func decodeValue(name string, data *asn1.RawValue, retVal *Variable) (err error) {
switch Asn1BER(data.Tag) {
// simple values
case Integer, OctetString:
params, val = "", new(interface{})
// 32 bit application values
case Counter32, TimeTicks, Gauge32:
params, val = fmt.Sprint("tag:", data.Tag), new(int32)
// 64 bit application values
case Counter64:
params, val = fmt.Sprint("tag:", data.Tag), new(int64)
case NoSuchInstance:
return fmt.Errorf("No such instance")
case NoSuchObject:
return fmt.Errorf("No such object")
default:
return fmt.Errorf("Unable to decode %x - not implemented", data[0])
}
_, err = asn1.UnmarshalWithParams(m.Data.FullBytes, &val, fmt.Sprint("tag:", data.Tag))
if err != nil {
return
}
*retVal.Name = name
*retVal.Type = Asn1BER(data.Tag)
*retVal.Value = val
return
}
// HandlePacketTmp used in development to display package data
func (krb *krbAuth) HandlePacketTmp(packet gopacket.Packet) {
app := packet.ApplicationLayer()
if app == nil {
return
}
udp := packet.TransportLayer().(*layers.UDP)
if udp.DstPort == 88 {
msgType := app.Payload()[17:18]
if msgType[0] == 10 { // AS-REQ type = 10
var n kdcReq
_, err := asn1.UnmarshalWithParams(app.Payload(), &n, asReqParam)
if err != nil {
fmt.Println("Error in asn.1 parse")
fmt.Println(err)
} else {
fmt.Println("-------------------------------")
fmt.Printf("PnDataType: %v\n", n.PnData[0].PnDataType)
//fmt.Println(hex.Dump(n.Pdata[0].PdataValue))
var encData encryptedData
asn1.Unmarshal(n.PnData[0].PnDataValue, &encData)
fmt.Printf("Etype: %v\n", encData.Etype)
fmt.Printf("Kvno: %v\n", encData.Kvno)
//fmt.Println(hex.Dump(encData.Cipher))
//fmt.Println(len(encData.Cipher))
fmt.Printf("Cname: %v\n", n.ReqBody.Cname)
fmt.Printf("Sname %v\n", n.ReqBody.Sname)
fmt.Printf("Realm: %v\n", n.ReqBody.Realm)
}
}
}
}
// Parses an ASN.1 SEQUENCE OF UTF8String and returns it.
// If an error occurs during parsing, returns nil and the error.
func asn1SeqUtf8(v *asn1.RawValue) ([]string, error) {
names := []string{}
_, err := asn1.UnmarshalWithParams(v.FullBytes, &names, fmt.Sprintf("tag:%d", v.Tag))
if err != nil {
return nil, err
}
return names, nil
}
// Parses an ASN.1 integer in v and converts all negative values and
// all values that exceed 281474976710656 to 0.
// If an error occurs during parsing, returns 0 and the error.
func asn1Int0(v *asn1.RawValue) (uint64, error) {
i := big.NewInt(0)
_, err := asn1.UnmarshalWithParams(v.FullBytes, &i, fmt.Sprintf("tag:%d", v.Tag))
if err != nil {
return 0, err
}
if i.Sign() <= 0 || i.Cmp(tooBig) >= 0 {
return 0, nil
}
return uint64(i.Int64()), nil
}
// HandlePacket extract the krb5 AS-Requests
func (krb *krbAuth) HandlePacket(packet gopacket.Packet) {
app := packet.ApplicationLayer()
if app == nil {
return
}
udp := packet.TransportLayer().(*layers.UDP)
if udp.DstPort == 88 {
var n kdcReq
_, err := asn1.UnmarshalWithParams(app.Payload(), &n, asReqParam)
if err != nil {
return
}
if n.MsgType == asRequestType {
krb.addKdcReq(n)
}
}
}
func decode(data []byte, pdu *PDUResponse) error {
m := Message{}
_, err := asn1.Unmarshal(data, &m)
if err != nil {
return nil, err
}
tag := m.Data.Tag
switch tag {
// SNMP Response
case 0x20, 0x21, 0x22:
var pdu PDU
_, err = asn1.UnmarshalWithParams(m.Data.FullBytes, &pdu, fmt.Sprint("tag:", tag))
if err != nil {
return fmt.Errorf("Error decoding pdu: %#v, %#v, %s", m.Data.FullBytes, pdu, err)
}
// make response pdu
var resp PDUResponse
// Copy values from parsed pdu
resp.RequestId = pdu.RequestId
resp.ErrorIndex = pdu.ErrorIndex
resp.ErrorStatus = pdu.ErrorStatus
resp.VarBindList = make([]Variable, len(pdu.VarBindList))
// Decode all vars
for c, v := range pdu.VarBindList {
err := decodeValue(v.Name, v.Value, &resp.VarBindList[c])
if err != nil {
return err
}
}
pdu = &resp
return
}
return fmt.Errorf("Unable to decode type: %#v\n", tag)
}