os/exec: on Windows, suppress ErrDot if the implicit path matches the explicit one
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>
diff --git a/src/os/exec/dot_test.go b/src/os/exec/dot_test.go
index 932d907..e2d2dba 100644
--- a/src/os/exec/dot_test.go
+++ b/src/os/exec/dot_test.go
@@ -15,6 +15,13 @@
"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 @@
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 @@
}
})
}
+
+ // 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)
+ }
+ }
+ })
}
diff --git a/src/os/exec/lp_windows.go b/src/os/exec/lp_windows.go
index dab5770..da04758 100644
--- a/src/os/exec/lp_windows.go
+++ b/src/os/exec/lp_windows.go
@@ -96,20 +96,43 @@
// 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}
}
