/*
    * Copyright 2015 The Netty Project
    *
    * The Netty Project licenses this file to you 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:
    *
    *   https://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 io.netty.handler.ssl;
  
  import io.netty.handler.ssl.util.KeyManagerFactoryWrapper;
  import io.netty.handler.ssl.util.TrustManagerFactoryWrapper;
  import io.netty.util.internal.UnstableApi;
  
  import javax.net.ssl.KeyManager;
  import javax.net.ssl.KeyManagerFactory;
  import javax.net.ssl.SNIHostName;
  import javax.net.ssl.SNIServerName;
  import javax.net.ssl.SSLEngine;
  import javax.net.ssl.SSLException;
  import javax.net.ssl.SSLParameters;
  import javax.net.ssl.TrustManager;
  import javax.net.ssl.TrustManagerFactory;
  import java.io.File;
  import java.io.InputStream;
  import java.security.KeyStore;
  import java.security.PrivateKey;
  import java.security.Provider;
  import java.security.SecureRandom;
  import java.security.cert.X509Certificate;
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  import static io.netty.util.internal.EmptyArrays.EMPTY_STRINGS;
  import static io.netty.util.internal.EmptyArrays.EMPTY_X509_CERTIFICATES;
  import static io.netty.util.internal.ObjectUtil.checkNotNull;
  import static io.netty.util.internal.ObjectUtil.checkNotNullWithIAE;
  import static io.netty.util.internal.ObjectUtil.checkNonEmpty;
  
  /**
   * Builder for configuring a new SslContext for creation.
   */
  public final class SslContextBuilder {
      @SuppressWarnings("rawtypes")
      private static final Map.Entry[] EMPTY_ENTRIES = new Map.Entry[0];
  
      /**
       * Creates a builder for new client-side {@link SslContext}.
       */
      public static SslContextBuilder forClient() {
          return new SslContextBuilder(false);
      }
  
      /**
       * Creates a builder for new server-side {@link SslContext}.
       *
       * @param keyCertChainFile an X.509 certificate chain file in PEM format
       * @param keyFile a PKCS#8 private key file in PEM format
       * @see #keyManager(File, File)
       */
      public static SslContextBuilder forServer(File keyCertChainFile, File keyFile) {
          return new SslContextBuilder(true).keyManager(keyCertChainFile, keyFile);
      }
  
      /**
       * Creates a builder for new server-side {@link SslContext}.
       *
       * @param keyCertChainInputStream   an input stream for an X.509 certificate chain in PEM format. The caller is
       *                                  responsible for calling {@link InputStream#close()} after {@link #build()}
       *                                  has been called.
       * @param keyInputStream            an input stream for a PKCS#8 private key in PEM format. The caller is
       *                                  responsible for calling {@link InputStream#close()} after {@link #build()}
       *                                  has been called.
       *
       * @see #keyManager(InputStream, InputStream)
       */
      public static SslContextBuilder forServer(InputStream keyCertChainInputStream, InputStream keyInputStream) {
          return new SslContextBuilder(true).keyManager(keyCertChainInputStream, keyInputStream);
      }
  
      /**
       * Creates a builder for new server-side {@link SslContext}.
       *
       * @param key a PKCS#8 private key
       * @param keyCertChain the X.509 certificate chain
       * @see #keyManager(PrivateKey, X509Certificate[])
       */
      public static SslContextBuilder forServer(PrivateKey key, X509Certificate... keyCertChain) {
          return new SslContextBuilder(true).keyManager(key, keyCertChain);
     }
 
     /**
      * Creates a builder for new server-side {@link SslContext}.
      *
      * @param key a PKCS#8 private key
      * @param keyCertChain the X.509 certificate chain
      * @see #keyManager(PrivateKey, X509Certificate[])
      */
     public static SslContextBuilder forServer(PrivateKey key, Iterable<? extends X509Certificate> keyCertChain) {
         return forServer(key, toArray(keyCertChain, EMPTY_X509_CERTIFICATES));
     }
 
     /**
      * Creates a builder for new server-side {@link SslContext}.
      *
      * @param keyCertChainFile an X.509 certificate chain file in PEM format
      * @param keyFile a PKCS#8 private key file in PEM format
      * @param keyPassword the password of the {@code keyFile}, or {@code null} if it's not
      *     password-protected
      * @see #keyManager(File, File, String)
      */
     public static SslContextBuilder forServer(
             File keyCertChainFile, File keyFile, String keyPassword) {
         return new SslContextBuilder(true).keyManager(keyCertChainFile, keyFile, keyPassword);
     }
 
     /**
      * Creates a builder for new server-side {@link SslContext}.
      *
      * @param keyCertChainInputStream   an input stream for an X.509 certificate chain in PEM format. The caller is
      *                                  responsible for calling {@link InputStream#close()} after {@link #build()}
      *                                  has been called.
      * @param keyInputStream            an input stream for a PKCS#8 private key in PEM format. The caller is
      *                                  responsible for calling {@link InputStream#close()} after {@link #build()}
      *                                  has been called.
      * @param keyPassword the password of the {@code keyFile}, or {@code null} if it's not
      *     password-protected
      * @see #keyManager(InputStream, InputStream, String)
      */
     public static SslContextBuilder forServer(
             InputStream keyCertChainInputStream, InputStream keyInputStream, String keyPassword) {
         return new SslContextBuilder(true).keyManager(keyCertChainInputStream, keyInputStream, keyPassword);
     }
 
     /**
      * Creates a builder for new server-side {@link SslContext}.
      *
      * @param key a PKCS#8 private key
      * @param keyCertChain the X.509 certificate chain
      * @param keyPassword the password of the {@code keyFile}, or {@code null} if it's not
      *     password-protected
      * @see #keyManager(File, File, String)
      */
     public static SslContextBuilder forServer(
             PrivateKey key, String keyPassword, X509Certificate... keyCertChain) {
         return new SslContextBuilder(true).keyManager(key, keyPassword, keyCertChain);
     }
 
     /**
      * Creates a builder for new server-side {@link SslContext}.
      *
      * @param key a PKCS#8 private key
      * @param keyCertChain the X.509 certificate chain
      * @param keyPassword the password of the {@code keyFile}, or {@code null} if it's not
      *     password-protected
      * @see #keyManager(File, File, String)
      */
     public static SslContextBuilder forServer(
             PrivateKey key, String keyPassword, Iterable<? extends X509Certificate> keyCertChain) {
         return forServer(key, keyPassword, toArray(keyCertChain, EMPTY_X509_CERTIFICATES));
     }
 
     /**
      * Creates a builder for new server-side {@link SslContext}.
      * <p>
      * If you use {@link SslProvider#OPENSSL} or {@link SslProvider#OPENSSL_REFCNT} consider using
      * {@link OpenSslX509KeyManagerFactory} or {@link OpenSslCachingX509KeyManagerFactory}.
      *
      * @param keyManagerFactory non-{@code null} factory for server's private key
      * @see #keyManager(KeyManagerFactory)
      */
     public static SslContextBuilder forServer(KeyManagerFactory keyManagerFactory) {
         return new SslContextBuilder(true).keyManager(keyManagerFactory);
     }
 
     /**
      * Creates a builder for new server-side {@link SslContext} with {@link KeyManager}.
      *
      * @param keyManager non-{@code null} KeyManager for server's private key
      */
     public static SslContextBuilder forServer(KeyManager keyManager) {
         return new SslContextBuilder(true).keyManager(keyManager);
     }
 
     private final boolean forServer;
     private SslProvider provider;
     private Provider sslContextProvider;
     private X509Certificate[] trustCertCollection;
     private TrustManagerFactory trustManagerFactory;
     private X509Certificate[] keyCertChain;
     private PrivateKey key;
     private String keyPassword;
     private KeyManagerFactory keyManagerFactory;
     private Iterable<String> ciphers;
     private CipherSuiteFilter cipherFilter = IdentityCipherSuiteFilter.INSTANCE;
     private ApplicationProtocolConfig apn;
     private long sessionCacheSize;
     private long sessionTimeout;
     private ClientAuth clientAuth = ClientAuth.NONE;
     private String[] protocols;
     private boolean startTls;
     private boolean enableOcsp;
     private SecureRandom secureRandom;
     private String keyStoreType = KeyStore.getDefaultType();
     private String endpointIdentificationAlgorithm;
     private final Map<SslContextOption<?>, Object> options = new HashMap<SslContextOption<?>, Object>();
     private final List<SNIServerName> serverNames;
 
     private SslContextBuilder(boolean forServer) {
         this.forServer = forServer;
         if (!forServer) {
             endpointIdentificationAlgorithm = SslUtils.defaultEndpointVerificationAlgorithm;
         }
         serverNames = forServer ? null : new ArrayList<>(2); // Only for clients.
     }
 
     /**
      * Configure a {@link SslContextOption}.
      */
     public <T> SslContextBuilder option(SslContextOption<T> option, T value) {
         if (value == null) {
             options.remove(option);
         } else {
             options.put(option, value);
         }
         return this;
     }
 
     /**
      * The {@link SslContext} implementation to use. {@code null} uses the default one.
      */
     public SslContextBuilder sslProvider(SslProvider provider) {
         this.provider = provider;
         return this;
     }
 
     /**
      * Sets the {@link KeyStore} type that should be used. {@code null} uses the default one.
      */
     public SslContextBuilder keyStoreType(String keyStoreType) {
         this.keyStoreType = keyStoreType;
         return this;
     }
 
     /**
      * The SSLContext {@link Provider} to use. {@code null} uses the default one. This is only
      * used with {@link SslProvider#JDK}.
      */
     public SslContextBuilder sslContextProvider(Provider sslContextProvider) {
         this.sslContextProvider = sslContextProvider;
         return this;
     }
 
     /**
      * Trusted certificates for verifying the remote endpoint's certificate. The file should
      * contain an X.509 certificate collection in PEM format. {@code null} uses the system default.
      */
     public SslContextBuilder trustManager(File trustCertCollectionFile) {
         try {
             return trustManager(SslContext.toX509Certificates(trustCertCollectionFile));
         } catch (Exception e) {
             throw new IllegalArgumentException("File does not contain valid certificates: "
                     + trustCertCollectionFile, e);
         }
     }
 
     /**
      * Trusted certificates for verifying the remote endpoint's certificate. The input stream should
      * contain an X.509 certificate collection in PEM format. {@code null} uses the system default.
      * <p>
      * The caller is responsible for calling {@link InputStream#close()} after {@link #build()} has been called.
      */
     public SslContextBuilder trustManager(InputStream trustCertCollectionInputStream) {
         try {
             return trustManager(SslContext.toX509Certificates(trustCertCollectionInputStream));
         } catch (Exception e) {
             throw new IllegalArgumentException("Input stream does not contain valid certificates.", e);
         }
     }
 
     /**
      * Trusted certificates for verifying the remote endpoint's certificate, {@code null} uses the system default.
      */
     public SslContextBuilder trustManager(X509Certificate... trustCertCollection) {
         this.trustCertCollection = trustCertCollection != null ? trustCertCollection.clone() : null;
         trustManagerFactory = null;
         return this;
     }
 
     /**
      * Trusted certificates for verifying the remote endpoint's certificate, {@code null} uses the system default.
      */
     public SslContextBuilder trustManager(Iterable<? extends X509Certificate> trustCertCollection) {
         return trustManager(toArray(trustCertCollection, EMPTY_X509_CERTIFICATES));
     }
 
     /**
      * Trusted manager for verifying the remote endpoint's certificate. {@code null} uses the system default.
      */
     public SslContextBuilder trustManager(TrustManagerFactory trustManagerFactory) {
         trustCertCollection = null;
         this.trustManagerFactory = trustManagerFactory;
         return this;
     }
 
     /**
      * A single trusted manager for verifying the remote endpoint's certificate.
      * This is helpful when custom implementation of {@link TrustManager} is needed.
      * Internally, a simple wrapper of {@link TrustManagerFactory} that only produces this
      * specified {@link TrustManager} will be created, thus all the requirements specified in
      * {@link #trustManager(TrustManagerFactory trustManagerFactory)} also apply here.
      */
     public SslContextBuilder trustManager(TrustManager trustManager) {
         if (trustManager != null) {
             trustManagerFactory = new TrustManagerFactoryWrapper(trustManager);
         } else {
             trustManagerFactory = null;
         }
         trustCertCollection = null;
         return this;
     }
 
     /**
      * Identifying certificate for this host. {@code keyCertChainFile} and {@code keyFile} may
      * be {@code null} for client contexts, which disables mutual authentication.
      *
      * @param keyCertChainFile an X.509 certificate chain file in PEM format
      * @param keyFile a PKCS#8 private key file in PEM format
      */
     public SslContextBuilder keyManager(File keyCertChainFile, File keyFile) {
         return keyManager(keyCertChainFile, keyFile, null);
     }
 
     /**
      * Identifying certificate for this host. {@code keyCertChainInputStream} and {@code keyInputStream} may
      * be {@code null} for client contexts, which disables mutual authentication.
      *
      * @param keyCertChainInputStream   an input stream for an X.509 certificate chain in PEM format. The caller is
      *                                  responsible for calling {@link InputStream#close()} after {@link #build()}
      *                                  has been called.
      * @param keyInputStream            an input stream for a PKCS#8 private key in PEM format. The caller is
      *                                  responsible for calling {@link InputStream#close()} after {@link #build()}
      *                                  has been called.
      */
     public SslContextBuilder keyManager(InputStream keyCertChainInputStream, InputStream keyInputStream) {
         return keyManager(keyCertChainInputStream, keyInputStream, null);
     }
 
     /**
      * Identifying certificate for this host. {@code keyCertChain} and {@code key} may
      * be {@code null} for client contexts, which disables mutual authentication.
      *
      * @param key a PKCS#8 private key
      * @param keyCertChain an X.509 certificate chain
      */
     public SslContextBuilder keyManager(PrivateKey key, X509Certificate... keyCertChain) {
         return keyManager(key, null, keyCertChain);
     }
 
     /**
      * Identifying certificate for this host. {@code keyCertChain} and {@code key} may
      * be {@code null} for client contexts, which disables mutual authentication.
      *
      * @param key a PKCS#8 private key
      * @param keyCertChain an X.509 certificate chain
      */
     public SslContextBuilder keyManager(PrivateKey key, Iterable<? extends X509Certificate> keyCertChain) {
         return keyManager(key, toArray(keyCertChain, EMPTY_X509_CERTIFICATES));
     }
 
     /**
      * Identifying certificate for this host. {@code keyCertChainFile} and {@code keyFile} may
      * be {@code null} for client contexts, which disables mutual authentication.
      *
      * @param keyCertChainFile an X.509 certificate chain file in PEM format
      * @param keyFile a PKCS#8 private key file in PEM format
      * @param keyPassword the password of the {@code keyFile}, or {@code null} if it's not
      *     password-protected
      */
     public SslContextBuilder keyManager(File keyCertChainFile, File keyFile, String keyPassword) {
         X509Certificate[] keyCertChain;
         PrivateKey key;
         try {
             keyCertChain = SslContext.toX509Certificates(keyCertChainFile);
         } catch (Exception e) {
             throw new IllegalArgumentException("File does not contain valid certificates: " + keyCertChainFile, e);
         }
         try {
             key = SslContext.toPrivateKey(keyFile, keyPassword);
         } catch (Exception e) {
             throw new IllegalArgumentException("File does not contain valid private key: " + keyFile, e);
         }
         return keyManager(key, keyPassword, keyCertChain);
     }
 
     /**
      * Identifying certificate for this host. {@code keyCertChainInputStream} and {@code keyInputStream} may
      * be {@code null} for client contexts, which disables mutual authentication.
      *
      * @param keyCertChainInputStream   an input stream for an X.509 certificate chain in PEM format. The caller is
      *                                  responsible for calling {@link InputStream#close()} after {@link #build()}
      *                                  has been called.
      * @param keyInputStream            an input stream for a PKCS#8 private key in PEM format. The caller is
      *                                  responsible for calling {@link InputStream#close()} after {@link #build()}
      *                                  has been called.
      * @param keyPassword the password of the {@code keyInputStream}, or {@code null} if it's not
      *     password-protected
      */
     public SslContextBuilder keyManager(InputStream keyCertChainInputStream, InputStream keyInputStream,
             String keyPassword) {
         X509Certificate[] keyCertChain;
         PrivateKey key;
         try {
             keyCertChain = SslContext.toX509Certificates(keyCertChainInputStream);
         } catch (Exception e) {
             throw new IllegalArgumentException("Input stream not contain valid certificates.", e);
         }
         try {
             key = SslContext.toPrivateKey(keyInputStream, keyPassword);
         } catch (Exception e) {
             throw new IllegalArgumentException("Input stream does not contain valid private key.", e);
         }
         return keyManager(key, keyPassword, keyCertChain);
     }
 
     /**
      * Identifying certificate for this host. {@code keyCertChain} and {@code key} may
      * be {@code null} for client contexts, which disables mutual authentication.
      *
      * @param key a PKCS#8 private key file
      * @param keyPassword the password of the {@code key}, or {@code null} if it's not
      *     password-protected
      * @param keyCertChain an X.509 certificate chain
      */
     public SslContextBuilder keyManager(PrivateKey key, String keyPassword, X509Certificate... keyCertChain) {
         if (forServer) {
             checkNonEmpty(keyCertChain, "keyCertChain");
             checkNotNull(key, "key required for servers");
         }
         if (keyCertChain == null || keyCertChain.length == 0) {
             this.keyCertChain = null;
         } else {
             for (X509Certificate cert: keyCertChain) {
                 checkNotNullWithIAE(cert, "cert");
             }
             this.keyCertChain = keyCertChain.clone();
         }
         this.key = key;
         this.keyPassword = keyPassword;
         keyManagerFactory = null;
         return this;
     }
 
     /**
      * Identifying certificate for this host. {@code keyCertChain} and {@code key} may
      * be {@code null} for client contexts, which disables mutual authentication.
      *
      * @param key a PKCS#8 private key file
      * @param keyPassword the password of the {@code key}, or {@code null} if it's not
      *     password-protected
      * @param keyCertChain an X.509 certificate chain
      */
     public SslContextBuilder keyManager(PrivateKey key, String keyPassword,
                                         Iterable<? extends X509Certificate> keyCertChain) {
         return keyManager(key, keyPassword, toArray(keyCertChain, EMPTY_X509_CERTIFICATES));
     }
 
     /**
      * Identifying manager for this host. {@code keyManagerFactory} may be {@code null} for
      * client contexts, which disables mutual authentication. Using a {@link KeyManagerFactory}
      * is only supported for {@link SslProvider#JDK} or {@link SslProvider#OPENSSL} / {@link SslProvider#OPENSSL_REFCNT}
      * if the used openssl version is 1.0.1+. You can check if your openssl version supports using a
      * {@link KeyManagerFactory} by calling {@link OpenSsl#supportsKeyManagerFactory()}. If this is not the case
      * you must use {@link #keyManager(File, File)} or {@link #keyManager(File, File, String)}.
      * <p>
      * If you use {@link SslProvider#OPENSSL} or {@link SslProvider#OPENSSL_REFCNT} consider using
      * {@link OpenSslX509KeyManagerFactory} or {@link OpenSslCachingX509KeyManagerFactory}.
      */
     public SslContextBuilder keyManager(KeyManagerFactory keyManagerFactory) {
         if (forServer) {
             checkNotNull(keyManagerFactory, "keyManagerFactory required for servers");
         }
         keyCertChain = null;
         key = null;
         keyPassword = null;
         this.keyManagerFactory = keyManagerFactory;
         return this;
     }
 
     /**
      * A single key manager managing the identity information of this host.
      * This is helpful when custom implementation of {@link KeyManager} is needed.
      * Internally, a wrapper of {@link KeyManagerFactory} that only produces this specified
      * {@link KeyManager} will be created, thus all the requirements specified in
      * {@link #keyManager(KeyManagerFactory keyManagerFactory)} also apply here.
      */
     public SslContextBuilder keyManager(KeyManager keyManager) {
         if (forServer) {
             checkNotNull(keyManager, "keyManager required for servers");
         }
         if (keyManager != null) {
             keyManagerFactory = new KeyManagerFactoryWrapper(keyManager);
         } else {
             keyManagerFactory = null;
         }
         keyCertChain = null;
         key = null;
         keyPassword = null;
         return this;
     }
 
     /**
      * The cipher suites to enable, in the order of preference. {@code null} to use default
      * cipher suites.
      */
     public SslContextBuilder ciphers(Iterable<String> ciphers) {
         return ciphers(ciphers, IdentityCipherSuiteFilter.INSTANCE);
     }
 
     /**
      * The cipher suites to enable, in the order of preference. {@code cipherFilter} will be
      * applied to the ciphers before use. If {@code ciphers} is {@code null}, then the default
      * cipher suites will be used.
      */
     public SslContextBuilder ciphers(Iterable<String> ciphers, CipherSuiteFilter cipherFilter) {
         this.cipherFilter = checkNotNull(cipherFilter, "cipherFilter");
         this.ciphers = ciphers;
         return this;
     }
 
     /**
      * Application protocol negotiation configuration. {@code null} disables support.
      */
     public SslContextBuilder applicationProtocolConfig(ApplicationProtocolConfig apn) {
         this.apn = apn;
         return this;
     }
 
     /**
      * Set the size of the cache used for storing SSL session objects. {@code 0} to use the
      * default value.
      */
     public SslContextBuilder sessionCacheSize(long sessionCacheSize) {
         this.sessionCacheSize = sessionCacheSize;
         return this;
     }
 
     /**
      * Set the timeout for the cached SSL session objects, in seconds. {@code 0} to use the
      * default value.
      */
     public SslContextBuilder sessionTimeout(long sessionTimeout) {
         this.sessionTimeout = sessionTimeout;
         return this;
     }
 
     /**
      * Sets the client authentication mode.
      */
     public SslContextBuilder clientAuth(ClientAuth clientAuth) {
         this.clientAuth = checkNotNull(clientAuth, "clientAuth");
         return this;
     }
 
     /**
      * The TLS protocol versions to enable.
      * @param protocols The protocols to enable, or {@code null} to enable the default protocols.
      * @see SSLEngine#setEnabledCipherSuites(String[])
      */
     public SslContextBuilder protocols(String... protocols) {
         this.protocols = protocols == null ? null : protocols.clone();
         return this;
     }
 
     /**
      * The TLS protocol versions to enable.
      * @param protocols The protocols to enable, or {@code null} to enable the default protocols.
      * @see SSLEngine#setEnabledCipherSuites(String[])
      */
     public SslContextBuilder protocols(Iterable<String> protocols) {
         return protocols(toArray(protocols, EMPTY_STRINGS));
     }
 
     /**
      * {@code true} if the first write request shouldn't be encrypted.
      */
     public SslContextBuilder startTls(boolean startTls) {
         this.startTls = startTls;
         return this;
     }
 
     /**
      * Enables OCSP stapling. Please note that not all {@link SslProvider} implementations support OCSP
      * stapling and an exception will be thrown upon {@link #build()}.
      *
      * @see OpenSsl#isOcspSupported()
      */
     @UnstableApi
     public SslContextBuilder enableOcsp(boolean enableOcsp) {
         this.enableOcsp = enableOcsp;
         return this;
     }
 
     /**
      * Specify a non-default source of randomness for the {@link JdkSslContext}
      * <p>
      * In general, the best practice is to leave this unspecified, or to assign a new random source using the
      * default {@code new SecureRandom()} constructor.
      * Only assign this something when you have a good reason to.
      *
      * @param secureRandom the source of randomness for {@link JdkSslContext}
      *
      */
     public SslContextBuilder secureRandom(SecureRandom secureRandom) {
         this.secureRandom = secureRandom;
         return this;
     }
 
     /**
      * Specify the endpoint identification algorithm (aka. hostname verification algorithm) that clients will use as
      * part of authenticating servers.
      * <p>
      * See <a href="https://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html#jssenames">
      *     Java Security Standard Names</a> for a list of supported algorithms.
      *
      * @param algorithm either {@code "HTTPS"}, {@code "LDAPS"}, or {@code null} (disables hostname verification).
      * @see SSLParameters#setEndpointIdentificationAlgorithm(String)
      */
     public SslContextBuilder endpointIdentificationAlgorithm(String algorithm) {
         endpointIdentificationAlgorithm = algorithm;
         return this;
     }
 
     /**
      * Add the given server name indication to this client context. This will cause the client to include a
      * Server Name Indication extension with its {@code ClientHello} message, as per
      * <a href="https://datatracker.ietf.org/doc/html/rfc6066#section-3">RFC 6066 section 3</a>.
      * <p>
      * Note that only one name per name type can be included in the message.
      * Currently, only the {@link SNIHostName} type is supported.
      * @param serverName The server name to include in the SNI extension.
      */
     public SslContextBuilder serverName(SNIServerName serverName) {
         if (forServer) {
             throw new UnsupportedOperationException("Cannot add Server Name Indication extension, " +
                     "because this is a server context builder.");
         }
         checkNotNull(serverName, "serverName");
         if (!(serverName instanceof SNIHostName)) {
             throw new IllegalArgumentException("Only SNIHostName is supported. The given SNIServerName type was " +
                     serverName.getClass().getName());
         }
         serverNames.add(serverName);
         return this;
     }
 
     /**
      * Create new {@code SslContext} instance with configured settings.
      * <p>If {@link #sslProvider(SslProvider)} is set to {@link SslProvider#OPENSSL_REFCNT} then the caller is
      * responsible for releasing this object, or else native memory may leak.
      */
     public SslContext build() throws SSLException {
         if (forServer) {
             return SslContext.newServerContextInternal(provider, sslContextProvider, trustCertCollection,
                 trustManagerFactory, keyCertChain, key, keyPassword, keyManagerFactory,
                 ciphers, cipherFilter, apn, sessionCacheSize, sessionTimeout, clientAuth, protocols, startTls,
                 enableOcsp, secureRandom, keyStoreType, toArray(options.entrySet(), EMPTY_ENTRIES));
         } else {
             return SslContext.newClientContextInternal(provider, sslContextProvider, trustCertCollection,
                 trustManagerFactory, keyCertChain, key, keyPassword, keyManagerFactory,
                 ciphers, cipherFilter, apn, protocols, sessionCacheSize,
                     sessionTimeout, enableOcsp, secureRandom, keyStoreType, endpointIdentificationAlgorithm,
                     serverNames, toArray(options.entrySet(), EMPTY_ENTRIES));
         }
     }
 
     private static <T> T[] toArray(Iterable<? extends T> iterable, T[] prototype) {
         if (iterable == null) {
             return null;
         }
         final List<T> list = new ArrayList<T>();
         for (T element : iterable) {
             list.add(element);
         }
         return list.toArray(prototype);
     }
 }