diff --git a/app/controllers/login_controller.rb b/app/controllers/login_controller.rb
--- a/app/controllers/login_controller.rb
+++ b/app/controllers/login_controller.rb
@@ -1,5 +1,7 @@
 class LoginController < ApplicationController
 
+  @@authenticators = []
+  
   def index
     # show login screen
     reset_session
@@ -7,7 +9,7 @@
   end
 
   def login
-    user = User.authenticate(params[:login], params[:password])
+    user = get_authenticated_user(params[:login], params[:password])
     unless user
       flash[:notice] = 'Wrong password'
       redirect_to :controller => 'main', :action => 'login'
@@ -60,4 +62,24 @@
     end
   end
 
+  def self.add_authenticator(authenticator)
+    @@authenticators << authenticator
+  end
+  
+  protected
+
+  def get_authenticated_user(login, password)
+    if @@authenticators.empty? 
+      return User.authenticate(login, password)
+    else
+      user = User.authenticate(login, password)
+      @@authenticators.each do |authenticator|
+        if not user
+          user = authenticator.authenticate(login, password)
+        end
+      end
+      return user
+    end
+  end
+  
 end
diff --git a/app/controllers/problems_controller.rb b/app/controllers/problems_controller.rb
--- a/app/controllers/problems_controller.rb
+++ b/app/controllers/problems_controller.rb
@@ -29,7 +29,7 @@
 
   def create
     @problem = Problem.new(problem_params)
-    @description = Description.new(params[:description])
+    @description = Description.new(description_params)
     if @description.body!=''
       if !@description.save
         render :action => new and return
@@ -252,6 +252,10 @@
   ##################################
   protected
 
+  def description_params
+    params.require(:description).permit(:body, :markdowned)
+  end
+  
   def allow_test_pair_import?
     if defined? ALLOW_TEST_PAIR_IMPORT
       return ALLOW_TEST_PAIR_IMPORT
diff --git a/app/models/submission.rb b/app/models/submission.rb
--- a/app/models/submission.rb
+++ b/app/models/submission.rb
@@ -127,8 +127,10 @@
   end
 
   def assign_language
-    self.language = Submission.find_language_in_source(self.source,
-                                                       self.source_filename)
+    if self.language == nil
+      self.language = Submission.find_language_in_source(self.source,
+                                                         self.source_filename)
+    end
   end
 
   # validation codes
@@ -138,8 +140,8 @@
     # for output_only tasks
     return if self.problem!=nil and self.problem.output_only
 
-    if self.language==nil
-      errors.add('source',"Cannot detect language. Did you submit a correct source file?") unless self.language!=nil
+    if self.language == nil
+      errors.add('source',"Cannot detect language. Did you submit a correct source file?")
     end
   end
 
diff --git a/app/models/user.rb b/app/models/user.rb
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -40,7 +40,7 @@
   validates_length_of :full_name, :minimum => 1
   
   validates_presence_of :password, :if => :password_required?
-  validates_length_of :password, :within => 4..20, :if => :password_required?
+  validates_length_of :password, :within => 4..50, :if => :password_required?
   validates_confirmation_of :password, :if => :password_required?
 
   validates_format_of :email, 
diff --git a/app/views/submissions/edit.html.haml b/app/views/submissions/edit.html.haml
--- a/app/views/submissions/edit.html.haml
+++ b/app/views/submissions/edit.html.haml
@@ -59,7 +59,9 @@
           %span{aria: {hidden: 'true'}, data: {dismiss: 'modal'}} &times;
         %h4 Compiler message
       .modal-body
-        %pre#compiler_msg= @submission.compiler_message
+      %pre#compiler_msg
+        - if @submission
+          = @submission.compiler_message
       .modal-footer
         %button.btn.btn-default{type: 'button', data: {dismiss: 'modal'}} Close
 
diff --git a/config/initializers/cafe_grader_config.rb.SAMPLE b/config/initializers/cafe_grader_config.rb.SAMPLE
--- a/config/initializers/cafe_grader_config.rb.SAMPLE
+++ b/config/initializers/cafe_grader_config.rb.SAMPLE
@@ -28,3 +28,6 @@
 
 # Uncomment so that configuration is read only once when the server is loaded
 # CONFIGURATION_CACHE_ENABLED = true
+
+# Uncomment to allow authentication and user import from programming.in.th
+# LoginController.add_authenticator(ProgrammingAuthenticator.new)
diff --git a/db/seeds.rb b/db/seeds.rb
--- a/db/seeds.rb
+++ b/db/seeds.rb
@@ -102,6 +102,14 @@
      :default_value => 'false',
      :description => 'When true, any user can view/download test data'
    },
+   
+   {
+     :key => 'system.online_registration',
+     :value_type => 'boolean',
+     :default_value => 'false',
+     :description => 'This option enables online registration.'
+   },
+
    # If Configuration['system.online_registration'] is true, the
    # system allows online registration, and will use these
    # information for sending confirmation emails.
diff --git a/lib/programming_authenticator.rb b/lib/programming_authenticator.rb
new file mode 100644
--- /dev/null
+++ b/lib/programming_authenticator.rb
@@ -0,0 +1,33 @@
+# Authentication and user imports through programming.in.th web request
+require 'net/http'
+require 'uri'
+require 'json'
+
+class ProgrammingAuthenticator
+  PROGRAMMING_AUTHEN_URL = "https://programming.in.th/authen.php"
+
+  def find_or_create_user(result)
+    user = User.find_by(login: result['username'])
+    if not user
+      user = User.new(login: result['username'],
+                      full_name: result['firstname'] + ' ' + result['surname'],
+                      alias: result['display'],
+                      email: result['email'])
+      user.password = User.random_password
+      user.save
+    end
+    return user
+  end
+  
+  def authenticate(login, password)
+    uri = URI(PROGRAMMING_AUTHEN_URL)
+    result = Net::HTTP.post_form(uri, 'username' => login, 'password' => password)
+    request_result = JSON.parse(result.body)
+
+    if request_result.fetch('status', 'incorrect') == 'OK'
+      return find_or_create_user(request_result)
+    else
+      return nil
+    end
+  end
+end