Skip header value with non-convertable encoding

sentry-ruby/lib/sentry/interfaces/request.rb

@@ -4,6 +4,7 @@ module Sentry
   class RequestInterface < Interface
     REQUEST_ID_HEADERS = %w(action_dispatch.request_id HTTP_X_REQUEST_ID).freeze
     CONTENT_HEADERS = %w(CONTENT_TYPE CONTENT_LENGTH).freeze
+    INVALID_ENCODING_MESSAGE = "[Filtered due to invalid encoding]"
     IP_HEADERS = [
       "REMOTE_ADDR",
       "HTTP_CLIENT_IP",
@@ -76,7 +77,18 @@ def filter_and_format_headers(env)
           # Rack stores headers as HTTP_WHAT_EVER, we need What-Ever
           key = key.sub(/^HTTP_/, "")
           key = key.split('_').map(&:capitalize).join('-')
-          memo[key] = value.to_s
+
+          value = value.to_s
+
+          if value.respond_to?(:force_encoding)
+            value = value.force_encoding(Encoding::UTF_8)
+          end
+
+          if !value.valid_encoding?
+            value = INVALID_ENCODING_MESSAGE
+          end
+
+          memo[key] = value
         rescue StandardError => e
           # Rails adds objects to the Rack env that can sometimes raise exceptions
           # when `to_s` is called.

sentry-ruby/spec/sentry/interfaces/request_interface_spec.rb

@@ -59,6 +59,17 @@
       end
     end
 
+    context 'with special characters' do
+      let(:additional_headers) { { "HTTP_FOO" => "\xC4" } }
+
+      it "doesn't cause any issue" do
+        interface = described_class.build(env: env)
+        json = JSON.generate(interface.to_hash)
+
+        expect(JSON.parse(json)["headers"]).to eq({"Content-Length"=>"0", "Foo"=>"[Filtered due to invalid encoding]"})
+      end
+    end
+
     context 'with additional env variables' do
       let(:mock) { double }
       let(:env) { { "some.variable" => mock } }