mirror of https://github.com/tailscale/tailscale/
util/winutil: add conpty package and helper for building windows.StartupInfoEx
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>icio/tsweb-nested-stdhandler
Aaron Klotz
2 weeks ago
parent
8a11a43c28
commit
34e8820301
@ -0,0 +1,134 @@
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// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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// Package conpty implements support for Windows pseudo-consoles.
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package conpty
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import (
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"errors"
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"fmt"
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"io"
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"os"
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"github.com/dblohm7/wingoes"
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"golang.org/x/sys/windows"
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"tailscale.com/util/winutil"
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)
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var (
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// ErrUnsupported is returned by NewPseudoConsole if the current Windows
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// build does not support this package's API.
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ErrUnsupported = errors.New("conpty unsupported on this version of Windows")
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)
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// PseudoConsole encapsulates a Windows pseudo-console. Use NewPseudoConsole
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// to create a new instance.
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type PseudoConsole struct {
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outputRead io.ReadCloser
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inputWrite io.WriteCloser
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console windows.Handle
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}
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// NewPseudoConsole creates a new PseudoConsole using size for its initial
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// width and height. It requires Windows 10 1809 or newer, and will return
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// ErrUnsupported if that requirement is not met.
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func NewPseudoConsole(size windows.Coord) (pty *PseudoConsole, err error) {
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if !wingoes.IsWin10BuildOrGreater(wingoes.Win10Build1809) {
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return nil, ErrUnsupported
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}
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if size.X <= 0 || size.Y <= 0 {
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return nil, fmt.Errorf("%w: size must contain positive values", os.ErrInvalid)
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}
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var inputRead, inputWrite windows.Handle
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if err := windows.CreatePipe(&inputRead, &inputWrite, nil, 0); err != nil {
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return nil, err
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}
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defer func() {
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windows.CloseHandle(inputRead)
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if err != nil {
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windows.CloseHandle(inputWrite)
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}
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}()
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var outputRead, outputWrite windows.Handle
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if err := windows.CreatePipe(&outputRead, &outputWrite, nil, 0); err != nil {
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return nil, err
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}
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defer func() {
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windows.CloseHandle(outputWrite)
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if err != nil {
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windows.CloseHandle(outputRead)
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}
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}()
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var console windows.Handle
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if err := windows.CreatePseudoConsole(size, inputRead, outputWrite, 0, &console); err != nil {
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return nil, err
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}
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pty = &PseudoConsole{
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outputRead: os.NewFile(uintptr(outputRead), "ptyOutputRead"),
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inputWrite: os.NewFile(uintptr(inputWrite), "ptyInputWrite"),
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console: console,
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}
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return pty, nil
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}
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// Resize sets the width and height of pty to size.
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func (pty *PseudoConsole) Resize(size windows.Coord) error {
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if pty.console == 0 {
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return fmt.Errorf("PseudoConsole is closed")
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}
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if size.X <= 0 || size.Y <= 0 {
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return fmt.Errorf("%w: size must contain positive values", os.ErrInvalid)
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}
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return windows.ResizePseudoConsole(pty.console, size)
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}
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// Close shuts down the pty. The caller must continue reading from the
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// ReadCloser returned by Output until either EOF is reached or Close returns;
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// failure to adequately drain the ReadCloser may result in Close deadlocking.
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func (pty *PseudoConsole) Close() error {
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if pty.console != 0 {
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windows.ClosePseudoConsole(pty.console)
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pty.console = 0
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}
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// now we can stop these
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if pty.outputRead != nil {
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pty.outputRead.Close()
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pty.outputRead = nil
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}
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if pty.inputWrite != nil {
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pty.inputWrite.Close()
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pty.inputWrite = nil
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}
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return nil
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}
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// ConfigureStartupInfo associates pty with the process to be started using sib.
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func (pty *PseudoConsole) ConfigureStartupInfo(sib *winutil.StartupInfoBuilder) error {
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if sib == nil {
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return os.ErrInvalid
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}
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// We need to explicitly set null std handles.
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// Failure to do so causes interference between the pty and the console
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// handles that are implicitly inherited from the parent.
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// This isn't explicitly documented anywhere. Windows Terminal does this too.
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if err := sib.SetStdHandles(0, 0, 0); err != nil {
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return err
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}
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return sib.SetPseudoConsole(pty.console)
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}
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// OutputPipe returns the ReadCloser for reading pty's output.
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func (pty *PseudoConsole) OutputPipe() io.ReadCloser {
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return pty.outputRead
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}
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// InputPipe returns the WriteCloser for writing pty's output.
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func (pty *PseudoConsole) InputPipe() io.WriteCloser {
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return pty.inputWrite
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}
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@ -0,0 +1,317 @@
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// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package winutil
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import (
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"errors"
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"fmt"
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"os"
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"slices"
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"unsafe"
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"github.com/dblohm7/wingoes"
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"golang.org/x/sys/windows"
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)
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var (
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// ErrAlreadyResolved is returned by (*StartupInfoBuilder).Resolve when the
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// StartupInfoBuilder has already been resolved.
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ErrAlreadyResolved = errors.New("StartupInfo already resolved")
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// ErrAlreadySet is returned by StartupInfoBuilder setters if the value
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// has already been set.
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ErrAlreadySet = errors.New("StartupInfoBuilder value already set")
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// ErrTooManyMitigationPolicyArguments is returned by
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// (*StartupInfoBuilder).AddMitigationPolicyFlags if more arguments are
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// passed than are supported by the current version of Windows. This error
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// may be wrapped with additional information, so use [errors.Is] to check for it.
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ErrTooManyMitigationPolicyArguments = errors.New("too many mitigation policy arguments for current Windows version")
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)
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// Attribute IDs not yet present in x/sys/windows
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const (
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_PROC_THREAD_ATTRIBUTE_JOB_LIST = 0x0002000D
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)
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// Mitigation flags from the Win32 SDK
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const (
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PROCESS_CREATION_MITIGATION_POLICY_IMAGE_LOAD_NO_REMOTE_ALWAYS_ON = (1 << 52)
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PROCESS_CREATION_MITIGATION_POLICY_IMAGE_LOAD_NO_LOW_LABEL_ALWAYS_ON = (1 << 56)
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PROCESS_CREATION_MITIGATION_POLICY_IMAGE_LOAD_PREFER_SYSTEM32_ALWAYS_ON = (1 << 60)
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)
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// StartupInfoBuilder constructs a Windows STARTUPINFOEX and optional
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// process/thread attribute list for use with the CreateProcess family of APIs.
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type StartupInfoBuilder struct {
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siex windows.StartupInfoEx
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attrs map[uintptr]any // attr -> value
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attrContainer *windows.ProcThreadAttributeListContainer
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}
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func (sib *StartupInfoBuilder) Close() error {
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si := &sib.siex.StartupInfo
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if (si.Flags & windows.STARTF_USESTDHANDLES) != 0 {
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for _, h := range []windows.Handle{si.StdInput, si.StdOutput, si.StdErr} {
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if canBeInherited(h) {
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windows.CloseHandle(h)
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}
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}
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}
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sib.siex = windows.StartupInfoEx{}
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if sib.attrContainer != nil {
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sib.attrContainer.Delete()
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sib.attrContainer = nil
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}
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sib.attrs = nil
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return nil
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}
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// Resolve causes all settings and attributes stored within sib to be processed
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// and formatted into valid arguments for use by CreateProcess* APIs.
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// The returned values will not be altered any further by sib, so the caller
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// is free to make additional customizations to the returned values prior to
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// passing them into CreateProcess.
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func (sib *StartupInfoBuilder) Resolve() (startupInfo *windows.StartupInfo, inheritHandles bool, createProcessFlags uint32, err error) {
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if sib.siex.StartupInfo.Cb != 0 {
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return nil, false, 0, ErrAlreadyResolved
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}
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// Always create a Unicode environment.
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createProcessFlags = windows.CREATE_UNICODE_ENVIRONMENT
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if l := uint32(len(sib.attrs)); l > 0 {
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attrCont, err := windows.NewProcThreadAttributeList(l)
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if err != nil {
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return nil, false, 0, err
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}
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defer func() {
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if err != nil {
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attrCont.Delete()
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}
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}()
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for attr, val := range sib.attrs {
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var pval unsafe.Pointer
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var sval uintptr
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switch v := val.(type) {
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case windows.Handle:
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// An individual handle is pointer-width and is thus passed by value.
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pval = unsafe.Pointer(v)
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sval = unsafe.Sizeof(v)
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case []uint64:
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pval = unsafe.Pointer(unsafe.SliceData(v))
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sval = unsafe.Sizeof(v[0]) * uintptr(len(v))
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case []windows.Handle:
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pval = unsafe.Pointer(unsafe.SliceData(v))
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sval = unsafe.Sizeof(v[0]) * uintptr(len(v))
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default:
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panic("unsupported data type")
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}
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// Note that pointer keepalives are managed by attrCont.
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if err := attrCont.Update(attr, pval, sval); err != nil {
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return nil, false, 0, err
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}
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if attr == windows.PROC_THREAD_ATTRIBUTE_HANDLE_LIST {
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inheritHandles = true
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}
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}
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sib.attrContainer = attrCont
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sib.siex.ProcThreadAttributeList = attrCont.List()
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sib.siex.StartupInfo.Cb = uint32(unsafe.Sizeof(sib.siex))
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createProcessFlags |= windows.EXTENDED_STARTUPINFO_PRESENT
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} else {
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sib.siex.StartupInfo.Cb = uint32(unsafe.Sizeof(sib.siex.StartupInfo))
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}
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return &sib.siex.StartupInfo, inheritHandles, createProcessFlags, nil
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}
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func canBeInherited(h windows.Handle) bool {
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if h == 0 || h == windows.InvalidHandle {
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return false
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}
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ft, _ := windows.GetFileType(h)
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switch ft {
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case windows.FILE_TYPE_DISK, windows.FILE_TYPE_PIPE:
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return true
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case windows.FILE_TYPE_CHAR:
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// Console handles are treated differently from other character devices.
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// In particular, they should not be set up to be inherited like other
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// kernel handles. We determine whether h is a console handle by attempting
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// to retrieve its console mode. If this call fails then h is not a console.
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var mode uint32
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return windows.GetConsoleMode(h, &mode) != nil
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default:
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return false
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}
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}
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// SetStdHandles sets the StdInput, StdOutput, and StdErr handles and configures
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// their inheritability as needed. When the handles are valid, non-console
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// kernel objects, sib takes ownership of of them. All three handles may be set
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// to zero to indicate that the parent's std handles should not be implicitly
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// inherited.
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//
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// It returns ErrAlreadySet if the handles have already been set by a previous call.
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func (sib *StartupInfoBuilder) SetStdHandles(stdin, stdout, stderr windows.Handle) error {
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if (sib.siex.StartupInfo.Flags & windows.STARTF_USESTDHANDLES) != 0 {
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return ErrAlreadySet
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}
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toInherit := make([]windows.Handle, 0, 3)
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for _, h := range []windows.Handle{stdin, stdout, stderr} {
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if !canBeInherited(h) {
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continue
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}
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toInherit = append(toInherit, h)
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}
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if err := sib.InheritHandles(toInherit...); err != nil {
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return err
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}
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sib.siex.StartupInfo.Flags |= windows.STARTF_USESTDHANDLES
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sib.siex.StartupInfo.StdInput = stdin
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sib.siex.StartupInfo.StdOutput = stdout
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sib.siex.StartupInfo.StdErr = stderr
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return nil
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}
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func (sib *StartupInfoBuilder) makeAttrs() {
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if sib.attrs == nil {
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// The size of this map should correspond to the number of distinct
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// attribute values supported by the StartupInfoBuilder API. Currently
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// we support four:
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// * Inheritable handle list;
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// * Pseudoconsole;
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// * Mitigation policy;
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// * Job list
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sib.attrs = make(map[uintptr]any, 4)
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}
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}
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func (sib *StartupInfoBuilder) getAttr(attr uintptr) any {
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sib.makeAttrs()
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return sib.attrs[attr]
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}
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// InheritHandles configures each handle in handles to be inheritable and adds
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// it to the inheritable handle list proc/thread attribute. handles must consist
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// entirely of kernel objects (handles that are closed via windows.CloseHandle).
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// InheritHandles may be called multiple times; each successive call accumulates
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// handles into an internal list maintained by sib.
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func (sib *StartupInfoBuilder) InheritHandles(handles ...windows.Handle) error {
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if len(handles) == 0 {
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return nil
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}
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newHandles := make([]windows.Handle, 0, len(handles))
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for _, h := range handles {
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if h == 0 || h == windows.InvalidHandle || slices.Contains(newHandles, h) {
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continue
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}
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if err := windows.SetHandleInformation(h, windows.HANDLE_FLAG_INHERIT, windows.HANDLE_FLAG_INHERIT); err != nil {
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return err
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}
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newHandles = append(newHandles, h)
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}
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if len(newHandles) == 0 {
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return nil
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}
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var handleList []windows.Handle
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if attrv := sib.getAttr(windows.PROC_THREAD_ATTRIBUTE_HANDLE_LIST); attrv != nil {
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handleList = attrv.([]windows.Handle)
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}
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sib.attrs[windows.PROC_THREAD_ATTRIBUTE_HANDLE_LIST] = append(handleList, newHandles...)
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return nil
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}
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// AddMitigationPolicyFlags sets the process mitigation policy flags in newFlags
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// on the mitigation policy proc/thread attribute. It accepts a different
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// number of arguments depending on the current Windows version. If the
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// current Windows version is Windows 10 build 1703 or newer, it accepts up to
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// two arguments. It only accepts one argument on older versions of Windows 10.
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// If too many arguments are supplied, AddMitigationPolicyFlags returns
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// ErrTooManyMitigationPolicyArguments wrapped with additional information;
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// use errors.Is to check for this error.
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// AddMitigationPolicyFlags may be called multiple times; each successive call
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// accumulates additional flags into the mitigation policy.
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func (sib *StartupInfoBuilder) AddMitigationPolicyFlags(newFlags ...uint64) error {
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if len(newFlags) == 0 {
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return nil
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}
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supportedLen := 1
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if wingoes.IsWin10BuildOrGreater(wingoes.Win10Build1703) {
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supportedLen++
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}
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if len(newFlags) > supportedLen {
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return fmt.Errorf("%w: no more than %d allowed", ErrTooManyMitigationPolicyArguments, supportedLen)
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}
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attrv := sib.getAttr(windows.PROC_THREAD_ATTRIBUTE_MITIGATION_POLICY)
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switch v := attrv.(type) {
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case nil:
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sib.attrs[windows.PROC_THREAD_ATTRIBUTE_MITIGATION_POLICY] = newFlags
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case []uint64:
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if newElems := len(newFlags) - len(v); newElems > 0 {
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v = append(v, make([]uint64, newElems)...)
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sib.attrs[windows.PROC_THREAD_ATTRIBUTE_MITIGATION_POLICY] = v
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}
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for i := range v {
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v[i] |= newFlags[i]
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}
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default:
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panic("unexpected attribute type")
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}
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return nil
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}
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// SetPseudoConsole sets pty as the pseudoconsole proc/thread attribute.
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// pty must be a conpty handle. It returns ErrAlreadySet if the pty has already
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// been successfully set by a previous call.
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func (sib *StartupInfoBuilder) SetPseudoConsole(pty windows.Handle) error {
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if pty == 0 {
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return os.ErrInvalid
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}
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if attrv := sib.getAttr(windows.PROC_THREAD_ATTRIBUTE_PSEUDOCONSOLE); attrv != nil {
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return ErrAlreadySet
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}
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sib.attrs[windows.PROC_THREAD_ATTRIBUTE_PSEUDOCONSOLE] = pty
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return nil
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}
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// AssignToJob assigns the process created by sib to job. AssignToJob may be
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// called multiple times to assign the process to multiple jobs.
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func (sib *StartupInfoBuilder) AssignToJob(job windows.Handle) error {
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if job == 0 {
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return os.ErrInvalid
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}
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var jobList []windows.Handle
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if attrv := sib.getAttr(_PROC_THREAD_ATTRIBUTE_JOB_LIST); attrv != nil {
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jobList = attrv.([]windows.Handle)
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}
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if slices.Contains(jobList, job) {
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return nil
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}
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sib.attrs[_PROC_THREAD_ATTRIBUTE_JOB_LIST] = append(jobList, job)
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return nil
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}
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