SOA S90.20 actual dump : SOA Security Lab

Service A provides a customized report generating capability. Due to infrastructure limitations, the number of service consumers permitted to access Service A concurrently is strictly controlled. Service A validates request messages based on the supplied credentials (1). If the authentication of the request message is successful, Service A sends a message to Service B (2) to retrieve the required data from Database A (3). Service A stores the response from Service B (4) in memory and then issues a request message to Service C (5). Service C retrieves a different set of data from Database A (6) and sends the result back to Service A (7). Service A consolidates the data received from Services B and C and sends the generated report in the response message to the service consumer (8).

It has been discovered that attackers have been gaining access to confidential data exchanged between Service A and Service B, and between Service A and its service consumers. What changes can be made to this service composition architecture in order to counter this threat?

• A. None of the above
• B. Apply the Service Perimeter Guard pattern in order to protect message exchanges between Service A and its service consumers. Apply the Direct Authentication pattern in order to protect message exchanges between Service A and Service B.
• C. Apply the Data Origin Authentication pattern to protect the final report sent by Service A to its service consumer. Service A can generate a message digest of the final report, after which it can sign the digest with its own private key. It then can send both the final report and the signed message digest to its service consumer. This service consumer can generate its own message digest, decrypt the signed digest using the public key of Service A (which proves that Service A sent the message), and then compare the two digests. If the digests match, it guarantees that the final report was not tampered with during transmission.
• D. Apply the Direct Authentication pattern in order to protect message exchanges between Service A and its service consumers and between Service A and Service B.
  This approach will establish a password-based authentication mechanism that relies on a local identity store and will therefore prevent access by attackers.

Service Consumer A sends a request message to Service A (1), after which Service A sends a request message to Service B (2). Service B forwards the message to have its contents calculated by Service C (3). After receiving the results of the calculations via a response message from Service C (4), Service B then requests additional data by sending a request message to Service D (5). Service D retrieves the necessary data from Database A (6), formats it into an XML document, and sends the response message containing the XML-formatted data to Service B (7).
Service B appends this XML document with the calculation results received from Service C, and then records the entire contents of the XML document into Database B (8). Finally, Service B sends a response message to Service A (9) and Service A sends a response message to Service Consumer A (10).

Services A, B and D are agnostic services that belong to Organization A and are also being reused in other service compositions. Service C is a publicly accessible calculation service that resides outside of the organizational boundary. Database A is a shared database used by other systems within Organization A and Database B is dedicated to exclusive access by Service B.
Service B has recently been experiencing a large increase in the volume of incoming request messages. It has been determined that most of these request messages were auto-generated and not legitimate. As a result, there is a strong suspicion that the request messages originated from an attacker attempting to carry out denial-of-service attacks on Service B.
Additionally, several of the response messages that have been sent to Service A from Service B contained URI references to external XML schemas that would need to be downloaded in order to parse the message data. It has been confirmed that these external URI references originated with data sent to Service B by Service C.
The XML parser currently being used by Service A is configured to download any required XML schemas by default. This configuration cannot be changed.
What steps can be taken to improve the service composition architecture in order to avoid future denial-of-service attacks against Service B and to further protect Service A from data access-oriented attacks?

• A. Apply the Service Perimeter Guard pattern to establish a perimeter service between Service B and Service C.
  Apply the Brokered Authentication pattern by turning the perimeter service into an authentication broker that is capable of ensuring that only legitimate response messages are being sent to Service C from Service B Further apply the Data Origin Authentication pattern to enable the perimeter service to verify that messages that claim to have been sent by Service C actually originated from Service C.
  Apply the Message Screening pattern to add logic to the perimeter service to also verify that URIs in request messages are validated against a list of permitted URIs from where XML schema downloads have been pre-approved.
• B. Apply the Data Origin Authentication pattern so that Service B can verify that request messages that claim to have been sent by Service A actually did originate from Service A.
  Apply the Message Screening pattern to add logic to Service A so that it can verify that external URIs in response messages from Service B refer to trusted sources.
• C. Apply the Direct Authentication pattern so that Service C is required to provide security credentials, such as Username tokens, with any response messages it sends to Service B.
  Furthermore, add logic to Service A so that it can validate security credentials passed to it via response messages from Service B.
  by using an identity store that is shared by Services A and B.
• D. Apply the Service Perimeter Guard pattern and the Message Screening pattern together to establish a service perimeter guard that can filter response messages from Service C before they reach Services A and B.
  The filtering rules are based on the IP address of Service C.
  If a request message originates from an IP address not listed as one of the IP addresses associated with Service C.
  then the response message is rejected.

• A. The service consumer's request message containing the ID value can be encrypted by inserting the private key of the service consumer into the data. Because all service consumers have different private keys, this approach will lead to different encrypted values, even if the plain text ID values are the same. As a result, two data items with the same encrypted unique identifier cannot exist.
• B. The database rules are changed so that the ID value of database records no longer needs to be unique. As a further precaution, the Service A logic is changed to disallow the update of private database records by service consumers with only public access permissions.
• C. When Service A detects that a service consumer with public access permissions has submitted an ID value that already exists within a private database record, it stores the service consumer's ID value in a temporary database and returns a response message indicating that the update was successful. A notification message is then sent to a human database administrator who manually contacts the owner of the service consumer in order to explain that the ID value submitted cannot be accepted because it already exists within a private database record.
• D. Each record in Database A is classified as either private or public. After Service A is invoked by a service consumer (1), it authenticates the request message using an identity store and retrieves the corresponding authorization (2, 3). Once authorized, the service consumer's request is submitted to Database A (4), which then returns the requested data (5) If the service consumer has private access permissions, all of the returned data is included in Service A's response message (6). If the service consumer has public access permissions, then Service A first filters the data in order to remove all unauthorized private data records before sending to the response message to the service consumer (6).
  
  In addition to retrieving data, Service A's data access capability can be used to update database records. An investigation recently revealed an information leakage problem that can occur when service consumers with public access permissions attempt to update the ID value of a database record The ID values of all database records (private or public) must be unique. When a service consumer with public access permissions updates a public database record with an ID value that is already assigned to a private database record, the database returns an error message describing this conflict. This error text reveals confidential information by stating that the ID value submitted by the service consumer with public access permissions already exists within a private database record.
  What steps can be taken to avoid this problem while preserving the requirement that all database records (private and public) have unique ID values?
• E. The Exception Shielding pattern is applied to replace the error description text before a response message is returned to the service consumer. Furthermore, the ID value of all database records is appended with a code indicating whether the database record is private or public