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/*   
 *  Copyright 1999-2004 The Apache Sofware Foundation.
 *
 *  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 org.apache.tomcat.modules.session;

import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Random;

import org.apache.tomcat.core.BaseInterceptor;
import org.apache.tomcat.core.ContextManager;
import org.apache.tomcat.core.Request;
import org.apache.tomcat.core.ServerSession;
import org.apache.tomcat.core.TomcatException;
import org.apache.tomcat.util.compat.Action;
import org.apache.tomcat.util.compat.Jdk11Compat;


/**
 * Generate session IDs. Will use a random generator and the
 * load balancing route.
 *
 * This class generates a unique 10+ character id. This is good
 * for authenticating users or tracking users around.
 * 

* This code was borrowed from Apache JServ.JServServletManager.java. * It is what Apache JServ uses to generate session ids for users. * Unfortunately, it was not included in Apache JServ as a class * so I had to create one here in order to use it. * * @author costin@eng.sun.com * @author hans@gefionsoftware.com * @author pfrieden@dChain.com * @author Shai Fultheim [shai@brm.com] * @author James Duncan Davidson [duncan@eng.sun.com] * @author Jason Hunter [jhunter@acm.org] * @author Jon S. Stevens jon@latchkey.com */ public final class SessionIdGenerator extends BaseInterceptor { String randomClassName=null; Random randomSource=null; DataInputStream randomIS=null; String devRandomSource="/dev/urandom"; static Jdk11Compat jdk11Compat=Jdk11Compat.getJdkCompat(); public SessionIdGenerator() { } // -------------------- Configuration properties -------------------- public final void setRandomClass(String randomClass) { this.randomClassName=randomClass; } /** Use /dev/random-type special device. This is new code, but may reduce the * big delay in generating the random. * * You must specify a path to a random generator file. Use /dev/urandom * for linux ( or similar ) systems. Use /dev/random for maximum security * ( it may block if not enough "random" exist ). You can also use * a pipe that generates random. * * The code will check if the file exists, and default to java Random * if not found. There is a significant performance difference, very * visible on the first call to getSession ( like in the first JSP ) * - so use it if available. */ public void setRandomFile( String s ) { // as a hack, you can use a static file - and genarate the same // session ids ( good for strange debugging ) try { devRandomSource=s; File f=new File( devRandomSource ); if( ! f.exists() ) return; randomIS= new DataInputStream( new FileInputStream(f)); randomIS.readLong(); log( "Opening " + devRandomSource ); } catch( IOException ex ) { randomIS=null; } } // -------------------- Tomcat request events -------------------- public int sessionState( Request req, ServerSession sess, int state ) { if( state==ServerSession.STATE_NEW ) { String jsIdent=req.getJvmRoute(); String newId=createNewId( jsIdent ); if(debug>0) log("Generate new session id " + newId ); sess.getId().setString( newId ); } return state; } //-------------------- Tomcat context events -------------------- private Object accessControlContext=null; /** Init session management stuff for this context. */ public void engineInit(ContextManager cm) throws TomcatException { try { accessControlContext=jdk11Compat.getAccessControlContext(); } catch(Exception ex) { ex.printStackTrace();// shouldn't happen } } // -------------------- Internal methods -------------------- String createNewId(String jsIdent) { /** * When using a SecurityManager and a JSP page or servlet triggers * creation of a new session id it must be performed with the * Permissions of this class using doPriviledged because the parent * JSP or servlet may not have sufficient Permissions. */ String newId; if( System.getSecurityManager() == null ) { newId= getIdentifier(jsIdent); return newId; } // We're in a sandbox... PriviledgedIdGenerator di = new PriviledgedIdGenerator(this, jsIdent); try { newId= (String)jdk11Compat.doPrivileged(di, accessControlContext); } catch( Exception ex ) { newId=null; } return newId; } // Sandbox support static class PriviledgedIdGenerator extends Action { SessionIdGenerator sg; String jsIdent; public PriviledgedIdGenerator(SessionIdGenerator sg, String jsIdent ) { this.sg=sg; this.jsIdent=jsIdent; } public Object run() { return sg.getIdentifier(jsIdent); } } /** Create the random generator using the configured class name, and * defaulting to java.security.SecureRandom */ private void createRandomClass() { if( randomClassName==null ) { // backward compatibility randomClassName=(String)cm.getProperty("randomClass" ); // set a reasonable default if( randomClassName==null ) { randomClassName="java.security.SecureRandom"; } } try { Class randomClass = Class.forName(randomClassName); randomSource = (java.util.Random)randomClass.newInstance(); } catch (Exception e) { log("SessionIdGenerator.createRandomClass", e); } if (randomSource == null) randomSource = new java.security.SecureRandom(); log( "Created random class " + randomSource.getClass().getName()); } /* * Create a suitable string for session identification * Use synchronized count and time to ensure uniqueness. * Use random string to ensure timestamp cannot be guessed * by programmed attack. * * format of id is <6 chars random><3 chars time><1+ char count> */ static private int session_count = 0; static private long lastTimeVal = 0; // MAX_RADIX is 36 /* * we want to have a random string with a length of * 6 characters. Since we encode it BASE 36, we've to * modulo it with the following value: */ public final static long maxRandomLen = 2176782336L; // 36 ** 6 /* * The session identifier must be unique within the typical lifespan * of a Session, the value can roll over after that. 3 characters: * (this means a roll over after over an day which is much larger * than a typical lifespan) */ public final static long maxSessionLifespanTics = 46656; // 36 ** 3 /* * millisecons between different tics. So this means that the * 3-character time string has a new value every 2 seconds: */ public final static long ticDifference = 2000; // ** NOTE that this must work together with get_jserv_session_balance() // ** in jserv_balance.c public synchronized String getIdentifier(String jsIdent) { StringBuffer sessionId = new StringBuffer(); // random value .. long n = 0; if( randomIS!=null ) { try { n=randomIS.readLong(); //System.out.println("Getting /dev/random " + n ); } catch( IOException ex ) { ex.printStackTrace(); randomIS=null; // We could also re-open it ( if it's a file of random values ) } } if( randomIS==null ) { if (randomSource==null ) createRandomClass(); n=randomSource.nextLong(); } if (n < 0) n = -n; n %= maxRandomLen; // add maxLen to pad the leading characters with '0'; remove // first digit with substring. n += maxRandomLen; sessionId.append (Long.toString(n, Character.MAX_RADIX) .substring(1)); long timeVal = (System.currentTimeMillis() / ticDifference); // cut.. timeVal %= maxSessionLifespanTics; // padding, see above timeVal += maxSessionLifespanTics; sessionId.append (Long.toString (timeVal, Character.MAX_RADIX) .substring(1)); /* * make the string unique: append the session count since last * time flip. */ // count sessions only within tics. So the 'real' session count // isn't exposed to the public .. if (lastTimeVal != timeVal) { lastTimeVal = timeVal; session_count = 0; } sessionId.append (Long.toString (++session_count, Character.MAX_RADIX)); if (jsIdent != null && jsIdent.length() > 0) { return sessionId.toString()+"."+jsIdent; } return sessionId.toString(); } }



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