From 0c03773c4c14f510e06d3fbbd69d7f300a842779 Mon Sep 17 00:00:00 2001
From: Gabe Kangas <gabek@real-ity.com>
Date: Wed, 28 Dec 2022 21:30:06 -0800
Subject: [PATCH] Sanitize+truncate display names on registration+change. For 
 #2527

---
 controllers/chat.go   |  7 +++++--
 core/chat/events.go   |  5 ++---
 utils/strings.go      | 29 +++++++++++++++++++++++++++++
 utils/strings_test.go | 32 ++++++++++++++++++++++++++++++++
 4 files changed, 68 insertions(+), 5 deletions(-)
 create mode 100644 utils/strings.go
 create mode 100644 utils/strings_test.go

diff --git a/controllers/chat.go b/controllers/chat.go
index 6dd40bdd0..9b4305647 100644
--- a/controllers/chat.go
+++ b/controllers/chat.go
@@ -4,9 +4,11 @@ import (
 	"encoding/json"
 	"net/http"
 
+	"github.com/owncast/owncast/config"
 	"github.com/owncast/owncast/core/chat"
 	"github.com/owncast/owncast/core/user"
 	"github.com/owncast/owncast/router/middleware"
+	"github.com/owncast/owncast/utils"
 	log "github.com/sirupsen/logrus"
 )
 
@@ -76,7 +78,8 @@ func RegisterAnonymousChatUser(w http.ResponseWriter, r *http.Request) {
 		request.DisplayName = r.Header.Get("X-Forwarded-User")
 	}
 
-	newUser, accessToken, err := user.CreateAnonymousUser(request.DisplayName)
+	proposedNewDisplayName := utils.MakeSafeStringOfLength(request.DisplayName, config.MaxChatDisplayNameLength)
+	newUser, accessToken, err := user.CreateAnonymousUser(proposedNewDisplayName)
 	if err != nil {
 		WriteSimpleResponse(w, false, err.Error())
 		return
@@ -85,7 +88,7 @@ func RegisterAnonymousChatUser(w http.ResponseWriter, r *http.Request) {
 	response := registerAnonymousUserResponse{
 		ID:          newUser.ID,
 		AccessToken: accessToken,
-		DisplayName: newUser.DisplayName,
+		DisplayName: proposedNewDisplayName,
 	}
 
 	w.Header().Set("Content-Type", "application/json")
diff --git a/core/chat/events.go b/core/chat/events.go
index 081a1532c..6e10b940d 100644
--- a/core/chat/events.go
+++ b/core/chat/events.go
@@ -11,6 +11,7 @@ import (
 	"github.com/owncast/owncast/core/data"
 	"github.com/owncast/owncast/core/user"
 	"github.com/owncast/owncast/core/webhooks"
+	"github.com/owncast/owncast/utils"
 	log "github.com/sirupsen/logrus"
 )
 
@@ -27,9 +28,7 @@ func (s *Server) userNameChanged(eventData chatClientEvent) {
 	blocklist := data.GetForbiddenUsernameList()
 
 	// Names have a max length
-	if len(proposedUsername) > config.MaxChatDisplayNameLength {
-		proposedUsername = proposedUsername[:config.MaxChatDisplayNameLength]
-	}
+	proposedUsername = utils.MakeSafeStringOfLength(proposedUsername, config.MaxChatDisplayNameLength)
 
 	for _, blockedName := range blocklist {
 		normalizedName := strings.TrimSpace(blockedName)
diff --git a/utils/strings.go b/utils/strings.go
new file mode 100644
index 000000000..1ad45c547
--- /dev/null
+++ b/utils/strings.go
@@ -0,0 +1,29 @@
+package utils
+
+import (
+	"strings"
+
+	"github.com/microcosm-cc/bluemonday"
+)
+
+// StripHTML will strip HTML tags from a string.
+func StripHTML(s string) string {
+	p := bluemonday.NewPolicy()
+	return p.Sanitize(s)
+}
+
+// MakeSafeStringOfLength will take a string and strip HTML tags,
+// trim whitespace, and limit the length.
+func MakeSafeStringOfLength(s string, length int) string {
+	newString := s
+	newString = StripHTML(newString)
+
+	if len(newString) > length {
+		newString = newString[:length]
+	}
+
+	newString = strings.ReplaceAll(newString, "\r", "")
+	newString = strings.TrimSpace(newString)
+
+	return newString
+}
diff --git a/utils/strings_test.go b/utils/strings_test.go
new file mode 100644
index 000000000..7d6ea2520
--- /dev/null
+++ b/utils/strings_test.go
@@ -0,0 +1,32 @@
+package utils
+
+import (
+	"fmt"
+	"testing"
+)
+
+// TestStripHTML tests the StripHTML function.
+func TestStripHTML(t *testing.T) {
+	requestedString := `<p><img src="img.png"/>Some text</p>`
+	expectedResult := `Some text`
+
+	result := StripHTML(requestedString)
+	fmt.Println(result)
+
+	if result != expectedResult {
+		t.Errorf("Expected %s, got %s", expectedResult, result)
+	}
+}
+
+// TestSafeString tests the TestSafeString function.
+func TestSafeString(t *testing.T) {
+	requestedString := `<p><img src="img.png"/>   Some text blah blah blah blah blah blahb albh</p>`
+	expectedResult := `Some te`
+
+	result := MakeSafeStringOfLength(requestedString, 10)
+	fmt.Println(result)
+
+	if result != expectedResult {
+		t.Errorf("Expected %s, got %s", expectedResult, result)
+	}
+}