From 0dbb9168667424f68b8caeb43562d6e5668a0f01 Mon Sep 17 00:00:00 2001
From: sysops <sysops@LenovoT14Gen5>
Date: Sun, 12 Jul 2026 23:42:36 +0200
Subject: [PATCH] Fix nil-pointer crash generating QR codes for non-default
 servers

GetClients, GetClientByID, and SendRequestedConfigsToTelegram all
looked up the legacy "wg0" server unconditionally when building a
client's QR code / config, ignoring which server the client actually
belongs to. On any multi-server setup without a migrated wg0, the
server lookup returned a zero-value model.Server (error discarded),
and BuildClientConfig then dereferenced its nil KeyPair pointer,
panicking whenever a client's QR code was rendered.

Now looks up the client's own ServerID (falling back to wg0 only for
legacy clients with no ServerID set) and surfaces the lookup error
instead of silently continuing with an empty server.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
---
 store/jsondb/jsondb.go | 56 +++++++++++++++++++++++++++---------------
 util/util.go           | 10 +++++++-
 2 files changed, 45 insertions(+), 21 deletions(-)

diff --git a/store/jsondb/jsondb.go b/store/jsondb/jsondb.go
index 05bdf09..dc97028 100644
--- a/store/jsondb/jsondb.go
+++ b/store/jsondb/jsondb.go
@@ -412,14 +412,22 @@ func (o *JsonDB) GetClients(hasQRCode bool) ([]model.ClientData, error) {
 
 		// generate client qrcode image in base64
 		if hasQRCode && client.PrivateKey != "" {
-			server, _ := o.GetServerByID(util.DefaultServerID)
-			globalSettings, _ := o.GetGlobalSettings()
-
-			png, err := qrcode.Encode(util.BuildClientConfig(client, server, globalSettings), qrcode.Medium, 256)
-			if err == nil {
-				clientData.QRCode = "data:image/png;base64," + base64.StdEncoding.EncodeToString(png)
+			serverID := client.ServerID
+			if serverID == "" {
+				serverID = util.DefaultServerID
+			}
+			server, err := o.GetServerByID(serverID)
+			if err != nil {
+				fmt.Printf("Cannot generate QR code: server %s not found: %v\n", serverID, err)
 			} else {
-				fmt.Print("Cannot generate QR code: ", err)
+				globalSettings, _ := o.GetGlobalSettings()
+
+				png, err := qrcode.Encode(util.BuildClientConfig(client, server, globalSettings), qrcode.Medium, 256)
+				if err == nil {
+					clientData.QRCode = "data:image/png;base64," + base64.StdEncoding.EncodeToString(png)
+				} else {
+					fmt.Print("Cannot generate QR code: ", err)
+				}
 			}
 		}
 
@@ -442,21 +450,29 @@ func (o *JsonDB) GetClientByID(clientID string, qrCodeSettings model.QRCodeSetti
 
 	// generate client qrcode image in base64
 	if qrCodeSettings.Enabled && client.PrivateKey != "" {
-		server, _ := o.GetServerByID(util.DefaultServerID)
-		globalSettings, _ := o.GetGlobalSettings()
-		client := client
-		if !qrCodeSettings.IncludeDNS {
-			globalSettings.DNSServers = []string{}
+		serverID := client.ServerID
+		if serverID == "" {
+			serverID = util.DefaultServerID
 		}
-		if !qrCodeSettings.IncludeMTU {
-			globalSettings.MTU = 0
-		}
-
-		png, err := qrcode.Encode(util.BuildClientConfig(client, server, globalSettings), qrcode.Medium, 256)
-		if err == nil {
-			clientData.QRCode = "data:image/png;base64," + base64.StdEncoding.EncodeToString(png)
+		server, err := o.GetServerByID(serverID)
+		if err != nil {
+			fmt.Printf("Cannot generate QR code: server %s not found: %v\n", serverID, err)
 		} else {
-			fmt.Print("Cannot generate QR code: ", err)
+			globalSettings, _ := o.GetGlobalSettings()
+			client := client
+			if !qrCodeSettings.IncludeDNS {
+				globalSettings.DNSServers = []string{}
+			}
+			if !qrCodeSettings.IncludeMTU {
+				globalSettings.MTU = 0
+			}
+
+			png, err := qrcode.Encode(util.BuildClientConfig(client, server, globalSettings), qrcode.Medium, 256)
+			if err == nil {
+				clientData.QRCode = "data:image/png;base64," + base64.StdEncoding.EncodeToString(png)
+			} else {
+				fmt.Print("Cannot generate QR code: ", err)
+			}
 		}
 	}
 
diff --git a/util/util.go b/util/util.go
index 5999fc9..db3925b 100644
--- a/util/util.go
+++ b/util/util.go
@@ -633,7 +633,15 @@ func SendRequestedConfigsToTelegram(db store.IStore, userid int64) []string {
 			}
 
 			// build config
-			server, _ := db.GetServerByID(DefaultServerID)
+			serverID := clientData.Client.ServerID
+			if serverID == "" {
+				serverID = DefaultServerID
+			}
+			server, err := db.GetServerByID(serverID)
+			if err != nil {
+				failedList = append(failedList, clientData.Client.Name)
+				continue
+			}
 			globalSettings, _ := db.GetGlobalSettings()
 			config := BuildClientConfig(*clientData.Client, server, globalSettings)
 			configData := []byte(config)