1. A method for authenticating users in a secure search system for searching a plurality of secure data sources, the method comprising: receiving, using one or more processors, user identification information from a user in a secure enterprise system (SES); providing, using the one or more processors, the user identification information to a plurality of identity management systems in the SES, wherein each of the plurality of identity management systems receives the user identification information through a respective Application Program Interface (API); validating, using the one or more processors, the user against at least one identity management system in the plurality of identity management systems; crawling, using the one or more processors, at least one secure data source in the plurality of secure data sources residing on a plurality of different computer systems that is associated with the at least one identity management system; building, using the one or more processors, an index of documents from the at least one secure data source based on the crawling; receiving, using the one or more processors, a query from the user; calling back, using the one or more processors, at query time into the at least one identity management system to obtain security attribute values for the user; appending, using the one or more processors, the security attribute values for the user to the query and using the appended query to query the index of documents; and determining, using the one or more processors, one or more documents from the index of documents in the plurality of secure data sources, that are responsive to the query and accessible to the user based on the security attribute values for the user and respective security attributes of the one or more documents.
2. The method according to claim 1 , wherein a number or type of objects required from the user identification information by a first identity management system in the plurality of identity management systems is different from a number or type of objects required from the user identification information by a second identity management system in the plurality of identity management systems.