cmd/go: respect group sticky bit on install.

When installing a package to a different directory using `go build`,
`mv` cannot be used if the destination directory has the group sticky
bit set.  Instead, `cp` should be used to make sure the destination
file has the correct permissions.

Fixes golang/go#18878.

Change-Id: I5423f559e7f84df080ed47816e19a22c6d00ab6d
Reviewed-on: https://go-review.googlesource.com/36797
Run-TryBot: Chris Manghane <cmang@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/cmd/go/internal/work/build.go b/src/cmd/go/internal/work/build.go
index a395176986d3c8d5633e85c0c6cc0610e774e58d..463206354beaaf23bc24834053ec3c51eddd7bd5 100644 (file)
--- a/src/cmd/go/internal/work/build.go
+++ b/src/cmd/go/internal/work/build.go
@@ -1655,6 +1655,15 @@ func (b *Builder) moveOrCopyFile(a *Action, dst, src string, perm os.FileMode, f
        // If we can update the mode and rename to the dst, do it.
        // Otherwise fall back to standard copy.
 
+       // If the destination directory has the group sticky bit set,
+       // we have to copy the file to retain the correct permissions.
+       // https://golang.org/issue/18878
+       if fi, err := os.Stat(filepath.Dir(dst)); err == nil {
+               if fi.IsDir() && (fi.Mode()&os.ModeSetgid) != 0 {
+                       return b.copyFile(a, dst, src, perm, force)
+               }
+       }
+
        // The perm argument is meant to be adjusted according to umask,
        // but we don't know what the umask is.
        // Create a dummy file to find out.

diff --git a/src/cmd/go/internal/work/build_test.go b/src/cmd/go/internal/work/build_test.go
index 9101ef1d1b4aa0c7cdf33f6de37bfeee93630756..2bfb6cb8145d7326729641f5c819018c5b21bc60 100644 (file)
--- a/src/cmd/go/internal/work/build_test.go
+++ b/src/cmd/go/internal/work/build_test.go
@@ -5,10 +5,15 @@
 package work
 
 import (
+       "bytes"
+       "fmt"
        "io/ioutil"
        "os"
+       "path"
        "path/filepath"
        "reflect"
+       "runtime"
+       "strings"
        "testing"
 
        "cmd/go/internal/base"
@@ -165,3 +170,54 @@ func pkgImportPath(pkgpath string) *load.Package {
                },
        }
 }
+
+// When installing packages, the installed package directory should
+// respect the group sticky bit and group name of the destination
+// directory.
+// See https://golang.org/issue/18878.
+func TestRespectGroupSticky(t *testing.T) {
+       if runtime.GOOS == "nacl" {
+               t.Skip("can't set group sticky bit with chmod on nacl")
+       }
+
+       var b Builder
+       b.Init()
+
+       // Check that `cp` is called instead of `mv` by looking at the output
+       // of `(*Builder).ShowCmd` afterwards as a sanity check.
+       cfg.BuildX = true
+       var cmdBuf bytes.Buffer
+       b.Print = func(a ...interface{}) (int, error) {
+               return cmdBuf.WriteString(fmt.Sprint(a...))
+       }
+
+       stickydir := path.Join(os.TempDir(), "GroupSticky")
+       if err := os.Mkdir(stickydir, 0755); err != nil {
+               t.Fatal(err)
+       }
+       defer os.RemoveAll(stickydir)
+
+       // Mkdir doesn't always correctly set the group sticky bit.
+       // Change stickydir's permissions to include group sticky bit.
+       if err := os.Chmod(stickydir, 0755|os.ModeSetgid); err != nil {
+               t.Fatal(err)
+       }
+
+       pkgfile, err := ioutil.TempFile(b.WorkDir, "")
+       if err != nil {
+               t.Fatalf("ioutil.TempFile(%q): %v", b.WorkDir, err)
+       }
+       defer os.Remove(pkgfile.Name())
+       defer pkgfile.Close()
+
+       stickyFile := filepath.Join(stickydir, "sticky")
+       if err := b.moveOrCopyFile(nil, stickyFile, pkgfile.Name(), 0666, true); err != nil {
+               t.Fatalf("moveOrCopyFile: %v", err)
+       }
+
+       got := strings.TrimSpace(cmdBuf.String())
+       want := b.fmtcmd("", "cp %s %s", pkgfile.Name(), stickyFile)
+       if got != want {
+               t.Fatalf("moveOrCopyFile(%q, %q): want %q, got %q", stickyFile, pkgfile.Name(), want, got)
+       }
+}