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Role-Based Security (RBS)

As a consumer of Serviced Components, always call Dispose on an instance when you re finished with it. The easiest way to do this is to use the using statement. This guarantees Dispose gets called on the type, regardless of your error-handling semantics. private static void ExPool() { string[] tables = { "authors", "employee", "titles", "publishers","sales" }; Random r = new Random(); using (Poolable p = new Poolable()) { for (int i = 1; i < 10; i++) { string s = string.Format( "select * from {0}", tables[r.Next(tables.Length - 1)]); DataSet ds = p.GetSomeData(s); } } //Dispose called automatically when 'using' goes out of scope } If you re creating Serviced Components you can control instance lifetimes by using JITA (see previous section on JITA). Instead of explicitly calling DeactivateOnReturn from each method implementation, you also have the option of simply flagging your class with the AutoComplete attribute. This attribute will guarantee instances are disposed of after a method completes. If your type is not JITA-enabled, the AutoComplete attribute will be ignored.

Table 6-3 provides a summary of when constructors and destructors are called. Table 6-3. Constructors and Destructors

Addressing information can be sensitive, especially when it contains port numbers and references to qualified endpoints. We are used to thinking of this information as being public because Web services are often publicly accessible. But with WS-Addressing, this information is attached to the SOAP message header directly. You typically do not want the body of the SOAP message to be tampered with or viewed by unauthorized parties. In the same way, you should feel equally protective about the SOAP message headers. Another sensitive case is when messages are routed between multiple endpoints, each of which writes additional WS-Addressing information to the message header. The additional endpoints may not be designed to handle direct service requests from outside clients. Their addressing information needs to be kept protected. There are three recommended options for securing the contents of a message that contains addressing headers: 1. Digitally sign the message, including the body and header information. 2. Encrypt the message headers. 3. Add a message ID. Digital signing allows you to detect whether a message has been tampered with or compromised. Digital signing alone will not encrypt or hide the contents of the message, but it will ensure that a tampered message will be automatically rejected by the receiving Web service. Encrypting the message headers will clearly protect its contents, but this approach works best if the message is not being routed or referred to another Web service endpoint. Intermediary Web services will need access to the addressing header information, so there is an additional burden on the developer to ensure that the intermediaries can encrypt the message header contents. This leads to key management issues and also performance issues if each endpoint is required to decrypt and encrypt message headers. The message ID (<wsa:MessageID>) is important because it allows you to design against replay attacks, whereby a client repeatedly resends the same message to a Web service endpoint in order to overwhelm the service and to bring down its host server. The receiving Web service simply needs to cache this message ID and then ignore additional requests that come in. Refer to 7 for a detailed discussion on replay attacks and how to prevent them. There is no right way to implement security to protect addressing headers. Each of these options are recommended rather than required. You need to make an individual determination as to whether security measures are required for your service-oriented application.

Figure 5-8. Both conditions with the new condition in the Condition Preview area As you can see, the Select Condition dialog shows you all conditions defined for this workflow, not only for the activity you re currently working on. Click OK in the Select Condition dialog box.

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