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425 lines
20 KiB
Java
425 lines
20 KiB
Java
/*
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* Copyright (c) 2008, 2021, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package sun.invoke.util;
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import java.lang.reflect.Modifier;
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import static java.lang.reflect.Modifier.*;
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import jdk.internal.reflect.Reflection;
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/**
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* This class centralizes information about the JVM's linkage access control.
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* @author jrose
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*/
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public class VerifyAccess {
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private VerifyAccess() { } // cannot instantiate
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private static final int UNCONDITIONAL_ALLOWED = java.lang.invoke.MethodHandles.Lookup.UNCONDITIONAL;
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private static final int ORIGINAL_ALLOWED = java.lang.invoke.MethodHandles.Lookup.ORIGINAL;
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private static final int MODULE_ALLOWED = java.lang.invoke.MethodHandles.Lookup.MODULE;
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private static final int PACKAGE_ONLY = 0;
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private static final int PACKAGE_ALLOWED = java.lang.invoke.MethodHandles.Lookup.PACKAGE;
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private static final int PROTECTED_OR_PACKAGE_ALLOWED = (PACKAGE_ALLOWED|PROTECTED);
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private static final int ALL_ACCESS_MODES = (PUBLIC|PRIVATE|PROTECTED|PACKAGE_ONLY);
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/**
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* Evaluate the JVM linkage rules for access to the given method
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* on behalf of a caller class which proposes to perform the access.
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* Return true if the caller class has privileges to invoke a method
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* or access a field with the given properties.
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* This requires an accessibility check of the referencing class,
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* plus an accessibility check of the member within the class,
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* which depends on the member's modifier flags.
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* <p>
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* The relevant properties include the defining class ({@code defc})
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* of the member, and its modifier flags ({@code mods}).
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* Also relevant is the class used to make the initial symbolic reference
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* to the member ({@code refc}). If this latter class is not distinguished,
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* the defining class should be passed for both arguments ({@code defc == refc}).
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* <h3>JVM Specification, 5.4.4 "Access Control"</h3>
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* A field or method R is accessible to a class or interface D if
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* and only if any of the following is true:
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* <ul>
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* <li>R is public.</li>
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* <li>R is protected and is declared in a class C, and D is either
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* a subclass of C or C itself. Furthermore, if R is not static,
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* then the symbolic reference to R must contain a symbolic
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* reference to a class T, such that T is either a subclass of D,
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* a superclass of D, or D itself.
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* <p>During verification, it was also required that, even if T is
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* a superclass of D, the target reference of a protected instance
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* field access or method invocation must be an instance of D or a
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* subclass of D (4.10.1.8).</p></li>
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* <li>R is either protected or has default access (that is, neither
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* public nor protected nor private), and is declared by a class
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* in the same run-time package as D.</li>
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* <li>R is private and is declared in D by a class or interface
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* belonging to the same nest as D.</li>
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* </ul>
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* If a referenced field or method is not accessible, access checking
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* throws an IllegalAccessError. If an exception is thrown while
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* attempting to determine the nest host of a class or interface,
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* access checking fails for the same reason.
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*
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* @param refc the class used in the symbolic reference to the proposed member
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* @param defc the class in which the proposed member is actually defined
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* @param mods modifier flags for the proposed member
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* @param lookupClass the class for which the access check is being made
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* @param prevLookupClass the class for which the access check is being made
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* @param allowedModes allowed modes
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* @return true iff the accessing class can access such a member
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*/
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public static boolean isMemberAccessible(Class<?> refc, // symbolic ref class
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Class<?> defc, // actual def class
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int mods, // actual member mods
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Class<?> lookupClass,
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Class<?> prevLookupClass,
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int allowedModes) {
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if (allowedModes == 0) return false;
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assert((allowedModes & ~(ALL_ACCESS_MODES|PACKAGE_ALLOWED|MODULE_ALLOWED|UNCONDITIONAL_ALLOWED|ORIGINAL_ALLOWED)) == 0);
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// The symbolic reference class (refc) must always be fully verified.
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if (!isClassAccessible(refc, lookupClass, prevLookupClass, allowedModes)) {
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return false;
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}
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// Usually refc and defc are the same, but verify defc also in case they differ.
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if (defc == lookupClass &&
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(allowedModes & PRIVATE) != 0)
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return true; // easy check; all self-access is OK with a private lookup
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switch (mods & ALL_ACCESS_MODES) {
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case PUBLIC:
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assert (allowedModes & PUBLIC) != 0 || (allowedModes & UNCONDITIONAL_ALLOWED) != 0;
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return true; // already checked above
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case PROTECTED:
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assert !defc.isInterface(); // protected members aren't allowed in interfaces
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if ((allowedModes & PROTECTED_OR_PACKAGE_ALLOWED) != 0 &&
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isSamePackage(defc, lookupClass))
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return true;
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if ((allowedModes & PROTECTED) == 0)
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return false;
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// Protected members are accessible by subclasses, which does not include interfaces.
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// Interfaces are types, not classes. They should not have access to
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// protected members in j.l.Object, even though it is their superclass.
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if ((mods & STATIC) != 0 &&
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!isRelatedClass(refc, lookupClass))
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return false;
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if ((allowedModes & PROTECTED) != 0 &&
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isSubClass(lookupClass, defc))
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return true;
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return false;
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case PACKAGE_ONLY: // That is, zero. Unmarked member is package-only access.
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assert !defc.isInterface(); // package-private members aren't allowed in interfaces
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return ((allowedModes & PACKAGE_ALLOWED) != 0 &&
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isSamePackage(defc, lookupClass));
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case PRIVATE:
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// Rules for privates follows access rules for nestmates.
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boolean canAccess = ((allowedModes & PRIVATE) != 0 &&
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Reflection.areNestMates(defc, lookupClass));
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// for private methods the selected method equals the
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// resolved method - so refc == defc
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assert (canAccess && refc == defc) || !canAccess;
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return canAccess;
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default:
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throw new IllegalArgumentException("bad modifiers: "+Modifier.toString(mods));
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}
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}
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static boolean isRelatedClass(Class<?> refc, Class<?> lookupClass) {
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return (refc == lookupClass ||
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isSubClass(refc, lookupClass) ||
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isSubClass(lookupClass, refc));
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}
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static boolean isSubClass(Class<?> lookupClass, Class<?> defc) {
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return defc.isAssignableFrom(lookupClass) &&
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!lookupClass.isInterface(); // interfaces are types, not classes.
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}
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static int getClassModifiers(Class<?> c) {
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// This would return the mask stored by javac for the source-level modifiers.
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// return c.getModifiers();
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// But what we need for JVM access checks are the actual bits from the class header.
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// ...But arrays and primitives are synthesized with their own odd flags:
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if (c.isArray() || c.isPrimitive())
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return c.getModifiers();
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return Reflection.getClassAccessFlags(c);
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}
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/**
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* Evaluate the JVM linkage rules for access to the given class on behalf of caller.
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* <h3>JVM Specification, 5.4.4 "Access Control"</h3>
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* A class or interface C is accessible to a class or interface D
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* if and only if any of the following conditions are true:<ul>
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* <li>C is public and in the same module as D.
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* <li>D is in a module that reads the module containing C, C is public and in a
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* package that is exported to the module that contains D.
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* <li>C and D are members of the same runtime package.
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* </ul>
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*
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* @param refc the symbolic reference class to which access is being checked (C)
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* @param lookupClass the class performing the lookup (D)
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* @param prevLookupClass the class from which the lookup was teleported or null
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* @param allowedModes allowed modes
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*/
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public static boolean isClassAccessible(Class<?> refc,
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Class<?> lookupClass,
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Class<?> prevLookupClass,
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int allowedModes) {
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if (allowedModes == 0) return false;
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assert((allowedModes & ~(ALL_ACCESS_MODES|PACKAGE_ALLOWED|MODULE_ALLOWED|UNCONDITIONAL_ALLOWED|ORIGINAL_ALLOWED)) == 0);
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if ((allowedModes & PACKAGE_ALLOWED) != 0 &&
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isSamePackage(lookupClass, refc))
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return true;
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int mods = getClassModifiers(refc);
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if (isPublic(mods)) {
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Module lookupModule = lookupClass.getModule();
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Module refModule = refc.getModule();
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// early VM startup case, java.base not defined or
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// module system is not fully initialized and exports are not set up
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if (lookupModule == null || !jdk.internal.misc.VM.isModuleSystemInited()) {
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assert lookupModule == refModule;
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return true;
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}
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// allow access to public types in all unconditionally exported packages
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if ((allowedModes & UNCONDITIONAL_ALLOWED) != 0) {
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return refModule.isExported(refc.getPackageName());
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}
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if (lookupModule == refModule && prevLookupClass == null) {
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// allow access to all public types in lookupModule
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if ((allowedModes & MODULE_ALLOWED) != 0)
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return true;
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assert (allowedModes & PUBLIC) != 0;
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return refModule.isExported(refc.getPackageName());
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}
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// cross-module access
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// 1. refc is in different module from lookupModule, or
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// 2. refc is in lookupModule and a different module from prevLookupModule
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Module prevLookupModule = prevLookupClass != null ? prevLookupClass.getModule()
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: null;
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assert refModule != lookupModule || refModule != prevLookupModule;
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if (isModuleAccessible(refc, lookupModule, prevLookupModule))
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return true;
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// public class not accessible to lookupClass
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return false;
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}
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return false;
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}
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/*
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* Tests if a class or interface REFC is accessible to m1 and m2 where m2
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* may be null.
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*
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* A class or interface REFC in m is accessible to m1 and m2 if and only if
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* both m1 and m2 read m and m exports the package of REFC at least to
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* both m1 and m2.
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*/
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public static boolean isModuleAccessible(Class<?> refc, Module m1, Module m2) {
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Module refModule = refc.getModule();
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assert refModule != m1 || refModule != m2;
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int mods = getClassModifiers(refc);
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if (isPublic(mods)) {
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if (m1.canRead(refModule) && (m2 == null || m2.canRead(refModule))) {
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String pn = refc.getPackageName();
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// refc is exported package to at least both m1 and m2
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if (refModule.isExported(pn, m1) && (m2 == null || refModule.isExported(pn, m2)))
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return true;
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}
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}
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return false;
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}
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/**
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* Decide if the given method type, attributed to a member or symbolic
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* reference of a given reference class, is really visible to that class.
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* @param type the supposed type of a member or symbolic reference of refc
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* @param refc the class attempting to make the reference
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*/
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public static boolean ensureTypeVisible(Class<?> type, Class<?> refc) {
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if (type == refc) {
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return true; // easy check
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}
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while (type.isArray()) type = type.getComponentType();
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if (type.isPrimitive() || type == Object.class) {
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return true;
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}
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ClassLoader typeLoader = type.getClassLoader();
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ClassLoader refcLoader = refc.getClassLoader();
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if (typeLoader == refcLoader) {
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return true;
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}
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if (refcLoader == null && typeLoader != null) {
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return false;
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}
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// The API for actually loading classes, ClassLoader.defineClass,
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// guarantees that classes with names beginning "java." cannot be aliased,
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// because class loaders cannot load them directly. However, it is beneficial
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// for JIT-compilers to ensure all signature classes are loaded.
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// JVM doesn't install any loader contraints when performing MemberName resolution,
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// so eagerly resolving signature classes is a way to match what JVM achieves
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// with loader constraints during method resolution for invoke bytecodes.
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// Do it the hard way: Look up the type name from the refc loader.
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//
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// Force the refc loader to report and commit to a particular binding for this type name (type.getName()).
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//
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// In principle, this query might force the loader to load some unrelated class,
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// which would cause this query to fail (and the original caller to give up).
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// This would be wasted effort, but it is expected to be very rare, occurring
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// only when an attacker is attempting to create a type alias.
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// In the normal case, one class loader will simply delegate to the other,
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// and the same type will be visible through both, with no extra loading.
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//
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// It is important to go through Class.forName instead of ClassLoader.loadClass
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// because Class.forName goes through the JVM system dictionary, which records
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// the class lookup once for all. This means that even if a not-well-behaved class loader
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// would "change its mind" about the meaning of the name, the Class.forName request
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// will use the result cached in the JVM system dictionary. Note that the JVM system dictionary
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// will record the first successful result. Unsuccessful results are not stored.
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//
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// The looked up type ("res") is compared for equality against the proposed
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// type ("type") and then is discarded. Thus, the worst that can happen to
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// the "child" class loader is that it is bothered to load and report a class
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// that differs from "type"; this happens once due to JVM system dictionary
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// memoization. And the caller never gets to look at the alternate type binding
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// ("res"), whether it exists or not.
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final String name = type.getName();
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Class<?> res = null;
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try {
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res = Class.forName(name, false, refcLoader);
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} catch (ClassNotFoundException | LinkageError e) {
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// Assume the class is not found
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}
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return (type == res);
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}
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/**
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* Decide if the given method type, attributed to a member or symbolic
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* reference of a given reference class, is really visible to that class.
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* @param type the supposed type of a member or symbolic reference of refc
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* @param refc the class attempting to make the reference
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*/
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public static boolean ensureTypeVisible(java.lang.invoke.MethodType type, Class<?> refc) {
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if (!ensureTypeVisible(type.returnType(), refc)) {
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return false;
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}
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for (int n = 0, max = type.parameterCount(); n < max; n++) {
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if (!ensureTypeVisible(type.parameterType(n), refc)) {
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return false;
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}
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}
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return true;
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}
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/**
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* Tests if two classes are in the same module.
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* @param class1 a class
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* @param class2 another class
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* @return whether they are in the same module
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*/
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public static boolean isSameModule(Class<?> class1, Class<?> class2) {
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return class1.getModule() == class2.getModule();
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}
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/**
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* Test if two classes have the same class loader and package qualifier.
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* @param class1 a class
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* @param class2 another class
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* @return whether they are in the same package
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*/
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public static boolean isSamePackage(Class<?> class1, Class<?> class2) {
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if (class1 == class2)
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return true;
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if (class1.getClassLoader() != class2.getClassLoader())
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return false;
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return class1.getPackageName() == class2.getPackageName();
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}
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/**
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* Test if two classes are defined as part of the same package member (top-level class).
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* If this is true, they can share private access with each other.
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* @param class1 a class
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* @param class2 another class
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* @return whether they are identical or nested together
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*/
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public static boolean isSamePackageMember(Class<?> class1, Class<?> class2) {
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if (class1 == class2)
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return true;
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if (!isSamePackage(class1, class2))
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return false;
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if (getOutermostEnclosingClass(class1) != getOutermostEnclosingClass(class2))
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return false;
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return true;
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}
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private static Class<?> getOutermostEnclosingClass(Class<?> c) {
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Class<?> pkgmem = c;
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for (Class<?> enc = c; (enc = enc.getEnclosingClass()) != null; )
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pkgmem = enc;
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return pkgmem;
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}
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private static boolean loadersAreRelated(ClassLoader loader1, ClassLoader loader2,
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boolean loader1MustBeParent) {
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if (loader1 == loader2 || loader1 == null
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|| (loader2 == null && !loader1MustBeParent)) {
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return true;
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}
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for (ClassLoader scan2 = loader2;
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scan2 != null; scan2 = scan2.getParent()) {
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if (scan2 == loader1) return true;
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}
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if (loader1MustBeParent) return false;
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// see if loader2 is a parent of loader1:
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for (ClassLoader scan1 = loader1;
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scan1 != null; scan1 = scan1.getParent()) {
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if (scan1 == loader2) return true;
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}
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return false;
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}
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/**
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* Is the class loader of parentClass identical to, or an ancestor of,
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* the class loader of childClass?
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* @param parentClass a class
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* @param childClass another class, which may be a descendent of the first class
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* @return whether parentClass precedes or equals childClass in class loader order
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*/
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public static boolean classLoaderIsAncestor(Class<?> parentClass, Class<?> childClass) {
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return loadersAreRelated(parentClass.getClassLoader(), childClass.getClassLoader(), true);
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}
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}
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