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| 1 | +package sarama |
| 2 | + |
| 3 | +import ( |
| 4 | + "encoding/binary" |
| 5 | + "encoding/hex" |
| 6 | + "fmt" |
| 7 | + "github.com/jcmturner/gofork/encoding/asn1" |
| 8 | + "gopkg.in/jcmturner/gokrb5.v7/asn1tools" |
| 9 | + krbclient "gopkg.in/jcmturner/gokrb5.v7/client" |
| 10 | + krbconfig "gopkg.in/jcmturner/gokrb5.v7/config" |
| 11 | + "gopkg.in/jcmturner/gokrb5.v7/gssapi" |
| 12 | + "gopkg.in/jcmturner/gokrb5.v7/iana/chksumtype" |
| 13 | + "gopkg.in/jcmturner/gokrb5.v7/iana/keyusage" |
| 14 | + "gopkg.in/jcmturner/gokrb5.v7/keytab" |
| 15 | + "gopkg.in/jcmturner/gokrb5.v7/messages" |
| 16 | + "gopkg.in/jcmturner/gokrb5.v7/types" |
| 17 | + "io" |
| 18 | + "strings" |
| 19 | +) |
| 20 | + |
| 21 | +const ( |
| 22 | + TOK_ID_KRB_AP_REQ = "0100" |
| 23 | + GSS_API_GENERIC_TAG = 0x60 |
| 24 | +) |
| 25 | + |
| 26 | +type GSSAPIConfig struct { |
| 27 | + KeyTabPath string |
| 28 | + KerberosConfigPath string |
| 29 | + ServiceName string |
| 30 | + Username string |
| 31 | + Realm string |
| 32 | +} |
| 33 | + |
| 34 | +type GSSAPIKerberosAuth struct { |
| 35 | + config *GSSAPIConfig |
| 36 | + client *krbclient.Client |
| 37 | + ticket messages.Ticket |
| 38 | + encryptionKey types.EncryptionKey |
| 39 | +} |
| 40 | + |
| 41 | +/* |
| 42 | +* |
| 43 | +* Appends length in big endian before payload, and send it to kafka |
| 44 | +* |
| 45 | + */ |
| 46 | + |
| 47 | +func (krbAuth *GSSAPIKerberosAuth) writePackage(broker *Broker, payload []byte) error { |
| 48 | + length := len(payload) |
| 49 | + finalPackage := make([]byte, length+4) //4 byte length header + payload |
| 50 | + copy(finalPackage[4:], payload) |
| 51 | + binary.BigEndian.PutUint32(finalPackage, uint32(length)) |
| 52 | + bytes, err := broker.conn.Write(finalPackage) |
| 53 | + broker.updateOutgoingCommunicationMetrics(bytes) |
| 54 | + if err != nil { |
| 55 | + return err |
| 56 | + } |
| 57 | + return nil |
| 58 | +} |
| 59 | + |
| 60 | +/* |
| 61 | +* |
| 62 | +* Read length (4 bytes) and then read the payload |
| 63 | +* |
| 64 | + */ |
| 65 | + |
| 66 | +func (krbAuth *GSSAPIKerberosAuth) readPackage(broker *Broker) ([]byte, error) { |
| 67 | + lengthInBytes := make([]byte, 4) |
| 68 | + _, err := io.ReadFull(broker.conn, lengthInBytes) |
| 69 | + if err != nil { |
| 70 | + return nil, err |
| 71 | + } |
| 72 | + payloadLength := binary.BigEndian.Uint32(lengthInBytes) |
| 73 | + payloadBytes := make([]byte, payloadLength) // buffer for read.. |
| 74 | + _, err = io.ReadFull(broker.conn, payloadBytes) // read bytes |
| 75 | + if err != nil { |
| 76 | + return payloadBytes, err |
| 77 | + } |
| 78 | + return payloadBytes, nil |
| 79 | +} |
| 80 | + |
| 81 | +func (krbAuth *GSSAPIKerberosAuth) newAuthenticatorChecksum(flags []int) []byte { |
| 82 | + a := make([]byte, 24) |
| 83 | + binary.LittleEndian.PutUint32(a[:4], 16) |
| 84 | + for _, i := range flags { |
| 85 | + if i == gssapi.ContextFlagDeleg { |
| 86 | + x := make([]byte, 28-len(a)) |
| 87 | + a = append(a, x...) |
| 88 | + } |
| 89 | + f := binary.LittleEndian.Uint32(a[20:24]) |
| 90 | + f |= uint32(i) |
| 91 | + binary.LittleEndian.PutUint32(a[20:24], f) |
| 92 | + } |
| 93 | + return a |
| 94 | +} |
| 95 | + |
| 96 | +/* |
| 97 | +* |
| 98 | +* Construct Kerberos AP_REQ package, conforming to RFC-4120 |
| 99 | +* https://tools.ietf.org/html/rfc4120#page-84 |
| 100 | +* |
| 101 | + */ |
| 102 | +func (krbAuth *GSSAPIKerberosAuth) createKrb5Token(client *krbclient.Client, ticket messages.Ticket, sessionKey types.EncryptionKey) []byte { |
| 103 | + var GSSAPIFlags = []int{gssapi.ContextFlagInteg, gssapi.ContextFlagConf} |
| 104 | + auth, _ := types.NewAuthenticator(client.Credentials.Domain(), client.Credentials.CName()) |
| 105 | + auth.Cksum = types.Checksum{ |
| 106 | + CksumType: chksumtype.GSSAPI, |
| 107 | + Checksum: krbAuth.newAuthenticatorChecksum(GSSAPIFlags), |
| 108 | + } |
| 109 | + APReq, _ := messages.NewAPReq( |
| 110 | + ticket, |
| 111 | + sessionKey, |
| 112 | + auth, |
| 113 | + ) |
| 114 | + aprBytes, _ := hex.DecodeString(TOK_ID_KRB_AP_REQ) |
| 115 | + tb, _ := APReq.Marshal() |
| 116 | + aprBytes = append(aprBytes, tb...) |
| 117 | + return aprBytes |
| 118 | +} |
| 119 | + |
| 120 | +/* |
| 121 | +* |
| 122 | +* Append the GSS-API header to the payload, conforming to RFC-2743 |
| 123 | +* Section 3.1, Mechanism-Independent Token Format |
| 124 | +* |
| 125 | +* https://tools.ietf.org/html/rfc2743#page-81 |
| 126 | +* |
| 127 | +* GSSAPIHeader + <specific mechanism payload> |
| 128 | +* |
| 129 | + */ |
| 130 | +func (krbAuth *GSSAPIKerberosAuth) appendGSSAPIHeader(payload []byte) []byte { |
| 131 | + oidBytes, _ := asn1.Marshal(gssapi.OID(gssapi.OIDKRB5)) |
| 132 | + tkoLengthBytes := asn1tools.MarshalLengthBytes(len(oidBytes) + len(payload)) |
| 133 | + GSSHeader := append([]byte{GSS_API_GENERIC_TAG}, tkoLengthBytes...) |
| 134 | + GSSHeader = append(GSSHeader, oidBytes...) |
| 135 | + GSSPackage := append(GSSHeader, payload...) |
| 136 | + return GSSPackage |
| 137 | +} |
| 138 | + |
| 139 | +/* |
| 140 | +* |
| 141 | +* Create kerberos client used to obtain TGT and TGS tokens |
| 142 | +* used gokrb5 library, which is a pure go kerberos client with |
| 143 | +* some GSS-API capabilities, and SPNEGO support. Kafka does not use SPNEGO |
| 144 | +* it uses pure Kerberos 5 solution (RFC-4121 and RFC-4120). |
| 145 | +* |
| 146 | + */ |
| 147 | +func (krbAuth *GSSAPIKerberosAuth) createKerberosClient() error { |
| 148 | + kt, err := keytab.Load(krbAuth.config.KeyTabPath) |
| 149 | + if err != nil { |
| 150 | + return err |
| 151 | + } |
| 152 | + cfg, err := krbconfig.Load(krbAuth.config.KerberosConfigPath) |
| 153 | + if err != nil { |
| 154 | + return err |
| 155 | + } |
| 156 | + krbAuth.client = krbclient.NewClientWithKeytab(krbAuth.config.Username, krbAuth.config.Realm, kt, cfg) |
| 157 | + return nil |
| 158 | +} |
| 159 | + |
| 160 | +/* This does the handshake for authorization */ |
| 161 | +func (krbAuth *GSSAPIKerberosAuth) Authorize(broker *Broker) error { |
| 162 | + |
| 163 | + err := krbAuth.createKerberosClient() |
| 164 | + if err != nil { |
| 165 | + Logger.Printf("Kerberos client error: %s", err) |
| 166 | + } |
| 167 | + // Construct SPN using serviceName and host |
| 168 | + // SPN format: <SERVICE>/<FQDN> |
| 169 | + |
| 170 | + host := strings.SplitN(broker.addr, ":", 2)[0] // Strip port part |
| 171 | + spn := fmt.Sprintf("%s/%s", broker.conf.Net.SASL.GSSAPI.ServiceName, host) |
| 172 | + |
| 173 | + ticket, encryptionKey, err := krbAuth.client.GetServiceTicket(spn) |
| 174 | + if err != nil { |
| 175 | + Logger.Printf("Error getting Kerberos service ticket : %s", err) |
| 176 | + return err |
| 177 | + } |
| 178 | + |
| 179 | + krbAuth.ticket = ticket |
| 180 | + krbAuth.encryptionKey = encryptionKey |
| 181 | + |
| 182 | + aprBytes := krbAuth.createKrb5Token(krbAuth.client, krbAuth.ticket, krbAuth.encryptionKey) |
| 183 | + GSSPackage := krbAuth.appendGSSAPIHeader(aprBytes) |
| 184 | + err = krbAuth.writePackage(broker, GSSPackage) |
| 185 | + if err != nil { |
| 186 | + Logger.Printf("Error while performing GSS-API Kerberos Authentication: %s\n", err) |
| 187 | + return err |
| 188 | + } |
| 189 | + |
| 190 | + wrapBytes, err := krbAuth.readPackage(broker) |
| 191 | + if err != nil { |
| 192 | + Logger.Printf("Error while performing GSS-API Kerberos Authentication: %s\n", err) |
| 193 | + return err |
| 194 | + } |
| 195 | + |
| 196 | + wrapTokenReq := gssapi.WrapToken{} |
| 197 | + err = wrapTokenReq.Unmarshal(wrapBytes, true) |
| 198 | + if err != nil { |
| 199 | + Logger.Printf("Error while performing GSS-API Kerberos Authentication: %s\n", err) |
| 200 | + return err |
| 201 | + } |
| 202 | + |
| 203 | + // Validate response. |
| 204 | + isValid, err := wrapTokenReq.Verify(krbAuth.encryptionKey, keyusage.GSSAPI_ACCEPTOR_SEAL) |
| 205 | + if !isValid { |
| 206 | + Logger.Printf("Error while performing GSS-API-Kerberos Authentication: %s", err) |
| 207 | + return err |
| 208 | + } |
| 209 | + |
| 210 | + // Reply to server |
| 211 | + wrapTokenResponse, err := gssapi.NewInitiatorWrapToken(wrapTokenReq.Payload, krbAuth.encryptionKey) |
| 212 | + if err != nil { |
| 213 | + Logger.Printf("Error while performing GSS-API-Kerberos Authentication: %s", err) |
| 214 | + return err |
| 215 | + } |
| 216 | + wrapResponseBytes, err := wrapTokenResponse.Marshal() |
| 217 | + if err != nil { |
| 218 | + Logger.Printf("Error while performing GSS-API-Kerberos Authentication: %s", err) |
| 219 | + return err |
| 220 | + } |
| 221 | + |
| 222 | + err = krbAuth.writePackage(broker, wrapResponseBytes) |
| 223 | + if err != nil { |
| 224 | + Logger.Printf("Error while performing GSS-API Kerberos Authentication: %s\n", err) |
| 225 | + return err |
| 226 | + } |
| 227 | + // If we reach this, we were already authenticated to kafka broker using kerberos. |
| 228 | + return nil |
| 229 | +} |
| 230 | + |
| 231 | +func NewGSSAPIKerberosAuthenticator(config *GSSAPIConfig) *GSSAPIKerberosAuth { |
| 232 | + return &GSSAPIKerberosAuth{ |
| 233 | + config: config, |
| 234 | + } |
| 235 | +} |
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