Support Referrals for security realms using LDAP for authentication or group loading.

I see the following scenarios to cover for this: -

• Authentication - A search is performed e.g against 'uid' and a referral is encountered, the URL needs to be extracted from the referral and a new connection created using the referral URL to load any additional attributes for the user, the referral URL is then used to establish the connection as the user to verify that their password is correct.

Group loading then has a couple of issues, firstly where the user was a referral.

The search for group membership information is a fresh start but now we potentially have 2 simple named and 2 distinguished names that could be referenced from the group object. We may want a config option to specify which one to actually use and even possibly use both.

Next could a group also be a referral, i.e. it contains the reference to the user as an attribute so was matched in the search but is also a referral to the true named group in another location. In this situation I suggest any iterative search takes into account the context containing the actual group definition and continues the search from there.

And then where the principal contains an attribute that references, this one should be a simple following of a referral and once followed continue the attribute loading using the new connection.

The connection manager logic is going to need reworking, ideally for a referral we should check if we have a connection definition that matches based on the URL returned otherwise we will need to try and establish a connection based on the settings of the last connection used, this probably also introduces a notion of some form of connection stack of the connections used for the current request - referrals could have us bouncing back and forth so connections should be cached and re-used where possible during authentication and group loading.

• Connection Settings *

We are going to need to support two different modes in relation to the 'java.naming.referral' property, follow and throw.

• follow - In this mode when the InitialDirContext encounters a referral during a search it will automatically follow it, this means automatically connecting to the server in the URL. This is fine if the remaining connection settings are valid for the alternative server e.g. same bindDN and credential. We however need to take the following into account for subsequent operations such as password validation or further queries.

• throw - When a referral is encountered and exception will be thrown instead, this mode should make it easier to have some more advanced referral handling logic that allows us control of which connection we subsequently use, e.g. we could not use a completely different host name to the one in the referral or use a different bind DN / credential pair.