/*

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

 *

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

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

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

 *

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

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

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

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

 * accompanied this code).

 *

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

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

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

 *

 */

package sun.security.ssl;

import java.io.*;

import java.security.*;

import java.security.interfaces.*;

import javax.crypto.*;

import javax.crypto.spec.*;

import javax.net.ssl.*;

import sun.security.internal.spec.TlsRsaPremasterSecretParameterSpec;

/**

 * This is the client key exchange message (CLIENT --> SERVER) used with

 * all RSA key exchanges; it holds the RSA-encrypted pre-master secret.

 *

 * The message is encrypted using PKCS #1 block type 02 encryption with the

 * server's public key.  The padding and resulting message size is a function

 * of this server's public key modulus size, but the pre-master secret is

 * always exactly 48 bytes.

 *

 */

final class RSAClientKeyExchange extends HandshakeMessage {

    /**

     * The TLS spec says that the version in the RSA premaster secret must

     * be the maximum version supported by the client (i.e. the version it

     * requested in its client hello version). However, we (and other

     * implementations) used to send the active negotiated version. The

     * system property below allows to toggle the behavior.

     *

     * Default is "false" (old behavior) for compatibility reasons. This

     * will be changed in the future.

     */

    private final static String PROP_NAME =

                                "com.sun.net.ssl.rsaPreMasterSecretFix";

    private final static boolean rsaPreMasterSecretFix =

                                Debug.getBooleanProperty(PROP_NAME, false);

    int messageType() {

        return ht_client_key_exchange;

    }

    /*

     * The following field values were encrypted with the server's public

     * key (or temp key from server key exchange msg) and are presented

     * here in DECRYPTED form.

     */

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

    SecretKey preMaster;

    private byte[] encrypted;           // same size as public modulus

    /*

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

     * using the server's RSA public key; only the server can decrypt

     * it, using its RSA private key.  Result is the same size as the

     * server's public key, and uses PKCS #1 block format 02.

     */

    RSAClientKeyExchange(ProtocolVersion protocolVersion, ProtocolVersion maxVersion,

            SecureRandom generator, PublicKey publicKey) throws IOException {

        if (publicKey.getAlgorithm().equals("RSA") == false) {

            throw new SSLKeyException("Public key not of type RSA");

        }

        this.protocolVersion = protocolVersion;

        int major, minor;

        if (rsaPreMasterSecretFix) {

            major = maxVersion.major;

            minor = maxVersion.minor;

        } else {

            major = protocolVersion.major;

            minor = protocolVersion.minor;

        }

        try {

            KeyGenerator kg = JsseJce.getKeyGenerator("SunTlsRsaPremasterSecret");

            kg.init(new TlsRsaPremasterSecretParameterSpec(major, minor));

            preMaster = kg.generateKey();

            Cipher cipher = JsseJce.getCipher(JsseJce.CIPHER_RSA_PKCS1);

            cipher.init(Cipher.WRAP_MODE, publicKey, generator);

            encrypted = cipher.wrap(preMaster);

        } catch (GeneralSecurityException e) {

            throw (SSLKeyException)new SSLKeyException

                                ("RSA premaster secret error").initCause(e);

        }

    }

    /*

     * Server gets the PKCS #1 (block format 02) data, decrypts

     * it with its private key.

     */

    RSAClientKeyExchange(ProtocolVersion currentVersion, HandshakeInStream input,

            int messageSize, PrivateKey privateKey) throws IOException {

        if (privateKey.getAlgorithm().equals("RSA") == false) {

            throw new SSLKeyException("Private key not of type RSA");

        }

        this.protocolVersion = currentVersion;

        if (currentVersion.v >= ProtocolVersion.TLS10.v) {

            encrypted = input.getBytes16();

        } else {

            encrypted = new byte [messageSize];

            if (input.read(encrypted) != messageSize) {

                throw new SSLProtocolException

                        ("SSL: read PreMasterSecret: short read");

            }

        }

        try {

            Cipher cipher = JsseJce.getCipher(JsseJce.CIPHER_RSA_PKCS1);

            cipher.init(Cipher.UNWRAP_MODE, privateKey);

            preMaster = (SecretKey)cipher.unwrap(encrypted,

                                "TlsRsaPremasterSecret", Cipher.SECRET_KEY);

        } catch (Exception e) {

            /*

             * Bogus decrypted ClientKeyExchange? If so, conjure a

             * a random preMaster secret that will fail later during

             * Finished message processing. This is a countermeasure against

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

             * in June 1998. Preserving the executation path will

             * mitigate timing attacks and force consistent error handling

             * that will prevent an attacking client from differentiating

             * different kinds of decrypted ClientKeyExchange bogosities.

             */

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

                System.out.println("Error decrypting premaster secret:");

                e.printStackTrace(System.out);

                System.out.println("Generating random secret");

            }

            preMaster = generateDummySecret(currentVersion);

        }

    }

    // generate a premaster secret with the specified version number

    static SecretKey generateDummySecret(ProtocolVersion version) {

        try {

            KeyGenerator kg =

                    JsseJce.getKeyGenerator("SunTlsRsaPremasterSecret");

            kg.init(new TlsRsaPremasterSecretParameterSpec

                    (version.major, version.minor));

            return kg.generateKey();

        } catch (GeneralSecurityException e) {

            throw new RuntimeException("Could not generate dummy secret", e);

        }

    }

    int messageLength() {

        if (protocolVersion.v >= ProtocolVersion.TLS10.v) {

            return encrypted.length + 2;

        } else {

            return encrypted.length;

        }

    }

    void send(HandshakeOutStream s) throws IOException {

        if (protocolVersion.v >= ProtocolVersion.TLS10.v) {

            s.putBytes16(encrypted);

        } else {

            s.write(encrypted);

        }

    }

    void print(PrintStream s) throws IOException {

        s.println("*** ClientKeyExchange, RSA PreMasterSecret, " + protocolVersion);

    }

}