Arcitura Education S90.20 Exam - Topic 1 Question 14 Discussion

Question

Service A has two specific service consumers, Service Consumer A and Service Consumer B (1). Both service consumers are required to provide security credentials in order for Service A to perform authentication using an identity store (2). If a service consumer's request message is successfully authenticated, Service A processes the request by exchanging messages with Service B (3) and then Service C (4). With each of these message exchanges, Service A collects data necessary to perform a query against historical data stored in a proprietary legacy system. Service A's request to the legacy system must be authenticated (5). The legacy system only provides access control using a single account. If the request from Service A is permitted, it will be able to access all of the data stored in the legacy system. If the request is not permitted, none of the data stored in the legacy system can be accessed. Upon successfully retrieving the requested data (6), Service A generates a response message that is sent back to either Service Consumer A or B .The legacy system is also used independently by Service D without requiring any authentication. Furthermore, the legacy system has no auditing feature and therefore cannot record when data access from Service A or Service D occurs. If the legacy system encounters an error when processing a request, it generates descriptive error codes. This service composition architecture needs to be upgraded in order to fulfill the following new security requirements:

1. Service Consumers A and B have different permission levels, and therefore, response messages sent to a service consumer must only contain data for which the service consumer is authorized.

2. All data access requests made to the legacy system must be logged.

3. Services B and C must be provided with the identity of Service A's service consumer in order to provide Service A with the requested data.

4. Response messages generated by Service A cannot contain confidential error information about the legacy system. Which of the following statements provides solutions that satisfy these requirements?

Lashon · Accepted Answer

B) Apply the Trusted Subsystem pattern by introducing a new utility service that encapsulates data access to the legacy system. After Service A authenticates a service consumer it creates a signed SAML assertion containing authentication and authorization information. The SAML assertions are used by Service A to convey the identity information of Service Consumer A or B to Services B and C .The utility service filters response messages to the service consumer based on the information in the SAML assertions. The utility service keeps a log of the all data access requests made to the legacy system. The Exception Shielding pattern is further applied to the utility service in order to prevent the leakage of confidential error information.

Lashon · Answer

A) To correctly enforce access privileges, Services B and C must share the identity store with Service A and directly authenticate Service Consumer A or B .Furthermore, Services B and C must each maintain two policies:
one for Service Consumer A and one for Service Consumer B .After receiving a request message from a Service A .Services B and C must evaluate the validity of the request by using the identity store and the appropriate policy. Service Consumers A and B are required to submit the necessary security credentials to the legacy system as part of the request message sent to Service A .After verifying the credentials, the legacy system-either-performs the necessary processing or-sends the response to Service A or denies access and sends an error message directly to Service Consumer A or B .The Message Screening pattern is applied to Service A so that it can perform message screening logic in order to filter out unauthorized data coming from the legacy system.

Lashon · Answer

C) Apply the Service Perimeter Guard pattern to provide selective access privileges to Service Consumers A and B .The resulting perimeter service shares the identity store with Service A, which it uses to authenticate each request message. If authentication is successful, the request message is forwarded to Service A .Service A then also authenticates the service consumer and retrieves the service consumer's security profile from the identity store upon successful authentication. Each service consumer's security profile includes its authorized level of access. Service consumer authentication is subsequently performed using digital certificates. The Exception Shielding pattern is further applied to the perimeter service in order to prevent the leakage of confidential error information.

Lashon · Answer

D) Apply the Trusted Subsystem pattern by introducing a new utility service that encapsulates data access to the legacy system. The utility service evaluates request messages by authenticating the service consumer against the identity store and also verifying the digital signature of each request. If the request is permitted, Service A forwards the service consumer's credentials to Services B and C, and to the legacy system. The response messages from Services B and C are returned to Service A, while responses from the legacy system are processed by the utility service. Logic is added to the utility service so that it can log access requests made to the legacy system.