This is an abstract class for representing the system security policy for
* a Java application environment (specifying which permissions are available
* for code from various sources). That is, the security policy is represented
* by a Policy subclass providing an implementation of the abstract
* methods in this Policy class.
There is only one Policy object in effect at any given time.
*
The source location for the policy information utilized by the
* Policy object is up to the Policy implementation.
* The policy configuration may be stored, for example, as a flat ASCII file, as
* a serialized binary file of the Policy class, or as a database.
*
The currently-installed Policy object can be obtained by
* calling the getPolicy() method, and it can be changed by a call
* to the setPolicy() method (by code with permission to reset the
* Policy).
The refresh() method causes the policy object to refresh /
* reload its current configuration.
This is implementation-dependent. For example, if the policy object stores
* its policy in configuration files, calling refresh() will cause
* it to re-read the configuration policy files. The refreshed policy may not
* have an effect on classes in a particular {@link ProtectionDomain}. This is
* dependent on the Policy provider's implementation of the
* implies() method and the {@link PermissionCollection} caching
* strategy.
The default Policy implementation can be changed by setting
* the value of the "policy.provider" security property (in the
* Java security properties file) to the fully qualified name of the desired
* Policy implementation class. The Java security properties file
* is located in the file named <JAVA_HOME>/lib/security/java.security
* , where <JAVA_HOME> refers to the directory where the
* SDK was installed.
IMPLEMENTATION NOTE: This implementation attempts to read the
* System property named policy.provider to find the concrete
* implementation of the Policy. If/when this fails, it falls back
* to a default implementation, which allows everything.
*
* @author Mark Benvenuto
* @see CodeSource
* @see PermissionCollection
* @see SecureClassLoader
* @since 1.2
*/
public abstract class Policy
{
private static Policy currentPolicy;
/** Map of ProtectionDomains to PermissionCollections for this instance. */
private Map pd2pc = null;
/** Constructs a new Policy object. */
public Policy()
{
}
/**
* Returns the installed Policy object. This value should not be
* cached, as it may be changed by a call to setPolicy(). This
* method first calls {@link SecurityManager#checkPermission(Permission)} with
* a SecurityPermission("getPolicy") permission to ensure it's ok
* to get the Policy object.
*
* @return the installed Policy.
* @throws SecurityException if a security manager exists and its
* checkPermission() method doesn't allow getting the
* Policy object.
* @see SecurityManager#checkPermission(Permission)
* @see #setPolicy(Policy)
*/
public static Policy getPolicy()
{
SecurityManager sm = System.getSecurityManager();
if (sm != null)
sm.checkPermission(new SecurityPermission("getPolicy"));
return getCurrentPolicy();
}
/**
* Sets the system-wide Policy object. This method first calls
* {@link SecurityManager#checkPermission(Permission)} with a
* SecurityPermission("setPolicy") permission to ensure it's ok
* to set the Policy.
*
* @param policy the new system Policy object.
* @throws SecurityException if a security manager exists and its
* checkPermission() method doesn't allow setting the
* Policy.
* @see SecurityManager#checkPermission(Permission)
* @see #getPolicy()
*/
public static void setPolicy(Policy policy)
{
SecurityManager sm = System.getSecurityManager();
if (sm != null)
sm.checkPermission(new SecurityPermission("setPolicy"));
setup(policy);
currentPolicy = policy;
}
private static void setup(final Policy policy)
{
if (policy.pd2pc == null)
policy.pd2pc = Collections.synchronizedMap(new LinkedHashMap());
ProtectionDomain pd = policy.getClass().getProtectionDomain();
if (pd.getCodeSource() != null)
{
PermissionCollection pc = null;
if (currentPolicy != null)
pc = currentPolicy.getPermissions(pd);
if (pc == null) // assume it has all
{
pc = new Permissions();
pc.add(new AllPermission());
}
policy.pd2pc.put(pd, pc); // add the mapping pd -> pc
}
}
/**
* Ensures/forces loading of the configured policy provider, while bypassing
* the {@link SecurityManager} checks for "getPolicy" security
* permission. Needed by {@link ProtectionDomain}.
*/
static Policy getCurrentPolicy()
{
// FIXME: The class name of the Policy provider should really be sourced
// from the "java.security" configuration file. For now, just hard-code
// a stub implementation.
if (currentPolicy == null)
{
String pp = System.getProperty ("policy.provider");
if (pp != null)
try
{
currentPolicy = (Policy) Class.forName(pp).newInstance();
}
catch (Exception e)
{
// Ignored.
}
if (currentPolicy == null)
currentPolicy = new gnu.java.security.provider.DefaultPolicy();
}
return currentPolicy;
}
/**
* Tests if currentPolicy is not null,
* thus allowing clients to not force loading of any policy
* provider; needed by {@link ProtectionDomain}.
*/
static boolean isLoaded()
{
return currentPolicy != null;
}
/**
* Evaluates the global policy and returns a {@link PermissionCollection}
* object specifying the set of permissions allowed for code from the
* specified code source.
*
* @param codesource the {@link CodeSource} associated with the caller. This
* encapsulates the original location of the code (where the code came from)
* and the public key(s) of its signer.
* @return the set of permissions allowed for code from codesource according
* to the policy. The returned set of permissions must be a new mutable
* instance and it must support heterogeneous {@link Permission} types.
*/
public abstract PermissionCollection getPermissions(CodeSource codesource);
/**
* Evaluates the global policy and returns a {@link PermissionCollection}
* object specifying the set of permissions allowed given the characteristics
* of the protection domain.
*
* @param domain the {@link ProtectionDomain} associated with the caller.
* @return the set of permissions allowed for the domain according to the
* policy. The returned set of permissions must be a new mutable instance and
* it must support heterogeneous {@link Permission} types.
* @since 1.4
* @see ProtectionDomain
* @see SecureClassLoader
*/
public PermissionCollection getPermissions(ProtectionDomain domain)
{
if (domain == null)
return new Permissions();
if (pd2pc == null)
setup(this);
PermissionCollection result = (PermissionCollection) pd2pc.get(domain);
if (result != null)
{
Permissions realResult = new Permissions();
for (Enumeration e = result.elements(); e.hasMoreElements(); )
realResult.add((Permission) e.nextElement());
return realResult;
}
result = getPermissions(domain.getCodeSource());
if (result == null)
result = new Permissions();
PermissionCollection pc = domain.getPermissions();
if (pc != null)
for (Enumeration e = pc.elements(); e.hasMoreElements(); )
result.add((Permission) e.nextElement());
return result;
}
/**
* Evaluates the global policy for the permissions granted to the {@link
* ProtectionDomain} and tests whether the permission is granted.
*
* @param domain the {@link ProtectionDomain} to test.
* @param permission the {@link Permission} object to be tested for
* implication.
* @return true if permission is a proper subset of
* a permission granted to this {@link ProtectionDomain}.
* @since 1.4
* @see ProtectionDomain
*/
public boolean implies(ProtectionDomain domain, Permission permission)
{
if (pd2pc == null)
setup(this);
PermissionCollection pc = (PermissionCollection) pd2pc.get(domain);
if (pc != null)
return pc.implies(permission);
boolean result = false;
pc = getPermissions(domain);
if (pc != null)
{
result = pc.implies(permission);
pd2pc.put(domain, pc);
}
return result;
}
/**
* Refreshes/reloads the policy configuration. The behavior of this method
* depends on the implementation. For example, calling refresh on a file-based
* policy will cause the file to be re-read.
*/
public abstract void refresh();
}