add reCaptcha support

main.go

@@ -40,7 +40,9 @@ var routes = Routes{
 		"SendMail",
 		"POST",
 		"/sendmail",
-		MuxSecAllowedDomainsHandler(http.HandlerFunc(SendMail)),
+		MuxSecAllowedDomainsHandler(
+			MuxSecReCaptchaHandler(
+				http.HandlerFunc(SendMail))),
 	},
 	Route{
 		"Healthz",

sendmail.go

@@ -4,7 +4,7 @@ Copyright 2020 Rodrigue Chakode and contributors.
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
-    
+
     http://www.apache.org/licenses/LICENSE-2.0
 
 Unless required by applicable law or agreed to in writing, software
@@ -27,6 +27,7 @@ import (
 	"net/smtp"
 	"strings"
 
+	"github.com/dpapathanasiou/go-recaptcha"
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/viper"
 )
@@ -180,6 +181,37 @@ func MuxSecAllowedDomainsHandler(next http.Handler) http.Handler {
 	})
 }
 
+// MuxSecReCaptchaHandler is a security middleware which verifies the challenge code from
+// the reCaptcha human verification system (provided by Google).
+func MuxSecReCaptchaHandler(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		recaptchaResponse, found := r.Form["g-recaptcha-response"]
+
+		if found {
+			remoteIp, _, _ := net.SplitHostPort(r.RemoteAddr)
+			recaptchaPrivateKey := viper.GetString("RECAPTCHA_PRIVATE_KEY")
+
+			recaptcha.Init(recaptchaPrivateKey)
+
+			result, err := recaptcha.Confirm(remoteIp, recaptchaResponse[0])
+			if err != nil {
+				log.WithFields(log.Fields{
+					"error": err,
+				}).Errorln("reCaptcha server error")
+				w.WriteHeader(http.StatusForbidden)
+				return
+			}
+
+			if !result {
+				w.WriteHeader(http.StatusForbidden)
+				return
+			}
+		}
+
+		next.ServeHTTP(w, r)
+	})
+}
+
 // SendMail handles HTTP request to send email
 func SendMail(httpResp http.ResponseWriter, httpReq *http.Request) {
 	httpReq.ParseForm()
@@ -234,12 +266,12 @@ func SendMail(httpResp http.ResponseWriter, httpReq *http.Request) {
 
 	replyTplFile := ""
 	if contactRequest.RequestTarget == "demo" {
-		replyTplFile = viper.GetString("TEMPLATE_DEMO_REQUEST_REPLY");
+		replyTplFile = viper.GetString("TEMPLATE_DEMO_REQUEST_REPLY")
 		if replyTplFile == "" {
 			replyTplFile = "./templates/template_reply_demo_request.html"
 		}
 	} else {
-		replyTplFile = viper.GetString("TEMPLATE_CONTACT_REQUEST_REPLY");
+		replyTplFile = viper.GetString("TEMPLATE_CONTACT_REQUEST_REPLY")
 		if replyTplFile == "" {
 			replyTplFile = "./templates/template_reply_contact_request.html"
 		}