Abstract:
A system and article of manufacture providing a high performance access control list. The preferred embodiments operate in a computer network having a plurality of users of the network and comprising a database management system and a content management system controlling access to a plurality of entities shareable by the users of the network, the content management system using an access control list table having group privilege rules and user privilege rules for controlling access to the entities. A high performance ACL system and article of manufacture is provided, the system and article including a run-time compiled ACL table, wherein the compiled ACL table provides resolved privilege rules for each of the users at run-time, and using the compiled ACL table, the content management system accesses user-selected ones of the entities based on the resolved privilege rules.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 10/459,078 which was filed on Jun. 11, 2003 now U.S. Pat. No. 7,478,094. 
    
    
     BACKGROUND OF THE INVENTION 
     This application pertains to the problem of flexibly and efficiently controlling the access rights of a large number of users to a large number of objects or other data entities. The problem arises, for example, in the context of a large number of users sharing access to a database management system on a network in which end users are given differing levels of access to different entities in the managed database. These entities represent the content of the network, as seen by end users. The entities may include, for example, data files, image files, sound files, multimedia files, client account information, etc. 
     The need to assign user-specific access rights to different entities arises in a variety of situations. For example, it may be desirable to give some users read/write access to certain entities, meaning that these users can replace data representing the entity, while others users may be limited to read-only access, meaning that these users can view the data but not alter or delete the data representing the entity. Some users may not be given any access to certain critical entities. 
     Various techniques are known in the art for controlling user accesses to objects and other data entities. One technique, which is commonly used in file systems, involves the storage of an access control list (ACL) for each data entity to which access is to be controlled. The ACL for a given data entity will typically be in the form of a list of the users or groups that have access to the data entity, together with the access rights or privileges of each such user or group with respect to the data entity. The organizing of users into groups simplifies the maintenance of an ACL, especially where a large number of users share the same set of access privileges. Such a group, for example, would be a public access group which would normally have limited, read-only access privileges. A user may, however, belong to a group with which many privileges are shared with other users, but where the user has some additional privileges or restrictions than the associated group. In such cases, the ACL can contain a user privilege that overrides the group privilege for particular database entities. 
     Each time a user requests access to an entity, a content management system (CMS) operating with or within the database management system will search the data entity&#39;s ACL to determine whether the user has been given user-specific privileges with respect to the requested entity. If the user has not been assigned user-specific privileges, the CMS may have to then search the ACL to determine group membership for the user, and then find the group privileges with respect to the requested entity. 
     With the increasing popularity and importance of networked resources it has become increasingly important to be able to provide rapid privilege determination to large numbers of users with controlled access to large numbers of content entities, particularly in high volume transaction environments. To provide flexibility, it is desirable to be able to individualize the access rights of users, and still provide a high performance run-time resolution of the user&#39;s privileges. 
     Although prior art access control techniques such as those summarized above are suitable in theory for flexibly controlling user access to large-scale networked databases, these techniques tend to take unacceptably long periods of time to search because of the number of searches that must be performed to resolve both group and individual user privileges. 
     A need thus exists in the art for a high performance run-time technique that is suitable for flexibly controlling the access of a large number of users and groups to data entities. A need also exists to be able to flexibly and efficiently define new types of access privileges as new users and groups are added to, or deleted from the system. 
     The embodiments of the claimed invention therefore provide solutions to the aforementioned problems, and offer other advantages over the prior art. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided a system providing a high performance ACL in a computer network having a plurality of users of the network. The network includes a database management system and a content management system controlling access to a plurality of entities shareable by the users of the network. The content management system uses an access control list table having group privilege rules and user privilege rules for controlling access to the entities. The system provides a run-time compiled ACL table, run-time being the duration of time that the entities are available to the users, wherein the compiled ACL table provides resolved privilege rules for each of the users at run-time. The system further uses the compiled ACL table, the content management system accessing user-selected ones of the entities based on the resolved privilege rules. 
     In accordance with another aspect of the present invention, there is also provided a computer network system having a plurality of users of the network system. The system comprises a database management system and a content management system configured to control access to a plurality of entities shareable by the users of the network system. The content management system is configured to use an access control list table having group privilege rules and user privilege rules for controlling access to the entities, and comprises a means of providing a run-time compiled ACL table and a means of using the compiled ACL table. The content management system is configured to access user-selected ones of the entities based on the resolved privilege rules. 
     In accordance with yet another aspect of the present invention, there is provided an article of computer-readable media having contents that provide a high performance security by means of an ACL on a computer network having a plurality of users of the network. The network comprises a database management system and a content management system controlling access to a plurality of entities shareable by the users of the network. The content management system uses an access control list table having group privilege rules and user privilege rules for controlling access to the entities. The network is configured to perform the computer-implemented steps of providing a run-time compiled ACL table and using a compiled ACL table, the content management system accessing user-selected ones of the entities based on resolved privilege rules. 
     The embodiments of the claimed invention reduce the time required to determine privilege rules for the users at run-time based on the compiled ACL table of resolved privilege rules for each user. 
     The compiled ACL table can be updated during run-time, thereby maintaining the reduction in time provided by the embodiments of the present invention. 
     Also, more users and transactions can be supported at run-time without straining system resources. 
     Other uses and applications of the subject system will become apparent to those skilled in the art upon a reading and understanding of this specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may take physical form in certain parts and steps and arrangements of parts and steps, the preferred embodiments of which will be described in detail in the specification and illustrated in the accompanying drawings hereof and wherein: 
         FIG. 1  is a block diagram of a network-connected content management system in accordance with a preferred embodiment of the present invention; 
         FIG. 2  is a block diagram depicting how a user needs to pass both user privileges and bound ACL checks; 
         FIG. 3  depicts user and group associations as maintained in a table in accordance with the present invention; 
         FIG. 4  diagrammatically shows the relationship between ACL codes and access control lists; and 
         FIG. 5  is a flow diagram of a method according to a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
     The detailed description which follows is presented in terms of general procedures, steps and symbolic representations of operations of data bits within a computer memory, associated computer processors, networks, and network devices. These procedure descriptions and representations are the means used by those skilled in the data processing art to convey the substance of their work to others skilled in the art. A procedure is here, and generally, conceived to be a self-consistent sequence of steps or actions leading to a desired result. Thus, the term “procedure” is generally used to refer to a series of operations performed by a processor, be it a central processing unit of a computer, or a processing unit of a network device, and as such, encompasses such terms of art as “objects,” “functions,” “subroutines” and “programs.” 
     The procedures presented herein are not inherently related to any particular computer or other apparatus. In particular, various general purpose machines may be used with programs in accordance with the teachings herein, or it may prove more convenient to construct more specialized apparatus to perform the required method steps. 
     However, one of ordinary skill in the art will recognize that there exists a variety of platforms and languages for creating software for performing the procedures outlined herein. One of ordinary skill in the art also recognizes that the choice of the exact platform and language is often dictated by the specifics of the actual system constructed, such that what may work for one type of general purpose computer may not be efficient on another type of general purpose computer. 
     One of ordinary skill in the art to which this invention belongs will have a solid understanding of content management systems, database management systems, and methods of securely controlling access to entities managed by the content management system such as an access control list (ACL) in particular. It being recognized that such practitioners do not require specific details of the software, but rather find data structure descriptions and process descriptions more desirable (due to the variety of suitable hardware and software platforms), such specifics are not discussed to avoid obscuring the invention. 
     Various terms are used to describe the invention that are well known to practitioners of the art are listed here for convenience. 
     Access Control List (ACL) 
     A set of one or more access control rules. These rules are used to control access to CM controlled Entities. 
     Access Control Rule (ACL Rule) 
     A rule specifies who (Users/Groups/Public) can perform what functions (ACL Privileges) on specific CM controlled entities. Rules with the same ACL Code form an ACL. 
     ACL Code 
     A CM system-generated unique identifier for an ACL. The CM Controlled Entity ACL binding is carried out using this code. 
     ACL Privileges 
     Operations specified in an ACL Rule that are allowed to be applied on the bound controlled entity by the ACL-specified users. See also User Privileges. 
     ACL Rule for Group 
     An ACL Rule that is pertinent to a group. 
     ACL Rule for Public 
     An ACL Rule that is pertinent to all users. 
     ACL Rule for User 
     An ACL Rule that is pertinent to an individual user. 
     Compiled ACL Table 
     A simulated database summary table that contains compiled ACLs. It optimizes runtime access control resolving. 
     Compiled Permission Table 
     A simulated database summary table that contains compiled user privileges. It optimizes runtime access control resolving. 
     Controlled Entity 
     A unit of protected user data that can be an item, an item type or the entire library. It must be bound to an ACL. Access to a controlled entity is authorized by both user privileges and the ACL. 
     Group 
     A number of zero of more users. Used only for defining ACLs, not granting user privileges. 
     Item 
     An atomic user data entity stored in the CM Library Server. 
     Item Type 
     A schema definition for a collection of items. Also used to represent all items that conform to the same schema definition. 
     Library 
     The entire collection of user data stored in the CM system. 
     Privilege 
     An ability to use the CM system. A user must be grouped into the privilege set before the CM system can be used. 
     Privilege Definition Code 
     A CM system-generated unique identifier for each CM privilege. 
     Privilege Set 
     A named group of privileges. It is used for both defining ACLs and granting privileges to users. 
     Privilege Set Code 
     A CM system-generated unique identifier for each CM privilege set. User privileges granting and ACL defining are carried out using this code. 
     System-defined Privilege 
     A CM system-defined privilege definition. See also User-defined privilege. 
     System Entity 
     The CM system management entities which can be system tables, views, indexes and stored procedures. A system entity has no ACL associated with it. Access to system entities is authorized only by the user privileges. See also controlled entity. 
     User 
     A registered CM user that can obtain CM services. 
     User-defined Privilege 
     The CM user-defined application-specific privileges. See also system-defined privilege. 
     UserID 
     A unique name for a CM user. Used for runtime authentication and access control. 
     User Privileges 
     A number of privileges granted to every CM User, stored in a user profile. It defines the maximum operations a user can perform. A user&#39;s effective access rights will never exceed his user privileges. See also ACL privileges. 
       FIG. 1  is a block diagram of a network-connected content management system in accordance with a preferred embodiment of the present invention. The system shown in  FIG. 1  is particularly suited to delivery of content over a network or the Internet. A content management system  10  is running on a server computer  12  which is connected to a network  14 . A user  16  of the CMS  10  accesses controlled entities on a content database  18 , such as a DB2 database for instance, by communicating with the CMS  10  via the network  14 . The CMS  10  is in communication with a library server (LS)  20 , a resource manager (RM)  22  and a database management system (DBMS)  24 . The CMS  10 , LS  20 , RM  22  and the DBMS  24  are shown in the figure as running on the same server  12 , however, it is to be appreciated that some or all of these may be running on separate, network connected, computers. 
     A concept of the CM access control model is that of user privileges. Each CM user  16  is granted a number of privileges. These privileges define the maximum scope of operations that a user can perform. A user&#39;s effective access rights to content on the database  18  will never exceed the user=s particular user privileges. 
     Another concept is that of the controlled entity. A controlled entity is a unit of protected user data on the database  18 . In the CM system, this can be an item, an item type, or the entire Library. The operation(s) applied on a controlled entity is authorized by one or more control rules from an access control list. Every CM Controlled Entity must be bound to an ACL. An item can be bound to an ACL in different levels. When an operation is applied to an item, an access control will check for the user&#39;s ACL privilege based on the configured binding level. 
     ACL, still another concept of the CM access control model, is one or more rules, associated with a controlled entity, authorizes user operation(s) on the bound entity. In particular, it specifies who (Users/Groups/Public) can perform what functions (ACL privileges) on the controlled entity. An ACL only defines the authorization of the bound entities and does not circumvent the user privileges. 
     In general, to perform an operation on a CM controlled entity, the user needs to pass both the user privileges and the bound ACL checks, as depicted in  FIG. 2 . For example, user  1  privileges  30  are allow operations a, b, c and d. User  2  privileges  32  allow operations a, c, d and e. However, item X binding  34  is to ACL code Y which allows user  1  to perform operations c and e on item X, while user  2  is permitted to perform operations b, c and e on item X. The resulting allowed operations  36  for users  1  and  2  permit user  1  to perform only operation c on item X, and permit user  2  to perform only operations c and e on item X. 
     The scope of the present invention, however, is primarily concerned with the resolving of ACL rules for each user, and the following description will, therefore, concentrate on the aspect of ACL rule resolving for users and user groups. 
     A CM group consists of zero or more users, usually with the same job description. A user may belong to none or to any number of groups. A group, however, should not belong to other groups. CM groups do not usually relate to DBMS or operating system groups. They serve rather as a convenient shorthand for defining ACLs only. 
     Groups are represented as CM users and stored in a user table with a User-Kind column containing a unique value, such as 1, standing for “Group”. User and group associations are maintained in another table as depicted in  FIG. 3 . The user table  40  contains both user and group entries, while the user-group association table  42  contains the relationships between users and groups. For example, a group  44  in the user table  40  consists of a first user  46  and a second user  48 , and the relationship is defined by the first group-user association  50  and the second group-user association  52  in the user-group association table  42 . 
     An ACL consists of one or more access control rules. Each ACL is assigned a unique identifier called Access Control List Code (ACL Code). The ACL definitions and codes are stored in a CM system access-list table. 
     An access control rule specifies who (Users/Groups/public) can perform what functions (ACL Privileges). Rules with the same ACL Code form an ACL. The rule definitions and the associations of rules with ACL are maintained in the system access-list table. 
     The ACL codes and lists are depicted in the diagram shown in  FIG. 4 . For example, an ACL code  60  defines an ACL comprising the rules  62 ,  64  and  66  having that same ACL code. 
     A CM controlled entity is bound to a specific ACL through the ACL Code. When associated with CM controlled entities, ACLs define the authorization of the bound entities and do not circumvent the User Privileges. ACL is enforced in addition to the User Privileges check as previously described. 
     The user specified in access control rules can be an individual user, a group, or public. The interpretation is determined by a user-kind field of the respective rule. The types of rules, for illustration purposes, can be given the names ACL Rule for User, ACL Rule for Group, and ACL Rule for Public, respectively. By specifying public, the ACL Rule for Public authorizes all the users to perform operations specified in the ACL Privileges on the bound entity, provided each user passes the respective user privilege check. 
     Within the same ACL, a user may be specified in more than one type of rule. The precedence of the three types, from highest to lowest, is ACL Rule for Public, ACL Rule for User, ACL Rule for Group. When applying ACL checks, if any higher-precedence rule type passes, the authorization is resolved and the process stops. If, for instance, the check of the ACL Rule for Public fails, the checking process continues to the lower-precedence rule types. If the check of the ACL Rule for User fails, however, the checking can stop; i.e., the ACL Rule for Group need not be checked. There is no need to continue the check on the Group type because, if a user does an individual User check, meaning the user has a rule in the access list table, this user will be excluded from the Group type access based on an access control algorithm. Therefore, the access control check for an individual User type and a Group type is not a sequential process, but an either/or process, even though there is no harm in doing a sequential check. If, however, the user is failed on an individual User type check, or the user does not have a rule in the access list table, the checking process continues to the Group type. If the user belongs to one of groups and the check of privilege passes, the authorization is considered resolved and the process stops. Otherwise, the user is denied permission and the process also stops. When a user is specified in more than one ACL Rule for a group, the user is authorized by the union of all the specified rules&#39; ACL privileges. A user should not be specified in more than one ACL rule for a user. 
     To optimize the user privilege resolving process, a CM access control module provides a simulated summary table, called the compiled ACL Table. This table contains the resolved access control information, meaning that each row in the table represents an authorized privilege for a user that is defined in an ACL rule. When accessing an item, this table will be joined on the item&#39;s ACL code, constrained by the run-time user&#39;s name and the desired privilege. If such a row exists, the operation on that item is allowed, otherwise it is denied. 
     To further optimize the resolving process, a compiled ACL table according to a preferred embodiment of the present invention is provided that enables run-time privilege resolving by simply querying one table, without any table joins as previously described. For example, a user desires to create an item instance in the database  18  of  FIG. 1 , and the LS  20  determines an appropriate ACL code for the item. To determine if the user can create the desired item, the LS  20  only needs to query the compiled ACL with the specified ACL code to determine if the user has the necessary privilege to create the item or not. 
     An algorithm according to the preferred embodiment is herein described that ensures that the compiled ACL table contains privileges either extracted from the user ACL rule or the group ACL rule, eliminating the need for table joins. The method hereinafter described, is suitable for building an initial run-time compiled ACL table, and for maintaining the compiled ACL table during run-time, wherein run-time is defined as the period of time that the CM system is actively serving users. 
     Referring now to  FIG. 5 , the preferred algorithm is now described. At step  70  it is determined if a user ACL is being added. If a user ACL is being added, at step  72 , rows are deleted rows from the compiled ACL table based on group rules for the respective user, rows are added to the compiled ACL table based on the added user ACL rule. 
     If a user ACL rule is being updated as determined at step  74 , step  76  is invoked to delete all rows from the compiled ACL table having a respective previously added user ACL rule and rows are added to the compiled ACL table based on the added user ACL rule. 
     If a user ACL rule is being deleted as determined at step  78 , step  80  is invoked to delete all rows from the ACL table having a respective previously added user ACL rule. 
     If a group ACL rule is being added as determined at step  82 , processing at step  84  adds rows to the compiled ACL table based on the added group ACL rule for all users included in the specified group that have no respective user ACL rule. 
     If a group ACL rule is being updated as determined at step  86 , step  88  is invoked to delete all rows from the compiled ACL table having a respective previously added user ACL rule for a user belonging to the specified group, and rows are added to the compiled ACL table based on the added group ACL rule for all users included in the specified group that have no respective user ACL rule. 
     If a group ACL rule is being deleted as determined at step  90 , step  92  is invoked to delete all rows from the compiled ACL table having a respective previously added user ACL rule for a user belonging to the specified group. 
     The invention has been described with reference to the preferred embodiments. Potential modifications and alterations will occur to others upon a reading and understanding of the specification. It is our intention to include all such modifications and alterations insofar as they come within the scope of the appended claims, or the equivalents thereof.