chapter 9 transactions and reliable sessions ms 304 wxmla 1 wcf transactions reliable messaging...

Chapter 9 Transactions and Reliable Sessions

MS 304 WXMLA

1

WCF Transactions Reliable Messaging Sessions

TransactionsOverview

Group of one or more unit of operations executed as whole.

Logical unit of work. Balance Transfer of 5000 from Account1 to

Account21. Debit of 5000 from Account1.(bal=bal-5000)2. Credit of 5000 in Account 2.(bal=bal+5000).

Both operations should be part of single unit.

MS 304 WXMLA

2

If either of the operations fail entire transaction should be rolled back.(It should be in the state before balance transfer).

A Transaction has following properties: 1. Atomic : All or one. Single unit (Remember Atom).2. Consistent: Outcome should be as per expected.

For example if Account 1 has 10000 and Account2 has 3000 then at the end of transaction Account 1 should have 5000 and Account should have 8000.

MS 304 WXMLA

3


3. Isolated : Private until it is committed. For ex: During balance transfer(not completed and not committed) if any relative of Account1 or Account2 checks balance from ATM then they would see 10000 Rs for Account1 and 3000 Rs for Account2.

4. Durable: Transaction must service failures. When a transaction is committed it should maintain that state even if there is a failure. For ex: After successful balance transfer(committed) if some shuts down bank server, then after restart a transaction must be in committed state.

MS 304 WXMLA

4


Transaction Attribute in System.ServiceModel .NET 2.0 introduced new namespace

System.Transactions. WCF utilizes many available object of this

name space for all necessary transaction capabilities.

* Transaction in .NET 3.0 – ProWCF – A Press Book pages 280 to 282 *

MS 304 WXMLA

5


Additional Details Enable transaction in binding. Use binding that supports transaction.

- WSHttpBinding, NetTcpBinding, NetNamedPipeBinding, WSDualHttpBinding

Transaction Protocols - OleTransactions: Optimal for .Net- Web Service Atomic Transaction- Use when Clients are not .Net

MS 304 WXMLA

6


ServiceBehavior Attribute TransactionAutoCompleteOnSessionClos

e TransactionIsolationLevel TransactionTimeOutOperationBehavior Attribute TransactionAutoComplete TransactionScopeRequired

MS 304 WXMLA

7


TransactionFlow Attribute Specifies whether an operation should be a part of

transaction or not. Single property which comes from

TransationFlowOption enum.- Allowed: Transaction may be flowed (not compulsory)

- Mandatory: Transaction must be flowed(compulsory) - NotAllowed: Tranasaction cannot be

flowed(operation can’t be used in transaction (transaction scope).

MS 304 WXMLA

8


MS 304 WXMLA

9


Default is NotAllowed.

WS-Atomic Transaction WS-AT is useful to flow transactions to other

applications. It is interoperable protocol. Enables two-phase commit protocol. No need to use it if you are using Microsoft

Technology.Specifying Transactions through config- Just set transactionFlow=true in binding (refer

demo).

MS 304 WXMLA

10


MS 304 WXMLA

11

TransactionsSummary

What is reliable messaging?- A mechanism to successfully deliver

messages in between distributed applications even if there is a failure of dependent components.

MS 304 WXMLA

12

Reliable Sessions

Reliable sessions in WCF provides reliable transfer of messages from one point to another, from source to destination.

Reliable messaging must be ensured in case of any failure like network or transport failure.

WCF inherits its reliable messaging from implementation of SOAP reliable messaging protocol.

MS 304 WXMLA

13

Reliable SessionsOverview

Reliable messaging enabled by including <reliableSession> element to the binding (in config) and setting enabled attribute to true.

Demo Reliable Messaging support:NetTcpBinding, wsHttpBinding,

*NetNamedPipeBinding, *wsDualHttpBinding, wsFederationBinding, *MsmqIntegrationBinding- * have reliable messaging enabled by default.

MS 304 WXMLA

14

Reliable SessionsMessage Exchange

Messages can be secured by using one of the in-build bindings.

Securing session requires that a client and service must be configured to exchange messages inside a reliable session and set of credentials to authenticate service.

Steps1. Configure binding for reliable session.2. add <security> element to that binding. 3. Inside <security> element the clientCredentialType attribute of the <message> needs to be set.

MS 304 WXMLA

15

Reliable SessionsSecuring Messages

Credentials while using transport- None:- Basic: Basic authentication is required for client.- Digest,Ntlm, Windows, Certificate: via X.509 certificate

Credentials while using message- None, Windows- UserName: Authentication via username.- Certificate: X.509- IssuedToken: Authentication via custom token.

MS 304 WXMLA

16


Specifying None is ok for testing but it does not enforce security. It is like blank password.

WCF does not allow cryptographic data with username credential. But it ensures transport security.

More about security in chap 10.

MS 304 WXMLA

17


Concept of queue is to provide reliable communication between sender and receiver, in case of failure.

Direct transport protocols such as TCP or HTTP offer little or not guarantee for safe and successful msg delivery if either client or service fails.

In direct transfer both parties should be running. In Queued transport provides isolation between sender

and receiver so if either party fails communication continues.

Good metaphore is telephone conversation using voice mail.

MS 304 WXMLA

18

Reliable SessionsQueues

WCF provides MSMQ as transport for queuing. Reliable messaging is provided even if there is a

network failure or other crash on sender/receiver. The role of queue is to catch any message in between

sender and receiver and send it to correct destination. WCF recommends queue in following scenarios:

- Disconnected operations: If either party is disconnected.- Loosely coupled applications: Speed of sender or receiver does not matter as both might not be online at the same time.

MS 304 WXMLA

19


- Disconnected operations: If either party is disconnected.- Loosely coupled applications: Client is not dependent on running service.- Load Leveling: Fast sender and slow receiver.- Failure isolation: Failure of sender or receiver does not affect other party.

A queue manager manages a collection of queues. It manages all queue operations. Basic queue behavior is shown as:

MS 304 WXMLA

20


1. client sends message to queue. Address on message is address of target queue.

2. The client’s queue manager sends messages to outgoing queue.

3. The client’s queue manager finds target queue and sends message to target queue.

4. The receiving application quests a message from target queue.

5. The queue manager of target queue hands the message to receiving application.

MS 304 WXMLA

21


Queues can also support transactional messaging.

In that case if messages sent and received from queue within transaction and if transaction is rolled back then result would be if no messages are sent to or received from queue.

MS 304 WXMLA

22


WCF includes two built-in bindings for message queuing: NetMsmqBinding and MsmqIntegrationBinding. NetMsmqBinding supports some subset of MSMQ.

Contains various properties. ExactlyOnce property ensures that message

will not be duplicated if it is already delivered. The dead letter queue is a queue which stores

messages which are not delivered some how and the reason will be recorded in that queue.

MS 304 WXMLA

23

Reliable SessionsWCF and Queues

Points to consider while using WCF queued bindings:- Service operations must be one way.- Generating WCF client using metadata exchange requires an additional HTTP endpoint on service.- Additional configuration outside WCF might be required.

MS 304 WXMLA

24


Queuing Best Practices Reliable Transfer: Make sure that ExactlyOnce and

Durable properties are set to true. Transactions: Using Transactions ensures end-to-

end reliability by ensuring that message was received.

Use dead letter queues: Required for reliable messaging. Message delivery can fail due to network failure, authentication failure or any other failure. Dead letter queues make sure that you are notified if message is not delivered.

MS 304 WXMLA

25


MS 304 WXMLA

26

Summary

Chap 10 Security WCF Security overview Security behaviors Clients/Services Best Practices

MS 304 WXMLA

27

Security overview SOAP message is communicated

between client and service. Securing and safe delivery of message

important. Intruder problem: Discuss WCF provides robust and versatile

secure messaging infrastructure.

MS 304 WXMLA

28

Security overviewConcepts

Integrity Confidentiality Authentication Authorization

MS 304 WXMLA

29


Integrity Message arrives at receiver is not altered. You need to trust that a message is not

tempered between sender and receiver. Digitally signing a message can ensure

integrity.Confidentially Message is sent to intended recipient. Message should not be viewed or interrogated

while in transit between sender and receiver.MS 304 WXMLA

30


Authentication Requesting evidence of identity. Client and

service have identity Generally one sided. In distributed system it should be on both

sides. Keeping it on both sides ensures there is no

middle-man attack.Authorization Happens after authentication. Like rights. Permission to call service.MS 304 WXMLA

31


For ex: Login in windows – Authenticationand accessing resources of network : authorization takes place (students are not allowed to access certain network folder while faculties are .)

WCF follows following mechanisms:- Windows Identity: - Public key Infrastructure: PKI employs digital

certificate.- X.509: Main form to credentials.- Kerberos: Used in Windows domain.

MS 304 WXMLA

32


Security Mechanism Transport Level Security

-Security is based on OS level.- Encryption is based on binding.- HTTPs(Secure Socket Layer – SSL).- TCP (Transport layer security).- Can require client to pass credentials to do authentication.

MS 304 WXMLA

33


Message Level Security- Messages are signed and encrypted before sending.- Based on WS-Security standard.- Can require client to pass credentials to do authentication.

TransportWithMessageCredential : mix

MS 304 WXMLA

34


Difference

MS 304 WXMLA

35

Transport Level Message LevelPro: Faster, Provides benefit from h/w level acceleration

Con: Slower

Con: Provides point-to-point encryption, so if service forward message then it is not encrypted.

Pro: Provides end-to-end encryptionPro: More option for credentials.

Con: Requires support for XML and WS-Security


Default security settings BasicHttpBinding

- No Security- For interoperability

WsHttpinding- Message level security.- Messages are encrypted.

NetTcpBinding - Trasport level security.Demo

MS 304 WXMLA

36

Security overviewWhy WCF Security

WCF provides strong security mechanism for distributed applications.

It accomplishes it by dividing security in three distinct functional areas:- Transfer Security- Access Control- Auditing

MS 304 WXMLA

37


WCF provides strong security mechanism for distributed applications.

It accomplishes it by dividing security in three distinct functional areas:- Transfer Security- Access Control- Auditing

MS 304 WXMLA

38


Transfer Security- For message integrity, confidentially and authentication.- Modes:- None: - Message: SOAP message security. Messages are security using WS-security standards. It ensures CIAtifor sender and receiver.- Transport: Transport security to ensure CIAti.- Mixed: Message and Transport security

MS 304 WXMLA

39


- Mixed: Message and Transport security.- Both: Available in netMsmqBinding binding. Provides authentication and protection on both levels.

Control Access/ Authorization- Authorization by using- PrinciplePermissionAttribute - ASP.NET Membership provides- ASP.NET role provider- Authorization Manager- Identity Model.

MS 304 WXMLA

40


Auditing- Process of logging security events.- Security events are written to the Windows Event Log and include evens such as logon successes and failures.- Helpful to Administrators to find attacks.

MS 304 WXMLA

41

Security Credentials

Transport Credentials- None: Anonymous client.- Basic: User name and password against active

directory(HTTP only). Password in unencrypted form.

- Digest: Only works with Windows active directly account. Sending hash value over network.

- NTLM: Uses SSPI(Security Support provide Interface)

- Windows: Windows Authentication.- Certificate: Authentication using X.509

MS 304 WXMLA

42


Message Credentials- None: Anonymous client.- Windows: Windows Authentication.- UserName: Client to be authenticated by

using username.- Certificate: Authentication using X.509- Windows Cardspace: Authentication using

Windows card space.- - All these credentials can be specified

by code or config.MS 304 WXMLA

43


Authentication Demo Authorization Demo

Summary

MS 304 WXMLA

44

MS 304 WXMLA

45

MS 304 WXMLA

46

MS 304 WXMLA

47

chapter 9 transactions and reliable sessions ms 304 wxmla 1 wcf transactions reliable messaging...

Documents