classloader.java

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            final int i = name.lastIndexOf('.');
	    if (i != -1) {
                AccessController.doPrivileged(new PrivilegedAction() {
                    public Object run() {
		        sm.checkPackageAccess(name.substring(0, i));
		        return null;
                    }
                }, new AccessControlContext(new ProtectionDomain[] {pd}));
	    }
	}
	domains.add(pd);
    }

    /**
     * Finds the specified class.  This method should be overridden by class
     * loader implementations that follow the delegation model for loading
     * classes, and will be invoked by the {@link #loadClass
     * <tt>loadClass</tt>} method after checking the parent class loader for
     * the requested class.  The default implementation throws a
     * <tt>ClassNotFoundException</tt>.  </p>
     *
     * @param  name
     *         The name of the class
     *
     * @return  The resulting <tt>Class</tt> object
     *
     * @throws  ClassNotFoundException
     *          If the class could not be found
     *
     * @since  1.2
     */
    protected Class findClass(String name) throws ClassNotFoundException {
	throw new ClassNotFoundException(name);
    }

    /**
     * Converts an array of bytes into an instance of class <tt>Class</tt>.
     * Before the <tt>Class</tt> can be used it must be resolved.  This method
     * is deprecated in favor of the version that takes the class name as its
     * first argument, and is more secure.
     *
     * @param  b
     *         The bytes that make up the class data.  The bytes in positions
     *         <tt>off</tt> through <tt>off+len-1</tt> should have the format
     *         of a valid class file as defined by the <a
     *         href="http://java.sun.com/docs/books/vmspec/">Java Virtual
     *         Machine Specification</a>.
     *
     * @param  off
     *         The start offset in <tt>b</tt> of the class data
     *
     * @param  len
     *         The length of the class data
     *
     * @return  The <tt>Class</tt> object that was created from the specified
     *          class data
     *
     * @throws  ClassFormatError
     *          If the data did not contain a valid class
     *
     * @throws  IndexOutOfBoundsException
     *          If either <tt>off</tt> or <tt>len</tt> is negative, or if
     *          <tt>off+len</tt> is greater than <tt>b.length</tt>.
     *
     * @see  #loadClass(String, boolean)
     * @see  #resolveClass(Class)
     *
     * deprecated  Replaced by {@link #defineClass(String, byte[], int, int)
     * defineClass(String, byte[], int, int)}
     *
    protected final Class defineClass(byte[] b, int off, int len)
	throws ClassFormatError
    {
	return defineClass(null, b, off, len, null);
    }
     */

    /**
     * Converts an array of bytes into an instance of class <tt>Class</tt>.
     * Before the <tt>Class</tt> can be used it must be resolved.
     *
     * <p> This method assigns a default {@link java.security.ProtectionDomain
     * <tt>ProtectionDomain</tt>} to the newly defined class.  The
     * <tt>ProtectionDomain</tt> is effectively granted the same set of
     * permissions returned when {@link
     * java.security.Policy#getPermissions(java.security.CodeSource)
     * <tt>Policy.getPolicy().getPermissions(new CodeSource(null, null))</tt>}
     * is invoked.  The default domain is created on the first invocation of
     * {@link #defineClass(String, byte[], int, int) <tt>defineClass</tt>},
     * and re-used on subsequent invocations.
     *
     * <p> To assign a specific <tt>ProtectionDomain</tt> to the class, use
     * the {@link #defineClass(String, byte[], int, int,
     * java.security.ProtectionDomain) <tt>defineClass</tt>} method that takes a
     * <tt>ProtectionDomain</tt> as one of its arguments.  </p>
     *
     * @param  name
     *         The expected name of the class, or <tt>null</tt>
     *         if not known, using '<tt>.</tt>' and not '<tt>/</tt>' as the
     *         separator and without a trailing <tt>.class</tt> suffix.
     *
     * @param  b
     *         The bytes that make up the class data.  The bytes in positions
     *         <tt>off</tt> through <tt>off+len-1</tt> should have the format
     *         of a valid class file as defined by the <a
     *         href="http://java.sun.com/docs/books/vmspec/">Java Virtual
     *         Machine Specification</a>.
     *
     * @param  off
     *         The start offset in <tt>b</tt> of the class data
     *
     * @param  len
     *         The length of the class data
     *
     * @return  The <tt>Class</tt> object that was created from the specified
     *          class data.
     *
     * @throws  ClassFormatError
     *          If the data did not contain a valid class
     *
     * @throws  IndexOutOfBoundsException
     *          If either <tt>off</tt> or <tt>len</tt> is negative, or if
     *          <tt>off+len</tt> is greater than <tt>b.length</tt>.
     *
     * @throws  SecurityException
     *          If an attempt is made to add this class to a package that
     *          contains classes that were signed by a different set of
     *          certificates than this class (which is unsigned), or if the
     *          class name begins with "<tt>java.</tt>".
     *
     * @see  #loadClass(String, boolean)
     * @see  #resolveClass(Class)
     * @see  java.security.CodeSource
     * @see  java.security.SecureClassLoader
     *
     * @since  1.1
     */
    protected final Class defineClass(String name, byte[] b, int off, int len)
	throws ClassFormatError
    {
	return defineClass(name, b, off, len, null);
    }

    /**
     * Converts an array of bytes into an instance of class <tt>Class</tt>,
     * with an optional <tt>ProtectionDomain</tt>.  If the domain is
     * <tt>null</tt>, then a default domain will be assigned to the class as
     * specified in the documentation for {@link #defineClass(String, byte[],
     * int, int)}.  Before the class can be used it must be resolved.
     *
     * <p> The first class defined in a package determines the exact set of
     * certificates that all subsequent classes defined in that package must
     * contain.  The set of certificates for a class is obtained from the
     * {@link java.security.CodeSource <tt>CodeSource</tt>} within the
     * <tt>ProtectionDomain</tt> of the class.  Any classes added to that
     * package must contain the same set of certificates or a
     * <tt>SecurityException</tt> will be thrown.  Note that if the
     * <tt>name</tt> argument is <tt>null</tt>, this check is not performed.
     * You should always pass in the name of the class you are defining as
     * well as the bytes.  This ensures that the class you are defining is
     * indeed the class you think it is.
     *
     * <p> The specified class name cannot begin with "<tt>java.</tt>", since
     * all classes in the "<tt>java.*</tt> packages can only be defined by the
     * bootstrap class loader. If the name parameter is not <tt>null</tt>, it
     * must be equal to the name of the class specified by the byte array
     * "<tt>b</tt>", otherwise a {@link <tt>NoClassDefFoundError</tt>} will be
     * thrown.  </p>
     *
     * @param  name
     *         The expected name of the class, or <tt>null</tt> if not known,
     *         using '<tt>.</tt>' and not '<tt>/</tt>' as the separator and
     *         without a trailing "<tt>.class</tt>" suffix.
     *
     * @param  b
     *         The bytes that make up the class data. The bytes in positions
     *         <tt>off</tt> through <tt>off+len-1</tt> should have the format
     *         of a valid class file as defined by the <a
     *         href="http://java.sun.com/docs/books/vmspec/">Java Virtual
     *         Machine Specification</a>.
     *
     * @param  off
     *         The start offset in <tt>b</tt> of the class data
     *
     * @param  len
     *         The length of the class data
     *
     * @param  protectionDomain
     *         The ProtectionDomain of the class
     *
     * @return  The <tt>Class</tt> object created from the data,
     *          and optional <tt>ProtectionDomain</tt>.
     *
     * @throws  ClassFormatError
     *          If the data did not contain a valid class
     *
     * @throws  NoClassDefFoundError
     *          If <tt>name</tt> is not equal to the name of the class
     *          specified by <tt>b</tt>
     *
     * @throws  IndexOutOfBoundsException
     *          If either <tt>off</tt> or <tt>len</tt> is negative, or if
     *          <tt>off+len</tt> is greater than <tt>b.length</tt>.
     *
     * @throws  SecurityException
     *          If an attempt is made to add this class to a package that
     *          contains classes that were signed by a different set of
     *          certificates than this class, or if the class name begins with
     *          "<tt>java.</tt>".
     */
    protected final Class defineClass(String name, byte[] b, int off, int len,
				      ProtectionDomain protectionDomain)
	throws ClassFormatError
    {
	check();
        if ((name != null) && name.startsWith("java.")) {
            throw new SecurityException("Prohibited package name: " +
                                        name.substring(0, name.lastIndexOf('.')));
        }
	if (protectionDomain == null) {
	    protectionDomain = getDefaultDomain();
	}

	if (name != null)
	    checkCerts(name, protectionDomain.getCodeSource());

        if (!checkName(name))
            throw new NoClassDefFoundError("Illegal name: " + name);

	Class c = null;

	try {
	    c = defineClass0(name, b, off, len, protectionDomain);
	} catch (ClassFormatError cfe) {
	    // Class format error - try to transform the bytecode and
	    // define the class again
	    //
	    Object[] transformers = ClassFileTransformer.getTransformers();

	    for (int i = 0; transformers != null && i < transformers.length; i++) {
		try {
		    // Transform byte code using transformer
		    byte[] tb = ((ClassFileTransformer) transformers[i]).transform(b, off, len);
		    c = defineClass0(name, tb, 0, tb.length, protectionDomain);
		    break;
		} catch (ClassFormatError cfe2)	{
		    // If ClassFormatError occurs, try next transformer
		}
	    }

	    // Rethrow original ClassFormatError if unable to transform
	    // bytecode to well-formed
	    //
	    if (c == null)
		throw cfe;
	}

	/* load superclases in a way that avoids C recursion */
	c.loadSuperClasses();

	if (protectionDomain.getCodeSource() != null) {
	    java.security.cert.Certificate certs[] =
		protectionDomain.getCodeSource().getCertificates();
	    if (certs != null)
		setSigners(c, certs);
	}
	return c;
    }

    private static boolean checkName(String name) {
        if (name == null || name.length() == 0)
            return true;
        if (name.indexOf('/') != -1)
            return false;
        if (name.charAt(0) == '[')
            return false;
        return true;
    }

    private native Class defineClass0(String name, byte[] b, int off, int len,
	ProtectionDomain pd);

    private synchronized void checkCerts(String name, CodeSource cs) {
	int i = name.lastIndexOf('.');
	String pname = (i == -1) ? "" : name.substring(0, i);
	java.security.cert.Certificate[] pcerts =
	    (java.security.cert.Certificate[]) package2certs.get(pname);
        if (pcerts == null) {
	    // first class in this package gets to define which
	    // certificates must be the same for all other classes
	    // in this package
	    if (cs != null) {
		pcerts = cs.getCertificates();
	    }
	    if (pcerts == null) {
		if (nocerts == null)
		    nocerts = new java.security.cert.Certificate[0];
		pcerts = nocerts;
	    }
	    package2certs.put(pname, pcerts);
	} else {
	    java.security.cert.Certificate[] certs = null;
	    if (cs != null) {
		certs = cs.getCertificates();
	    }

	    if (!compareCerts(pcerts, certs)) {
		throw new SecurityException("class \""+ name +
					    "\"'s signer information does not match signer information of other classes in the same package");
	    }
	}
    }

    /**
     * check to make sure the certs for the new class (certs) are the same as
     * the certs for the first class inserted in the package (pcerts)
     */
    private boolean compareCerts(java.security.cert.Certificate[] pcerts,
				 java.security.cert.Certificate[] certs)
    {
	// certs can be null, indicating no certs.
	if ((certs == null) || (certs.length == 0)) {
	    return pcerts.length == 0;
	}

	// the length must be the same at this point
	if (certs.length != pcerts.length)
	    return false;

	// go through and make sure all the certs in one array
	// are in the other and vice-versa.
	boolean match;
	for (int i = 0; i < certs.length; i++) {
	    match = false;
	    for (int j = 0; j < pcerts.length; j++) {
		if (certs[i].equals(pcerts[j])) {
		    match = true;
		    break;
		}
	    }
	    if (!match) return false;
	}

	// now do the same for pcerts
	for (int i = 0; i < pcerts.length; i++) {
	    match = false;
	    for (int j = 0; j < certs.length; j++) {
		if (pcerts[i].equals(certs[j])) {
		    match = true;
		    break;
		}
	    }
	    if (!match) return false;
	}

	return true;
    }

    /**
     * Links the specified class.  This (misleadingly named) method may be
     * used by a class loader to link a class.  If the class <tt>c</tt> has
     * already been linked, then this method simply returns. Otherwise, the
     * class is linked as described in the "Execution" chapter of the <a
     * href="http://java.sun.com/docs/books/jls/">Java Language Specification</a>.
     * </p>
     *
     * @param  c
     *         The class to link
     *
     * @throws  NullPointerException
     *          If <tt>c</tt> is <tt>null</tt>.