[host] windows: re-implement open log safely

Instead of doing ShellExecute from the service, we instead get the token
of the currently logged in user, and do CreateProcessAsUserA to run
notepad with that token. This should be safe.

host/platform/Windows/src/service.c

@@ -44,24 +44,6 @@ Place, Suite 330, Boston, MA 02111-1307 USA
 #define FAIL_MAX_RETRIES         5
 #define FAIL_RETRY_INIT_INTERVAL 1000
 
-/*
- * Windows 10 provides this API via kernel32.dll as well as advapi32.dll and
- * mingw opts for linking against the kernel32.dll version which is fine
- * provided you don't intend to run this on earlier versions of windows. As such
- * we need to lookup this method at runtime. */
-typedef WINBOOL WINAPI (*CreateProcessAsUserA_t)(HANDLE hToken,
-    LPCSTR lpApplicationName,
-    LPSTR lpCommandLine,
-    LPSECURITY_ATTRIBUTES lpProcessAttributes,
-    LPSECURITY_ATTRIBUTES lpThreadAttributes,
-    WINBOOL bInheritHandles,
-    DWORD dwCreationFlags,
-    LPVOID lpEnvironment,
-    LPCSTR lpCurrentDirectory,
-    LPSTARTUPINFOA lpStartupInfo,
-    LPPROCESS_INFORMATION lpProcessInformation);
-static CreateProcessAsUserA_t f_CreateProcessAsUserA = NULL;
-
 struct Service
 {
   FILE * logFile;
@@ -90,32 +72,6 @@ void doLogReal(const char * fmt, ...)
 
 #define doLog(fmt, ...) doLogReal("[%s] " fmt, currentTime(), ##__VA_ARGS__)
 
-static bool setupAPI(void)
-{
-  /* first look in kernel32.dll */
-  HMODULE mod;
-
-  mod = GetModuleHandleA("kernel32.dll");
-  if (mod)
-  {
-    f_CreateProcessAsUserA = (CreateProcessAsUserA_t)
-      GetProcAddress(mod, "CreateProcessAsUserA");
-    if (f_CreateProcessAsUserA)
-      return true;
-  }
-
-  mod = GetModuleHandleA("advapi32.dll");
-  if (mod)
-  {
-    f_CreateProcessAsUserA = (CreateProcessAsUserA_t)
-      GetProcAddress(mod, "CreateProcessAsUserA");
-    if (f_CreateProcessAsUserA)
-      return true;
-  }
-
-  return false;
-}
-
 static void setupLogging(void)
 {
   char logFilePath[MAX_PATH];
@@ -260,9 +216,9 @@ void Launch(void)
     service.process = NULL;
   }
 
-  if (!setupAPI())
+  if (!windowsSetupAPI())
   {
-    doLog("setupAPI failed\n");
+    doLog("windowsSetupAPI failed\n");
     return;
   }