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   /*
    * Copyright 2018 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 java.util.Locale;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  /**
   * Converts OpenSSL signature Algorithm names to
   * <a href="https://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html#Signature">
   *     Java signature Algorithm names</a>.
   */
  final class SignatureAlgorithmConverter {
  
      private SignatureAlgorithmConverter() { }
  
      // OpenSSL has 3 different formats it uses at the moment we will match against all of these.
      // For example:
      //              ecdsa-with-SHA384
      //              hmacWithSHA384
      //              dsa_with_SHA224
      //
      // For more details see https://github.com/openssl/openssl/blob/OpenSSL_1_0_2p/crypto/objects/obj_dat.h
      //
      // BoringSSL uses a different format:
      // https://github.com/google/boringssl/blob/8525ff3/ssl/ssl_privkey.cc#L436
      //
      private static final Pattern PATTERN = Pattern.compile(
              // group 1 - 2
              "(?:(^[a-zA-Z].+)With(.+)Encryption$)|" +
              // group 3 - 4
              "(?:(^[a-zA-Z].+)(?:_with_|-with-|_pkcs1_|_pss_rsae_)(.+$))|" +
              // group 5 - 6
              "(?:(^[a-zA-Z].+)_(.+$))");
  
      /**
       * Converts an OpenSSL algorithm name to a Java algorithm name and return it,
       * or return {@code null} if the conversation failed because the format is not known.
       */
      static String toJavaName(String opensslName) {
          if (opensslName == null) {
              return null;
          }
          Matcher matcher = PATTERN.matcher(opensslName);
          if (matcher.matches()) {
              String group1 = matcher.group(1);
              if (group1 != null) {
                  return group1.toUpperCase(Locale.ROOT) + "with" + matcher.group(2).toUpperCase(Locale.ROOT);
              }
              if (matcher.group(3) != null) {
                  return matcher.group(4).toUpperCase(Locale.ROOT) + "with" + matcher.group(3).toUpperCase(Locale.ROOT);
              }
  
              if (matcher.group(5) != null) {
                  return matcher.group(6).toUpperCase(Locale.ROOT) + "with" + matcher.group(5).toUpperCase(Locale.ROOT);
              }
          }
          return null;
      }
  }