Java Language
Beveiligingsmanager
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SecurityManager inschakelen
Java Virtual Machines (JVM's) kunnen worden uitgevoerd met een geïnstalleerde SecurityManager. De SecurityManager bepaalt wat de code die in de JVM wordt uitgevoerd, mag doen op basis van factoren zoals waar de code is geladen en welke certificaten zijn gebruikt om de code te ondertekenen.
De SecurityManager kan worden geïnstalleerd door de systeemeigenschap java.security.manager op de opdrachtregel in te stellen bij het starten van de JVM:
java -Djava.security.manager <main class name>
of programmeerbaar vanuit Java-code:
System.setSecurityManager(new SecurityManager())
De standaard Java SecurityManager verleent machtigingen op basis van een beleid, dat wordt gedefinieerd in een beleidsbestand. Als er geen beleidsbestand is opgegeven, wordt het standaardbeleidsbestand onder $JAVA_HOME/lib/security/java.policy gebruikt.
Sandboxing-klassen geladen door een ClassLoader
De ClassLoader moet een ProtectionDomain dat de bron van de code identificeert:
public class PluginClassLoader extends ClassLoader {
private final ClassProvider provider;
private final ProtectionDomain pd;
public PluginClassLoader(ClassProvider provider) {
this.provider = provider;
Permissions permissions = new Permissions();
this.pd = new ProtectionDomain(provider.getCodeSource(), permissions, this, null);
}
@Override
protected Class<?> findClass(String name) throws ClassNotFoundException {
byte[] classDef = provider.getClass(name);
Class<?> clazz = defineClass(name, classDef, 0, classDef.length, pd);
return clazz;
}
}
Door findClass overschrijven findClass plaats van loadClass het delegatiemodel behouden en zal de PluginClassLoader eerst het systeem en de bovenliggende classloader doorzoeken op klassedefinities.
Maak een beleid:
public class PluginSecurityPolicy extends Policy {
private final Permissions appPermissions = new Permissions();
private final Permissions pluginPermissions = new Permissions();
public PluginSecurityPolicy() {
// amend this as appropriate
appPermissions.add(new AllPermission());
// add any permissions plugins should have to pluginPermissions
}
@Override
public Provider getProvider() {
return super.getProvider();
}
@Override
public String getType() {
return super.getType();
}
@Override
public Parameters getParameters() {
return super.getParameters();
}
@Override
public PermissionCollection getPermissions(CodeSource codesource) {
return new Permissions();
}
@Override
public PermissionCollection getPermissions(ProtectionDomain domain) {
return isPlugin(domain)?pluginPermissions:appPermissions;
}
private boolean isPlugin(ProtectionDomain pd){
return pd.getClassLoader() instanceof PluginClassLoader;
}
}
Stel ten slotte het beleid en een SecurityManager in (standaardimplementatie is prima):
Policy.setPolicy(new PluginSecurityPolicy());
System.setSecurityManager(new SecurityManager());
Implementatiebeleid weigert regels
Het is soms wenselijk om een bepaalde Permission voor sommige ProtectionDomain te weigeren , ongeacht andere toestemmingen die het domein toekent. Dit voorbeeld toont slechts een van alle mogelijke benaderingen om aan dit soort vereisten te voldoen. Het introduceert een "negatief" toestemming klasse, samen met een wrapper dat de standaard mogelijk maakt Policy te worden hergebruikt als een opslagplaats van dergelijke rechten.
Opmerkingen:
- De standaardsyntaxis van het beleidsbestand en het mechanisme voor het toewijzen van rechten in het algemeen blijven onaangetast. Dit betekent dat regels voor het weigeren in beleidsdossiers nog steeds worden uitgedrukt als subsidies .
- Het beleid wrapper is bedoeld om specifiek in te kapselen de standaard-file gesteunde
Policy(aangenomen datcom.sun.security.provider.PolicyFile). - Geweigerde machtigingen worden alleen als zodanig op beleidsniveau verwerkt. Als statisch toegewezen aan een domein, worden ze standaard door dat domein behandeld als gewone "positieve" machtigingen.
De klasse DeniedPermission
package com.example;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Modifier;
import java.security.BasicPermission;
import java.security.Permission;
import java.security.UnresolvedPermission;
import java.text.MessageFormat;
/**
* A representation of a "negative" privilege.
* <p>
* A <code>DeniedPermission</code>, when "granted" (to some <code>ProtectionDomain</code> and/or
* <code>Principal</code>), represents a privilege which <em>cannot</em> be exercised, regardless of
* any positive permissions (<code>AllPermission</code> included) possessed. In other words, if a
* set of granted permissions, <em>P</em>, contains a permission of this class, <em>D</em>, then the
* set of effectively granted permissions is<br/>
* <br/>
* <em>{ P<sub>implied</sub> - D<sub>implied</sub> }</em>.
* </p>
* <p>
* Each instance of this class encapsulates a <em>target permission</em>, representing the
* "positive" permission being denied.
* </p>
* Denied permissions employ the following naming scheme:<br/>
* <br/>
* <em><target_class_name>:<target_name>(:<target_actions>)</em><br/>
* <br/>
* where:
* <ul>
* <li><em>target_class_name</em> is the name of the target permission's class,</li>
* <li><em>target_name</em> is the name of the target permission, and</li>
* <li><em>target_actions</em> is, optionally, the actions string of the target permission.</li>
* </ul>
* A denied permission, having a target permission <em>t</em>, is said to <em>imply</em> another
* permission <em>p</em>, if:
* <ul>
* <li>p <em>is not</em> itself a denied permission, and <code>(t.implies(p) == true)</code>,
* or</li>
* <li>p <em>is</em> a denied permission, with a target <em>t1</em>, and
* <code>(t.implies(t1) == true)</code>.
* </ul>
* <p>
* It is the responsibility of the policy decision point (e.g., the <code>Policy</code> provider) to
* take denied permission semantics into account when issuing authorization statements.
* </p>
*/
public final class DeniedPermission extends BasicPermission {
private final Permission target;
private static final long serialVersionUID = 473625163869800679L;
/**
* Instantiates a <code>DeniedPermission</code> that encapsulates a target permission of the
* indicated class, specified name and, optionally, actions.
*
* @throws IllegalArgumentException
* if:
* <ul>
* <li><code>targetClassName</code> is <code>null</code>, the empty string, does not
* refer to a concrete <code>Permission</code> descendant, or refers to
* <code>DeniedPermission.class</code> or <code>UnresolvedPermission.class</code>.</li>
* <li><code>targetName</code> is <code>null</code>.</li>
* <li><code>targetClassName</code> cannot be instantiated, and it's the caller's fault;
* e.g., because <code>targetName</code> and/or <code>targetActions</code> do not adhere
* to the naming constraints of the target class; or due to the target class not
* exposing a <code>(String name)</code>, or <code>(String name, String actions)</code>
* constructor, depending on whether <code>targetActions</code> is <code>null</code> or
* not.</li>
* </ul>
*/
public static DeniedPermission newDeniedPermission(String targetClassName, String targetName,
String targetActions) {
if (targetClassName == null || targetClassName.trim().isEmpty() || targetName == null) {
throw new IllegalArgumentException(
"Null or empty [targetClassName], or null [targetName] argument was supplied.");
}
StringBuilder sb = new StringBuilder(targetClassName).append(":").append(targetName);
if (targetName != null) {
sb.append(":").append(targetName);
}
return new DeniedPermission(sb.toString());
}
/**
* Instantiates a <code>DeniedPermission</code> that encapsulates a target permission of the class,
* name and, optionally, actions, collectively provided as the <code>name</code> argument.
*
* @throws IllegalArgumentException
* if:
* <ul>
* <li><code>name</code>'s target permission class name component is empty, does not
* refer to a concrete <code>Permission</code> descendant, or refers to
* <code>DeniedPermission.class</code> or <code>UnresolvedPermission.class</code>.</li>
* <li><code>name</code>'s target name component is <code>empty</code></li>
* <li>the target permission class cannot be instantiated, and it's the caller's fault;
* e.g., because <code>name</code>'s target name and/or target actions component(s) do
* not adhere to the naming constraints of the target class; or due to the target class
* not exposing a <code>(String name)</code>, or
* <code>(String name, String actions)</code> constructor, depending on whether the
* target actions component is empty or not.</li>
* </ul>
*/
public DeniedPermission(String name) {
super(name);
String[] comps = name.split(":");
if (comps.length < 2) {
throw new IllegalArgumentException(MessageFormat.format("Malformed name [{0}] argument.", name));
}
this.target = initTarget(comps[0], comps[1], ((comps.length < 3) ? null : comps[2]));
}
/**
* Instantiates a <code>DeniedPermission</code> that encapsulates the given target permission.
*
* @throws IllegalArgumentException
* if <code>target</code> is <code>null</code>, a <code>DeniedPermission</code>, or an
* <code>UnresolvedPermission</code>.
*/
public static DeniedPermission newDeniedPermission(Permission target) {
if (target == null) {
throw new IllegalArgumentException("Null [target] argument.");
}
if (target instanceof DeniedPermission || target instanceof UnresolvedPermission) {
throw new IllegalArgumentException("[target] must not be a DeniedPermission or an UnresolvedPermission.");
}
StringBuilder sb = new StringBuilder(target.getClass().getName()).append(":").append(target.getName());
String targetActions = target.getActions();
if (targetActions != null) {
sb.append(":").append(targetActions);
}
return new DeniedPermission(sb.toString(), target);
}
private DeniedPermission(String name, Permission target) {
super(name);
this.target = target;
}
private Permission initTarget(String targetClassName, String targetName, String targetActions) {
Class<?> targetClass;
try {
targetClass = Class.forName(targetClassName);
}
catch (ClassNotFoundException cnfe) {
if (targetClassName.trim().isEmpty()) {
targetClassName = "<empty>";
}
throw new IllegalArgumentException(
MessageFormat.format("Target Permission class [{0}] not found.", targetClassName));
}
if (!Permission.class.isAssignableFrom(targetClass) || Modifier.isAbstract(targetClass.getModifiers())) {
throw new IllegalArgumentException(MessageFormat
.format("Target Permission class [{0}] is not a (concrete) Permission.", targetClassName));
}
if (targetClass == DeniedPermission.class || targetClass == UnresolvedPermission.class) {
throw new IllegalArgumentException("Target Permission class cannot be a DeniedPermission itself.");
}
Constructor<?> targetCtor;
try {
if (targetActions == null) {
targetCtor = targetClass.getConstructor(String.class);
}
else {
targetCtor = targetClass.getConstructor(String.class, String.class);
}
}
catch (NoSuchMethodException nsme) {
throw new IllegalArgumentException(MessageFormat.format(
"Target Permission class [{0}] does not provide or expose a (String name) or (String name, String actions) constructor.",
targetClassName));
}
try {
return (Permission) targetCtor
.newInstance(((targetCtor.getParameterCount() == 1) ? new Object[] { targetName }
: new Object[] { targetName, targetActions }));
}
catch (ReflectiveOperationException roe) {
if (roe instanceof InvocationTargetException) {
if (targetName == null) {
targetName = "<null>";
}
else if (targetName.trim().isEmpty()) {
targetName = "<empty>";
}
if (targetActions == null) {
targetActions = "<null>";
}
else if (targetActions.trim().isEmpty()) {
targetActions = "<empty>";
}
throw new IllegalArgumentException(MessageFormat.format(
"Could not instantiate target Permission class [{0}]; provided target name [{1}] and/or target actions [{2}] potentially erroneous.",
targetClassName, targetName, targetActions), roe);
}
throw new RuntimeException(
"Could not instantiate target Permission class [{0}]; an unforeseen error occurred - see attached cause for details",
roe);
}
}
/**
* Checks whether the given permission is implied by this one, as per the {@link DeniedPermission
* overview}.
*/
@Override
public boolean implies(Permission p) {
if (p instanceof DeniedPermission) {
return target.implies(((DeniedPermission) p).target);
}
return target.implies(p);
}
/**
* Returns this denied permission's target permission (the actual positive permission which is not
* to be granted).
*/
public Permission getTargetPermission() {
return target;
}
}
De klasse DenyingPolicy
package com.example;
import java.security.CodeSource;
import java.security.NoSuchAlgorithmException;
import java.security.Permission;
import java.security.PermissionCollection;
import java.security.Policy;
import java.security.ProtectionDomain;
import java.security.UnresolvedPermission;
import java.util.Enumeration;
/**
* Wrapper that adds rudimentary {@link DeniedPermission} processing capabilities to the standard
* file-backed <code>Policy</code>.
*/
public final class DenyingPolicy extends Policy {
{
try {
defaultPolicy = Policy.getInstance("javaPolicy", null);
}
catch (NoSuchAlgorithmException nsae) {
throw new RuntimeException("Could not acquire default Policy.", nsae);
}
}
private final Policy defaultPolicy;
@Override
public PermissionCollection getPermissions(CodeSource codesource) {
return defaultPolicy.getPermissions(codesource);
}
@Override
public PermissionCollection getPermissions(ProtectionDomain domain) {
return defaultPolicy.getPermissions(domain);
}
/**
* @return
* <ul>
* <li><code>true</code> if:</li>
* <ul>
* <li><code>permission</code> <em>is not</em> an instance of
* <code>DeniedPermission</code>,</li>
* <li>an <code>implies(domain, permission)</code> invocation on the system-default
* <code>Policy</code> yields <code>true</code>, and</li>
* <li><code>permission</code> <em>is not</em> implied by any <code>DeniedPermission</code>s
* having potentially been assigned to <code>domain</code>.</li>
* </ul>
* <li><code>false</code>, otherwise.
* </ul>
*/
@Override
public boolean implies(ProtectionDomain domain, Permission permission) {
if (permission instanceof DeniedPermission) {
/*
* At the policy decision level, DeniedPermissions can only themselves imply, not be implied (as
* they take away, rather than grant, privileges). Furthermore, clients aren't supposed to use this
* method for checking whether some domain _does not_ have a permission (which is what
* DeniedPermissions express after all).
*/
return false;
}
if (!defaultPolicy.implies(domain, permission)) {
// permission not granted, so no need to check whether denied
return false;
}
/*
* Permission granted--now check whether there's an overriding DeniedPermission. The following
* assumes that previousPolicy is a sun.security.provider.PolicyFile (different implementations
* might not support #getPermissions(ProtectionDomain) and/or handle UnresolvedPermissions
* differently).
*/
Enumeration<Permission> perms = defaultPolicy.getPermissions(domain).elements();
while (perms.hasMoreElements()) {
Permission p = perms.nextElement();
/*
* DeniedPermissions will generally remain unresolved, as no code is expected to check whether other
* code has been "granted" such a permission.
*/
if (p instanceof UnresolvedPermission) {
UnresolvedPermission up = (UnresolvedPermission) p;
if (up.getUnresolvedType().equals(DeniedPermission.class.getName())) {
// force resolution
defaultPolicy.implies(domain, up);
// evaluate right away, to avoid reiterating over the collection
p = new DeniedPermission(up.getUnresolvedName());
}
}
if (p instanceof DeniedPermission && p.implies(permission)) {
// permission denied
return false;
}
}
// permission granted
return true;
}
@Override
public void refresh() {
defaultPolicy.refresh();
}
}
demonstratie
package com.example;
import java.security.Policy;
public class Main {
public static void main(String... args) {
Policy.setPolicy(new DenyingPolicy());
System.setSecurityManager(new SecurityManager());
// should fail
System.getProperty("foo.bar");
}
}
Wijs enkele machtigingen toe:
grant codeBase "file:///path/to/classes/bin/-"
permission java.util.PropertyPermission "*", "read,write";
permission com.example.DeniedPermission "java.util.PropertyPermission:foo.bar:read";
};
Voer ten slotte de Main en kijk hoe deze mislukt, vanwege de " DeniedPermission " -regel (de DeniedPermission ) die de grant overschrijft (de PropertyPermission ). Merk op dat een setProperty("foo.baz", "xyz") in plaats daarvan zou zijn geslaagd, omdat de geweigerde toestemming alleen de actie "lezen" dekt, en alleen voor de eigenschap "foo.bar".
Modified text is an extract of the original Stack Overflow Documentation
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