308 lines
14 KiB
Go
308 lines
14 KiB
Go
package messages
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// Reference: https://www.ietf.org/rfc/rfc4120.txt
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// Section: 5.4.2
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import (
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"fmt"
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"time"
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"github.com/jcmturner/gofork/encoding/asn1"
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"github.com/jcmturner/gokrb5/v8/config"
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"github.com/jcmturner/gokrb5/v8/credentials"
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"github.com/jcmturner/gokrb5/v8/crypto"
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"github.com/jcmturner/gokrb5/v8/iana/asnAppTag"
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"github.com/jcmturner/gokrb5/v8/iana/flags"
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"github.com/jcmturner/gokrb5/v8/iana/keyusage"
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"github.com/jcmturner/gokrb5/v8/iana/msgtype"
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"github.com/jcmturner/gokrb5/v8/iana/patype"
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"github.com/jcmturner/gokrb5/v8/krberror"
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"github.com/jcmturner/gokrb5/v8/types"
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)
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type marshalKDCRep struct {
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PVNO int `asn1:"explicit,tag:0"`
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MsgType int `asn1:"explicit,tag:1"`
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PAData types.PADataSequence `asn1:"explicit,optional,tag:2"`
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CRealm string `asn1:"generalstring,explicit,tag:3"`
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CName types.PrincipalName `asn1:"explicit,tag:4"`
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// Ticket needs to be a raw value as it is wrapped in an APPLICATION tag
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Ticket asn1.RawValue `asn1:"explicit,tag:5"`
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EncPart types.EncryptedData `asn1:"explicit,tag:6"`
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}
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// KDCRepFields represents the KRB_KDC_REP fields.
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type KDCRepFields struct {
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PVNO int
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MsgType int
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PAData []types.PAData
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CRealm string
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CName types.PrincipalName
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Ticket Ticket
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EncPart types.EncryptedData
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DecryptedEncPart EncKDCRepPart
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}
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// ASRep implements RFC 4120 KRB_AS_REP: https://tools.ietf.org/html/rfc4120#section-5.4.2.
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type ASRep struct {
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KDCRepFields
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}
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// TGSRep implements RFC 4120 KRB_TGS_REP: https://tools.ietf.org/html/rfc4120#section-5.4.2.
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type TGSRep struct {
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KDCRepFields
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}
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// EncKDCRepPart is the encrypted part of KRB_KDC_REP.
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type EncKDCRepPart struct {
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Key types.EncryptionKey `asn1:"explicit,tag:0"`
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LastReqs []LastReq `asn1:"explicit,tag:1"`
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Nonce int `asn1:"explicit,tag:2"`
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KeyExpiration time.Time `asn1:"generalized,explicit,optional,tag:3"`
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Flags asn1.BitString `asn1:"explicit,tag:4"`
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AuthTime time.Time `asn1:"generalized,explicit,tag:5"`
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StartTime time.Time `asn1:"generalized,explicit,optional,tag:6"`
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EndTime time.Time `asn1:"generalized,explicit,tag:7"`
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RenewTill time.Time `asn1:"generalized,explicit,optional,tag:8"`
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SRealm string `asn1:"generalstring,explicit,tag:9"`
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SName types.PrincipalName `asn1:"explicit,tag:10"`
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CAddr []types.HostAddress `asn1:"explicit,optional,tag:11"`
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EncPAData types.PADataSequence `asn1:"explicit,optional,tag:12"`
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}
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// LastReq part of KRB_KDC_REP.
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type LastReq struct {
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LRType int32 `asn1:"explicit,tag:0"`
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LRValue time.Time `asn1:"generalized,explicit,tag:1"`
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}
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// Unmarshal bytes b into the ASRep struct.
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func (k *ASRep) Unmarshal(b []byte) error {
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var m marshalKDCRep
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_, err := asn1.UnmarshalWithParams(b, &m, fmt.Sprintf("application,explicit,tag:%v", asnAppTag.ASREP))
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if err != nil {
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return processUnmarshalReplyError(b, err)
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}
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if m.MsgType != msgtype.KRB_AS_REP {
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return krberror.NewErrorf(krberror.KRBMsgError, "message ID does not indicate an AS_REP. Expected: %v; Actual: %v", msgtype.KRB_AS_REP, m.MsgType)
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}
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//Process the raw ticket within
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tkt, err := unmarshalTicket(m.Ticket.Bytes)
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if err != nil {
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return krberror.Errorf(err, krberror.EncodingError, "error unmarshaling Ticket within AS_REP")
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}
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k.KDCRepFields = KDCRepFields{
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PVNO: m.PVNO,
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MsgType: m.MsgType,
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PAData: m.PAData,
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CRealm: m.CRealm,
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CName: m.CName,
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Ticket: tkt,
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EncPart: m.EncPart,
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}
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return nil
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}
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// Unmarshal bytes b into the TGSRep struct.
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func (k *TGSRep) Unmarshal(b []byte) error {
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var m marshalKDCRep
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_, err := asn1.UnmarshalWithParams(b, &m, fmt.Sprintf("application,explicit,tag:%v", asnAppTag.TGSREP))
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if err != nil {
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return processUnmarshalReplyError(b, err)
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}
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if m.MsgType != msgtype.KRB_TGS_REP {
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return krberror.NewErrorf(krberror.KRBMsgError, "message ID does not indicate an TGS_REP. Expected: %v; Actual: %v", msgtype.KRB_TGS_REP, m.MsgType)
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}
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//Process the raw ticket within
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tkt, err := unmarshalTicket(m.Ticket.Bytes)
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if err != nil {
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return krberror.Errorf(err, krberror.EncodingError, "error unmarshaling Ticket within TGS_REP")
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}
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k.KDCRepFields = KDCRepFields{
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PVNO: m.PVNO,
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MsgType: m.MsgType,
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PAData: m.PAData,
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CRealm: m.CRealm,
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CName: m.CName,
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Ticket: tkt,
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EncPart: m.EncPart,
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}
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return nil
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}
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// Unmarshal bytes b into encrypted part of KRB_KDC_REP.
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func (e *EncKDCRepPart) Unmarshal(b []byte) error {
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_, err := asn1.UnmarshalWithParams(b, e, fmt.Sprintf("application,explicit,tag:%v", asnAppTag.EncASRepPart))
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if err != nil {
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// Try using tag 26
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// Ref: RFC 4120 - mentions that some implementations use application tag number 26 wether or not the reply is
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// a AS-REP or a TGS-REP.
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_, err = asn1.UnmarshalWithParams(b, e, fmt.Sprintf("application,explicit,tag:%v", asnAppTag.EncTGSRepPart))
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if err != nil {
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return krberror.Errorf(err, krberror.EncodingError, "error unmarshaling encrypted part within KDC_REP")
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}
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}
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return nil
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}
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// DecryptEncPart decrypts the encrypted part of an AS_REP.
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func (k *ASRep) DecryptEncPart(c *credentials.Credentials) (types.EncryptionKey, error) {
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var key types.EncryptionKey
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var err error
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if c.HasKeytab() {
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key, _, err = c.Keytab().GetEncryptionKey(k.CName, k.CRealm, k.EncPart.KVNO, k.EncPart.EType)
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if err != nil {
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return key, krberror.Errorf(err, krberror.DecryptingError, "error decrypting AS_REP encrypted part")
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}
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}
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if c.HasPassword() {
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key, _, err = crypto.GetKeyFromPassword(c.Password(), k.CName, k.CRealm, k.EncPart.EType, k.PAData)
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if err != nil {
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return key, krberror.Errorf(err, krberror.DecryptingError, "error decrypting AS_REP encrypted part")
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}
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}
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if !c.HasKeytab() && !c.HasPassword() {
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return key, krberror.NewErrorf(krberror.DecryptingError, "no secret available in credentials to perform decryption of AS_REP encrypted part")
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}
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b, err := crypto.DecryptEncPart(k.EncPart, key, keyusage.AS_REP_ENCPART)
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if err != nil {
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return key, krberror.Errorf(err, krberror.DecryptingError, "error decrypting AS_REP encrypted part")
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}
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var denc EncKDCRepPart
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err = denc.Unmarshal(b)
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if err != nil {
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return key, krberror.Errorf(err, krberror.EncodingError, "error unmarshaling decrypted encpart of AS_REP")
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}
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k.DecryptedEncPart = denc
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return key, nil
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}
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// Verify checks the validity of AS_REP message.
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func (k *ASRep) Verify(cfg *config.Config, creds *credentials.Credentials, asReq ASReq) (bool, error) {
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//Ref RFC 4120 Section 3.1.5
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if k.CName.NameType != asReq.ReqBody.CName.NameType || k.CName.NameString == nil {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "CName in response does not match what was requested. Requested: %+v; Reply: %+v", asReq.ReqBody.CName, k.CName)
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}
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for i := range k.CName.NameString {
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if k.CName.NameString[i] != asReq.ReqBody.CName.NameString[i] {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "CName in response does not match what was requested. Requested: %+v; Reply: %+v", asReq.ReqBody.CName, k.CName)
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}
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}
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if k.CRealm != asReq.ReqBody.Realm {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "CRealm in response does not match what was requested. Requested: %s; Reply: %s", asReq.ReqBody.Realm, k.CRealm)
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}
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key, err := k.DecryptEncPart(creds)
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if err != nil {
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return false, krberror.Errorf(err, krberror.DecryptingError, "error decrypting EncPart of AS_REP")
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}
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if k.DecryptedEncPart.Nonce != asReq.ReqBody.Nonce {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "possible replay attack, nonce in response does not match that in request")
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}
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if k.DecryptedEncPart.SName.NameType != asReq.ReqBody.SName.NameType || k.DecryptedEncPart.SName.NameString == nil {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "SName in response does not match what was requested. Requested: %v; Reply: %v", asReq.ReqBody.SName, k.DecryptedEncPart.SName)
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}
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for i := range k.CName.NameString {
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if k.DecryptedEncPart.SName.NameString[i] != asReq.ReqBody.SName.NameString[i] {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "SName in response does not match what was requested. Requested: %+v; Reply: %+v", asReq.ReqBody.SName, k.DecryptedEncPart.SName)
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}
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}
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if k.DecryptedEncPart.SRealm != asReq.ReqBody.Realm {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "SRealm in response does not match what was requested. Requested: %s; Reply: %s", asReq.ReqBody.Realm, k.DecryptedEncPart.SRealm)
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}
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if len(asReq.ReqBody.Addresses) > 0 {
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if !types.HostAddressesEqual(k.DecryptedEncPart.CAddr, asReq.ReqBody.Addresses) {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "addresses listed in the AS_REP does not match those listed in the AS_REQ")
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}
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}
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t := time.Now().UTC()
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if t.Sub(k.DecryptedEncPart.AuthTime) > cfg.LibDefaults.Clockskew || k.DecryptedEncPart.AuthTime.Sub(t) > cfg.LibDefaults.Clockskew {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "clock skew with KDC too large. Greater than %v seconds", cfg.LibDefaults.Clockskew.Seconds())
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}
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// RFC 6806 https://tools.ietf.org/html/rfc6806.html#section-11
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if asReq.PAData.Contains(patype.PA_REQ_ENC_PA_REP) && types.IsFlagSet(&k.DecryptedEncPart.Flags, flags.EncPARep) {
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if len(k.DecryptedEncPart.EncPAData) < 2 || !k.DecryptedEncPart.EncPAData.Contains(patype.PA_FX_FAST) {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "KDC did not respond appropriately to FAST negotiation")
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}
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for _, pa := range k.DecryptedEncPart.EncPAData {
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if pa.PADataType == patype.PA_REQ_ENC_PA_REP {
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var pafast types.PAReqEncPARep
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err := pafast.Unmarshal(pa.PADataValue)
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if err != nil {
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return false, krberror.Errorf(err, krberror.EncodingError, "KDC FAST negotiation response error, could not unmarshal PA_REQ_ENC_PA_REP")
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}
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etype, err := crypto.GetChksumEtype(pafast.ChksumType)
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if err != nil {
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return false, krberror.Errorf(err, krberror.ChksumError, "KDC FAST negotiation response error")
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}
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ab, _ := asReq.Marshal()
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if !etype.VerifyChecksum(key.KeyValue, ab, pafast.Chksum, keyusage.KEY_USAGE_AS_REQ) {
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return false, krberror.Errorf(err, krberror.ChksumError, "KDC FAST negotiation response checksum invalid")
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}
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}
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}
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}
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return true, nil
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}
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// DecryptEncPart decrypts the encrypted part of an TGS_REP.
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func (k *TGSRep) DecryptEncPart(key types.EncryptionKey) error {
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b, err := crypto.DecryptEncPart(k.EncPart, key, keyusage.TGS_REP_ENCPART_SESSION_KEY)
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if err != nil {
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return krberror.Errorf(err, krberror.DecryptingError, "error decrypting TGS_REP EncPart")
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}
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var denc EncKDCRepPart
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err = denc.Unmarshal(b)
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if err != nil {
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return krberror.Errorf(err, krberror.EncodingError, "error unmarshaling encrypted part")
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}
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k.DecryptedEncPart = denc
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return nil
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}
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// Verify checks the validity of the TGS_REP message.
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func (k *TGSRep) Verify(cfg *config.Config, tgsReq TGSReq) (bool, error) {
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if k.CName.NameType != tgsReq.ReqBody.CName.NameType || k.CName.NameString == nil {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "CName type in response does not match what was requested. Requested: %+v; Reply: %+v", tgsReq.ReqBody.CName, k.CName)
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}
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for i := range k.CName.NameString {
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if k.CName.NameString[i] != tgsReq.ReqBody.CName.NameString[i] {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "CName in response does not match what was requested. Requested: %+v; Reply: %+v", tgsReq.ReqBody.CName, k.CName)
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}
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}
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if k.Ticket.Realm != tgsReq.ReqBody.Realm {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "realm in response ticket does not match what was requested. Requested: %s; Reply: %s", tgsReq.ReqBody.Realm, k.Ticket.Realm)
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}
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if k.DecryptedEncPart.Nonce != tgsReq.ReqBody.Nonce {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "possible replay attack, nonce in response does not match that in request")
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}
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//if k.Ticket.SName.NameType != tgsReq.ReqBody.SName.NameType || k.Ticket.SName.NameString == nil {
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// return false, krberror.NewErrorf(krberror.KRBMsgError, "SName in response ticket does not match what was requested. Requested: %v; Reply: %v", tgsReq.ReqBody.SName, k.Ticket.SName)
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//}
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//for i := range k.Ticket.SName.NameString {
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// if k.Ticket.SName.NameString[i] != tgsReq.ReqBody.SName.NameString[i] {
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// return false, krberror.NewErrorf(krberror.KRBMsgError, "SName in response ticket does not match what was requested. Requested: %+v; Reply: %+v", tgsReq.ReqBody.SName, k.Ticket.SName)
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// }
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//}
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//if k.DecryptedEncPart.SName.NameType != tgsReq.ReqBody.SName.NameType || k.DecryptedEncPart.SName.NameString == nil {
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// return false, krberror.NewErrorf(krberror.KRBMsgError, "SName in response does not match what was requested. Requested: %v; Reply: %v", tgsReq.ReqBody.SName, k.DecryptedEncPart.SName)
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//}
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//for i := range k.DecryptedEncPart.SName.NameString {
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// if k.DecryptedEncPart.SName.NameString[i] != tgsReq.ReqBody.SName.NameString[i] {
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// return false, krberror.NewErrorf(krberror.KRBMsgError, "SName in response does not match what was requested. Requested: %+v; Reply: %+v", tgsReq.ReqBody.SName, k.DecryptedEncPart.SName)
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// }
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//}
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if k.DecryptedEncPart.SRealm != tgsReq.ReqBody.Realm {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "SRealm in response does not match what was requested. Requested: %s; Reply: %s", tgsReq.ReqBody.Realm, k.DecryptedEncPart.SRealm)
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}
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if len(k.DecryptedEncPart.CAddr) > 0 {
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if !types.HostAddressesEqual(k.DecryptedEncPart.CAddr, tgsReq.ReqBody.Addresses) {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "addresses listed in the TGS_REP does not match those listed in the TGS_REQ")
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}
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}
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if time.Since(k.DecryptedEncPart.StartTime) > cfg.LibDefaults.Clockskew || k.DecryptedEncPart.StartTime.Sub(time.Now().UTC()) > cfg.LibDefaults.Clockskew {
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if time.Since(k.DecryptedEncPart.AuthTime) > cfg.LibDefaults.Clockskew || k.DecryptedEncPart.AuthTime.Sub(time.Now().UTC()) > cfg.LibDefaults.Clockskew {
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return false, krberror.NewErrorf(krberror.KRBMsgError, "clock skew with KDC too large. Greater than %v seconds.", cfg.LibDefaults.Clockskew.Seconds())
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}
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}
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return true, nil
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}
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