Arcitura Education SOA Security Lab S90.20 Exam Questions

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Total 30 questions

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Question 1

Service A exchanges messages with Service B multiple times during the same runtime service activity. Communication between Services A and B has been secured using transport-layer security. With each service request message sent to Service B (1A .IB), Service A includes an X.509 certificate, signed by an external Certificate Authority (CA). Service B validates the certificate by retrieving the public key of the CA (2A .2B) and verifying the digital signature of the X.509 certificate. Service B then performs a certificate revocation check against a separate external CA repository (3A, 3B). No intermediary service agents reside between Service A and Service B .

To fulfill a new security requirement, Service A needs to be able to verify that the response message sent by Service B has not been modified during transit. Secondly, the runtime performance between Services A and B has been unacceptably poor and therefore must be improved without losing the ability to verify Service A's security credentials. It has been determined that the latency is being caused by redundant security processing carried out by Service B .Which of the following statements describes a solution that fulfills these requirements?

AApply the Trusted Subsystem pattern to introduce a utility service that performs the security processing instead of Service B .The utility service can verify the security credentials of request messages from Service A and digitally sign messages sent to Service A to enable verification of message integrity. Furthermore, the utility service can perform the verification of security credentials submitted by Service A only once per runtime service activity. After the first message-exchange, it can issue a SAML token to Service A that gets stored within the current session. Service A can then use this session-based token with subsequent message exchange. Because SAML tokens have a very small validity period (in contrast to X.509 certificates), there is no need to perform a revocation check with every message exchange.

BService B needs to be redesigned so that it performs the verification of request messages from Service A only for the first message exchange during the runtime service activity. Thereafter, it can issue a SAML token to Service A that gets stored within the current session. Service A then uses this session-based token with subsequent message exchanges. Because SAML tokens have a very small validity period (in contrast to X.509 certificates), there is no need to perform a revocation check with every message exchange.

CWS-Security-Policy transport binding assertions can be used to improve performance via transport-layer security Tkhe use of symmetric keys can keep the encryption and decryption overhead to a minimum, which will further reduce the latency between Service A and Service B .By encrypting the messages, attackers cannot modify message contents, so no additional actions for integrity verification are needed.

DThe Data Origin Authentication pattern can be applied together with the Service Perimeter Guard pattern to establish a perimeter service that can verify incoming request messages sent to Service B and to filter response messages sent to Service A .The repository containing the verification information about the Certificate Authorities can be replicated in the trust domain of the perimeter service. When access is requested by Service A, the perimeter service evaluates submitted security credentials by checking them against the locally replicated repository. Furthermore, it can encrypt messages sent to Service A by Service B .and attach a signed hash value.

Answer : A

Question 2

Services A, B, and C reside in Service Inventory A and Services D, E, and F reside in Service Inventory B .Service B is an authentication broker that issues WS-Trust based SAML tokens to Services A and C upon receiving security credentials from Services A and C .Service E is an authentication broker that issues WS-Trust based SAML tokens to Services D and F upon receiving security credentials from Services D and E .Service B uses the Service Inventory A identify store to validate the security credentials of Services A and C .Service E uses the Service Inventory B identity store to validate the security credentials of Services D and F .To date, the two service inventories have existed independently from each other. However, a requirement has emerged that the services in Service Inventory A need to be able to use the services in Service Inventory B, and vice versa. How can cross-service inventory message exchanges be enabled with minimal changes to the existing service inventory architectures and without introducing new security mechanisms?

ABecause SAML tokens cannot be used across multiple security domains, authentication brokers C and E need to be replaced with one single authentication broker so that one token issuer is used for all services across both of the service inventories.

BThe current security mechanism already fulfills the requirement because SAML tokens can be used across multiple security-domains. The only change required is for each authentication broker to be configured so that it issues service inventory-specific assertions for SAML tokens originating from other service inventories.

CThe individual domain service inventories need to be combined into one enterprise service inventory. The Service Perimeter Guard pattern can be applied to establish a contact point for request messages originating from outside the service inventory. Within the service inventory, services no longer need to be authenticated because they are all part of the same trust boundary.

DThe Trusted Subsystem pattern is applied to encapsulate Services B and E using a central utility service that balances request and response messages exchanged between Services B and E, depending on which service inventory the messages originate from. The utility service also contains transformation logic to ensure that the SAML tokens issued by Services B and E are compatible. This guarantees that an issued SAML token can be used across Service Inventories A and B without further need for runtime conversion.

Answer : B

Question 3

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?

AUse 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.

BUse 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 .

CUse 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.

DUse 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.

Answer : C

Question 4

Service A provides a data retrieval capability that can be used by a range of service consumers, including Service Consumer A, In order to retrieve the necessary data. Service Consumer A first sends a request message to Service A (1). Service A then exchanges request and response messages with Service B (2, 3). Service C (4, 5), and Service D (6. 7). After receiving all three response messages from Services B .C .and D, Service A assembles the collected data into a response message that it returns to Service Consumer A (8). The Service A data retrieval capability has been suffering from poor performance, which has reduced its usefulness to Service Consumer A .Upon studying the service composition architecture, it is determined that the performance problem can be partially attributed to redundant validation by service contracts for compliance to security policies. Services B and C have service contracts that contain the same two security policies. And, Service D has a service contract that contains a security policy that is also part of Service A's service contract. What changes can be made to the service contracts in order to improve the performance of the service composition while preserving the security policy compliance requirements?

AApply the Policy Centralization pattern in order to establish a single security policy for the entire service composition. The-redundant policies residing in the service contracts of Services A .B, C and D need to be removed and grouped together into one master policy definition enforced by Service A .This way, redundant policy validation is eliminated, thereby improving runtime performance.

BApply the Policy Centralization pattern in order to establish two centralized policy definitions and ensure that policy enforcement logic is correspondingly centralized. The first policy definition includes the redundant security policies from Services A and D and the second policy definition contains the redundant security policies from Services B and C .

CAll policies are analyzed for similarities, which are then extracted and, by applying the Policy Centralization pattern, combined into a single policy definition. This 'meta-policy' is then positioned to perform validation of the response message generated by Service A, prior to receipt by Service Consumer A .If validation fails, an alternative error message is sent to Service Consumer A instead.

DApply the Standardized Service Contract principle in order to remove redundancy within service contracts by ensuring that all four service contracts comply with the same policy standards. This further requires the application of the Service Abstraction principle to guarantee that policy definitions are sufficiently streamlined for performance reasons.

Answer : B

Question 5

Service A provides a data access capability that can be used by a variety of service consumers. The database records accessed by Service A are classified as either private or public. There are two types of service consumers that use Service A:

Service consumers with public access permissions (allowed to access only public data records) and service consumers with private access permissions (allowed to access all data records). For performance reasons the Service A architecture uses a single database, named Database A .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?

AThe 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

BThe 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.

CThe 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.

DWhen 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.

Answer : A

Question 6

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?

ATo 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.

BApply 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.

CApply 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.

DApply 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.

Answer : B

Question 7

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 its service consumer (8).

This service composition was recently shut down after it was discovered that Database A had been successfully attacked twice in a row. The first type of attack consisted of a series of coordinated request messages sent by the same malicious service consumer, with the intention of triggering a range of exception conditions within the database in order to generate various error messages. The second type of attack consisted of a service consumer sending request messages with malicious input with the intention of gaining control over the database server. This attack resulted in the deletion of database records and tables. An investigation revealed that both attacks were carried out by malicious service consumers that were authorized. How can the service composition security architecture be improved to prevent these types of attacks?

AApply the Data Confidentiality pattern together with the Data Origin Authentication pattern. This establishes message-level-security so that all messages are encrypted and digitally signed. Secondly, the Service A logic must be enhanced so that it can keep track of the trustworthiness of its service consumers If a request message originated from a trustworthy service consumer, then the request message is processed as normal. If the request message originates from a non-trustworthy service consumer, then the request message is rejected and an error message is returned to the service consumer.

BApply the Service Perimeter Guard pattern together with the Trusted Subsystem pattern. This establishes a perimeter service between Database A and any service that requires access to it (including Services B and C). The perimeter service evaluates incoming data requests and filters out those that can introduce a security risk. Only request messages issued by authorized services and service consumers are forwarded to Database A .Responses originating from Database A are further evaluated by the trusted subsystem to remove any unauthorized data. The two patterns together ensure that only authorized data is returned to the service consumer and that no request messages present a security threat to Database A.

CApply the Exception Shielding pattern together with the Message Screening pattern. This establishes new logic within Service A that screens incoming request messages for data-driven attacks (such as SQL injection and X-Path injection attacks), and also evaluates whether exception details returned by Database A contains potentially confidential or unsafe information. Any inappropriate exception information is replaced with sanitized content.

DApply the Trusted Subsystem pattern to protect Database A from data-driven attacks and to evaluate whether database-responses contain inappropriate data. The trusted subsystem maintains a snapshot of Database A and executes the original service consumer's request message against the snapshot. The processing logic that accesses the snapshot has limited privileges in order to prevent malicious attacks from overtaking the database. If no security violation is detected during the processing of the snapshot, then the original service consumer's request is forwarded to Database A .If an error message is generated during the processing of the snapshot, then it is returned to the original service consumer and the request is not forwarded to Database A .Because the error message was generated on the snapshot, it cannot contain unsafe information about Database A.

Answer : C