2ac9968401
Go 1.15.7 contained a security fix for CVE-2021-3115, which allowed arbitrary code to be executed at build time when using cgo on Windows. This issue also affects Unix users who have “.” listed explicitly in their PATH and are running “go get” outside of a module or with module mode disabled. This issue is not limited to the go command itself, and can also affect binaries that use `os.Command`, `os.LookPath`, etc. From the related blogpost (ttps://blog.golang.org/path-security): > Are your own programs affected? > > If you use exec.LookPath or exec.Command in your own programs, you only need to > be concerned if you (or your users) run your program in a directory with untrusted > contents. If so, then a subprocess could be started using an executable from dot > instead of from a system directory. (Again, using an executable from dot happens > always on Windows and only with uncommon PATH settings on Unix.) > > If you are concerned, then we’ve published the more restricted variant of os/exec > as golang.org/x/sys/execabs. You can use it in your program by simply replacing This patch replaces all uses of `os/exec` with `golang.org/x/sys/execabs`. While some uses of `os/exec` should not be problematic (e.g. part of tests), it is probably good to be consistent, in case code gets moved around. Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
103 lines
3.5 KiB
Go
103 lines
3.5 KiB
Go
// Copyright 2020 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package execabs is a drop-in replacement for os/exec
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// that requires PATH lookups to find absolute paths.
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// That is, execabs.Command("cmd") runs the same PATH lookup
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// as exec.Command("cmd"), but if the result is a path
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// which is relative, the Run and Start methods will report
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// an error instead of running the executable.
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//
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// See https://blog.golang.org/path-security for more information
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// about when it may be necessary or appropriate to use this package.
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package execabs
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import (
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"context"
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"fmt"
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"os/exec"
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"path/filepath"
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"reflect"
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"unsafe"
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)
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// ErrNotFound is the error resulting if a path search failed to find an executable file.
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// It is an alias for exec.ErrNotFound.
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var ErrNotFound = exec.ErrNotFound
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// Cmd represents an external command being prepared or run.
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// It is an alias for exec.Cmd.
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type Cmd = exec.Cmd
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// Error is returned by LookPath when it fails to classify a file as an executable.
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// It is an alias for exec.Error.
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type Error = exec.Error
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// An ExitError reports an unsuccessful exit by a command.
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// It is an alias for exec.ExitError.
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type ExitError = exec.ExitError
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func relError(file, path string) error {
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return fmt.Errorf("%s resolves to executable in current directory (.%c%s)", file, filepath.Separator, path)
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}
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// LookPath searches for an executable named file in the directories
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// named by the PATH environment variable. If file contains a slash,
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// it is tried directly and the PATH is not consulted. The result will be
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// an absolute path.
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//
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// LookPath differs from exec.LookPath in its handling of PATH lookups,
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// which are used for file names without slashes. If exec.LookPath's
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// PATH lookup would have returned an executable from the current directory,
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// LookPath instead returns an error.
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func LookPath(file string) (string, error) {
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path, err := exec.LookPath(file)
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if err != nil {
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return "", err
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}
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if filepath.Base(file) == file && !filepath.IsAbs(path) {
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return "", relError(file, path)
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}
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return path, nil
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}
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func fixCmd(name string, cmd *exec.Cmd) {
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if filepath.Base(name) == name && !filepath.IsAbs(cmd.Path) {
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// exec.Command was called with a bare binary name and
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// exec.LookPath returned a path which is not absolute.
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// Set cmd.lookPathErr and clear cmd.Path so that it
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// cannot be run.
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lookPathErr := (*error)(unsafe.Pointer(reflect.ValueOf(cmd).Elem().FieldByName("lookPathErr").Addr().Pointer()))
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if *lookPathErr == nil {
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*lookPathErr = relError(name, cmd.Path)
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}
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cmd.Path = ""
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}
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}
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// CommandContext is like Command but includes a context.
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//
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// The provided context is used to kill the process (by calling os.Process.Kill)
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// if the context becomes done before the command completes on its own.
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func CommandContext(ctx context.Context, name string, arg ...string) *exec.Cmd {
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cmd := exec.CommandContext(ctx, name, arg...)
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fixCmd(name, cmd)
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return cmd
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}
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// Command returns the Cmd struct to execute the named program with the given arguments.
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// See exec.Command for most details.
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//
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// Command differs from exec.Command in its handling of PATH lookups,
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// which are used when the program name contains no slashes.
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// If exec.Command would have returned an exec.Cmd configured to run an
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// executable from the current directory, Command instead
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// returns an exec.Cmd that will return an error from Start or Run.
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func Command(name string, arg ...string) *exec.Cmd {
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cmd := exec.Command(name, arg...)
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fixCmd(name, cmd)
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return cmd
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}
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