001: /*
002: * Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved.
003: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004: *
005: * This code is free software; you can redistribute it and/or modify it
006: * under the terms of the GNU General Public License version 2 only, as
007: * published by the Free Software Foundation. Sun designates this
008: * particular file as subject to the "Classpath" exception as provided
009: * by Sun in the LICENSE file that accompanied this code.
010: *
011: * This code is distributed in the hope that it will be useful, but WITHOUT
012: * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013: * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014: * version 2 for more details (a copy is included in the LICENSE file that
015: * accompanied this code).
016: *
017: * You should have received a copy of the GNU General Public License version
018: * 2 along with this work; if not, write to the Free Software Foundation,
019: * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020: *
021: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022: * CA 95054 USA or visit www.sun.com if you need additional information or
023: * have any questions.
024: */
025:
026: package java.security;
027:
028: import java.util.ArrayList;
029: import java.util.List;
030: import sun.security.util.Debug;
031: import sun.security.util.SecurityConstants;
032:
033: /**
034: * An AccessControlContext is used to make system resource access decisions
035: * based on the context it encapsulates.
036: *
037: * <p>More specifically, it encapsulates a context and
038: * has a single method, <code>checkPermission</code>,
039: * that is equivalent to the <code>checkPermission</code> method
040: * in the AccessController class, with one difference: The AccessControlContext
041: * <code>checkPermission</code> method makes access decisions based on the
042: * context it encapsulates,
043: * rather than that of the current execution thread.
044: *
045: * <p>Thus, the purpose of AccessControlContext is for those situations where
046: * a security check that should be made within a given context
047: * actually needs to be done from within a
048: * <i>different</i> context (for example, from within a worker thread).
049: *
050: * <p> An AccessControlContext is created by calling the
051: * <code>AccessController.getContext</code> method.
052: * The <code>getContext</code> method takes a "snapshot"
053: * of the current calling context, and places
054: * it in an AccessControlContext object, which it returns. A sample call is
055: * the following:
056: *
057: * <pre>
058: * AccessControlContext acc = AccessController.getContext()
059: * </pre>
060: *
061: * <p>
062: * Code within a different context can subsequently call the
063: * <code>checkPermission</code> method on the
064: * previously-saved AccessControlContext object. A sample call is the
065: * following:
066: *
067: * <pre>
068: * acc.checkPermission(permission)
069: * </pre>
070: *
071: * @see AccessController
072: *
073: * @author Roland Schemers
074: */
075:
076: public final class AccessControlContext {
077:
078: private ProtectionDomain context[];
079: private boolean isPrivileged;
080: private AccessControlContext privilegedContext;
081: private DomainCombiner combiner = null;
082:
083: private static boolean debugInit = false;
084: private static Debug debug = null;
085:
086: static Debug getDebug() {
087: if (debugInit)
088: return debug;
089: else {
090: if (Policy.isSet()) {
091: debug = Debug.getInstance("access");
092: debugInit = true;
093: }
094: return debug;
095: }
096: }
097:
098: /**
099: * Create an AccessControlContext with the given set of ProtectionDomains.
100: * Context must not be null. Duplicate domains will be removed from the
101: * context.
102: *
103: * @param context the ProtectionDomains associated with this context.
104: * The non-duplicate domains are copied from the array. Subsequent
105: * changes to the array will not affect this AccessControlContext.
106: */
107: public AccessControlContext(ProtectionDomain context[]) {
108: if (context.length == 0) {
109: this .context = null;
110: } else if (context.length == 1) {
111: if (context[0] != null) {
112: this .context = (ProtectionDomain[]) context.clone();
113: } else {
114: this .context = null;
115: }
116: } else {
117: List<ProtectionDomain> v = new ArrayList<ProtectionDomain>(
118: context.length);
119: for (int i = 0; i < context.length; i++) {
120: if ((context[i] != null) && (!v.contains(context[i])))
121: v.add(context[i]);
122: }
123: this .context = new ProtectionDomain[v.size()];
124: this .context = (ProtectionDomain[]) v.toArray(this .context);
125: }
126: }
127:
128: /**
129: * Create a new <code>AccessControlContext</code> with the given
130: * <code>AccessControlContext</code> and <code>DomainCombiner</code>.
131: * This constructor associates the provided
132: * <code>DomainCombiner</code> with the provided
133: * <code>AccessControlContext</code>.
134: *
135: * <p>
136: *
137: * @param acc the <code>AccessControlContext</code> associated
138: * with the provided <code>DomainCombiner</code>.
139: *
140: * @param combiner the <code>DomainCombiner</code> to be associated
141: * with the provided <code>AccessControlContext</code>.
142: *
143: * @exception NullPointerException if the provided
144: * <code>context</code> is <code>null</code>.
145: *
146: * @exception SecurityException if a security manager is installed and the
147: * caller does not have the "createAccessControlContext"
148: * {@link SecurityPermission}
149: * @since 1.3
150: */
151: public AccessControlContext(AccessControlContext acc,
152: DomainCombiner combiner) {
153:
154: SecurityManager sm = System.getSecurityManager();
155: if (sm != null) {
156: sm.checkPermission(SecurityConstants.CREATE_ACC_PERMISSION);
157: }
158:
159: this .context = acc.context;
160:
161: // we do not need to run the combine method on the
162: // provided ACC. it was already "combined" when the
163: // context was originally retrieved.
164: //
165: // at this point in time, we simply throw away the old
166: // combiner and use the newly provided one.
167: this .combiner = combiner;
168: }
169:
170: /**
171: * package private for AccessController
172: */
173: AccessControlContext(ProtectionDomain context[],
174: DomainCombiner combiner) {
175: if (context != null) {
176: this .context = (ProtectionDomain[]) context.clone();
177: }
178: this .combiner = combiner;
179: }
180:
181: /**
182: * package private constructor for AccessController.getContext()
183: */
184:
185: AccessControlContext(ProtectionDomain context[],
186: boolean isPrivileged) {
187: this .context = context;
188: this .isPrivileged = isPrivileged;
189: }
190:
191: /**
192: * Returns true if this context is privileged.
193: */
194: boolean isPrivileged() {
195: return isPrivileged;
196: }
197:
198: /**
199: * get the assigned combiner from the privileged or inherited context
200: */
201: DomainCombiner getAssignedCombiner() {
202: AccessControlContext acc;
203: if (isPrivileged) {
204: acc = privilegedContext;
205: } else {
206: acc = AccessController.getInheritedAccessControlContext();
207: }
208: if (acc != null) {
209: return acc.combiner;
210: }
211: return null;
212: }
213:
214: /**
215: * Get the <code>DomainCombiner</code> associated with this
216: * <code>AccessControlContext</code>.
217: *
218: * <p>
219: *
220: * @return the <code>DomainCombiner</code> associated with this
221: * <code>AccessControlContext</code>, or <code>null</code>
222: * if there is none.
223: *
224: * @exception SecurityException if a security manager is installed and
225: * the caller does not have the "getDomainCombiner"
226: * {@link SecurityPermission}
227: * @since 1.3
228: */
229: public DomainCombiner getDomainCombiner() {
230:
231: SecurityManager sm = System.getSecurityManager();
232: if (sm != null) {
233: sm
234: .checkPermission(SecurityConstants.GET_COMBINER_PERMISSION);
235: }
236: return combiner;
237: }
238:
239: /**
240: * Determines whether the access request indicated by the
241: * specified permission should be allowed or denied, based on
242: * the security policy currently in effect, and the context in
243: * this object. The request is allowed only if every ProtectionDomain
244: * in the context implies the permission. Otherwise the request is
245: * denied.
246: *
247: * <p>
248: * This method quietly returns if the access request
249: * is permitted, or throws a suitable AccessControlException otherwise.
250: *
251: * @param perm the requested permission.
252: *
253: * @exception AccessControlException if the specified permission
254: * is not permitted, based on the current security policy and the
255: * context encapsulated by this object.
256: * @exception NullPointerException if the permission to check for is null.
257: */
258: public void checkPermission(Permission perm)
259: throws AccessControlException {
260: boolean dumpDebug = false;
261:
262: if (perm == null) {
263: throw new NullPointerException("permission can't be null");
264: }
265: if (getDebug() != null) {
266: // If "codebase" is not specified, we dump the info by default.
267: dumpDebug = !Debug.isOn("codebase=");
268: if (!dumpDebug) {
269: // If "codebase" is specified, only dump if the specified code
270: // value is in the stack.
271: for (int i = 0; context != null && i < context.length; i++) {
272: if (context[i].getCodeSource() != null
273: && context[i].getCodeSource().getLocation() != null
274: && Debug.isOn("codebase="
275: + context[i].getCodeSource()
276: .getLocation().toString())) {
277: dumpDebug = true;
278: break;
279: }
280: }
281: }
282:
283: dumpDebug &= !Debug.isOn("permission=")
284: || Debug.isOn("permission="
285: + perm.getClass().getCanonicalName());
286:
287: if (dumpDebug && Debug.isOn("stack")) {
288: Thread.currentThread().dumpStack();
289: }
290:
291: if (dumpDebug && Debug.isOn("domain")) {
292: if (context == null) {
293: debug.println("domain (context is null)");
294: } else {
295: for (int i = 0; i < context.length; i++) {
296: debug.println("domain " + i + " " + context[i]);
297: }
298: }
299: }
300: }
301:
302: /*
303: * iterate through the ProtectionDomains in the context.
304: * Stop at the first one that doesn't allow the
305: * requested permission (throwing an exception).
306: *
307: */
308:
309: /* if ctxt is null, all we had on the stack were system domains,
310: or the first domain was a Privileged system domain. This
311: is to make the common case for system code very fast */
312:
313: if (context == null)
314: return;
315:
316: for (int i = 0; i < context.length; i++) {
317: if (context[i] != null && !context[i].implies(perm)) {
318: if (dumpDebug) {
319: debug.println("access denied " + perm);
320: }
321:
322: if (Debug.isOn("failure")) {
323: // Want to make sure this is always displayed for failure,
324: // but do not want to display again if already displayed
325: // above.
326: if (!dumpDebug) {
327: debug.println("access denied " + perm);
328: }
329: Thread.currentThread().dumpStack();
330: final ProtectionDomain pd = context[i];
331: final Debug db = debug;
332: AccessController
333: .doPrivileged(new PrivilegedAction<Void>() {
334: public Void run() {
335: db.println("domain that failed "
336: + pd);
337: return null;
338: }
339: });
340: }
341: throw new AccessControlException("access denied "
342: + perm, perm);
343: }
344: }
345:
346: // allow if all of them allowed access
347: if (dumpDebug) {
348: debug.println("access allowed " + perm);
349: }
350:
351: return;
352: }
353:
354: /**
355: * Take the stack-based context (this) and combine it with the
356: * privileged or inherited context, if need be.
357: */
358: AccessControlContext optimize() {
359: // the assigned (privileged or inherited) context
360: AccessControlContext acc;
361: if (isPrivileged) {
362: acc = privilegedContext;
363: } else {
364: acc = AccessController.getInheritedAccessControlContext();
365: }
366:
367: // this.context could be null if only system code is on the stack;
368: // in that case, ignore the stack context
369: boolean skipStack = (context == null);
370:
371: // acc.context could be null if only system code was involved;
372: // in that case, ignore the assigned context
373: boolean skipAssigned = (acc == null || acc.context == null);
374:
375: if (acc != null && acc.combiner != null) {
376: // let the assigned acc's combiner do its thing
377: return goCombiner(context, acc);
378: }
379:
380: // optimization: if neither have contexts; return acc if possible
381: // rather than this, because acc might have a combiner
382: if (skipAssigned && skipStack) {
383: return this ;
384: }
385:
386: // optimization: if there is no stack context; there is no reason
387: // to compress the assigned context, it already is compressed
388: if (skipStack) {
389: return acc;
390: }
391:
392: int slen = context.length;
393:
394: // optimization: if there is no assigned context and the stack length
395: // is less then or equal to two; there is no reason to compress the
396: // stack context, it already is
397: if (skipAssigned && slen <= 2) {
398: return this ;
399: }
400:
401: // optimization: if there is a single stack domain and that domain
402: // is already in the assigned context; no need to combine
403: if ((slen == 1) && (context[0] == acc.context[0])) {
404: return acc;
405: }
406:
407: int n = (skipAssigned) ? 0 : acc.context.length;
408:
409: // now we combine both of them, and create a new context
410: ProtectionDomain pd[] = new ProtectionDomain[slen + n];
411:
412: // first copy in the assigned context domains, no need to compress
413: if (!skipAssigned) {
414: System.arraycopy(acc.context, 0, pd, 0, n);
415: }
416:
417: // now add the stack context domains, discarding nulls and duplicates
418: outer: for (int i = 0; i < context.length; i++) {
419: ProtectionDomain sd = context[i];
420: if (sd != null) {
421: for (int j = 0; j < n; j++) {
422: if (sd == pd[j]) {
423: continue outer;
424: }
425: }
426: pd[n++] = sd;
427: }
428: }
429:
430: // if length isn't equal, we need to shorten the array
431: if (n != pd.length) {
432: // optimization: if we didn't really combine anything
433: if (!skipAssigned && n == acc.context.length) {
434: return acc;
435: } else if (skipAssigned && n == slen) {
436: return this ;
437: }
438: ProtectionDomain tmp[] = new ProtectionDomain[n];
439: System.arraycopy(pd, 0, tmp, 0, n);
440: pd = tmp;
441: }
442:
443: // return new AccessControlContext(pd, false);
444:
445: // Reuse existing ACC
446:
447: this .context = pd;
448: this .combiner = null;
449: this .isPrivileged = false;
450:
451: return this ;
452: }
453:
454: private AccessControlContext goCombiner(ProtectionDomain[] current,
455: AccessControlContext assigned) {
456:
457: // the assigned ACC's combiner is not null --
458: // let the combiner do its thing
459:
460: // XXX we could add optimizations to 'current' here ...
461:
462: if (getDebug() != null) {
463: debug.println("AccessControlContext invoking the Combiner");
464: }
465:
466: // No need to clone current and assigned.context
467: // combine() will not update them
468: ProtectionDomain[] combinedPds = assigned.combiner.combine(
469: current, assigned.context);
470:
471: // return new AccessControlContext(combinedPds, assigned.combiner);
472:
473: // Reuse existing ACC
474: this .context = combinedPds;
475: this .combiner = assigned.combiner;
476: this .isPrivileged = false;
477:
478: return this ;
479: }
480:
481: /**
482: * Checks two AccessControlContext objects for equality.
483: * Checks that <i>obj</i> is
484: * an AccessControlContext and has the same set of ProtectionDomains
485: * as this context.
486: * <P>
487: * @param obj the object we are testing for equality with this object.
488: * @return true if <i>obj</i> is an AccessControlContext, and has the
489: * same set of ProtectionDomains as this context, false otherwise.
490: */
491: public boolean equals(Object obj) {
492: if (obj == this )
493: return true;
494:
495: if (!(obj instanceof AccessControlContext))
496: return false;
497:
498: AccessControlContext that = (AccessControlContext) obj;
499:
500: if (context == null) {
501: return (that.context == null);
502: }
503:
504: if (that.context == null)
505: return false;
506:
507: if (!(this .containsAllPDs(that) && that.containsAllPDs(this )))
508: return false;
509:
510: if (this .combiner == null)
511: return (that.combiner == null);
512:
513: if (that.combiner == null)
514: return false;
515:
516: if (!this .combiner.equals(that.combiner))
517: return false;
518:
519: return true;
520: }
521:
522: private boolean containsAllPDs(AccessControlContext that) {
523: boolean match = false;
524: //
525: // ProtectionDomains within an ACC currently cannot be null
526: // and this is enforced by the constructor and the various
527: // optimize methods. However, historically this logic made attempts
528: // to support the notion of a null PD and therefore this logic continues
529: // to support that notion.
530: ProtectionDomain this Pd;
531: for (int i = 0; i < context.length; i++) {
532: match = false;
533: if ((this Pd = context[i]) == null) {
534: for (int j = 0; (j < that.context.length) && !match; j++) {
535: match = (that.context[j] == null);
536: }
537: } else {
538: Class this PdClass = this Pd.getClass();
539: ProtectionDomain thatPd;
540: for (int j = 0; (j < that.context.length) && !match; j++) {
541: thatPd = that.context[j];
542:
543: // Class check required to avoid PD exposure (4285406)
544: match = (thatPd != null
545: && this PdClass == thatPd.getClass() && this Pd
546: .equals(thatPd));
547: }
548: }
549: if (!match)
550: return false;
551: }
552: return match;
553: }
554:
555: /**
556: * Returns the hash code value for this context. The hash code
557: * is computed by exclusive or-ing the hash code of all the protection
558: * domains in the context together.
559: *
560: * @return a hash code value for this context.
561: */
562:
563: public int hashCode() {
564: int hashCode = 0;
565:
566: if (context == null)
567: return hashCode;
568:
569: for (int i = 0; i < context.length; i++) {
570: if (context[i] != null)
571: hashCode ^= context[i].hashCode();
572: }
573: return hashCode;
574: }
575: }
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