Arcitura Education S90.20 SOA Security Lab Exam Practice Test

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Total 30 questions

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Question 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. The owner of Service C is planning two changes to the service architecture:

1. A fee will be charged to Service Consumer A (or any service consumer) using Service C .2. The response messages issued by Service C need to be secured in order to prevent unauthorized access. An analysis of Service C's usage statistics reveals that a group of service consumers specifically request the retrieval of multimedia data on a frequent basis. To promote the usage of Service C to these types of service consumers, the owner of Service C plans to offer a special discount by allowing unlimited multimedia retrievals for a fixed monthly price. Service consumers that do not subscribe to this promotion will need to pay for each request individually. It is anticipated that the new promotion will significantly increase the usage of Service C .The owner of Service C therefore wants to ensure that the security added to the response messages has a minimal impact on Service C's runtime performance. What steps can be taken to fulfill these requirements?

AUse symmetric session keys so that for each response message, Service C generates a session key and encrypts the-response message using this session key. The session key is then encrypted (using the service consumer's public key) and attached to the encrypted response. A single session key can then be used by Service C for communication with all service consumers that subscribe to the promotion.

BBecause the services in this service composition already rely on public key encryption to provide authentication, Service C can provide message confidentiality by encrypting the response message with Service Consumer A's public key. This will ensure that only the intended recipient, in possession of the corresponding private key, can decrypt the response message. To further reduce the performance impact of encryption, Service C can generate a new public-private key pair to be used by service consumers subscribed to the promotion. By securely distributing the private key to each of these service consumers, Service C only needs to encrypt the response messages once with the public key.

CDesign Service C to generate a message digest of the response message and encrypt it with the service consumer's publickey. Because the message digest is typically small, the performance of public key encryption is acceptable. This approach also ensures that only the service consumer can decrypt the response message using the corresponding private key.

DDesign the service composition architecture so that the encryption of the response messages is performed by Service B and Service C .To reduce the performance impact, a policy can be added to Service A's service contract in order to require the encryption of all response messages, regardless of the type of service consumer making the request. Further, a new utility service can be added to the service composition. This service can be responsible for obtaining the public key of the service consumer and forwarding the key along with the request message to the appropriate service (Service B or Service C). The service receiving the message can then encrypt the response message with the received public key. Service A can then forward the encrypted response to the service consumer. This approach ensures that only authorized service consumers will be able to access response messages.

Answer : A

Question 2

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). An investigation recently detected that private data has been leaked to unauthorized service consumers. An audit of the Service A architecture revealed that Service A's filtering logic is flawed, resulting in situations where private data was accidentally shared with service consumers that only have public access permissions. Further, it was discovered that attackers have been monitoring response messages sent by Service A in order to capture private data. It is subsequently decided to split Database A into two databases:

one containing only private data (the Private Database) and the other containing only public data (the Public Database). What additional changes are necessary to address these security problems?

AThe Service A logic needs to be modified to work with the two new databases. Service A needs to be able to access the Public Database and the Private Database when it receives a request message from a service consumer with private access permissions, and it must only access the Public Database when it receives a request message from a service consumer with public access permissions. Furthermore, any response messages issued by Service A containing private data need to be encrypted.

BA utility service needs to be created and positioned between Service A and the service consumer. The utility service can-contain screening logic that can verify the service consumer's credentials and then forward the request message to the Private Database or to the Public Database, depending on the service consumer's access permissions. Because each request message is evaluated by the database, no filtering of the returned data is necessary. The data is sent back to the consumer in a response message encrypted using symmetric key encryption.

CAfter the service consumer's request message is authenticated. Service A can generate a onetime symmetric encryption key that it sends to the service consumer. This key is encrypted by the public key of the service consumer. After the service consumer acknowledges the receipt of the one-time encryption key, Service A forwards the service consumer's data access request (and the corresponding credentials) to both databases. After receiving the responses from the databases, Service A compiles the results into a single response message. This message is encrypted with the one-time key and sent by Service A to the service consumer.

DThe Service A architecture can be enhanced with certificate-based authentication of service consumers in order to avoid dependency on the identity store. By using digital certificates, Service A can authenticate a service consumer's request message and then forward the data access request to the appropriate database. After receiving the responses from the databases, Service A can use the service consumer's public key to encrypt the response message that is sent to the service consumer.

Answer : A

Question 3

Service Consumer A sends a request message to Service A (1), after which Service A sends a request message with security credentials to Service B (2). Service B authenticates the request and, if the authentication is successful, writes data from the request message into Database B (3). Service B then sends a request message to Service C (4), which is not required to issue a response message. Service B then sends a response message back to Service A (5). After processing Service B's response, Service A sends another request message with security credentials to Service B (6). After successfully authenticating this second request message from Service A, Service B sends a request message to Service D (7). Service D is also not required to issue a response message. Finally, Service B sends a response message to Service A (8), after which Service A records the response message contents in Database A (9) before sending its own response message to Service Consumer A (10).

Services A and B use digital certificates to support message integrity and authentication. With every message exchange between the two services (2, 5, 6, 8), the digital certificates are used. It has been determined that both Databases A and B are vulnerable to malicious attackers that may try to directly access sensitive data records. Furthermore, performance logs have revealed that the current exchange of digital certificates between Services A and B is unacceptably slow. How can the integrity and authenticity of messages exchanged between Services A and B be maintained, but with improved runtime performance - and - how can Databases A and B be protected with minimal additional impact on performance?

AApply the Brokered Authentication pattern to establish an authentication broker that uses WS-Trust based SAML tokens for message exchanges between Services A and B .This eliminates the need for Service A to be repeatedly authenticated by Service B .Use the public key of Service A to encrypt Database A and use the public key of Service B to encrypt Database B.

BApply the Brokered Authentication pattern to establish an authentication broker that uses WS-Secure-Conversation Security-context tokens (SCTs) to generate and transmit a symmetric session key. The session key is used to encrypt and digitally sign messages exchanged between Services A and B .For each database the Trusted Subsystem pattern is applied to require authenticated access to the database and to prevent attackers from accessing the database directly

CApply the Direct Authentication pattern to establish mutual authentication between Services A and B using a shared identity store. Service A attaches a Username token to the first request message sent to Service B and Service B authenticates the request message using the shared identity store. Similarly, when Service B submits a response message to Service A .it attaches its own Username token that Service A then authenticates by also using the same shared identity-store. Database A is encrypted using the Service A password as a secret encryption key and Database B is encrypted using the Service B password as a secret encryption key.

DApply the Brokered Authentication pattern to establish an authentication broker that uses WS-Trust based SAML tokens for message exchanges between Services A and B .This eliminates the need for Service A to be repeatedly authenticated by Service B .Database A is encrypted using the Service A password as a secret encryption key and Database B is encrypted using the Service B password as a secret encryption key.

Answer : B

Question 4

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

Question 5

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 6

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 7

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 .

Component B is considered a mission critical program that requires guaranteed access to and fast response from Database A .Service A was recently the victim of a denial of service attack, which resulted in Database A becoming unavailable for extended periods of time (which further compromised Component B). Additionally, Services B, C, and D have repeatedly been victims of malicious intermediary attacks, which have further destabilized the performance of Service A .How can this architecture be improved to prevent these attacks?

AA utility service is created to encapsulate Database A and to assume responsibility for authenticating all access to the database by Service A and any other service consumers. Due to the mission critical requirements of Component B, the utility service further contains logic that strictly limits the amount of concurrent requests made to Database A from outside the organizational boundary. The Data Confidentiality and Data Origin Authentication patterns are applied to all message exchanged within the external service composition in order to establish message-layer security.

BService Consumer A generates a private/public key pair and sends this public key and identity information to Service A .Service A generates its own private/public key pair and sends it back to Service Consumer A .Service Consumer A uses the public key of Service A to encrypt a randomly generated session key and then sign the encrypted session key with the private key. The encrypted, signed session key is sent to Service A .Now, this session key can be used for secure message-layer communication between Service Consumer A and Service A .The Service Perimeter Guard pattern is applied to establish a perimeter service that encapsulates Database A in order to authenticate all external access requests.

CServices B, C, and D randomly generate Session Key K, and use this key to encrypt request and response messages with symmetric encryption. Session Key K is further encrypted itself asymmetrically. When each service acts as a service consumer by invoking another service, it decrypts the encrypted Session Key K and the invoked service uses the key to decrypt the encrypted response. Database A is replicated so that only the replicated version of the database can be accessed by Service A and other external service consumers.

DThe Direct Authentication pattern is applied so that when Service Consumer A submits security credentials, Service A will be able to evaluate the credentials in order to authenticate the request message. If the request message is permitted, Service A invokes the other services and accesses Database A .Database A is replicated so that only the replicated version of the database can be accessed by Service A and other external service consumers.

Answer : A