Configuring encryption to protect message confidentiality using the WSS APIs

You can configure encryption information for the client-side request generator (sender) bindings. Encryption information is used to specify how the generators (senders) encrypt outgoing SOAP messages. To configure encryption, specify which message parts to encrypt and specify which algorithm methods and security tokens are to be used for encryption.

Before you begin

Confidentiality refers to encryption while integrity refers to digital signing. Confidentiality reduces the risk of someone understanding the message flowing across the Internet. With confidentiality specifications, the message is encrypted before it is sent and decrypted when it is received at the correct target. Prior to configuring encryption, familiarize yourself with XML encryption.

About this task

For encryption, you must specify the following:

Which parts of the message are to be encrypted.
Which encryption algorithms to specify.

To configure encryption and encrypted parts on the client side, use the WSSEncryption and WSSEncryptPart APIs, or configure policy sets using the administrative console.

WebSphere® Application Server provides default values for bindings. However, an administrator must modify the defaults for a production environment.

WebSphere Application Server uses encryption information for the default generator to encrypt parts of the SOAP message. The WSSEncryption API configures the following required parts as encrypted parts.

Table 1. Required encrypted parts. Use encrypted parts to increase the confidentiality of SOAP messages.
Encryption parts	Description
Keywords	Keywords are used to add the encrypted parts to the SOAP message.
XPath expression	An XPath expression is used to add the encrypted parts to the SOAP message.
WSSEncryptPart object	This object adds the encrypted parts to the SOAP message.
WSSSignature object	This object adds the signature component as an encrypted part.
Header	This part adds the header in the SOAP header, specified by QName, as an encryption part.
Security token object	This object adds the security token as an encryption part.

Web Services Security API (WSS API) supports symmetric encryption, by using a shared key, only when Web Services Secure Conversation (WS-SecureConversation) is used.

The WSS APIs allow the use of either keywords or an XPath expression to specify the parts of the message that are to be encrypted. WebSphere Application Server supports the use of the following keywords:

Table 2. Supported encryption keywords. Use keywords to specify encrypted parts.
Keyword	References
BODY_CONTENT	The keyword for the contents of the SOAP message body as an encryption target.
SIGNATURE	The keyword for the signature component as an encryption target.

If configuring using the WSS APIs, the WSSEncryption and WSSEncryptPart APIs complete these high-level steps:

Procedure

Use the WSSEncryption API to configure encryption.
The WSSEncryption API performs these tasks by default:
1. Generates the callback handler.
2. Generates the generator security token object.
3. Adds the security token reference type.
4. Adds the signature component.
5. Adds the WSSEncryptPart object.
6. Adds the parts to be encrypted.
  Adds the default parts as targets of encryption by using keywords and XPath expressions.
7. Adds the header in the SOAP message, specified by QName.
8. Sets the default data encryption method.
9. Specifies whether the key is to be encrypted using a Boolean value.
10. Sets the default key encryption method.
11. Selects a part reference.
12. Sets the MTOM optimization Boolean value.
Use the WSSEncryptPart API to configure encrypted parts or add a transform method. The WSSEncryptPart API performs these tasks by default:
1. Sets the encrypted parts specified by using keywords or an XPath expression.
2. Sets the encrypted parts specified by an XPath expression.
3. Sets the signature component object, WSSSignature.
4. Sets the header in the SOAP message, specified by QName.
5. Sets the generator security token.
6. Adds the transform method, if needed.
Change from the default values for algorithm or message parts, as needed.
For example: you could change one or more of the following items:
- Change the data encryption algorithm from the default value of AES 128.
- Change the key encryption algorithm from the default value of KW_RSA_OAEP.
- Specify to not encrypt the key (false).
- Change the security token type from default of X.509 token.
- Change the security token reference type from the default value of SecurityToken.REF_STR.
- Only use BODY_CONTENT as an encryption part and not use SIGNATURE also.
- Turn MTOM optimization on (true).

Results

The encryption information is configured for the generator binding.

Example

The following is an example of the WSSEncryption API:

    WSSFactory factory = WSSFactory.getInstance();
    WSSGenerationContext gencont = factory.newWSSGenerationContext();
   
    X509GenerateCallbackHandler callbackhandler = generateCallbackHandler();
    SecurityToken token = factory.newSecurityToken(X509Token.class, callbackHandler);
    WSSEncryption enc = factory.newWSSEncryption(token);
    
    gencont.add(enc);

What to do next

You must configure similar decryption information for the client-side response consumer (receiver) bindings, if you have not already configured the information.

Next, review the WSSEncryption API process.