Authorization for Access Control

The Authorization for Access Control security service is concerned with implementing policy-based access control decisions, with the assumption that the appropriate Identity Establishment has taken place. The service consumes as input a credential/identity token which embodies the identity of a service requestor and/or for the resource that the service requestor requests. Based upon the credentials and trust factors and policy, the resource will determine if authenticating the peer is to be performed. Once authenticated, the peers may then process each other’s requests (as authorized), based upon appropriate policy enforcement (e.g. privilege or role based access).

It is expected that the hosting environment for Open Grid Services Architecture (OGSA)-compliant services will provide access control functions, and it is appropriate to further expose an abstract authorization service depending on the granularity of the access control policy that is being enforced. Allow for controlling access to OGSA services based on authorization policies (i.e., who can access a service, under what conditions) attached to each service. Also allow for service requestors to specify invocation policies (i.e. who does the client trust to provide the requested service). Authorization should accommodate various access control models and implementation.

Factors for Access Control Authentication

Authentication for Access Control relies upon several basic factors being achieved:

·    That the identity of the entity/person is established. The Identity Establishment Service performs this function.

• That there is an acceptable level of Trust established that the entity is who they claim to be. The Trust Establishment and Quality of Identity services are involved in providing this functionality.
• That there is a policy and management process that has been used to determine which entity has the privileges to access certain assets, resources, or information. The Policy and Security Management Interface (SMI)-related services provide this functionality.
• That there is a mechanism to enforce the mandates of the policy and management process. The Authorization for Access Control service is responsible for providing this functionality.

Categories of Access Control

There are generally three (3) categories of Access Control that need to be addressed within a security domain: Physical Assets; Computational Resources; and Information.

Physical Access to Assets

The basic premise of physical access control is intended to allow authorized individuals to be able to enter the areas for which they have clearance to enter and to make it difficult for un-authorized individuals to enter. Based on the Security Domain definition, physical access control is not an inter-domain issue. However, there are some desirable aspects to any physical access control system:

·       The system should be capable of providing an audit trail of who actually entered a specific area.

·       The system should be capable of detecting intrusion attempts of an un-authorized individual to enter an area.

·       There are issues in regards to the quickness/speed of enunciating intrusion or intrusion attempts. The speed at which this enunciation can occur is a key metric in regards to the ability of a SMI to respond to the intrusion.

·       The system should be robust enough that intrusions can be proven in an authoritative manner so that legal prosecution has a probability of success.

·       Properly implemented, a physical access control system can provide on-site personnel listings/locations in the event of an emergency event.

·       The choice of access control mechanisms should allow for multi-factor authentication and ease of management in the event that revocation of access privileges is required (e.g. User and Group Management issues). In order to accomplish this service function, there must be a security token that is used to enable a final access mechanism (e.g. a lock).

·       A policy/strategy needs to address assets that are not capable of being physically secured. For these types of resources, informational and resource security measures will need to be enhanced. Examples of such an assets are wireless networks and wireless technologies.

·       A residual risk analysis and recovery plan needs to be developed, as part of the Policy service, to address resources for which no type of adequate security can be provided. Examples of such physical resources are transmission lines and telephone lines.

In order to provide physical access control, there needs to have a physical barrier that separates critical or controlled areas from un-controlled areas. These barriers would typically be fences, walls, or doors that have locks or security guards so that proper access privileges can be determined.

Physical Access Technologies/Specifications

There are no relevant specifications regarding Physical Authorization for Access Control. However, there are typical strategies that are worthy of some discussion (see Table 2).

Table 2: Typical Physical Access Control Strategies

Another method of analyzing the same strategies would be:

Table 3: Physical Security Strategies vs. Security Services Provided

Technological Assessment

The suggested technology to be used to provide Access Control to critical areas is the use of multi-factor access control. It is further suggested that SMART-CARD[2]s that double as personal identification cards be utilized to enable combination locks. Furthermore, it is also recommended that such technology deployment be used in conjunction with an electronic audit mechanism.

Computational Resource

The basic premise of computational access control is intended to allow authorized individuals to be able to access programs for which they have clearance to make use of. Based on the Security Domain definition, computational access control is both an inter-domain and intra-domain issue. However, the enforcement of computation access control is purely an intra-domain issue. For inter-domain access control the Identity Mapping service (and its required sub-functions) actually provides the mapping from an external identity to an identity recognized and managed intra-domain.

·       The system should be capable of providing an audit trail of who accessed a given computational resource.

·       The system should be capable of detecting intrusion attempts of an un-authorized individual to a computational resource.

·       There are issues in regards to the quickness/speed of enunciating intrusion or intrusion attempts. The speed at which this enunciation can occur is a key metric in regards to the ability of a SMI to respond to the intrusion.

·       The system should be robust enough that intrusions can be proven in an authoritative manner so that legal prosecution has a probability of success.

·       The choice of access control mechanisms should allow for multi-factor authentication and ease of management in the event that revocation of access privileges is required (e.g. User and Group Management issues). In order to accomplish this service function, there must be a security token that is used to enable a final access mechanism (e.g. a lock).

·       A policy/strategy needs to address assets that are not capable of being secured. For those types of resources, the level of trust should be considered low.

The aforementioned issues need to be addressed for a variety of computational resources: Operating Systems (OSs); programs within a OS that has access control; programs within an environment where there is no OS access control required to access the program (e.g. an RTU); and wireless networks.

Operating System and Computer Programs

Operating System (OS) access control requires Identity Establishment (see the identity establishment service). The access control service, for OSs, determines which programs/computational resources the Identified User/Program has privileges to execute/access.

The major issues regarding this access are:

·       To provide an appropriate policy and SMI so that such access is granular enough to provide enough audit capability.

·       Managing the configuration in a distributed environment.

·       The level of trust that can be associated with the OS to perform its tasks in a secure manner (see ACC-01). Several issues are mitigated if a “Trusted/Secure” OS is used. However, the use of such OSs in IntelliGrid Architecture environment is not viable in a majority of the cases, therefore this section will address non-Trusted OS issues.

For all OSs, the issue of access control relates to properly managed Access Control Lists that are typically OS specific. However, care needs to be taken to ensure that if Role Based Access is used, that an audit mechanism is provided in order to reference back to the actual individual/entity that has accessed the OS. Additionally, the information in ACC-02 should be considered when developing the OS access framework in a distributed environment.

Computer Programs

In the cases where an OS does not provide Access Control to the programmatic level, programs themselves need to provide this capability. This is particularly true for electronic protocol processes that bypass OS authentication on the destination of the communication path. In such a situation, it is incumbent upon the destination program/process to apply the appropriate security mechanisms.

In IntelliGrid Architecture there will be computational and communication technologies integrated of various capabilities. These various capabilities (e.g. process/memory/storage capacity or bandwidth limitations) require that different technological solutions be available. However the functional objectives remain consistent: provide a manageable environment and to provide enough granularity to provide a capability for non-repudiation.

Communication Networks

There are several types of communication networks that need to be addressed:

·      Inter-Domain networks where the physical network are exposed. The major issue with these types of physical networks is that both domains do not manage the network segments that provide the inter-domain interfaces. These segments are typically provided by a third party and therefore constitute a third Security Domain. Thus it is important that appropriate access control be provided at the security domain interface points.

·      Intra-Domain networks where the physical network is within a Security Domain. For intra-domain networks, some Security Domains may desire to control the computers/computer users that actually have access to the network. Once a resource is within a Security Domain, there is no reliable mechanism to prevent physical access to the network. Thus it becomes incumbent upon the SMI to detect that a non-authorized access to the network has been attempted or been successful. Additionally, it may be possible to make it more difficult for a non-authorized resource to make use of the network through proper management of the network addresses so that no address is assigned to the intruding resource.

·      Wireless LAN/WAN Networks whose transmissions can be easily monitored and spoofed. This type of network represents an intra-domain network that REQUIRES management in regards to who can actually make use of the network. The issue can be easily demonstrated by looking at the prevalence of WI-FI. In the WI-FI case, hot-spots (e.g. Starbucks, airports) could not recoup their investment without a challenge response mechanism to ensure that only authorized (e.g. paid subscription entities) are actually assigned an address that facilitates real communications. Such mechanisms may prevent off-segment communications, but will not prevent denial-of-service attacks (see ACC-03). Thus such systems need to be augmented beyond challenge-response.

·      Dial-up Networks: There is a well-documented history in regards to the vulnerabilities associated with dial-up networks. These types of networks are inherently susceptible to denial-of-service attacks and have poor identity establishment/access control at a physical/network level. This is especially true for equipment that is deployed in the Transmission and Distribution environment.

Table 4: References regarding Computational Resource Access Control

Technological Assessment Specifications/Standards

Table 5 represents a set of specifications and/or standards that are relevant to the understanding of the issues regarding access control for computational resources. Those specifications marked as Recommended or Recommended Reading should be considered as materials that should be considered prior to actually implementing the access control service.

Table 5: Relevant Computational Resource Access Control Standards/Specifications

Technological Assessment and Recommendations

OS Recommendations

It is recommended that Trusted OSs be used whenever possible. Additionally, ANSI INCITS 359-2004 us suggested as an implementation strategy for Role Based Access.

Computer Programs

It is recommended that the appropriate access control list mechanisms be used in regards to the applications where such technologies have been noted in Table 5. Thus, make use of:

·       RFC 1013 for X Windows applications.

·       RFC 2086 for IMAP based applications.

·       RFC 2820 for LDAP.

·       RFC 1305 in regards to NTP.

Otherwise, it is suggested to follow the general policies/procedures set forth in ISO/IEC 10181-3:1996 and make use of any application specific access control strategies set forth.

Communication Networks and Protocols

In general it is recommended that all computational resources, when possible, be assigned dynamic addresses that allow off-segment communications. There is no single technology that can accomplish this, but a challenge response mechanism is suggested as part of the implementation strategy.

For those resources that require fixed addresses (e.g. servers of data), it is suggested that network based access control lists be implement in order to prevent un-authorized off-segment communication.

There is a substantial amount of work occurring within IEC TC57 WG15 to secure several of the communication protocols that are intended to be used by IntelliGrid Architecture. It is suggested that these be adopted and deployed as rapidly as is feasible.

Wireless networks are extremely susceptible to denial-of-service attacks. In order to mitigate this issue, AES encryption on wireless links is suggested.

Dial-up access control should be implemented through the use of RAIDUS (RFC 2865 and RFC 2869) when this is feasible. Such access should be deployed so that there is an additional access control list (e.g. a Firewall or router based ACL) that provides additional security. Thus, when possible, it is suggested that NO direct dial-up access be given to a computer or a computer process. However, this is not always feasible in the Transmission and Distribution systems deployed within IntelliGrid Architecture environment (e.g. RTUs and field devices). For this class of resource, or resources with similar constraints, it is suggested that the devices be implemented in such a manner that denial-of-service is mitigated:

• Dial-up connections should be constructed such there is an inactivity time-out to prevent a connect/hold the port open denial of service attack.

• Once the port is connected, there should be a time-out on the connection that requires valid communication protocol/application level information flow.

• It is not suggested to implement a dial-back strategy since these become difficult to manage and maintain and does not allow the type of environment that IntelliGrid Architecture is attempting to promote.

Informational Technology Assessment/Specification

Information access control is extremely similar to a combination of OS and program access. However, it is up to each individual program to provide the appropriate level of access control.

ACC-04 represents a very simple summary of the granularity required in access control for most databases: Control over Reading; Control over Changing; and Control over Storing. Additionally, for Object Oriented access, there may need to be an ability to prevent an entity from discovering that an Object Exists (optional).

Table 6: References relating to Access Control for Informational Resources