The SAMLTokenProvider has a "SubjectProvider subjectProvider" property, which can be used to configure the Subject of the generated token, regardless of the version of the token. The SubjectProvider interface defines a single method to return a SubjectBean, given the token provider parameters, the parent Document of the assertion, and a secret key to use (if any). The SubjectBean contains the Subject name, name-qualifier, confirmation method, and KeyInfo element, amongst other properties. The SAMLTokenProvider ships with a default SubjectProvider implementation that is used to insert a Subject into every SAML Token that is generated.
The DefaultSubjectProvider has a single configuration method to set the subject name qualifier. It creates a subject confirmation method by checking the received key type. The subject name is the name of the principal obtained from TokenProviderParameters. Finally, a KeyInfo element is set on the SubjectBean under the following conditions:
If a "SymmetricKey" Key Type algorithm is specified by the client, then the secret key passed through to the SubjectProvider is encrypted with the X509Certificate of the recipient, and added to the KeyInfo element. How the provider knows the public key of the recipient will be covered subsequently.
If a "PublicKey" KeyType algorithm is specified by the client, the X509Certificate that is received as part of the "UseKey" request is inserted into the KeyInfo element of the Subject.
If a "Bearer" KeyType algorithm is specified by the client, then no KeyInfo element is added to the Subject. For the "SymmetricKey" Key Type case, the SAMLTokenProvider creates a secret key using a SymmetricKeyHandler instance. The SymmetricKeyHandler first checks the key size that is supplied as part of the KeyRequirements object, by checking that it fits in between a minimum and maximum key size that can be configured. It also checks any client entropy that is supplied, as well as the computed key algorithm. It then creates some entropy and a secret key.
To add a custom Subject element to an assertion, you must create your own SubjectProvider implementation, and set it on the SAMLTokenProvider.