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Nuts'n'Bolts Utilities

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/*
 * Copyright (c) 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020 David Berkman
 *
 * This file is part of the SmallMind Code Project.
 *
 * The SmallMind Code Project is free software, you can redistribute
 * it and/or modify it under either, at your discretion...
 *
 * 1) The terms of GNU Affero General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at
 * your option) any later version.
 *
 * ...or...
 *
 * 2) The terms of the Apache License, Version 2.0.
 *
 * The SmallMind Code Project 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 or Apache License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * and the Apache License along with the SmallMind Code Project. If not, see
 *  or .
 *
 * Additional permission under the GNU Affero GPL version 3 section 7
 * ------------------------------------------------------------------
 * If you modify this Program, or any covered work, by linking or
 * combining it with other code, such other code is not for that reason
 * alone subject to any of the requirements of the GNU Affero GPL
 * version 3.
 */
package org.smallmind.nutsnbolts.security.key;

import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.nio.charset.StandardCharsets;
import org.smallmind.nutsnbolts.http.Base64Codec;

public class PKCS8KeyReader implements KeyReader {

  private final KeyFactors keyFactors;

  public PKCS8KeyReader (String raw)
    throws IOException, KeyParseException {

    try (DataInputStream dataInputStream = new DataInputStream(new ByteArrayInputStream(Base64Codec.decode(raw)))) {

      if (!"ssh-rsa".equals(new String(readBytes(dataInputStream), StandardCharsets.UTF_8))) {
        throw new KeyParseException("Missing RFC-416 'ssh-rsa' prologue");
      }

      byte[] exponentBytes = readBytes(dataInputStream);
      byte[] modulusBytes = readBytes(dataInputStream);

      keyFactors = new KeyFactors(new BigInteger(modulusBytes), new BigInteger(exponentBytes));
    }
  }

  @Override
  public KeyFactors extractFactors () {

    return keyFactors;
  }

  private byte[] readBytes (DataInputStream dataInputStream)
    throws IOException {

    byte[] bytes = new byte[dataInputStream.readInt()];

    dataInputStream.readFully(bytes);

    return bytes;
  }
}