YubiKey: Retry to recover hotplugging

* Attempt one retry in the event the event the device was removed and
  re-inserted.

Signed-off-by: Kyle Manna <kyle@kylemanna.com>

src/keys/YkChallengeResponseKey.cpp

@@ -26,6 +26,8 @@
 #include "keys/YkChallengeResponseKey.h"
 #include "keys/drivers/YubiKey.h"
 
+#include <QDebug>
+
 YkChallengeResponseKey::YkChallengeResponseKey(int slot,
                                                bool blocking)
     : m_slot(slot),
@@ -46,11 +48,31 @@ YkChallengeResponseKey* YkChallengeResponseKey::clone() const
 
 /** Assumes yubikey()->init() was called */
 bool YkChallengeResponseKey::challenge(const QByteArray& chal)
+{
+    return challenge(chal, 1);
+}
+
+bool YkChallengeResponseKey::challenge(const QByteArray& chal, int retries)
 {
     if (YubiKey::instance()->challenge(m_slot, true, chal, m_key) != YubiKey::ERROR) {
         return true;
     }
 
+    /* If challenge failed, retry to detect YubiKeys int the event the YubiKey
+     *  was un-plugged and re-plugged */
+    while (retries > 0) {
+        qDebug() << "Attempt" << retries << "to re-detect YubiKey(s)";
+        retries--;
+
+        if (YubiKey::instance()->init() != true) {
+            continue;
+        }
+
+        if (YubiKey::instance()->challenge(m_slot, true, chal, m_key) != YubiKey::ERROR) {
+            return true;
+        }
+    }
+
     return false;
 }
 

src/keys/YkChallengeResponseKey.h

@@ -31,7 +31,8 @@ public:
 
     QByteArray rawKey() const;
     YkChallengeResponseKey* clone() const;
-    bool challenge(const QByteArray& challenge);
+    bool challenge(const QByteArray& chal);
+    bool challenge(const QByteArray& chal, int retries);
     QString getName() const;
     bool isBlocking() const;
 

src/keys/drivers/YubiKey.cpp

@@ -182,6 +182,11 @@ YubiKey::ChallengeResult YubiKey::challenge(int slot, bool mayBlock,
     int yk_cmd = (slot == 1) ? SLOT_CHAL_HMAC1 : SLOT_CHAL_HMAC2;
     QByteArray paddedChal = chal;
 
+    /* Ensure that YubiKey::init() succeeded */
+    if (m_yk == NULL) {
+        return ERROR;
+    }
+
     /* yk_challenge_response() insists on 64 byte response buffer */
     resp.resize(64);