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SOA Security Lab: S90-20A Exam
S90-20A Questions & Answers
Exam Code: S90-20A
Exam Name: SOA Security Lab
Q & A: 35 Q&As

QUESTION 1
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?
A. A 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.
B. Service 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.
C. Services 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.
D. The 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

QUESTION 2
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?
A. Apply 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.
B. Service 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
C. 509 certificates), there is no need to perform a revocation check with every message exchange.
D. WS-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
D .By encrypting the messages, attackers cannot modify message contents, so no additional
actions for integrity verification are needed.
E. The Data Origin Authentic     ation 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 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?
A. Apply 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. B. Apply 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
C. Apply 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 identitystore. 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.
D. Apply 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?
A. Apply 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.
B. Apply 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.
C. Apply 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.
D. Apply the Trusted Subsystem pattern to protect Database A from data-driven attacks and to evaluate whether database-responses contain inappropriate dat
E. 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 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?
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
systemeitherperforms the necessary processing orsends 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.
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.
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.
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.
Answer: B

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