
- Extract usernames/names from internal documents, social media, services (mainly web) inside the domain environments and also from the publicly available.
- If you find the complete names of company workers, you could try different AD username conventions (read this). The most common conventions are: NameSurname, Name.Surname, NamSur (3letters of each), Nam.Sur, NSurname, N.Surname, SurnameName, Surname.Name, SurnameN, Surname.N, 3 random letters and 3 random numbers (abc123).
- Kerbrute enum: When an invalid username is requested the server will respond using the Kerberos error code KRB5KDC_ERR_C_PRINCIPAL_UNKNOWN, allowing us to determine that the username was invalid. Valid usernames will illicit either the TGT in a AS-REP response or the error KRB5KDC_ERR_PREAUTH_REQUIRED, indicating that the user is required to perform pre-authentication.
./kerbrute_linux_amd64 userenum -d lab.ropnop.com --dc 10.10.10.10 usernames.txt #From https://github.com/ropnop/kerbrute/releases
nmap -p 88 --script=krb5-enum-users --script-args="krb5-enum-users.realm='DOMAIN'" <IP>
Nmap -p 88 --script=krb5-enum-users --script-args krb5-enum-users.realm='<domain>',userdb=/root/Desktop/usernames.txt <IP>
msf> use auxiliary/gather/kerberos_enumusers
crackmapexec smb dominio.es -u '' -p '' --users | awk '{print $4}' | uniq
- OWA (Outlook Web Access) Server
If you found one of these servers in the network you can also perform user enumeration against it. For example, you could use the tool MailSniper:
ipmo C:\Tools\MailSniper\MailSniper.ps1
# Get info about the domain
Invoke-DomainHarvestOWA -ExchHostname [ip]
# Enumerate valid users from a list of potential usernames
Invoke-UsernameHarvestOWA -ExchHostname [ip] -Domain [domain] -UserList .\possible-usernames.txt -OutFile valid.txt
# Password spraying
Invoke-PasswordSprayOWA -ExchHostname [ip] -UserList .\valid.txt -Password Summer2021
# Get addresses list from the compromised mail
Get-GlobalAddressList -ExchHostname [ip] -UserName [domain]\[username] -Password Summer2021 -OutFile gal.txt
You can find lists of usernames in this github repo **** and this one (statistically-likely-usernames).
However, you should have the name of the people working on the company from the recon step you should have performed before this. With the name and surname you could used the script namemash.py to generate potential valid usernames.
Ok, so you know you have already a valid username but no passwords... Then try:
- ASREPRoast: If a user doesn't have the attribute DONT_REQ_PREAUTH you can request a AS_REP message for that user that will contain some data encrypted by a derivation of the password of the user.
- Password Spraying: Let's try the most common passwords with each of the discovered users, maybe some user is using a bad password (keep in mind the password policy!).
- Note that you can also spray OWA servers to try to get access to the users mail servers.
You might be able to obtain some challenge hashes to crack poisoning some protocols of the network:
If you have managed to enumerate the active directory you will have more emails and a better understanding of the network. You might be able to to force NTML relay attacks **** to get access to the AD env.
If you can access other PCs or shares with the null or guest user you could place files (like a SCF file) that if somehow accessed will trigger an NTML authentication against you so you can steal the NTLM challenge to crack it:
For this phase you need to have compromised the credentials or a session of a valid domain account. If you have some valid credentials or a shell as a domain user, you should remember that the options given before are still options to compromise other users.
Before start the authenticated enumeration you should know what is the Kerberos double hop problem.
Having compromised an account is a big step to start compromising the whole domain, because you are going to be able to start the Active Directory Enumeration:
Regarding ASREPRoast you can now find every possible vulnerable user, and regarding Password Spraying you can get a list of all the usernames and try the password of the compromised account, empty passwords and new promising passwords.
- Another amazing tool for recon in an active directory is BloodHound. It is not very stealthy (depending on the collection methods you use), but if you don't care about that, you should totally give it a try. Find where users can RDP, find path to other groups, etc.
- A tool with GUI that you can use to enumerate the directory is AdExplorer.exe from SysInternal Suite.
- You can also search in the LDAP database with ldapsearch to look for credentials in fields userPassword & unixUserPassword, or even for Description. cf. Password in AD User comment on PayloadsAllTheThings for other methods.
- You could also try automated tools as:
- Extracting all domain usersIt's very easy to obtain all the domain usernames from Windows (
net user /domain,Get-DomainUserorwmic useraccount get name,sid). In Linux, you can use:GetADUsers.py -all -dc-ip 10.10.10.110 domain.com/usernameorenum4linux -a -u "user" -p "password" <DC IP>
Even if this Enumeration section looks small this is the most important part of all. Access the links (mainly the one of cmd, powershell, powerview and BloodHound), learn how to enumerate a domain and practice until you feel comfortable. During an assessment, this will be the key moment to find your way to DA or to decide that nothing can be done.
The goal of Kerberoasting is to harvest TGS tickets for services that run on behalf of domain user accounts. Part of these TGS tickets are encrypted wit keys derived from user passwords. As a consequence, their credentials could be cracked offline.
More about this in:
Once you have obtained some credentials you could check if you have access to any machine. For that matter, you could use CrackMapExec to attempt connecting on several servers with different protocols, accordingly to your ports scans.
If you have compromised credentials or a session as a regular domain user and you have access with this user to any machine in the domain you should try to find your way to escalate privileges locally and looting for credentials. This is because only with local administrator privileges you will be able to dump hashes of other users in memory (LSASS) and locally (SAM).
There is a complete page in this book about local privilege escalation in Windows and a checklist. Also, don't forget to use WinPEAS.
It's very unlikely that you will find tickets in the current user giving you permission to access unexpected resources, but you could check:
## List all tickets (if not admin, only current user tickets)
.\Rubeus.exe triage
## Dump the interesting one by luid
.\Rubeus.exe dump /service:krbtgt /luid:<luid> /nowrap
[IO.File]::WriteAllBytes("ticket.kirbi", [Convert]::FromBase64String("<BASE64_TICKET>"))
If you have managed to enumerate the active directory you will have more emails and a better understanding of the network. You might be able to to force NTML relay attacks.
Now that you have some basic credentials you should check if you can find any interesting files being shared inside the AD. You could do that manually but it's a very boring repetitive task (and more if you find hundreds of docs you need to check).
If you can access other PCs or shares you could place files (like a SCF file) that if somehow accessed will trigger an NTML authentication against you so you can steal the NTLM challenge to crack it:
This vulnerability allowed any authenticated user to compromise the domain controller.
For the following techniques a regular domain user is not enough, you need some special privileges/credentials to perform these attacks.
Hopefully you have managed to compromise some local admin account using AsRepRoast, Password Spraying, Kerberoast, Responder including relaying, EvilSSDP, escalating privileges locally.
Then, its time to dump all the hashes in memory and locally.
Read this page about different ways to obtain the hashes.
Once you have the hash of a user, you can use it to impersonate it.
You need to use some tool that will perform the NTLM authentication using that hash, or you could create a new sessionlogon and inject that hash inside the LSASS, so when any NTLM authentication is performed, that hash will be used. The last option is what mimikatz does.
Read this page for more information.
This attack aims to use the user NTLM hash to request Kerberos tickets, as an alternative to the common Pass The Hash over NTLM protocol. Therefore, this could be especially useful in networks where NTLM protocol is disabled and only Kerberos is allowed as authentication protocol.
This attack is similar to Pass the Key, but instead of using hashes to request a ticket, the ticket itself is stolen and used to authenticate as its owner.
If you have the hash or password of a local administrator you should try to login locally to other PCs with it.
# Local Auth Spray (once you found some local admin pass or hash)
## --local-auth flag indicate to only try 1 time per machine
crackmapexec smb --local-auth 10.10.10.10/23 -u administrator -H 10298e182387f9cab376ecd08491764a0 | grep +
Note that this is quite noisy and LAPS would mitigate it.
If a user has privileges to access MSSQL instances, he could be able to use it to execute commands in the MSSQL host (if running as SA), steal the NetNTLM hash or even perform a relay attack.
Also, if a MSSQL instance is trusted (database link) by a different MSSQL instance. If the user has privileges over the trusted database, he is going to be able to use the trust relationship to execute queries also in the other instance. These trusts can be chained and at some point the user might be able to find a misconfigured database where he can execute commands.
The links between databases work even across forest trusts.
If you find any Computer object with the attribute ADS_UF_TRUSTED_FOR_DELEGATION and you have domain privileges in the computer, you will be able to dump TGTs from memory of every users that logins onto the computer.
So, if a Domain Admin logins onto the computer, you will be able to dump his TGT and impersonate him using Pass the Ticket.
Thanks to constrained delegation you could even automatically compromise a Print Server (hopefully it will be a DC).
If a user or computer is allowed for "Constrained Delegation" it will be able to impersonate any user to access some services in a computer.
Then, if you compromise the hash of this user/computer you will be able to impersonate any user (even domain admins) to access some services.
It's possible to gain code execution with elevated privileges on a remote computer if you have WRITE privilege on that computer's AD object.
The compromised user could have some interesting privileges over some domain objects that could let you move laterally/escalate privileges.
If you can find any Spool service listening inside the domain, you may be able to abuse is to obtain new credentials and escalate privileges.
More information about how to abuse Spooler services here.
If other users access the compromised machine, it's possible to gather credentials from memory and even inject beacons in their processes to impersonate them.
Usually users will access the system via RDP, so here you have how to performa couple of attacks over third party RDP sessions:
LAPS allows you to manage the local Administrator password (which is randomised, unique, and changed regularly) on domain-joined computers. These passwords are centrally stored in Active Directory and restricted to authorised users using ACLs. If you have enough permission to read these passwords you could move to other computers.
Gathering certificates from the compromised machine could be a way to escalate privileges inside the environment:
If vulnerable templates are configured it's possible to abuse them to escalate privileges:
Once you get Domain Admin or even better Enterprise Admin privileges, you can dump the domain database: ntds.dit.
Some of the techniques discussed before can be used for persistence.
For example you could:
- Set-DomainObject -Identity <username> -Set @{serviceprincipalname="fake/NOTHING"}r
- Set-DomainObject -Identity <username> -XOR @{UserAccountControl=4194304}
- Add-DomainObjectAcl -TargetIdentity "DC=SUB,DC=DOMAIN,DC=LOCAL" -PrincipalIdentity bfarmer -Rights DCSync
The Silver ticket attack is based on crafting a valid TGS for a service once the NTLM hash of service is owned (like the PC account hash). Thus, it is possible to gain access to that service by forging a custom TGS as any user (like privileged access to a computer).
A valid TGT as any user can be created using the NTLM hash of the krbtgt AD account. The advantage of forging a TGT instead of TGS is being able to access any service (or machine) in the domain ad the impersonated user.
These are like golden tickets forged in a way that bypasses common golden tickets detection mechanisms.
Having certificates of an account or being able to request them is a very good way to be able to persist in the users account (even if he changes the password):
Using certificates is also possible to persist with high privileges inside the domain:
The Access Control List (ACL) of the AdminSDHolder object is used as a template to copy permissions to all “protected groups” in Active Directory and their members. Protected groups include privileged groups such as Domain Admins, Administrators, Enterprise Admins, and Schema Admins, Backup Operators and krbtgt.
By default, the ACL of this group is copied inside all the "protected groups". This is done to avoid intentional or accidental changes to these critical groups. However, if an attacker modifies the ACL of the group AdminSDHolder for example, giving full permissions to a regular user, this user will have full permissions on all the groups inside the protected group (in an hour).
And if someone tries to delete this user from the Domain Admins (for example) in an hour or less, the user will be back in the group.
More information about AdminDSHolder Group here.
There is a local administrator account inside each DC. Having admin privileges in this machine, you can use mimikatz to dump the local Administrator hash. Then, modifying a registry to activate this password so you can remotely access to this local Administrator user.
You could give some special permissions to a user over some specific domain objects that will let the user escalate privileges in the future.
The security descriptors are used to store the permissions an object have over an object. If you can just make a little change in the security descriptor of an object, you can obtain very interesting privileges over that object without needing to be member of a privileged group.
Modify LSASS in memory to create a master password that will work for any account in the domain.
Learn what is a SSP (Security Support Provider) here.
You can create you own SSP to capture in clear text the credentials used to access the machine.\
It registers a new Domain Controller in the AD and uses it to push attributes (SIDHistory, SPNs...) on specified objects without leaving any logs regarding the modifications. You need DA privileges and be inside the root domain.
Note that if you use wrong data, pretty ugly logs will appear.
Previously we have discussed about how to escalate privileges if you have enough permission to read LAPS passwords. However, these passwords can also be used to maintain persistence.
Check:
Microsoft considers that the domain isn't a Security Boundary, the Forest is the security Boundary. This means that if you compromise a domain inside a Forest you might be able to compromise the entire Forest.
At a high level, a domain trust establishes the ability for users in one domain to authenticate to resources or act as a security principal in another domain.
Essentially, all a trust does is linking up the authentication systems of two domains and allowing authentication traffic to flow between them through a system of referrals.
When 2 domains trust each other they exchange keys, these keys are going to be saved in the DCs of each domains (2 keys per trust direction, latest and previous) and the keys will be the base of the trust.
When a user tries to access a service on the trusting domain it will request an inter-realm TGT to the DC of its domain. The DC wills serve the client this TGT which would be encrypted/signed with the inter-realm key (the key both domains exchanged). Then, the client will access the DC of the other domain and will request a TGS for the service using the inter-realm TGT. The DC of the trusting domain will check the key used, if it's ok, it will trust everything in that ticket and will serve the TGS to the client.
It's important to notice that a trust can be 1 way or 2 ways. In the 2 ways options, both domains will trust each other, but in the 1 way trust relation one of the domains will be the trusted and the other the trusting domain. In the last case, you will only be able to access resources inside the trusting domain from the trusted one.
If Domain A trusts Domain B, A is the trusting domain and B ins the trusted one. Moreover, in Domain A, this would be an Outbound trust; and in Domain B, this would be an Inbound trust.
Different trusting relationships
- Parent-Child – part of the same forest – a child domain retains an implicit two-way transitive trust with its parent. This is probably the most common type of trust that you’ll encounter.
- Cross-link – aka a “shortcut trust” between child domains to improve referral times. Normally referrals in a complex forest have to filter up to the forest root and then back down to the target domain, so for a geographically spread out scenario, cross-links can make sense to cut down on authentication times.
- External – an implicitly non-transitive trust created between disparate domains. “External trusts provide access to resources in a domain outside of the forest that is not already joined by a forest trust.” External trusts enforce SID filtering, a security protection covered later in this post.
- Tree-root – an implicit two-way transitive trust between the forest root domain and the new tree root you’re adding. I haven’t encountered tree-root trusts too often, but from the Microsoft documentation, they’re created when you create a new domain tree in a forest. These are intra-forest trusts, and they preserve two-way transitivity while allowing the tree to have a separate domain name (instead of child.parent.com).
- Forest – a transitive trust between two forest root domain. Forest trusts also enforce SID filtering.
- MIT – a trust with a non-Windows RFC4120-compliant Kerberos domain. I hope to dive more into MIT trusts in the future.
- A trust relationship can also be transitive (A trust B, B trust C, then A trust C) or non-transitive.
- A trust relationship can be set up as bidirectional trust (both trust each other) or as one-way trust (only one of them trust the other).
- 1.Enumerate the trusting relationships
- 2.Check if any security principal (user/group/computer) has access to resources of the other domain, maybe by ACE entries or by being in groups of the other domain. Look for relationships across domains (the trust was created for this probably).
- 1.kerberoast in this case could be another option.
- 3.Compromise the accounts which can pivot through domains.
There are three main ways that security principals (users/groups/computer) from one domain can have access into resources in another foreign/trusting domain:
- They can be added to local groups on individual machines, i.e. the local “Administrators” group on a server.
- They can be added to groups in the foreign domain. There are some caveats depending on trust type and group scope, described shortly.
- They can be added as principals in an access control list, most interesting for us as principals in ACEs in a DACL. For more background on ACLs/DACLs/ACEs, check out the “An ACE Up The Sleeve” whitepaper.
Get-DomainTrust
SourceName : sub.domain.local --> current domain
TargetName : domain.local --> foreign domain
TrustType : WINDOWS_ACTIVE_DIRECTORY
TrustAttributes : WITHIN_FOREST --> WITHIN_FOREST: Both in the same forest
TrustDirection : Bidirectional --> Trust direction (2ways in this case)
WhenCreated : 2/19/2021 1:28:00 PM
WhenChanged : 2/19/2021 1:28:00 PM
There are 2 trusted keys, one for Child --> Parent and another one for Parent --> Child.
You can the one used by the current domain them with:
Invoke-Mimikatz -Command '"lsadump::trust /patch"' -ComputerName dc.my.domain.local
Invoke-Mimikatz -Command '"lsadump::dcsync /user:dcorp\mcorp$"'
Escalate as Enterprise admin to the child/parent domain abusing the trust with SID-History injection:
The Configuration NC is the primary repository for configuration information for a forest and is replicated to every DC in the forest. Additionally, every writable DC (not read-only DCs) in the forest holds a writable copy of the Configuration NC. Exploiting this require running as SYSTEM on a (child) DC.
It is possible to compromise the root domain in various ways covered below.
Link GPO to root DC site
The Sites container in Configuration NC contains all sites of the domain-joined computers in the AD forest. It is possible to link GPOs to sites when running as SYSTEM on any DC in the forest, including the site(s) of the forest root DCs, and thereby compromise these.
Compromise any gMSA in the forest
The attack depends on privileged gMSAs in the targeted domain.
The KDS Root key, which is used to calculate the password of gMSAs in the forest, is stored in the Configuration NC. When running as SYSTEM on any DC in the forest, one can read out the KDS Root key and calculate the password of any gMSA in the forest.
Schema change attack
The attack requires the attacker to wait for new privileged AD objects to be created.
When running as SYSTEM on any DC in the forest, one can grant any user full control over all classes in the AD Schema. That control can be abused to create an ACE in the default security descriptor of any AD object that grants full control to a compromised principal. All new instances of the modified AD object types will have this ACE.
From DA to EA with ADCS ESC5
The ADCS ESC5 (Vulnerable PKI Object Access Control) attacks abuse control over PKI objects to create a vulnerable certificate template that can be abused to authenticate as any user in the forest. Since all the PKI objects are stored in the Configuration NC, one can execute ESC5 if they have compromised any writable (child) DC in the forest.
In case the AD forest does not have ADCS, the attacker can create the necessary components as described here: Escalating from child domain’s admins to enterprise admins in 5 minutes by abusing AD CS, a follow up.
Get-DomainTrust
SourceName : a.domain.local --> Current domain
TargetName : domain.external --> Destination domain
TrustType : WINDOWS-ACTIVE_DIRECTORY
TrustAttributes :
TrustDirection : Inbound --> Inboud trust
WhenCreated : 2/19/2021 10:50:56 PM
WhenChanged : 2/19/2021 10:50:56 PM
In this scenario your domain is trusted by an external one giving you undetermined permissions over it. You will need to find which principals of your domain have which access over the external domain and then try to exploit it:
Get-DomainTrust -Domain current.local
SourceName : current.local --> Current domain
TargetName : external.local --> Destination domain
TrustType : WINDOWS_ACTIVE_DIRECTORY
TrustAttributes : FOREST_TRANSITIVE
TrustDirection : Outbound --> Outbound trust
WhenCreated : 2/19/2021 10:15:24 PM
WhenChanged : 2/19/2021 10:15:24 PM
In this scenario your domain is trusting some privileges to principal from a different domains.
However, when a domain is trusted by the trusting domain, the trusted domain creates a user with a predictable name that uses as password the trusted password. Which means that it's possible to access a user from the trusting domain to get inside the trusted one to enumerate it and try to escalate more privileges:
Another way to compromise the trusted domain is to find a SQL trusted link created in the opposite direction of the domain trust (which isn't very common).
Another way to compromise the trusted domain is to wait in a machine where a user from the trusted domain can access to login via RDP. Then, the attacker could inject code in the RDP session process and access the origin domain of the victim from there.
Moreover, if the victim mounted his hard drive, from the RDP session process the attacker could store backdoors in the startup folder of the hard drive. This technique is called RDPInception.
SID Filtering:
- Avoid attacks which abuse SID history attribute across forest trust.
- Enabled by default on all inter-forest trusts. Intra-forest trusts are assumed secured by default (MS considers forest and not the domain to be a security boundary).
- But, since SID filtering has potential to break applications and user access, it is often disabled.
- Selective Authentication
- In an inter-forest trust, if Selective Authentication is configured, users between the trusts will not be automatically authenticated. Individual access to domains and servers in the trusting domain/forest should be given.
- Does not prevent writeable Configration NC exploitation and trust account attack.
Learn more about how to protect credentials here.
Please, find some migrations against each technique in the description of the technique.
- Not allow Domain Admins to login on any other hosts apart from Domain Controllers
- Never run a service with DA privileges
- If you need domain admin privileges, limit the time:
Add-ADGroupMember -Identity ‘Domain Admins’ -Members newDA -MemberTimeToLive (New-TimeSpan -Minutes 20)