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package packets
import (
"errors"
"fmt"
"strconv"
"time"
"encoding/asn1"
"encoding/hex"
)
const (
Krb5AsRequestType = 10
Krb5Krb5PrincipalNameType = 1
Krb5CryptDesCbcMd4 = 2
Krb5CryptDescCbcMd5 = 3
Krb5CryptRc4Hmac = 23
)
var (
ErrNoCrypt = errors.New("No crypt alg found")
ErrReqData = errors.New("Failed to extract pnData from as-req")
ErrNoCipher = errors.New("No encryption type or cipher found")
Krb5AsReqParam = "application,explicit,tag:10"
)
type Krb5PrincipalName struct {
NameType int `asn1:"explicit,tag:0"`
NameString []string `asn1:"general,explicit,tag:1"`
}
type Krb5EncryptedData struct {
Etype int `asn1:"explicit,tag:0"`
Kvno int `asn1:"optional,explicit,tag:1"`
Cipher []byte `asn1:"explicit,tag:2"`
}
type Krb5Ticket struct {
TktVno int `asn1:"explicit,tag:0"`
Realm string `asn1:"general,explicit,tag:1"`
Sname Krb5PrincipalName `asn1:"explicit,tag:2"`
EncPart Krb5EncryptedData `asn1:"explicit,tag:3"`
}
type Krb5Address struct {
AddrType int `asn1:"explicit,tag:0"`
Krb5Address []byte `asn1:"explicit,tag:1"`
}
type Krb5PnData struct {
Krb5PnDataType int `asn1:"explicit,tag:1"`
Krb5PnDataValue []byte `asn1:"explicit,tag:2"`
}
type Krb5ReqBody struct {
KDCOptions asn1.BitString `asn1:"explicit,tag:0"`
Cname Krb5PrincipalName `asn1:"optional,explicit,tag:1"`
Realm string `asn1:"general,explicit,tag:2"`
Sname Krb5PrincipalName `asn1:"optional,explicit,tag:3"`
From time.Time `asn1:"generalized,optional,explicit,tag:4"`
Till time.Time `asn1:"generalized,optional,explicit,tag:5"`
Rtime time.Time `asn1:"generalized,optional,explicit,tag:6"`
Nonce int `asn1:"explicit,tag:7"`
Etype []int `asn1:"explicit,tag:8"`
Krb5Addresses []Krb5Address `asn1:"optional,explicit,tag:9"`
EncAuthData Krb5EncryptedData `asn1:"optional,explicit,tag:10"`
AdditionalKrb5Tickets []Krb5Ticket `asn1:"optional,explicit,tag:11"`
}
type Krb5Request struct {
Pvno int `asn1:"explicit,tag:1"`
MsgType int `asn1:"explicit,tag:2"`
Krb5PnData []Krb5PnData `asn1:"optional,explicit,tag:3"`
ReqBody Krb5ReqBody `asn1:"explicit,tag:4"`
}
func (kdc Krb5Request) String() (string, error) {
var eType, cipher string
if kdc.ReqBody.Cname.NameType != Krb5Krb5PrincipalNameType {
return "", ErrNoCrypt
}
realm := kdc.ReqBody.Realm
crypt := kdc.ReqBody.Cname.NameString
for _, pn := range kdc.Krb5PnData {
if pn.Krb5PnDataType == 2 {
enc, err := pn.getParsedValue()
if err != nil {
return "", ErrReqData
}
eType = strconv.Itoa(enc.Etype)
cipher = hex.EncodeToString(enc.Cipher)
}
}
if eType == "" || cipher == "" {
return "", ErrNoCipher
}
return fmt.Sprintf("$krb5$%s$%s$%s$nodata$%s", eType, crypt[0], realm, cipher), nil
}
func (pd Krb5PnData) getParsedValue() (Krb5EncryptedData, error) {
var encData Krb5EncryptedData
_, err := asn1.Unmarshal(pd.Krb5PnDataValue, &encData)
if err != nil {
return Krb5EncryptedData{}, ErrReqData
}
return encData, nil
}
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