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package java.security.spec;

import java.util.Objects;

/**
 * This class specifies a parameter spec for the RSASSA-PSS signature scheme,
 * as defined in the
 * <a href="https://tools.ietf.org/rfc/rfc8017.txt">PKCS#1 v2.2</a> standard.
 *
 * <p>Its ASN.1 definition in the PKCS #1 standard is described below:
 * <pre>
 * RSASSA-PSS-params ::= SEQUENCE {
 *   hashAlgorithm      [0] HashAlgorithm      DEFAULT sha1,
 *   maskGenAlgorithm   [1] MaskGenAlgorithm   DEFAULT mgf1SHA1,
 *   saltLength         [2] INTEGER            DEFAULT 20,
 *   trailerField       [3] TrailerField       DEFAULT trailerFieldBC(1)
 * }
 * </pre>
 * where
 * <pre>
 * HashAlgorithm ::= AlgorithmIdentifier {
 *   {OAEP-PSSDigestAlgorithms}
 * }
 * MaskGenAlgorithm ::= AlgorithmIdentifier { {PKCS1MGFAlgorithms} }
 * TrailerField ::= INTEGER { trailerFieldBC(1) }
 *
 * OAEP-PSSDigestAlgorithms    ALGORITHM-IDENTIFIER ::= {
 *   { OID id-sha1       PARAMETERS NULL }|
 *   { OID id-sha224     PARAMETERS NULL }|
 *   { OID id-sha256     PARAMETERS NULL }|
 *   { OID id-sha384     PARAMETERS NULL }|
 *   { OID id-sha512     PARAMETERS NULL }|
 *   { OID id-sha512-224 PARAMETERS NULL }|
 *   { OID id-sha512-256 PARAMETERS NULL },
 *   ...  -- Allows for future expansion --
 * }
 * PKCS1MGFAlgorithms    ALGORITHM-IDENTIFIER ::= {
 *   { OID id-mgf1 PARAMETERS HashAlgorithm },
 *   ...  -- Allows for future expansion --
 * }
 * </pre>
 *
 * @spec https://www.rfc-editor.org/info/rfc8017
 *      RFC 8017: PKCS #1: RSA Cryptography Specifications Version 2.2
 * @see MGF1ParameterSpec
 * @see AlgorithmParameterSpec
 * @see java.security.Signature
 *
 * @author Valerie Peng
 *
 *
 * @since 1.4
 */

public class PSSParameterSpec implements AlgorithmParameterSpec {

    private final String mdName;

    private final String mgfName;

    private final AlgorithmParameterSpec mgfSpec;

    private final int saltLen;

    private final int trailerField;

    /**
     * The {@code TrailerFieldBC} constant as defined in the PKCS #1 standard.
     *
     * @since 11
     */
    public static final int TRAILER_FIELD_BC = 1;

    /**
     * The PSS parameter set with all default values.
     * @spec https://www.rfc-editor.org/info/rfc8017
     *      RFC 8017: PKCS #1: RSA Cryptography Specifications Version 2.2
     * @deprecated This field uses the default values defined in the PKCS #1
     *         standard. Some of these defaults are no longer recommended due
     *         to advances in cryptanalysis -- see the
     *         <a href="https://tools.ietf.org/rfc/rfc8017.txt">PKCS#1 v2.2</a>
     *         standard for more details. Thus, it is recommended to create
     *         a new {@code PSSParameterSpec} with the desired parameter values
     *         using the
     *         {@link #PSSParameterSpec(String, String, AlgorithmParameterSpec, int, int)} constructor.
     *
     * @since 1.5
     */
    @Deprecated(since="19")
    public static final PSSParameterSpec DEFAULT = new PSSParameterSpec
        ("SHA-1", "MGF1", MGF1ParameterSpec.SHA1, 20, TRAILER_FIELD_BC);


    /**
     * Creates a new {@code PSSParameterSpec} as defined in
     * the PKCS #1 standard using the specified message digest,
     * mask generation function, parameters for mask generation
     * function, salt length, and trailer field values.
     *
     * @param mdName       the algorithm name of the hash function. See the
     *         PSSParameterSpec section of the
     *         <a href=
     *        "{@docRoot}/../specs/security/standard-names.html#pssparameterspec">
     *         Java Security Standard Algorithm Names Specification</a>
     *         for information about standard names for the hash function.
     * @param mgfName      the algorithm name of the mask generation function.
     *         See the PSSParameterSpec section of the
     *         <a href=
     *        "{@docRoot}/../specs/security/standard-names.html#pssparameterspec">
     *         Java Security Standard Algorithm Names Specification</a>
     *         for information about standard names for the mask generation
     *         function.
     * @param mgfSpec      the parameters for the mask generation function.
     *         If null is specified, null will be returned by
     *         getMGFParameters().
     * @param saltLen      the length of salt in bytes
     * @param trailerField the value of the trailer field
     * @throws    NullPointerException if {@code mdName}, or {@code mgfName}
     *         is null
     * @throws    IllegalArgumentException if {@code saltLen} or
     *         {@code trailerField} is less than 0
     * @since 1.5
     */
    public PSSParameterSpec(String mdName, String mgfName,
            AlgorithmParameterSpec mgfSpec, int saltLen, int trailerField) {
        Objects.requireNonNull(mdName, "digest algorithm is null");
        Objects.requireNonNull(mgfName,
            "mask generation function algorithm is null");
        if (saltLen < 0) {
            throw new IllegalArgumentException("negative saltLen value: " +
                                               saltLen);
        }
        if (trailerField < 0) {
            throw new IllegalArgumentException("negative trailerField: " +
                                               trailerField);
        }
        this.mdName = mdName;
        this.mgfName = mgfName;
        this.mgfSpec = mgfSpec;
        this.saltLen = saltLen;
        this.trailerField = trailerField;
    }

    /**
     * Creates a new {@code PSSParameterSpec}
     * using the specified salt length and other default values as
     * defined in the PKCS #1 standard.
     *
     * @param saltLen the length of salt in bytes
     * @throws    IllegalArgumentException if {@code saltLen} is
     *         less than 0
     * @spec https://www.rfc-editor.org/info/rfc8017
     *      RFC 8017: PKCS #1: RSA Cryptography Specifications Version 2.2
     * @deprecated This constructor uses the default values defined in
     *         the PKCS #1 standard except for the salt length. Some of these
     *         defaults are no longer recommended due to advances in
     *         cryptanalysis -- see the
     *         <a href="https://tools.ietf.org/rfc/rfc8017.txt">PKCS#1 v2.2</a>
     *         standard for more details. Thus, it is recommended to explicitly
     *         specify all desired parameter values with the
     *         {@link #PSSParameterSpec(String, String, AlgorithmParameterSpec, int, int)} constructor.
     */
    @Deprecated(since="19")
    public PSSParameterSpec(int saltLen) {
        this("SHA-1", "MGF1", MGF1ParameterSpec.SHA1, saltLen, TRAILER_FIELD_BC);
    }

    /**
     * Returns the message digest algorithm name.
     *
     * @return the message digest algorithm name
     * @since 1.5
     */
    public String getDigestAlgorithm() {
        return mdName;
    }

    /**
     * Returns the mask generation function algorithm name.
     *
     * @return the mask generation function algorithm name
     *
     * @since 1.5
     */
    public String getMGFAlgorithm() {
        return mgfName;
    }

    /**
     * Returns the parameters for the mask generation function.
     *
     * @return the parameters for the mask generation function
     * @since 1.5
     */
    public AlgorithmParameterSpec getMGFParameters() {
        return mgfSpec;
    }

    /**
     * Returns the salt length in bytes.
     *
     * @return the salt length
     */
    public int getSaltLength() {
        return saltLen;
    }

    /**
     * Returns the value for the trailer field.
     *
     * @return the value for the trailer field
     * @since 1.5
     */
    public int getTrailerField() {
        return trailerField;
    }

    @Override
    public String toString() {
        return "PSSParameterSpec[" + "hashAlgorithm=" + mdName + ", " +
                "maskGenAlgorithm=" + mgfSpec + ", " +
                "saltLength=" + saltLen + ", " +
                "trailerField=" + trailerField +
                ']';
    }
}
