expose TOTP setup key during enrollment

server/mfa.go

@@ -261,20 +261,36 @@ func (s *Server) renderTOTPPage(secret *storage.MFASecret, lastFail bool, issuer
 	// Prevent browser from caching the TOTP page (contains QR code with secret).
 	w.Header().Set("Cache-Control", "no-store")
 	var qrCode string
+	var totpKey string
 	if !secret.Confirmed {
 		var err error
+		totpKey, err = totpManualSecret(secret.Secret)
+		if err != nil {
+			s.logger.ErrorContext(r.Context(), "failed to load TOTP key", "err", err)
+			s.renderError(r, w, http.StatusInternalServerError, "Internal server error.")
+			return
+		}
+
 		qrCode, err = generateTOTPQRCode(secret.Secret)
 		if err != nil {
 			s.logger.ErrorContext(r.Context(), "failed to generate QR code", "err", err)
 			s.renderError(r, w, http.StatusInternalServerError, "Internal server error.")
 			return
 		}
 	}
-	if err := s.templates.totpVerify(r, w, r.URL.String(), issuer, connectorID, qrCode, lastFail); err != nil {
+	if err := s.templates.totpVerify(r, w, r.URL.String(), issuer, connectorID, qrCode, totpKey, lastFail); err != nil {
 		s.logger.ErrorContext(r.Context(), "server template error", "err", err)
 	}
 }
 
+func totpManualSecret(keyURL string) (string, error) {
+	generated, err := otp.NewKeyFromURL(keyURL)
+	if err != nil {
+		return "", fmt.Errorf("load TOTP key: %w", err)
+	}
+	return generated.Secret(), nil
+}
+
 func generateTOTPQRCode(keyURL string) (string, error) {
 	generated, err := otp.NewKeyFromURL(keyURL)
 	if err != nil {

server/mfa_test.go

@@ -0,0 +1,55 @@
+package server
+
+import (
+	"html/template"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+
+	"github.com/pquerna/otp/totp"
+	"github.com/stretchr/testify/require"
+)
+
+func TestTOTPManualSecret(t *testing.T) {
+	key, err := totp.Generate(totp.GenerateOpts{Issuer: "example", AccountName: "user@example.com"})
+	require.NoError(t, err)
+
+	manualSecret, err := totpManualSecret(key.String())
+	require.NoError(t, err)
+	require.Equal(t, key.Secret(), manualSecret)
+	require.NotContains(t, manualSecret, "otpauth://")
+
+	_, err = totpManualSecret("otpauth://totp/%ZZ")
+	require.Error(t, err)
+}
+
+func TestTOTPTemplateSecretOnlyProvidedForEnrollment(t *testing.T) {
+	key, err := totp.Generate(totp.GenerateOpts{Issuer: "example", AccountName: "user@example.com"})
+	require.NoError(t, err)
+
+	for _, test := range []struct {
+		name       string
+		totpKey    string
+		wantSecret bool
+	}{
+		{name: "enrollment", totpKey: key.Secret(), wantSecret: true},
+		{name: "verification", wantSecret: false},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			tmpl := &templates{totpVerifyTmpl: template.Must(template.New("totp").Parse("{{.TotpKey}}"))}
+			request := httptest.NewRequest("GET", "/mfa/totp", nil)
+			request.URL.RawQuery = url.Values{"req": []string{"request"}}.Encode()
+			response := httptest.NewRecorder()
+
+			secret := test.totpKey
+			require.NoError(t, tmpl.totpVerify(request, response, "/mfa/totp", "example", "connector", "", secret, false))
+			if test.wantSecret {
+				require.Contains(t, response.Body.String(), key.Secret())
+			} else {
+				require.NotContains(t, response.Body.String(), key.Secret())
+			}
+			require.False(t, strings.Contains(response.Body.String(), key.String()))
+		})
+	}
+}

server/templates.go

@@ -361,7 +361,7 @@ func (t *templates) approval(r *http.Request, w http.ResponseWriter, authReqID,
 	return renderTemplate(w, t.approvalTmpl, data)
 }
 
-func (t *templates) totpVerify(r *http.Request, w http.ResponseWriter, postURL, issuer, connector, qrCode string, lastWasInvalid bool) error {
+func (t *templates) totpVerify(r *http.Request, w http.ResponseWriter, postURL, issuer, connector, qrCode, totpKey string, lastWasInvalid bool) error {
 	if lastWasInvalid {
 		w.WriteHeader(http.StatusUnauthorized)
 	}
@@ -371,8 +371,9 @@ func (t *templates) totpVerify(r *http.Request, w http.ResponseWriter, postURL,
 		Issuer    string
 		Connector string
 		QRCode    string
+		TotpKey   string
 		ReqPath   string
-	}{postURL, lastWasInvalid, issuer, connector, qrCode, r.URL.Path}
+	}{postURL, lastWasInvalid, issuer, connector, qrCode, totpKey, r.URL.Path}
 	return renderTemplate(w, t.totpVerifyTmpl, data)
 }