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 * Copyright (c) 1996, 2019, Oracle and/or its affiliates. All rights reserved.

 * 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

 * published by the Free Software Foundation.  Oracle designates this

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

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

 *

 * 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.

 *

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

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 * questions.

 */

package java.security;

import java.security.spec.AlgorithmParameterSpec;

import java.util.*;

import java.util.concurrent.ConcurrentHashMap;

import java.io.*;

import java.security.cert.Certificate;

import java.security.cert.X509Certificate;

import java.nio.ByteBuffer;

import java.security.Provider.Service;

import javax.crypto.Cipher;

import javax.crypto.IllegalBlockSizeException;

import javax.crypto.BadPaddingException;

import javax.crypto.NoSuchPaddingException;

import jdk.internal.access.JavaSecuritySignatureAccess;

import jdk.internal.access.SharedSecrets;

import sun.security.util.Debug;

import sun.security.jca.*;

import sun.security.jca.GetInstance.Instance;

/**

 * The Signature class is used to provide applications the functionality

 * of a digital signature algorithm. Digital signatures are used for

 * authentication and integrity assurance of digital data.

 *

 * <p> The signature algorithm can be, among others, the NIST standard

 * DSA, using DSA and SHA-256. The DSA algorithm using the

 * SHA-256 message digest algorithm can be specified as {@code SHA256withDSA}.

 * In the case of RSA the signing algorithm could be specified as, for example,

 * {@code SHA256withRSA}.

 * The algorithm name must be specified, as there is no default.

 *

 * <p> A Signature object can be used to generate and verify digital

 * signatures.

 *

 * <p> There are three phases to the use of a Signature object for

 * either signing data or verifying a signature:<ol>

 *

 * <li>Initialization, with either

 *

 *     <ul>

 *

 *     <li>a public key, which initializes the signature for

 *     verification (see {@link #initVerify(PublicKey) initVerify}), or

 *

 *     <li>a private key (and optionally a Secure Random Number Generator),

 *     which initializes the signature for signing

 *     (see {@link #initSign(PrivateKey)}

 *     and {@link #initSign(PrivateKey, SecureRandom)}).

 *

 *     </ul>

 *

 * <li>Updating

 *

 * <p>Depending on the type of initialization, this will update the

 * bytes to be signed or verified. See the

 * {@link #update(byte) update} methods.

 *

 * <li>Signing or Verifying a signature on all updated bytes. See the

 * {@link #sign() sign} methods and the {@link #verify(byte[]) verify}

 * method.

 *

 * </ol>

 *

 * <p>Note that this class is abstract and extends from

 * {@code SignatureSpi} for historical reasons.

 * Application developers should only take notice of the methods defined in

 * this {@code Signature} class; all the methods in

 * the superclass are intended for cryptographic service providers who wish to

 * supply their own implementations of digital signature algorithms.

 *

 * <p> Every implementation of the Java platform is required to support the

 * following standard {@code Signature} algorithms:

 * <ul>

 * <li>{@code SHA1withDSA}</li>

 * <li>{@code SHA256withDSA}</li>

 * <li>{@code SHA1withRSA}</li>

 * <li>{@code SHA256withRSA}</li>

 * </ul>

 * These algorithms are described in the <a href=

 * "{@docRoot}/../specs/security/standard-names.html#signature-algorithms">

 * Signature section</a> of the

 * Java Security Standard Algorithm Names Specification.

 * Consult the release documentation for your implementation to see if any

 * other algorithms are supported.

 *

 * @author Benjamin Renaud

 * @since 1.1

 *

 */

public abstract class Signature extends SignatureSpi {

    static {

        SharedSecrets.setJavaSecuritySignatureAccess(

            new JavaSecuritySignatureAccess() {

                @Override

                public void initVerify(Signature s, PublicKey publicKey,

                        AlgorithmParameterSpec params)

                        throws InvalidKeyException,

                        InvalidAlgorithmParameterException {

                    s.initVerify(publicKey, params);

                }

                @Override

                public void initVerify(Signature s,

                        java.security.cert.Certificate certificate,

                        AlgorithmParameterSpec params)

                        throws InvalidKeyException,

                        InvalidAlgorithmParameterException {

                    s.initVerify(certificate, params);

                }

                @Override

                public void initSign(Signature s, PrivateKey privateKey,

                        AlgorithmParameterSpec params, SecureRandom random)

                        throws InvalidKeyException,

                        InvalidAlgorithmParameterException {

                    s.initSign(privateKey, params, random);

                }

        });

    }

    private static final Debug debug =

                        Debug.getInstance("jca", "Signature");

    private static final Debug pdebug =

                        Debug.getInstance("provider", "Provider");

    private static final boolean skipDebug =

        Debug.isOn("engine=") && !Debug.isOn("signature");

    /*

     * The algorithm for this signature object.

     * This value is used to map an OID to the particular algorithm.

     * The mapping is done in AlgorithmObject.algOID(String algorithm)

     */

    private String algorithm;

    // The provider

    Provider provider;

    /**

     * Possible {@link #state} value, signifying that

     * this signature object has not yet been initialized.

     */

    protected static final int UNINITIALIZED = 0;

    /**

     * Possible {@link #state} value, signifying that

     * this signature object has been initialized for signing.

     */

    protected static final int SIGN = 2;

    /**

     * Possible {@link #state} value, signifying that

     * this signature object has been initialized for verification.

     */

    protected static final int VERIFY = 3;

    /**

     * Current state of this signature object.

     */

    protected int state = UNINITIALIZED;

    /**

     * Creates a Signature object for the specified algorithm.

     *

     * @param algorithm the standard string name of the algorithm.

     * See the Signature section in the <a href=

     * "{@docRoot}/../specs/security/standard-names.html#signature-algorithms">

     * Java Security Standard Algorithm Names Specification</a>

     * for information about standard algorithm names.

     */

    protected Signature(String algorithm) {

        this.algorithm = algorithm;

    }

    // name of the special signature alg

    private static final String RSA_SIGNATURE = "NONEwithRSA";

    // name of the equivalent cipher alg

    private static final String RSA_CIPHER = "RSA/ECB/PKCS1Padding";

    // all the services we need to lookup for compatibility with Cipher

    private static final List<ServiceId> rsaIds = List.of(

        new ServiceId("Signature", "NONEwithRSA"),

        new ServiceId("Cipher", "RSA/ECB/PKCS1Padding"),

        new ServiceId("Cipher", "RSA/ECB"),

        new ServiceId("Cipher", "RSA//PKCS1Padding"),

        new ServiceId("Cipher", "RSA"));

    /**

     * Returns a Signature object that implements the specified signature

     * algorithm.

     *

     * <p> This method traverses the list of registered security Providers,

     * starting with the most preferred Provider.

     * A new Signature object encapsulating the

     * SignatureSpi implementation from the first

     * Provider that supports the specified algorithm is returned.

     *

     * <p> Note that the list of registered providers may be retrieved via

     * the {@link Security#getProviders() Security.getProviders()} method.

     *

     * @implNote

     * The JDK Reference Implementation additionally uses the

     * {@code jdk.security.provider.preferred}

     * {@link Security#getProperty(String) Security} property to determine

     * the preferred provider order for the specified algorithm. This

     * may be different than the order of providers returned by

     * {@link Security#getProviders() Security.getProviders()}.

     *

     * @param algorithm the standard name of the algorithm requested.

     * See the Signature section in the <a href=

     * "{@docRoot}/../specs/security/standard-names.html#signature-algorithms">

     * Java Security Standard Algorithm Names Specification</a>

     * for information about standard algorithm names.

     *

     * @return the new {@code Signature} object

     *

     * @throws NoSuchAlgorithmException if no {@code Provider} supports a

     *         {@code Signature} implementation for the

     *         specified algorithm

     *

     * @throws NullPointerException if {@code algorithm} is {@code null}

     *

     * @see Provider

     */

    public static Signature getInstance(String algorithm)

            throws NoSuchAlgorithmException {

        Objects.requireNonNull(algorithm, "null algorithm name");

        List<Service> list;

        if (algorithm.equalsIgnoreCase(RSA_SIGNATURE)) {

            list = GetInstance.getServices(rsaIds);

        } else {

            list = GetInstance.getServices("Signature", algorithm);

        }

        Iterator<Service> t = list.iterator();

        if (t.hasNext() == false) {

            throw new NoSuchAlgorithmException

                (algorithm + " Signature not available");

        }

        // try services until we find an Spi or a working Signature subclass

        NoSuchAlgorithmException failure;

        do {

            Service s = t.next();

            if (isSpi(s)) {

                return new Delegate(s, t, algorithm);

            } else {

                // must be a subclass of Signature, disable dynamic selection

                try {

                    Instance instance =

                        GetInstance.getInstance(s, SignatureSpi.class);

                    return getInstance(instance, algorithm);

                } catch (NoSuchAlgorithmException e) {

                    failure = e;

                }

            }

        } while (t.hasNext());

        throw failure;

    }

    private static Signature getInstance(Instance instance, String algorithm) {

        Signature sig;

        if (instance.impl instanceof Signature) {

            sig = (Signature)instance.impl;

            sig.algorithm = algorithm;

        } else {

            SignatureSpi spi = (SignatureSpi)instance.impl;

            sig = new Delegate(spi, algorithm);

        }

        sig.provider = instance.provider;

        return sig;

    }

    private static final Map<String,Boolean> signatureInfo;

    static {

        signatureInfo = new ConcurrentHashMap<>();

        Boolean TRUE = Boolean.TRUE;

        // pre-initialize with values for our SignatureSpi implementations

        signatureInfo.put("sun.security.provider.DSA$RawDSA", TRUE);

        signatureInfo.put("sun.security.provider.DSA$SHA1withDSA", TRUE);

        signatureInfo.put("sun.security.rsa.RSASignature$MD2withRSA", TRUE);

        signatureInfo.put("sun.security.rsa.RSASignature$MD5withRSA", TRUE);

        signatureInfo.put("sun.security.rsa.RSASignature$SHA1withRSA", TRUE);

        signatureInfo.put("sun.security.rsa.RSASignature$SHA256withRSA", TRUE);

        signatureInfo.put("sun.security.rsa.RSASignature$SHA384withRSA", TRUE);

        signatureInfo.put("sun.security.rsa.RSASignature$SHA512withRSA", TRUE);

        signatureInfo.put("sun.security.rsa.RSAPSSSignature", TRUE);

        signatureInfo.put("sun.security.pkcs11.P11Signature", TRUE);

    }

    private static boolean isSpi(Service s) {

        if (s.getType().equals("Cipher")) {

            // must be a CipherSpi, which we can wrap with the CipherAdapter

            return true;

        }

        String className = s.getClassName();

        Boolean result = signatureInfo.get(className);

        if (result == null) {

            try {

                Object instance = s.newInstance(null);

                // Signature extends SignatureSpi

                // so it is a "real" Spi if it is an

                // instance of SignatureSpi but not Signature

                boolean r = (instance instanceof SignatureSpi)

                                && (instance instanceof Signature == false);

                if ((debug != null) && (r == false)) {

                    debug.println("Not a SignatureSpi " + className);

                    debug.println("Delayed provider selection may not be "

                        + "available for algorithm " + s.getAlgorithm());

                }

                result = Boolean.valueOf(r);

                signatureInfo.put(className, result);

            } catch (Exception e) {

                // something is wrong, assume not an SPI

                return false;

            }

        }

        return result.booleanValue();

    }

    /**

     * Returns a Signature object that implements the specified signature

     * algorithm.

     *

     * <p> A new Signature object encapsulating the

     * SignatureSpi implementation from the specified provider

     * is returned.  The specified provider must be registered

     * in the security provider list.

     *

     * <p> Note that the list of registered providers may be retrieved via

     * the {@link Security#getProviders() Security.getProviders()} method.

     *

     * @param algorithm the name of the algorithm requested.

     * See the Signature section in the <a href=

     * "{@docRoot}/../specs/security/standard-names.html#signature-algorithms">

     * Java Security Standard Algorithm Names Specification</a>

     * for information about standard algorithm names.

     *

     * @param provider the name of the provider.

     *

     * @return the new {@code Signature} object

     *

     * @throws IllegalArgumentException if the provider name is {@code null}

     *         or empty

     *

     * @throws NoSuchAlgorithmException if a {@code SignatureSpi}

     *         implementation for the specified algorithm is not

     *         available from the specified provider

     *

     * @throws NoSuchProviderException if the specified provider is not

     *         registered in the security provider list

     *

     * @throws NullPointerException if {@code algorithm} is {@code null}

     *

     * @see Provider

     */

    public static Signature getInstance(String algorithm, String provider)

            throws NoSuchAlgorithmException, NoSuchProviderException {

        Objects.requireNonNull(algorithm, "null algorithm name");

        if (algorithm.equalsIgnoreCase(RSA_SIGNATURE)) {

            // exception compatibility with existing code

            if (provider == null || provider.isEmpty()) {

                throw new IllegalArgumentException("missing provider");

            }

            Provider p = Security.getProvider(provider);

            if (p == null) {

                throw new NoSuchProviderException

                    ("no such provider: " + provider);

            }

            return getInstanceRSA(p);

        }

        Instance instance = GetInstance.getInstance

                ("Signature", SignatureSpi.class, algorithm, provider);

        return getInstance(instance, algorithm);

    }

    /**

     * Returns a Signature object that implements the specified

     * signature algorithm.

     *

     * <p> A new Signature object encapsulating the

     * SignatureSpi implementation from the specified Provider

     * object is returned.  Note that the specified Provider object

     * does not have to be registered in the provider list.

     *

     * @param algorithm the name of the algorithm requested.

     * See the Signature section in the <a href=

     * "{@docRoot}/../specs/security/standard-names.html#signature-algorithms">

     * Java Security Standard Algorithm Names Specification</a>

     * for information about standard algorithm names.

     *

     * @param provider the provider.

     *

     * @return the new {@code Signature} object

     *

     * @throws IllegalArgumentException if the provider is {@code null}

     *

     * @throws NoSuchAlgorithmException if a {@code SignatureSpi}

     *         implementation for the specified algorithm is not available

     *         from the specified {@code Provider} object

     *

     * @throws NullPointerException if {@code algorithm} is {@code null}

     *

     * @see Provider

     *

     * @since 1.4

     */

    public static Signature getInstance(String algorithm, Provider provider)

            throws NoSuchAlgorithmException {

        Objects.requireNonNull(algorithm, "null algorithm name");

        if (algorithm.equalsIgnoreCase(RSA_SIGNATURE)) {

            // exception compatibility with existing code

            if (provider == null) {

                throw new IllegalArgumentException("missing provider");

            }

            return getInstanceRSA(provider);

        }

        Instance instance = GetInstance.getInstance

                ("Signature", SignatureSpi.class, algorithm, provider);

        return getInstance(instance, algorithm);

    }

    // return an implementation for NONEwithRSA, which is a special case

    // because of the Cipher.RSA/ECB/PKCS1Padding compatibility wrapper

    private static Signature getInstanceRSA(Provider p)

            throws NoSuchAlgorithmException {

        // try Signature first

        Service s = p.getService("Signature", RSA_SIGNATURE);

        if (s != null) {

            Instance instance = GetInstance.getInstance(s, SignatureSpi.class);

            return getInstance(instance, RSA_SIGNATURE);

        }

        // check Cipher

        try {

            Cipher c = Cipher.getInstance(RSA_CIPHER, p);

            return new Delegate(new CipherAdapter(c), RSA_SIGNATURE);

        } catch (GeneralSecurityException e) {

            // throw Signature style exception message to avoid confusion,

            // but append Cipher exception as cause

            throw new NoSuchAlgorithmException("no such algorithm: "

                + RSA_SIGNATURE + " for provider " + p.getName(), e);

        }

    }

    /**

     * Returns the provider of this signature object.

     *

     * @return the provider of this signature object

     */

    public final Provider getProvider() {

        chooseFirstProvider();

        return this.provider;

    }

    private String getProviderName() {

        return (provider == null)  ? "(no provider)" : provider.getName();

    }

    void chooseFirstProvider() {

        // empty, overridden in Delegate

    }

    /**

     * Initializes this object for verification. If this method is called

     * again with a different argument, it negates the effect

     * of this call.

     *

     * @param publicKey the public key of the identity whose signature is

     * going to be verified.

     *

     */

    public final void initVerify(PublicKey publicKey)

            throws InvalidKeyException {

        engineInitVerify(publicKey);

        state = VERIFY;

        if (!skipDebug && pdebug != null) {

            pdebug.println("Signature." + algorithm +

                " verification algorithm from: " + getProviderName());

        }

    }