golt: add GOLT_BIND_PORT option

Author: chowder

README.md

@@ -5,10 +5,12 @@
 # Why?
 
 [The official recommendation](https://help.jagex.com/hc/en-gb/articles/13413514881937-Downloading-the-Jagex-Launcher-on-Linux)
-points to several community projects, most of which involve running the launcher in Wine or a similar environment. However, I really wanted a native solution, or one
+points to several community projects, most of which involve running the launcher in Wine or a similar environment.
+However, I really wanted a native solution, or one
 that didn't require installing a 1.5GB compatibility layer solely for launcher functionality.
 
-While there is a project that served as the inspiration for this one, and functions seamlessly on Linux, there were some boxes that it didn't tick for me:
+While there is a project that served as the inspiration for this one, and functions seamlessly on Linux, there were some
+boxes that it didn't tick for me:
 
 - Its installation size is ~460MB
 - Lack of support for overriding the client launch command/environment
@@ -18,7 +20,8 @@ In comparison, the linux-amd64 build for `golt` is a single 6.8MB binary.
 
 # Installation
 
-Either download the latest binary from the [Releases](https://github.com/chowder/golt/releases) page (or build it yourself), and add it to a directory on your `PATH`.
+Either download the latest binary from the [Releases](https://github.com/chowder/golt/releases) page (or build it
+yourself), and add it to a directory on your `PATH`.
 
 Then, create a desktop entry for the application:
 
@@ -52,17 +55,18 @@ The login flow is currently done in the browser:
 - The OAuth login redirects to a page which invokes a scheme handler
 - The game login step redirects to `http://localhost`
 
-These redirect URLs are validated server side, so cannot be modified on the client side. 
+These redirect URLs are validated server side, so cannot be modified on the client side.
 
-As for the iptable entry, most Linux distros don't allow binding to port 80, so `golt` binds to port 8080 instead. 
+As for the iptable entry, most Linux distros don't allow binding to port 80, so `golt` binds to port 8080 instead.
 
 </details>
 
 # Configuration
 
-| Environment Variable | Default             | Description                                                                                                                                                    |
-|----------------------|---------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------|
-| `GOLT_GAME_PATH`     | `RuneLite.AppImage` | Either a binary on `PATH`, or an absolute path to the client to launch.<br/>This value is passed to `exec.Command`([docs](https://pkg.go.dev/os/exec#Command)) |
+| Environment Variable | Default             | Description                                                                                                                                                                                        |
+|----------------------|---------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| `GOLT_GAME_PATH`     | `RuneLite.AppImage` | Either a binary on `PATH`, or an absolute path to the client to launch.<br/>This value is passed to `exec.Command`([docs](https://pkg.go.dev/os/exec#Command))                                     |
+| `GOLT_BIND_PORT`     | `8080`              | Local port to which `golt` will bind to to receive the OAuth response callback.<br/>If this is not `80`, you must set up an iptable entry to redirect inbound traffic from port `80` to this port. |
 
 # Disclaimer
 

internal/golt/requests.go

@@ -11,7 +11,9 @@ import (
 	"github.com/pkg/browser"
 	"golang.org/x/oauth2"
 	"log"
+	"os"
 	"net/http"
+	"strconv"
 	"strings"
 )
 
@@ -179,10 +181,22 @@ func StandardLogin(idToken string) (*Tuple[string, string], error) {
 		channel <- Tuple[string, string]{code, idToken}
 	})
 
+	port := 8080 
+	
+	if val, exists := os.LookupEnv("GOLT_BIND_PORT"); exists {
+		var err error
+		port, err = strconv.Atoi(val)
+		if err != nil {
+			Die(errors.New("could not parse GOLT_BIND_PORT as integer"))
+		}
+	}
+
+	log.Println("Binding to port:", port)
+
 	// Start the server
 	server := &http.Server{
 		// TODO: sudo iptables -t nat -I OUTPUT -p tcp -d 127.0.0.1 --dport 80 -j REDIRECT --to-ports 8080
-		Addr:    ":8080",
+		Addr:    ":" + strconv.Itoa(port),
 		Handler: nil,
 	}
 	go func() {