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package java.security.spec;

import java.util.Objects;

/**

 * This class specifies a parameter spec for 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 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>

 * <p>Note: the PSSParameterSpec.DEFAULT uses the following:

 *     message digest  -- "SHA-1"

 *     mask generation function (mgf) -- "MGF1"

 *     parameters for mgf -- MGF1ParameterSpec.SHA1

 *     SaltLength   -- 20

 *     TrailerField -- 1

 *

 * @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 PKCS#1

     *

     * @since 11

     */

    public static final int TRAILER_FIELD_BC = 1;

    /**

     * The PSS parameter set with all default values

     *

     * @since 1.5

     */

    public static final PSSParameterSpec DEFAULT = new PSSParameterSpec

        ("SHA-1", "MGF1", MGF1ParameterSpec.SHA1, 20, TRAILER_FIELD_BC);

    // disallowed

    private PSSParameterSpec() {

        throw new RuntimeException("default constructor not allowed");

    }

    /**

     * 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

     * @param mgfName      the algorithm name of 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

     * @param trailerField the value of the trailer field

     *         is null

     *         {@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 PKCS#1.

     *

     * @param saltLen the length of salt in bytes to be used in PKCS#1

     *         PSS encoding

     *         less than 0

     */

    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() {

        StringBuilder sb = new StringBuilder();

        sb.append("MD: " + mdName + "\n")

                .append("MGF: " + mgfSpec + "\n")

                .append("SaltLength: " + saltLen + "\n")

                .append("TrailerField: " + trailerField + "\n");

        return sb.toString();

    }

}