From bddc882f7d12a0d178a5735a07036224f2507bff Mon Sep 17 00:00:00 2001
From: Brad Fitzpatrick <bradfitz@tailscale.com>
Date: Tue, 10 Nov 2020 11:30:05 -0800
Subject: [PATCH] net/interfaces: ignore bogus proxy URLs from winhttp
 [windows]

Updates tailscale/corp#853

(cherry picked from commit d192bd0f860e6beacc63390b9b21a7b691923d31)
---
 net/interfaces/interfaces_windows.go | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/interfaces/interfaces_windows.go b/net/interfaces/interfaces_windows.go
index bf6fff8a9..19e9b48b4 100644
--- a/net/interfaces/interfaces_windows.go
+++ b/net/interfaces/interfaces_windows.go
@@ -7,6 +7,7 @@ package interfaces
 import (
 	"fmt"
 	"log"
+	"net/url"
 	"os/exec"
 	"syscall"
 	"unsafe"
@@ -176,7 +177,12 @@ func getPACWindows() string {
 			return ""
 		}
 		defer globalFree.Call(uintptr(unsafe.Pointer(res)))
-		return windows.UTF16PtrToString(res)
+		s := windows.UTF16PtrToString(res)
+		if _, err := url.Parse(s); err != nil {
+			log.Printf("getPACWindows: invalid URL %q from winhttp; ignoring", s)
+			return ""
+		}
+		return s
 	}
 	const (
 		ERROR_WINHTTP_AUTODETECTION_FAILED = 12180