fix: malformed charset param (#2263) (#2277)

Earlopain · AllyMarthaJ · web-flow · commit edb0869eec77 · 2025-01-31T11:27:22.000+13:00
If a content type header is provided with a malformed part, there's no
nice way of interpreting it since instead of being a key/value pair it's
just a key.

Instead, we mimic the behaviour of query parameters and opt to return an
empty string in lieu of missing values—this way we can still identify
their presence, but won't blow up. The behaviour isn't identical, but
we're also not worried about backwards compatibility here (given the
alternative was exploding)

Co-authored-by: Ally &lt;28497049+AllyMarthaJ@users.noreply.github.com&gt;
diff --git a/lib/rack/media_type.rb b/lib/rack/media_type.rb
@@ -27,6 +27,11 @@ def type(content_type)
       # provided.  e.g., when the CONTENT_TYPE is "text/plain;charset=utf-8",
       # this method responds with the following Hash:
       #   { 'charset' => 'utf-8' }
+      #
+      # This will pass back parameters with empty strings in the hash if they
+      # lack a value (e.g., "text/plain;charset=" will return { 'charset' => '' },
+      # and "text/plain;charset" will return { 'charset' => '' }, similarly to 
+      # the query params parser (barring the latter case, which returns nil instead)).
       def params(content_type)
         return {} if content_type.nil?
 
@@ -40,9 +45,9 @@ def params(content_type)
 
       private
 
-        def strip_doublequotes(str)
-          (str.start_with?('"') && str.end_with?('"')) ? str[1..-2] : str
-        end
+      def strip_doublequotes(str)
+        (str && str.start_with?('"') && str.end_with?('"')) ? str[1..-2] : str || ''
+      end
     end
   end
 end
diff --git a/test/spec_media_type.rb b/test/spec_media_type.rb
@@ -44,4 +44,28 @@
       Rack::MediaType.params(@content_type)['charset'].must_equal 'utf-8'
     end
   end
+
+  describe 'when content_type contains media_type and incomplete params' do 
+    before { @content_type = 'application/text;CHARSET' }
+
+    it '#type is application/text' do
+      Rack::MediaType.type(@content_type).must_equal 'application/text'
+    end
+
+    it '#params has key "charset" with value ""' do
+      Rack::MediaType.params(@content_type)['charset'].must_equal ''
+    end
+  end
+
+  describe 'when content_type contains media_type and empty params' do 
+    before { @content_type = 'application/text;CHARSET=' }
+
+    it '#type is application/text' do
+      Rack::MediaType.type(@content_type).must_equal 'application/text'
+    end
+
+    it '#params has key "charset" with value of empty string' do
+      Rack::MediaType.params(@content_type)['charset'].must_equal ''
+    end
+  end
 end
