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/* -*-mode:java; c-basic-offset:2; indent-tabs-mode:nil -*- */
/*
Copyright (c) 2006-2009 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 
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     derived from this software without specific prior written permission.

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INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JCRAFT,
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package com.jcraft.jsch.jgss;

import com.jcraft.jsch.JSchException;

import java.net.InetAddress;
import java.net.UnknownHostException;
import org.ietf.jgss.GSSContext;
import org.ietf.jgss.GSSCredential;
import org.ietf.jgss.GSSException;
import org.ietf.jgss.GSSManager;
import org.ietf.jgss.GSSName;
import org.ietf.jgss.MessageProp;
import org.ietf.jgss.Oid;

public class GSSContextKrb5 implements com.jcraft.jsch.GSSContext{

  private static final String pUseSubjectCredsOnly = 
    "javax.security.auth.useSubjectCredsOnly";
  private static String useSubjectCredsOnly = 
    getSystemProperty(pUseSubjectCredsOnly);

  private GSSContext context=null;
  public void create(String user, String host) throws JSchException{
    try{
      // RFC 1964
      Oid krb5=new Oid("1.2.840.113554.1.2.2");
      // Kerberos Principal Name Form
      Oid principalName=new Oid("1.2.840.113554.1.2.2.1");

      GSSManager mgr=GSSManager.getInstance();

      GSSCredential crd=null;
      /*
      try{
        GSSName _user=mgr.createName(user, principalName);
        crd=mgr.createCredential(_user,
                                 GSSCredential.DEFAULT_LIFETIME,
                                 krb5,
                                 GSSCredential.INITIATE_ONLY);
      }
      catch(GSSException crdex){
      }
      */

      String cname=host;
      try{
        cname=InetAddress.getByName(cname).getCanonicalHostName();
      }
      catch(UnknownHostException e){
      }
      GSSName _host=mgr.createName("host/"+cname, principalName);

      context=mgr.createContext(_host,
                                krb5,
                                crd,
                                GSSContext.DEFAULT_LIFETIME);

      // RFC4462  3.4.  GSS-API Session
      //
      // When calling GSS_Init_sec_context(), the client MUST set
      // integ_req_flag to "true" to request that per-message integrity
      // protection be supported for this context.  In addition,
      // deleg_req_flag MAY be set to "true" to request access delegation, if
      // requested by the user.
      //
      // Since the user authentication process by its nature authenticates
      // only the client, the setting of mutual_req_flag is not needed for
      // this process.  This flag SHOULD be set to "false".

      // TODO: OpenSSH's sshd does accepts 'false' for mutual_req_flag
      //context.requestMutualAuth(false);
      context.requestMutualAuth(true);
      context.requestConf(true);
      context.requestInteg(true);             // for MIC
      context.requestCredDeleg(true);
      context.requestAnonymity(false);

      return;
    }
    catch(GSSException ex){
      throw new JSchException(ex.toString());
    }
  }

  public boolean isEstablished(){
    return context.isEstablished();
  }

  public byte[] init(byte[] token, int s, int l) throws JSchException {
    try{
      // Without setting "javax.security.auth.useSubjectCredsOnly" to "false",
      // Sun's JVM for Un*x will show messages to stderr in
      // processing context.initSecContext().
      // This hack is not thread safe ;-<.
      // If that property is explicitly given as "true" or "false",
      // this hack must not be invoked.
      if(useSubjectCredsOnly==null){
        setSystemProperty(pUseSubjectCredsOnly, "false");
      }
      return context.initSecContext(token, 0, l);
    }
    catch(GSSException ex){
      throw new JSchException(ex.toString());
    }
    catch(java.lang.SecurityException ex){
      throw new JSchException(ex.toString());
    }
    finally{
      if(useSubjectCredsOnly==null){
        // By the default, it must be "true".
        setSystemProperty(pUseSubjectCredsOnly, "true");
      }
    }
  }

  public byte[] getMIC(byte[] message, int s, int l){
    try{
      MessageProp prop =  new MessageProp(0, true);
      return context.getMIC(message, s, l, prop);
    }
    catch(GSSException ex){
      return null;
    }
  }

  public void dispose(){
    try{
      context.dispose();
    }
    catch(GSSException ex){
    }
  }

  private static String getSystemProperty(String key){
    try{ return System.getProperty(key); }
    catch(Exception e){ 
      // We are not allowed to get the System properties.
      return null; 
    } 
  }

  private static void setSystemProperty(String key, String value){
    try{ System.setProperty(key, value); }
    catch(Exception e){ 
      // We are not allowed to set the System properties.
    }
  }
}
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