From 6274fc5f5ed971a81ee6ff30c0ed72b58ac4ce66 Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Tue, 7 May 2019 08:15:39 +0200
Subject: ringlogger: export R/O handle for UI process

---
 main.go                          |  2 --
 ringlogger/ringlogger_windows.go | 52 ++++++++++++++++++++++++----------------
 service/securityapi.go           |  2 +-
 service/service_manager.go       |  3 ++-
 4 files changed, 35 insertions(+), 24 deletions(-)

diff --git a/main.go b/main.go
index c68118a8..18b83e92 100644
--- a/main.go
+++ b/main.go
@@ -11,7 +11,6 @@ import (
 	"golang.zx2c4.com/wireguard/windows/ringlogger"
 	"golang.zx2c4.com/wireguard/windows/service"
 	"golang.zx2c4.com/wireguard/windows/ui"
-	"log"
 	"os"
 	"strconv"
 	"strings"
@@ -175,7 +174,6 @@ func main() {
 		if err != nil {
 			fatal(err)
 		}
-		log.SetOutput(ringlogger.Global)
 		service.InitializeIPCClient(readPipe, writePipe, eventPipe)
 		ui.RunUI()
 		return
diff --git a/ringlogger/ringlogger_windows.go b/ringlogger/ringlogger_windows.go
index 1e0b4b76..4c142e6a 100644
--- a/ringlogger/ringlogger_windows.go
+++ b/ringlogger/ringlogger_windows.go
@@ -36,10 +36,11 @@ type logMem struct {
 }
 
 type Ringlogger struct {
-	tag     string
-	file    *os.File
-	mapping windows.Handle
-	log     *logMem
+	tag      string
+	file     *os.File
+	mapping  windows.Handle
+	log      *logMem
+	readOnly bool
 }
 
 func NewRinglogger(filename string, tag string) (*Ringlogger, error) {
@@ -55,7 +56,7 @@ func NewRinglogger(filename string, tag string) (*Ringlogger, error) {
 	if err != nil {
 		return nil, err
 	}
-	rl, err := NewRingloggerFromMappingHandle(mapping, tag)
+	rl, err := newRingloggerFromMappingHandle(mapping, tag, windows.FILE_MAP_WRITE)
 	if err != nil {
 		return nil, err
 	}
@@ -63,8 +64,16 @@ func NewRinglogger(filename string, tag string) (*Ringlogger, error) {
 	return rl, nil
 }
 
-func NewRingloggerFromMappingHandle(mappingHandle windows.Handle, tag string) (*Ringlogger, error) {
-	view, err := windows.MapViewOfFile(mappingHandle, windows.FILE_MAP_WRITE, 0, 0, 0)
+func NewRingloggerFromInheritedMappingHandle(handleStr string, tag string) (*Ringlogger, error) {
+	handle, err := strconv.ParseUint(handleStr, 10, 64)
+	if err != nil {
+		return nil, err
+	}
+	return newRingloggerFromMappingHandle(windows.Handle(handle), tag, windows.FILE_MAP_READ)
+}
+
+func newRingloggerFromMappingHandle(mappingHandle windows.Handle, tag string, access uint32) (*Ringlogger, error) {
+	view, err := windows.MapViewOfFile(mappingHandle, access, 0, 0, 0)
 	if err != nil {
 		return nil, err
 	}
@@ -83,23 +92,20 @@ func NewRingloggerFromMappingHandle(mappingHandle windows.Handle, tag string) (*
 	}
 
 	rl := &Ringlogger{
-		tag:     tag,
-		mapping: mappingHandle,
-		log:     log,
+		tag:      tag,
+		mapping:  mappingHandle,
+		log:      log,
+		readOnly: access&windows.FILE_MAP_WRITE == 0,
 	}
 	runtime.SetFinalizer(rl, (*Ringlogger).Close)
 	return rl, nil
 }
 
-func NewRingloggerFromInheritedMappingHandle(handleStr string, tag string) (*Ringlogger, error) {
-	handle, err := strconv.ParseUint(handleStr, 10, 64)
-	if err != nil {
-		return nil, err
+func (rl *Ringlogger) Write(p []byte) (n int, err error) {
+	if rl.readOnly {
+		return 0, io.ErrShortWrite
 	}
-	return NewRingloggerFromMappingHandle(windows.Handle(handle), tag)
-}
 
-func (rl *Ringlogger) Write(p []byte) (n int, err error) {
 	// Race: This isn't synchronized with the fetch_add below, so items might be slightly out of order.
 	ts := time.Now().UnixNano()
 
@@ -219,11 +225,17 @@ func (rl *Ringlogger) Close() error {
 	return nil
 }
 
-func (rl *Ringlogger) ExportInheritableMappingHandleStr() (str string, err error) {
-	err = windows.SetHandleInformation(rl.mapping, windows.HANDLE_FLAG_INHERIT, windows.HANDLE_FLAG_INHERIT)
+func (rl *Ringlogger) ExportInheritableMappingHandleStr() (str string, handleToClose windows.Handle, err error) {
+	handleToClose, err = windows.CreateFileMapping(windows.Handle(rl.file.Fd()), nil, windows.PAGE_READONLY, 0, 0, nil)
+	if err != nil {
+		return
+	}
+	err = windows.SetHandleInformation(handleToClose, windows.HANDLE_FLAG_INHERIT, windows.HANDLE_FLAG_INHERIT)
 	if err != nil {
+		windows.Close(handleToClose)
+		handleToClose = 0
 		return
 	}
-	str = strconv.FormatUint(uint64(rl.mapping), 10)
+	str = strconv.FormatUint(uint64(handleToClose), 10)
 	return
 }
diff --git a/service/securityapi.go b/service/securityapi.go
index 6c5f7844..6373fd7c 100644
--- a/service/securityapi.go
+++ b/service/securityapi.go
@@ -154,4 +154,4 @@ func getCurrentSecurityAttributes() (*syscall.SecurityAttributes, error) {
 		return nil, err
 	}
 	return securityAttributes, nil
-}
\ No newline at end of file
+}
diff --git a/service/service_manager.go b/service/service_manager.go
index e8818ae4..e2ccf4c9 100644
--- a/service/service_manager.go
+++ b/service/service_manager.go
@@ -143,7 +143,7 @@ func (service *managerService) Execute(args []string, r <-chan svc.ChangeRequest
 				log.Printf("Unable to listen on IPC pipes: %v", err)
 				return
 			}
-			theirLogMapping, err := ringlogger.Global.ExportInheritableMappingHandleStr()
+			theirLogMapping, theirLogMappingHandle, err := ringlogger.Global.ExportInheritableMappingHandleStr()
 			if err != nil {
 				log.Printf("Unable to export inheritable mapping handle for logging: %v", err)
 				return
@@ -173,6 +173,7 @@ func (service *managerService) Execute(args []string, r <-chan svc.ChangeRequest
 			theirReader.Close()
 			theirWriter.Close()
 			theirEvents.Close()
+			windows.Close(theirLogMappingHandle)
 			runtime.UnlockOSThread()
 			if err != nil {
 				log.Printf("Unable to start manager UI process: %v", err)
-- 
cgit v1.2.3-59-g8ed1b