Wrap header values in quotes if they contain characters that are not allowed

Author: Alex Wieser

lib/mail/renderers/rfc_2822.ex

@@ -140,6 +140,7 @@ defmodule Mail.Renderers.RFC2822 do
 
   defp render_address({name, email}), do: "#{encode_header_value(~s("#{name}"), :quoted_printable)} <#{validate_address(email)}>"
   defp render_address(email), do: validate_address(email)
+
   defp render_subtypes([]), do: []
 
   defp render_subtypes([{key, value} | subtypes]) when is_atom(key),
@@ -152,6 +153,14 @@ defmodule Mail.Renderers.RFC2822 do
   defp render_subtypes([{key, value} | subtypes]) do
     key = String.replace(key, "_", "-")
     value = encode_header_value(value, :quoted_printable)
+
+    value =
+      if value =~ ~r/[\s;]/ do
+        "\"#{value}\""
+      else
+        value
+      end
+
     ["#{key}=#{value}" | render_subtypes(subtypes)]
   end
 

test/mail/renderers/rfc_2822_test.exs

@@ -15,6 +15,17 @@ defmodule Mail.Renderers.RFC2822Test do
     assert header == "Foo-Bar: abcd; baz-buzz=qux"
   end
 
+  test "quotes header parameters if necessary" do
+    header = Mail.Renderers.RFC2822.render_header("Content-Disposition", ["attachment", filename: "my-test-file"])
+    assert header == "Content-Disposition: attachment; filename=my-test-file"
+
+    header = Mail.Renderers.RFC2822.render_header("Content-Disposition", ["attachment", filename: "my test file"])
+    assert header == "Content-Disposition: attachment; filename=\"my test file\""
+
+    header = Mail.Renderers.RFC2822.render_header("Content-Disposition", ["attachment", filename: "my;test;file"])
+    assert header == "Content-Disposition: attachment; filename=\"my;test;file\""
+  end
+
   test "address headers renders list of recipients" do
     header = Mail.Renderers.RFC2822.render_header("from", "[email protected]")
     assert header == "From: [email protected]"