Providing access to a smartcard within a remote session

1. A method, implemented on a server in a virtual desktop infrastructure environment, for enabling smart card access from within a remote session, the method comprising:

establishing a remote session between a client and the server, including redirecting a smart card that is connected to the client to the server so that the smart card is accessible on the server;

intercepting, by a smart card stub that executes within the remote session on the server, an application programming interface (API) for accessing the redirected smart card that was made by an application executing within the remote session;

passing, by the smart card stub that executes within the remote session, the intercepted API call to a smart card proxy that is executing on the server within session 0; and

executing, by the smart card proxy that executes within session 0, the API call to access the redirected smart card.

2. The method of claim 1 , wherein the smart card stub passes the intercepted API call to the smart card proxy using a remote procedure call.

3. The method of claim 1 , wherein the API call is executed via a smart card resource manager service that is executing on the server.

4. The method of claim 3 , wherein the API call is executed via a smart card driver stack that is loaded on the server.

5. The method of claim 1 , wherein the smart card stub employs a remote procedure call to pass the intercepted API call to the smart card proxy.

6. The method of claim 1 , wherein the smart card stub hooks API calls of the WinSCard API.

7. The method of claim 1 , further comprising:

receiving, by the smart card proxy, a response from the execution of the API call; and

passing the response to the smart card stub.

8. The method of claim 7 , wherein the smart card proxy passes the response to the smart card stub as a response to a remote procedure call that the smart call stub invoked to pass the intercepted API call to the smart card proxy.

9. The method of claim 8 , further comprising:

returning, by the smart card stub, the response to the application.

10. The method of claim 1 , wherein the intercepted API call includes an Answer-To-Reset (ATR) string, and the smart card stub passes the ATR string to the smart card proxy in a buffer having a size that is equal to the maximum size of an ATR string even when the ATR string has a size that is less than the maximum size.

11. The method of claim 10 , wherein the smart card stub copies the ATR string into the buffer using the memcpy function that specifies the maximum size as the number of bytes to copy.

12. The method of claim 10 , wherein the smart card stub passes the ATR string as part of a remote procedure call, including specifying the maximum size as the length of the ATR string.

13. The method of claim 1 , further comprising:

establishing a nested session with another server from within the remote session, including loading an instance of the smart card stub in the nested session;

intercepting, by the smart card stub in the nested session, a second API call to access the smart card that is made by an application executing on the other server within the nested session;

passing, by the smart card stub in the nested session, the second intercepted API call to the smart card proxy executing on the server; and

executing, by the smart card proxy, the second API call.

14. The method of claim 13 , wherein the smart card stub in the nested session passes the second intercepted API call to the smart card proxy via a remote procedure call.

15. The method of claim 14 , further comprising:

receiving, by the smart card proxy, a response to the second API call; and

passing the response to the second API call to the smart card stub in the nested session.

16. The method of claim 13 , wherein establishing the nested sessions comprises specifying, to the smart card stub in the nested session, information for communicating with the smart card proxy.

17. One or more computer storage media having computer executable instructions which when executed by one or more processors of a server in a virtual desktop infrastructure environment implement a method for enabling smart card access from within a remote session, the method comprising:

as part of establishing a remote session for a client that has remotely connected to the server, loading a smart card stub in the remote session and a smart card proxy in session 0, loading the smart card stub including hooking operating-system-provided application programming interface (API) calls for accessing smart cards;

intercepting, by the smart card stub, an API call for accessing the redirected smart card that was made by an application executing with the remote session;

passing, by the smart card stub, the API call to the smart card proxy using a remote procedure call; and

executing, by the smart card proxy, the API call to access the redirected smart card.

18. The computer storage media of claim 17 , wherein the API call includes an Answer to Reset (ATR) string, and wherein the smart card stub passes the ATR string in a buffer having a size equal to a maximum allowable size for an ATR string.

19. One or more computer storage media having computer executable instructions which when executed by one or more processors of a server implement a virtual desktop infrastructure environment comprising:

an agent that executes on the server and is configured to establish remote sessions with clients;

a virtual USB bus driver that interfaces with the agent to redirect smart cards from the clients to the server;

a smart card stub that is loaded in each remote session and is configured to intercept application programming interface (API) calls to access the redirected smart cards; and

a smart card proxy that is loaded in session 0 and is configured to receive the intercepted API calls from the smart card stub and to invoke the API calls.

20. The computer storage media of claim 19 , wherein the smart card proxy receives the API calls via remote procedure calls.