| // Copyright 2020 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // Package execabs is a drop-in replacement for os/exec |
| // that requires PATH lookups to find absolute paths. |
| // That is, execabs.Command("cmd") runs the same PATH lookup |
| // as exec.Command("cmd"), but if the result is a path |
| // which is relative, the Run and Start methods will report |
| // an error instead of running the executable. |
| // |
| // See https://blog.golang.org/path-security for more information |
| // about when it may be necessary or appropriate to use this package. |
| package execabs |
| |
| import ( |
| "context" |
| "fmt" |
| "os/exec" |
| "path/filepath" |
| "reflect" |
| "unsafe" |
| ) |
| |
| // ErrNotFound is the error resulting if a path search failed to find an executable file. |
| // It is an alias for exec.ErrNotFound. |
| var ErrNotFound = exec.ErrNotFound |
| |
| // Cmd represents an external command being prepared or run. |
| // It is an alias for exec.Cmd. |
| type Cmd = exec.Cmd |
| |
| // Error is returned by LookPath when it fails to classify a file as an executable. |
| // It is an alias for exec.Error. |
| type Error = exec.Error |
| |
| // An ExitError reports an unsuccessful exit by a command. |
| // It is an alias for exec.ExitError. |
| type ExitError = exec.ExitError |
| |
| func relError(file, path string) error { |
| return fmt.Errorf("%s resolves to executable in current directory (.%c%s)", file, filepath.Separator, path) |
| } |
| |
| // LookPath searches for an executable named file in the directories |
| // named by the PATH environment variable. If file contains a slash, |
| // it is tried directly and the PATH is not consulted. The result will be |
| // an absolute path. |
| // |
| // LookPath differs from exec.LookPath in its handling of PATH lookups, |
| // which are used for file names without slashes. If exec.LookPath's |
| // PATH lookup would have returned an executable from the current directory, |
| // LookPath instead returns an error. |
| func LookPath(file string) (string, error) { |
| path, err := exec.LookPath(file) |
| if err != nil && !isGo119ErrDot(err) { |
| return "", err |
| } |
| if filepath.Base(file) == file && !filepath.IsAbs(path) { |
| return "", relError(file, path) |
| } |
| return path, nil |
| } |
| |
| func fixCmd(name string, cmd *exec.Cmd) { |
| if filepath.Base(name) == name && !filepath.IsAbs(cmd.Path) && !isGo119ErrFieldSet(cmd) { |
| // exec.Command was called with a bare binary name and |
| // exec.LookPath returned a path which is not absolute. |
| // Set cmd.lookPathErr and clear cmd.Path so that it |
| // cannot be run. |
| lookPathErr := (*error)(unsafe.Pointer(reflect.ValueOf(cmd).Elem().FieldByName("lookPathErr").Addr().Pointer())) |
| if *lookPathErr == nil { |
| *lookPathErr = relError(name, cmd.Path) |
| } |
| cmd.Path = "" |
| } |
| } |
| |
| // CommandContext is like Command but includes a context. |
| // |
| // The provided context is used to kill the process (by calling os.Process.Kill) |
| // if the context becomes done before the command completes on its own. |
| func CommandContext(ctx context.Context, name string, arg ...string) *exec.Cmd { |
| cmd := exec.CommandContext(ctx, name, arg...) |
| fixCmd(name, cmd) |
| return cmd |
| |
| } |
| |
| // Command returns the Cmd struct to execute the named program with the given arguments. |
| // See exec.Command for most details. |
| // |
| // Command differs from exec.Command in its handling of PATH lookups, |
| // which are used when the program name contains no slashes. |
| // If exec.Command would have returned an exec.Cmd configured to run an |
| // executable from the current directory, Command instead |
| // returns an exec.Cmd that will return an error from Start or Run. |
| func Command(name string, arg ...string) *exec.Cmd { |
| cmd := exec.Command(name, arg...) |
| fixCmd(name, cmd) |
| return cmd |
| } |