001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, 013 * software distributed under the License is distributed on an 014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 015 * KIND, either express or implied. See the License for the 016 * specific language governing permissions and limitations 017 * under the License. 018 */ 019package org.apache.shiro.authz; 020 021/** 022 * A Permission represents the ability to perform an action or access a resource. A Permission is the most 023 * granular, or atomic, unit in a system's security policy and is the cornerstone upon which fine-grained security 024 * models are built. 025 * <p/> 026 * It is important to understand a Permission instance only represents functionality or access - it does not grant it. 027 * Granting access to an application functionality or a particular resource is done by the application's security 028 * configuration, typically by assigning Permissions to users, roles and/or groups. 029 * <p/> 030 * Most typical systems are what the Shiro team calls <em>role-based</em> in nature, where a role represents 031 * common behavior for certain user types. For example, a system might have an <em>Administrator</em> role, a 032 * <em>User</em> or <em>Guest</em> roles, etc. 033 * <p/> 034 * But if you have a dynamic security model, where roles can be created and deleted at runtime, you can't hard-code 035 * role names in your code. In this environment, roles themselves aren't very useful. What matters is what 036 * <em>permissions</em> are assigned to these roles. 037 * <p/> 038 * Under this paradigm, permissions are immutable and reflect an application's raw functionality 039 * (opening files, accessing a web URL, creating users, etc). This is what allows a system's security policy 040 * to be dynamic: because Permissions represent raw functionality and only change when the application's 041 * source code changes, they are immutable at runtime - they represent 'what' the system can do. Roles, users, and 042 * groups are the 'who' of the application. Determining 'who' can do 'what' then becomes a simple exercise of 043 * associating Permissions to roles, users, and groups in some way. 044 * <p/> 045 * Most applications do this by associating a named role with permissions (i.e. a role 'has a' collection of 046 * Permissions) and then associate users with roles (i.e. a user 'has a' collection of roles) so that by transitive 047 * association, the user 'has' the permissions in their roles. There are numerous variations on this theme 048 * (permissions assigned directly to users, or assigned to groups, and users added to groups and these groups in turn 049 * have roles, etc, etc). When employing a permission-based security model instead of a role-based one, users, roles, 050 * and groups can all be created, configured and/or deleted at runtime. This enables an extremely powerful security 051 * model. 052 * <p/> 053 * A benefit to Shiro is that, although it assumes most systems are based on these types of static role or 054 * dynamic role w/ permission schemes, it does not require a system to model their security data this way - all 055 * Permission checks are relegated to {@link org.apache.shiro.realm.Realm} implementations, and only those 056 * implementations really determine how a user 'has' a permission or not. The Realm could use the semantics described 057 * here, or it could utilize some other mechanism entirely - it is always up to the application developer. 058 * <p/> 059 * Shiro provides a very powerful default implementation of this interface in the form of the 060 * {@link org.apache.shiro.authz.permission.WildcardPermission WildcardPermission}. We highly recommend that you 061 * investigate this class before trying to implement your own <code>Permission</code>s. 062 * 063 * @see org.apache.shiro.authz.permission.WildcardPermission WildcardPermission 064 * @since 0.2 065 */ 066public interface Permission { 067 068 /** 069 * Returns {@code true} if this current instance <em>implies</em> all the functionality and/or resource access 070 * described by the specified {@code Permission} argument, {@code false} otherwise. 071 * <p/> 072 * <p>That is, this current instance must be exactly equal to or a <em>superset</em> of the functionality 073 * and/or resource access described by the given {@code Permission} argument. Yet another way of saying this 074 * would be: 075 * <p/> 076 * <p>If "permission1 implies permission2", i.e. <code>permission1.implies(permission2)</code> , 077 * then any Subject granted {@code permission1} would have ability greater than or equal to that defined by 078 * {@code permission2}. 079 * 080 * @param p the permission to check for behavior/functionality comparison. 081 * @return {@code true} if this current instance <em>implies</em> all the functionality and/or resource access 082 * described by the specified {@code Permission} argument, {@code false} otherwise. 083 */ 084 boolean implies(Permission p); 085}