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**vngx-jsch** (beta) is an updated version of the popular JSch SSH library
written in pure Java. It has been updated to Java 6 with all the latest
language features and improved code clarity.
/*
* Copyright (c) 2002-2010 Atsuhiko Yamanaka, JCraft,Inc. All rights reserved.
* Copyright (c) 2010-2011 Michael Laudati, N1 Concepts LLC.
*
* 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 org.vngx.jsch.userauth;
import org.vngx.jsch.exception.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;
/**
* Implementation of com.jcraft.jsch.GSSContext to perform user
* authentication.
*
* @see org.vngx.jsch.GSSContext
*
* @author Atsuhiko Yamanaka
* @author Michael Laudati
*/
public final class GSSContextKrb5 implements org.vngx.jsch.userauth.GSSContext {
/** Constant for System property to use subject credentials only. */
private static final String USE_SUBJECT_CREDS_ONLY = "javax.security.auth.useSubjectCredsOnly";
/** Property value to use subject credentials only. */
private static String $useSubjectCredsOnly = getSystemProperty(USE_SUBJECT_CREDS_ONLY);
/** Generic security services context. */
private GSSContext _context;
@Override
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) {
// TODO Error handling?
}
GSSName gssHost = mgr.createName("host/" + cname, principalName);
_context = mgr.createContext(gssHost, 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 accept '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);
} catch(GSSException ex) {
throw new JSchException("Failed to create GSSContextKrb5: "+ex, ex);
}
}
@Override
public boolean isEstablished() {
return _context.isEstablished();
}
@Override
public byte[] init(byte[] token, int offset, int length) throws JSchException {
try {
// Without setting "javax.security.auth.useSubjectCredsOnly" to "false",
// Sun'offset 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(USE_SUBJECT_CREDS_ONLY, "false");
}
return _context.initSecContext(token, 0, length);
} catch(GSSException ex) {
throw new JSchException("Failed to init GSSContextKrb5: "+ex, ex);
} catch(SecurityException ex) {
throw new JSchException("Failed to init GSSContextKrb5: "+ex, ex);
} finally {
if( $useSubjectCredsOnly == null ) {
// By default, it must be "true".
setSystemProperty(USE_SUBJECT_CREDS_ONLY, "true");
}
}
}
@Override
public byte[] getMIC(byte[] message, int offset, int length) {
try {
return _context.getMIC(message, offset, length, new MessageProp(0, true));
} catch(GSSException ex) {
return null;
}
}
@Override
public void dispose() {
try {
_context.dispose();
} catch(GSSException ex) {
// TODO Error handling?
}
}
/**
* Utility method for retrieving a property value from System properties.
*
* @param key
* @return property value or null if error occurs
*/
private static String getSystemProperty(String key) {
try {
return System.getProperty(key);
} catch(SecurityException e) {
return null; // Not allowed to get the System properties
}
}
/**
* Utility method for setting a property value in System properties.
*
* @param key
* @param value
*/
private static void setSystemProperty(String key, String value) {
try {
System.setProperty(key, value);
} catch(SecurityException e) { /* Not allowed to set the System properties */ }
}
}