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	/*
	* Copyright (c) 2018, 2021, 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 sun.security.rsa;

	import java.io.IOException;
	import java.nio.ByteBuffer;

	import java.security.*;
	import java.security.spec.AlgorithmParameterSpec;
	import java.security.spec.PSSParameterSpec;
	import java.security.spec.MGF1ParameterSpec;
	import java.security.interfaces.*;

	import java.util.Arrays;
	import java.util.Hashtable;

	import sun.security.util.*;
	import sun.security.jca.JCAUtil;


	/**
	* PKCS#1 v2.2 RSASSA-PSS signatures with various message digest algorithms.
	* RSASSA-PSS implementation takes the message digest algorithm, MGF algorithm,
	* and salt length values through the required signature PSS parameters.
	* We support SHA-1, SHA-2 family and SHA3 family of message digest algorithms,
	* and MGF1 mask generation function.
	*
	* @since 11
	*/
	public class RSAPSSSignature extends SignatureSpi {

	private static final boolean DEBUG = false;

	// utility method for comparing digest algorithms
	// NOTE that first argument is assumed to be standard digest name
	private boolean isDigestEqual(String stdAlg, String givenAlg) {
	if (stdAlg == null \|\| givenAlg == null) return false;

	if (givenAlg.indexOf("-") != -1) {
	return stdAlg.equalsIgnoreCase(givenAlg);
	} else {
	if (stdAlg.equals("SHA-1")) {
	return (givenAlg.equalsIgnoreCase("SHA")
	\|\| givenAlg.equalsIgnoreCase("SHA1"));
	} else {
	StringBuilder sb = new StringBuilder(givenAlg);
	// case-insensitive check
	if (givenAlg.regionMatches(true, 0, "SHA", 0, 3)) {
	givenAlg = sb.insert(3, "-").toString();
	return stdAlg.equalsIgnoreCase(givenAlg);
	} else {
	throw new ProviderException("Unsupported digest algorithm "
	+ givenAlg);
	}
	}
	}
	}

	private static final byte[] EIGHT_BYTES_OF_ZEROS = new byte[8];

	private static final Hashtable<KnownOIDs, Integer> DIGEST_LENGTHS =
	new Hashtable<KnownOIDs, Integer>();
	static {
	DIGEST_LENGTHS.put(KnownOIDs.SHA_1, 20);
	DIGEST_LENGTHS.put(KnownOIDs.SHA_224, 28);
	DIGEST_LENGTHS.put(KnownOIDs.SHA_256, 32);
	DIGEST_LENGTHS.put(KnownOIDs.SHA_384, 48);
	DIGEST_LENGTHS.put(KnownOIDs.SHA_512, 64);
	DIGEST_LENGTHS.put(KnownOIDs.SHA_512$224, 28);
	DIGEST_LENGTHS.put(KnownOIDs.SHA_512$256, 32);
	DIGEST_LENGTHS.put(KnownOIDs.SHA3_224, 28);
	DIGEST_LENGTHS.put(KnownOIDs.SHA3_256, 32);
	DIGEST_LENGTHS.put(KnownOIDs.SHA3_384, 48);
	DIGEST_LENGTHS.put(KnownOIDs.SHA3_512, 64);
	}

	// message digest implementation we use for hashing the data
	private MessageDigest md;
	// flag indicating whether the digest is reset
	private boolean digestReset = true;

	// private key, if initialized for signing
	private RSAPrivateKey privKey = null;
	// public key, if initialized for verifying
	private RSAPublicKey pubKey = null;
	// PSS parameters from signatures and keys respectively
	private PSSParameterSpec sigParams = null; // required for PSS signatures

	// PRNG used to generate salt bytes if none given
	private SecureRandom random;

	/**
	* Construct a new RSAPSSSignatur with arbitrary digest algorithm
	*/
	public RSAPSSSignature() {
	this.md = null;
	}

	// initialize for verification. See JCA doc
	@Override
	protected void engineInitVerify(PublicKey publicKey)
	throws InvalidKeyException {
	if (!(publicKey instanceof RSAPublicKey)) {
	throw new InvalidKeyException("key must be RSAPublicKey");
	}
	this.pubKey = (RSAPublicKey) isValid((RSAKey)publicKey);
	this.privKey = null;
	resetDigest();
	}

	// initialize for signing. See JCA doc
	@Override
	protected void engineInitSign(PrivateKey privateKey)
	throws InvalidKeyException {
	engineInitSign(privateKey, null);
	}

	// initialize for signing. See JCA doc
	@Override
	protected void engineInitSign(PrivateKey privateKey, SecureRandom random)
	throws InvalidKeyException {
	if (!(privateKey instanceof RSAPrivateKey)) {
	throw new InvalidKeyException("key must be RSAPrivateKey");
	}
	this.privKey = (RSAPrivateKey) isValid((RSAKey)privateKey);
	this.pubKey = null;
	this.random =
	(random == null? JCAUtil.getSecureRandom() : random);
	resetDigest();
	}

	/**
	* Utility method for checking the key PSS parameters against signature
	* PSS parameters.
	* Returns false if any of the digest/MGF algorithms and trailerField
	* values does not match or if the salt length in key parameters is
	* larger than the value in signature parameters.
	*/
	private static boolean isCompatible(AlgorithmParameterSpec keyParams,
	PSSParameterSpec sigParams) {
	if (keyParams == null) {
	// key with null PSS parameters means no restriction
	return true;
	}
	if (!(keyParams instanceof PSSParameterSpec)) {
	return false;
	}
	// nothing to compare yet, defer the check to when sigParams is set
	if (sigParams == null) {
	return true;
	}
	PSSParameterSpec pssKeyParams = (PSSParameterSpec) keyParams;
	// first check the salt length requirement
	if (pssKeyParams.getSaltLength() > sigParams.getSaltLength()) {
	return false;
	}

	// compare equality of the rest of fields based on DER encoding
	PSSParameterSpec keyParams2 =
	new PSSParameterSpec(pssKeyParams.getDigestAlgorithm(),
	pssKeyParams.getMGFAlgorithm(),
	pssKeyParams.getMGFParameters(),
	sigParams.getSaltLength(),
	pssKeyParams.getTrailerField());
	PSSParameters ap = new PSSParameters();
	// skip the JCA overhead
	try {
	ap.engineInit(keyParams2);
	byte[] encoded = ap.engineGetEncoded();
	ap.engineInit(sigParams);
	byte[] encoded2 = ap.engineGetEncoded();
	return Arrays.equals(encoded, encoded2);
	} catch (Exception e) {
	if (DEBUG) {
	e.printStackTrace();
	}
	return false;
	}
	}

	/**
	* Validate the specified RSAKey and its associated parameters against
	* internal signature parameters.
	*/
	private RSAKey isValid(RSAKey rsaKey) throws InvalidKeyException {
	AlgorithmParameterSpec keyParams = rsaKey.getParams();
	// validate key parameters
	if (!isCompatible(rsaKey.getParams(), this.sigParams)) {
	throw new InvalidKeyException
	("Key contains incompatible PSS parameter values");
	}
	// validate key length
	if (this.sigParams != null) {
	String digestAlgo = this.sigParams.getDigestAlgorithm();
	KnownOIDs ko = KnownOIDs.findMatch(digestAlgo);
	if (ko != null) {
	Integer hLen = DIGEST_LENGTHS.get(ko);
	if (hLen != null) {
	checkKeyLength(rsaKey, hLen,
	this.sigParams.getSaltLength());
	} else {
	// should never happen; checked in validateSigParams()
	throw new ProviderException
	("Unsupported digest algo: " + digestAlgo);
	}
	} else {
	// should never happen; checked in validateSigParams()
	throw new ProviderException
	("Unrecognized digest algo: " + digestAlgo);
	}
	}
	return rsaKey;
	}

	/**
	* Validate the specified Signature PSS parameters.
	*/
	private PSSParameterSpec validateSigParams(AlgorithmParameterSpec p)
	throws InvalidAlgorithmParameterException {
	if (p == null) {
	throw new InvalidAlgorithmParameterException
	("Parameters cannot be null");
	}
	if (!(p instanceof PSSParameterSpec)) {
	throw new InvalidAlgorithmParameterException
	("parameters must be type PSSParameterSpec");
	}
	// no need to validate again if same as current signature parameters
	PSSParameterSpec params = (PSSParameterSpec) p;
	if (params == this.sigParams) return params;

	RSAKey key = (this.privKey == null? this.pubKey : this.privKey);
	// check against keyParams if set
	if (key != null) {
	if (!isCompatible(key.getParams(), params)) {
	throw new InvalidAlgorithmParameterException
	("Signature parameters does not match key parameters");
	}
	}
	// now sanity check the parameter values
	if (!(params.getMGFAlgorithm().equalsIgnoreCase("MGF1"))) {
	throw new InvalidAlgorithmParameterException("Only supports MGF1");

	}
	if (params.getTrailerField() != PSSParameterSpec.TRAILER_FIELD_BC) {
	throw new InvalidAlgorithmParameterException
	("Only supports TrailerFieldBC(1)");

	}

	// check key length again
	if (key != null) {
	String digestAlgo = params.getDigestAlgorithm();
	KnownOIDs ko = KnownOIDs.findMatch(digestAlgo);
	if (ko != null) {
	Integer hLen = DIGEST_LENGTHS.get(ko);
	if (hLen != null) {
	try {
	checkKeyLength(key, hLen, params.getSaltLength());
	} catch (InvalidKeyException e) {
	throw new InvalidAlgorithmParameterException(e);
	}
	} else {
	throw new InvalidAlgorithmParameterException
	("Unsupported digest algo: " + digestAlgo);
	}
	} else {
	throw new InvalidAlgorithmParameterException
	("Unrecognized digest algo: " + digestAlgo);
	}
	}
	return params;
	}

	/**
	* Ensure the object is initialized with key and parameters and
	* reset digest
	*/
	private void ensureInit() throws SignatureException {
	RSAKey key = (this.privKey == null? this.pubKey : this.privKey);
	if (key == null) {
	throw new SignatureException("Missing key");
	}
	if (this.sigParams == null) {
	// Parameters are required for signature verification
	throw new SignatureException
	("Parameters required for RSASSA-PSS signatures");
	}
	}

	/**
	* Utility method for checking key length against digest length and
	* salt length
	*/
	private static void checkKeyLength(RSAKey key, int digestLen,
	int saltLen) throws InvalidKeyException {
	if (key != null) {
	int keyLength = (getKeyLengthInBits(key) + 7) >> 3;
	int minLength = Math.addExact(Math.addExact(digestLen, saltLen), 2);
	if (keyLength < minLength) {
	throw new InvalidKeyException
	("Key is too short, need min " + minLength + " bytes");
	}
	}
	}

	/**
	* Reset the message digest if it is not already reset.
	*/
	private void resetDigest() {
	if (digestReset == false) {
	this.md.reset();
	digestReset = true;
	}
	}

	/**
	* Return the message digest value.
	*/
	private byte[] getDigestValue() {
	digestReset = true;
	return this.md.digest();
	}

	// update the signature with the plaintext data. See JCA doc
	@Override
	protected void engineUpdate(byte b) throws SignatureException {
	ensureInit();
	this.md.update(b);
	digestReset = false;
	}

	// update the signature with the plaintext data. See JCA doc
	@Override
	protected void engineUpdate(byte[] b, int off, int len)
	throws SignatureException {
	ensureInit();
	this.md.update(b, off, len);
	digestReset = false;
	}

	// update the signature with the plaintext data. See JCA doc
	@Override
	protected void engineUpdate(ByteBuffer b) {
	try {
	ensureInit();
	} catch (SignatureException se) {
	// workaround for API bug
	throw new RuntimeException(se.getMessage());
	}
	this.md.update(b);
	digestReset = false;
	}

	// sign the data and return the signature. See JCA doc
	@Override
	protected byte[] engineSign() throws SignatureException {
	ensureInit();
	byte[] mHash = getDigestValue();
	try {
	byte[] encoded = encodeSignature(mHash);
	byte[] encrypted = RSACore.rsa(encoded, privKey, true);
	return encrypted;
	} catch (GeneralSecurityException e) {
	throw new SignatureException("Could not sign data", e);
	} catch (IOException e) {
	throw new SignatureException("Could not encode data", e);
	}
	}

	// verify the data and return the result. See JCA doc
	// should be reset to the state after engineInitVerify call.
	@Override
	protected boolean engineVerify(byte[] sigBytes) throws SignatureException {
	ensureInit();
	try {
	if (sigBytes.length != RSACore.getByteLength(this.pubKey)) {
	throw new SignatureException
	("Signature length not correct: got "
	+ sigBytes.length + " but was expecting "
	+ RSACore.getByteLength(this.pubKey));
	}
	byte[] mHash = getDigestValue();
	byte[] decrypted = RSACore.rsa(sigBytes, this.pubKey);
	return decodeSignature(mHash, decrypted);
	} catch (javax.crypto.BadPaddingException e) {
	// occurs if the app has used the wrong RSA public key
	// or if sigBytes is invalid
	// return false rather than propagating the exception for
	// compatibility/ease of use
	return false;
	} catch (IOException e) {
	throw new SignatureException("Signature encoding error", e);
	} finally {
	resetDigest();
	}
	}

	// return the modulus length in bits
	private static int getKeyLengthInBits(RSAKey k) {
	if (k != null) {
	return k.getModulus().bitLength();
	}
	return -1;
	}

	/**
	* Encode the digest 'mHash', return the to-be-signed data.
	* Also used by the PKCS#11 provider.
	*/
	private byte[] encodeSignature(byte[] mHash)
	throws IOException, DigestException {
	AlgorithmParameterSpec mgfParams = this.sigParams.getMGFParameters();
	String mgfDigestAlgo;
	if (mgfParams != null) {
	mgfDigestAlgo =
	((MGF1ParameterSpec) mgfParams).getDigestAlgorithm();
	} else {
	mgfDigestAlgo = this.md.getAlgorithm();
	}
	try {
	int emBits = getKeyLengthInBits(this.privKey) - 1;
	int emLen = (emBits + 7) >> 3;
	int hLen = this.md.getDigestLength();
	int dbLen = emLen - hLen - 1;
	int sLen = this.sigParams.getSaltLength();

	// maps DB into the corresponding region of EM and
	// stores its bytes directly into EM
	byte[] em = new byte[emLen];

	// step7 and some of step8
	em[dbLen - sLen - 1] = (byte) 1; // set DB's padding2 into EM
	em[em.length - 1] = (byte) 0xBC; // set trailer field of EM

	if (!digestReset) {
	throw new ProviderException("Digest should be reset");
	}
	// step5: generates M' using padding1, mHash, and salt
	this.md.update(EIGHT_BYTES_OF_ZEROS);
	digestReset = false; // mark digest as it now has data
	this.md.update(mHash);
	if (sLen != 0) {
	// step4: generate random salt
	byte[] salt = new byte[sLen];
	this.random.nextBytes(salt);
	this.md.update(salt);

	// step8: set DB's salt into EM
	System.arraycopy(salt, 0, em, dbLen - sLen, sLen);
	}
	// step6: generate H using M'
	this.md.digest(em, dbLen, hLen); // set H field of EM
	digestReset = true;

	// step7 and 8 are already covered by the code which setting up
	// EM as above

	// step9 and 10: feed H into MGF and xor with DB in EM
	MGF1 mgf1 = new MGF1(mgfDigestAlgo);
	mgf1.generateAndXor(em, dbLen, hLen, dbLen, em, 0);

	// step11: set the leftmost (8emLen - emBits) bits of the leftmost
	// octet to 0
	int numZeroBits = (emLen << 3) - emBits;

	if (numZeroBits != 0) {
	byte MASK = (byte) (0xff >>> numZeroBits);
	em[0] = (byte) (em[0] & MASK);
	}

	// step12: em should now holds maskedDB \|\| hash h \|\| 0xBC
	return em;
	} catch (NoSuchAlgorithmException e) {
	throw new IOException(e.toString());
	}
	}

	/**
	* Decode the signature data as under RFC8017 sec9.1.2 EMSA-PSS-VERIFY
	*/
	private boolean decodeSignature(byte[] mHash, byte[] em)
	throws IOException {
	int hLen = mHash.length;
	int sLen = this.sigParams.getSaltLength();
	int emBits = getKeyLengthInBits(this.pubKey) - 1;
	int emLen = (emBits + 7) >> 3;

	// When key length is 8N+1 bits (N+1 bytes), emBits = 8N,
	// emLen = N which is one byte shorter than em.length.
	// Otherwise, emLen should be same as em.length
	int emOfs = em.length - emLen;
	if ((emOfs == 1) && (em[0] != 0)) {
	return false;
	}

	// step3
	if (emLen < (hLen + sLen + 2)) {
	return false;
	}

	// step4
	if (em[emOfs + emLen - 1] != (byte) 0xBC) {
	return false;
	}

	// step6: check if the leftmost (8emLen - emBits) bits of the leftmost
	// octet are 0
	int numZeroBits = (emLen << 3) - emBits;

	if (numZeroBits != 0) {
	byte MASK = (byte) (0xff << (8 - numZeroBits));
	if ((em[emOfs] & MASK) != 0) {
	return false;
	}
	}
	String mgfDigestAlgo;
	AlgorithmParameterSpec mgfParams = this.sigParams.getMGFParameters();
	if (mgfParams != null) {
	mgfDigestAlgo =
	((MGF1ParameterSpec) mgfParams).getDigestAlgorithm();
	} else {
	mgfDigestAlgo = this.md.getAlgorithm();
	}
	// step 7 and 8
	int dbLen = emLen - hLen - 1;
	try {
	MGF1 mgf1 = new MGF1(mgfDigestAlgo);
	mgf1.generateAndXor(em, emOfs + dbLen, hLen, dbLen,
	em, emOfs);
	} catch (NoSuchAlgorithmException nsae) {
	throw new IOException(nsae.toString());
	}

	// step9: set the leftmost (8emLen - emBits) bits of the leftmost
	// octet to 0
	if (numZeroBits != 0) {
	byte MASK = (byte) (0xff >>> numZeroBits);
	em[emOfs] = (byte) (em[emOfs] & MASK);
	}

	// step10
	int i = emOfs;
	for (; i < emOfs + (dbLen - sLen - 1); i++) {
	if (em[i] != 0) {
	return false;
	}
	}
	if (em[i] != 0x01) {
	return false;
	}
	// step12 and 13
	this.md.update(EIGHT_BYTES_OF_ZEROS);
	digestReset = false;
	this.md.update(mHash);
	if (sLen > 0) {
	this.md.update(em, emOfs + (dbLen - sLen), sLen);
	}
	byte[] digest2 = this.md.digest();
	digestReset = true;

	// step14
	byte[] digestInEM = Arrays.copyOfRange(em, emOfs + dbLen,
	emOfs + emLen - 1);
	return MessageDigest.isEqual(digest2, digestInEM);
	}

	// set parameter, not supported. See JCA doc
	@Deprecated
	@Override
	protected void engineSetParameter(String param, Object value)
	throws InvalidParameterException {
	throw new UnsupportedOperationException("setParameter() not supported");
	}

	@Override
	protected void engineSetParameter(AlgorithmParameterSpec params)
	throws InvalidAlgorithmParameterException {
	this.sigParams = validateSigParams(params);
	// disallow changing parameters when digest has been used
	if (!digestReset) {
	throw new ProviderException
	("Cannot set parameters during operations");
	}
	String newHashAlg = this.sigParams.getDigestAlgorithm();
	// re-allocate md if not yet assigned or algorithm changed
	if ((this.md == null) \|\|
	!(this.md.getAlgorithm().equalsIgnoreCase(newHashAlg))) {
	try {
	this.md = MessageDigest.getInstance(newHashAlg);
	} catch (NoSuchAlgorithmException nsae) {
	// should not happen as we pick default digest algorithm
	throw new InvalidAlgorithmParameterException
	("Unsupported digest algorithm " +
	newHashAlg, nsae);
	}
	}
	}

	// get parameter, not supported. See JCA doc
	@Deprecated
	@Override
	protected Object engineGetParameter(String param)
	throws InvalidParameterException {
	throw new UnsupportedOperationException("getParameter() not supported");
	}

	@Override
	protected AlgorithmParameters engineGetParameters() {
	AlgorithmParameters ap = null;
	if (this.sigParams != null) {
	try {
	ap = AlgorithmParameters.getInstance("RSASSA-PSS");
	ap.init(this.sigParams);
	} catch (GeneralSecurityException gse) {
	throw new ProviderException(gse.getMessage());
	}
	}
	return ap;
	}
	}

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