JexlPermissions.java
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* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
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*
* https://www.apache.org/licenses/LICENSE-2.0
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package org.apache.commons.jexl3.introspection;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;
import java.util.Objects;
import java.util.Set;
import java.util.stream.Collectors;
import org.apache.commons.jexl3.internal.introspection.PermissionsParser;
/**
* This interface describes permissions used by JEXL introspection that constrain which
* packages/classes/constructors/fields/methods are made visible to JEXL scripts.
* <p>By specifying or implementing permissions, it is possible to constrain precisely which objects can be manipulated
* by JEXL, allowing users to enter their own expressions or scripts whilst maintaining tight control
* over what can be executed. JEXL introspection mechanism will check whether it is permitted to
* access a constructor, method or field before exposition to the {@link JexlUberspect}. The restrictions
* are applied in all cases, for any {@link org.apache.commons.jexl3.introspection.JexlUberspect.ResolverStrategy}.
* </p>
* <p>This complements using a dedicated {@link ClassLoader} and/or {@link SecurityManager} - being deprecated -
* and possibly {@link JexlSandbox} with a simpler mechanism. The {@link org.apache.commons.jexl3.annotations.NoJexl}
* annotation processing is actually performed using the result of calling {@link #parse(String...)} with no arguments;
* implementations shall delegate calls to its methods for {@link org.apache.commons.jexl3.annotations.NoJexl} to be
* processed.</p>
* <p>A simple textual configuration can be used to create user-defined permissions using
* {@link JexlPermissions#parse(String...)}. The permission syntax supports both positive (+) and negative (-)
* declarations:</p>
* <ul>
* <li><b>Negative restrictions ({@code -})</b>: By default or when prefixed with {@code -}, class restrictions
* explicitly <b>deny</b> access to the specified members (or the entire class if the block is empty).
* This is the default mode and works like {@link org.apache.commons.jexl3.annotations.NoJexl}.</li>
* <li><b>Positive restrictions ({@code +})</b>: When prefixed with {@code +}, class restrictions
* explicitly <b>allow only</b> the specified members (or the entire class if the block is empty), denying
* all others. This provides a whitelist approach where you must explicitly list what is permitted.</li>
* </ul>
* <p>For example:</p>
* <pre>
* // Deny specific methods in a class (negative restriction - default)
* java.lang { System { exit(); } } // or -System { exit(); }
*
* // Allow only specific methods in a class (positive restriction)
* java.lang { +System { currentTimeMillis(); nanoTime(); } }
*
* // Allow entire class (positive restriction with empty block)
* java.io -{ +PrintWriter{} +Writer{} }
* </pre>
*
*<p>To instantiate a JEXL engine using permissions, one should use a {@link org.apache.commons.jexl3.JexlBuilder}
* and call {@link org.apache.commons.jexl3.JexlBuilder#permissions(JexlPermissions)}. Another approach would
* be to instantiate a {@link JexlUberspect} with those permissions and call
* {@link org.apache.commons.jexl3.JexlBuilder#uberspect(JexlUberspect)}.</p>
*
* <p>
* To help migration from earlier versions, it is possible to revert to the JEXL 3.2 default lenient behavior
* by calling {@link org.apache.commons.jexl3.JexlBuilder#setDefaultPermissions(JexlPermissions)} with
* {@link #UNRESTRICTED} as parameter before creating a JEXL engine instance.
* </p>
* <p>
* For the same reason, using JEXL through scripting, it is possible to revert the underlying JEXL behavior to
* JEXL 3.2 default by calling {@link org.apache.commons.jexl3.scripting.JexlScriptEngine#setPermissions(JexlPermissions)}
* with {@link #UNRESTRICTED} as parameter.
* </p>
*
* @since 3.3
*/
public interface JexlPermissions {
/**
* A permission delegation that augments the RESTRICTED permission with an explicit
* set of classes.
* <p>A typical use case is to deny access to a package - and thus all its classes - but allow
* a few specific classes.</p>
* <p>Note that the newer positive restriction syntax is preferable as in:
* <code>RESTRICTED.compose("java.lang { +Class {} }")</code>.</p>
*/
final class ClassPermissions extends JexlPermissions.Delegate {
/**
* The set of explicitly allowed classes, overriding the delegate permissions.
*/
private final Set<String> allowedClasses;
/**
* Creates permissions based on the RESTRICTED set but allowing an explicit set.
*
* @param allow the set of allowed classes
*/
public ClassPermissions(final Class<?>... allow) {
this(JexlPermissions.RESTRICTED, allow);
}
/**
* Creates permissions by augmenting an existing set with an explicit set of allowed classes.
* @param permissions the base permissions to augment
* @param allow the set of allowed classes
*/
public ClassPermissions(final JexlPermissions permissions, final Class<?>... allow) {
this(permissions, Arrays.stream(Objects.requireNonNull(allow)).map(Class::getCanonicalName).collect(Collectors.toList()));
}
/**
* Creates permissions by augmenting an existing set with an explicit set of allowed canonical class names.
*
* @param delegate the base to delegate to
* @param allow the list of class canonical names
*/
public ClassPermissions(final JexlPermissions delegate, final Collection<String> allow) {
super(Objects.requireNonNull(delegate));
allowedClasses = new HashSet<>(Objects.requireNonNull(allow));
}
@Override
public boolean allow(final Constructor<?> constructor) {
return validate(constructor) &&
(allowedClasses.contains(constructor.getDeclaringClass().getCanonicalName()) || super.allow(constructor));
}
@Override
public boolean allow(final Class<?> clazz) {
return validate(clazz) &&
(allowedClasses.contains(clazz.getCanonicalName()) || super.allow(clazz));
}
@Override
public boolean allow(final Class<?> clazz, final Field field) {
if (!validate(field)) {
return false;
}
if (!validate(clazz)) {
return false;
}
if (!field.getDeclaringClass().isAssignableFrom(clazz)) {
return false;
}
if (super.allow(clazz, field)) {
return true;
}
return isClassAllowed(clazz);
}
@Override
public boolean allow(final Class<?> clazz, final Method method) {
if (!validate(method)) {
return false;
}
if (!method.getDeclaringClass().isAssignableFrom(clazz)) {
return false;
}
if (super.allow(clazz, method)) {
return true;
}
return isClassAllowed(clazz);
}
@Override
public JexlPermissions compose(final String... src) {
return new ClassPermissions(base.compose(src), allowedClasses);
}
private boolean isClassAllowed(final Class<?> aClass) {
Class<?> clazz = aClass;
// let's walk all interfaces
for (final Class<?> inter : clazz.getInterfaces()) {
if (allowedClasses.contains(inter.getCanonicalName())) {
return true;
}
}
// let's walk all super classes
while (clazz != null) {
if (allowedClasses.contains(clazz.getCanonicalName())) {
return true;
}
clazz = clazz.getSuperclass();
}
return false;
}
}
/**
* A base for permission delegation allowing functional refinement.
* Overloads should call the appropriate validate() method early in their body.
*/
class Delegate implements JexlPermissions {
/**
* The permissions we delegate to.
*/
protected final JexlPermissions base;
/**
* Constructs a new instance.
*
* @param delegate the delegate.
*/
protected Delegate(final JexlPermissions delegate) {
base = delegate;
}
@Override
public boolean allow(final Class<?> clazz) {
return base.allow(clazz);
}
@Override
public boolean allow(final Constructor<?> ctor) {
return base.allow(ctor);
}
@Override
public boolean allow(final Field field) {
return validate(field) && allow(field.getDeclaringClass(), field);
}
@Override
public boolean allow(final Class<?> clazz, final Field field) {
return base.allow(clazz, field);
}
@Override
public boolean allow(final Method method) {
return validate(method) && allow(method.getDeclaringClass(), method);
}
@Override
public boolean allow(final Class<?> clazz, final Method method) {
return base.allow(clazz, method);
}
@Override
public boolean allow(final Package pack) {
return base.allow(pack);
}
@Override
public JexlPermissions compose(final String... src) {
return new Delegate(base.compose(src));
}
}
/**
* The unrestricted permissions.
* <p>This enables any public class, method, constructor or field to be visible to JEXL and used in scripts.</p>
*
* @since 3.3
*/
JexlPermissions UNRESTRICTED = JexlPermissions.parse();
/**
* A restricted singleton.
* <p>The RESTRICTED set is built using the following allowed packages and denied packages/classes.</p>
* <p>Of particular importance are the restrictions on the {@link System},
* {@link Runtime}, {@link ProcessBuilder}, {@link Class} and those on {@link java.net},
* {@link java.io} and {@link java.lang.reflect} that should provide a decent level of isolation between the scripts
* and its host.
* </p>
* <p>
* Every allowed package is declared explicitly using the positive {@code +{}} syntax rather than a
* {@code .*} wildcard. A wildcard matches a package <em>and all of its sub-packages</em>, which is not
* future-proof: a sub-package added by a later JDK (or a dangerous existing one such as
* {@code java.util.zip}/{@code java.util.jar} - which can read files - or {@code java.nio.file}) would be
* silently exposed. Listing each package explicitly keeps the perimeter closed: only the packages below are
* visible, nothing else.
* </p>
* <p>Allowed packages (each member is visible unless explicitly denied):</p>
* <ul>
* <li>java.math</li>
* <li>java.text</li>
* <li>java.time, java.time.chrono, java.time.format, java.time.temporal, java.time.zone</li>
* <li>java.util, java.util.concurrent, java.util.concurrent.atomic, java.util.function, java.util.stream, java.util.regex</li>
* <li>java.nio, java.nio.charset</li>
* <li>org.w3c.dom</li>
* <li>java.lang (minus the denied classes below)</li>
* <li>org.apache.commons.jexl3 (minus JexlBuilder)</li>
* </ul>
* <p>Denied classes / members (carved out of otherwise-allowed packages):</p>
* <ul>
* <li>java.lang { Runtime, System, ProcessBuilder, Process, RuntimePermission, SecurityManager, Thread, ThreadGroup, Class, ClassLoader }</li>
* <li>java.io { everything except PrintWriter, Writer, StringWriter, Reader, InputStream, OutputStream }</li>
* <li>java.util.concurrent { Executors and the thread-pool / fork-join executor classes }</li>
* <li>java.time.zone { ZoneRulesProvider } (prevents JVM-wide time-zone provider registration)</li>
* <li>org.apache.commons.jexl3 { JexlBuilder }</li>
* </ul>
* <p>Notably absent (and therefore denied) are file/IO/persistence/loader-bearing packages such as
* {@code java.util.zip}, {@code java.util.jar}, {@code java.util.prefs}, {@code java.util.logging},
* {@code java.util.concurrent.locks}, {@code java.nio.file}, {@code java.lang.reflect},
* {@code java.lang.invoke} and {@code org.w3c.dom.ls}.</p>
*/
JexlPermissions RESTRICTED = JexlPermissions.parse(
"# Default Uberspect Permissions",
"java.math +{}",
"java.text +{}",
"java.time +{}",
"java.time.chrono +{}",
"java.time.format +{}",
"java.time.temporal +{}",
"java.time.zone +{ -ZoneRulesProvider{} }",
"java.util +{}",
"java.util.concurrent +{" +
"-Executors{} -ExecutorService{} -AbstractExecutorService{}" +
"-ThreadPoolExecutor{} -ScheduledThreadPoolExecutor{} -ScheduledExecutorService{}" +
"-ForkJoinPool{} -ForkJoinTask{} -ForkJoinWorkerThread{}" +
"}",
"java.util.concurrent.atomic +{}",
"java.util.function +{}",
"java.util.stream +{}",
"java.util.regex +{}",
"org.w3c.dom +{}",
"java.lang +{" +
"-Runtime{} -System{} -ProcessBuilder{} -Process{}" +
"-RuntimePermission{} -SecurityManager{}" +
"-Thread{} -ThreadGroup{} -Class{} -ClassLoader{}" +
"}",
"java.io -{ +PrintWriter{} +Writer{} +StringWriter{} +Reader{} +InputStream{} +OutputStream{} }",
"java.nio +{}",
"java.nio.charset +{}",
"org.apache.commons.jexl3 +{ -JexlBuilder{} }"
);
/**
* Parses a set of permissions.
* <p>
* In JEXL 3.3, the syntax recognizes 2 types of permissions:
* </p>
* <ul>
* <li>Allowing access to a wildcard restricted set of packages. </li>
* <li>Denying access to packages, classes (and inner classes), methods and fields</li>
* </ul>
* <p>Wildcards specifications determine the set of allowed packages. When empty, all packages can be
* used. When using JEXL to expose functional elements, their packages should be exposed through wildcards.
* These allow composing the volume of what is allowed by addition.</p>
* <p>Restrictions behave exactly like the {@link org.apache.commons.jexl3.annotations.NoJexl} annotation;
* they can restrict access to package, class, inner-class, methods and fields.
* These allow refining the volume of what is allowed by extrusion.</p>
* An example of a tight environment that would not allow scripts to wander could be:
* <pre>
* # allow a very restricted set of base classes
* java.math.*
* java.text.*
* java.util.*
* # deny classes that could pose a security risk
* java.lang { Runtime {} System {} ProcessBuilder {} Class {} }
* org.apache.commons.jexl3 { JexlBuilder {} }
* </pre>
* <p><b>Syntax Overview:</b></p>
* <ul>
* <li>Syntax for wildcards is the name of the package suffixed by {@code .*}.</li>
* <li>Syntax for restrictions is a list of package restrictions.</li>
* <li>A package restriction is a package name followed by a block (as in curly-bracket block {})
* that contains a list of class restrictions.</li>
* <li>A class restriction is a class name prefixed by an optional {@code -} or {@code +} sign
* followed by a block of member restrictions.</li>
* <li>A member restriction can be a class restriction - to restrict
* nested classes -, a field which is the Java field name suffixed with {@code ;}, a method composed of
* its Java name suffixed with {@code ();}. Constructor restrictions are specified like methods using the
* class name as method name.</li>
* </ul>
* <p><b>Negative ({@code -}) vs Positive ({@code +}) Restrictions:</b></p>
* <ul>
* <li><b>Negative restriction (default or {@code -} prefix)</b>: Explicitly <b>denies</b> access to the members
* declared in its block. If the block is empty, the entire class is denied.
* <br>Example: {@code java.lang { -System { exit(); } }} denies System.exit() but allows other System methods.
* <br>Example: {@code java.lang { Runtime {} }} denies the entire Runtime class (empty block means deny all).</li>
* <li><b>Positive restriction ({@code +} prefix)</b>: Explicitly <b>allows only</b> the members declared
* in its block, denying all others not listed. If the block is empty, the entire class is allowed.
* <br>Example: {@code java.lang { +System { currentTimeMillis(); } }} allows only System.currentTimeMillis(),
* denying all other System methods.
* <br>Example: {@code java.io -{ +PrintWriter{} +Writer{} }} in the context of a denied java.io package,
* allows only PrintWriter and Writer classes entirely (empty blocks mean allow all members).</li>
* </ul>
* <p>
* All overrides and overloads of constructors or methods are allowed or restricted at the same time,
* the restriction being based on their names, not their whole signature. This differs from the @NoJexl annotation.
* </p>
* <p><b>Complete Example:</b></p>
* <pre>
* # some wildcards
* java.util.* # java.util is pretty much a must-have
* my.allowed.package0.*
* another.allowed.package1.*
* # nojexl like restrictions
* my.package.internal {} # the whole package is hidden
* my.package {
* +class4 { theMethod(); } # POSITIVE: only theMethod can be called in class4, all others denied
* class0 {
* class1 {} # NEGATIVE (default): the whole class1 is hidden
* class2 {
* class2(); # class2 constructors cannot be invoked
* class3 {
* aMethod(); # aMethod cannot be called
* aField; # aField cannot be accessed
* }
* } # end of class2
* class0(); # class0 constructors cannot be invoked
* method(); # method cannot be called
* field; # field cannot be accessed
* } # end class0
* } # end package my.package
* </pre>
*
* @param src the permissions source, the default (NoJexl aware) permissions if null
* @return the permissions instance
* @since 3.3
*/
static JexlPermissions parse(final String... src) {
return new PermissionsParser().parse(src);
}
/**
* Checks whether a class allows JEXL introspection.
* <p>If the class disallows JEXL introspection, none of its constructors, methods or fields
* as well as derived classes are visible to JEXL and cannot be used in scripts or expressions.
* If one of its super-classes is not allowed, tbe class is not allowed either.</p>
* <p>For interfaces, only methods and fields are disallowed in derived interfaces or implementing classes.</p>
*
* @param clazz the class to check
* @return true if JEXL is allowed to introspect, false otherwise
* @since 3.3
*/
boolean allow(Class<?> clazz);
/**
* Checks whether a constructor allows JEXL introspection.
* <p>If a constructor is not allowed, the new operator cannot be used to instantiate its declared class
* in scripts or expressions.</p>
*
* @param ctor the constructor to check
* @return true if JEXL is allowed to introspect, false otherwise
* @since 3.3
*/
boolean allow(Constructor<?> ctor);
/**
* Checks whether a field explicitly allows JEXL introspection.
* <p>If a field is not allowed, it cannot be resolved and accessed in scripts or expressions.</p>
*
* @param field the field to check
* @return true if JEXL is allowed to introspect, false otherwise
* @since 3.3
*/
boolean allow(Field field);
/**
* Checks whether a field explicitly allows JEXL introspection.
* <p>If a field is not allowed, it cannot be resolved and accessed in scripts or expressions.</p>
* @param clazz the class from which the field is accessed, used to check that the field is allowed for this class
* @param field the field to check
* @return true if JEXL is allowed to introspect, false otherwise
* @since 3.6.3
*/
default boolean allow(Class<?> clazz, Field field) {
return allow(field);
}
/**
* Checks whether a method allows JEXL introspection.
* <p>If a method is not allowed, it cannot be resolved and called in scripts or expressions.</p>
* <p>Since methods can be overridden and overloaded, this also checks that no superclass or interface
* explicitly disallows this method.</p>
*
* @param method the method to check
* @return true if JEXL is allowed to introspect, false otherwise
* @since 3.3
*/
boolean allow(Method method);
/**
* Checks whether a method allows JEXL introspection.
* <p>If a method is not allowed, it cannot be resolved and called in scripts or expressions.</p>
* <p>Since methods can be overridden and overloaded, this checks that this class explicitly allows
* this method - superseding any superclass or interface specified permissions.</p>
*
* @param clazz the class from which the method is accessed, used to check that the method is allowed for this class
* @param method the method to check
* @return true if JEXL is allowed to introspect, false otherwise
* @since 3.6.3
*/
default boolean allow(Class<?> clazz, Method method) {
return allow(method);
}
/**
* Checks whether a package allows JEXL introspection.
* <p>If the package disallows JEXL introspection, none of its classes or interfaces are visible
* to JEXL and cannot be used in scripts or expression.</p>
*
* @param pack the package
* @return true if JEXL is allowed to introspect, false otherwise
* @since 3.3
*/
boolean allow(Package pack);
/**
* Compose these permissions with a new set.
* <p>This is a convenience method meant to easily give access to the packages JEXL is
* used to integrate with. For instance, using <code>{@link #RESTRICTED}.compose("com.my.app.*")</code>
* would extend the restricted set of permissions by allowing the com.my.app package.</p>
*
* @param src the new constraints
* @return the new permissions
*/
JexlPermissions compose(String... src);
/**
* Checks that a class is valid for permission check.
*
* @param clazz the class
* @return true if the class is not null, false otherwise
*/
default boolean validate(final Class<?> clazz) {
return clazz != null;
}
/**
* Checks that a constructor is valid for permission check.
*
* @param constructor the constructor
* @return true if constructor is not null and public, false otherwise
*/
default boolean validate(final Constructor<?> constructor) {
return constructor != null && Modifier.isPublic(constructor.getModifiers());
}
/**
* Checks that a field is valid for permission check.
*
* @param field the constructor
* @return true if field is not null and public, false otherwise
*/
default boolean validate(final Field field) {
return field != null && Modifier.isPublic(field.getModifiers());
}
/**
* Checks that a method is valid for permission check.
*
* @param method the method
* @return true if method is not null and public, false otherwise
*/
default boolean validate(final Method method) {
return method != null && Modifier.isPublic(method.getModifiers());
}
/**
* Checks that a package is valid for permission check.
*
* @param pack the package
* @return true if the class is not null, false otherwise
*/
default boolean validate(final Package pack) {
return pack != null;
}
}