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os/exec: on Windows, suppress ErrDot if the implicit path matches the explicit one

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If the current directory is also listed explicitly in %PATH%,
this changes the behavior of LookPath to prefer the explicit name for it
(and thereby avoid ErrDot).

However, in order to avoid running a different executable from what
would have been run by previous Go versions, we still return the
implicit path (and ErrDot) if it refers to a different file entirely.

Fixes #53536.
Updates #43724.

Change-Id: I7ab01074e21a0e8b07a176e3bc6d3b8cf0c873cd
Reviewed-on: https://go-review.googlesource.com/c/go/+/414054
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Bryan C. Mills 2022-06-24 15:36:25 -04:00 committed by Bryan Mills
parent 34f3ac5f16
commit 3580ef9d64
2 changed files with 116 additions and 7 deletions
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98
src/os/exec/dot_test.go
View File

@ -15,6 +15,13 @@ import (
"testing"
)
var pathVar string = func() string {
if runtime.GOOS == "plan9" {
return "path"
}
return "PATH"
}()
func TestLookPath(t *testing.T) {
testenv.MustHaveExec(t)
@ -42,22 +49,24 @@ func TestLookPath(t *testing.T) {
if err = os.Chdir(tmpDir); err != nil {
t.Fatal(err)
}
origPath := os.Getenv("PATH")
defer os.Setenv("PATH", origPath)
t.Setenv("PWD", tmpDir)
t.Logf(". is %#q", tmpDir)
origPath := os.Getenv(pathVar)
// Add "." to PATH so that exec.LookPath looks in the current directory on all systems.
// And try to trick it with "../testdir" too.
for _, dir := range []string{".", "../testdir"} {
os.Setenv("PATH", dir+string(filepath.ListSeparator)+origPath)
t.Run("PATH="+dir, func(t *testing.T) {
t.Run(pathVar+"="+dir, func(t *testing.T) {
t.Setenv(pathVar, dir+string(filepath.ListSeparator)+origPath)
good := dir + "/execabs-test"
if found, err := LookPath(good); err != nil || !strings.HasPrefix(found, good) {
t.Fatalf("LookPath(%q) = %q, %v, want \"%s...\", nil", good, found, err, good)
t.Fatalf(`LookPath(%#q) = %#q, %v, want "%s...", nil`, good, found, err, good)
}
if runtime.GOOS == "windows" {
good = dir + `\execabs-test`
if found, err := LookPath(good); err != nil || !strings.HasPrefix(found, good) {
t.Fatalf("LookPath(%q) = %q, %v, want \"%s...\", nil", good, found, err, good)
t.Fatalf(`LookPath(%#q) = %#q, %v, want "%s...", nil`, good, found, err, good)
}
}
@ -84,4 +93,81 @@ func TestLookPath(t *testing.T) {
}
})
}
// Test the behavior when the first entry in PATH is an absolute name for the
// current directory.
//
// On Windows, "." may or may not be implicitly included before the explicit
// %PATH%, depending on the process environment;
// see https://go.dev/issue/4394.
//
// If the relative entry from "." resolves to the same executable as what
// would be resolved from an absolute entry in %PATH% alone, LookPath should
// return the absolute version of the path instead of ErrDot.
// (See https://go.dev/issue/53536.)
//
// If PATH does not implicitly include "." (such as on Unix platforms, or on
// Windows configured with NoDefaultCurrentDirectoryInExePath), then this
// lookup should succeed regardless of the behavior for ".", so it may be
// useful to run as a control case even on those platforms.
t.Run(pathVar+"=$PWD", func(t *testing.T) {
t.Setenv(pathVar, tmpDir+string(filepath.ListSeparator)+origPath)
good := filepath.Join(tmpDir, "execabs-test")
if found, err := LookPath(good); err != nil || !strings.HasPrefix(found, good) {
t.Fatalf(`LookPath(%#q) = %#q, %v, want \"%s...\", nil`, good, found, err, good)
}
if found, err := LookPath("execabs-test"); err != nil || !strings.HasPrefix(found, good) {
t.Fatalf(`LookPath(%#q) = %#q, %v, want \"%s...\", nil`, "execabs-test", found, err, good)
}
cmd := Command("execabs-test")
if cmd.Err != nil {
t.Fatalf("Command(%#q).Err = %v; want nil", "execabs-test", cmd.Err)
}
})
t.Run(pathVar+"=$OTHER", func(t *testing.T) {
// Control case: if the lookup returns ErrDot when PATH is empty, then we
// know that PATH implicitly includes ".". If it does not, then we don't
// expect to see ErrDot at all in this test (because the path will be
// unambiguously absolute).
wantErrDot := false
t.Setenv(pathVar, "")
if found, err := LookPath("execabs-test"); errors.Is(err, ErrDot) {
wantErrDot = true
} else if err == nil {
t.Fatalf(`with PATH='', LookPath(%#q) = %#q; want non-nil error`, "execabs-test", found)
}
// Set PATH to include an explicit directory that contains a completely
// independent executable that happens to have the same name as an
// executable in ".". If "." is included implicitly, looking up the
// (unqualified) executable name will return ErrDot; otherwise, the
// executable in "." should have no effect and the lookup should
// unambiguously resolve to the directory in PATH.
dir := t.TempDir()
executable := "execabs-test"
if runtime.GOOS == "windows" {
executable += ".exe"
}
if err := os.WriteFile(filepath.Join(dir, executable), []byte{1, 2, 3}, 0777); err != nil {
t.Fatal(err)
}
t.Setenv(pathVar, dir+string(filepath.ListSeparator)+origPath)
found, err := LookPath("execabs-test")
if wantErrDot {
wantFound := filepath.Join(".", executable)
if found != wantFound || !errors.Is(err, ErrDot) {
t.Fatalf(`LookPath(%#q) = %#q, %v, want %#q, Is ErrDot`, "execabs-test", found, err, wantFound)
}
} else {
wantFound := filepath.Join(dir, executable)
if found != wantFound || err != nil {
t.Fatalf(`LookPath(%#q) = %#q, %v, want %#q, nil`, "execabs-test", found, err, wantFound)
}
}
})
}

25
src/os/exec/lp_windows.go
View File

@ -96,20 +96,43 @@ func LookPath(file string) (string, error) {
// have configured their environment this way!
// https://docs.microsoft.com/en-us/windows/win32/api/processenv/nf-processenv-needcurrentdirectoryforexepathw
// See also go.dev/issue/43947.
var (
dotf string
dotErr error
)
if _, found := syscall.Getenv("NoDefaultCurrentDirectoryInExePath"); !found {
if f, err := findExecutable(filepath.Join(".", file), exts); err == nil {
return f, &Error{file, ErrDot}
dotf, dotErr = f, &Error{file, ErrDot}
}
}
path := os.Getenv("path")
for _, dir := range filepath.SplitList(path) {
if f, err := findExecutable(filepath.Join(dir, file), exts); err == nil {
if dotErr != nil {
// https://go.dev/issue/53536: if we resolved a relative path implicitly,
// and it is the same executable that would be resolved from the explicit %PATH%,
// prefer the explicit name for the executable (and, likely, no error) instead
// of the equivalent implicit name with ErrDot.
//
// Otherwise, return the ErrDot for the implicit path as soon as we find
// out that the explicit one doesn't match.
dotfi, dotfiErr := os.Lstat(dotf)
fi, fiErr := os.Lstat(f)
if dotfiErr != nil || fiErr != nil || !os.SameFile(dotfi, fi) {
return dotf, dotErr
}
}
if !filepath.IsAbs(f) {
return f, &Error{file, ErrDot}
}
return f, nil
}
}
if dotErr != nil {
return dotf, dotErr
}
return "", &Error{file, ErrNotFound}
}