content: /*
   * Copyright 2018 The Android Open Source Project
   *
   * 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 android.security.keystore.recovery;
  
  import java.io.ByteArrayInputStream;
  import java.io.InputStream;
  import java.security.cert.CertificateException;
  import java.security.cert.CertificateFactory;
  import java.security.cert.X509Certificate;
  import java.util.Base64;
  
  /**
   * Static helper methods for decoding {@link X509Certificate} instances.
   *
   * @hide
   */
  public class X509CertificateParsingUtils {
      private static final String CERT_FORMAT = "X.509";
  
      /**
       * Decodes an {@link X509Certificate} encoded as a base-64 string.
       */
      public static X509Certificate decodeBase64Cert(String string) throws CertificateException {
          try {
              return decodeCert(decodeBase64(string));
          } catch (IllegalArgumentException e) {
              throw new CertificateException(e);
          }
      }
  
      /**
       * Decodes a base-64 string.
       *
       * @throws IllegalArgumentException if not a valid base-64 string.
       */
      private static byte[] decodeBase64(String string) {
          return Base64.getDecoder().decode(string);
      }
  
      /**
       * Decodes a byte array containing an encoded X509 certificate.
       *
       * @param certBytes the byte array containing the encoded X509 certificate
       * @return the decoded X509 certificate
       * @throws CertificateException if any parsing error occurs
       */
      private static X509Certificate decodeCert(byte[] certBytes) throws CertificateException {
          return decodeCert(new ByteArrayInputStream(certBytes));
      }
  
      /**
       * Decodes an X509 certificate from an {@code InputStream}.
       *
       * @param inStream the input stream containing the encoded X509 certificate
       * @return the decoded X509 certificate
       * @throws CertificateException if any parsing error occurs
       */
      private static X509Certificate decodeCert(InputStream inStream) throws CertificateException {
          CertificateFactory certFactory;
          try {
              certFactory = CertificateFactory.getInstance(CERT_FORMAT);
          } catch (CertificateException e) {
              // Should not happen, as X.509 is mandatory for all providers.
              throw new RuntimeException(e);
          }
          return (X509Certificate) certFactory.generateCertificate(inStream);
      }
  }
  