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pac_type.go
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pac_type.go
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package pac
import (
"encoding/binary"
"errors"
"fmt"
"gopkg.in/jcmturner/gokrb5.v5/crypto"
"gopkg.in/jcmturner/gokrb5.v5/iana/keyusage"
"gopkg.in/jcmturner/gokrb5.v5/ndr"
"gopkg.in/jcmturner/gokrb5.v5/types"
)
// PACType implements: https://msdn.microsoft.com/en-us/library/cc237950.aspx
type PACType struct {
CBuffers uint32
Version uint32
Buffers []InfoBuffer
Data []byte
KerbValidationInfo *KerbValidationInfo
CredentialsInfo *CredentialsInfo
ServerChecksum *SignatureData
KDCChecksum *SignatureData
ClientInfo *ClientInfo
S4UDelegationInfo *S4UDelegationInfo
UPNDNSInfo *UPNDNSInfo
ClientClaimsInfo *ClientClaimsInfo
DeviceInfo *DeviceInfo
DeviceClaimsInfo *DeviceClaimsInfo
ZeroSigData []byte
}
// Unmarshal bytes into the PACType struct
func (pac *PACType) Unmarshal(b []byte) error {
var p int
var e binary.ByteOrder = binary.LittleEndian
pac.Data = b
zb := make([]byte, len(b), len(b))
copy(zb, b)
pac.ZeroSigData = zb
pac.CBuffers = ndr.ReadUint32(&b, &p, &e)
pac.Version = ndr.ReadUint32(&b, &p, &e)
buf := make([]InfoBuffer, pac.CBuffers, pac.CBuffers)
for i := range buf {
buf[i] = ReadPACInfoBuffer(&b, &p, &e)
}
pac.Buffers = buf
return nil
}
// ProcessPACInfoBuffers processes the PAC Info Buffers.
// https://msdn.microsoft.com/en-us/library/cc237954.aspx
func (pac *PACType) ProcessPACInfoBuffers(key types.EncryptionKey) error {
for _, buf := range pac.Buffers {
p := make([]byte, buf.CBBufferSize, buf.CBBufferSize)
copy(p, pac.Data[int(buf.Offset):int(buf.Offset)+int(buf.CBBufferSize)])
switch int(buf.ULType) {
case ulTypeKerbValidationInfo:
if pac.KerbValidationInfo != nil {
//Must ignore subsequent buffers of this type
continue
}
var k KerbValidationInfo
err := k.Unmarshal(p)
if err != nil {
return fmt.Errorf("error processing KerbValidationInfo: %v", err)
}
pac.KerbValidationInfo = &k
case ulTypeCredentials:
if pac.CredentialsInfo != nil {
//Must ignore subsequent buffers of this type
continue
}
var k CredentialsInfo
err := k.Unmarshal(p, key)
if err != nil {
return fmt.Errorf("error processing CredentialsInfo: %v", err)
}
pac.CredentialsInfo = &k
case ulTypePACServerSignatureData:
if pac.ServerChecksum != nil {
//Must ignore subsequent buffers of this type
continue
}
var k SignatureData
zb, err := k.Unmarshal(p)
copy(pac.ZeroSigData[int(buf.Offset):int(buf.Offset)+int(buf.CBBufferSize)], zb)
if err != nil {
return fmt.Errorf("error processing ServerChecksum: %v", err)
}
pac.ServerChecksum = &k
case ulTypePACKDCSignatureData:
if pac.KDCChecksum != nil {
//Must ignore subsequent buffers of this type
continue
}
var k SignatureData
zb, err := k.Unmarshal(p)
copy(pac.ZeroSigData[int(buf.Offset):int(buf.Offset)+int(buf.CBBufferSize)], zb)
if err != nil {
return fmt.Errorf("error processing KDCChecksum: %v", err)
}
pac.KDCChecksum = &k
case ulTypePACClientInfo:
if pac.ClientInfo != nil {
//Must ignore subsequent buffers of this type
continue
}
var k ClientInfo
err := k.Unmarshal(p)
if err != nil {
return fmt.Errorf("error processing ClientInfo: %v", err)
}
pac.ClientInfo = &k
case ulTypeS4UDelegationInfo:
if pac.S4UDelegationInfo != nil {
//Must ignore subsequent buffers of this type
continue
}
var k S4UDelegationInfo
err := k.Unmarshal(p)
if err != nil {
return fmt.Errorf("error processing S4U_DelegationInfo: %v", err)
}
pac.S4UDelegationInfo = &k
case ulTypeUPNDNSInfo:
if pac.UPNDNSInfo != nil {
//Must ignore subsequent buffers of this type
continue
}
var k UPNDNSInfo
err := k.Unmarshal(p)
if err != nil {
return fmt.Errorf("error processing UPN_DNSInfo: %v", err)
}
pac.UPNDNSInfo = &k
case ulTypePACClientClaimsInfo:
if pac.ClientClaimsInfo != nil {
//Must ignore subsequent buffers of this type
continue
}
var k ClientClaimsInfo
err := k.Unmarshal(p)
if err != nil {
return fmt.Errorf("error processing ClientClaimsInfo: %v", err)
}
pac.ClientClaimsInfo = &k
case ulTypePACDeviceInfo:
if pac.DeviceInfo != nil {
//Must ignore subsequent buffers of this type
continue
}
var k DeviceInfo
err := k.Unmarshal(p)
if err != nil {
return fmt.Errorf("error processing DeviceInfo: %v", err)
}
pac.DeviceInfo = &k
case ulTypePACDeviceClaimsInfo:
if pac.DeviceClaimsInfo != nil {
//Must ignore subsequent buffers of this type
continue
}
var k DeviceClaimsInfo
err := k.Unmarshal(p)
if err != nil {
return fmt.Errorf("error processing DeviceClaimsInfo: %v", err)
}
pac.DeviceClaimsInfo = &k
}
}
if ok, err := pac.validate(key); !ok {
return err
}
return nil
}
func (pac *PACType) validate(key types.EncryptionKey) (bool, error) {
if pac.KerbValidationInfo == nil {
return false, errors.New("PAC Info Buffers does not contain a KerbValidationInfo")
}
if pac.ServerChecksum == nil {
return false, errors.New("PAC Info Buffers does not contain a ServerChecksum")
}
if pac.KDCChecksum == nil {
return false, errors.New("PAC Info Buffers does not contain a KDCChecksum")
}
if pac.ClientInfo == nil {
return false, errors.New("PAC Info Buffers does not contain a ClientInfo")
}
etype, err := crypto.GetChksumEtype(int32(pac.ServerChecksum.SignatureType))
if err != nil {
return false, err
}
if ok := etype.VerifyChecksum(key.KeyValue,
pac.ZeroSigData,
pac.ServerChecksum.Signature,
keyusage.KERB_NON_KERB_CKSUM_SALT); !ok {
return false, errors.New("PAC service checksum verification failed")
}
return true, nil
}