JDK8/Java8源码在线阅读
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* accompanied this code).
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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},
* that is equivalent to the {@code checkPermission} method
* in the AccessController class, with one difference: The AccessControlContext
* {@code checkPermission} 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} method.
* The {@code getContext} 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} 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[];
// isPrivileged and isAuthorized are referenced by the VM - do not remove
// or change their names
private boolean isPrivileged;
private boolean isAuthorized = false;
// Note: This field is directly used by the virtual machine
// native codes. Don't touch it.
private AccessControlContext privilegedContext;
private DomainCombiner combiner = null;
// limited privilege scope
private Permission permissions[];
private AccessControlContext parent;
private boolean isWrapped;
// is constrained by limited privilege scope?
private boolean isLimited;
private ProtectionDomain limitedContext[];
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 array 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.
* @throws NullPointerException if {@code context} is {@code null}
*/
public AccessControlContext(ProtectionDomain context[])
{
if (context.length == 0) {
this.context = null;
} else if (context.length == 1) {
if (context[0] != null) {
this.context = context.clone();
} else {
this.context = null;
}
} else {
List<ProtectionDomain> 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]);
}
if (!v.isEmpty()) {
this.context = new ProtectionDomain[v.size()];
this.context = v.toArray(this.context);
}
}
}
/**
* Create a new {@code AccessControlContext} with the given
* {@code AccessControlContext} and {@code DomainCombiner}.
* This constructor associates the provided
* {@code DomainCombiner} with the provided
* {@code AccessControlContext}.
*
* <p>
*
* @param acc the {@code AccessControlContext} associated
* with the provided {@code DomainCombiner}.
*
* @param combiner the {@code DomainCombiner} to be associated
* with the provided {@code AccessControlContext}.
*
* @exception NullPointerException if the provided
* {@code context} is {@code null}.
*
* @exception SecurityException if a security manager is installed and the
* caller does not have the "createAccessControlContext"
* {@link SecurityPermission}
* @since 1.3
*/
public AccessControlContext(AccessControlContext acc,
DomainCombiner combiner) {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(SecurityConstants.CREATE_ACC_PERMISSION);
this.isAuthorized = true;
}
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
*
* This "argument wrapper" context will be passed as the actual context
* parameter on an internal doPrivileged() call used in the implementation.
*/
AccessControlContext(ProtectionDomain caller, DomainCombiner combiner,
AccessControlContext parent, AccessControlContext context,
Permission[] perms)
{
/*
* Combine the domains from the doPrivileged() context into our
* wrapper context, if necessary.
*/
ProtectionDomain[] callerPDs = null;
if (caller != null) {
callerPDs = new ProtectionDomain[] { caller };
}
if (context != null) {
if (combiner != null) {
this.context = combiner.combine(callerPDs, context.context);
} else {
this.context = combine(callerPDs, context.context);
}
} else {
/*
* Call combiner even if there is seemingly nothing to combine.
*/
if (combiner != null) {
this.context = combiner.combine(callerPDs, null);
} else {
this.context = combine(callerPDs, null);
}
}
this.combiner = combiner;
Permission[] tmp = null;
if (perms != null) {
tmp = new Permission[perms.length];
for (int i=0; i < perms.length; i++) {
if (perms[i] == null) {
throw new NullPointerException("permission can't be null");
}
/*
* An AllPermission argument is equivalent to calling
* doPrivileged() without any limit permissions.
*/
if (perms[i].getClass() == AllPermission.class) {
parent = null;
}
tmp[i] = perms[i];
}
}
/*
* For a doPrivileged() with limited privilege scope, initialize
* the relevant fields.
*
* The limitedContext field contains the union of all domains which
* are enclosed by this limited privilege scope. In other words,
* it contains all of the domains which could potentially be checked
* if none of the limiting permissions implied a requested permission.
*/
if (parent != null) {
this.limitedContext = combine(parent.context, parent.limitedContext);
this.isLimited = true;
this.isWrapped = true;
this.permissions = tmp;
this.parent = parent;
this.privilegedContext = context; // used in checkPermission2()
}
this.isAuthorized = true;
}
/**
* package private constructor for AccessController.getContext()
*/
AccessControlContext(ProtectionDomain context[],
boolean isPrivileged)
{
this.context = context;
this.isPrivileged = isPrivileged;
this.isAuthorized = true;
}
/**
* Constructor for JavaSecurityAccess.doIntersectionPrivilege()
*/
AccessControlContext(ProtectionDomain[] context,
AccessControlContext privilegedContext)
{
this.context = context;
this.privilegedContext = privilegedContext;
this.isPrivileged = true;
}
/**
* Returns this context's context.
*/
ProtectionDomain[] getContext() {
return context;
}
/**
* 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} associated with this
* {@code AccessControlContext}.
*
* <p>
*
* @return the {@code DomainCombiner} associated with this
* {@code AccessControlContext}, or {@code null}
* if there is none.
*
* @exception SecurityException if a security manager is installed and
* the caller does not have the "getDomainCombiner"
* {@link SecurityPermission}
* @since 1.3
*/
public DomainCombiner getDomainCombiner() {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(SecurityConstants.GET_COMBINER_PERMISSION);
}
return getCombiner();
}
/**
* package private for AccessController
*/
DomainCombiner getCombiner() {
return combiner;
}
boolean isAuthorized() {
return isAuthorized;
}
/**
* 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.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) {
checkPermission2(perm);
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.dumpStack();
final ProtectionDomain pd = context[i];
final Debug db = debug;
AccessController.doPrivileged (new PrivilegedAction<Void>() {
public Void 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);
}
checkPermission2(perm);
}
/*
* Check the domains associated with the limited privilege scope.
*/
private void checkPermission2(Permission perm) {
if (!isLimited) {
return;
}
/*
* Check the doPrivileged() context parameter, if present.
*/
if (privilegedContext != null) {
privilegedContext.checkPermission2(perm);
}
/*
* Ignore the limited permissions and parent fields of a wrapper
* context since they were already carried down into the unwrapped
* context.
*/
if (isWrapped) {
return;
}
/*
* Try to match any limited privilege scope.
*/
if (permissions != null) {
Class<?> permClass = perm.getClass();
for (int i=0; i < permissions.length; i++) {
Permission limit = permissions[i];
if (limit.getClass().equals(permClass) && limit.implies(perm)) {
return;
}
}
}
/*
* Check the limited privilege scope up the call stack or the inherited
* parent thread call stack of this ACC.
*/
if (parent != null) {
/*
* As an optimization, if the parent context is the inherited call
* stack context from a parent thread then checking the protection
* domains of the parent context is redundant since they have
* already been merged into the child thread's context by
* optimize(). When parent is set to an inherited context this
* context was not directly created by a limited scope
* doPrivileged() and it does not have its own limited permissions.
*/
if (permissions == null) {
parent.checkPermission2(perm);
} else {
parent.checkPermission(perm);
}
}
}
/**
* Take the stack-based context (this) and combine it with the
* privileged or inherited context, if need be. Any limited
* privilege scope is flagged regardless of whether the assigned
* context comes from an immediately enclosing limited doPrivileged().
* The limited privilege scope can indirectly flow from the inherited
* parent thread or an assigned context previously captured by getContext().
*/
AccessControlContext optimize() {
// the assigned (privileged or inherited) context
AccessControlContext acc;
DomainCombiner combiner = null;
AccessControlContext parent = null;
Permission[] permissions = null;
if (isPrivileged) {
acc = privilegedContext;
if (acc != null) {
/*
* If the context is from a limited scope doPrivileged() then
* copy the permissions and parent fields out of the wrapper
* context that was created to hold them.
*/
if (acc.isWrapped) {
permissions = acc.permissions;
parent = acc.parent;
}
}
} else {
acc = AccessController.getInheritedAccessControlContext();
if (acc != null) {
/*
* If the inherited context is constrained by a limited scope
* doPrivileged() then set it as our parent so we will process
* the non-domain-related state.
*/
if (acc.isLimited) {
parent = acc;
}
}
}
// 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);
ProtectionDomain[] assigned = (skipAssigned) ? null : acc.context;
ProtectionDomain[] pd;
// if there is no enclosing limited privilege scope on the stack or
// inherited from a parent thread
boolean skipLimited = ((acc == null || !acc.isWrapped) && parent == null);
if (acc != null && acc.combiner != null) {
// let the assigned acc's combiner do its thing
if (getDebug() != null) {
debug.println("AccessControlContext invoking the Combiner");
}
// No need to clone current and assigned.context
// combine() will not update them
combiner = acc.combiner;
pd = combiner.combine(context, assigned);
} else {
if (skipStack) {
if (skipAssigned) {
calculateFields(acc, parent, permissions);
return this;
} else if (skipLimited) {
return acc;
}
} else if (assigned != null) {
if (skipLimited) {
// optimization: if there is a single stack domain and
// that domain is already in the assigned context; no
// need to combine
if (context.length == 1 && context[0] == assigned[0]) {
return acc;
}
}
}
pd = combine(context, assigned);
if (skipLimited && !skipAssigned && pd == assigned) {
return acc;
} else if (skipAssigned && pd == context) {
calculateFields(acc, parent, permissions);
return this;
}
}
// Reuse existing ACC
this.context = pd;
this.combiner = combiner;
this.isPrivileged = false;
calculateFields(acc, parent, permissions);
return this;
}
/*
* Combine the current (stack) and assigned domains.
*/
private static ProtectionDomain[] combine(ProtectionDomain[]current,
ProtectionDomain[] assigned) {
// current could be null if only system code is on the stack;
// in that case, ignore the stack context
boolean skipStack = (current == null);
// assigned could be null if only system code was involved;
// in that case, ignore the assigned context
boolean skipAssigned = (assigned == null);
int slen = (skipStack) ? 0 : current.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 current;
}
int n = (skipAssigned) ? 0 : assigned.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(assigned, 0, pd, 0, n);
}
// now add the stack context domains, discarding nulls and duplicates
outer:
for (int i = 0; i < slen; i++) {
ProtectionDomain sd = current[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 == assigned.length) {
return assigned;
} else if (skipAssigned && n == slen) {
return current;
}
ProtectionDomain tmp[] = new ProtectionDomain[n];
System.arraycopy(pd, 0, tmp, 0, n);
pd = tmp;
}
return pd;
}
/*
* Calculate the additional domains that could potentially be reached via
* limited privilege scope. Mark the context as being subject to limited
* privilege scope unless the reachable domains (if any) are already
* contained in this domain context (in which case any limited
* privilege scope checking would be redundant).
*/
private void calculateFields(AccessControlContext assigned,
AccessControlContext parent, Permission[] permissions)
{
ProtectionDomain[] parentLimit = null;
ProtectionDomain[] assignedLimit = null;
ProtectionDomain[] newLimit;
parentLimit = (parent != null)? parent.limitedContext: null;
assignedLimit = (assigned != null)? assigned.limitedContext: null;
newLimit = combine(parentLimit, assignedLimit);
if (newLimit != null) {
if (context == null || !containsAllPDs(newLimit, context)) {
this.limitedContext = newLimit;
this.permissions = permissions;
this.parent = parent;
this.isLimited = true;
}
}
}
/**
* 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 (!equalContext(that))
return false;
if (!equalLimitedContext(that))
return false;
return true;
}
/*
* Compare for equality based on state that is free of limited
* privilege complications.
*/
private boolean equalContext(AccessControlContext that) {
if (!equalPDs(this.context, that.context))
return false;
if (this.combiner == null && that.combiner != null)
return false;
if (this.combiner != null && !this.combiner.equals(that.combiner))
return false;
return true;
}
private boolean equalPDs(ProtectionDomain[] a, ProtectionDomain[] b) {
if (a == null) {
return (b == null);
}
if (b == null)
return false;
if (!(containsAllPDs(a, b) && containsAllPDs(b, a)))
return false;
return true;
}
/*
* Compare for equality based on state that is captured during a
* call to AccessController.getContext() when a limited privilege
* scope is in effect.
*/
private boolean equalLimitedContext(AccessControlContext that) {
if (that == null)
return false;
/*
* If neither instance has limited privilege scope then we're done.
*/
if (!this.isLimited && !that.isLimited)
return true;
/*
* If only one instance has limited privilege scope then we're done.
*/
if (!(this.isLimited && that.isLimited))
return false;
/*
* Wrapped instances should never escape outside the implementation
* this class and AccessController so this will probably never happen
* but it only makes any sense to compare if they both have the same
* isWrapped state.
*/
if ((this.isWrapped && !that.isWrapped) ||
(!this.isWrapped && that.isWrapped)) {
return false;
}
if (this.permissions == null && that.permissions != null)
return false;
if (this.permissions != null && that.permissions == null)
return false;
if (!(this.containsAllLimits(that) && that.containsAllLimits(this)))
return false;
/*
* Skip through any wrapped contexts.
*/
AccessControlContext thisNextPC = getNextPC(this);
AccessControlContext thatNextPC = getNextPC(that);
/*
* The protection domains and combiner of a privilegedContext are
* not relevant because they have already been included in the context
* of this instance by optimize() so we only care about any limited
* privilege state they may have.
*/
if (thisNextPC == null && thatNextPC != null && thatNextPC.isLimited)
return false;
if (thisNextPC != null && !thisNextPC.equalLimitedContext(thatNextPC))
return false;
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