Fix remote IP, fix title

backend/internal/auth/handler.go

@@ -1,10 +1,33 @@
 package auth
 
 import (
+	"net"
 	"net/http"
+	"strings"
 	"time"
 )
 
+// ExtractIP resolves the client's IP address from a request, accounting for the
+// reverse proxy in front of the backend. When the proxy forwards the original
+// address (X-Forwarded-For / X-Real-IP) the leftmost value is used; otherwise it
+// falls back to the connection's remote address.
+func ExtractIP(r *http.Request) string {
+	if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
+		ips := strings.Split(xff, ",")
+		return strings.TrimSpace(ips[0])
+	}
+
+	if realIP := r.Header.Get("X-Real-IP"); realIP != "" {
+		return realIP
+	}
+
+	ip, _, err := net.SplitHostPort(r.RemoteAddr)
+	if err != nil {
+		return r.RemoteAddr
+	}
+	return ip
+}
+
 func SigninSetup(w http.ResponseWriter, cookieName, cookieValue string, expiresAt time.Time, secure bool) {
 	maxAge := expiresAt.Sub(time.Now().UTC())
 	http.SetCookie(w, &http.Cookie{

backend/internal/rest/context.go

@@ -2,7 +2,6 @@ package rest
 
 import (
 	"fmt"
-	"net"
 	"net/http"
 
 	"goAuth/internal/auth"
@@ -27,14 +26,6 @@ func sessionFromRequest(r *http.Request) *auth.Session {
 	return session
 }
 
-func clientAddress(r *http.Request) string {
-	host, _, err := net.SplitHostPort(r.RemoteAddr)
-	if err != nil {
-		return r.RemoteAddr
-	}
-	return host
-}
-
 func formatUserId(id int64) string {
 	return fmt.Sprintf("user-%d", id)
 }

backend/internal/rest/handler_auth.go

@@ -39,7 +39,7 @@ func (h *Handler) signup(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	address := clientAddress(r)
+	address := auth.ExtractIP(r)
 	device := h.sessions.ClassifiedUserAgent(r.UserAgent())
 
 	u, session, err := h.sessions.RegisterUser(r.Context(), req.Login, req.Password, req.Invite, address, device)
@@ -64,7 +64,7 @@ func (h *Handler) signin(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	address := clientAddress(r)
+	address := auth.ExtractIP(r)
 	device := h.sessions.ClassifiedUserAgent(r.UserAgent())
 
 	u, session, err := h.sessions.LoginUser(r.Context(), req.Login, req.Password, address, device, req.Remember)

docker/nginx.conf

@@ -22,12 +22,18 @@ server {
     }
 
     # Proxy the API to the Go backend running alongside nginx.
+    #
+    # X-Forwarded-For is set to $remote_addr (the peer nginx actually saw), NOT
+    # $proxy_add_x_forwarded_for. The latter appends to any client-supplied
+    # header, which would let a client spoof its own IP since the backend trusts
+    # the leftmost value. If you deploy behind another trusted proxy, switch to
+    # $proxy_add_x_forwarded_for and make the backend read the correct hop.
     location /api/ {
         proxy_pass http://${BACKEND_HOST}:${BACKEND_PORT};
         proxy_http_version 1.1;
         proxy_set_header Host $host;
         proxy_set_header X-Real-IP $remote_addr;
-        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-For $remote_addr;
         proxy_set_header X-Forwarded-Proto $scheme;
     }
 }

frontend/index.html

@@ -3,7 +3,7 @@
   <head>
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-    <title>goChat</title>
+    <title>uPortal</title>
   </head>
   <body>
     <div id="root"></div>

frontend/nginx.conf.example

@@ -26,12 +26,17 @@ server {
 
     # Reverse proxy the API to the Go service. Keeping the same origin means
     # the session cookie (SameSite=Lax) and CSRF cookie work without CORS.
+    #
+    # X-Forwarded-For uses $remote_addr (the immediate peer) so a client cannot
+    # spoof its recorded session IP; the backend trusts the leftmost value. If
+    # this nginx sits behind another trusted proxy, use $proxy_add_x_forwarded_for
+    # and make the backend read the appropriate hop instead.
     location /api/ {
         proxy_pass http://127.0.0.1:8080;
         proxy_http_version 1.1;
         proxy_set_header Host $host;
         proxy_set_header X-Real-IP $remote_addr;
-        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-For $remote_addr;
         proxy_set_header X-Forwarded-Proto $scheme;
     }
 }