Use binary coding for invalid charsets

Previously, this would raise an error for invalid charsets, but that
is unlikely to be desired behavior.

While here, inline the CHARSET constant, since it is only used in
a single case, and we are using frozen string literals.

2 files changed, 20 insertions, 1 deletions

diff --git a/lib/rack/multipart/parser.rb b/lib/rack/multipart/parser.rb
index ce82cb1b..8e770ecf 100644
--- a/lib/rack/multipart/parser.rb
+++ b/lib/rack/multipart/parser.rb
@@ -355,6 +355,7 @@ module Rack
       end
 
       CHARSET = "charset"
+      deprecate_constant :CHARSET
 
       def tag_multipart_encoding(filename, content_type, name, body)
         name = name.to_s
@@ -375,7 +376,13 @@ module Rack
               k.strip!
               v.strip!
               v = v[1..-2] if v.start_with?('"') && v.end_with?('"')
-              encoding = Encoding.find v if k == CHARSET
+              if k == "charset"
+                encoding = begin
+                  Encoding.find v
+                rescue ArgumentError
+                  Encoding::BINARY
+                end
+              end
             end
           end
         end
diff --git a/test/spec_multipart.rb b/test/spec_multipart.rb
index 1510b2a2..8e4a0c4c 100644
--- a/test/spec_multipart.rb
+++ b/test/spec_multipart.rb
@@ -76,6 +76,18 @@ describe Rack::Multipart do
     end
   end
 
+  it "sets BINARY encoding for invalid charsets" do
+    env = Rack::MockRequest.env_for("/", multipart_fixture(:content_type_and_unknown_charset))
+    params = Rack::Multipart.parse_multipart(env)
+    params["text"].encoding.must_equal Encoding::BINARY
+
+    # I'm not 100% sure if making the param name encoding match the
+    # content-type charset is the right thing to do.  We should revisit this.
+    params.keys.each do |key|
+      key.encoding.must_equal Encoding::BINARY
+    end
+  end
+
   it "set BINARY encoding on things without content type" do
     env = Rack::MockRequest.env_for("/", multipart_fixture(:none))
     params = Rack::Multipart.parse_multipart(env)