krbroast

Documentation

Overview

Package krbroast assembles the hashcat crack line for the two dominant offline Kerberos credential attacks, from a captured KDC response:

• AS-REP roast (hashcat -m 18200): an AS-REP for a user with "do not require Kerberos preauth" set leaks the enc-part encrypted with the user's password-derived key. Line: $krb5asrep$23$user@REALM:checksum$edata
• Kerberoast (hashcat -m 13100): a TGS-REP's service ticket enc-part is encrypted with the service account's password-derived key. Line: $krb5tgs$23$*user$REALM$spn*$checksum$edata

kerberos_decode surfaces the pieces (the AS-REP/TGS-REP enc-part, the service ticket's enc-part + SPN); this closes the capture→crackable-hash gap by emitting the ready-to-crack line, exactly as netntlm_hashcat does for NTLM. The RC4 (etype 23) cipher is checksum(16) ‖ edata; that split is what hashcat expects. Pure offline transform; no network or device.

Wrap-vs-native judgement

Native. It reuses the in-tree internal/kerberos AS-REP/TGS-REP + Ticket decoder and does a length split + string format. There is nothing to wrap.

Verifiable / no confidently-wrong output

The line FORMAT is the canonical hashcat / impacket one; the cipher split is anchored to hand-built, spec-conformant AS-REP and TGS-REP DERs with known enc-parts (the EncryptedData parse itself is the same one verified against an impacket-built Ticket). Both encryption families are handled, matching impacket's GetUserSPNs / GetNPUsers exactly:

• RC4 (etype 23): cipher = checksum(16) ‖ edata. Kerberoast -m 13100, AS-REP roast -m 18200.
• AES (etype 17/18): cipher = edata ‖ checksum(12) (the checksum is the LAST 12 bytes). Kerberoast -m 19600 (AES128) / -m 19700 (AES256); the SPN is `*`-wrapped alone and ':' → '~'. AES AS-REP roast has no standard hashcat mode and is flagged for John the Ripper.

A non-AS-REP/TGS-REP message, or any other etype, errors rather than emitting a mis-split line.

Index

• type Result
  • func RoastLine(messageHex string) (*Result, error)

Types

type Result

type Result struct {
	Attack      string `json:"attack"`       // "AS-REP roast" / "Kerberoast"
	HashcatMode int    `json:"hashcat_mode"` // 18200 / 13100
	Principal   string `json:"principal,omitempty"`
	SPN         string `json:"spn,omitempty"`
	Realm       string `json:"realm,omitempty"`
	Line        string `json:"crack_line"`
	Note        string `json:"note,omitempty"`
}

Result is the assembled crack line.

func RoastLine

func RoastLine(messageHex string) (*Result, error)

RoastLine decodes an AS-REP / TGS-REP (hex) and emits the hashcat crack line.