最新SOA Certification S90.20考試題庫，SOA S90.20課程的擬真試題下載

問題1
Service A is a publically accessible service that provides free multimedia retrieval capabilities to a range of service consumers. To carry out this functionality, Service A is first invoked by Service Consumer A (1). Based on the nature of the request message received from Service Consumer A, Service A either invokes Service B or Service C.
When Service B is invoked by Service A (2A) it retrieves data from publicly available sources (not shown) and responds with the requested data (3A). When Service C is invoked by Service A (2B) it retrieves data from proprietary sources within the IT enterprise (not shown) and responds with the requested data (3B). After receiving a response from Service B or Service C, Service A sends the retrieved data to Service Consumer A (4).
Service B does not require service consumers to be authenticated, but Service C does require authentication of service consumers. The service contract for Service A therefore uses WS-Policy alternative policies in order to express the two different authentication requirements to Service Consumer A.
When Service Consumer A sends a request message (1), Service A determines whether the request requires the involvement of Service C and then checks to ensure that the necessary security credentials were received as part of the message. If the credentials provided by Service Consumer A are verified. Service A creates a signed SAML assertion and sends it with the request message to Service C (2B) This authentication information is protected by public key encryption However, responses to Service Consumer A's request message (3B, 4) are not encrypted for performance reasons.

Recently, the usage of Service C has noticeably declined. An investigation has revealed response messages issued by Service C (3B) have been repeatedly intercepted and accessed by unauthorized and malicious intermediaries. As a result, Service Consumer A has lost confidence in the use of Service A for the retrieval of proprietary data because it is being viewed as a security risk. This is especially troubling, because the owner of Service A had planned to start charging a fee for Service A's ability to provide proprietary data via the use of Service C.
How can this service composition architecture be changed to address the security problem with minimal impact on runtime performance?

A. Use the existing PKI to provide two-way authentication of the exchanged messages.
After receiving a request from the service consumer, Service A can respond with a signed acknowledgement of the message, encrypted by the public key of Service Consumer A.
Only Service Consumer A will be able to decrypt the encrypted acknowledgement. Service Consumer A then responds to the acknowledgement, thereby verifying its identity with Service A.
Because both Service Consumer A and Service A are mutually authenticated, end-to-end transport-layer security is sufficient to provide message confidentiality in order to prevent unauthorized intermediaries from accessing messages originating from Service C.

B. Use the existing PKI to provide message-layer security for the response messages originating from Service C.
To provide message confidentiality, Service C can encrypt the response messages using Service Consumer A's public key. This prevents unauthorized intermediaries from accessing the content of response messages.

C. Use the existing PKI to establish secure communication between Service Consumer A and Service C.
A symmetric key can be generated for the data being sent from Service C to Service Consumer A Service C can generate a session key that is encrypted with Service Consumer A's public key. Service C can then attach the session key to the response message, which is encrypted using the session key. Because only Service Consumer A can decrypt the encrypted session key, the data transmitted in the message is safe from access by unauthorized intermediaries.

D. Use the existing PKI to specify encryption and digital signature requirements on the messages. Service C can use Service Consumer A's public key to generate a symmetric key. Service Consumer A can also generate the same session key from its own public key.
Service C can use the session key to encrypt the response message (and the hash value of the response message), concatenate them, and send them to Service Consumer A.
Service Consumer A separates the concatenated and encrypted hash value, decrypts it, and then decrypts the encrypted response message. As a result, the confidentiality and integrity of the response message are guaranteed.

正確答案: C

問題2
Service Consumer A sends a request message to Service A (1) after which Service A retrieves financial data from Database A (2). Service A then sends a request message with the retrieved data to Service B (3). Service B exchanges messages with Service C (4) and Service D (5), which perform a series of calculations on the data and return the results to Service A.
Service A uses these results to update Database A (7) and finally sends a response message to Service Consumer A (8). Component B has direct, independent access to Database A and is fully trusted by Database A.
Both Component B and Database A reside within Organization A.
Service Consumer A and Services A, B, C, and D are external to the organizational boundary of Organization A.

Service A has recently experienced an increase in the number of requests from Service Consumer A.
However, the owner of Service Consumer A has denied that Service Consumer A actually sent these requests. Upon further investigation it was determined that several of these disclaimed requests resulted in a strange behavior in Database A, including the retrieval of confidential data. The database product used for Database A has no feature that enables authentication of consumers. Furthermore, the external service composition (Services A, B, C, D) must continue to operate at a high level of runtime performance.
How can this architecture be improved to avoid unauthenticated access to Database A while minimizing the performance impact on the external service composition?

A. The Brokered Authentication pattern is applied so that each service consumer generates a pair of private/public keys and sends the public key to Service A.
When any service in the external service composition (Services A, B, C, and D) sends a request message to another service, the request message is signed with the private key of the requesting service (the service acting as the service consumer). The service then authenticates the request using the already established public key of the service consumer. If authentication is successful, the service generates a symmetric session key and uses the public key of the service consumer to securely send the session key back to the service consumer. All further communication is protected by symmetric key encryption. Because all service consumers are authenticated, all external access to Database A is secured.

B. Service Consumer A generates a pair of private/public keys (Public Key E and Private Key D) and sends the public key to Service A.
Service A can use this key to send confidential messages to Service Consumer A because messages encrypted by the public key of Service Consumer A can only be decrypted by Service A The Data Origin Authentication pattern can be further applied so that Service A can authenticate Service Consumer A by verifying the digital signature on request messages. The Message Screening pattern is applied to a utility service that encapsulates Database A in order to prevent harmful input.

C. A utility service is established to encapsulate Database A and to carry out the authentication of all access to the database by Service A and any other service consumers.
To further support this functionality within the utility service, an identity store is introduced.
This identity store is also used by Service A which is upgraded with its own authentication logic to avoid access by malicious service consumers pretending to be legitimate service consumers. In order to avoid redundant authentication by services within the external service composition, Service A creates a signed SAML assertion that contains the service consumer's authentication and authorization information.

D. Implement a firewall between Service Consumer A and Service A.
All access to Service A is then controlled by the firewall rules. The firewall contains embedded logic that authenticates request messages and then forwards permitted messages to Service A.
Moreover, the firewall can implement the Message Screening pattern so that each incoming message is screened for malicious content. This solution minimizes the security processing performed by Service A in order to maintain the performance requirements of the external service composition.

正確答案: C

問題3
Services A, B and C belong to Service Inventory A.
Services D, E and F belong to Service Inventory B.
Service C acts as an authentication broker for Service Inventory A.
Service F acts as an authentication broker for Service Inventory B.
Both of the authentication brokers use Kerberos-based authentication technologies. Upon receiving a request message from a service consumer, Services C and F authenticate the request using a local identity store and then use a separate Ticket Granting Service (not shown) to issue the Kerberos ticket to the service consumer.

Currently, tickets issued in one service inventory are not valid in the other. For example, if Service A wants to communicate with Services D or E, it must request a ticket from the Service Inventory B authentication broker (Service F). Because Service Inventory A and B trust each other, the current cross-inventory authentication is considered unnecessarily redundant.
How can these service inventory architectures be improved to avoid redundant authentication?

A. A trust relationship needs to be established between the two authentication brokers.
This trust relationship can enable the authentication brokers to accept Kerberos tickets issued by each other.

B. Create a single, enterprise-wide service inventory by merging Service Inventories A and B.
Instead of the current Kerberos-based brokered authentication, the merged service inventory can use X.509 digital certificates to remove the burden from the local authentication brokers. Designate either Service C or Service F as the central authentication service with the responsibility to validate service consumer X.509 digital certificates. After successful validation, the authentication service can issue a signed SAML token to be used within the entire service inventory.

C. Replace Services C and F with a single authentication broker so that one single token can be used with services across both service inventories. This can be achieved by merging the content of the two identity stores.

D. The same Kerberos tickets can be used across both service inventories by updating the security policies of the services that require Kerberos tickets. Because each authentication broker issues Kerberos tickets, the only difference between these tickets is the identity of the issuer. For example, because services in Service Inventory A already accept Kerberos tickets issued by Service C, Service F just needs to be included in the security policies of these services. Similarly, services in Service Inventory B that accept Kerberos tickets issued by Service F need to include the acceptance of Kerberos tickets issued by Service C in their security policies.

正確答案: A

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