From 70816f90b2c4488c9636ca60124eb897c7da6371 Mon Sep 17 00:00:00 2001
From: Janek Bevendorff <janek@jbev.net>
Date: Fri, 24 Feb 2017 00:15:57 +0100
Subject: [PATCH] Make challenge() member thread-safe

---
 src/keys/drivers/YubiKey.cpp | 27 ++++++++++++++++-----------
 src/keys/drivers/YubiKey.h   | 12 ++++++++++--
 2 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/src/keys/drivers/YubiKey.cpp b/src/keys/drivers/YubiKey.cpp
index b287c13b2..1d4445cd6 100644
--- a/src/keys/drivers/YubiKey.cpp
+++ b/src/keys/drivers/YubiKey.cpp
@@ -107,8 +107,10 @@ void YubiKey::detect()
             QByteArray resp;
 
             result = challenge(i, false, rand, resp);
-
-            if (result != YubiKey::ERROR) {
+            if (result == YubiKey::ALREADY_RUNNING) {
+                emit alreadyRunning();
+                return;
+            } else if (result != YubiKey::ERROR) {
                 emit detected(i, result == YubiKey::WOULDBLOCK ? true : false);
                 return;
             }
@@ -141,13 +143,18 @@ static inline QString printByteArray(const QByteArray& a)
 }
 #endif
 
-YubiKey::ChallengeResult YubiKey::challenge(int slot, bool mayBlock, const QByteArray& chal, QByteArray& resp) const
+YubiKey::ChallengeResult YubiKey::challenge(int slot, bool mayBlock, const QByteArray& chal, QByteArray& resp)
 {
+    if (!m_mutex.tryLock()) {
+        return ALREADY_RUNNING;
+    }
+
     int yk_cmd = (slot == 1) ? SLOT_CHAL_HMAC1 : SLOT_CHAL_HMAC2;
     QByteArray paddedChal = chal;
 
-    /* Ensure that YubiKey::init() succeeded */
+    // ensure that YubiKey::init() succeeded
     if (m_yk == NULL) {
+        m_mutex.unlock();
         return ERROR;
     }
 
@@ -171,13 +178,12 @@ YubiKey::ChallengeResult YubiKey::challenge(int slot, bool mayBlock, const QByte
     r = reinterpret_cast<unsigned char*>(resp.data());
 
 #ifdef QT_DEBUG
-    qDebug().nospace() << __func__ << "(" << slot << ") c = "
-                       << printByteArray(paddedChal);
+    qDebug().nospace() << __func__ << "(" << slot << ") c = " << printByteArray(paddedChal);
 #endif
 
-    int ret = yk_challenge_response(m_yk, yk_cmd, mayBlock,
-                                    paddedChal.size(), c,
-                                    resp.size(), r);
+    int ret = yk_challenge_response(m_yk, yk_cmd, mayBlock, paddedChal.size(), c, resp.size(), r);
+
+    m_mutex.unlock();
 
     if (!ret) {
         if (yk_errno == YK_EWOULDBLOCK) {
@@ -206,8 +212,7 @@ YubiKey::ChallengeResult YubiKey::challenge(int slot, bool mayBlock, const QByte
     resp.resize(20);
 
 #ifdef QT_DEBUG
-    qDebug().nospace() << __func__ << "(" << slot << ") r = "
-                       << printByteArray(resp) << ", ret = " << ret;
+    qDebug().nospace() << __func__ << "(" << slot << ") r = " << printByteArray(resp) << ", ret = " << ret;
 #endif
 
     return SUCCESS;
diff --git a/src/keys/drivers/YubiKey.h b/src/keys/drivers/YubiKey.h
index acf4feb72..6c3504ed1 100644
--- a/src/keys/drivers/YubiKey.h
+++ b/src/keys/drivers/YubiKey.h
@@ -19,6 +19,7 @@
 #define KEEPASSX_YUBIKEY_H
 
 #include <QObject>
+#include <QMutex>
 
 /**
  * Singleton class to manage the interface to the hardware
@@ -28,7 +29,7 @@ class YubiKey : public QObject
     Q_OBJECT
 
 public:
-    enum ChallengeResult { ERROR = -1, SUCCESS = 0, WOULDBLOCK };
+    enum ChallengeResult { ERROR = -1, SUCCESS = 0, WOULDBLOCK, ALREADY_RUNNING };
 
     /**
      * @brief YubiKey::instance - get instance of singleton
@@ -64,7 +65,7 @@ public:
      */
     ChallengeResult challenge(int slot, bool mayBlock,
                               const QByteArray& chal,
-                              QByteArray& resp) const;
+                              QByteArray& resp);
 
     /**
      * @brief YubiKey::getSerial - serial number of YubiKey
@@ -92,6 +93,11 @@ Q_SIGNALS:
      */
     void notFound();
 
+    /**
+     * Emitted when detection is already running.
+     */
+    void alreadyRunning();
+
 private:
     explicit YubiKey();
     static YubiKey* m_instance;
@@ -100,6 +106,8 @@ private:
     void* m_yk_void;
     void* m_ykds_void;
 
+    QMutex m_mutex;
+
     Q_DISABLE_COPY(YubiKey)
 };