* Support NFC readers for hardware tokens using PC/SC
This requires a new library dependency: PCSC.
The PCSC library provides methods to access smartcards. On Linux, the third-party pcsc-lite package is used. On Windows, the native Windows API (Winscard.dll) is used. On Mac OSX, the native OSX API (framework-PCSC) is used.
* Split hardware key access into multiple classes to handle different methods of communicating with the keys.
* Since the Yubikey can now be a wireless token as well, the verb "plug in" was replaced with a more
generic "interface with". This shall indicate that the user has to present their token to the reader, or plug it in via USB.
* Add PC/SC interface for YubiKey challenge-response
This new interface uses the PC/SC protocol and API
instead of the USB protocol via ykpers. Many YubiKeys expose their functionality as a CCID device, which can be interfaced with using PC/SC. This is especially useful for NFC-only or NFC-capable Yubikeys, when they are used together with a PC/SC compliant NFC reader device.
Although many (not all) Yubikeys expose their CCID functionality over their own USB connection as well, the HMAC-SHA1 functionality is often locked in this mode, as it requires eg. a touch on the gold button. When accessing the CCID functionality wirelessly via NFC (like this code can do using a reader), then the user interaction is to present the key to the reader.
This implementation has been tested on Linux using pcsc-lite, Windows using the native Winscard.dll library, and Mac OSX using the native PCSC-framework library.
* Remove PC/SC ATR whitelist, instead scan for AIDs
Before, a whitelist of ATR codes (answer to reset, hardware-specific)
was used to scan for compatible (Yubi)Keys.
Now, every connected smartcard is scanned for AIDs (applet identifier),
which are known to implement the HMAC-SHA1 protocol.
This enables the support of currently unknown or unreleased hardware.
Co-authored-by: Jonathan White <support@dmapps.us>
