001: /*
002: * @(#)AccessControlContext.java 1.40 06/10/10
003: *
004: * Copyright 1990-2006 Sun Microsystems, Inc. All Rights Reserved.
005: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
006: *
007: * This program is free software; you can redistribute it and/or
008: * modify it under the terms of the GNU General Public License version
009: * 2 only, as published by the Free Software Foundation.
010: *
011: * This program is distributed in the hope that it will be useful, but
012: * WITHOUT ANY WARRANTY; without even the implied warranty of
013: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014: * General Public License version 2 for more details (a copy is
015: * included at /legal/license.txt).
016: *
017: * You should have received a copy of the GNU General Public License
018: * version 2 along with this work; if not, write to the Free Software
019: * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
020: * 02110-1301 USA
021: *
022: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
023: * Clara, CA 95054 or visit www.sun.com if you need additional
024: * information or have any questions.
025: *
026: */
027:
028: package java.security;
029:
030: import java.util.Vector;
031: import sun.security.util.Debug;
032: import sun.security.util.SecurityConstants;
033:
034: /**
035: * An AccessControlContext is used to make system resource access decisions
036: * based on the context it encapsulates.
037: *
038: * <p>More specifically, it encapsulates a context and
039: * has a single method, <code>checkPermission</code>,
040: * that is equivalent to the <code>checkPermission</code> method
041: * in the AccessController class, with one difference: The AccessControlContext
042: * <code>checkPermission</code> method makes access decisions based on the
043: * context it encapsulates,
044: * rather than that of the current execution thread.
045: *
046: * <p>Thus, the purpose of AccessControlContext is for those situations where
047: * a security check that should be made within a given context
048: * actually needs to be done from within a
049: * <i>different</i> context (for example, from within a worker thread).
050: *
051: * <p> An AccessControlContext is created by calling the
052: * <code>AccessController.getContext</code> method.
053: * The <code>getContext</code> method takes a "snapshot"
054: * of the current calling context, and places
055: * it in an AccessControlContext object, which it returns. A sample call is
056: * the following:
057: *
058: * <pre>
059: *
060: * AccessControlContext acc = AccessController.getContext()
061: *
062: * </pre>
063: *
064: * <p>
065: * Code within a different context can subsequently call the
066: * <code>checkPermission</code> method on the
067: * previously-saved AccessControlContext object. A sample call is the
068: * following:
069: *
070: * <pre>
071: *
072: * acc.checkPermission(permission)
073: *
074: * </pre>
075: *
076: * @see AccessController
077: *
078: * @author Roland Schemers
079: */
080:
081: public final class AccessControlContext {
082:
083: private ProtectionDomain context[];
084: private boolean isPrivileged;
085: private AccessControlContext privilegedContext;
086: private DomainCombiner combiner = null;
087:
088: private static boolean debugInit = false;
089: private static Debug debug = null;
090:
091: static Debug getDebug() {
092: if (debugInit)
093: return debug;
094: else {
095: if (Policy.isSet()) {
096: debug = Debug.getInstance("access");
097: debugInit = true;
098: }
099: return debug;
100: }
101: }
102:
103: /**
104: * Create an AccessControlContext with the given set of ProtectionDomains.
105: * Context must not be null. Duplicate domains will be removed from the
106: * context.
107: *
108: * @param context the ProtectionDomains associated with this context.
109: */
110:
111: public AccessControlContext(ProtectionDomain context[]) {
112: if (context.length == 0) {
113: this .context = null;
114: } else if (context.length == 1) {
115: this .context = (ProtectionDomain[]) context.clone();
116: } else {
117: Vector v = new Vector(context.length);
118: for (int i = 0; i < context.length; i++) {
119: if ((context[i] != null) && (!v.contains(context[i])))
120: v.addElement(context[i]);
121: }
122: this .context = new ProtectionDomain[v.size()];
123: v.copyInto(this .context);
124: }
125: }
126:
127: /**
128: * Create a new <code>AccessControlContext</code> with the given
129: * <code>AccessControlContext</code> and <code>DomainCombiner</code>.
130: * This constructor associates the provided
131: * <code>DomainCombiner</code> with the provided
132: * <code>AccessControlContext</code>.
133: *
134: * <p>
135: *
136: * @param acc the <code>AccessControlContext</code> associated
137: * with the provided <code>DomainCombiner</code>. <p>
138: *
139: * @param combiner the <code>DomainCombiner</code> to be associated
140: * with the provided <code>AccessControlContext</code>.
141: *
142: * @exception NullPointerException if the provided
143: * <code>context</code> is <code>null</code>. <p>
144: *
145: * @exception SecurityException if the caller does not have permission
146: * to invoke this constructor.
147: */
148: public AccessControlContext(AccessControlContext acc,
149: DomainCombiner combiner) {
150:
151: SecurityManager sm = System.getSecurityManager();
152: if (sm != null) {
153: sm.checkPermission(SecurityConstants.CREATE_ACC_PERMISSION);
154: }
155:
156: if (acc == null) {
157: throw new NullPointerException(
158: "null AccessControlContext was provided");
159: }
160:
161: this .context = acc.context;
162:
163: // we do not need to run the combine method on the
164: // provided ACC. it was already "combined" when the
165: // context was originally retrieved.
166: //
167: // at this point in time, we simply throw away the old
168: // combiner and use the newly provided one.
169: this .combiner = combiner;
170: }
171:
172: private AccessControlContext(ProtectionDomain context[],
173: DomainCombiner combiner) {
174: this .context = (ProtectionDomain[]) context.clone();
175: this .combiner = combiner;
176: }
177:
178: /**
179: * package private constructor for AccessController
180: */
181:
182: AccessControlContext(ProtectionDomain context[],
183: boolean isPrivileged, AccessControlContext privilegedContext) {
184: this .context = context;
185: this .isPrivileged = isPrivileged;
186: this .privilegedContext = privilegedContext;
187: }
188:
189: private AccessControlContext(ProtectionDomain context[],
190: boolean isPrivileged) {
191: this (context, isPrivileged, null);
192: }
193:
194: /**
195: * Returns true if this context is privileged.
196: */
197: boolean isPrivileged() {
198: return isPrivileged;
199:
200: }
201:
202: /**
203: * Get the <code>DomainCombiner</code> associated with this
204: * <code>AccessControlContext</code>.
205: *
206: * <p>
207: *
208: * @return the <code>DomainCombiner</code> associated with this
209: * <code>AccessControlContext</code>, or <code>null</code>
210: * if there is none.
211: *
212: * @exception SecurityException if the caller does not have permission
213: * to get the <code>DomainCombiner</code> associated with this
214: * <code>AccessControlContext</code>.
215: */
216: public DomainCombiner getDomainCombiner() {
217:
218: SecurityManager sm = System.getSecurityManager();
219: if (sm != null) {
220: sm
221: .checkPermission(SecurityConstants.GET_COMBINER_PERMISSION);
222: }
223: return combiner;
224: }
225:
226: /**
227: * Determines whether the access request indicated by the
228: * specified permission should be allowed or denied, based on
229: * the security policy currently in effect, and the context in
230: * this object.
231: * <p>
232: * This method quietly returns if the access request
233: * is permitted, or throws a suitable AccessControlException otherwise.
234: *
235: * @param perm the requested permission.
236: *
237: * @exception AccessControlException if the specified permission
238: * is not permitted, based on the current security policy and the
239: * context encapsulated by this object.
240: * @exception NullPointerException if the permission to check for is null.
241: */
242: public void checkPermission(Permission perm)
243: throws AccessControlException {
244: if (perm == null) {
245: throw new NullPointerException("permission can't be null");
246: }
247: if (getDebug() != null) {
248: if (Debug.isOn("stack"))
249: Thread.currentThread().dumpStack();
250: if (Debug.isOn("domain")) {
251: if (context == null) {
252: debug.println("domain (context is null)");
253: } else {
254: for (int i = 0; i < context.length; i++) {
255: debug.println("domain " + i + " " + context[i]);
256: }
257: }
258: }
259: }
260:
261: /*
262: * iterate through the ProtectionDomains in the context.
263: * Stop at the first one that doesn't allow the
264: * requested permission (throwing an exception).
265: *
266: */
267:
268: /* if ctxt is null, all we had on the stack were system domains,
269: or the first domain was a Privileged system domain. This
270: is to make the common case for system code very fast */
271:
272: if (context == null)
273: return;
274:
275: for (int i = 0; i < context.length; i++) {
276: if (context[i] != null && !context[i].implies(perm)) {
277: if (debug != null) {
278: debug.println("access denied " + perm);
279: if (Debug.isOn("failure")) {
280: Thread.currentThread().dumpStack();
281: final ProtectionDomain pd = context[i];
282: final Debug db = debug;
283: AccessController
284: .doPrivileged(new PrivilegedAction() {
285: public Object run() {
286: db
287: .println("domain that failed "
288: + pd);
289: return null;
290: }
291: });
292: }
293: }
294: throw new AccessControlException("access denied "
295: + perm, perm);
296: }
297: }
298:
299: // allow if all of them allowed access
300: if (debug != null)
301: debug.println("access allowed " + perm);
302:
303: return;
304: }
305:
306: /**
307: * Take the stack-based context (this) and combine it with the
308: * privileged or inherited context, if need be.
309: */
310: AccessControlContext optimize() {
311: // the assigned (privileged or inherited) context
312: AccessControlContext acc;
313: if (isPrivileged) {
314: acc = privilegedContext;
315: } else {
316: acc = AccessController.getInheritedAccessControlContext();
317: }
318:
319: // this.context could be null if only system code is on the stack;
320: // in that case, ignore the stack context
321: boolean skipStack = (context == null);
322:
323: // acc.context could be null if only system code was involved;
324: // in that case, ignore the assigned context
325: boolean skipAssigned = (acc == null || acc.context == null);
326:
327: // optimization: if neither have contexts; return acc if possible
328: // rather than this, because acc might have a combiner
329: if (skipAssigned && skipStack) {
330: return (acc != null) ? acc : this ;
331: }
332:
333: if (acc != null && acc.combiner != null) {
334: // let the assigned acc's combiner do its thing
335: return goCombiner(context, acc);
336: }
337:
338: // optimization: if there is no stack context; there is no reason
339: // to compress the assigned context, it already is compressed
340: if (skipStack) {
341: return acc;
342: }
343:
344: int slen = context.length;
345:
346: // optimization: if there is no assigned context and the stack length
347: // is less then or equal to two; there is no reason to compress the
348: // stack context, it already is
349: if (skipAssigned && slen <= 2) {
350: return this ;
351: }
352:
353: // optimization: if there is a single stack domain and that domain
354: // is already in the assigned context; no need to combine
355: if ((slen == 1) && (context[0] == acc.context[0])) {
356: return acc;
357: }
358:
359: int n = (skipAssigned) ? 0 : acc.context.length;
360:
361: // now we combine both of them, and create a new context
362: ProtectionDomain pd[] = new ProtectionDomain[slen + n];
363:
364: // first copy in the assigned context domains, no need to compress
365: if (!skipAssigned) {
366: System.arraycopy(acc.context, 0, pd, 0, n);
367: }
368:
369: // now add the stack context domains, discarding nulls and duplicates
370: outer: for (int i = 0; i < context.length; i++) {
371: ProtectionDomain sd = context[i];
372: if (sd != null) {
373: for (int j = 0; j < n; j++) {
374: if (sd == pd[j]) {
375: continue outer;
376: }
377: }
378: pd[n++] = sd;
379: }
380: }
381:
382: // if length isn't equal, we need to shorten the array
383: if (n != pd.length) {
384: // optimization: if we didn't really combine anything
385: if (!skipAssigned && n == acc.context.length) {
386: return acc;
387: } else if (skipAssigned && n == slen) {
388: return this ;
389: }
390: ProtectionDomain tmp[] = new ProtectionDomain[n];
391: System.arraycopy(pd, 0, tmp, 0, n);
392: pd = tmp;
393: }
394:
395: return new AccessControlContext(pd, false);
396: }
397:
398: private AccessControlContext goCombiner(ProtectionDomain[] current,
399: AccessControlContext assigned) {
400:
401: // the assigned ACC's combiner is not null --
402: // let the combiner do its thing
403:
404: // We could add optimizations to 'current' here ...
405:
406: if (getDebug() != null) {
407: debug.println("AccessControlContext invoking the Combiner");
408: }
409:
410: ProtectionDomain[] combinedPds = assigned.combiner
411: .combine(current == null ? null
412: : (ProtectionDomain[]) current.clone(),
413: assigned.context == null ? null
414: : (ProtectionDomain[]) assigned.context
415: .clone());
416:
417: // return the new ACC
418: return new AccessControlContext(combinedPds, assigned.combiner);
419: }
420:
421: /**
422: * Checks two AccessControlContext objects for equality.
423: * Checks that <i>obj</i> is
424: * an AccessControlContext and has the same set of ProtectionDomains
425: * as this context.
426: * <P>
427: * @param obj the object we are testing for equality with this object.
428: * @return true if <i>obj</i> is an AccessControlContext, and has the
429: * same set of ProtectionDomains as this context, false otherwise.
430: */
431: public boolean equals(Object obj) {
432: if (obj == this )
433: return true;
434:
435: if (!(obj instanceof AccessControlContext))
436: return false;
437:
438: AccessControlContext that = (AccessControlContext) obj;
439:
440: if (context == null) {
441: return (that.context == null);
442: }
443:
444: if (that.context == null)
445: return false;
446:
447: if (!(this .containsAllPDs(that) && that.containsAllPDs(this )))
448: return false;
449:
450: if (this .combiner == null)
451: return (that.combiner == null);
452:
453: if (that.combiner == null)
454: return false;
455:
456: if (!this .combiner.equals(that.combiner))
457: return false;
458:
459: return true;
460:
461: }
462:
463: private boolean containsAllPDs(AccessControlContext that) {
464: boolean match = false;
465: //
466: // ProtectionDomains within an ACC currently cannot be null
467: // and this is enforced by the contructor and the various
468: // optimize methods. However, historically this logic made attempts
469: // to support the notion of a null PD and therefore this logic continues
470: // to support that notion.
471: for (int i = 0; i < context.length; i++) {
472: match = false;
473: if (context[i] == null) {
474: for (int j = 0; (j < that.context.length) && !match; j++) {
475: match = (that.context[j] == null);
476: }
477: } else {
478: for (int j = 0; (j < that.context.length) && !match; j++) {
479: if (that.context[j] != null) {
480: match = ((context[i].getClass() == that.context[j]
481: .getClass()) && (context[i]
482: .equals(that.context[j])));
483: }
484: }
485: }
486: if (!match)
487: return false;
488: }
489: return match;
490: }
491:
492: /**
493: * Returns the hash code value for this context. The hash code
494: * is computed by exclusive or-ing the hash code of all the protection
495: * domains in the context together.
496: *
497: * @return a hash code value for this context.
498: */
499:
500: public int hashCode() {
501: int hashCode = 0;
502:
503: if (context == null)
504: return hashCode;
505:
506: for (int i = 0; i < context.length; i++) {
507: if (context[i] != null)
508: hashCode ^= context[i].hashCode();
509: }
510: return hashCode;
511: }
512: }
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