/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* 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
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/**
* This class centralizes information about the JVM's linkage access control.
* @author jrose
*/
public class VerifyAccess {
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
*/
int mods, // actual member mods
Class<?> lookupClass,
int allowedModes) {
if (allowedModes == 0) return false;
// Usually refc and defc are the same, but if they differ, verify them both.
// Note that defc is verified in the switch below.
return false;
}
// Apply the special rules for refc here.
// If refc == defc, the call to isPublicSuperClass will do
// the whole job, since in that case refc (as defc) will be
// a superclass of the lookup class.
}
}
if (defc == lookupClass &&
return true; // easy check; all self-access is OK
switch (mods & ALL_ACCESS_MODES) {
case PUBLIC:
case PROTECTED:
return true;
return true;
return false;
case PACKAGE_ONLY: // That is, zero. Unmarked member is package-only access.
case PRIVATE:
// Loosened rules for privates follows access rules for inner classes.
return (ALLOW_NESTMATE_ACCESS &&
default:
}
}
return (refc == lookupClass ||
}
}
/**
* 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)
*/
int allowedModes) {
if (allowedModes == 0) return false;
return true;
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
*/
return true;
// Do it the hard way: Look up the type name from the refc loader.
try {
} 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
*/
return false;
}
return true;
}
/**
* Test if two classes have the same class loader and package qualifier.
* @param class1
* @param class2
* @return whether they are in the same package
*/
return true;
return false;
return false;
for (int i = 0; i < dot; i++) {
return false;
}
return true;
}
/** Return the package name for this class.
*/
}
/**
* 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
* @param class2
* @return whether they are identical or nested together
*/
return true;
return false;
return false;
return true;
}
return pkgmem;
}
boolean loader1MustBeParent) {
return true;
}
}
if (loader1MustBeParent) return false;
// see if loader2 is a parent of loader1:
}
return false;
}
/**
* Is the class loader of parentClass identical to, or an ancestor of,
* the class loader of childClass?
* @param parentClass
* @param childClass
* @return whether parentClass precedes or equals childClass in class loader order
*/
}
}