fix incorrect ^$ usage leading to XSS in sanitize_css [CVE-2013-1855]

actionpack/lib/action_controller/vendor/html-scanner/html/sanitizer.rb

@@ -109,8 +109,8 @@ def sanitize_css(style)
       style = style.to_s.gsub(/url\s*\(\s*[^\s)]+?\s*\)\s*/, ' ')
 
       # gauntlet
-      if style !~ /^([:,;#%.\sa-zA-Z0-9!]|\w-\w|\'[\s\w]+\'|\"[\s\w]+\"|\([\d,\s]+\))*$/ ||
-          style !~ /^(\s*[-\w]+\s*:\s*[^:;]*(;|$)\s*)*$/
+      if style !~ /\A([:,;#%.\sa-zA-Z0-9!]|\w-\w|\'[\s\w]+\'|\"[\s\w]+\"|\([\d,\s]+\))*\z/ ||
+          style !~ /\A(\s*[-\w]+\s*:\s*[^:;]*(;|$)\s*)*\z/
         return ''
       end
 
@@ -121,7 +121,7 @@ def sanitize_css(style)
         elsif shorthand_css_properties.include?(prop.split('-')[0].downcase)
           unless val.split().any? do |keyword|
             !allowed_css_keywords.include?(keyword) &&
-              keyword !~ /^(#[0-9a-f]+|rgb\(\d+%?,\d*%?,?\d*%?\)?|\d{0,2}\.?\d{0,2}(cm|em|ex|in|mm|pc|pt|px|%|,|\))?)$/
+              keyword !~ /\A(#[0-9a-f]+|rgb\(\d+%?,\d*%?,?\d*%?\)?|\d{0,2}\.?\d{0,2}(cm|em|ex|in|mm|pc|pt|px|%|,|\))?)\z/
           end
             clean << prop + ': ' + val + ';'
           end

actionpack/test/template/html-scanner/sanitizer_test.rb

@@ -248,6 +248,11 @@ def test_should_sanitize_div_style_expression
     assert_equal '', sanitize_css(raw)
   end
 
+  def test_should_sanitize_across_newlines
+    raw = %(\nwidth:\nexpression(alert('XSS'));\n)
+    assert_equal '', sanitize_css(raw)
+  end
+
   def test_should_sanitize_img_vbscript
     assert_sanitized %(<img src='vbscript:msgbox("XSS")' />), '<img />'
   end