More accurate version checking using Rtl variant

Author: Julia-Garland

src/libmongoc/src/mongoc/mongoc-version-functions.c

@@ -84,6 +84,9 @@ mongoc_check_version(int required_major, int required_minor, int required_micro)
 }
 
 #ifdef _WIN32
+
+typedef NTSTATUS (APIENTRY *RTLVERIFYVERSIONINFO_FN) (PRTL_OSVERSIONINFOEXW VersionInfo, ULONG TypeMask, ULONGLONG ConditionMask);
+
 /**
  * _mongoc_verify_windows_version:
  *
@@ -93,37 +96,56 @@ mongoc_check_version(int required_major, int required_minor, int required_micro)
 bool
 _mongoc_verify_windows_version(int major_version, int minor_version, int build_number, bool strictly_equal)
 {
-   OSVERSIONINFOEX osvi;
+   static RTLVERIFYVERSIONINFO_FN pRtlVerifyVersionInfo;
+   OSVERSIONINFOEXW osvi;
    bool matched;
    int op = VER_GREATER_EQUAL;
 
    if (strictly_equal) {
       op = VER_EQUAL;
    }
 
-   ZeroMemory(&osvi, sizeof(OSVERSIONINFOEX));
-   osvi.dwOSVersionInfoSize = sizeof(OSVERSIONINFOEX);
+   /* Windows version functions may not return the correct version for
+   later Windows versions unless the application is so manifested. Try  
+   to use the more accurate kernel function RtlVerifyVersionInfo */
+   HMODULE hDll = LoadLibrary(TEXT("Ntdll.dll"));
+   if (hDll) {
+      pRtlVerifyVersionInfo = (RTLVERIFYVERSIONINFO_FN)GetProcAddress(hDll, "RtlVerifyVersionInfo");
+   }
+
+   ZeroMemory(&osvi, sizeof(OSVERSIONINFOEXW));
+   osvi.dwOSVersionInfoSize = sizeof(OSVERSIONINFOEXW);
    osvi.dwMajorVersion = major_version;
    osvi.dwMinorVersion = minor_version;
 
    ULONGLONG mask = 0;
    VER_SET_CONDITION(mask, VER_MAJORVERSION, op);
    VER_SET_CONDITION(mask, VER_MINORVERSION, op);
 
-   matched = VerifyVersionInfo(&osvi, VER_MAJORVERSION | VER_MINORVERSION, mask);
+   if (pRtlVerifyVersionInfo) {
+      matched = (pRtlVerifyVersionInfo(&osvi, VER_MAJORVERSION | VER_MINORVERSION, mask) == 0);
+   } else {
+      matched = (VerifyVersionInfoW(&osvi, VER_MAJORVERSION | VER_MINORVERSION, mask) != 0);
+   } 
 
    // Compare build number separately if major and minor versions are equal
    if (build_number && matched && _mongoc_verify_windows_version(major_version, minor_version, 0, true)) {
-      ZeroMemory(&osvi, sizeof(OSVERSIONINFOEX));
-      osvi.dwOSVersionInfoSize = sizeof(OSVERSIONINFOEX);
+      ZeroMemory(&osvi, sizeof(OSVERSIONINFOEXW));
+      osvi.dwOSVersionInfoSize = sizeof(OSVERSIONINFOEXW);
       osvi.dwBuildNumber = build_number;
 
       mask = 0;
       VER_SET_CONDITION(mask, VER_BUILDNUMBER, op);
 
-      matched = VerifyVersionInfo(&osvi, VER_BUILDNUMBER, mask);
+      if (pRtlVerifyVersionInfo) {
+         matched = (pRtlVerifyVersionInfo(&osvi, VER_BUILDNUMBER, mask) == 0);
+      } 
+      else {
+         matched = (VerifyVersionInfoW(&osvi, VER_BUILDNUMBER, mask) != 0);
+      }
    }
 
    return matched;
 }
+
 #endif