7.3. Providing Client Credentials
Overview
There are essentially two approaches to providing
UsernameToken client credentials: you can either set both the username and the password directly in the client's Spring XML configuration; or you can set the username in the client's configuration and implement a callback handler to provide passwords programmatically. The latter approach (by programming) has the advantage that passwords are easier to hide from view.
Client credentials properties
Table 7.1, “Client Credentials Properties” shows the properties you can use to specify WS-Security username/password credentials on a client's request context in Spring XML.
| Properties | Description |
|---|---|
security.username | Specifies the username for UsernameToken policy assertions. |
security.password | Specifies the password for UsernameToken policy assertions. If not specified, the password is obtained by calling the callback handler. |
security.callback-handler |
Specifies the class name of the WSS4J callback handler that retrieves passwords for UsernameToken policy assertions. Note that the callback handler can also handle other kinds of security events.
|
Configuring client credentials in Spring XML
To configure username/password credentials in a client's request context in Spring XML, set the
security.username and security.password properties as follows:
<beans ... >
<jaxws:client name="{NamespaceName}LocalPortName"
createdFromAPI="true">
<jaxws:properties>
<entry key="security.username" value="Alice"/>
<entry key="security.password" value="abcd!1234"/>
</jaxws:properties>
</jaxws:client>
...
</beans>
If you prefer not to store the password directly in Spring XML (which might potentially be a security hazard), you can provide passwords using a callback handler instead.
Programming a callback handler for passwords
If you want to use a callback handler to provide passwords for the UsernameToken header, you must first modify the client configuration in Spring XML, replacing the
security.password setting by a security.callback-handler setting, as follows:
<beans ... >
<jaxws:client name="{NamespaceName}LocalPortName"
createdFromAPI="true">
<jaxws:properties>
<entry key="security.username" value="Alice"/>
<entry key="security.callback-handler" value="interop.client.UTPasswordCallback"/>
</jaxws:properties>
</jaxws:client>
...
</beans>
In the preceding example, the callback handler is implemented by the
UTPasswordCallback class. You can write a callback handler by implementing the javax.security.auth.callback.CallbackHandler interface, as shown in Example 7.2, “Callback Handler for UsernameToken Passwords”.
Example 7.2. Callback Handler for UsernameToken Passwords
package interop.client; import java.io.IOException; import java.util.HashMap; import java.util.Map; import javax.security.auth.callback.Callback; import javax.security.auth.callback.CallbackHandler; import javax.security.auth.callback.UnsupportedCallbackException; import org.apache.ws.security.WSPasswordCallback; public class UTPasswordCallback implements CallbackHandler { private Map<String, String> passwords = new HashMap<String, String>(); public UTPasswordCallback() { passwords.put("Alice", "ecilA"); passwords.put("Frank", "invalid-password"); //for MS clients passwords.put("abcd", "dcba"); } public void handle(Callback[] callbacks) throws IOException, UnsupportedCallbackException { for (int i = 0; i < callbacks.length; i++) { WSPasswordCallback pc = (WSPasswordCallback)callbacks[i]; String pass = passwords.get(pc.getIdentifier()); if (pass != null) { pc.setPassword(pass); return; } } throw new IOException(); } // Add an alias/password pair to the callback mechanism. public void setAliasPassword(String alias, String password) { passwords.put(alias, password); } }
The callback functionality is implemented by the
CallbackHandler.handle() method. In this example, it assumed that the callback objects passed to the handle() method are all of org.apache.ws.security.WSPasswordCallback type (in a more realistic example, you would check the type of the callback objects).
A more realistic implementation of a client callback handler would probably consist of prompting the user to enter their password.
WSPasswordCallback class
When a
CallbackHandler is called in a Apache CXF client for the purpose of setting a UsernameToken password, the corresponding WSPasswordCallback object has the USERNAME_TOKEN usage code.
For more details about the
WSPasswordCallback class, see org.apache.ws.security.WSPasswordCallback.
The
WSPasswordCallback class defines several different usage codes, as follows:
- USERNAME_TOKEN
- Obtain the password for UsernameToken credentials. This usage code is used both on the client side (to obtain a password to send to the server) and on the server side (to obtain a password in order to compare it with the password received from the client).On the server side, this code is set in the following cases:
- Digest password—if the UsernameToken contains a digest password, the callback must return the corresponding password for the given user name (given by
WSPasswordCallback.getIdentifier()). Verification of the password (by comparing with the digest password) is done by the WSS4J runtime. - Plaintext password—implemented the same way as the digest password case (since Apache CXF 2.4.0).
- Custom password type—if
getHandleCustomPasswordTypes()istrueonorg.apache.ws.security.WSSConfig, this case is implemented the same way as the digest password case (since Apache CXF 2.4.0). Otherwise, an exception is thrown.
If noPasswordelement is included in a received UsernameToken on the server side, the callback handler is not called (since Apache CXF 2.4.0). - DECRYPT
- Need a password to retrieve a private key from a Java keystore, where
WSPasswordCallback.getIdentifier()gives the alias of the keystore entry. WSS4J uses this private key to decrypt the session (symmetric) key. - SIGNATURE
- Need a password to retrieve a private key from a Java keystore, where
WSPasswordCallback.getIdentifier()gives the alias of the keystore entry. WSS4J uses this private key to produce a signature. - SECRET_KEY
- Need a secret key for encryption or signature on the outbound side, or for decryption or verification on the inbound side. The callback handler must set the key using the
setKey(byte[])method. - SECURITY_CONTEXT_TOKEN
- Need the key for a
wsc:SecurityContextToken, which you provide by calling thesetKey(byte[])method. - CUSTOM_TOKEN
- Need a token as a DOM element. For example, this is used for the case of a reference to a SAML Assertion or SecurityContextToken that is not in the message. The callback handler must set the token using the
setCustomToken(Element)method. - KEY_NAME
- (Obsolete) Since Apache CXF 2.4.0, this usage code is obsolete.
- USERNAME_TOKEN_UNKNOWN
- (Obsolete) Since Apache CXF 2.4.0, this usage code is obsolete.
- UNKNOWN
- Not used by WSS4J.
