/*
* @(#)AccessControlContext.java 1.48 08/04/17
*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.security;
import java.util.ArrayList;
import java.util.List;
import sun.security.util.Debug;
import sun.security.util.SecurityConstants;
/**
* An AccessControlContext is used to make system resource access decisions
* based on the context it encapsulates.
*
* <p>More specifically, it encapsulates a context and
* has a single method, <code>checkPermission</code>,
* that is equivalent to the <code>checkPermission</code> method
* in the AccessController class, with one difference: The AccessControlContext
* <code>checkPermission</code> method makes access decisions based on the
* context it encapsulates,
* rather than that of the current execution thread.
*
* <p>Thus, the purpose of AccessControlContext is for those situations where
* a security check that should be made within a given context
* actually needs to be done from within a
* <i>different</i> context (for example, from within a worker thread).
*
* <p> An AccessControlContext is created by calling the
* <code>AccessController.getContext</code> method.
* The <code>getContext</code> method takes a "snapshot"
* of the current calling context, and places
* it in an AccessControlContext object, which it returns. A sample call is
* the following:
*
* <pre>
*
* AccessControlContext acc = AccessController.getContext()
*
* </pre>
*
* <p>
* Code within a different context can subsequently call the
* <code>checkPermission</code> method on the
* previously-saved AccessControlContext object. A sample call is the
* following:
*
* <pre>
*
* acc.checkPermission(permission)
*
* </pre>
*
* @see AccessController
*
* @author Roland Schemers
*/
public final class AccessControlContext {
private ProtectionDomain context[];
private boolean isPrivileged;
private AccessControlContext privilegedContext;
private DomainCombiner combiner = null;
private static boolean debugInit = false;
private static Debug debug = null;
static Debug getDebug()
{
if (debugInit)
return debug;
else {
if (Policy.isSet()) {
debug = Debug.getInstance("access");
debugInit = true;
}
return debug;
}
}
/**
* Create an AccessControlContext with the given set of ProtectionDomains.
* Context must not be null. Duplicate domains will be removed from the
* context.
*
* @param context the ProtectionDomains associated with this context.
* The non-duplicate domains are copied from the array. Subsequent
* changes to the array will not affect this AccessControlContext.
*/
public AccessControlContext(ProtectionDomain context[])
{
if (context.length == 0) {
this.context = null;
} else if (context.length == 1) {
if (context[0] != null) {
this.context = (ProtectionDomain[])context.clone();
} else {
this.context = null;
}
} else {
List v = new ArrayList(context.length);
for (int i =0; i< context.length; i++) {
if ((context[i] != null) && (!v.contains(context[i])))
v.add(context[i]);
}
this.context = new ProtectionDomain[v.size()];
this.context = (ProtectionDomain[]) v.toArray(this.context);
}
}
/**
* Create a new <code>AccessControlContext</code> with the given
* <code>AccessControlContext</code> and <code>DomainCombiner</code>.
* This constructor associates the provided
* <code>DomainCombiner</code> with the provided
* <code>AccessControlContext</code>.
*
* <p>
*
* @param acc the <code>AccessControlContext</code> associated
* with the provided <code>DomainCombiner</code>. <p>
*
* @param combiner the <code>DomainCombiner</code> to be associated
* with the provided <code>AccessControlContext</code>.
*
* @exception NullPointerException if the provided
* <code>context</code> is <code>null</code>. <p>
*
* @exception SecurityException if the caller does not have permission
* to invoke this constructor.
* @since 1.3
*/
public AccessControlContext(AccessControlContext acc,
DomainCombiner combiner) {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(SecurityConstants.CREATE_ACC_PERMISSION);
}
this.context = acc.context;
// we do not need to run the combine method on the
// provided ACC. it was already "combined" when the
// context was originally retrieved.
//
// at this point in time, we simply throw away the old
// combiner and use the newly provided one.
this.combiner = combiner;
}
/**
* package private for AccessController
*/
AccessControlContext(ProtectionDomain context[], DomainCombiner combiner) {
if (context != null) {
this.context = (ProtectionDomain[])context.clone();
}
this.combiner = combiner;
}
/**
* package private constructor for AccessController.getContext()
*/
AccessControlContext(ProtectionDomain context[],
boolean isPrivileged)
{
this.context = context;
this.isPrivileged = isPrivileged;
}
/**
* Returns true if this context is privileged.
*/
boolean isPrivileged()
{
return isPrivileged;
}
/**
* get the assigned combiner from the privileged or inherited context
*/
DomainCombiner getAssignedCombiner() {
AccessControlContext acc;
if (isPrivileged) {
acc = privilegedContext;
} else {
acc = AccessController.getInheritedAccessControlContext();
}
if (acc != null) {
return acc.combiner;
}
return null;
}
/**
* Get the <code>DomainCombiner</code> associated with this
* <code>AccessControlContext</code>.
*
* <p>
*
* @return the <code>DomainCombiner</code> associated with this
* <code>AccessControlContext</code>, or <code>null</code>
* if there is none.
*
* @exception SecurityException if the caller does not have permission
* to get the <code>DomainCombiner</code> associated with this
* <code>AccessControlContext</code>.
* @since 1.3
*/
public DomainCombiner getDomainCombiner() {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(SecurityConstants.GET_COMBINER_PERMISSION);
}
return combiner;
}
/**
* Determines whether the access request indicated by the
* specified permission should be allowed or denied, based on
* the security policy currently in effect, and the context in
* this object. The request is allowed only if every ProtectionDomain
* in the context implies the permission. Otherwise the request is
* denied.
*
* <p>
* This method quietly returns if the access request
* is permitted, or throws a suitable AccessControlException otherwise.
*
* @param perm the requested permission.
*
* @exception AccessControlException if the specified permission
* is not permitted, based on the current security policy and the
* context encapsulated by this object.
* @exception NullPointerException if the permission to check for is null.
*/
public void checkPermission(Permission perm)
throws AccessControlException
{
boolean dumpDebug = false;
if (perm == null) {
throw new NullPointerException("permission can't be null");
}
if (getDebug() != null) {
// If "codebase" is not specified, we dump the info by default.
dumpDebug = !Debug.isOn("codebase=");
if (!dumpDebug) {
// If "codebase" is specified, only dump if the specified code
// value is in the stack.
for (int i = 0; context != null && i < context.length; i++) {
if (context[i].getCodeSource() != null &&
context[i].getCodeSource().getLocation() != null &&
Debug.isOn("codebase=" + context[i].getCodeSource().getLocation().toString())) {
dumpDebug = true;
break;
}
}
}
dumpDebug &= !Debug.isOn("permission=") ||
Debug.isOn("permission=" + perm.getClass().getCanonicalName());
if (dumpDebug && Debug.isOn("stack")) {
Thread.currentThread().dumpStack();
}
if (dumpDebug && Debug.isOn("domain")) {
if (context == null) {
debug.println("domain (context is null)");
} else {
for (int i=0; i< context.length; i++) {
debug.println("domain "+i+" "+context[i]);
}
}
}
}
/*
* iterate through the ProtectionDomains in the context.
* Stop at the first one that doesn't allow the
* requested permission (throwing an exception).
*
*/
/* if ctxt is null, all we had on the stack were system domains,
or the first domain was a Privileged system domain. This
is to make the common case for system code very fast */
if (context == null)
return;
for (int i=0; i< context.length; i++) {
if (context[i] != null && !context[i].implies(perm)) {
if (dumpDebug) {
debug.println("access denied " + perm);
}
if (Debug.isOn("failure") && debug != null) {
// Want to make sure this is always displayed for failure,
// but do not want to display again if already displayed
// above.
if (!dumpDebug) {
debug.println("access denied " + perm);
}
Thread.currentThread().dumpStack();
final ProtectionDomain pd = context[i];
final Debug db = debug;
AccessController.doPrivileged (new PrivilegedAction() {
public Object run() {
db.println("domain that failed "+pd);
return null;
}
});
}
throw new AccessControlException("access denied "+perm, perm);
}
}
// allow if all of them allowed access
if (dumpDebug) {
debug.println("access allowed "+perm);
}
return;
}
/**
* Take the stack-based context (this) and combine it with the
* privileged or inherited context, if need be.
*/
AccessControlContext optimize() {
// the assigned (privileged or inherited) context
AccessControlContext acc;
if (isPrivileged) {
acc = privilegedContext;
} else {
acc = AccessController.getInheritedAccessControlContext();
}
// this.context could be null if only system code is on the stack;
// in that case, ignore the stack context
boolean skipStack = (context == null);
// acc.context could be null if only system code was involved;
// in that case, ignore the assigned context
boolean skipAssigned = (acc == null || acc.context == null);
if (acc != null && acc.combiner != null) {
// let the assigned acc's combiner do its thing
return goCombiner(context, acc);
}
// optimization: if neither have contexts; return acc if possible
// rather than this, because acc might have a combiner
if (skipAssigned && skipStack) {
return this;
}
// optimization: if there is no stack context; there is no reason
// to compress the assigned context, it already is compressed
if (skipStack) {
return acc;
}
int slen = context.length;
// optimization: if there is no assigned context and the stack length
// is less then or equal to two; there is no reason to compress the
// stack context, it already is
if (skipAssigned && slen <= 2) {
return this;
}
// optimization: if there is a single stack domain and that domain
// is already in the assigned context; no need to combine
if ((slen == 1) && (context[0] == acc.context[0])) {
return acc;
}
int n = (skipAssigned) ? 0 : acc.context.length;
// now we combine both of them, and create a new context
ProtectionDomain pd[] = new ProtectionDomain[slen + n];
// first copy in the assigned context domains, no need to compress
if (!skipAssigned) {
System.arraycopy(acc.context, 0, pd, 0, n);
}
// now add the stack context domains, discarding nulls and duplicates
outer:
for (int i = 0; i < context.length; i++) {
ProtectionDomain sd = context[i];
if (sd != null) {
for (int j = 0; j < n; j++) {
if (sd == pd[j]) {
continue outer;
}
}
pd[n++] = sd;
}
}
// if length isn't equal, we need to shorten the array
if (n != pd.length) {
// optimization: if we didn't really combine anything
if (!skipAssigned && n == acc.context.length) {
return acc;
} else if (skipAssigned && n == slen) {
return this;
}
ProtectionDomain tmp[] = new ProtectionDomain[n];
System.arraycopy(pd, 0, tmp, 0, n);
pd = tmp;
}
// return new AccessControlContext(pd, false);
// Reuse existing ACC
this.context = pd;
this.combiner = null;
this.isPrivileged = false;
return this;
}
private AccessControlContext goCombiner(ProtectionDomain[] current,
AccessControlContext assigned) {
// the assigned ACC's combiner is not null --
// let the combiner do its thing
// XXX we could add optimizations to 'current' here ...
if (getDebug() != null) {
debug.println("AccessControlContext invoking the Combiner");
}
// No need to clone current and assigned.context
// combine() will not update them
ProtectionDomain[] combinedPds = assigned.combiner.combine(
current, assigned.context);
// return new AccessControlContext(combinedPds, assigned.combiner);
// Reuse existing ACC
this.context = combinedPds;
this.combiner = assigned.combiner;
this.isPrivileged = false;
return this;
}
/**
* Checks two AccessControlContext objects for equality.
* Checks that <i>obj</i> is
* an AccessControlContext and has the same set of ProtectionDomains
* as this context.
* <P>
* @param obj the object we are testing for equality with this object.
* @return true if <i>obj</i> is an AccessControlContext, and has the
* same set of ProtectionDomains as this context, false otherwise.
*/
public boolean equals(Object obj) {
if (obj == this)
return true;
if (! (obj instanceof AccessControlContext))
return false;
AccessControlContext that = (AccessControlContext) obj;
if (context == null) {
return (that.context == null);
}
if (that.context == null)
return false;
if (!(this.containsAllPDs(that) && that.containsAllPDs(this)))
return false;
if (this.combiner == null)
return (that.combiner == null);
if (that.combiner == null)
return false;
if (!this.combiner.equals(that.combiner))
return false;
return true;
}
private boolean containsAllPDs(AccessControlContext that) {
boolean match = false;
//
// ProtectionDomains within an ACC currently cannot be null
// and this is enforced by the constructor and the various
// optimize methods. However, historically this logic made attempts
// to support the notion of a null PD and therefore this logic continues
// to support that notion.
ProtectionDomain thisPd;
for (int i = 0; i < context.length; i++) {
match = false;
if ((thisPd = context[i]) == null) {
for (int j = 0; (j < that.context.length) && !match; j++) {
match = (that.context[j] == null);
}
} else {
Class thisPdClass = thisPd.getClass();
ProtectionDomain thatPd;
for (int j = 0; (j < that.context.length) && !match; j++) {
thatPd = that.context[j];
// Class check required to avoid PD exposure (4285406)
match = (thatPd != null &&
thisPdClass == thatPd.getClass() && thisPd.equals(thatPd));
}
}
if (!match) return false;
}
return match;
}
/**
* Returns the hash code value for this context. The hash code
* is computed by exclusive or-ing the hash code of all the protection
* domains in the context together.
*
* @return a hash code value for this context.
*/
public int hashCode() {
int hashCode = 0;
if (context == null)
return hashCode;
for (int i =0; i < context.length; i++) {
if (context[i] != null)
hashCode ^= context[i].hashCode();
}
return hashCode;
}
}