An open source proxy server used for libraries to use so they can give access to the paid restricted-access databases and other websites available only to certa

An open source proxy server used for libraries to use so they can give access to the paid restricted-access databases and other websites available only to certain patrons. Most types of libraries (especially college and public) have resources they pay for and require users to authenticate in order to access. There's currently not a nice easy to use FOSS solution for this.