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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

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 package sun.invoke.util;

 import java.lang.reflect.Modifier;

 import static java.lang.reflect.Modifier.*;

 /**

  * This class centralizes information about the JVM's linkage access control.

  * @author jrose

  */

 public class VerifyAccess {

     private VerifyAccess() { }  // cannot instantiate

     private static final int PACKAGE_ONLY = 0;

     private static final int PACKAGE_ALLOWED = java.lang.invoke.MethodHandles.Lookup.PACKAGE;

     private static final int PROTECTED_OR_PACKAGE_ALLOWED = (PACKAGE_ALLOWED|PROTECTED);

     private static final int ALL_ACCESS_MODES = (PUBLIC|PRIVATE|PROTECTED|PACKAGE_ONLY);

     private static final boolean ALLOW_NESTMATE_ACCESS = false;

     /**

      * Evaluate the JVM linkage rules for access to the given method

      * on behalf of a caller class which proposes to perform the access.

      * Return true if the caller class has privileges to invoke a method

      * or access a field with the given properties.

      * This requires an accessibility check of the referencing class,

      * plus an accessibility check of the member within the class,

      * which depends on the member's modifier flags.

      * <p>

      * The relevant properties include the defining class ({@code defc})

      * of the member, and its modifier flags ({@code mods}).

      * Also relevant is the class used to make the initial symbolic reference

      * to the member ({@code refc}).  If this latter class is not distinguished,

      * the defining class should be passed for both arguments ({@code defc == refc}).

      * <h3>JVM Specification, 5.4.4 "Access Control"</h3>

      * A field or method R is accessible to a class or interface D if

      * and only if any of the following conditions is true:<ul>

      * <li>R is public.

      * <li>R is protected and is declared in a class C, and D is either

      *     a subclass of C or C itself.  Furthermore, if R is not

      *     static, then the symbolic reference to R must contain a

      *     symbolic reference to a class T, such that T is either a

      *     subclass of D, a superclass of D or D itself.

      * <li>R is either protected or has default access (that is,

      *     neither public nor protected nor private), and is declared

      *     by a class in the same runtime package as D.

      * <li>R is private and is declared in D.

      * </ul>

      * This discussion of access control omits a related restriction

      * on the target of a protected field access or method invocation

      * (the target must be of class D or a subtype of D). That

      * requirement is checked as part of the verification process

      * (5.4.1); it is not part of link-time access control.

      * @param refc the class used in the symbolic reference to the proposed member

      * @param defc the class in which the proposed member is actually defined

      * @param mods modifier flags for the proposed member

      * @param lookupClass the class for which the access check is being made

      * @return true iff the the accessing class can access such a member

      */

     public static boolean isMemberAccessible(Class<?> refc,  // symbolic ref class

                                              Class<?> defc,  // actual def class

                                              int      mods,  // actual member mods

                                              Class<?> lookupClass,

                                              int      allowedModes) {

         if (allowedModes == 0)  return false;

         assert((allowedModes & PUBLIC) != 0 &&

                (allowedModes & ~(ALL_ACCESS_MODES|PACKAGE_ALLOWED)) == 0);

         // The symbolic reference class (refc) must always be fully verified.

         if (!isClassAccessible(refc, lookupClass, allowedModes)) {

             return false;

         }

         // Usually refc and defc are the same, but verify defc also in case they differ.

         if (defc == lookupClass &&

             (allowedModes & PRIVATE) != 0)

             return true;        // easy check; all self-access is OK

         switch (mods & ALL_ACCESS_MODES) {

         case PUBLIC:

             return true;  // already checked above

         case PROTECTED:

             if ((allowedModes & PROTECTED_OR_PACKAGE_ALLOWED) != 0 &&

                 isSamePackage(defc, lookupClass))

                 return true;

             if ((allowedModes & PROTECTED) == 0)

                 return false;

             if ((mods & STATIC) != 0 &&

                 !isRelatedClass(refc, lookupClass))

                 return false;

             if ((allowedModes & PROTECTED) != 0 &&

                 isSuperClass(defc, lookupClass))

                 return true;

             return false;

         case PACKAGE_ONLY:  // That is, zero.  Unmarked member is package-only access.

             return ((allowedModes & PACKAGE_ALLOWED) != 0 &&

                     isSamePackage(defc, lookupClass));

         case PRIVATE:

             // Loosened rules for privates follows access rules for inner classes.

             return (ALLOW_NESTMATE_ACCESS &&

                     (allowedModes & PRIVATE) != 0 &&

                     isSamePackageMember(defc, lookupClass));

         default:

             throw new IllegalArgumentException("bad modifiers: "+Modifier.toString(mods));

         }

     }

     static boolean isRelatedClass(Class<?> refc, Class<?> lookupClass) {

         return (refc == lookupClass ||

                 refc.isAssignableFrom(lookupClass) ||

                 lookupClass.isAssignableFrom(refc));

     }

     static boolean isSuperClass(Class<?> defc, Class<?> lookupClass) {

         return defc.isAssignableFrom(lookupClass);

     }

     static int getClassModifiers(Class<?> c) {

         // This would return the mask stored by javac for the source-level modifiers.

         //   return c.getModifiers();

         // But what we need for JVM access checks are the actual bits from the class header.

         // ...But arrays and primitives are synthesized with their own odd flags:

         if (c.isArray() || c.isPrimitive())

             return c.getModifiers();

         return c.getModifiers();

 //        return Reflection.getClassAccessFlags(c);

     }

     /**

      * Evaluate the JVM linkage rules for access to the given class on behalf of caller.

      * <h3>JVM Specification, 5.4.4 "Access Control"</h3>

      * A class or interface C is accessible to a class or interface D

      * if and only if either of the following conditions are true:<ul>

      * <li>C is public.

      * <li>C and D are members of the same runtime package.

      * </ul>

      * @param refc the symbolic reference class to which access is being checked (C)

      * @param lookupClass the class performing the lookup (D)

      */

     public static boolean isClassAccessible(Class<?> refc, Class<?> lookupClass,

                                             int allowedModes) {

         if (allowedModes == 0)  return false;

         assert((allowedModes & PUBLIC) != 0 &&

                (allowedModes & ~(ALL_ACCESS_MODES|PACKAGE_ALLOWED)) == 0);

         int mods = getClassModifiers(refc);

         if (isPublic(mods))

             return true;

         if ((allowedModes & PACKAGE_ALLOWED) != 0 &&

             isSamePackage(lookupClass, refc))

             return true;

         return false;

     }

     /**

      * Decide if the given method type, attributed to a member or symbolic

      * reference of a given reference class, is really visible to that class.

      * @param type the supposed type of a member or symbolic reference of refc

      * @param refc the class attempting to make the reference

      */

     public static boolean isTypeVisible(Class<?> type, Class<?> refc) {

         if (type == refc)  return true;  // easy check

         while (type.isArray())  type = type.getComponentType();

         if (type.isPrimitive() || type == Object.class)  return true;

         ClassLoader parent = type.getClassLoader();

         if (parent == null)  return true;

         ClassLoader child  = refc.getClassLoader();

         if (child == null)  return false;

         if (parent == child || loadersAreRelated(parent, child, true))

             return true;

         // Do it the hard way:  Look up the type name from the refc loader.

         try {

             Class<?> res = child.loadClass(type.getName());

             return (type == res);

         } catch (ClassNotFoundException ex) {

             return false;

         }

     }

     /**

      * Decide if the given method type, attributed to a member or symbolic

      * reference of a given reference class, is really visible to that class.

      * @param type the supposed type of a member or symbolic reference of refc

      * @param refc the class attempting to make the reference

      */

     public static boolean isTypeVisible(java.lang.invoke.MethodType type, Class<?> refc) {

         for (int n = -1, max = type.parameterCount(); n < max; n++) {

             Class<?> ptype = (n < 0 ? type.returnType() : type.parameterType(n));

             if (!isTypeVisible(ptype, refc))

                 return false;

         }

         return true;

     }

     /**

      * Test if two classes have the same class loader and package qualifier.

      * @param class1 a class

      * @param class2 another class

      * @return whether they are in the same package

      */

     public static boolean isSamePackage(Class<?> class1, Class<?> class2) {

         assert(!class1.isArray() && !class2.isArray());

         if (class1 == class2)

             return true;

         if (class1.getClassLoader() != class2.getClassLoader())

             return false;

         String name1 = class1.getName(), name2 = class2.getName();

         int dot = name1.lastIndexOf('.');

         if (dot != name2.lastIndexOf('.'))

             return false;

         for (int i = 0; i < dot; i++) {

             if (name1.charAt(i) != name2.charAt(i))

                 return false;

         }

         return true;

     }

     /** Return the package name for this class.

      */

     public static String getPackageName(Class<?> cls) {

         assert(!cls.isArray());

         String name = cls.getName();

         int dot = name.lastIndexOf('.');

         if (dot < 0)  return "";

         return name.substring(0, dot);

     }

     /**

      * Test if two classes are defined as part of the same package member (top-level class).

      * If this is true, they can share private access with each other.

      * @param class1 a class

      * @param class2 another class

      * @return whether they are identical or nested together

      */

     public static boolean isSamePackageMember(Class<?> class1, Class<?> class2) {

         if (class1 == class2)

             return true;

         if (!isSamePackage(class1, class2))

             return false;

         if (getOutermostEnclosingClass(class1) != getOutermostEnclosingClass(class2))

             return false;

         return true;

     }

     private static Class<?> getOutermostEnclosingClass(Class<?> c) {

         throw new IllegalStateException("Needed?");

 //        Class<?> pkgmem = c;

 //        for (Class<?> enc = c; (enc = enc.getEnclosingClass()) != null; )

 //            pkgmem = enc;

 //        return pkgmem;

     }

     private static boolean loadersAreRelated(ClassLoader loader1, ClassLoader loader2,

                                              boolean loader1MustBeParent) {

         if (loader1 == loader2 || loader1 == null

                 || (loader2 == null && !loader1MustBeParent)) {

             return true;

         }

         for (ClassLoader scan2 = loader2;

                 scan2 != null; scan2 = scan2.getParent()) {

             if (scan2 == loader1)  return true;

         }

         if (loader1MustBeParent)  return false;

         // see if loader2 is a parent of loader1:

         for (ClassLoader scan1 = loader1;

                 scan1 != null; scan1 = scan1.getParent()) {

             if (scan1 == loader2)  return true;

         }

         return false;

     }

     /**

      * Is the class loader of parentClass identical to, or an ancestor of,

      * the class loader of childClass?

      * @param parentClass a class

      * @param childClass another class, which may be a descendent of the first class

      * @return whether parentClass precedes or equals childClass in class loader order

      */

     public static boolean classLoaderIsAncestor(Class<?> parentClass, Class<?> childClass) {

         return loadersAreRelated(parentClass.getClassLoader(), childClass.getClassLoader(), true);

     }

 }