Java tutorial
/* * Copyright (c) 1997, 2017, 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 * or visit www.oracle.com if you need additional information or have any * questions. */ package java.security; import java.io.*; import java.security.spec.AlgorithmParameterSpec; import java.security.spec.InvalidParameterSpecException; import java.util.Objects; /** * This class is used as an opaque representation of cryptographic parameters. * * <p>An {@code AlgorithmParameters} object for managing the parameters * for a particular algorithm can be obtained by * calling one of the {@code getInstance} factory methods * (static methods that return instances of a given class). * * <p>Once an {@code AlgorithmParameters} object is obtained, it must be * initialized via a call to {@code init}, using an appropriate parameter * specification or parameter encoding. * * <p>A transparent parameter specification is obtained from an * {@code AlgorithmParameters} object via a call to * {@code getParameterSpec}, and a byte encoding of the parameters is * obtained via a call to {@code getEncoded}. * * <p> Every implementation of the Java platform is required to support the * following standard {@code AlgorithmParameters} algorithms: * <ul> * <li>{@code AES}</li> * <li>{@code DES}</li> * <li>{@code DESede}</li> * <li>{@code DiffieHellman}</li> * <li>{@code DSA}</li> * </ul> * These algorithms are described in the <a href= * "{@docRoot}/../specs/security/standard-names.html#algorithmparameters-algorithms"> * AlgorithmParameters 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 Jan Luehe * * * @see java.security.spec.AlgorithmParameterSpec * @see java.security.spec.DSAParameterSpec * @see KeyPairGenerator * * @since 1.2 */ public class AlgorithmParameters { // The provider private Provider provider; // The provider implementation (delegate) private AlgorithmParametersSpi paramSpi; // The algorithm private String algorithm; // Has this object been initialized? private boolean initialized = false; /** * Creates an AlgorithmParameters object. * * @param paramSpi the delegate * @param provider the provider * @param algorithm the algorithm */ protected AlgorithmParameters(AlgorithmParametersSpi paramSpi, Provider provider, String algorithm) { this.paramSpi = paramSpi; this.provider = provider; this.algorithm = algorithm; } /** * Returns the name of the algorithm associated with this parameter object. * * @return the algorithm name. */ public final String getAlgorithm() { return this.algorithm; } /** * Returns a parameter object for the specified algorithm. * * <p> This method traverses the list of registered security Providers, * starting with the most preferred Provider. * A new AlgorithmParameters object encapsulating the * AlgorithmParametersSpi 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. * * <p> The returned parameter object must be initialized via a call to * {@code init}, using an appropriate parameter specification or * parameter encoding. * * @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 name of the algorithm requested. * See the AlgorithmParameters section in the <a href= * "{@docRoot}/../specs/security/standard-names.html#algorithmparameters-algorithms"> * Java Security Standard Algorithm Names Specification</a> * for information about standard algorithm names. * * @return the new parameter object * * @throws NoSuchAlgorithmException if no {@code Provider} supports an * {@code AlgorithmParametersSpi} implementation for the * specified algorithm * * @throws NullPointerException if {@code algorithm} is {@code null} * * @see Provider */ public static AlgorithmParameters getInstance(String algorithm) throws NoSuchAlgorithmException { Objects.requireNonNull(algorithm, "null algorithm name"); try { Object[] objs = Security.getImpl(algorithm, "AlgorithmParameters", (String) null); return new AlgorithmParameters((AlgorithmParametersSpi) objs[0], (Provider) objs[1], algorithm); } catch (NoSuchProviderException e) { throw new NoSuchAlgorithmException(algorithm + " not found"); } } /** * Returns a parameter object for the specified algorithm. * * <p> A new AlgorithmParameters object encapsulating the * AlgorithmParametersSpi 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. * * <p>The returned parameter object must be initialized via a call to * {@code init}, using an appropriate parameter specification or * parameter encoding. * * @param algorithm the name of the algorithm requested. * See the AlgorithmParameters section in the <a href= * "{@docRoot}/../specs/security/standard-names.html#algorithmparameters-algorithms"> * Java Security Standard Algorithm Names Specification</a> * for information about standard algorithm names. * * @param provider the name of the provider. * * @return the new parameter object * * @throws IllegalArgumentException if the provider name is {@code null} * or empty * * @throws NoSuchAlgorithmException if an {@code AlgorithmParametersSpi} * 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 AlgorithmParameters getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException { Objects.requireNonNull(algorithm, "null algorithm name"); if (provider == null || provider.isEmpty()) throw new IllegalArgumentException("missing provider"); Object[] objs = Security.getImpl(algorithm, "AlgorithmParameters", provider); return new AlgorithmParameters((AlgorithmParametersSpi) objs[0], (Provider) objs[1], algorithm); } /** * Returns a parameter object for the specified algorithm. * * <p> A new AlgorithmParameters object encapsulating the * AlgorithmParametersSpi implementation from the specified Provider * object is returned. Note that the specified Provider object * does not have to be registered in the provider list. * * <p>The returned parameter object must be initialized via a call to * {@code init}, using an appropriate parameter specification or * parameter encoding. * * @param algorithm the name of the algorithm requested. * See the AlgorithmParameters section in the <a href= * "{@docRoot}/../specs/security/standard-names.html#algorithmparameters-algorithms"> * Java Security Standard Algorithm Names Specification</a> * for information about standard algorithm names. * * @param provider the name of the provider. * * @return the new parameter object * * @throws IllegalArgumentException if the provider is {@code null} * * @throws NoSuchAlgorithmException if an * {@code AlgorithmParameterGeneratorSpi} * 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 AlgorithmParameters getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException { Objects.requireNonNull(algorithm, "null algorithm name"); if (provider == null) throw new IllegalArgumentException("missing provider"); Object[] objs = Security.getImpl(algorithm, "AlgorithmParameters", provider); return new AlgorithmParameters((AlgorithmParametersSpi) objs[0], (Provider) objs[1], algorithm); } /** * Returns the provider of this parameter object. * * @return the provider of this parameter object */ public final Provider getProvider() { return this.provider; } /** * Initializes this parameter object using the parameters * specified in {@code paramSpec}. * * @param paramSpec the parameter specification. * * @exception InvalidParameterSpecException if the given parameter * specification is inappropriate for the initialization of this parameter * object, or if this parameter object has already been initialized. */ public final void init(AlgorithmParameterSpec paramSpec) throws InvalidParameterSpecException { if (this.initialized) throw new InvalidParameterSpecException("already initialized"); paramSpi.engineInit(paramSpec); this.initialized = true; } /** * Imports the specified parameters and decodes them according to the * primary decoding format for parameters. The primary decoding * format for parameters is ASN.1, if an ASN.1 specification for this type * of parameters exists. * * @param params the encoded parameters. * * @exception IOException on decoding errors, or if this parameter object * has already been initialized. */ public final void init(byte[] params) throws IOException { if (this.initialized) throw new IOException("already initialized"); paramSpi.engineInit(params); this.initialized = true; } /** * Imports the parameters from {@code params} and decodes them * according to the specified decoding scheme. * If {@code format} is null, the * primary decoding format for parameters is used. The primary decoding * format is ASN.1, if an ASN.1 specification for these parameters * exists. * * @param params the encoded parameters. * * @param format the name of the decoding scheme. * * @exception IOException on decoding errors, or if this parameter object * has already been initialized. */ public final void init(byte[] params, String format) throws IOException { if (this.initialized) throw new IOException("already initialized"); paramSpi.engineInit(params, format); this.initialized = true; } /** * Returns a (transparent) specification of this parameter object. * {@code paramSpec} identifies the specification class in which * the parameters should be returned. It could, for example, be * {@code DSAParameterSpec.class}, to indicate that the * parameters should be returned in an instance of the * {@code DSAParameterSpec} class. * * @param <T> the type of the parameter specification to be returrned * @param paramSpec the specification class in which * the parameters should be returned. * * @return the parameter specification. * * @exception InvalidParameterSpecException if the requested parameter * specification is inappropriate for this parameter object, or if this * parameter object has not been initialized. */ public final <T extends AlgorithmParameterSpec> T getParameterSpec(Class<T> paramSpec) throws InvalidParameterSpecException { if (this.initialized == false) { throw new InvalidParameterSpecException("not initialized"); } return paramSpi.engineGetParameterSpec(paramSpec); } /** * Returns the parameters in their primary encoding format. * The primary encoding format for parameters is ASN.1, if an ASN.1 * specification for this type of parameters exists. * * @return the parameters encoded using their primary encoding format. * * @exception IOException on encoding errors, or if this parameter object * has not been initialized. */ public final byte[] getEncoded() throws IOException { if (this.initialized == false) { throw new IOException("not initialized"); } return paramSpi.engineGetEncoded(); } /** * Returns the parameters encoded in the specified scheme. * If {@code format} is null, the * primary encoding format for parameters is used. The primary encoding * format is ASN.1, if an ASN.1 specification for these parameters * exists. * * @param format the name of the encoding format. * * @return the parameters encoded using the specified encoding scheme. * * @exception IOException on encoding errors, or if this parameter object * has not been initialized. */ public final byte[] getEncoded(String format) throws IOException { if (this.initialized == false) { throw new IOException("not initialized"); } return paramSpi.engineGetEncoded(format); } /** * Returns a formatted string describing the parameters. * * @return a formatted string describing the parameters, or null if this * parameter object has not been initialized. */ public final String toString() { if (this.initialized == false) { return null; } return paramSpi.engineToString(); } }