我爱编程：用户管理 Restriction Management-Oak

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
• AggregationAware: optional extension to make a RestrictionProvider aware of being used in an composite setup, since Oak 1.44.0 (see OAK-9782)

Default Implementation

Oak 1.0 provides the following base implementations:

• AbstractRestrictionProvider: abstract base implementation of the provider interface. Since 1.44.0 also implements AggregationAware (see OAK-9782)
• 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:globs	String	true	false	Multivalued variant of the rep:glob restriction	Oak 1.44.0
rep:subtrees	String	true	false	Multivalued restriction that limits effect to one or multiple subtrees (see below)	Oak 1.44.0

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.

rep:subtrees – Details and Examples

The rep:subtrees restriction allows to limit the effect to one or multiple subtrees below the access-controlled node. It is a simplified variant of the common pattern using 2 rep:glob (wildcard) patterns to grant or deny access on a particular node in the subtree and all its descendent items.

A common pattern involving rep:glob may look as follows:

• entry 1: rep:glob = “/*/path/to/subtree”
• entry 2: rep:glob= “/*/path/to/subtree/*”

The rep:subtrees restriction neither requires multiple entries nor wildcard characters that have shown to be prone to mistakes. The corresponding setup with rep:subtrees would be

• entry: rep:subtrees = “/path/to/subtree”

and matches both the tree defined at /foo/path/to/subtree as well as any subtree at /foo/*/path/to/subtree.

For a node path /foo the following results can be expected for different values of rep:subtrees:

rep:subtrees	Result
[/cat]	all descendants of /foo whose path ends with /cat or that have an intermediate segment /cat/
[/cat/]	all descendants of /foo that have an intermediate segment /cat/
[cat]	all siblings or descendants of /foo whose path ends with cat or that have an intermediate segment ending with cat
[cat/]	all siblings or descendants of /foo that have an intermediate segment ending with cat

Note:

• variants of ‘cat’-paths could also consist of multiple segments like e.g. /cat/dog or /cat/dog
• different subtrees can be matched by defining multiple values in the restriction
• in contrast to rep:glob no wildcard characters are required to make sure the restriction is evaluated against the whole tree below the access controlled node.
• an empty value array will never match any path/item
• null values and empty string values will be ignored

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();

更多请阅读：Restriction Management

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