/*
 * nimbus-jose-jwt
 *
 * Copyright 2012-2026, Connect2id Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use
 * this file except in compliance with the License. You may obtain a copy of the
 * License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed
 * under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
 * CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 */

package com.nimbusds.jose.crypto;


import java.util.Collections;
import java.util.Set;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

import com.nimbusds.jose.*;
import com.nimbusds.jose.crypto.impl.*;
import com.nimbusds.jose.crypto.opts.OptionUtils;
import com.nimbusds.jose.jwk.OctetSequenceKey;
import com.nimbusds.jose.util.Base64URL;
import net.jcip.annotations.ThreadSafe;


/**
 * Direct decrypter of {@link com.nimbusds.jose.JWEObject JWE objects} with a
 * shared symmetric key.
 *
 * <p>See RFC 7518
 * <a href="https://tools.ietf.org/html/rfc7518#section-4.5">section 4.5</a>
 * for more information.</p>
 *
 * <p>This class is thread-safe.
 *
 * <p>Supports the following key management algorithms:
 *
 * <ul>
 *     <li>{@link com.nimbusds.jose.JWEAlgorithm#DIR}
 * </ul>
 *
 * <p>Supports the following content encryption algorithms:
 *
 * <ul>
 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A128CBC_HS256} (requires 256 bit key)
 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A192CBC_HS384} (requires 384 bit key)
 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A256CBC_HS512} (requires 512 bit key)
 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A128GCM} (requires 128 bit key)
 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A192GCM} (requires 192 bit key)
 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A256GCM} (requires 256 bit key)
 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A128CBC_HS256_DEPRECATED} (requires 256 bit key)
 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A256CBC_HS512_DEPRECATED} (requires 512 bit key)
 *     <li>{@link com.nimbusds.jose.EncryptionMethod#XC20P} (requires 256 bit key)
 * </ul>
 *
 * <p>Also supports a promiscuous mode to decrypt any JWE by passing the
 * content encryption key (CEK) directly. The that mode the JWE algorithm
 * checks for ("alg":"dir") and encrypted key not being present will be
 * skipped.
 * 
 * @author Vladimir Dzhuvinov
 * @author Egor Puzanov
 * @version 2026-09-16
 */
@ThreadSafe
public class DirectDecrypter extends DirectCryptoProvider implements JWEDecrypter, CriticalHeaderParamsAware {
        
        
        /**
         * If set skips the checks for alg "dir" and encrypted key not present.
         */
        private final boolean promiscuousMode;


        /**
         * The critical header policy.
         */
        private final CriticalHeaderParamsDeferral critPolicy = new CriticalHeaderParamsDeferral();


        /**
         * The configured options, empty set if none.
         */
        private final Set<JWEDecrypterOption> opts;


        /**
         * Creates a new direct decrypter.
         *
         * @param key The symmetric key. Its algorithm should be "AES". Must be
         *            128 bits (16 bytes), 192 bits (24 bytes), 256 bits (32
         *            bytes), 384 bits (48 bytes) or 512 bits (64 bytes) long.
         *            Must not be {@code null}.
         *
         * @throws KeyLengthException If the symmetric key length is not
         *                            compatible.
         */
        public DirectDecrypter(final SecretKey key)
                throws KeyLengthException {

                this(key, false);
        }


        /**
         * Creates a new direct decrypter with the option to set it in
         * promiscuous mode.
         *
         * @param key             The symmetric key. Its algorithm should be
         *                        "AES". Must be 128 bits (16 bytes), 192 bits
         *                        (24 bytes), 256 bits (32 bytes), 384 bits (48
         *                        bytes) or 512 bits (64 bytes) long. Must not
         *                        be {@code null}.
         * @param promiscuousMode If {@code true} set the decrypter in
         *                        promiscuous mode to permit decryption of any
         *                        JWE with the supplied symmetric key. In that
         *                        mode the JWE algorithm checks for
         *                        ("alg":"dir") and encrypted key not being
         *                        present will be skipped.
         *
         * @throws KeyLengthException If the symmetric key length is not
         *                            compatible.
         */
        public DirectDecrypter(final SecretKey key, final boolean promiscuousMode)
                throws KeyLengthException {

                this(key, null, promiscuousMode, Collections.<JWEDecrypterOption>emptySet());
        }


        /**
         * Creates a new direct decrypter.
         *
         * @param keyBytes The symmetric key, as a byte array. Must be 128 bits
         *                 (16 bytes), 192 bits (24 bytes), 256 bits (32
         *                 bytes), 384 bits (48 bytes) or 512 bits (64 bytes)
         *                 long. Must not be {@code null}.
         *
         * @throws KeyLengthException If the symmetric key length is not
         *                            compatible.
         */
        public DirectDecrypter(final byte[] keyBytes)
                throws KeyLengthException {

                this(new SecretKeySpec(keyBytes, "AES"), false);
        }


        /**
         * Creates a new direct decrypter.
         *
         * @param octJWK The symmetric key, as a JWK. Must be 128 bits (16
         *               bytes), 192 bits (24 bytes), 256 bits (32 bytes), 384
         *               bits (48 bytes) or 512 bits (64 bytes) long. Must not
         *               be {@code null}.
         *
         * @throws KeyLengthException If the symmetric key length is not
         *                            compatible.
         */
        public DirectDecrypter(final OctetSequenceKey octJWK)
                throws KeyLengthException {

                this(octJWK.toSecretKey("AES"));
        }


        /**
         * Creates a new direct decrypter with the option to set it in
         * promiscuous mode.
         *
         * @param key            The symmetric key. Its algorithm should be
         *                       "AES". Must be 128 bits (16 bytes), 192 bits
         *                       (24 bytes), 256 bits (32 bytes), 384 bits (48
         *                       bytes) or 512 bits (64 bytes) long. Must not
         *                       be {@code null}.
         * @param defCritHeaders The names of the critical header parameters
         *                       that are deferred to the application for
         *                       processing, empty set or {@code null} if none.
         *
         * @throws KeyLengthException If the symmetric key length is not
         *                            compatible.
         */
        public DirectDecrypter(final SecretKey key, final Set<String> defCritHeaders)
                throws KeyLengthException {

                this(key, defCritHeaders, false);
        }


        /**
         * Creates a new direct decrypter.
         *
         * @param key            The symmetric key. Its algorithm should be
         *                       "AES". Must be 128 bits (16 bytes), 192 bits
         *                       (24 bytes), 256 bits (32 bytes), 384 bits (48
         *                       bytes) or 512 bits (64 bytes) long. Must not
         *                       be {@code null}.
         * @param defCritHeaders The names of the critical header parameters
         *                       that are deferred to the application for
         *                       processing, empty set or {@code null} if none.
         *@param promiscuousMode If {@code true} set the decrypter in
         *                       promiscuous mode to permit decryption of any
         *                       JWE with the supplied symmetric key. In that
         *                       mode the JWE algorithm checks for
         *                       ("alg":"dir") and encrypted key not being
         *                       present will be skipped.
         *
         * @throws KeyLengthException If the symmetric key length is not
         *                            compatible.
         */
        public DirectDecrypter(final SecretKey key,
                               final Set<String> defCritHeaders,
                               final boolean promiscuousMode)
                throws KeyLengthException {

                this(key, defCritHeaders, promiscuousMode, Collections.<JWEDecrypterOption>emptySet());
        }


        /**
         * Creates a new direct decrypter.
         *
         * @param key            The symmetric key. Its algorithm should be
         *                       "AES". Must be 128 bits (16 bytes), 192 bits
         *                       (24 bytes), 256 bits (32 bytes), 384 bits (48
         *                       bytes) or 512 bits (64 bytes) long. Must not
         *                       be {@code null}.
         * @param defCritHeaders The names of the critical header parameters
         *                       that are deferred to the application for
         *                       processing, empty set or {@code null} if none.
         * @param promiscuousMode If {@code true} set the decrypter in
         *                       promiscuous mode to permit decryption of any
         *                       JWE with the supplied symmetric key. The that
         *                       mode the JWE algorithm checks for
         *                       ("alg":"dir") and encrypted key not being
         *                       present will be skipped.
         * @param opts           The decryption options, empty or {@code null}
         *                       if none.
         *
         * @throws KeyLengthException If the symmetric key length is not
         *                            compatible.
         */
        public DirectDecrypter(final SecretKey key,
                               final Set<String> defCritHeaders,
                               final boolean promiscuousMode,
                               final Set<JWEDecrypterOption> opts)
                throws KeyLengthException {

                super(key);
                critPolicy.setDeferredCriticalHeaderParams(defCritHeaders);
                this.promiscuousMode = promiscuousMode;
                this.opts = opts != null ? opts : Collections.<JWEDecrypterOption>emptySet();
        }


        /**
         * Creates a new direct decrypter.
         *
         * @param key            The symmetric key. Its algorithm should be
         *                       "AES". Must be 128 bits (16 bytes), 192 bits
         *                       (24 bytes), 256 bits (32 bytes), 384 bits (48
         *                       bytes) or 512 bits (64 bytes) long. Must not
         *                       be {@code null}.
         * @param defCritHeaders The names of the critical header parameters
         *                       that are deferred to the application for
         *                       processing, empty set or {@code null} if none.
         * @param opts           The decryption options, empty or {@code null}
         *                       if none.
         *
         * @throws KeyLengthException If the symmetric key length is not
         *                            compatible.
         */
        public DirectDecrypter(final SecretKey key,
                               final Set<String> defCritHeaders,
                               final Set<JWEDecrypterOption> opts)
                throws KeyLengthException {

                this(key, defCritHeaders, false, opts);
        }


        /**
         * Creates a new direct decrypter with the option to set it in
         * promiscuous mode.
         *
         * @param key             The symmetric key. Its algorithm should be
         *                        "AES". Must be 128 bits (16 bytes), 192 bits
         *                        (24 bytes), 256 bits (32 bytes), 384 bits (48
         *                        bytes) or 512 bits (64 bytes) long. Must not
         *                        be {@code null}.
         * @param promiscuousMode If {@code true} set the decrypter in
         *                        promiscuous mode to permit decryption of any
         *                        JWE with the supplied symmetric key. In that
         *                        mode the JWE algorithm checks for
         *                        ("alg":"dir") and encrypted key not being
         *                        present will be skipped.
         * @param opts            The decryption options, empty or {@code null}
         *                        if none.
         *
         * @throws KeyLengthException If the symmetric key length is not
         *                            compatible.
         */
        public DirectDecrypter(final SecretKey key,
                               final boolean promiscuousMode,
                               final Set<JWEDecrypterOption> opts)
                throws KeyLengthException {

                this(key, null, promiscuousMode, opts);
        }


        /**
         * Creates a new direct decrypter.
         *
         * @param keyBytes The symmetric key, as a byte array. Must be 128 bits
         *                 (16 bytes), 192 bits (24 bytes), 256 bits (32
         *                 bytes), 384 bits (48 bytes) or 512 bits (64 bytes)
         *                 long. Must not be {@code null}.
         * @param opts     The decryption options, empty or {@code null} if
         *                 none.
         *
         * @throws KeyLengthException If the symmetric key length is not
         *                            compatible.
         */
        public DirectDecrypter(final byte[] keyBytes,
                               final Set<JWEDecrypterOption> opts)
                throws KeyLengthException {

                this(new SecretKeySpec(keyBytes, "AES"), null, false, opts);
        }


        /**
         * Creates a new direct decrypter.
         *
         * @param octJWK The symmetric key, as a JWK. Must be 128 bits (16
         *               bytes), 192 bits (24 bytes), 256 bits (32 bytes), 384
         *               bits (48 bytes) or 512 bits (64 bytes) long. Must not
         *               be {@code null}.
         * @param opts   The decryption options, empty or {@code null} if none.
         *
         * @throws KeyLengthException If the symmetric key length is not
         *                            compatible.
         */
        public DirectDecrypter(final OctetSequenceKey octJWK,
                               final Set<JWEDecrypterOption> opts)
                throws KeyLengthException {

                this(octJWK.toSecretKey("AES"), null, false, opts);
        }


        /**
         * Creates a new direct decrypter.
         *
         * @param octJWK         The symmetric key, as a JWK. Must be 128 bits
         *                       (16 bytes), 192 bits (24 bytes), 256 bits (32
         *                       bytes), 384 bits (48 bytes) or 512 bits (64
         *                       bytes) long. Must not be {@code null}.
         * @param defCritHeaders The names of the critical header parameters
         *                       that are deferred to the application for
         *                       processing, empty set or {@code null} if none.
         * @param opts           The decryption options, empty or {@code null}
         *                       if none.
         *
         * @throws KeyLengthException If the symmetric key length is not
         *                            compatible.
         */
        public DirectDecrypter(final OctetSequenceKey octJWK,
                               final Set<String> defCritHeaders,
                               final Set<JWEDecrypterOption> opts)
                throws KeyLengthException {

                this(octJWK.toSecretKey("AES"), defCritHeaders, false, opts);
        }


        @Override
        public Set<String> getProcessedCriticalHeaderParams() {

                return critPolicy.getProcessedCriticalHeaderParams();
        }


        @Override
        public Set<String> getDeferredCriticalHeaderParams() {

                return critPolicy.getDeferredCriticalHeaderParams();
        }


        /**
         * Decrypts the specified cipher text of a {@link JWEObject JWE Object}.
         *
         * @param header       The JSON Web Encryption (JWE) header. Must
         *                     specify a supported JWE algorithm and method.
         *                     Must not be {@code null}.
         * @param encryptedKey The encrypted key, {@code null} if not required
         *                     by the JWE algorithm.
         * @param iv           The initialisation vector, {@code null} if not
         *                     required by the JWE algorithm.
         * @param cipherText   The cipher text to decrypt. Must not be
         *                     {@code null}.
         * @param authTag      The authentication tag, {@code null} if not
         *                     required.
         *
         * @return The clear text.
         *
         * @throws JOSEException If the JWE algorithm or method is not
         *                       supported, if a critical header parameter is
         *                       not supported or marked for deferral to the
         *                       application, or if decryption failed for some
         *                       other reason.
         */
        @Deprecated
        public byte[] decrypt(final JWEHeader header,
                       final Base64URL encryptedKey,
                       final Base64URL iv,
                       final Base64URL cipherText,
                       final Base64URL authTag)
                throws JOSEException {

                return decrypt(header, encryptedKey, iv, cipherText, authTag, AAD.compute(header));
        }


        @Override
        public byte[] decrypt(final JWEHeader header,
                              final Base64URL encryptedKey,
                              final Base64URL iv,
                              final Base64URL cipherText,
                              final Base64URL authTag,
                              final byte[] aad)
                throws JOSEException {

                // Validate required JWE parts
                if (! promiscuousMode) {
                        
                        JWEAlgorithm alg = JWEHeaderValidation.getAlgorithmAndEnsureNotNull(header);
                        
                        if (!alg.equals(JWEAlgorithm.DIR)) {
                                throw new JOSEException(AlgorithmSupportMessage.unsupportedJWEAlgorithm(alg, SUPPORTED_ALGORITHMS));
                        }
                        
                        if (encryptedKey != null) {
                                throw new JOSEException("Unexpected present JWE encrypted key");
                        }
                }
                
                if (iv == null) {
                        throw new JOSEException("Unexpected present JWE initialization vector (IV)");
                }

                if (authTag == null) {
                        throw new JOSEException("Missing JWE authentication tag");
                }

                critPolicy.ensureHeaderPasses(header);

                int maxDecompressedLength = OptionUtils.resolveMaxDecompressedPlainTextLength(opts);

                return ContentCryptoProvider.decrypt(header, aad, null, iv, cipherText, authTag, getKey(), getJCAContext(), maxDecompressedLength);
        }
}