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add method GetServiceTicket to the kerberos module #4422

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merged 3 commits into from
Jan 12, 2024
Merged

add method GetServiceTicket to the kerberos module #4422

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cacfccc
add method GetServiceTicket to the kerberos module
5amu Nov 26, 2023
b129ccc
add target username to service ticket
5amu Nov 27, 2023
62ee28a
destroy kerberos client when function returns
5amu Dec 22, 2023
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48 changes: 48 additions & 0 deletions pkg/js/libs/kerberos/kerberos.go
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Original file line number Diff line number Diff line change
Expand Up @@ -97,6 +97,7 @@ func (c *KerberosClient) EnumerateUser(domain, controller string, username strin
return resp, err
}
cl := kclient.NewWithPassword(username, opts.realm, "foobar", opts.config, kclient.DisablePAFXFAST(true))
defer cl.Destroy()

req, err := messages.NewASReqForTGT(cl.Credentials.Domain(), cl.Config, cl.Credentials.CName())
if err != nil {
Expand Down Expand Up @@ -143,3 +144,50 @@ func asRepToHashcat(asrep messages.ASRep) (string, error) {
hex.EncodeToString(asrep.EncPart.Cipher[:16]),
hex.EncodeToString(asrep.EncPart.Cipher[16:])), nil
}

type TGS struct {
Ticket messages.Ticket
Hash string
}

func (c *KerberosClient) GetServiceTicket(domain, controller string, username, password string, target, spn string) (TGS, error) {
var tgs TGS

if !protocolstate.IsHostAllowed(domain) {
// host is not valid according to network policy
return tgs, protocolstate.ErrHostDenied.Msgf(domain)
}

opts, err := newKerbrosEnumUserOpts(domain, controller)
if err != nil {
return tgs, err
}
cl := kclient.NewWithPassword(username, opts.realm, password, opts.config, kclient.DisablePAFXFAST(true))
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I notice kclient is never destroyed, is this intentional?

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@5amu 5amu Dec 21, 2023 •
edited
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It is intentional, I assumed there was a reason, as the EnumerateUser function does not destroy the client.

nuclei/pkg/js/libs/kerberos/kerberos.go

Lines 86 to 136 in 984dfaf

func (c *KerberosClient) EnumerateUser(domain, controller string, username string) (EnumerateUserResponse, error) {
resp := EnumerateUserResponse{}
if !protocolstate.IsHostAllowed(domain) {
// host is not valid according to network policy
return resp, protocolstate.ErrHostDenied.Msgf(domain)
}
opts, err := newKerbrosEnumUserOpts(domain, controller)
if err != nil {
return resp, err
}
cl := kclient.NewWithPassword(username, opts.realm, "foobar", opts.config, kclient.DisablePAFXFAST(true))
req, err := messages.NewASReqForTGT(cl.Credentials.Domain(), cl.Config, cl.Credentials.CName())
if err != nil {
return resp, err
}
b, err := req.Marshal()
if err != nil {
return resp, err
}
rb, err := cl.SendToKDC(b, opts.realm)
if err == nil {
var ASRep messages.ASRep
err = ASRep.Unmarshal(rb)
if err != nil {
// something went wrong, it's not a valid response
return resp, err
}
hashcatString, _ := asRepToHashcat(ASRep)
resp.Valid = true
resp.ASREPHash = hashcatString
return resp, nil
}
e, ok := err.(messages.KRBError)
if !ok {
return resp, nil
}
switch e.ErrorCode {
case errorcode.KDC_ERR_C_PRINCIPAL_UNKNOWN:
return resp, nil
case errorcode.KDC_ERR_PREAUTH_REQUIRED:
resp.Valid = true
return resp, nil
default:
return resp, err
}
}

Should I add the relevant change? If so, should I add the Destroy() to EnumerateUser too or that's a different PR?

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Yeah, I think it would be best practice to do that. I'm sure the resources will get cleaned up eventually but it would be best not to leave them dangling.

defer cl.Destroy()

ticket, _, err := cl.GetServiceTicket(spn)
if err != nil {
return tgs, err
}

hashcat, err := tgsToHashcat(ticket, target)
if err != nil {
return tgs, err
}

return TGS{
Ticket: ticket,
Hash: hashcat,
}, nil
}

func tgsToHashcat(tgs messages.Ticket, username string) (string, error) {
return fmt.Sprintf("$krb5tgs$%d$*%s$%s$%s*$%s$%s",
tgs.EncPart.EType,
username,
tgs.Realm,
strings.Join(tgs.SName.NameString[:], "/"),
hex.EncodeToString(tgs.EncPart.Cipher[:16]),
hex.EncodeToString(tgs.EncPart.Cipher[16:]),
), nil
}
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