syscall: do not pass console handles to PROC_THREAD_ATTRIBUTE_HANDLE_LIST on Windows 7

On Windows 7 (and below), console handles are not real kernel handles
but are rather userspace objects, with information passed via special
bits in the handle itself. That means they can't be passed in
PROC_THREAD_ATTRIBUTE_HANDLE_LIST, even though they can be inherited.
So, we filter the list passed to PROC_THREAD_ATTRIBUTE_HANDLE_LIST to
not have any console handles on Windows 7. At the same time, it turns
out that the presence of a NULL handle in the list is enough to render
PROC_THREAD_ATTRIBUTE_HANDLE_LIST completely useless, so filter these
out too. Console handles also can't be duplicated into parent processes,
as inhertance always happens from the present process, so duplicate
always into the present process even when a parent process is specified.

Fixes #45914.

Change-Id: I70b4ff4874dbf0507d9ec9278f63b9b4dd4f1999
Reviewed-on: https://go-review.googlesource.com/c/go/+/319310
Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Trust: Alex Brainman <alex.brainman@gmail.com>
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

1 files changed, 47 insertions, 7 deletions

diff --git a/src/syscall/exec_windows.go b/src/syscall/exec_windows.go
index 253e9e8c1f..18d15028c3 100644
--- a/src/syscall/exec_windows.go
+++ b/src/syscall/exec_windows.go
@@ -313,6 +313,17 @@ func StartProcess(argv0 string, argv []string, attr *ProcAttr) (pid int, handle
 		}
 	}
 
+	var maj, min, build uint32
+	rtlGetNtVersionNumbers(&maj, &min, &build)
+	isWin7 := maj < 6 || (maj == 6 && min <= 1)
+	// NT kernel handles are divisible by 4, with the bottom 3 bits left as
+	// a tag. The fully set tag correlates with the types of handles we're
+	// concerned about here.  Except, the kernel will interpret some
+	// special handle values, like -1, -2, and so forth, so kernelbase.dll
+	// checks to see that those bottom three bits are checked, but that top
+	// bit is not checked.
+	isLegacyWin7ConsoleHandle := func(handle Handle) bool { return isWin7 && handle&0x10000003 == 3 }
+
 	p, _ := GetCurrentProcess()
 	parentProcess := p
 	if sys.ParentProcess != 0 {
@@ -321,7 +332,15 @@ func StartProcess(argv0 string, argv []string, attr *ProcAttr) (pid int, handle
 	fd := make([]Handle, len(attr.Files))
 	for i := range attr.Files {
 		if attr.Files[i] > 0 {
-			err := DuplicateHandle(p, Handle(attr.Files[i]), parentProcess, &fd[i], 0, true, DUPLICATE_SAME_ACCESS)
+			destinationProcessHandle := parentProcess
+
+			// On Windows 7, console handles aren't real handles, and can only be duplicated
+			// into the current process, not a parent one, which amounts to the same thing.
+			if parentProcess != p && isLegacyWin7ConsoleHandle(Handle(attr.Files[i])) {
+				destinationProcessHandle = p
+			}
+
+			err := DuplicateHandle(p, Handle(attr.Files[i]), destinationProcessHandle, &fd[i], 0, true, DUPLICATE_SAME_ACCESS)
 			if err != nil {
 				return 0, 0, err
 			}
@@ -351,19 +370,40 @@ func StartProcess(argv0 string, argv []string, attr *ProcAttr) (pid int, handle
 	si.StdErr = fd[2]
 
 	fd = append(fd, sys.AdditionalInheritedHandles...)
+
+	// On Windows 7, console handles aren't real handles, so don't pass them
+	// through to PROC_THREAD_ATTRIBUTE_HANDLE_LIST.
+	for i := range fd {
+		if isLegacyWin7ConsoleHandle(fd[i]) {
+			fd[i] = 0
+		}
+	}
+
+	// The presence of a NULL handle in the list is enough to cause PROC_THREAD_ATTRIBUTE_HANDLE_LIST
+	// to treat the entire list as empty, so remove NULL handles.
+	j := 0
+	for i := range fd {
+		if fd[i] != 0 {
+			fd[j] = fd[i]
+			j++
+		}
+	}
+	fd = fd[:j]
+
 	// Do not accidentally inherit more than these handles.
-	err = updateProcThreadAttribute(si.ProcThreadAttributeList, 0, _PROC_THREAD_ATTRIBUTE_HANDLE_LIST, unsafe.Pointer(&fd[0]), uintptr(len(fd))*unsafe.Sizeof(fd[0]), nil, nil)
-	if err != nil {
-		return 0, 0, err
+	if len(fd) > 0 {
+		err = updateProcThreadAttribute(si.ProcThreadAttributeList, 0, _PROC_THREAD_ATTRIBUTE_HANDLE_LIST, unsafe.Pointer(&fd[0]), uintptr(len(fd))*unsafe.Sizeof(fd[0]), nil, nil)
+		if err != nil {
+			return 0, 0, err
+		}
 	}
 
 	pi := new(ProcessInformation)
-
 	flags := sys.CreationFlags | CREATE_UNICODE_ENVIRONMENT | _EXTENDED_STARTUPINFO_PRESENT
 	if sys.Token != 0 {
-		err = CreateProcessAsUser(sys.Token, argv0p, argvp, sys.ProcessAttributes, sys.ThreadAttributes, !sys.NoInheritHandles, flags, createEnvBlock(attr.Env), dirp, &si.StartupInfo, pi)
+		err = CreateProcessAsUser(sys.Token, argv0p, argvp, sys.ProcessAttributes, sys.ThreadAttributes, len(fd) > 0 && !sys.NoInheritHandles, flags, createEnvBlock(attr.Env), dirp, &si.StartupInfo, pi)
 	} else {
-		err = CreateProcess(argv0p, argvp, sys.ProcessAttributes, sys.ThreadAttributes, !sys.NoInheritHandles, flags, createEnvBlock(attr.Env), dirp, &si.StartupInfo, pi)
+		err = CreateProcess(argv0p, argvp, sys.ProcessAttributes, sys.ThreadAttributes, len(fd) > 0 && !sys.NoInheritHandles, flags, createEnvBlock(attr.Env), dirp, &si.StartupInfo, pi)
 	}
 	if err != nil {
 		return 0, 0, err