Add a new "firefox" plugin to work around Firefox evil plan

dnscrypt-proxy/plugin_firefox.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"strings"
+
+	"github.com/jedisct1/dlog"
+	"github.com/miekg/dns"
+)
+
+type PluginFirefox struct {
+}
+
+func (plugin *PluginFirefox) Name() string {
+	return "firefox"
+}
+
+func (plugin *PluginFirefox) Description() string {
+	return "Work around Firefox taking over DNS"
+}
+
+func (plugin *PluginFirefox) Init(proxy *Proxy) error {
+	dlog.Noticef("Firefox workaround initialized")
+	return nil
+}
+
+func (plugin *PluginFirefox) Drop() error {
+	return nil
+}
+
+func (plugin *PluginFirefox) Reload() error {
+	return nil
+}
+
+func (plugin *PluginFirefox) Eval(pluginsState *PluginsState, msg *dns.Msg) error {
+	questions := msg.Question
+	if len(questions) != 1 {
+		return nil
+	}
+	question := questions[0]
+	if question.Qclass != dns.ClassINET || (question.Qtype != dns.TypeA && question.Qtype != dns.TypeAAAA) {
+		return nil
+	}
+	qName := strings.ToLower(question.Name)
+	if qName != "use-application-dns.net." && !strings.HasSuffix(qName, ".use-application-dns.net.") {
+		return nil
+	}
+	synth, err := EmptyResponseFromMessage(msg)
+	if err != nil {
+		return err
+	}
+	synth.Rcode = dns.RcodeNameError
+	pluginsState.synthResponse = synth
+	pluginsState.action = PluginsActionSynth
+	pluginsState.returnCode = PluginsReturnCodeSynth
+	return nil
+}

dnscrypt-proxy/plugins.go

@@ -86,6 +86,9 @@ func InitPluginsGlobals(pluginsGlobals *PluginsGlobals, proxy *Proxy) error {
 	if len(proxy.whitelistNameFile) != 0 {
 		*queryPlugins = append(*queryPlugins, Plugin(new(PluginWhitelistName)))
 	}
+
+	*queryPlugins = append(*queryPlugins, Plugin(new(PluginFirefox)))
+
 	if len(proxy.blockNameFile) != 0 {
 		*queryPlugins = append(*queryPlugins, Plugin(new(PluginBlockName)))
 	}