Implement CSRF protection

This commit adds CSRF protection based on the gorilla/csrf package.

Node dependencies have been updated.

Logging uses sirupsen/logrus for log level support now.

go.mod

@@ -4,7 +4,9 @@ go 1.13
 
 require (
 	github.com/BurntSushi/toml v0.3.1
+	github.com/gorilla/csrf v1.7.0
 	github.com/nicksnyder/go-i18n/v2 v2.1.1
+	github.com/sirupsen/logrus v1.7.0
 	golang.org/x/text v0.3.4
 	gopkg.in/yaml.v2 v2.4.0 // indirect
 )

go.sum

@@ -1,7 +1,23 @@
 github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/gorilla/csrf v1.7.0 h1:mMPjV5/3Zd460xCavIkppUdvnl5fPXMpv2uz2Zyg7/Y=
+github.com/gorilla/csrf v1.7.0/go.mod h1:+a/4tCmqhG6/w4oafeAZ9pEa3/NZOWYVbD9fV0FwIQA=
+github.com/gorilla/securecookie v1.1.1 h1:miw7JPhV+b/lAHSXz4qd/nN9jRiAFV5FwjeKyCS8BvQ=
+github.com/gorilla/securecookie v1.1.1/go.mod h1:ra0sb63/xPlUeL+yeDciTfxMRAA+MP+HVt/4epWDjd4=
 github.com/nicksnyder/go-i18n/v2 v2.1.1 h1:ATCOanRDlrfKVB4WHAdJnLEqZtDmKYsweqsOUYflnBU=
 github.com/nicksnyder/go-i18n/v2 v2.1.1/go.mod h1:d++QJC9ZVf7pa48qrsRWhMJ5pSHIPmS3OLqK1niyLxs=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/sirupsen/logrus v1.7.0 h1:ShrD1U9pZB12TX0cVy0DtePoCH97K8EtX+mg7ZARUtM=
+github.com/sirupsen/logrus v1.7.0/go.mod h1:yWOB1SBYBC5VeMP7gHvWumXLIWorT60ONWic61uBYv0=
+github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
+github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
+golang.org/x/sys v0.0.0-20191026070338-33540a1f6037 h1:YyJpGZS1sBuBCzLAR1VEpK193GlqGZbnPFnPV/5Rsb4=
+golang.org/x/sys v0.0.0-20191026070338-33540a1f6037/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/text v0.3.4 h1:0YWbFKbhXG/wIiuHDSKpS0Iy7FSA+u45VtBMfQcFTTc=
 golang.org/x/text v0.3.4/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=

main.go

@@ -2,19 +2,22 @@ package main
 
 import (
 	"bytes"
+	"crypto/rand"
 	"crypto/tls"
 	"encoding/json"
 	"fmt"
 	"html/template"
 	"io/ioutil"
-	"log"
 	"net/http"
+	"os"
 	"os/exec"
 	"strings"
 	"time"
 
 	"github.com/BurntSushi/toml"
+	"github.com/gorilla/csrf"
 	"github.com/nicksnyder/go-i18n/v2/i18n"
+	log "github.com/sirupsen/logrus"
 	"golang.org/x/text/language"
 )
 
@@ -32,13 +35,28 @@ type responseData struct {
 func (h *signCertificate) sign(csrPem string, commonName string) (certPem string, err error) {
 	log.Printf("received CSR for %s:\n\n%s", commonName, csrPem)
 	subjectDN := fmt.Sprintf("/CN=%s", commonName)
-	err = ioutil.WriteFile("in.pem", []byte(csrPem), 0644)
+	var csrFile *os.File
-	if err != nil {
+	if csrFile, err = ioutil.TempFile("", "*.csr.pem"); err != nil {
-		log.Print(err)
+		log.Errorf("could not open temporary file: %s", err)
 		return
 	}
+	if _, err = csrFile.Write([]byte(csrPem)); err != nil {
+		log.Errorf("could not write CSR to file: %s", err)
+		return
+	}
+	if err = csrFile.Close(); err != nil {
+		log.Errorf("could not close CSR file: %s", err)
+		return
+	}
+	defer func(file *os.File) {
+		err = os.Remove(file.Name())
+		if err != nil {
+			log.Errorf("could not remove temporary file: %s", err)
+		}
+	}(csrFile)
+
 	opensslCommand := exec.Command(
-		"openssl", "ca", "-config", "ca.cnf", "-days", "365",
+		"openssl", "ca", "-config", "ca.cnf",
 		"-policy", "policy_match", "-extensions", "client_ext",
 		"-batch", "-subj", subjectDN, "-utf8", "-rand_serial", "-in", "in.pem")
 	var out, cmdErr bytes.Buffer
@@ -159,6 +177,7 @@ func (i *indexHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		"CSRButtonLabel":     csrButtonLabel,
 		"StatusLoading":      statusLoading,
 		"SendCSRButtonLabel": sendCSRButtonLabel,
+		csrf.TemplateTag:     csrf.TemplateField(r),
 	})
 	if err != nil {
 		log.Panic(err)
@@ -207,6 +226,18 @@ func (j *jsLocalesHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+func generateRandomBytes(count int) []byte {
+	randomBytes := make([]byte, count)
+
+	_, err := rand.Read(randomBytes)
+	if err != nil {
+		log.Fatalf("could not read random bytes: %v", err)
+		return nil
+	}
+
+	return randomBytes
+}
+
 func main() {
 	tlsConfig := &tls.Config{
 		CipherSuites: []uint16{
@@ -227,6 +258,7 @@ func main() {
 	}
 
 	mux := http.NewServeMux()
+	csrfKey := generateRandomBytes(32)
 	mux.Handle("/sign/", &signCertificate{})
 	mux.Handle("/", &indexHandler{Bundle: bundle})
 	fileServer := http.FileServer(http.Dir("./public"))
@@ -235,7 +267,7 @@ func main() {
 	mux.Handle("/locales/", &jsLocalesHandler{Bundle: bundle})
 	server := http.Server{
 		Addr:              ":8000",
-		Handler:           mux,
+		Handler:           csrf.Protect(csrfKey, csrf.FieldName("csrfToken"), csrf.RequestHeader("X-CSRF-Token"))(mux),
 		TLSConfig:         tlsConfig,
 		ReadTimeout:       20 * time.Second,
 		ReadHeaderTimeout: 5 * time.Second,

src/index.html

@@ -61,7 +61,8 @@
     <div class="row">
         <div class="col-12">
             <div id="result">
-                <button type="button" disabled id="send-button" class="btn btn-default disabled">Send signing request</button>
+                <button type="button" disabled id="send-button" class="btn btn-default disabled">Send signing request
+                </button>
             </div>
         </div>
     </div>
@@ -91,6 +92,10 @@
     }
 
     document.addEventListener("DOMContentLoaded", function () {
+        i18n.init({fallbackLng: 'en', debug: true}, (err) => {
+            if (err) return console.log('something went wrong loading', err);
+        });
+
         const keyElement = document.getElementById('key');
         document.getElementById('csr-form').onsubmit = function (event) {
             const subject = event.target["nameInput"].value;

templates/index.html

@@ -6,7 +6,7 @@
 
     <!-- Bootstrap CSS -->
     <link rel="stylesheet" href="css/styles.min.css"
-          integrity="sha384-z6vVrRFOae08oK23yt6itLI8bfPDebhJw60IbTu43zFoAELolv/CiNUBScry21Fa" crossorigin="anonymous">
+          integrity="sha384-vKuz4xd0kXa+x9wRdibDAVE8gXC/1up2T9QVSas8Rk07AZhzOzbwFdj00XUjOO4i" crossorigin="anonymous">
     <meta name="theme-color" content="#ffffff">
 
     <title>{{ .Title }}</title>
@@ -17,6 +17,7 @@
     <div class="row">
         <div class="col-12">
             <form id="csr-form">
+                {{ .csrfField }}
                 <div class="form-group">
                     <label for="nameInput">{{ .NameLabel }}</label>
                     <input type="text" class="form-control" id="nameInput" aria-describedby="nameHelp" required
@@ -79,7 +80,7 @@
 <script src="js/i18next.min.js" integrity="sha384-Juj1kpjwKBUTV6Yp9WHG4GdeoMxCmx0zBN9SkwlyrAh5QYWb3l4WrfG7oTv/b00a"
         crossorigin="anonymous"></script>
 <script>
-    async function postData(url = '', data = {}) {
+    async function postData(url = '', data = {}, csrfToken) {
         const response = await fetch(url, {
             method: 'POST',
             mode: 'cors',
@@ -87,6 +88,7 @@
             credentials: 'same-origin',
             headers: {
                 'Content-Type': 'application/json',
+                'X-CSRF-Token': csrfToken,
             },
             redirect: "error",
             referrerPolicy: "no-referrer",
@@ -104,6 +106,7 @@
         document.getElementById('csr-form').onsubmit = function (event) {
             const subject = event.target["nameInput"].value;
             const password = event.target["passwordInput"].value;
+            const csrfToken = event.target["csrfToken"].value;
             const keySize = parseInt(event.target["keySize"].value);
             if (isNaN(keySize)) {
                 return false;
@@ -145,7 +148,7 @@
                         const sendButton =
                             document.getElementById("send-button");
                         sendButton.addEventListener("click", function () {
-                            postData("/sign/", {"csr": csrPem, "commonName": subject})
+                            postData("/sign/", {"csr": csrPem, "commonName": subject}, csrfToken)
                                 .then(data => {
                                     console.log(data);
                                     document.getElementById("crt").innerHTML = data["certificate"];