1 /*

     2  * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package sun.security.ssl.krb5;

    27 

    28 import java.io.*;

    29 import java.security.*;

    30 import java.util.Arrays;

    31 

    32 import javax.net.ssl.*;

    33 

    34 import sun.security.krb5.EncryptionKey;

    35 import sun.security.krb5.EncryptedData;

    36 import sun.security.krb5.KrbException;

    37 import sun.security.krb5.internal.crypto.KeyUsage;

    38 

    39 import sun.security.ssl.Debug;

    40 import sun.security.ssl.HandshakeInStream;

    41 import sun.security.ssl.HandshakeMessage;

    42 import sun.security.ssl.ProtocolVersion;

    43 

    44 /**

    45  * This is the Kerberos premaster secret in the Kerberos client key

    46  * exchange message (CLIENT --> SERVER); it holds the

    47  * Kerberos-encrypted pre-master secret. The secret is encrypted using the

    48  * Kerberos session key.  The padding and size of the resulting message

    49  * depends on the session key type, but the pre-master secret is

    50  * always exactly 48 bytes.

    51  *

    52  */

    53 final class KerberosPreMasterSecret {

    54 

    55     private ProtocolVersion protocolVersion; // preMaster [0,1]

    56     private byte preMaster[];           // 48 bytes

    57     private byte encrypted[];

    58 

    59     /**

    60      * Constructor used by client to generate premaster secret.

    61      *

    62      * Client randomly creates a pre-master secret and encrypts it

    63      * using the Kerberos session key; only the server can decrypt

    64      * it, using the session key available in the service ticket.

    65      *

    66      * @param protocolVersion used to set preMaster[0,1]

    67      * @param generator random number generator for generating premaster secret

    68      * @param sessionKey Kerberos session key for encrypting premaster secret

    69      */

    70     KerberosPreMasterSecret(ProtocolVersion protocolVersion,

    71         SecureRandom generator, EncryptionKey sessionKey) throws IOException {

    72 

    73         if (sessionKey.getEType() ==

    74             EncryptedData.ETYPE_DES3_CBC_HMAC_SHA1_KD) {

    75             throw new IOException(

    76                "session keys with des3-cbc-hmac-sha1-kd encryption type " +

    77                "are not supported for TLS Kerberos cipher suites");

    78         }

    79 

    80         this.protocolVersion = protocolVersion;

    81         preMaster = generatePreMaster(generator, protocolVersion);

    82 

    83         // Encrypt premaster secret

    84         try {

    85             EncryptedData eData = new EncryptedData(sessionKey, preMaster,

    86                 KeyUsage.KU_UNKNOWN);

    87             encrypted = eData.getBytes();  // not ASN.1 encoded.

    88 

    89         } catch (KrbException e) {

    90             throw (SSLKeyException)new SSLKeyException

    91                 ("Kerberos premaster secret error").initCause(e);

    92         }

    93     }

    94 

    95     /*

    96      * Constructor used by server to decrypt encrypted premaster secret.

    97      * The protocol version in preMaster[0,1] must match either currentVersion

    98      * or clientVersion, otherwise, the premaster secret is set to

    99      * a random one to foil possible attack.

   100      *

   101      * @param currentVersion version of protocol being used

   102      * @param clientVersion version requested by client

   103      * @param generator random number generator used to generate

   104      *        bogus premaster secret if premaster secret verification fails

   105      * @param input input stream from which to read the encrypted

   106      *        premaster secret

   107      * @param sessionKey Kerberos session key to be used for decryption

   108      */

   109     KerberosPreMasterSecret(ProtocolVersion currentVersion,

   110         ProtocolVersion clientVersion,

   111         SecureRandom generator, HandshakeInStream input,

   112         EncryptionKey sessionKey) throws IOException {

   113 

   114          // Extract encrypted premaster secret from message

   115          encrypted = input.getBytes16();

   116 

   117          if (HandshakeMessage.debug != null && Debug.isOn("handshake")) {

   118             if (encrypted != null) {

   119                 Debug.println(System.out,

   120                      "encrypted premaster secret", encrypted);

   121             }

   122          }

   123 

   124         if (sessionKey.getEType() ==

   125             EncryptedData.ETYPE_DES3_CBC_HMAC_SHA1_KD) {

   126             throw new IOException(

   127                "session keys with des3-cbc-hmac-sha1-kd encryption type " +

   128                "are not supported for TLS Kerberos cipher suites");

   129         }

   130 

   131         // Decrypt premaster secret

   132         try {

   133             EncryptedData data = new EncryptedData(sessionKey.getEType(),

   134                         null /* optional kvno */, encrypted);

   135 

   136             byte[] temp = data.decrypt(sessionKey, KeyUsage.KU_UNKNOWN);

   137             if (HandshakeMessage.debug != null && Debug.isOn("handshake")) {

   138                  if (encrypted != null) {

   139                      Debug.println(System.out,

   140                          "decrypted premaster secret", temp);

   141                  }

   142             }

   143 

   144             // Remove padding bytes after decryption. Only DES and DES3 have

   145             // paddings and we don't support DES3 in TLS (see above)

   146 

   147             if (temp.length == 52 &&

   148                     data.getEType() == EncryptedData.ETYPE_DES_CBC_CRC) {

   149                 // For des-cbc-crc, 4 paddings. Value can be 0x04 or 0x00.

   150                 if (paddingByteIs(temp, 52, (byte)4) ||

   151                         paddingByteIs(temp, 52, (byte)0)) {

   152                     temp = Arrays.copyOf(temp, 48);

   153                 }

   154             } else if (temp.length == 56 &&

   155                     data.getEType() == EncryptedData.ETYPE_DES_CBC_MD5) {

   156                 // For des-cbc-md5, 8 paddings with 0x08, or no padding

   157                 if (paddingByteIs(temp, 56, (byte)8)) {

   158                     temp = Arrays.copyOf(temp, 48);

   159                 }

   160             }

   161 

   162             preMaster = temp;

   163 

   164             protocolVersion = ProtocolVersion.valueOf(preMaster[0],

   165                  preMaster[1]);

   166             if (HandshakeMessage.debug != null && Debug.isOn("handshake")) {

   167                  System.out.println("Kerberos PreMasterSecret version: "

   168                         + protocolVersion);

   169             }

   170         } catch (Exception e) {

   171             // catch exception & process below

   172             preMaster = null;

   173             protocolVersion = currentVersion;

   174         }

   175 

   176         // check if the premaster secret version is ok

   177         // the specification says that it must be the maximum version supported

   178         // by the client from its ClientHello message. However, many

   179         // old implementations send the negotiated version, so accept both

   180         // for SSL v3.0 and TLS v1.0.

   181         // NOTE that we may be comparing two unsupported version numbers in

   182         // the second case, which is why we cannot use object references

   183         // equality in this special case

   184         boolean versionMismatch = (protocolVersion.v != clientVersion.v);

   185 

   186         /*

   187          * we never checked the client_version in server side

   188          * for TLS v1.0 and SSL v3.0. For compatibility, we

   189          * maintain this behavior.

   190          */

   191         if (versionMismatch && (clientVersion.v <= 0x0301)) {

   192             versionMismatch = (protocolVersion.v != currentVersion.v);

   193         }

   194 

   195         /*

   196          * Bogus decrypted ClientKeyExchange? If so, conjure a

   197          * a random preMaster secret that will fail later during

   198          * Finished message processing. This is a countermeasure against

   199          * the "interactive RSA PKCS#1 encryption envelop attack" reported

   200          * in June 1998. Preserving the executation path will

   201          * mitigate timing attacks and force consistent error handling

   202          * that will prevent an attacking client from differentiating

   203          * different kinds of decrypted ClientKeyExchange bogosities.

   204          */

   205          if ((preMaster == null) || (preMaster.length != 48)

   206                 || versionMismatch) {

   207             if (HandshakeMessage.debug != null && Debug.isOn("handshake")) {

   208                 System.out.println("Kerberos PreMasterSecret error, "

   209                                    + "generating random secret");

   210                 if (preMaster != null) {

   211                     Debug.println(System.out, "Invalid secret", preMaster);

   212                 }

   213             }

   214 

   215             /*

   216              * Randomize the preMaster secret with the

   217              * ClientHello.client_version, as will produce invalid master

   218              * secret to prevent the attacks.

   219              */

   220             preMaster = generatePreMaster(generator, clientVersion);

   221             protocolVersion = clientVersion;

   222         }

   223     }

   224 

   225     /**

   226      * Checks if all paddings of data are b

   227      * @param data the block with padding

   228      * @param len length of data, >= 48

   229      * @param b expected padding byte

   230      */

   231     private static boolean paddingByteIs(byte[] data, int len, byte b) {

   232         for (int i=48; i<len; i++) {

   233             if (data[i] != b) return false;

   234         }

   235         return true;

   236     }

   237 

   238     /*

   239      * Used by server to generate premaster secret in case of

   240      * problem decoding ticket.

   241      *

   242      * @param protocolVersion used for preMaster[0,1]

   243      * @param generator random number generator to use for generating secret.

   244      */

   245     KerberosPreMasterSecret(ProtocolVersion protocolVersion,

   246         SecureRandom generator) {

   247 

   248         this.protocolVersion = protocolVersion;

   249         preMaster = generatePreMaster(generator, protocolVersion);

   250     }

   251 

   252     private static byte[] generatePreMaster(SecureRandom rand,

   253         ProtocolVersion ver) {

   254 

   255         byte[] pm = new byte[48];

   256         rand.nextBytes(pm);

   257         pm[0] = ver.major;

   258         pm[1] = ver.minor;

   259 

   260         return pm;

   261     }

   262 

   263     // Clone not needed; internal use only

   264     byte[] getUnencrypted() {

   265         return preMaster;

   266     }

   267 

   268     // Clone not needed; internal use only

   269     byte[] getEncrypted() {

   270         return encrypted;

   271     }

   272 }