There is no support for smart card redirection in Web Access. We're not sure about the feasibility of this feature with the current set of web standards.
There is apparently a draft web standard for what is seemingly a full PC/SC API that is current being implemented in Chrome: https://chromestatus.com/feature/6411735804674048 From the looks of things, universal web browser support for this is likely years away.
There is also the Webauthn API which more or less has universal support among the major browsers: https://developer.mozilla.org/en-US/docs/Web/API/Web_Authentication_API Webauthn *can* interface with smart cards. The problem is that it is fairly limited in scope. Assuming that the abstraction level of Webauthn is low enough, it may be possible to emulate PC/SC on the server side through Webauthn on the client side. My knowledge of smart cards is a bit too limited to draw any conclusions about this just yet.
