blob: 5becccc4dde56b4ac1694000712c2e244033f918 [file] [log] [blame]
David K. Bainbridgebd6b2882021-08-26 13:31:02 +00001package client
2
3import (
4 "github.com/jcmturner/gokrb5/v8/crypto"
5 "github.com/jcmturner/gokrb5/v8/crypto/etype"
6 "github.com/jcmturner/gokrb5/v8/iana/errorcode"
7 "github.com/jcmturner/gokrb5/v8/iana/keyusage"
8 "github.com/jcmturner/gokrb5/v8/iana/patype"
9 "github.com/jcmturner/gokrb5/v8/krberror"
10 "github.com/jcmturner/gokrb5/v8/messages"
11 "github.com/jcmturner/gokrb5/v8/types"
12)
13
14// ASExchange performs an AS exchange for the client to retrieve a TGT.
15func (cl *Client) ASExchange(realm string, ASReq messages.ASReq, referral int) (messages.ASRep, error) {
16 if ok, err := cl.IsConfigured(); !ok {
17 return messages.ASRep{}, krberror.Errorf(err, krberror.ConfigError, "AS Exchange cannot be performed")
18 }
19
20 // Set PAData if required
21 err := setPAData(cl, nil, &ASReq)
22 if err != nil {
23 return messages.ASRep{}, krberror.Errorf(err, krberror.KRBMsgError, "AS Exchange Error: issue with setting PAData on AS_REQ")
24 }
25
26 b, err := ASReq.Marshal()
27 if err != nil {
28 return messages.ASRep{}, krberror.Errorf(err, krberror.EncodingError, "AS Exchange Error: failed marshaling AS_REQ")
29 }
30 var ASRep messages.ASRep
31
32 rb, err := cl.sendToKDC(b, realm)
33 if err != nil {
34 if e, ok := err.(messages.KRBError); ok {
35 switch e.ErrorCode {
36 case errorcode.KDC_ERR_PREAUTH_REQUIRED, errorcode.KDC_ERR_PREAUTH_FAILED:
37 // From now on assume this client will need to do this pre-auth and set the PAData
38 cl.settings.assumePreAuthentication = true
39 err = setPAData(cl, &e, &ASReq)
40 if err != nil {
41 return messages.ASRep{}, krberror.Errorf(err, krberror.KRBMsgError, "AS Exchange Error: failed setting AS_REQ PAData for pre-authentication required")
42 }
43 b, err := ASReq.Marshal()
44 if err != nil {
45 return messages.ASRep{}, krberror.Errorf(err, krberror.EncodingError, "AS Exchange Error: failed marshaling AS_REQ with PAData")
46 }
47 rb, err = cl.sendToKDC(b, realm)
48 if err != nil {
49 if _, ok := err.(messages.KRBError); ok {
50 return messages.ASRep{}, krberror.Errorf(err, krberror.KDCError, "AS Exchange Error: kerberos error response from KDC")
51 }
52 return messages.ASRep{}, krberror.Errorf(err, krberror.NetworkingError, "AS Exchange Error: failed sending AS_REQ to KDC")
53 }
54 case errorcode.KDC_ERR_WRONG_REALM:
55 // Client referral https://tools.ietf.org/html/rfc6806.html#section-7
56 if referral > 5 {
57 return messages.ASRep{}, krberror.Errorf(err, krberror.KRBMsgError, "maximum number of client referrals exceeded")
58 }
59 referral++
60 return cl.ASExchange(e.CRealm, ASReq, referral)
61 default:
62 return messages.ASRep{}, krberror.Errorf(err, krberror.KDCError, "AS Exchange Error: kerberos error response from KDC")
63 }
64 } else {
65 return messages.ASRep{}, krberror.Errorf(err, krberror.NetworkingError, "AS Exchange Error: failed sending AS_REQ to KDC")
66 }
67 }
68 err = ASRep.Unmarshal(rb)
69 if err != nil {
70 return messages.ASRep{}, krberror.Errorf(err, krberror.EncodingError, "AS Exchange Error: failed to process the AS_REP")
71 }
72 if ok, err := ASRep.Verify(cl.Config, cl.Credentials, ASReq); !ok {
73 return messages.ASRep{}, krberror.Errorf(err, krberror.KRBMsgError, "AS Exchange Error: AS_REP is not valid or client password/keytab incorrect")
74 }
75 return ASRep, nil
76}
77
78// setPAData adds pre-authentication data to the AS_REQ.
79func setPAData(cl *Client, krberr *messages.KRBError, ASReq *messages.ASReq) error {
80 if !cl.settings.DisablePAFXFAST() {
81 pa := types.PAData{PADataType: patype.PA_REQ_ENC_PA_REP}
82 ASReq.PAData = append(ASReq.PAData, pa)
83 }
84 if cl.settings.AssumePreAuthentication() {
85 // Identify the etype to use to encrypt the PA Data
86 var et etype.EType
87 var err error
88 var key types.EncryptionKey
89 var kvno int
90 if krberr == nil {
91 // This is not in response to an error from the KDC. It is preemptive or renewal
92 // There is no KRB Error that tells us the etype to use
93 etn := cl.settings.preAuthEType // Use the etype that may have previously been negotiated
94 if etn == 0 {
95 etn = int32(cl.Config.LibDefaults.PreferredPreauthTypes[0]) // Resort to config
96 }
97 et, err = crypto.GetEtype(etn)
98 if err != nil {
99 return krberror.Errorf(err, krberror.EncryptingError, "error getting etype for pre-auth encryption")
100 }
101 key, kvno, err = cl.Key(et, 0, nil)
102 if err != nil {
103 return krberror.Errorf(err, krberror.EncryptingError, "error getting key from credentials")
104 }
105 } else {
106 // Get the etype to use from the PA data in the KRBError e-data
107 et, err = preAuthEType(krberr)
108 if err != nil {
109 return krberror.Errorf(err, krberror.EncryptingError, "error getting etype for pre-auth encryption")
110 }
111 cl.settings.preAuthEType = et.GetETypeID() // Set the etype that has been defined for potential future use
112 key, kvno, err = cl.Key(et, 0, krberr)
113 if err != nil {
114 return krberror.Errorf(err, krberror.EncryptingError, "error getting key from credentials")
115 }
116 }
117 // Generate the PA data
118 paTSb, err := types.GetPAEncTSEncAsnMarshalled()
119 if err != nil {
120 return krberror.Errorf(err, krberror.KRBMsgError, "error creating PAEncTSEnc for Pre-Authentication")
121 }
122 paEncTS, err := crypto.GetEncryptedData(paTSb, key, keyusage.AS_REQ_PA_ENC_TIMESTAMP, kvno)
123 if err != nil {
124 return krberror.Errorf(err, krberror.EncryptingError, "error encrypting pre-authentication timestamp")
125 }
126 pb, err := paEncTS.Marshal()
127 if err != nil {
128 return krberror.Errorf(err, krberror.EncodingError, "error marshaling the PAEncTSEnc encrypted data")
129 }
130 pa := types.PAData{
131 PADataType: patype.PA_ENC_TIMESTAMP,
132 PADataValue: pb,
133 }
134 // Look for and delete any exiting patype.PA_ENC_TIMESTAMP
135 for i, pa := range ASReq.PAData {
136 if pa.PADataType == patype.PA_ENC_TIMESTAMP {
137 ASReq.PAData[i] = ASReq.PAData[len(ASReq.PAData)-1]
138 ASReq.PAData = ASReq.PAData[:len(ASReq.PAData)-1]
139 }
140 }
141 ASReq.PAData = append(ASReq.PAData, pa)
142 }
143 return nil
144}
145
146// preAuthEType establishes what encryption type to use for pre-authentication from the KRBError returned from the KDC.
147func preAuthEType(krberr *messages.KRBError) (etype etype.EType, err error) {
148 //RFC 4120 5.2.7.5 covers the preference order of ETYPE-INFO2 and ETYPE-INFO.
149 var etypeID int32
150 var pas types.PADataSequence
151 e := pas.Unmarshal(krberr.EData)
152 if e != nil {
153 err = krberror.Errorf(e, krberror.EncodingError, "error unmashalling KRBError data")
154 return
155 }
156Loop:
157 for _, pa := range pas {
158 switch pa.PADataType {
159 case patype.PA_ETYPE_INFO2:
160 info, e := pa.GetETypeInfo2()
161 if e != nil {
162 err = krberror.Errorf(e, krberror.EncodingError, "error unmashalling ETYPE-INFO2 data")
163 return
164 }
165 etypeID = info[0].EType
166 break Loop
167 case patype.PA_ETYPE_INFO:
168 info, e := pa.GetETypeInfo()
169 if e != nil {
170 err = krberror.Errorf(e, krberror.EncodingError, "error unmashalling ETYPE-INFO data")
171 return
172 }
173 etypeID = info[0].EType
174 }
175 }
176 etype, e = crypto.GetEtype(etypeID)
177 if e != nil {
178 err = krberror.Errorf(e, krberror.EncryptingError, "error creating etype")
179 return
180 }
181 return etype, nil
182}