/*
 * Copyright (c) 2006-2018 ymnk, JCraft,Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted
 * provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this list of conditions
 * and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
 * conditions and the following disclaimer in the documentation and/or other materials provided with
 * the distribution.
 *
 * 3. The names of the authors may not be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL JCRAFT, INC. OR ANY CONTRIBUTORS TO THIS SOFTWARE BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES(INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION)HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT(INCLUDING NEGLIGENCE OR OTHERWISE)ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package com.jcraft.jsch;

class UserAuthGSSAPIWithMIC extends UserAuth {
  private static final int SSH_MSG_USERAUTH_GSSAPI_RESPONSE = 60;
  private static final int SSH_MSG_USERAUTH_GSSAPI_TOKEN = 61;
  private static final int SSH_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE = 63;
  private static final int SSH_MSG_USERAUTH_GSSAPI_ERROR = 64;
  private static final int SSH_MSG_USERAUTH_GSSAPI_ERRTOK = 65;
  private static final int SSH_MSG_USERAUTH_GSSAPI_MIC = 66;

  private static final byte[][] supported_oid = {
      // OID 1.2.840.113554.1.2.2 in DER
      {(byte) 0x6, (byte) 0x9, (byte) 0x2a, (byte) 0x86, (byte) 0x48, (byte) 0x86, (byte) 0xf7,
          (byte) 0x12, (byte) 0x1, (byte) 0x2, (byte) 0x2}};

  private static final String[] supported_method = {"gssapi-with-mic.krb5"};

  @Override
  public boolean start(Session session) throws Exception {
    super.start(session);

    byte[] _username = Util.str2byte(username);

    packet.reset();

    // byte       SSH_MSG_USERAUTH_REQUEST(50)
    // string     user name(in ISO-10646 UTF-8 encoding)
    // string     service name(in US-ASCII)
    // string     "gssapi"(US-ASCII)
    // uint32     n, the number of OIDs client supports
    // string[n]  mechanism OIDS
    buf.putByte((byte) SSH_MSG_USERAUTH_REQUEST);
    buf.putString(_username);
    buf.putString(Util.str2byte("ssh-connection"));
    buf.putString(Util.str2byte("gssapi-with-mic"));
    buf.putInt(supported_oid.length);
    for (int i = 0; i < supported_oid.length; i++) {
      buf.putString(supported_oid[i]);
    }
    session.write(packet);

    String method = null;
    int command;
    while (true) {
      buf = session.read(buf);
      command = buf.getCommand() & 0xff;

      if (command == SSH_MSG_USERAUTH_FAILURE) {
        return false;
      }

      if (command == SSH_MSG_USERAUTH_GSSAPI_RESPONSE) {
        buf.getInt();
        buf.getByte();
        buf.getByte();
        byte[] message = buf.getString();

        for (int i = 0; i < supported_oid.length; i++) {
          if (Util.array_equals(message, supported_oid[i])) {
            method = supported_method[i];
            break;
          }
        }

        if (method == null) {
          return false;
        }

        break; // success
      }

      if (command == SSH_MSG_USERAUTH_BANNER) {
        buf.getInt();
        buf.getByte();
        buf.getByte();
        byte[] _message = buf.getString();
        byte[] lang = buf.getString();
        String message = Util.byte2str(_message);
        if (userinfo != null) {
          userinfo.showMessage(message);
        }
        continue;
      }
      return false;
    }

    GSSContext context = null;
    try {
      Class<? extends GSSContext> c =
          Class.forName(session.getConfig(method)).asSubclass(GSSContext.class);
      context = c.getDeclaredConstructor().newInstance();
    } catch (Exception e) {
      return false;
    }

    try {
      context.create(username, session.host);
    } catch (JSchException e) {
      return false;
    }

    byte[] token = new byte[0];

    while (!context.isEstablished()) {
      try {
        token = context.init(token, 0, token.length);
      } catch (JSchException e) {
        // TODO
        // ERRTOK should be sent?
        // byte    SSH_MSG_USERAUTH_GSSAPI_ERRTOK
        // string  error token
        return false;
      }

      if (token != null) {
        packet.reset();
        buf.putByte((byte) SSH_MSG_USERAUTH_GSSAPI_TOKEN);
        buf.putString(token);
        session.write(packet);
      }

      if (!context.isEstablished()) {
        buf = session.read(buf);
        command = buf.getCommand() & 0xff;
        if (command == SSH_MSG_USERAUTH_GSSAPI_ERROR) {
          // uint32  major_status
          // uint32  minor_status
          // string  message
          // string  language tag

          buf = session.read(buf);
          command = buf.getCommand() & 0xff;
          // return false;
        } else if (command == SSH_MSG_USERAUTH_GSSAPI_ERRTOK) {
          // string error token

          buf = session.read(buf);
          command = buf.getCommand() & 0xff;
          // return false;
        }

        if (command == SSH_MSG_USERAUTH_FAILURE) {
          return false;
        }

        buf.getInt();
        buf.getByte();
        buf.getByte();
        token = buf.getString();
      }
    }

    Buffer mbuf = new Buffer();
    // string  session identifier
    // byte    SSH_MSG_USERAUTH_REQUEST
    // string  user name
    // string  service
    // string  "gssapi-with-mic"
    mbuf.putString(session.getSessionId());
    mbuf.putByte((byte) SSH_MSG_USERAUTH_REQUEST);
    mbuf.putString(_username);
    mbuf.putString(Util.str2byte("ssh-connection"));
    mbuf.putString(Util.str2byte("gssapi-with-mic"));

    byte[] mic = context.getMIC(mbuf.buffer, 0, mbuf.getLength());

    if (mic == null) {
      return false;
    }

    packet.reset();
    buf.putByte((byte) SSH_MSG_USERAUTH_GSSAPI_MIC);
    buf.putString(mic);
    session.write(packet);

    context.dispose();

    buf = session.read(buf);
    command = buf.getCommand() & 0xff;

    if (command == SSH_MSG_USERAUTH_SUCCESS) {
      return true;
    } else if (command == SSH_MSG_USERAUTH_FAILURE) {
      buf.getInt();
      buf.getByte();
      buf.getByte();
      byte[] foo = buf.getString();
      int partial_success = buf.getByte();
      // System.err.println(new String(foo) +
      //                    " partial_success:" + (partial_success != 0));
      if (partial_success != 0) {
        throw new JSchPartialAuthException(Util.byte2str(foo));
      }
    }
    return false;
  }
}
