use win32 crypt api for password generation on windows

creates a new function rand in the util class that calls bcryptgenrandom
from the win32 api when running on windows and falls back to qrand on
other platforms

src/pass.cpp

@@ -91,7 +91,7 @@ QString Pass::Generate_b(int length, const QString &charset) {
   } else {
     if (charset.length() > 0) {
       for (int i = 0; i < length; ++i) {
-        int index = qrand() % charset.length();
+        int index = Util::rand() % charset.length();
         QChar nextChar = charset.at(index);
         passwd.append(nextChar);
       }

src/src.pro

@@ -164,7 +164,7 @@ win32 {
     }
     gcc:QMAKE_LFLAGS += -Wl,--dynamicbase -Wl,--nxcompat
     msvc:QMAKE_LFLAGS += /DYNAMICBASE /NXCOMPAT
-    LIBS    += -lmpr
+    LIBS    += -lmpr -lbcrypt
 } else:macx {
     ICON = ../artwork/icon.icns
     QMAKE_INFO_PLIST = ../qtpass.plist

src/util.cpp

@@ -6,6 +6,7 @@
 #include <QString>
 #ifdef Q_OS_WIN
 #include <windows.h>
+#include <bcrypt.h>
 #else
 #include <sys/time.h>
 #endif
@@ -176,3 +177,13 @@ void Util::copyDir(const QString src, const QString dest) {
                 dest + QDir::separator() + file);
   }
 }
+
+int Util::rand() {
+#ifdef Q_OS_WIN
+  quint32 ret;
+  BCryptGenRandom(NULL, (PUCHAR)&ret, sizeof(ret), BCRYPT_USE_SYSTEM_PREFERRED_RNG);
+  return ret%RAND_MAX;
+#else
+  return qrand();
+#endif
+}

src/util.h

@@ -21,7 +21,8 @@ class Util {
   static QString getDir(const QModelIndex &index, bool forPass,
                         const QFileSystemModel &model,
                         const StoreModel &storeModel);
-  static void copyDir(const QString src, const QString dest);
+  static void copyDir(const QString src, const QString dest);\
+  static int rand();
 
 private:
   static void initialiseEnvironment();

tests/auto/util/util.pro

@@ -21,3 +21,7 @@ HEADERS   += util.h \
 
 VPATH += ../../../src
 INCLUDEPATH += ../../../src
+
+win32 {
+    LIBS += -lbcrypt
+}