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util/winutil: add conpty package and helper for building windows.StartupInfoEx

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StartupInfoBuilder is a helper for constructing StartupInfoEx structures
featuring proc/thread attribute lists. Calling its setters triggers the
appropriate setting of fields, adjusting flags as necessary, and populating
the proc/thread attribute list as necessary. Currently it supports four
features: setting std handles, setting pseudo-consoles, specifying handles
for inheritance, and specifying jobs.

The conpty package simplifies creation of pseudo-consoles, their associated
pipes, and assignment of the pty to StartupInfoEx proc/thread attributes.

Updates #12383

Signed-off-by: Aaron Klotz <aaron@tailscale.com>
pull/12389/head
Aaron Klotz 6 months ago
parent 8a11a43c28
commit 34e8820301
2 changed files with 451 additions and 0 deletions
Show Stats Download Patch File Download Diff File

134
util/winutil/conpty/conpty_windows.go
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// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
// Package conpty implements support for Windows pseudo-consoles.
package conpty
import (
"errors"
"fmt"
"io"
"os"
"github.com/dblohm7/wingoes"
"golang.org/x/sys/windows"
"tailscale.com/util/winutil"
)
var (
// ErrUnsupported is returned by NewPseudoConsole if the current Windows
// build does not support this package's API.
ErrUnsupported = errors.New("conpty unsupported on this version of Windows")
)
// PseudoConsole encapsulates a Windows pseudo-console. Use NewPseudoConsole
// to create a new instance.
type PseudoConsole struct {
outputRead io.ReadCloser
inputWrite io.WriteCloser
console windows.Handle
}
// NewPseudoConsole creates a new PseudoConsole using size for its initial
// width and height. It requires Windows 10 1809 or newer, and will return
// ErrUnsupported if that requirement is not met.
func NewPseudoConsole(size windows.Coord) (pty *PseudoConsole, err error) {
if !wingoes.IsWin10BuildOrGreater(wingoes.Win10Build1809) {
return nil, ErrUnsupported
}
if size.X <= 0 || size.Y <= 0 {
return nil, fmt.Errorf("%w: size must contain positive values", os.ErrInvalid)
}
var inputRead, inputWrite windows.Handle
if err := windows.CreatePipe(&inputRead, &inputWrite, nil, 0); err != nil {
return nil, err
}
defer func() {
windows.CloseHandle(inputRead)
if err != nil {
windows.CloseHandle(inputWrite)
}
}()
var outputRead, outputWrite windows.Handle
if err := windows.CreatePipe(&outputRead, &outputWrite, nil, 0); err != nil {
return nil, err
}
defer func() {
windows.CloseHandle(outputWrite)
if err != nil {
windows.CloseHandle(outputRead)
}
}()
var console windows.Handle
if err := windows.CreatePseudoConsole(size, inputRead, outputWrite, 0, &console); err != nil {
return nil, err
}
pty = &PseudoConsole{
outputRead: os.NewFile(uintptr(outputRead), "ptyOutputRead"),
inputWrite: os.NewFile(uintptr(inputWrite), "ptyInputWrite"),
console: console,
}
return pty, nil
}
// Resize sets the width and height of pty to size.
func (pty *PseudoConsole) Resize(size windows.Coord) error {
if pty.console == 0 {
return fmt.Errorf("PseudoConsole is closed")
}
if size.X <= 0 || size.Y <= 0 {
return fmt.Errorf("%w: size must contain positive values", os.ErrInvalid)
}
return windows.ResizePseudoConsole(pty.console, size)
}
// Close shuts down the pty. The caller must continue reading from the
// ReadCloser returned by Output until either EOF is reached or Close returns;
// failure to adequately drain the ReadCloser may result in Close deadlocking.
func (pty *PseudoConsole) Close() error {
if pty.console != 0 {
windows.ClosePseudoConsole(pty.console)
pty.console = 0
}
// now we can stop these
if pty.outputRead != nil {
pty.outputRead.Close()
pty.outputRead = nil
}
if pty.inputWrite != nil {
pty.inputWrite.Close()
pty.inputWrite = nil
}
return nil
}
// ConfigureStartupInfo associates pty with the process to be started using sib.
func (pty *PseudoConsole) ConfigureStartupInfo(sib *winutil.StartupInfoBuilder) error {
if sib == nil {
return os.ErrInvalid
}
// We need to explicitly set null std handles.
// Failure to do so causes interference between the pty and the console
// handles that are implicitly inherited from the parent.
// This isn't explicitly documented anywhere. Windows Terminal does this too.
if err := sib.SetStdHandles(0, 0, 0); err != nil {
return err
}
return sib.SetPseudoConsole(pty.console)
}
// OutputPipe returns the ReadCloser for reading pty's output.
func (pty *PseudoConsole) OutputPipe() io.ReadCloser {
return pty.outputRead
}
// InputPipe returns the WriteCloser for writing pty's output.
func (pty *PseudoConsole) InputPipe() io.WriteCloser {
return pty.inputWrite
}

317
util/winutil/startupinfo_windows.go
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// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
package winutil
import (
"errors"
"fmt"
"os"
"slices"
"unsafe"
"github.com/dblohm7/wingoes"
"golang.org/x/sys/windows"
)
var (
// ErrAlreadyResolved is returned by (*StartupInfoBuilder).Resolve when the
// StartupInfoBuilder has already been resolved.
ErrAlreadyResolved = errors.New("StartupInfo already resolved")
// ErrAlreadySet is returned by StartupInfoBuilder setters if the value
// has already been set.
ErrAlreadySet = errors.New("StartupInfoBuilder value already set")
// ErrTooManyMitigationPolicyArguments is returned by
// (*StartupInfoBuilder).AddMitigationPolicyFlags if more arguments are
// passed than are supported by the current version of Windows. This error
// may be wrapped with additional information, so use [errors.Is] to check for it.
ErrTooManyMitigationPolicyArguments = errors.New("too many mitigation policy arguments for current Windows version")
)
// Attribute IDs not yet present in x/sys/windows
const (
_PROC_THREAD_ATTRIBUTE_JOB_LIST = 0x0002000D
)
// Mitigation flags from the Win32 SDK
const (
PROCESS_CREATION_MITIGATION_POLICY_IMAGE_LOAD_NO_REMOTE_ALWAYS_ON = (1 << 52)
PROCESS_CREATION_MITIGATION_POLICY_IMAGE_LOAD_NO_LOW_LABEL_ALWAYS_ON = (1 << 56)
PROCESS_CREATION_MITIGATION_POLICY_IMAGE_LOAD_PREFER_SYSTEM32_ALWAYS_ON = (1 << 60)
)
// StartupInfoBuilder constructs a Windows STARTUPINFOEX and optional
// process/thread attribute list for use with the CreateProcess family of APIs.
type StartupInfoBuilder struct {
siex windows.StartupInfoEx
attrs map[uintptr]any // attr -> value
attrContainer *windows.ProcThreadAttributeListContainer
}
func (sib *StartupInfoBuilder) Close() error {
si := &sib.siex.StartupInfo
if (si.Flags & windows.STARTF_USESTDHANDLES) != 0 {
for _, h := range []windows.Handle{si.StdInput, si.StdOutput, si.StdErr} {
if canBeInherited(h) {
windows.CloseHandle(h)
}
}
}
sib.siex = windows.StartupInfoEx{}
if sib.attrContainer != nil {
sib.attrContainer.Delete()
sib.attrContainer = nil
}
sib.attrs = nil
return nil
}
// Resolve causes all settings and attributes stored within sib to be processed
// and formatted into valid arguments for use by CreateProcess* APIs.
// The returned values will not be altered any further by sib, so the caller
// is free to make additional customizations to the returned values prior to
// passing them into CreateProcess.
func (sib *StartupInfoBuilder) Resolve() (startupInfo *windows.StartupInfo, inheritHandles bool, createProcessFlags uint32, err error) {
if sib.siex.StartupInfo.Cb != 0 {
return nil, false, 0, ErrAlreadyResolved
}
// Always create a Unicode environment.
createProcessFlags = windows.CREATE_UNICODE_ENVIRONMENT
if l := uint32(len(sib.attrs)); l > 0 {
attrCont, err := windows.NewProcThreadAttributeList(l)
if err != nil {
return nil, false, 0, err
}
defer func() {
if err != nil {
attrCont.Delete()
}
}()
for attr, val := range sib.attrs {
var pval unsafe.Pointer
var sval uintptr
switch v := val.(type) {
case windows.Handle:
// An individual handle is pointer-width and is thus passed by value.
pval = unsafe.Pointer(v)
sval = unsafe.Sizeof(v)
case []uint64:
pval = unsafe.Pointer(unsafe.SliceData(v))
sval = unsafe.Sizeof(v[0]) * uintptr(len(v))
case []windows.Handle:
pval = unsafe.Pointer(unsafe.SliceData(v))
sval = unsafe.Sizeof(v[0]) * uintptr(len(v))
default:
panic("unsupported data type")
}
// Note that pointer keepalives are managed by attrCont.
if err := attrCont.Update(attr, pval, sval); err != nil {
return nil, false, 0, err
}
if attr == windows.PROC_THREAD_ATTRIBUTE_HANDLE_LIST {
inheritHandles = true
}
}
sib.attrContainer = attrCont
sib.siex.ProcThreadAttributeList = attrCont.List()
sib.siex.StartupInfo.Cb = uint32(unsafe.Sizeof(sib.siex))
createProcessFlags |= windows.EXTENDED_STARTUPINFO_PRESENT
} else {
sib.siex.StartupInfo.Cb = uint32(unsafe.Sizeof(sib.siex.StartupInfo))
}
return &sib.siex.StartupInfo, inheritHandles, createProcessFlags, nil
}
func canBeInherited(h windows.Handle) bool {
if h == 0 || h == windows.InvalidHandle {
return false
}
ft, _ := windows.GetFileType(h)
switch ft {
case windows.FILE_TYPE_DISK, windows.FILE_TYPE_PIPE:
return true
case windows.FILE_TYPE_CHAR:
// Console handles are treated differently from other character devices.
// In particular, they should not be set up to be inherited like other
// kernel handles. We determine whether h is a console handle by attempting
// to retrieve its console mode. If this call fails then h is not a console.
var mode uint32
return windows.GetConsoleMode(h, &mode) != nil
default:
return false
}
}
// SetStdHandles sets the StdInput, StdOutput, and StdErr handles and configures
// their inheritability as needed. When the handles are valid, non-console
// kernel objects, sib takes ownership of of them. All three handles may be set
// to zero to indicate that the parent's std handles should not be implicitly
// inherited.
//
// It returns ErrAlreadySet if the handles have already been set by a previous call.
func (sib *StartupInfoBuilder) SetStdHandles(stdin, stdout, stderr windows.Handle) error {
if (sib.siex.StartupInfo.Flags & windows.STARTF_USESTDHANDLES) != 0 {
return ErrAlreadySet
}
toInherit := make([]windows.Handle, 0, 3)
for _, h := range []windows.Handle{stdin, stdout, stderr} {
if !canBeInherited(h) {
continue
}
toInherit = append(toInherit, h)
}
if err := sib.InheritHandles(toInherit...); err != nil {
return err
}
sib.siex.StartupInfo.Flags |= windows.STARTF_USESTDHANDLES
sib.siex.StartupInfo.StdInput = stdin
sib.siex.StartupInfo.StdOutput = stdout
sib.siex.StartupInfo.StdErr = stderr
return nil
}
func (sib *StartupInfoBuilder) makeAttrs() {
if sib.attrs == nil {
// The size of this map should correspond to the number of distinct
// attribute values supported by the StartupInfoBuilder API. Currently
// we support four:
// * Inheritable handle list;
// * Pseudoconsole;
// * Mitigation policy;
// * Job list
sib.attrs = make(map[uintptr]any, 4)
}
}
func (sib *StartupInfoBuilder) getAttr(attr uintptr) any {
sib.makeAttrs()
return sib.attrs[attr]
}
// InheritHandles configures each handle in handles to be inheritable and adds
// it to the inheritable handle list proc/thread attribute. handles must consist
// entirely of kernel objects (handles that are closed via windows.CloseHandle).
// InheritHandles may be called multiple times; each successive call accumulates
// handles into an internal list maintained by sib.
func (sib *StartupInfoBuilder) InheritHandles(handles ...windows.Handle) error {
if len(handles) == 0 {
return nil
}
newHandles := make([]windows.Handle, 0, len(handles))
for _, h := range handles {
if h == 0 || h == windows.InvalidHandle || slices.Contains(newHandles, h) {
continue
}
if err := windows.SetHandleInformation(h, windows.HANDLE_FLAG_INHERIT, windows.HANDLE_FLAG_INHERIT); err != nil {
return err
}
newHandles = append(newHandles, h)
}
if len(newHandles) == 0 {
return nil
}
var handleList []windows.Handle
if attrv := sib.getAttr(windows.PROC_THREAD_ATTRIBUTE_HANDLE_LIST); attrv != nil {
handleList = attrv.([]windows.Handle)
}
sib.attrs[windows.PROC_THREAD_ATTRIBUTE_HANDLE_LIST] = append(handleList, newHandles...)
return nil
}
// AddMitigationPolicyFlags sets the process mitigation policy flags in newFlags
// on the mitigation policy proc/thread attribute. It accepts a different
// number of arguments depending on the current Windows version. If the
// current Windows version is Windows 10 build 1703 or newer, it accepts up to
// two arguments. It only accepts one argument on older versions of Windows 10.
// If too many arguments are supplied, AddMitigationPolicyFlags returns
// ErrTooManyMitigationPolicyArguments wrapped with additional information;
// use errors.Is to check for this error.
// AddMitigationPolicyFlags may be called multiple times; each successive call
// accumulates additional flags into the mitigation policy.
func (sib *StartupInfoBuilder) AddMitigationPolicyFlags(newFlags ...uint64) error {
if len(newFlags) == 0 {
return nil
}
supportedLen := 1
if wingoes.IsWin10BuildOrGreater(wingoes.Win10Build1703) {
supportedLen++
}
if len(newFlags) > supportedLen {
return fmt.Errorf("%w: no more than %d allowed", ErrTooManyMitigationPolicyArguments, supportedLen)
}
attrv := sib.getAttr(windows.PROC_THREAD_ATTRIBUTE_MITIGATION_POLICY)
switch v := attrv.(type) {
case nil:
sib.attrs[windows.PROC_THREAD_ATTRIBUTE_MITIGATION_POLICY] = newFlags
case []uint64:
if newElems := len(newFlags) - len(v); newElems > 0 {
v = append(v, make([]uint64, newElems)...)
sib.attrs[windows.PROC_THREAD_ATTRIBUTE_MITIGATION_POLICY] = v
}
for i := range v {
v[i] |= newFlags[i]
}
default:
panic("unexpected attribute type")
}
return nil
}
// SetPseudoConsole sets pty as the pseudoconsole proc/thread attribute.
// pty must be a conpty handle. It returns ErrAlreadySet if the pty has already
// been successfully set by a previous call.
func (sib *StartupInfoBuilder) SetPseudoConsole(pty windows.Handle) error {
if pty == 0 {
return os.ErrInvalid
}
if attrv := sib.getAttr(windows.PROC_THREAD_ATTRIBUTE_PSEUDOCONSOLE); attrv != nil {
return ErrAlreadySet
}
sib.attrs[windows.PROC_THREAD_ATTRIBUTE_PSEUDOCONSOLE] = pty
return nil
}
// AssignToJob assigns the process created by sib to job. AssignToJob may be
// called multiple times to assign the process to multiple jobs.
func (sib *StartupInfoBuilder) AssignToJob(job windows.Handle) error {
if job == 0 {
return os.ErrInvalid
}
var jobList []windows.Handle
if attrv := sib.getAttr(_PROC_THREAD_ATTRIBUTE_JOB_LIST); attrv != nil {
jobList = attrv.([]windows.Handle)
}
if slices.Contains(jobList, job) {
return nil
}
sib.attrs[_PROC_THREAD_ATTRIBUTE_JOB_LIST] = append(jobList, job)
return nil
}
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