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Restriction Management

Overview

The concept of restriction has been created as extension to JCR access control management in order to refine the effect of individual access control entries.

Quoting from JSR 283 section 16.6.2 Permissions:

[…] the permissions encompass the restrictions imposed by privileges, but also include any additional policy-internal refinements with effects too fine-grained to be exposed through privilege discovery. A common case may be to provide finer-grained access restrictions to individual properties or child nodes of the node to which the policy applies.

Furthermore, the restriction concept is aimed to allow for custom extensions of the default access control implementation to meet project specific needs without having to implement the common functionality provided by JCR.

Existing and potential examples of restrictions limiting the effect of a given access control entry during permission evaluation include:

  • set of node types
  • set of namespaces
  • name/path pattern
  • dedicated time frame
  • size of a value

The set of built-in restrictions available with Jackrabbit 2.x has been extended along with some extensions of the Jackrabbit API. This covers the public facing usage of restrictions i.e. access control management.

In addition, Oak provides its own internal restriction API that adds support for validation and permission evaluation.

Jackrabbit API

The Jackrabbit API adds the following extensions to JCR access control management to read and create entries with restrictions:

  • JackrabbitAccessControlList

    • getRestrictionNames() : returns the JCR names of the supported restrictions.
    • getRestrictionType(String restrictionName) : returns the property type of a given restriction.
    • addEntry(Principal, Privilege[], boolean, Map<String, Value>): the map contain the restrictions.
    • addEntry(Principal, Privilege[], boolean, Map<String, Value>, Map<String, Value[]>): allows to specify both single and multi-value restrictions (since Oak 1.0, Jackrabbit API 2.8)
  • JackrabbitAccessControlEntry

    • getRestrictionNames(): returns the JCR names of the restrictions present with this entry.
    • getRestriction(String restrictionName): returns the restriction as JCR value.
    • getRestrictions(String restrictionName): returns the restriction as array of JCR values (since Oak 1.0, Jackrabbit API 2.8).

Oak Restriction API

The following public interfaces are provided by Oak in the package org.apache.jackrabbit.oak.spi.security.authorization.restriction and provide support for pluggable restrictions both for access control management and the repository internal permission evaluation:

  • RestrictionProvider: interface to obtain restriction information needed for access control and permission management
  • Restriction: the restriction object as created using Jackrabbit access control API
  • RestrictionDefinition: the static definition of a supported restriction
  • RestrictionPattern: the processed restriction ready for permission evaluation

Default Implementation

Oak 1.0 provides the following base implementations:

  • AbstractRestrictionProvider: abstract base implementation of the provider interface.
  • RestrictionDefinitionImpl: default implementation of the RestrictionDefinition interface.
  • RestrictionImpl: default implementation of the Restriction interface.
  • CompositeRestrictionProvider: Allows aggregating multiple provider implementations (see Pluggability below).
  • CompositePattern: Allows aggregating multiple restriction patterns.

Changes wrt Jackrabbit 2.x

Apart from the fact that the internal Jackrabbit extension has been replaced by a public API, the restriction implementation in Oak differs from Jackrabbit 2.x as follows:

  • Separate restriction management API (see below) on the OAK level that simplifies plugging custom restrictions.
  • Changed node type definition for storing restrictions in the default implementation.
    • as of OAK restrictions are collected underneath a separate child node “rep:restrictions”
    • backwards compatible behavior for restrictions stored underneath the ACE node directly
  • Support for multi-valued restrictions (see JCR-3637, JCR-3641)
  • Validation of the restrictions is delegated to a dedicated commit hook
  • Restriction rep:glob limits the number of wildcard characters to 20
  • New restrictions rep:ntNames, rep:prefixes, rep:itemNames and rep:current

Built-in Restrictions

The following Restriction implementations are supported with the default Oak access control management:

Restriction Name Type Multi-Valued Mandatory Description Since
rep:glob String false false Single name, path or path pattern with ‘*’ wildcard(s), see below for details Oak 1.0
rep:ntNames Name true false Multivalued restriction to limit the effect to nodes of the specified primary node types (no nt inheritance) Oak 1.0
rep:prefixes String true false Multivalued restriction to limit the effect to item names that match the specified namespace prefixes (session level remapping not respected) Oak 1.0
rep:itemNames Name true false Multivalued restriction for property or node names Oak 1.3.8
rep:current String true false Multivalued restriction that limits the effect to a single level i.e. the target node where the access control entry takes effect and optionally all or a subset of it’s properties. There is no inheritance of the ACE effect to nodes in the subtree or their properties. Expanded JCR property names and namespace remapping not supported (see below for details) Oak 1.42.0
rep:glob - Details and Examples

For a nodePath /foo the following results can be expected for the different values of rep:glob.

Please note that the pattern is based on simple path concatenation and equally applies to either type of item (both nodes and properties). Consequently, the examples below need to be adjusted for the root node in order to produce the desired effect. In particular a path with two subsequent / is invalid and will never match any target item or path.

rep:glob Result
null i.e. no restriction: matches /foo and all descendants
"" matches node /foo only (no descendants, not even properties)

Examples including wildcard char:

rep:glob Result
* foo, siblings of foo and their descendants
/*cat all descendants of /foo whose paths end with ‘cat’
*cat all siblings and descendants of foo that have a name ending with ‘cat’
/*/cat all non-direct descendants of /foo named ‘cat’
/cat* all descendant of /foo that have the direct foo-descendant segment starting with ‘cat’
*/cat all descendants of /foo and foo’s siblings that have a name segment ‘cat’
cat/* all descendants of ‘/foocat’
/cat/* all descendants of ‘/foo/cat’
/*cat/* all descendants of /foo that have an intermediate segment ending with ‘cat’

Examples without wildcard char:

rep:glob Result
/cat ‘/foo/cat’ and all it’s descendants
/cat/ all descendants of ‘/foo/cat’
cat ‘/foocat’ and all it’s descendants
cat/ all descendants of ‘/foocat’

See also GlobPattern for implementation details and the GlobRestrictionTest in the oak-exercise module for training material.

rep:current - Details and Examples

The restriction limits the effect to the target node. The value of the restriction property defines which properties of the target node will in addition also match the restriction:

  • an empty value array will make the restriction matching the target node only (i.e. equivalent to rep:glob="").
  • an array of qualified property names will extend the effect of the restriction to properties of the target node that match the specified names.
  • the residual name * will match all properties of the target node.

For a nodePath /foo the following results can be expected for the different values of rep:current:

rep:current Result
[] /foo only, none of it’s properties
[*] /foo and all it’s properties
[jcr:primaryType] /foo and it’s jcr:primaryType property. no other property
[a, b, c] /foo and it’s properties a,b,c
Known Limitations
  • Due to the support of the residual name *, which isn’t a valid JCR name, the restriction rep:current is defined to be of PropertyType.STRING instead of PropertyType.NAME. Like the rep:glob restriction it will therefore not work with expanded JCR names or with remapped namespace prefixes.
  • In case of permission evaluation for a path pointing to a non-existing JCR item (see e.g. javax.jcr.Session#hasPermission(String, String)), it’s not possible to distinguish between nodes and properties. A best-effort approach is take to identify known properties like e.g. jcr:primaryType. For all other paths the implementation of the rep:current restrictions assumes that they point to non-existing nodes. Example: if rep:current is present with an ACE taking effect at /foo the call Session.hasPermission("/foo/non-existing",Session.ACTION_READ) will always return false because the restriction will interpret /foo/non-existing as a path pointing to a node.

Representation in the Repository

All restrictions defined by default in an Oak repository are stored as properties in a dedicated rep:restriction child node of the target access control entry node. Similarly, they are represented with the corresponding permission entry. The node type definition used to represent restriction content is as follows:

[rep:ACE]
  - rep:principalName (STRING) protected mandatory
  - rep:privileges (NAME) protected mandatory multiple
  - rep:nodePath (PATH) protected /* deprecated in favor of restrictions */
  - rep:glob (STRING) protected   /* deprecated in favor of restrictions */
  - * (UNDEFINED) protected       /* deprecated in favor of restrictions */
  + rep:restrictions (rep:Restrictions) = rep:Restrictions protected /* since oak 1.0 */

/**
 * @since oak 1.0
 */
[rep:Restrictions]
  - * (UNDEFINED) protected
  - * (UNDEFINED) protected multiple

Pluggability

The default security setup as present with Oak 1.0 is able to provide custom RestrictionProvider implementations and will automatically combine the different implementations using the CompositeRestrictionProvider.

In an OSGi setup the following steps are required in order to add an action provider implementation:

  • implement RestrictionProvider interface exposing your custom restriction(s).
  • make the provider implementation an OSGi service and make it available to the Oak repository.
  • make sure the RestrictionProvider is listed as required service with the SecurityProvider (see also Introduction)

Please make sure to consider the following recommendations when implementing a custom RestrictionProvider: - restrictions are part of the overall permission evaluation and thus may heavily impact overall read/write performance - the hashCode generation of the base implementation (RestrictionImpl.hashCode) relies on PropertyStateValue.hashCode, which includes the internal String representation, which is not optimal for binaries (see also OAK-5784)

Examples
Example RestrictionProvider

Simple example of a RestrictionProvider that defines a single time-based Restriction, which is expected to have 2 values defining a start and end date, which can then be used to allow or deny access within the given time frame.

@Component
@Service(RestrictionProvider.class)
public class MyRestrictionProvider extends AbstractRestrictionProvider {

    public MyRestrictionProvider() {
        super(supportedRestrictions());
    }

    private static Map<String, RestrictionDefinition> supportedRestrictions() {
        RestrictionDefinition dates = new RestrictionDefinitionImpl("dates", Type.DATES, false);
        return Collections.singletonMap(dates.getName(), dates);
    }

    //------------------------------------------------< RestrictionProvider >---

    @Override
    public RestrictionPattern getPattern(String oakPath, Tree tree) {
        if (oakPath != null) {
            PropertyState property = tree.getProperty("dates");
            if (property != null) {
                return DatePattern.create(property);
            }
        }
        return RestrictionPattern.EMPTY;
    }

    @Nonnull
    @Override
    public RestrictionPattern getPattern(@Nullable String oakPath, @Nonnull Set<Restriction> restrictions) {
        if (oakPath != null) {
            for (Restriction r : restrictions) {
                String name = r.getDefinition().getName();
                if ("dates".equals(name)) {
                    return DatePattern.create(r.getProperty());
                }
            }
        }
        return RestrictionPattern.EMPTY;
    }

    // TODO: implementing 'validateRestrictions(String oakPath, Tree aceTree)' would allow to make sure the property contains 2 date values.
}
Example RestrictionPattern

The time-based RestrictionPattern used by the example provider above.

class DatePattern implements RestrictionPattern {

    private final Date start;
    private final Date end;

    private DatePattern(@Nonnull Calendar start, @Nonnull Calendar end) {
        this.start = start.getTime();
        this.end = end.getTime();
    }

    static RestrictionPattern create(PropertyState timeProperty) {
        if (timeProperty.count() == 2) {
            return new DatePattern(
                    Conversions.convert(timeProperty.getValue(Type.DATE, 0), Type.DATE).toCalendar(),
                    Conversions.convert(timeProperty.getValue(Type.DATE, 1), Type.DATE).toCalendar()
            );
        } else {
            return RestrictionPattern.EMPTY;
        }
    }

    @Override
    public boolean matches(@Nonnull Tree tree, @Nullable PropertyState property) {
        return matches();
    }

    @Override
    public boolean matches(@Nonnull String path) {
        return matches();
    }

    @Override
    public boolean matches() {
        Date d = new Date();
        return d.after(start) && d.before(end);
    }
};
Example Non-OSGI Setup
RestrictionProvider rProvider = CompositeRestrictionProvider.newInstance(new MyRestrictionProvider(), ...);
Map<String, RestrictionProvider> authorizMap = ImmutableMap.of(PARAM_RESTRICTION_PROVIDER, rProvider);
ConfigurationParameters config =  ConfigurationParameters.of(ImmutableMap.of(AuthorizationConfiguration.NAME, ConfigurationParameters.of(authorizMap)));
SecurityProvider securityProvider = SecurityProviderBuilder.newBuilder().with(config).build();
Repository repo = new Jcr(new Oak()).with(securityProvider).createRepository();