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Common Security: CDSA and CSSM
Copyright © 1997 The Open Group


CDSA Add-In Module Overview

Figure: CDSA Add-In Module Structure

A CDSA add-in module is a dynamically-linkable library, composed of functions that implement some or all of the CSSM Module Interfaces. Add-in module functionality is partitioned into two areas:

Add-in modules provide one or more categories of security services to applications. The service categories are Cryptographic Service Provider (CSP) services, Trust Policy (TP) services, Certificate Library (CL) services, and Data Storage Library (DL) services. Each security service contains one or more implementation instances, called sub-services. For a CSP service providing access to hardware tokens, a sub-service would represent a slot. For a DL service provider, a sub-service would represent a type of persistent storage. These sub-services each support the module interface for their respective service categories. This documentation-part describes the module interface functions in the trust policy service category. More information about CSP, CL and DL services can be found in the CSSM Cryptographic Service Provider Interface Specification, CSSM Certificate Library Interface Specification and in the CSSM Data Storage Library Interface Specification respectively.

Each module, regardless of the security services it offers, has the same set of administrative responsibilities. Every module must expose functions which allow CSSM to indicate events such as module attach and detach. In addition, as part of the attach operation, every module must be able to verify its own integrity, verify the integrity of CSSM, and register with CSSM. Detailed information about add-in module structure, administration, and interfaces can be found in the CSSM Add-in Module Structure and Administration Specification.

Information about the Common Data Security Architecture (CDSA) and Common Security Services Manager (CSSM) can be found in the CSSM Application Programming Interface.

Trust Policy Overview

Trust Policy modules implement policies defined by authorities and institutions. Policies define the level of trust required before certain actions can be performed. Three basic action categories exist for all certificate-based trust domains:

The CSSM Trust Policy API defines the generic operations that each TP module supports. Each module may choose to implement the required subset of these operations for the policy it serves.

The CSSM API defines a pass-through function, which allows each module to provide additional functions, along with those defined by the CSSM Trust Policy API. When a TP function determines the trustworthiness of performing an action, it may invoke Certificate Library functions and Data storage Library functions to carry out the mechanics of the approved action. TP modules must be installed and registered with the CSSM Trust Policy Services Manager. Applications may query the Services Manager to retrieve properties of the TP module, as defined during installation.

Using Trust Policy Modules

An application determines the availability of a Trust Policy module by querying the CSSM Registry. When a new TP is installed on a system, it must be registered with CSSM. When a client requests that CSSM attach to a TP, CSSM returns a TP handle to the application which uniquely identifies the pairing of the application thread to the TP module instance. The application uses this handle to identify the TP in future function calls.

CSSM manages function tables provided by the TP module and the application. A function upcall table is used to register application memory allocation and de-allocation functions with CSSM. The Trust Policy module will have access to the upcall table. The Trust Policy module registers its function table with CSSM at library load time using CSSM_RegisterServices. See the CSSM Add-in Module Structure and Administration Specification for details of module installation and registration.

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