Minor clean ups for ruby strings and check method

Author: zeroSteiner

modules/exploits/windows/local/ms15_051_client_copy_image.rb

@@ -57,19 +57,17 @@ def initialize(info={})
   end
 
   def check
-    os = sysinfo["OS"]
-
-    if os !~ /windows/i
+    if sysinfo['OS'] !~ /windows/i
       return Exploit::CheckCode::Unknown
     end
 
-    if sysinfo["Architecture"] =~ /(wow|x)64/i
+    if sysinfo['Architecture'] =~ /(wow|x)64/i
       arch = ARCH_X86_64
-    elsif sysinfo["Architecture"] =~ /x86/i
+    elsif sysinfo['Architecture'] =~ /x86/i
       arch = ARCH_X86
     end
 
-    file_path = expand_path("%windir%") << "\\system32\\win32k.sys"
+    file_path = expand_path('%windir%') << '\\system32\\win32k.sys'
     major, minor, build, revision, branch = file_version(file_path)
     vprint_status("win32k.sys file version: #{major}.#{minor}.#{build}.#{revision} branch: #{branch}")
 
@@ -83,15 +81,15 @@ def exploit
       fail_with(Failure::None, 'Session is already elevated')
     end
 
-    if check == Exploit::CheckCode::Safe
-      fail_with(Failure::NotVulnerable, "Exploit not available on this system.")
+    if check == Exploit::CheckCode::Safe || check == Exploit::CheckCode::Unknown
+      fail_with(Failure::NotVulnerable, 'Exploit not available on this system.')
     end
 
-    if sysinfo["Architecture"] =~ /wow64/i
+    if sysinfo['Architecture'] =~ /wow64/i
       fail_with(Failure::NoTarget, 'Running against WOW64 is not supported')
-    elsif sysinfo["Architecture"] =~ /x64/ && target.arch.first == ARCH_X86
+    elsif sysinfo['Architecture'] =~ /x64/ && target.arch.first == ARCH_X86
       fail_with(Failure::NoTarget, 'Session host is x64, but the target is specified as x86')
-    elsif sysinfo["Architecture"] =~ /x86/ && target.arch.first == ARCH_X86_64
+    elsif sysinfo['Architecture'] =~ /x86/ && target.arch.first == ARCH_X86_64
       fail_with(Failure::NoTarget, 'Session host is x86, but the target is specified as x64')
     end